Small-scale gold mining threatens food
security in Southwest Ghana
(Al Jazeera, 2011)
Assignment 12: Final Report Interdisciplinary Project
Emma Daniëls Tamara Jonkman Lieke Hevink - 11003669 Addowa Scherpenisse - 10657754
Ayla Alting Siberg - 11025611 Lotte van Helden - 10574336
Table of contents
Abstract 3
1. Introduction 4
2. Theoretical Framework 5
3. Interdisciplinary approach 9
4. Selected methods and data 10
5. Analysis 12
6. Discussion 22
7. Conclusion 23
8. References 24
Appendix 1: Data Management Table 29
Appendix 2: Sampling method and locations 33
Abstract
In Southwestern Ghana, small-scale gold mining activities have experienced a big increase in the last 30 years. Change in law and increasing gold prices are examples of drivers of this increase. This has led to several problems for the environment, especially due to the use of mercury in the gold extraction process. Mercury spillage in the environment affects soil- and water quality and
eventually accumulates in the food system through crop uptake. This affects the yield of crops, the wealth of farmers and the health of miners and consumers. The aim of this paper is to get better insights into the negative effects of mercury accumulations in cassava leading to decreased food production and health risks for the population. In this interdisciplinary research, an integrated theoretical framework is developed following a DPSIR framework, which stands for: driving forces, pressures, states, impacts and responses. All environmental and societal indicators involved in the small-scale gold mining sector in Ghana are presented in this framework. The DPSIR framework is combined with an Integrated Human and Ecological Risk Assessment. The WHO safety guideline for consumption of mercury through cassava is 147 μg/kg (Castilhos et al., 2006). Four out of 34 cassava samples exceeded this WHO guideline. This indicates the serious threat of mercury pollution in Southwest Ghana. Even though not all samples showed concentration values above the guideline limit, mercury can accumulate in the food chain of the river ecosystem and after consuming fish or food crops, subsequently in human. Its effect on human health can therefore not be ignored. Mercury pollution could be one of the main threats to future food security in Southwest Ghana.
1.
Introduction
The United Nations Committee on World Food Security defines food security as “the condition in which all people at all times, have physical, social and economic access to safe, sufficient and nutritious food that meets their dietary needs and food preferences for a healthy life” (Pinstrup-Andersen, 2009). Food security has always been a point of focus for the world's nations, but will become more so due to a projected population growth to 10 billion people by 2050 (United Nations, 2017). Climate change, environmental issues and increasing food prices are further stressing food security (ibid).
Ghana has seen immense population growth, from 6 million inhabitants in 1957 (Adlakha, 1996) to 28 million in 2016, with predictions of 53 million inhabitants by 2050 (Pardee Center for
International Futures, 2016) and therefore needs an increase in food production in order to increase and maintain its food security. Small-scale gold mining is considered a stressor, possibly threatening Ghana’s food security (Garvin et al., 2009).
As of 2016 half of Ghana’s citizens are estimated to work in the agricultural sector, accounting for 21% of the country’s BNP (CIA Factbook, 2017). Ghana is the eighth largest gold producing country in the world (Sarpong, 2017) and ranks as the second gold producer of the African continent, behind South Africa (Obiri et al., 2016). Currently the country identifies two main categories within its gold mining sector: large-scale mining (>25 acres), small-scale mining (SSM) (<25 acres), within the SSM sector illicit mining is called galamsey (Hilson, 2010).
In the 2006 legislative framework for mining by the Ghanaian department of mineral wealth, it was written that the Ghanaian state is the rightful owner of all the minerals within the country's sea and land borders (Adjei et al., 2012). SSM concessions are only given to Ghanaian citizens which are allowed to enter into a joint venture with foreign investors to provide capital and critical knowledge in exchange for a cut of the profit (Gilbert & Albert, 2016). This liberalization of the mining sector has lead to boom of foreign investments in the gold sector in both the legal and illegal sector (Adjei et al., 2012).
There are several problems associated with SSM. First and foremost the decrease in arable land due to its conversion into lands for mining. Secondly, widespread destruction of flora (such as the unspoiled rain forests) and fauna by decreasing their food staples and habitat (Kessey et al., 2013). Creating bare lands for mining has led to the decrease of top and subsoils and thus land erosion. Another problem is the pollution of land and water caused by metals used by the miners such as mercury and arsenic (Nyame & Blocher, 2010). Mercury has very toxic properties that can be hazardous to miners health. As a result mental diseases, skin infections and eye complications are a frequent occurrence among small-scale miners (Kessey et al., 2013). Direct disposal of mercury into water bodies at mine sites has caused pollution of rivers and streams (Hilson, 2011). Mercury can accumulate in organisms where it can decrease biological activity and be carcinogenic (Kessey et al., 2013). It is estimated that improper disposal of mercury in SSM operations has been so rampant that all major water bodies in Ghana have been affected (Obiri et al., 2016), considerably decreasing clean drinking water reserves for the inhabitants.
Whilst deteriorating the environment, SSM has major socio-economic values such as the
contribution to earnings in foreign currency and employment. Hilson (2016), identified SSM as one of the most important livelihood activities, employing 1 million and indirectly supporting more than 4.5 million Ghanaians. According to Tschakert and Singha (2017), artisanal mining has seen
enormous growth since it was formalized in 1980. The growing SSM sector is partially attributed to growing youth unemployment, and the rise in global gold prices (Armh, 2013). Therefore the government is put in the difficult position with on the one hand the economic benefits and on the other hand the environmental drawbacks of SSM.
The main issue this paper will research is the possible threat of SSM to food security and public health in Southwest Ghana. SSM activities negatively affect waters, soils and food crop production, by pollution with chemicals such as mercury. The effects on food security, and thus the exact consequences for the local population are unclear. By conducting literature research as well as soil sample research an attempt will be made to answer the following research question: How and to what extent does small-scale gold mining threaten food security in the Southwestern region of Ghana?
2. Theoretical Framework
In this chapter a theoretical framework will be given from a social, economic, biological and geographical perspective, whereby it is separated in social sciences and natural sciences. Theories will be discussed about the causes of the problem. After evaluation of the disciplinary sections, an integrated theoretical framework will be introduced.
2.1. Social sciences
2.1.1. Push and pull theorySmallholder farmers often decide to diversify economic activities and income sources. Using the push and pull theory (Hilson, 2010), this study analyses why farmers decide to start engaging in nonfarm activities such as SSM (Appendix 1: DMT). Push factors are motives that are commonly associated with risk aversion and distress (Hilson, 2010). Pull factors are those factors in nonfarm activities that attract farmers to leave the farming business.
2.2. Natural sciences
2.2.1. Gold extraction processThe small-scale gold extraction process involves the crushing of gold-bearing rocks using machinery (Serfor-Armah et al., 2004). The crushed ore is then milled and the fine gravel obtained is mixed with water. The mixture flows down an inclined board which is covered with jute sack. Gold dust is trapped on the jute sack due to gravity concentration. The gold dust from the jute sack is
subsequently washed with water in a pan. Mercury is then added to the gold dust and hand-mixed to form a homogenous Hg-Au amalgam. Gold is obtained by roasting the amalgam in a coal pot in open charcoal fire (Serfor-Armah et al., 2004). All the mercury that is used, is released into the environment, since there is no system in place to recover the used mercury (Serfor-Armah et al., 2004).
2.2.2. Methylation
Methylation is an important theory for the spread of mercury in the environment (Armah et al., 2010) (Appendix 1: DMT). Methylation results into methylmercury and this is a more mobile and lethal product that can enter the food chain (Tschakert & Singha, 2007). Methylmercury can be formed from inorganic mercury in presence of microbes that live in aquatic systems such as lakes, rivers, sediments and soils (Voegborlo et al, 2006). Methylmercury is a volatile, colourless liquid which is insoluble in water (NPI, n.d.). Methylmercury is a bio accumulative environmental toxicant and therefore a potential threat for fish, food crops and subsequently human (Voegborlo et al., 2006).
2.2.3. Hydraulic conductivity
Hydraulic conductivity is another phenomena that contributes to the spread of mercury in the environment (Appendix 1: DMT). Hydraulic conductivity is the ease at which water can flow through porous spaces and fractures in soil and rock. Mercury that is spilled during the gold extraction process, may end up in rivers and sediments through rain-washing and thereby flow through the environment (Serfor-Armah et al., 2004). The more easily water can flow through rocks and soil, the more easily mercury in water may spread through the environment.
2.3. Integrated theoretical framework
2.3.1. DPSIR frameworkA driving forces-pressures-state-impacts-response (DPSIR) framework will be used to integrate all theories of the different disciplines. The DPSIR framework will give a clear overview of all
the developments that have occurred and their consequences for the environment and the society. In the figure below (Figure 1) an example of the framework can be seen.
The DPSIR framework consists of the following elements: Driving forces, Pressures, State, Impact and Responses (Gabrielsen & Bosch, 2003) (Appendix 1: DMT). Driving forces are the social, demographic and economic developments that occur in societies, one example hereof is population growth. This development leads to changes in production and consumption and thereby exert pressure on the environment. Pressures are developments in emissions, the use of resources and the use of land, CO2-emissions are an example. Due to these pressures, the state of the environment changes. In other words, the quantity and/or quality of the environment changes. This leads to impacts on e.g. human health, ecosystems and materials. Those impacts may elicit a societal response that feeds back on the driving forces, on the pressures or on the state or impacts directly (Gabrielsen & Bosch,
2003).
Figure 1: DPSIR framework
2.3.2. Integrated human and ecological Risk Assessment
When composing and using the DPSIR framework, an Integrated human and ecological Risk
Assessment is required to study the mercury pollution in cassava crops and the potentially harmful consequences for humans (Appendix 1: DMT). This study uses the assessment from Suter et al. (2006). The methods for this assessment are explained in chapter 4: Selected methods and data. There are two assumptions that were made when developing the assessment. First, the ingested dose of mercury is equal to the absorbed dose (United States Environmental Protection Agency,
safety guideline for consumption of mercury is 0.5μg/g (Castilhos et al., 2006) per day. In this report, mercury in cassava is studied and since an average diet consists of more than just cassava, the safety guideline needs to be adjusted according to calorie intake of cassava. This will be further explained in chapter 4: Selected method and data. This report has to show whether Ghanaians in southwest Ghana ingest more mercury through cassava than this safety guideline.
3.
Interdisciplinary approach
Food security is a complex subject which occurs on different levels with different actors. Besides, the three main elements of food security (food availability, food access and food utilization) are
continuously subject to change, and can therefore be seen as unpredictable, non-linear and
uncontrollable. This is enhanced by the different levels and the wide range of actors influencing the issue. In this report, the food security pillar ‘food utilization’ is analysed. This encompasses the safety, quality and nutritional value of food (Pinstrup-Anderson, 2009).
To equally analyse different aspects and processes of this complex issue, an interdisciplinary
approach is required. For this report an integrated framework in the form of a DPSIR framework will be used to expose social, economic, biological and geographical inputs. The DPSIR framework consists of the following elements: Driving forces, Pressures, State, Impact and Responses
(Gabrielsen & Bosch, 2003). The first sub-question is part of the ‘Driving forces’ and will answer how the SSM industry has been able to expand, and what the consequences are for local population. Contextual and historical socio-political and socio-economic aspects will be described here. The second sub-question is part of the ‘Pressures’ and ‘State’ and will answer what the effects of SSM are on water quality in the Southwestern region of Ghana. This encompasses aspects from the earth science perspective. The third and final sub-question is part of the ‘State’ and ‘Impact’ will answer how SSM affects soils and crop production, and what the consequences are for local food
production. For the ‘State’ and ‘Impact’ sections, an Integrated human and ecological Risk
Assessment is required to study the mercury pollution in cassava crops and the potentially harmful consequences for humans. The knowledge from previous sub-questions will be combined with biological aspects, after which the consequences on the population will be researched, using a human geography approach. This way it will be possible to cover the issue and provide more insight. In the last section of the DPSIR framework, ‘Responses’, the societal responses that feed back into the driving forces, pressures, or on the state or impacts will be described.
4.
Selected methods and data
As was stated before, this paper will consist of a DPSIR framework to be able to create an interdisciplinary approach of the problem. Within the DPSIR framework an Integrated Risk Assessment will be implemented, which will be described in the following paragraphs. The Integrated Risk Assessment will make use of a set safety guideline of maximum mercury intake through cassava. This paper uses cassava as base to measure food security is because it is one of the most important sources of calories in Ghana (FAO, 2001). As a matter of fact, cassava roots account for approximately 662 calories per person per day (ibid.). This amount of average daily calorie intake and the WHO safety guideline of maximum mercury intake were used to set a new guideline for maximum intake of mercury through cassava consumption. To be able to calculate this new guideline, the assumption was made that the average calorie intake per day per person is 2250 calories (ibid.). The WHO guideline is 0.5μg/g per day for a whole diet (Castilhos et al., 2006) and when adjusting this guideline to the guideline for cassava, the following calculation was made. When dividing 2250 by 662, it resulted in a factor of 3.4 and when dividing the WHO guideline through this factor, a new guideline was settled at 0.5/3.4 = 0.147 μg/g = 147 μg/kg mercury. This is why the used safety guideline for cassava intake was set at 147 μg/kg.
When making the DPSIR-framework, both primary and secondary data will be used to retrieve information. The type of data that is used depends on the discipline and DPSIR section. When describing the ‘Drivers’ section to find out how SSM has been able to expand and what the consequences are for the population, mainly secondary data will be assembled through literature study and it has to be viewed from a social and economic perspective. Secondary data will also be used when constructing the ‘Pressures’ and ‘Responses’. On the other hand, to be able to analyze the matter of exposure and the effects soils, crop production and health, not only secondary, but also primary data will be necessary. To be able to present accurate data, soil samples have been taken at 4 different farming sites and they were examined in the laboratory after. These steps have been taken earlier this year and mercury concentrations from the soil samples have been
determined in the Science Park lab. Further explanation about the sampling methods can be found in Appendix 2. The concentration results of these samples will be used when compiling the sections ‘State’ and ‘Impact’ sections.
When estimating ‘State’ and ‘Impact’ there will also be use of a different framework to be able to get a clear view on exposure and dose-response. This is why the Integrated Risk Assessment of Suter (2005) will be used, which was based on the framework for health and ecological risk of WHO (2001). This assessment consists of 4 steps which are pictured in Figure 2. The first step in this assessment is the formulation of the problem (Suter, 2005), which will be covered by the ‘Drivers’ and ‘Pressures’ sections. After that, there will be an exposure assessment (ibid.), which will be worked out at the ‘State’ section. At this section the mercury concentrations of the derived soil samples1 will be compared to mercury concentrations of soil and cassava samples from the research of Adjorlolo-Gasokpoh, Golow & Kambo-Dorsa (2012). When analyzing these samples, mercury concentrations of cassava growing on the four researched farming sites will be estimated, since there were no cassava samples derived from these sites to calculate these concentrations from. This way, the degree of mercury exposure in the South-West region of Ghana can be estimated. After this, the next step of the Integrated Risk Assessment will be a dose-response assessment, which will be described by the ‘Impact’ section. In this part, all samples will be compared to the set safety guideline of maximum mercury intake through cassava. After this comparison, the consequences on
public health can be estimated in the risk characterization. At last all of the derived information has to be combined to be able to answer the main question about the effect of small-scale gold mining on food security in Ghana. The results can be examined and depending on the outcome, potential future steps to reduce risk can be discussed in the response section of the DPSIR framework.
Figure 2: Framework of Integrated Risk Assessment for Health and Ecological Risks (Suter, 2005).
5.
Analysis
5.1. Drivers
5.1.1. GeologyFigure 3: Geologic map of southwest Ghana showing Birimian and Tarkwaian rocks and the five volcanic belts (Eisenlohr & Hirdes, 1992).
In the Proterozoic Birmian and Tarkwaian supracrustal rocks of West Africa, a major gold province exists (Dzigbodi-Adjimah, 1993). The majority of the gold comes from the primary lode occurrences of the Birmian rocks of Ghana (ibid.). Gold is in five parallel, evenly spaced, northeast-trending volcanic belts separated by basins containing pyroclastic material (ibid.) (Fig. 2). The Ashanti volcanic “greenstone” belt is the most prominent one, which hosts the Ashanti Goldfields Corporation mines at Obuasi, the Billiton Bogoso Gold mine at Bogoso, and the State Gold Mining Corporation mines at Prestea, Bibiani and Konongo (ibid.).
5.1.2. Demand for employment
A lot of Ghanaian farmers have decided to engage in nonfarm activities such as SSM. The push and pull theory explains this development. The major push factors to pursue different or secondary activities seem to be the increasing population growth and decreasing farm productivity (Hilson, 2010; Wilson, 2015). Others found that people are pushed towards mining activities due to lack of other employment opportunities and loss of previous jobs (Tschakert, 2009). The factors that pull them to SSM are mostly associated with economic opportunities, such as a higher return on labour (Hilson, 2010; Wilson, 2015). This notion of SSM being an opportunity to “get rich quick” is popular (Hilson, 2012). Some locals also mention the opportunity to accumulate capital to start their own business (Tschakert, 2009). This is especially the case for women, who make up 15% of legal SSM practices and approximately 50% of illegal SSM activities (Wilson, 2015). However, the push factors seem to outweigh the pull factors, “in other words, most of these people are “pushed” into SSM out of necessity, rather than being “pulled” by a “get rich quick” prospect” (Wilson, 2015, p.8139). Thus, the majority of workers in gold mining activities are largely driven by poverty (Tschakert, 2009; Banchirigah & Hilson, 2010).
Nevertheless, mining can create opportunities for those who can no longer be supported solely by farming (Hilson & Garforth, 2012). Moreover, members from farm households move in and out of farming as their economic situation changes, possibly due to seasonal differences in farm
productivity (Hilson, 2012). Investment in mining often comes from agricultural earnings. This also works the other way around as mining earnings can be invested in necessary farming supplies. Locals often remain reliant on agriculture to meet their needs, not solely for export reasons, but mostly for food security reasons. “The role of agriculture has by no means been diminished; it has rather been redefined” (Hilson, 2012).
5.1.3. Employment demand and rising gold prices
(Illicit) Artisanal mining has major socio-economic values such as the contribution to earnings in foreign currency and employment. Hilson (2016), identifies SSM as one of the most important livelihood activities, employing 1 million and indirectly supporting more than 4.5 million ghanaians. According to Tschakert and Singha (2017), artisanal mining has seen enormous growth since it was formalized in 1980. This is in large part due to the growing youth unemployment and economic hardships in mining communities. It was estimated that the illegal artisanal sector employed 500,000 people in 2009 (Tschakert, 2009) and 1 million people in 2016 (Hilson, 2016). In the past five years the closure of large-scale mines such as the Obuasi gold mine which employed over 5000, has led these laid off miners to seek out jobs in galamsey.
Part of the surge in galamsey can also be attributed to the rise in global gold prices (Armah et al., 2013). Between 2005 and 2010 the price of gold increased from $445 per ounce to $1224 per ounce (Nyame & Grant, 2011). This increase has made gold mining more alluring than ever before.
5.1.4. Ban on Ghanaian diamond exports
The production of diamonds has always contributed to the country’s GDP, in 2006 it was ranked the fourth natural resource export product. However, since 1972 when Ghana`s diamond production reached its peak of 2.5 million carats, the diamond output has been declining (Nyame & Grant,2011),
surfaced that diamonds from Ivory Coast where sold in Ghana. Due to the civil war in Ivory Coast the UN had banned the export of diamonds from Ivory Coast in order to prevent the regime funding its war with the proceeds. Around the same time the Kimberley Process Certification Scheme (KPCS) was implemented (Afriyie, Ganle & Adomako, 2016). This scheme emphasises safe diamond mining with the least amount of environmental effects. From 2006 onward all diamonds had to comply with with the KPCS to be eligible for export. This led to a large increase in the production cost of artisanal diamond mining. During this time the price of gold only increased, this caused many diamond miners to adapt to SSM (Nyame & Grant, 2011).
5.1.5. A change in the law and the liberalization of the mining sector
Ghana’s SSM sector is over 2000 years old. During and after the colonial era, legislature was put in place aiming to prevent local inhabitants and local operators from practicing SSM whilst
simultaneously boosting large-scale mining (Aryee et al., 2003). The SSM sector was considered informal until 1980 when the government drafted its first legislature on artisanal mining (Hilson, 2001).
In 2006 the government of Ghana established a new legislative framework for mining. This
contained legislature identifying the Ghanaian state as the rightful owner of all the minerals within the country's sea and land borders. The same framework describes artisanal mining as mining activities on an area that contains less than 25 acres and large scale mining as mining activities spreading more than 25 acres (Adjei et al., 2012).
It states that Ghanaian citizens can apply for artisanal mining concessions. To boost investments and mining knowledge, these citizens are allowed to join into joint ventures with foreign investors. Commonly these investors in turn, get the first rights to buy all gold that is produced at this venture (Gilbert & Albert, 2016). By liberalizing the gold mining sector, the government has stimulated foreign investments in both the legal and illegal sector (Adjei, 2012).
Furthermore, the legislation states “a person shall be presumed to be lawfully in possession of gold until the contrary is proven” (Hilson, 2013 p4). As gold is untraceable once it exploited from the ground illegal gold miners have the same legal access to world gold markets as registered gold miners do (Teschner, 2012).
5.1.6. Difficulties in obtaining small scale mining concessions lead to illegal mining
Even though it is possible for Ghanaian citizens to apply for mining concessions at their local
illegally so without a permit (Sarpong, 2017).
A study by Sarpong et al. (2017), found that most miners consider the process of registering complex and the acquirement of land to be costly. Part of the difficulty in obtaining a mining licence is due to the lack of untitled land to exploit for mining. The untitled lands that are available often lack
geological records without which it is nearly impossible to attract foreign investments (McQuilken & Gavin Hilson, 2016). This encourages poverty driven miners to continue operating illegally.
5.1.7. The influx of Chinese nationals
A recent boost in galamsey is attributed to the influx of 50,000 plus Chinese nationals in the Ghanaian mining sector (Hilson et al., 2014). With them they have brought expensive technology and equipment, which increased the profitability and productivity in the illegal mining sector. With this advanced equipment such as bulldozers, payloaders etc. they have been primarily been mining shallow rock and alluvial deposits which has inundated large areas of land and dredged vast sections of rivers (ibid). The Chinese have also repeatedly been accused of the violation of human rights at their mining sites. These accusations such as illegal seizing of farmlands, rerouting important rivers and threatening locals with rivals in combination with the large amount of pollution and erosion associated with Chinese mining practices have led to the growing civilian cals for the government to prosecute these Chinese nationals. In response the government has founded a national taskforce in 2013 with the aim of stopping Chinese gold miners. However it is rumored that widespread
corruption of government officials continues to make it possible for Chinese goldminers to enter the country without the necessary paperwork (Teschner, 2013).
Whilst the task force has had some successes such as the deportation of 168 Chinese nationals in june 2013, it has been found that the local gold miners continue using the equipment brought in by the Chinese. Chinese investments in Ghana that reached 5.4 billion dollars in 2015 as well as being one of the main trade partners of ghana arize questions with regard to the leniency that ghanaian officials show to chinese miners rounded up by the national taskforce (Hilson, Hilson & Darko, 2014). 5.1.8. Funding and law enforcement
Many accounts have surfaced of Ghanaian politicians themselves investing and backing galamsey (Hirons, 2013). As a result many Ghanaians doubt the legitimacy of the Ministerial Task Force that was established to prosecute illegal miners and seize their activity.
As illicit miners have limited access to formal credit and federal investments, local investors have been filling this gap. This has further complicated prosecution of local miners as many locals and local government employees are invested and benefiting from galamsey (Hilson, Hilson & Darko, 2014).
Improved road and telecommunication networks has aided access to formerly unreachable backwoods. The improved infrastructure has allowed small-scale miners to move themselves and equipment with increased ease and speed. Improved telephone and internet networks are used by miners to tip each other off during law enforcements rades. Hence, it has become easier for small-scale miners to evade prosecution (Hirons, 2013).
5.2. Pressures
5.2.1. Evaporation of mercury
Mercury is a toxic heavy metal with a high vapour pressure, which causes it to vaporize easily. When roasting the amalgam to obtain gold, mercury is released into the atmosphere (Tschakert & Singha, 2007). Small-scale gold miners usually do not have suitable retorting facilities, therefore all mercury vaporizes into the atmosphere (Golow & Adzei, 2002). Hereafter, the mercury is converted to soluble forms and deposited by rain onto soils and water, which causes it to be distributed
throughout the soils and water systems of Ghana (WHO, 1990). Mercury vapour has an atmospheric residence time of between 0.4 and 3 years, whereas soluble forms have residence times of a few weeks. Transport in soil and water is thus limited and it is probably that deposition will occur within short distance (WHO, 1990).
5.2.2. Spillage of mercury
In the gold extraction process, the anthropogenically introduced mercury is lost to soils, tailings, stream sediments and water close to the processing sites (Serfor-Armah et al., 2004). Spillage of mercury into the environment may take place when adding and mixing the mercury to form amalgam (Tschakert & Singha, 2007). Besides, dumping of mercury containing ashes from coal pots that were used to roast the amalgam also pollute the environment (Serfor-Armah et al., 2004). Inorganic mercury released into the aquatic environment undergoes biological methylation into methylmercury (Me-Hg), this is the most toxic form of mercury (ibid.) Besides, methylmercury is a more mobile product that can enter the food chain (Tschakert & Singha, 2007).
Through polluted precipitation, spillage of mercury and tailings, mercury will end up in rivers and sediments (Serfor-Armah et al., 2004). Hydraulic conductivity indicates how fast water, and thus mercury, can spread through the environment. In the Southwestern region of Ghana, the hydraulic conductivity is in the range of 4.5 m/d to over 70 m/d (meters per day) (Yidana et al., 2013).
5.3. State
5.3.1. Mercury pollution in water
Communities in Ghana get their domestic water supply from boreholes, rivers, streams and
groundwater. The central and western regions of Ghana rely on groundwater as their main source of domestic water supply. This is a result of the widespread contamination of surface water sources through mining activities (Nartey et al., 2011; Tay & Hayford, 2016).
The World Health Organization (WHO) drinking water guideline limit for total (inorganic and organic) mercury is 0.001 mg/L (WHO, 2011). Serfor-Armah et al. (2004) measured total mercury
concentrations in water in Prestea and its environs. Prestea is a gold mining town, known for its history of SSM using amalgamation. The range of total mercury concentration was between 0.50-19.82 mg/L. The concentration levels of total mercury in water from all the sampling sites were in excess of WHO tolerable limit of 0.001 mg/L. Obiri et al. (2016) collected 200 water samples from four streams, five rivers and one borehole in the Tarkwa Nsuaem Municipality. The Tarkwa Nsuaem Municipality district produces an estimated 35% of Ghana’s gold output. All 200 water samples analysed for Hg exceeded the WHO guideline value of 0.001 mg/L.
5.3.2. Mercury pollution in sediments and soils
Sediments of rivers function as sinks for released Hg in the environment, while those same rivers also act as a source for domestic water supply (Adjei-Kyereme et al., 2015). The United States Environmental Protection Agency (US EPA) guideline value for mercury in sediments is 0.2 mg/kg. Donkor et al. (2006) studied sediments from the Pra River Basin during the dry season and the rainy season. During the dry season, none of the sampling sites exceeded the US EPA guideline of 0.2 mg/kg. However, during the rainy season, three out of the 21 sampling sites exceeded the US EPA guideline of Hg in sediments. Serfor-Armah et al. (2004) measured total mercury concentrations in sediments in Prestea and its environs. The range of total mercury concentration for the sediments was 1.20 - 84.30 mg/kg. All samples were above the US EPA guideline and therefore might be a threat for aquatic life and human.
As regards to mercury concentration levels in soils, a natural soil intervention value of 0.098 mg/kg is accepted worldwide (Fergusson, 1990). From the study of Bempah & Ewusi (2016) to mercury levels in agricultural soils, appeared that all farms within the studied areas, Hg concentrations higher than 0.098 mg/kg occurred. This study was conducted in the Obuasi mine area. Donkor et al. (2006) also studied soil samples. During the dry season, one of the sampling sites exceeded the natural
intervention value of 0.098 mg/kg. During the rainy season, ten of the sampling points exceeded this value.
5.3.3. Exposure Assessment Mercury pollution in cassava
The amount of mercury that a plant is able to take up and their way of absorption differs per species (Alcantara et al., 2017). Despite the characteristic of cassava to be highly tolerant to mercury, high concentrations still have negative on physiological and biochemical processes, which reduces the growth rate and biomass average (ibid.). This could have a small negative effect on local yield. Another characteristic of cassava is the fact that it stores most of the mercury in its biomass instead
could make it dangerous to consume cassava in large amounts, which makes it important to know the amount of mercury pollution in cassava (ibid).
One study that has already examined the mercury concentration in cassava was the research of Adjorlolo-Gasokpoh, Golow & Kambo-Dorsa (2012). They took multiple soil and cassava samples from different sites that varied in distance from small scale gold mines. The research stated that in some areas, the matter of cassava pollution was already exceeding concentration limits (ibid).When analyzing the soil and cassava samples of the study of Adjorlolo-Gasokpoh, Golow & Kambo-Dorsa (2012) the mercury concentrations from the Ashanti region samples could be estimated (Appendix 4). The findings (figure 5) show that mercury concentrations of cassava in the region of Bogoso lay between 66.60 and 195.47 μg/kg, while the concentrations in the Ashanti regions were all
approximately 24 μg/kg.
Relation between mercury pollution and distance to gold mines
Another discovery in the research of Adjorlolo-Gasokpoh, Golow & Kambo-Dorsa (2012) was a linear connection between distance from a gold mine and mercury concentrations in soil and cassava plants. Locations that were further away had larger amounts of mercury in the soil and plants than the farms that were closer to the mines (ibid). They explained this by stating that precipitation containing vaporized mercury would fall further away from the mines. However, they did not measure samples from areas further than 20 km distance, so it is not certain is this linear relation would continue from this point. Still, it could be concluded that farmers and locals which live
approximately 20 km from the mines could experience more impact, because it could affect the yield amount and the nutritional values. However, this could also be discussable, since the cassava is also sold to other areas throughout the country, which could mean that the threat could be evenly shared across the whole county.
5.4. Impact
5.4.1. Dose-response assessment and health risk characterization
According to the World Health Organization (WHO), the safety guideline for consumption of mercury is levelled at 0.5 μg/g and 0.25 μg/g for pregnant women (Castilhos et al., 2006; Tchounwou et al., 2003; WHO, 1991). After converting this concentration to maximum mercury intake from cassava consumption only, the safety guideline was set at 147 μg/kg. When comparing this value to the concentrations of the Bogoso and Ashanti samples, the outcomes vary (Figure 4). The Ashanti samples and most of the Bogoso samples do not exceed the limit, but some of the Bogoso samples taken from larger distances of the gold mines do. This means that in most cases there is no great risk, but that there is a possibility that the limit would be exceeded.
When this is the case, there is a threat that clinical issues will arise which can affect human health (Castilhos et al., 2006). It is known that mercury exposure through food can cause many
complications in the functioning of the human body (WHO, 1991). Examples of these effects are kidney problems, “Pink Disease” in children, problems with the menstruation cycle, effects on the central nervous system like erethism and some researchers even claim that mercury poisoning has already caused some health hazards among populations (WHO, 1991; Tchnounwou et al., 2003)). Another public health concern is the impact of mercury on foetuses and babies (Dorea, 2004). The mercury will be passed onto foetuses through blood transportation and when new mothers obtain too much mercury in their digestive system, the mercury will be passed onto babies through breast feeding (ibid.). This can contribute to early child mortality among populations in Ghana.
Even though most of the sample concentrations do not exceed the set guideline, there is still a chance that people consume cassava that contains too much mercury, which could cause serious health issues as stated above. When looking at the samples from Bogoso and Ashanti combined, there are 4 out of 34 situations in which the limit is exceeded, which is why current mercury pollution could still be characterized as high risk.
Figure 4: Mercury concentrations (μg/kg) in soil surface and cassava, compared with safety guideline for mercury intake through cassava.
5.5. Responses
Due to the impact of SSM, there will be an incentive to respond to the previously addressed drivers, its following pressures, affected state and subsequent impact. All of the following responses can also be recognized as recommendations for the Ghanaian government or NGOs. To whom it is addressed will be clarified with each response.
5.5.1 Responses to drivers Creating sustainable livelihoods
One of the main factors that drives a large part of the population to engage in SSM is the demand for employment. If there would be a wider range of job opportunities, it is likely that the amount of small-scale gold miners would decrease.
Moreover, it is important to create more sustainable livelihoods, not only environmentally but also labour-wise. This means that vulnerability must be reduced by helping people and their livelihoods be more resilient to external disturbances (Carney, 1999). Workers need to be able to depend on their job long-term and have a steady income. This would hopefully prevent them from turning back to the highly unsustainable gold mining sector.
Existing projects to create alternative livelihoods have, however, not been very successful or effective among illegal SSM communities (Hilson & Banchirigah, 2009). This is therefore a recommendation to the Ghanaian government to create new initiatives to create sustainable livelihoods.
5.5.2. Responses to pressures Applying better equipment and methods
If the amount of small-scale miners would decrease as a result of livelihood diversification, there would hopefully be a larger proportion of large-scale miners. This part of the industry utilizes different techniques and equipment. They do not, for instance, use mercury in large-scale mining (Chuhan-Pole et al., 2015). This means that mercury spillage and evaporation, pressures of SSM, is not seen in large-scale mining.
However, it is unlikely for the large proportion of small-scale miners to decrease rapidly, which means that unsuitable techniques will still be applied largely. To tackle this issue and to decrease the negative effects of applied techniques, the Ghanaian government could start subsidizing adequate equipment. Subsidization could however attract even more people to the industry, which would create adverse effects. That is why the miners would have to be qualified based on strict
requirements such as mining experience and knowledge.
To expand their knowledge and to ensure that all small-scale miners consistently use the correct methods, NGOs could organize programs in which miners learn how to properly apply techniques and why, environmentally speaking, this is so important.
5.5.3. Responses to state
Monitoring of mercury concentrations in soil and water
One response that is of great importance is the environmental monitoring of mercury
concentrations in mining regions. As of yet, this has not been carried out to a great extent. The government can play an important role in this by setting up directives for monitoring. If mercury concentrations in water and soil would be monitored on a large scale and long term, it can create
more awareness and opportunities for organisations, scientists and other actors. They could, for instance, educate mining communities about the environmental effects of SSM.
Policy changes
Increased awareness of mercury pollution in water and soil in mining regions, could result in policy interventions. If communities and the Ghanaian government realize the extent of the issue and how it might increases over time, they may realize it is important to implement change.
5.5.4. Responses to impact Routine medical check-ups
Once established what the consequences are for food production and food quality, local
communities will likely feel very uneasy about possible negative health effects. A recommendation for NGOs would be to undertake free and routine medical check-ups amongst mining communities. They might feel less scared and uneasy if the state of their health is monitored routinely. Moreover, it will likely reduce uncertainty amongst mining communities.
5.6. DPSIR framework
From the conducted analysis, a DPSIR framework for Ghana’s small-scale gold mining case is derived (Figure 5).
6.
Discussion
The resulted DPSIR framework does not consist of all elements that play a part in the small-scale gold mining problem, but when conducting this research an attempt has been made to include the most important factors that play a role in the small-scale gold mining problem. Based on literature studies, the most frequently mentioned factors have been chosen.
Furthermore, for this research a guideline was used, but since mercury can accumulate in food crops, fish and human bodies, the question is how safe this guideline is. In addition, the DPSIR framework and the Integrated human and ecological Risk Assessment show worrying results for Southwestern Ghana. However, the amount of samples used for this study was too low to be able to draw conclusions that apply for that entire region. Further research is needed on the accumulation of mercury to see whether guidelines need to be changed and there also have to be more papers regarding mercury contamination in soil and cassava crops in different regions to be able to draw conclusions.
Moreover, in answering our research question only one pillar of food security, the food utilization pillar, has been considered. This encompasses the safety, quality and nutritional value of food. The other two pillars, food availability and food access, were not taken into account. Thus it could be argued that this research has given an incomplete picture regarding the effect on food security. Besides, the responses and recommendations for the Ghanaian government, NGOs and local
communities may not be easily implemented as portrayed in this report. It requires further research, awareness of the issue and cooperation of a wide range of actors to assess and implement change. This is part of the reason why there was no explicit reference to any particular policy change in paragraph 5.5.3.
7.
Conclusion
How and to what extent does SSM threaten food security in the Southwestern region of Ghana? It starts by explaining the origin of the problem. The growth of SSM in the past 30 years can be attributed to a multitude of drivers. First and foremost the decentralization and liberalization of the mining sector in Ghana that has been in motion ever since the colonial independence has made the industry increasingly unmanageable. Secondly rising gold prices in combination with increased productivity due to the mechanisation of SSM has created many job openings in SSM. The large amount of positions that galamsey creates for unemployed youths and laid off large-scale miners puts the government in a predicament as it has little alternative jobs to offer and the socio-economic benefits of galamsey for the country on short term are large.
These developments have led to a fast growth in the SSM industry and thereby exert pressure on the environment. Spillage of mercury, evaporation of mercury and gold mine waste containing mercury, are pressures for the environment. Mercury pollution occurs in surface waters, groundwater, sediments, soils and in cassava crops. This has a small impact on the yield of cassava and thereby the wealth of farmers, but most of all has impact on health, since the mercury concentrations in cassava can exceed the set safety guideline of 147 μg/kg. Four out of 34 cassava samples exceeded this WHO guideline. This indicates the serious threat of mercury pollution in Southwest Ghana. Even though not all samples showed concentration values above the guideline limit, mercury can accumulate in the food chain of the river ecosystem and after consuming fish or food crops, subsequently in human. Its effect on human health can therefore not be ignored. Mercury pollution could be one of the main threats to future food security in Southwest Ghana.
Subsequently, there is a range of possible responses from both the Ghanaian government and NGOs, which can be perceived as recommendations for these actors. The responses include creation of sustainable livelihoods, application of better mining equipment and methods, environmental monitoring, policy changes and routine medical check-ups among mining communities.
Due to the large impact that high mercury concentrations in food can have and the small number of samples taken as evidence to support this paper, it is strongly advised that NGOs or the Ghanaian government conduct a large scale investigation where many soil samples are taken. It is also important that Ghana's staple crops are tested to see to which amount mercury accumulates in these consumable plants to gain a more accurate insight into the amount of mercury that the average Ghanaian might consume by food intake and the associated health risks that accompany these intakes. Lastly it is advised the government and NGOs use special monitoring using satellite imagery and drones as a low cost method to more effectively locate illegal mining operations.
As far as solving the problem, the most important thing is to address the problem at the source. This means stricter rules regarding the use of mercury in SSM, or perhaps forbidding it entirely to use. Education about the environmental and health problems might also steer the Ghanaian citizens into more eco-friendly directions.
8.
References
Adjei S., Oladejo N.K. & Adetunde, I.A. (2012). The Impact and Effect of Illegal Mining (galamsey) towards the Socio-economic Development of Mining Communities: A case study of Kenyasi in the Brong Ahafo Region. International Journal of Modern Social Sciences, 1(1), 38-55.
Adjei-Kyereme, Y., Donkor, A. K., Golow, A. A., Yeboah, P. O., & Pwamang, J. (2015). Mercury concentrations in water and sediments in rivers impacted by artisanal gold mining in the Asutifi district, Ghana. Res. J. Chem. Environ. Sci, 3, 40-48.
Adjorlolo-Gasokpoh, A., Golow, A. & Kambo-Dorsa, J. (2012). Mercury in the Surface Soil and
Cassava, Manihot esculenta (Flesh, Leaves and Peel) Near Goldmines at Bogoso and Prestea, Ghana. Bulletin of Environmental Contamination and Toxicology, 89(6), 1106-1110.
Adlakha, A. (1996). Population trends: Ghana. US Department of Commerce, Economics and Statistics Administration, Bureau of the Census.
Afriyie, K., Ganle, J.K., & Adomako, J.A.A. (2016). The good in evil: a discourse analysis of the galamsey industry in Ghana. Oxford Development Studies, 44(4), 493-508.
Alcantara, H.J.P., Doronila, A.I. & Kolev, S.D. (2017). Phytoextraction potential of Manihot esculenta Crantz. (cassava) grown in mercury- and gold-containing biosolids and mine tailings. Minerals Engineering, 114, 57-63.
Al Jazeera (2011). Gold: Ghana's blessing or curse?. Received on 18-12-2017 from
http://www.aljazeera.com/programmes/africainvestigates/2011/11/201111307453977885.html Armah, F.A., Obiri, S., Yawson, D.O., Onumah, E.E., Yengoh, G.T., Afrifa, E.K., & Odoi, J.O. (2010). Anthropogenic sources and environmentally relevant concentrations of heavy metals in surface water of a mining district in Ghana: a multivariate statistical approach. Journal of Environmental Science and Health Part A, 45(13), 1804-1813.
Aryee B.N.A., Ntibery B.K., Atorkui E. (2003). Trends in the small-scale mining of precious minerals in Ghana: a perspective on its environmental impact. Journal of Cleaner Production 11 (2003) 131–140. Banchirigah, S.M. & Hilson, G. (2010). De-agrarianization, re-agragrianization and local economic development: Re-orienting livelihoods in African artisanal mining communities. Policy Sciences, 43(2), 157-180.
Bempah, C.K. & Ewusi, A. (2016). Heavy metals contamination and human health risk assessment around Obuasi gold mine in Ghana. Environmental monitoring and assessment, 188(5), 261.
Carney, D. (1999). Approaches to Sustainable Livelihoods for the Rural Poor. Overseas Development Institute. Retrieved from https://www.odi.org/sites/odi.org.uk/files/odi-assets/publications-opinion-files/3093.pdf on 30-11-2017.
Castilhos, Z.C., Rodrigues-Filho, S., Rodrigues, A.P.C., Villas-Bôas, R.C., Siegel, S., Veiga, M.M. & Beinhoff, C. (2006). Mercury contamination in fish from gold mining areas in Indonesia and human health risk assessment. Science of the Total Environment, 368(1), 320-325.
CIA Factbook (2017). Economy. Received on 02-10-2017 from
https://www.cia.gov/library/publications/the-world-factbook/geos/gh.html
Chuhan-Pole, P., Dabalen, A., Kotsadam, A., Sanoh, A. & Tolonen, A. (2015). The Local Socioeconomic Effects of Gold Mining: Evidence from Ghana. World Bank Policy Research Working Paper, 7250. Donkor, A.K., Bonzongo, J.C., Nartey, V.K. & Adotey, D.K. (2006). Mercury in different environmental compartments of the Pra River Basin, Ghana. Science of the Total Environment, 368(1), 164-176. Dorea, J.G. (2004). Mercury and lead during breast-feeding. British Journal of Nutrition, 92(1), 21-40. Dzigbodi-Adjimah, K. (1993). Geology and geochemical patterns of the Birimian gold deposits, Ghana, West Africa. Journal of geochemical exploration, 47(1-3), 305-320.
Eisenlohr, B.N. & Hirdes, W. (1992). The structural development of the early Proterozoic Birimian and Tarkwaian rocks of southwest Ghana, West Africa. Journal of African Earth Sciences (and the Middle East), 14(3), 313-325.
FAO. (2001). The cassava transformation in Africa. Received on 20-12-2017 from
http://www.fao.org/docrep/009/a0154e/A0154E03.HTM
Fergusson, J.E. (1990). Heavy elements: chemistry, environmental impact and health effects. Pergamon.
Forti, E., Salovaara, S., Cetin, Y., Bulgheroni, A., Tessadri, R., Jennings, P., ... & Prieto, P. (2011). In vitro evaluation of the toxicity induced by nickel soluble and particulate forms in human airway epithelial cells. Toxicology in Vitro, 25(2), 454-461.
Gabrielsen, P. & Bosch, P. (2003). Environmental indicators: typology and use in reporting. EEA, Copenhagen.
Garvin, T., McGee, T.K., Smoyer-Tomic, K.E., & Aubynn, E.A. (2009). Community–company relations in gold mining in Ghana. Journal of environmental management, 90(1), 571-586.
Gilbert, D., & Albert, O.B. (2016). Illegal Small-Scale Gold Mining in Ghana: A Threat to Food Security. Journal of Food Security, 4(5), 112-119.
Golow, A.A., Adzei, E.A. (2002). Mercury in Surface Soil and Cassava Crop Near an Alluvial Gold Mine at Dunkwa-on-Offin, Ghana. Bulletin of Environmental Contamination and Toxicology, 69, 228–235. Hilson, G. & Banchirigah, S.M. (2009). Are Alternative Livelihood Projects Alleviating Poverty in Mining Communities? Experiences from Ghana. The Journal of Development Studies, 45(2), 172-196.
Hilson, G. (2010). ‘Once a miner, always a miner’: Poverty and livelihood diversification in Akwaita, Ghana. Journal of Rural Studies, 26(3), 296-307.
Hilson, G. & Garforth, C. (2012). ‘Everyone Now is Concentrating on the Mining’: Drivers and Implications of Rural Economic Transition in the Eastern Region of Ghana. The Journal of Development Studies, 49(3), 348-364.
Hilson, G., Hilson, A. & Adu-Darko, E. (2014). Chinese participation in Ghana's informal gold mining economy: Drivers, implications and clarifications. Journal of Rural Studies, 34, 292-303.
Hirons, M. (2013)
Mining in Ghana's forests: cross-sectoral linkages and the prospects for REDD. International Development Planning Review, 35 (3).
Kessey, K.D. & Arko, B. (2013). Small Scale Gold Mining and Environmental Degradation in Ghana: Issues of Mining Policy Implementation and Challenges. Journal of Social Sciences, 5(1), 12-30. McQuilken, J. & Hilson, G. (2016) Artisanal and small-scale gold mining in Ghana. Evidence to inform an ‘action dialogue’. Received on 30-12-2017 from http://pubs.iied.org/16618IIED/
Nartey, V.K., Klake, R.K., Hayford, E.K., Doamekpor, L.K. & Appoh, R.K. (2011). Assessment of mercury pollution in rivers and streams around artisanal gold mining areas of the Birim North District of Ghana. Journal of Environmental Protection, 2(9), 1227.
Nyame, F.K. & Blocher, J. (2010). Influence of land tenure practices on artisanal mining activity in Ghana. Resources Policy, 35(1), 47-53.
Nyame F.K. & Grant A. (2012). From carats to karats: explaining the shift from diamond to gold mining by artisanal miners in Ghana.
Journal of Cleaner Production: Volumes 29–30, July 2012, Pages 163-172
NPI - National Pollutant Inventory (n.d.). Mercury & compounds, Chemical properties. Received on 23-11-2017 from http://www.npi.gov.au/resource/mercury-compounds
Obiri, S., Mattah, P.A., Mattah, M.M., Armah, F.A., Osae, S., Adu-Kumi, S. & Yeboah, P.O. (2016). Assessing the environmental and socio-economic impacts of artisanal gold mining on the livelihoods of communities in the Tarkwa Nsuaem municipality in Ghana. International Journal of Environmental Research and Public Health, 13(2), 160.
Pardee Center for International Futures (2016). Population. Received on 02-10-2017 from
http://pardee.du.edu/population
Periodic Table (n.d.). Received on 23-11-2017 from
http://periodictable.com/Properties/A/Density.an.html
Pinstrup-Andersen, P. (2009). Food Security, Food security: definition and measurement, 1(1), 5-7. Sarpong, S. (2017). Sweat and Blood: Deific Interventions in Small-Scale Mining in Ghana
Serfor-Armah, Y., Nyarko, B., Adotey, D., Adomako, D. & Akaho, E. (2004). The impact of small-scale mining activities on the levels of mercury in the environment: The case of Prestea and its environs. Journal of Radioanalytical and Nuclear Chemistry, 262(3), 685-690.
Suter, G.W. (2005). An integrated framework for health and ecological risk assessment. Toxicology and Applied Pharmacology, 207(2), 611-616.
Tay, C.K. & Hayford, E. (2016). Levels, source determination and health implications of trace metals in groundwater within the Lower Pra Basin, Ghana. Environmental Earth Sciences, 75(18), 1236. Teschner B.A. (2012).Small-scale mining in Ghana: The government and the galamsey
Resources Policy, vol. 37, issue 3, 308-314
Tschakert, P. (2009). Recognizing and nurturing artisanal mining as a viable livelihood. Resources Policy, 34(1-2), 24-31.
Tschakert, P. & Singha, K. (2007). Contaminated identities: Mercury and marginalization in Ghana’s artisanal mining sector. Geoforum, 38(6), 1304-1321.
Tchounwou, Paul B. ; Ayensu, Wellington K. ; Ninashvili, Nanuli ; Sutton, Dwayne. (2003). Review: Environmental exposure to mercury and its toxicopathologic implications for public health, Vol. 18(3), pp. 149-175
United States Environmental Protection Agency (1989). Office of Water Regulations and Standard: Guidance manual for assessing human health risks from chemically contaminated, fish and shellfish. U.S. Environmental Protection Agency, Washington, DC; EPA-503/8-89-002.
United Nations (2017). World Population Prospects. Received on 02-10-2017 from
https://esa.un.org/unpd/wpp/Publications/Files/WPP2017_KeyFindings.pdf
US EPA. Sediments guidelines. Received on 05-10-2017 from
http://water.epa.gov./polwaste/sediments/guidelines.cfm
Voegborlo, R.B., Matsuyama, A., Akagi, H., Adimado, A.A. & Ephraim, J. H. (2006). Total mercury and methylmercury accumulation in the muscle tissue of frigate (Auxis thazard thazard) and yellow fin (Thunnus albacares) tuna from the Gulf of Guinea, Ghana. Bulletin of environmental contamination and toxicology, 76(5), 840-847.
WHO (1990). International Programme on Chemical Safety - Methylmercury. Received on 23-11-2017 from http://apps.who.int/iris/bitstream/10665/38082/1/9241571012_eng.pdf
WHO (1991). Inorganic mercury. Environmental health criteria 118. World Health Organization, Geneva, p 147
WHO (2001). Report on Integrated Risk Assessment. WHO/IPCS/IRA/01/12, World Health Organization, Geneva, Switzerland
WHO (2011) Guidelines for drinking-water quality, fourth edition. Received on 05-10-2017 from
Wilson, M.L., Renne, E., Roncoli, C., Agyei-Baffour, P. & Tenkorang, E.Y. (2015). Integrated Assessment of Artisanal and Small-Scale Gold Mining in Ghana – Part 3: Social Sciences and Economics. International Journal of Environmental Research and Public Health, 12(7). doi:10.3390/ijerph120708133.
World Atlas (2017). Top Gold Producing Countries In The World. Received on 02-10-2017 from
http://www.worldatlas.com/articles/top-14-gold-producers-in-the-world.html
Yidana, S.M., Fynn, O.F., Chegbeleh, L.P., Nude, P.M. & Asiedu, D.K. (2013). Hydrogeological Conditions of a Crystalline Aquifer: Simulation of Optimal Abstraction Rates under Scenarios of Reduced Recharge. The Scientific World Journal, 2013, 1-8.
Appendix 1: Data Management Table
(Sub) Discipline Theory /hypothesis
Concept(s) Assumptions / methodology
Insight into the problem Human geography
Earth Sciences (Soil Science)
Push and pull theory
Certain economic, political or cultural factors can either drive (push) or attract (pull) people to move to another place. In
geographical terms, this usually concerns
migration. Hydraulic conductivity The ease at which water can flow through porous spaces and fractures in soil or rock. Push factor A negative factor that pushes or drives people to move to another place. Pull factor A positive factor that pull or attract people to move to another place. Porosity A measure of the empty spaces in a material. Fractures A break in a rock formation. For example joints or faults. Permeability A measure of the ability of a porous material to allow fluids to pass through it. Soil saturation A condition in which all pores between soil particles are temporarily or permanently filled with water. Solubility
Push and pull factors can also be applied in the concept of labour. Certain factors can push or pull people to other workplaces. Path of least resistance Groundwater moves downhill in the path of least resistance due to gravity. Water follows the path which allows it to flow most easily.
People in rural Southwest Ghana are either pushed or pulled into the small-scale mining industry, which in turn may affect the local community and environment.
The more easily water can flow through rocks and soil, the more easily heavy metals may spread through the environment.
Biology Mercury transformation theory (methylation) Methylation is a product of complex processes that move and transform mercury. Methylmercury can enter the food chain or can be released back into the atmosphere. Integrated human and ecological Risk Assessment This assessment consists of 4 steps. First, the formulation of the problem. Second, a conceptual model has to be composed which can form a visual representation of the system. This diagram has to include
consequences for both human and non-human environments and show the
regulating
systems. The third step is an analysis gaseous chemical called ‘solute’ to dissolve in a solid, liquid, or gaseous ‘solvent’. Transformation The conversion of a substrate to a product. Methylation The addition of a methyl group on a substrate, or the substitution of an atom by a methyl group. Bioaccumulation The accumulation of substances (heavy metals) in an organism. Heavy metals A metal of relatively high density, or of high relative atomic weight. Toxicity The degree in which a chemical substance is toxic or poisonous (to which degree a substance can damage an organism). Mortality
The state of being
Ingested dose of pollutant is equal to the absorbed dose (United States Environmental Protection Agency, 1989). Cooking has no effect on pollutants (Forti et al., 2011) Methylmercury can be formed from inorganic mercury in presence of microbes that live in aquatic systems as lakes, rivers, sediments and soils. The methylation process results into a more mobile or more lethal product that can enter the food chain. Methylmercury is a bioaccumulative environmental toxicant. Through the ingestion of fish, vegetables, fruit and other crops, heavy metals can accumulate.
Environmental sciences which consists of an exposure assessment and a dose-response assessment. At last there will be a risk characterization which combines the outcome of both assessments to be able to predict potential consequences for all stakeholders (Suter, 2005). DPSIR framework Driving forces, Pressures, State, Impact, Responses framework. “Social and economic developments exert pressure on the environment and as a consequence, the state of the environment changes. This leads to impacts on e.g. human health, ecosystems and materials that may elicit a societal response that feeds back on the driving forces, on the pressures or on the state or impacts directly, through adaptation or curative action” mortal. Driving forces Social, demographic and economic developments that occur in societies. An example is population growth, which lead to changes in production and consumption and thereby exert pressure on the environment. Pressures Developments in emissions, the use of resources and the use of land. An example is CO2-emissions per sector. State Quantity and quality of the environment. Examples: fish stocks, The framework uses indicators. An example of an indicator we use regularly is our body temperature. It provides information on our physical condition. Environmental indicators also provide information on phenomena related to environmental quality. The DPSIR
framework will give a clear overview of all driving forces involved in the small-scale gold mining sector in Ghana. And shows the consequences of all social, demographic and economic developments that have occurred. With this knowledge, suggestions can be made for possible solutions.
concentration of phosphorus in lakes. Impact Impacts are parameters that directly reflect changes in environmental use functions by human. It also includes health impacts. An example is: loss of terrestrial
biodiversity. Responses Responses of society and of the government to prevent, compensate or adapt to changes in the state of the environment.
Appendix 2: Sampling method and locations
Samples for this research were taken in the Ashanti region in Ghana in April and May, 2017. 4 farms were chosen on which the sampling was performed.
A plot of 0.5 hectare was measured out and
then divided into 12 subplots. In each subplot a soil sample was taken, this was done in a
zigzag manner. These samples were obtained from the topsoil (the upper 0-15 cm) after
removal of the plant debris. Each sample weighed about 30 grams and was combined by
putting it in the same zip lock bag. This created a mixed sample that decreased the statistical
effect of spatial soil differences. Another mixed sample was taken from the same field but in
the mirror image of the first sample track. The bags were marked in the order and field it
was taken. Field one sample 1 is 1.2 whereas the control sample was marked 1.2. In the lab
of the UvA a heavy metal water analysis was carried out from which the mercury results
were obtained.
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
X
x
x
x
X
x
x
x
X
Appendix 3: Mercury concentrations of soil samples, derived from 4 different
locations in Ghana
Sample Hg 253.652 (mg/L) 1.1 0.600 1.2 0.641 2.1 0.670 2.2 0.602 3.1 0.710 3.2 0.640 4.1 0.615 4.2 0.612 5.1 0.649 5.2 0.639 6.1 0.612 6.2 0.649 7.1 0.662 7.2 0.645 8.1 0.672 8.1 0.652 9.1 0.638 9.2 0.674These mercury concentrations are measured in mg/L. For this research values had to be obtained in μg/kg in order to be able to compare them with concentration found in literature. The density of Hg is 13.6 g/cm3 (Periodic Table, n.d.).
All of the above values were converted according to this calculation: 0.600 mg/L → ? μg/kg
1. 0.600 mg/1000 = 0.0006 g
2. 0.0006 g/1 * 1 cm3/13.6 g → 0.0006/13.6 = 4.41 * 10-5 cm3 3. 4.41 * 10-5 cm3 = 4.41 * 10-5 mL
Appendix 4: Mercury concentrations from soil and cassava of
Adjorlolo-Gasokpoh, Golow & Kambo-Dorsa (2012)
Mercury
concentration in cassava tissues Bogoso (μg/kg)
Mercury
concentration in surface soil Bogoso (μg/kg) Mercury concentration in soil samples Ashanti (μg/kg) Mercury concentration in cassava Ashanti (expected) (μg/kg) 105,46 125,29 44,1 23,26275 113,38 151,11 45,59 24,048725 121,58 206,41 45 23,7375 122,08 208,04 45 23,7375 127,45 209,59 45,22 23,85355 135,8 213,94 46,91 24,745025 138,61 217,96 46,99 24,787225 149,08 230,29 47,06 24,82415 152,11 238,58 47,13 24,861075 167,67 242,01 47,43 25,019325 195,47 255,03 47,72 25,1723 66,6 255,16 47,72 25,1723 75,62 262,12 47,94 25,28835 78,75 295,72 48,68 25,6787 89,29 308,58 49,26 25,98465 98,25 316,52 49,41 26,063775 - 317,01 49,56 26,1429
- 352,52 52,21 27,540775
The Bogoso concentrations were used to estimate the cassava concentrations of the derived samples from the Ashanti region. In Bogoso, at average 52.75% of the mercury in the soil was absorbed in cassava, so that percentage was used to calculate the cassava concentrations from the Ashanti region.
