CLEANING THE BROEKPOLDER: AN INTERDISCIPLINARY ASSESSMENT. SCORING DIFFERENT ENVIRONMENTAL REMEDIATION METHODS FOR THE BROEKPOLDER

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Source image I: https://www.fdertiebroekpolder.nl/

CLEANING THE BROEKPOLDER

AN INTERDISCIPLINARY ASSESSMENT: SCORING DIFFERENT

ENVIRONMENTAL REMEDIATION METHODS FOR THE BROEKPOLDER

ARIAN VAN HUIS FLORIS VAN LITH JUSTIN KERKMEIJER LOTTE MOLENAAR 30-05-2018 UNIVERSITY OF AMTERDAM

INTERDISCIPLINARY PROJECT IN COOPORATION WITH BALANCE & MSc. FENNA HOEFSLOOT

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Abstract

The Broekpolder is a recreational area of 400 ha in South-Holland that has been contaminated with large amounts of sludge from the Rotterdam Harbour. The sludge contained high concentrations of aldrin, dieldrin and heavy metals and therefore poses an ecological risk, thus the area has to be remediated. The Broekpolder is a Social-Ecological-System, and is characterized by a set of resources (cultural, natural, and socioeconomic), of which the flow and use is regulated by a combination of (oftenly linked) ecological and social processes. For the users of the Broekpolder it is, therefore, desirable to preserve its current ecosystem services. This research compares three remediation methods according to a mutual relative scoring system. Elevation is used as the baseline conventional method, while the sustainable methods phyto- and bioremediation are scored relative to it. The mutual relative scoring system is divided in three pillars of sustainability; environment, economy and society. Phytoremediation performs best overall, however there a uncertainties regarding its efficiency. Elevation is outscored by the sustainable methods in the environmental pillar, but has been proven to be efficient. Moreover, for bioremediation further research is required regarding its applicability on site. Ultimately, the decision on which remediation method to implement is not within the scope of this paper. However, hopefully the involved parties can use the mutual relative scoring system and its specifications to decide which remediation method is most suitable for the Broekpolder, by which the governance system of the SES influences the other subsystems, who together produce ‘improved’ system-outcomes, and in this way more beneficially ecosystem services.

Introduction

The Broekpolder is a recreational area of about 400 ha, located in the municipality of Vlaardingen in the Dutch province of South-Holland. The area is also partly owned by borough Midden-Delfland and Natuurmonumenten. Between the years 1958 and 1967, large amounts of sludge, originating from the Rotterdam harbour in the Netherlands, has been dumped in the Vlaardingse polder (Maka et al., 2009). As a result of these practices, the polder has been transformed into an incremented plateau of seven meters high, rising up above the surrounding lowlands (Balance, 2017).

Building plans for the Broekpolder area were cancelled in begin ’70s because the sludge is contaminated, and real estate development on contaminated soil is prohibited in The Netherlands, until contamination has been removed (Litjens, 2017; Rijkswaterstaat, 2017). However, remediation did not take place then, because it had no urgency; instead, some trees were planted on the dumped sludge and the further ecological development was assigned to nature itself. The rough character attracts organisms as well as people, and as a result, a recreational function for the area manifested (Bakker, 2018; Stadsarchief Vlaardingen, n.d.).

The area attracts a large variety of visitors; for example joggers, children and people who walk their dog (Maka et al., 2009). However, it also serves an important ecological function. The Broekpolder is home to over 500 different species in tall plants, whose habitat alternates between ruggedly looking wood-, grass- and wetlands (ibid). Additionally the area contains a large variety of insects and presumably around 80 different species of breeding birds which are locally active (ibid.). In this light, the Broekpolder should not only be seen through the lens of recreational functionality, but also as an important habitat for many native species, which can be considered special within the densely populated and bricked environment of the Randstad.

Figure 1: Triad (SKB, 2016).

However, contaminated soil of the Broekpolder is currently, in 2017/2018, an active discussion topic, as it could form an ecological risk. Such a risk signifies ‘the presence of a perhaps alarming concentration of harmful particles in an environment, which are, at least at some point in history, released by humans’ (EEA, 2016) and can be indicated by the integration of a chemical analysis, toxicological information and ecological impact (figure 1): In case of the Broekpolder, ‘drins’, which are notorious Persistent Organic Pollutants (POPs) and the collective name for Aldrin and Dieldrin, are present in the soil (Balance, 2017). These are formerly used insecticides, whose chemical particles have the property to be a possible harm for the living organisms in the Broekpolder ecosystem (Jorgenson, 2001). In the Broekpolder it was already found that earthworms had accumulated drins, and the absence of moles in the specific area was also attributed as further evidence of the everlasting presence of soil toxicants (Bakker pers.com., 2018).

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Other known chemical and toxicological information for the Broekpolder is based on its originating soil from the Rotterdam harbours, which consists of the mentioned POPs and heavy metals like copper (Cu), cadmium (Cd) and zinc (Zn) (Balance, 2017). Hydrophobic POPs bioaccumulate up the food chain, posing an increasing effect risk for predators higher up, such as birds (Jones & de Voogt, 1999). In addition, heavy metals could potentially leak to water sources and cause stress in plants, killing them or causing functional disabilities if they are unable to adapt (Shah et al., 2010). The distribution of the contaminants is not equal over the area, therefore the Broekpolder has been divided in several subsites by level of contamination, based on a soil investigation conducted by Osté (2015) (figure 2). The highest amounts of drins are found in area 7 ‘a’ and ‘b’, followed by areas 5, 12 and 13Z. The highest values of heavy metals occur in area 7b, 8 and 8a and 9. Areas 1,2,3,4 and 6 are not highly polluted.

Figure 2: Subsites within the Broekpolder (Osté, 2016).

The issue has always been acknowledged, but over the last approximately five years, the central government of the province South-Holland has decided that a remediation project must take place (Balance, 2017). They are motivated by the expected ecological risk and the current rewriting of the, for this area applicable, Law of Soil-Protection (Wbb), which newly incorporates an interesting pillar: this pillar comprises the dealing with residual historical pollution, where the focus is on a non-uniform remediation approach. This entails that the main responsibility for remediation policy is with the involved municipalities and stakeholders (Rijkswaterstaat, n.d.). This approach rhymes with the present multi-level (or polycentric) government strategy in the Broekpolder, constructed as a triangular relationship, wherein the three different parties are: I) a federation which represents the concerned citizens, II) the college of citizens and councillors, and III) the local council of Vlaardingen itself. Within these parties, different collaborators and their concerns are incorporated, and each of

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the groups have their own rights, tasks and authorizations with regard to the area (Maka et al., 2009). A polycentric approach reinforces the achievement of benefits at multiple, non-hierarchical, scales, as well as it facilitates experimentation and learning from experience and each other (Ostrom, 2010).

The focus of this research will therefore be on proposing, discussing and mutually weighing sustainable ways in which the Broekpolder can be remediated so as to improve its ecosystem services. To accomplish this remediation analysis, first, a theoretical framework which elaborates on the relevant concepts will be presented. Secondly, the problem will more precisely be defined and the interdisciplinary approach within this research will be introduced. Afterwards the research design will be discussed with the expected timeframe of this research. Data and results of the research will be visualized and finally a conclusion can be drawn, which should lead to relevant policy advice for the Broekpolder.

Theoretical Framework

Social-Ecological Systems

The interaction between humans and nature indicates that the Broekpolder is a Social-Ecological System (SES), what means that the area is characterized by a set of resources (cultural, natural, and socioeconomic), of which the flow and use is regulated by a combination of (oftenly linked) ecological and social processes (Becker, 2012).

The introduction of this Social-Ecological Systems concept in science is the result of an international discourse on human/nature interactions (Becker, 2012). This indicates the assumption that most ecological systems are not solely ‘natural’ anymore, but also ‘social’, because human activities strongly influence the earth’s ecosystems (ibid.). So, when humans use ecological resources, or enjoy services or benefits of a system, this can be conceptualized as a complex SES (Ostrom, 2009), of which the complexity is explained by the involvement of human as well as biophysical values and (un)certainties (Dietz et al., 2003). Ostrom (2009) illustrates the SES complexity by a framework, which shows four different, but interacting, subsystems, who should be seen as the bridge between the human (S), and biophysical (ECO) aspect of the SES (figure 3).

Figure 3: The core subsystems in a framework for analysing Social-Ecological Systems (Ostrom, 2009 p.420).

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The subsystems on the left side of Ostrom’s framework shows the biophysical aspects: This includes the complete resource system (RS), which is the entire ecological system or area, including all its ‘nature functions’; the resources and services provided by the system. The resource units (RU) in itself are the other biophysical component, which are for example the trees and organisms present in the RS. On the right side, the social aspects of the SES are visualized. Here, the users (U) of the area come to mention, which involve both physical and spiritual enjoyers. Also, the governance system (GS) is addressed, what comprises the social organization and network structures of the RS. Ostrom (2009) emphasises, by this framework, not only the complexity and disciplinary overlap that comes with an SES, but also the importance of the acknowledgement of the interconnectedness of all subsystems, to create a complete understanding, when taking this SES approach.

Ecosystem Services

The outcomes produced by the SES have (again) an influence on the users of the system, as shown by the arrow between these aspects in figure 3. If the users experience these outcomes as socially beneficial, they can be perceived as ecosystem services (ES): Largely based upon the study of Boyd and Banzhaf (2007), Fisher et al. (2009) presents a clear definition of ecosystem services, which will therefore be applied in this research, and states: “ecosystem services are the aspects of ecosystems utilized (actively or passively) to produce human well-being” (p.645). The difference with the study of Boyd and Banzhaf lies within the inclusion of indirect ‘consummation’ of ecosystems as well. Cultural services are to the most extend an example of indirect services, as they include social relations and spiritual and aesthetic values. These services, in combination with many others, can establish the ‘recreational benefit’ of an area. In the context of the SES approach, the function of the Broekpolder as a recreational area can thus be seen as a benefit of the system, which is maintained by the combination of cultural and ecological ecosystem services which the area provides for the local and nearby communities (Boyd & Banzhaf, 2007).

The concept of ecosystem services has widely been adopted as a framework for weighting and identifying the social and ecological values of an area, in relation to management strategies and decision making (Daily, 1997; Chan et al., 2012). The ecological ecosystem services includes resource provisioning for humanly use, residential values for organisms, health of the environment and the availability of resources and resilience to maintain the system (Daily, 1997). When the system is at its ecological optimum, the social benefits are, according to Daily (19970), most favourable as well. Other social benefits of ES fall within the cultural category, which is defined by the Millenium Ecosystem Assessment (MA) as: “The nonmaterial benefits people obtain from ecosystems through spiritual enrichment, cognitive development, reflection, recreation, and aesthetic experience, including, e.g., knowledge systems, social relations, and aesthetic values” (2005 p.40). These cultural aspects are a key in decision-making context (GS in SES), becsuse they can impede the goal achievement, as stated by the particular governing organ(s), when they are not acknowledged (Chan et al., 2012).

POPs and heavy metals

As mentioned in the introduction there are several problems due to the presence of drins and heavy metals in the soil and surface water of the Broekpolder. The term ‘drins’ is a combined name for aldrin and dieldrin, which are insecticides that have been widely used from 1950 onwards till the 1970s. Both are toxic and bioaccumulative, and part of a group of twelve chemicals categorized as Persistent Organic Pollutants (POPs) (Jorgenson, 2001). The production and use of POPs has been restricted in the convention of Stockholm in 2001. POPs are hazardous to humans and the environment if concentrations in a specific area are high

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(WHO, 1989). Both aldrin and dieldrin are easily adsorbed by soils and transported by ways of erosion. They accumulate both in human and animal adipose tissue and lead to serious health problems in mammals; in humans they lead to convulsions, a hyperexcitable state of the brain and a predisposition to cardiac arrhythmia (Frazer, 2000). Another way in which they can end up in humans is by percolating through the soil and dissolve in groundwater, which is used as a drinking water source (ibid.).

This contamination optimum the ecological state of the Broekpolder’s SES, as the RS, and possibly some RU as well, are negatively influenced by these toxins. The assumption of this presence is based on measurements done by Chemielinco in 1995. This classification as ‘highly contaminated’ is a form of qualitative risk assessment, whereby qualitative hazard analysis is aimed to assist a risk manager in policy making decisions (Coleman & Marks, 1999). Chemielinco divided the area into sub-areas whereby samples are measured in the soil. However this data of Chemielinco is untraceable, but this paper is still the basis for many reports to state that certain subareas of the Broekpolder are ‘highly contaminated’.

Fortunately, in 2001, a qualitative and quantitative risk assessment has been done by Ma, Bosveld and van den Brink. In this paper a risk-coefficient ‘R’ for bovine animals is calculated, whereby values of the ‘R’ are qualified. If ‘R’ is equal or smaller than one, the effects on a bovine is negligible. A ‘R’ of 1-10 indicates a relatively low chance of effects. A ‘R’ of 10-100 means that there is a highly likely chance of effects towards the bovines, and a ‘R’ of 100 and higher means that the toxic effects on the bovine will occur and could bring serious damage to the bovine, which indicates a ‘highly contaminated’ soil (Ma, Bosveld & van den Brink, 2009). Indeed, the drins have a R>100 based on the values of Chemielinco, while other contaminants like As, Cd, Co Hg, Pb, Zn are not exceeding a ‘R’ value of 1 (ibid.). Ma, Bosveld and van den Brink have calculated the ‘R’ for heavy metals themselves, based on their own measurements. The ‘R’ value of Cu (Copper) in subarea 11 (Figure 2), has a value of 1.03 while the rest is lower. For drins the information from the study of Chemielinco is used within this research, as there are no new values available.

Bioremediation & Phytoremediation

In order to preserve the SES in the Broekpolder, sustainable remediation methods are the most obvious to remediate the area. Both bioremediation and phytoremediation are very promising sustainable remediation methods.

Bioremediation is the microbial breakdown of toxic pollutants in order to eliminate or reduce them to non-toxic concentrations. Either in a laboratorium cultivated microorganisms can be used, or microbial degradation of pollutants is enhanced by supplementing naturally occurring microorganisms (Gavrilescu, 2004; Frazar, 2000). Depending on the characteristics of the contaminant, the most suitable microorganism is selected. Bioremediation is found to be less expensive than other detoxification methods and is proved to degrade up to 99 percent of pollutants in the soil (Frazar, 2000). However, in the case of heavy metals the situation is different, as they are not biodegradable; microorganisms can only extract them by bioaccumulation. Several microorganisms have the ability to adsorb and bind heavy metals to their biomass, whilst removing them from the environment (Baldrian & Gabriel, 2003). These metal sorbing microorganisms are called biosorbents and are, according to Volesky (1999) very effective. Considering this, bioremediation could maybe be used to remove the discussed POPs and heavy metals from the Broekpolder’s SES, by which the state of the RS improves, what is conducive for the SES’s provided ecosystem services.

Phytoremediation is a technology that uses either genetically engineered or wild type hyperaccumulators: plant species that are able to tolerate extreme amounts of pollutants

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(Rascio & Navari-Izzo, 2010). They deploy methods like phytoextraction, rhizofiltration or phytovolatilization, which effectively either store or degrade the pollutant (Salt et al., 1995). Targeted chemicals range from heavy metals to POPs, like aldrin and dieldrin. Depending on the pollutants, a type or various types of plants are chosen, as different types have specific characteristics to remove contaminants from the soil (ibid.). All in all, the relatively low cost (Wan, Lei & Chen, 2016), the wide variety of pollutants that can be remediated, subsequent effectiveness (Salt et al., 1995; Kang, 2014), added ecological benefits and public acceptance (Kang, 2014) seem to make this an attractive option for environmental remediation. This sounds, as well, promising with respect to the Broekpolder’s SES; to improve the ecological aspects of the system, which again supports the social side of the system as well.

Problem Definition

The presence of POP’s and heavy metals in the soil of the Broekpolder, caused by the earlier deposition of contaminated sludge, induces and ecological risk in the area. This risk directly affects the ecological subsystems of the SES in a negative way, and an indirect impact for the social side of the system is established through the interactions between the four subsystems in the SES. Therefore can be said that the ecological risk impedes the ecosystem services of the Broekpolder. To overcome this problem, remediation has to take place in the area. However, this solution is not as easy as it seems: different types of remediation methods could be applied in the area, but, as the issue concerns a SES, many aspects and actors have to be taken into account before a decision can be made.

The complexity is further increased by the incorporation of the not always straightforward sustainability concept. To make this term concrete and measurable, the terminology of SuRF-UK (The UK Sustainable Remediation Forum) is used within this research, which defines ‘sustainable’ in terms of three indicators: ‘environmental’, ‘economic’ and ‘social’. For a remediation method to be sustainable, the benefits should be greater than the negative consequences of its implication (Bardos et al., 2011). This means that the possible remediation methods should be reviewed by their environmental, social and economic characteristics. Afterwards, this information can again be integrated in the SES framework, to be able to give meaningful remediation recommendations regarding the Broekpolder area.

So the aim for this research is to explicate the two introduced remediation methods, ‘bioremediation’ and ‘phytoremediation’, by their sustainable characteristics, and compare them with a more conventional remediation method; ‘elevation of the area’, by the use of a mutually relative scoring system. In this way is explored in what sustainable way the Broekpolder can be remediated so as to improve the ecosystem services of the area.

Interdisciplinary integration

To ensure this research with a complete understanding of the Broekpolder’s SES, the biological-, social-, and earth sciences disciplines are converged. This is necessary, as the interactions within a SES show that an understanding of all subsystems, including their characteristics and background, is needed to be able to say something applicable for the whole system (figure 4). This interdisciplinary integration leads to a holistic view with regard to the system, by which accurate implication is enhanced, and a substantiated joint approach towards sustainable remediation methods can be given.

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Figure 4: Interconnected disciplines through SES (Ostrom, 2009 p.420).

Research Design

In this literature study, the ultimate goal is to determine the environmental remediation method that maintains, or improves, the ecosystem services of the Broekpolder in the, defined as “most sustainable”, way. The term ‘sustainability’ is already explained by the way SuRF-UK approaches the topic. This approach is very similar to the well-known ‘three pillars of sustainability’, and places emphasis on an integrative, inter- and transdisciplinary approach to environmental policy decisions (Hansman, Mieg & Frischknecht, 2012). SuRF-UK also subdivides these pillars into assessment criteria by which they can be measured, as depicted in figure 5 below, from Huysegoms & Cappuyns (2017). This method will be applied in this study in a more simplistic form, by only discussing ‘relevant’ environmental, social and economic indicators, disregarding the other aspects visualized in figure 5. The ‘relevant indicators’ with regard to this research are listed in table 1 below.

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ISSUES EXPLANATION

Air Emissions that affect local air quality or global climate change (such as greenhouse gases, particulates)

Soil & ground conditions

Changes in the soil condition in such a way that ecosystem services are affected

Groundwater & surface water

 Changes in the release of contaminants, organic carbon or other particulates that affect groundwater

 Issues associated with flooding

Ecology  Changes in local ecology: flora, fauna and their food chains. Changes in community structure/function

 Effect of “remediation disturbance” (light, noise, vibration) Natural resources &

waste

Impacts and/or benefits for: land and waste resources, use and substitution of primary resources, water use/disposal/abstraction/, handling of materials on and off-site and waste disposal resources ECONOMIC

ISSUES EXPLANATION

Direct economic costs/benefits

Consequence of capital and operation costs associated with the work of implementing and completing the remediation method (short-term) Indirect economic

costs/benefits

Indirect costs/benefits: debt, internal financial allocation for relevant stakeholders, fines, tax. consequence for the areas economic

performance (long-term) Project lifespan &

flexibility

Factors affecting chances of success, the ability to respond to changes in circumstances, robustness to climate change effects or altering economic circumstances, financial allocation for ongoing institutional controls.

SOCIAL

ISSUES EXPLANATION

Human health & safety

 Chronic and acute risks

 Risk management in the long term: mitigation of unacceptable health risks

 Risk management in the short term (during the remediation): site workers, public, emissions

Neighbourhood & locality

 Social effects of possible changes in site usage.

 Changes in way of functioning and accessible services

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community involvement

 Effects on local culture

 Transparency and involvement of community

 Compliance with local policy/spatial planning Uncertainty &

evidence

 Quality of research and accuracy of record taking

Table 1: The three pillars of sustainable remediation methods, subdivided into different issues with the respective elements they take into consideration. The table has been taken from Huysegoms & Cappuyns (2017) and issues as well as explanations have been modified for the

purposes of this paper. A mutual relative scoring system

To properly compare different remediation methods, a mutually relative scoring system is made, which determines to what extent these issues are addressed for each method. Several sanitation methods are compared through extensive literature studies, where data on effectiveness and applicability can be analyzed according to the method devised by SuRF-UK. With the information available, remediation methods can be analyzed through the variables listed in table 1. All of these variables can be scored on a scale from 0-5, where the values 0 and 1 indicate the lowest sustainability rates, values 2 and 3 are considered intermediate, and values 4 and 5 are the two most sustainable scores based on mutual comparison (figure 6). The results are written down in a schematic overview, which will eventually provide a comparison table.

Figure 6: Scoring scale from 0-5.

The way parameters are scored and how sustainability is defined, according to this ranking system, is as follows: Elevation is considered as the conventional remediation method, and serves as a “baseline method”. The decision to use this method as baseline was made based on the current speculations in the Broekpolder, where elevation seems to be seriously considered as the solution with regard to the ecological risk in the area (Bakker, pers.com., 2018). When comparing the ‘unconventional methods’; phytoremediation and bioremediation, with elevation, as well as between themselves, this tactic provides a good insight into the advantages and disadvantages of each method, relative to each other. The scores that parameters are given within elevation are therefore crucial, and require thorough analysis.

As far as the actual scoring is concerned; not only are all parameter scored relative to the baseline method, they are also determined through assertion with different methods and standards. For instance, “Air” in the environmental pillar (see table 1 for definition): this parameter could be defined by the weight of greenhouse gases emitted over the period of a year, and is therefore an easily quantifiable variable, of which the outcome can then be graded on a scale of 0-5. However, such a strategy is much less applicable in a parameter as “Commitment & community involvement”, which requires a qualitative and evaluative approach from which a 0-5 score is distilled.

In the analysis, each selected indicator of table 1 is discussed for all the three remediation methods. Based on the evaluation of a data gained from existing literature, and by mutual comparison, an estimation of the best applicable score for each parameter, with regard to the remediation methods, is applied, to create a complete comparison table.

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Analysis

In this chapter of analysis, mutually relative grades will be given to the remediation methods based on the sustainability indicators, against the background of the processes applicable to the Broekpolder and its SES dynamics. Before the alternative remediation methods of phyto- and bioremediation are discussed, the baseline method of elevation will be reviewed. Eventually an overview will be given, as the methods are set out in the comparison table. Elevation

Elevation is considered to be a conventional remediation method and seen as the baseline for the indicators. The scores of the indicators are made on the assumption that the whole area is altered in height by 50 cm of slightly contaminated ground. This ground is still slightly contaminated, meaning that no building projects, could be constructed on this ground. Nevertheless, it could keep its creational function. Another assumption is made that all this ground is transported from the ground-bank in Blekensgraaf. All indicators are score in the section below.

Environmental: Air Grade: 0

30,7 km from Blekensgraaf to Broekpolder: 61,4*103.480 truck dumps required (see Project Lifespan & Flexibilty) = 6.353.672 km total = 3.947.912,3171 miles total cumulative distance covered by all trucks.

The calculation of total emission values below is based on EPA (2008). - VOC = 143230 tons (tn) of emission

- CO = 1127523,76 tn - NOx = 193131,87 tn

- Small Particulate Matter (PM2.5) = 1934,48 tn - PM10 = 2408,23 tn

Environmental: Soil & ground conditions Grade: 1

The aeration of roots are affected with soil alteration. Figure 7 below shows that in a sandy soil, the groundwater level is at 60 cm in depth, after an alteration of 40 cm sand, there is a decline in its aeration from 900 to 500 mg/m2/uur (Kopinga, 2011). For most trees currently present in the Broekpolder, such an oxygen deficiency would mean certain death as the roots do not receive enough oxygen to function normally.

Groundwater Level could alter by the stagnation of rainwater (Kopinga, 2011). As the elevation in the Broekpolder would, mean a soil level increase of 50 cm, death and weakening of roots will occur, making it that trees more are susceptible for fungi (ibid).

Figure 7: Oxygen supply of the y-axis in mg/m2*uur and thickness of the layer on the x-axis in cm. The blue line is representative for sand and the green for loam (Kopinga 2011).

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Environmental: Groundwater & surface water Grade: 2

The run-off of this soil in the surface water will cause that these contaminants in the elevation layer still end up in the surface water (Wauchope, 1978). Further research is needed to make a approximating on values that end up in the ground and surface water. So there is some uncertainty concerning the score of this indicator.

Issues associated with flooding could be present in this method of remediation, as water stagnates in the soil; but this is case-specific, so there does not have to be any complications (Kopinga, 2011).

Environmental: Ecology Grade: 0

By burying the current sediment and flora under 0.5 meters of soil, biota in the Broekpolder may undergo a drastic change. This is because the sediment effectively “chokes out” any small plants underneath that are unable to penetrate the new topsoil layer (Kopinga, 2011). Secondly, most trees are very sensitive to the practice of soil elevation since the roots are not supplied with sufficient oxygen (ibid). The amount of oxygen that can still penetrate the new topsoil depends on the oxygen diffusion resistance of the type of soil used (ibid). Sandy soils have the lowest diffusion resistance and would be the best option when considering tree viability (ibid). However, since the Broekpolder consists mostly of peaty soils and only a small fraction of sandy soils (Maka et al, 2009), covering the area in sand will lead to changes in properties of the rhizosphere. Making it that new plants and microorganisms need to be suitable to a new situation to survive (Harper, Williams, & Sagar, 1965; Marschner, Crowley, & Yang, 2004).

Environmental: Natural resources & waste Grade: 2

Elevation has a positive or negative impact considering: land and waste resources, use and substitution of primary resources, water use/disposal/abstraction/, handling of materials on and off-site and waste disposal resources. Concerning the latter, the elevation of the soil is not creating any waste or disposal of waste, because the contaminated soil is isolated. Besides, the land and water resources that are taken up by plants are not available to the plant anymore as a new rhizosphere is deposited by the elevation method. Furthermore, a new ditch system has to be created in Broekpolder because the current ditch system would be influenced or vanished by the alternation method.

Economic: Direct economic costs/benefits Grade: 3

The direct economic costs are estimated on €3.122.315,61 (For elaboration see appendix A1). Economic: Indirect economic costs/benefits Grade: 1

The renewal of plants, and the whole new design of the Broekpolder, could be seen as the indirect economic costs. The rebuilding of the whole Broekpolder, including its land cover, is unavoidable if a new soil layer is deposited on top of the Broekpolder, as it is most likely, but not certain, that plants and trees will not survive the deposit. This will be a very costly, and time consuming, process (Summer et al., 2015).

Economic: Project lifespan & flexibility Grade: 5

The lifespan of the elevation only is circa 2 years. (For elaboration see appendix A2) But afterwards the whole area has to be rebuilt and re-grow again.

Social: Human health & safety Grade: 4

The sediment that is to be deposited is most likely contaminated, although less than the Broekpolder. However, this means that the transportation and deposition of sediment poses a risk to workers and/or localities, since spreading of dust particles by the wind is inevitable

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during handling. It is impossible to determine the exact risk however, since compound hazard analysis would have to be performed.

Social: Neighbourhood & locality Grade: 0

In total, 103.478 trucks filled with sediment will need to be deployed to completely elevate the Broekpolder. These trucks will constantly take up the freeway and roads adjacent to the Broekpolder for a period of at least 2 years. In this estimation, it is assumed that there are no night shifts, so no construction lights are needed, resulting in minimum light pollution.

It is certain that local inhabitants will experience disturbance related to dirt from dust particles, noise from passing and working trucks and construction work and vibration, as is common in . Apart from this infrastructure related nuisance, the whole Broekpolder, as the recreational area it is, will be disturbed completely. Even though the soil deposition will be executed part by part, the whole appearance of the area will change. Even when the reconstruction is over, all the new planted trees and vegetation has to grow, and it is most likely that the Broekpolder will never become exactly the way it was.

Social: Communities & community involvement Grade: 2

Soil elevation must be done by third parties and thus the local community has no influence over the remediation process once this method has been chosen. However, after the project has been complete, inhabitants could be asked to participate in the planting and maintenance of the new flora and could even be asked for input on the design of the new elevated land plots.

Social: Uncertainty & evidence Grade: 3

Surprisingly, there is little to find concerning scientific research. Only few papers discuss the effects on vegetation (Kopinga, 2011; Geluk, Koppelaar & Doorenbal, n.d.), but do not discuss the social implications. This could, however, also been seen as an increasing factor regarding the uncertainty as a social indicator. It must be said, however, that there exists a great body of gray knowledge about the effects and intricacies of soil elevation as a way of remediation. Therefore, it can scientifically not be concluded nor excluded that elevation is an effective way of environmental remediation. However, because its widespread use is an indication of its effectiveness and merit, it receives an average grade of 3.

Phytoremediation

The second remediation method evaluated is phytoremediation. Suitable plant species need to be chosen to maximize the effect of phytoremediation; such as some members of the Cucurbitaceae family (pumpkins), as they take up drins out of the soil, while they are tolerant for it (Otani, Seike & Sakata, 2007). Temperature is taken in consideration as environmental condition, leading up to the following suitable pumpkins: the winter squash Cucurbita maxima, the Cucurbita moschata, and the fig leaf squash Cucurbita ficifolia (ibid). Furthermore, the Indian-, Chinese- and brown mustard Brassica juncea are used for the phytoremediation, as they take up cadmium, copper, lead, and zinc (Lim, Salido, & Butcher, 2004) and have been the subject of most research for heavy metal phytoremediation (Salt et al., 1995). All these plants are phytoextractors, which means that the fruits of the plants cannot be harvested for consumption and must be harvested to prevent the recycling of heavy metals into the system.

Plants respire oxygen and therefore emit no greenhouse gases. However, overseers will need to maintain, harvest and cultivate the plants, and this will most likely require cars and vans transporting green waste. Compared to the heavy lift trucks this is negligible. However,

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because phytoremediation will take much longer to remediate the area, the accumulative effect downgrades the score from 5 to 4.

Plants help the cycling of nutrients and aggregate soil particles, preventing erosion and leaching and improve the condition of microbial communities in the soil by engaging in symbiosis with soil-based microorganisms. However, with phytoextraction and rhizofiltration, there is the risk of toxic plant litter being spread to adjacent habitats or ending up in the food chain through herbivores, even though it is not likely that they would eat the plants (Nevel et al., 2007). (For elaboration see Appendix A3)

Plants contribute to the water cycle through the process of evapotranspiration, returning soil water to the atmosphere and keep the soil moist by preventing the impact of direct sunlight. Groundwater levels are too deep for the roots to reach, so this is not affected. The roots are barely a half meter long and the groundwater level is around -3 meters beneath sea level (Loots Grondwatertechniek, 2017).

Environmenta: Ecology Grade: 3

Since the cucurbits are imperfect flowers, they rely heavily on insect pollination. The cucurbit flowers attract a wide variety of bee and honey- and bumblebees species, what is considered beneficial for the whole ecosystem and surrounding ecosystems, because they are important for maintaining biodiversity and the biological productivity of an area (Devillers & Pham-Delègue, 2003).

However, beetle species (Lupertini), known to occur in the Broekpolder, will feed on all cucurbit species as well, which poses an ecotoxicological risk of accumulating drins up in the food chain (Metcalf & Lampman, 1989). There exist pesticide-free control methods to perceive this thread, but they cannot guarantee (yet) that the spreading of drins will be stopped completely (Elliott, 1995). (For elaboration see Appendix A4)

There is a disposal of resources, as the vegetables are withdrawn from the field. These vegetables are contaminated, therefore they are not eatable and can be seen as waste. Furthermore, nutrients are subtracted from the soil as well. Water resources are not that much influenced by the plants itself, although it the roots hold more water in its ryhosphere (Kamh et al., 1999). A part of the rainfall is withdrawn by the plants and the rain is not going to the groundwater.

The phytoremediation cost expectation for the entire project is stated 3.2 million US$, which makes it cheaper than elevation. However, it is likely that pests and premature dying of plants will occur, what asks for re-investments (Salt et al., 1995). (For elaboration see Appendix A5) Economic: Indirect economic costs/benefits Grade: 2

Should the function of the Broekpolder remain as it is now, one way in which indirect benefits can be expressed is ecosystem service improvement, the monetary valuation of which is something that lies outside the scope of this paper. Nevertheless, because recreational value is closely linked to a (perceived) healthy ecological landscape and phytoremediation has strong aesthetic values, this might attract more visitors to the area.

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A second indirect cost is tied to the nature and duration of the project: because large areas will need to be planted with the hyperaccumulating Brassicacea and cucurbits, these plots cannot be used for anything else until the project is finished. This effectively means that some parts, such as the golf course will lose (economic) functionality.

Using Brassica juncea, the total time required to fully remediate all of the four most abundant metals (Cd, Pb, Cu & Zn) lies between 26 days and 2410 years. Using Cucurbitaceae, the total time required to fully remediate the two most abundant drins (dieldrin and endrin) lies between 77 days and 106 years. (For elaboration see Appendix A6)

So long as no consumption of the vegetables takes place, human risk is next to none. However, the occurrence of pests cannot be excluded and the effects of their intake of drins via Cucurbitaceae is unknown. Therefore it is impossible to say with certainty if and how insects will carry these toxins further into the food chain, and if this will eventually pose a risk to humans. However, this is extremely unlikely since the food chain of the Broekpolder is does not directly affected if IPM is implemented properly, the risk of further spreading of drins to the food chain is minimized.

Phytoremediation of the entire Broekpolder would mean that recreational areas would be transformed for the purposes of the best remediation practices. This means that the Broekpolder would undergo a drastic transformation, seeing as recreation cannot take place amidst vast fields of growing, toxic hyperaccumulators. However, phytoremediation has been perceived as aesthetically very pleasing to visitors and locals and would thus would thus contribute positively to the visual environment (van Nevel et al., 2007).

The planting, maintaining and harvesting are processes the local community could become involved in. This would require an extensive briefing of the project as well as rules and regulation concerning the prohibition of consumption of the plants. However, because of the magnitude of the project, it is unlikely that the local community will fully cover the planting and maintenance of the entire Broekpolder, most likely because of the amount of time it will take (unless a type of compensation can be offered). Therefore, a third party will most likely need to be hired).

Phytoremediation is promising, but hyperaccumulators are known to have a lower overall fitness, making them more susceptible to pests and plant diseases (Maestri et al., 2010). A second issue is that the Broekpolder is contaminated with multiple drins and metals, likely slowing down phytoremediation (EEA, 2014; EEA, 2017). Stress from environmental factors also impedes the rate of phytoextraction. (Kang, 2014). The third important limitation is the bioavailability of heavy metals especially, which ranges from 0.11 to a maximum of 3.32 percent. This could be dramatically improved by ten- to hundredfolds with chelating agents such as EDTA (Wu et al., 2004; Lim, Salido & Butcher, 2004).. However, these have been shown to induce a toxicity response in vertebrates, meaning a hazard to humans cannot be excluded (Hart, 2000).

Bioremediation

Bioremediation can be divided into to two groups; in situ and ex situ. Ex situ involves all methods that remove contaminated objects from their natural habitat to treat them in another

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place, when they are detoxified, re-introduce them in their environment. In situ remediation covers all remediation methods that take place at the contaminated site. In situ remediation is in general considered more convenient and more attractive to the parties involved than ex situ remediation, because equipment is not needed in the process. Therefore, the costs are lower and it leads to less disturbance in the SES (Boopathy, 2000; National Research Council, 1993); this again leads probably to less opposition from its users, which again simplifies governance decisions, and will therefore be the bioremediation focus in the below analysis.

There are several different microorganism species, who all have other characteristics. Some microorganisms, like fungi and algae, are able to respire carbon dioxide from the atmosphere, while others generate carbon dioxide, nitrous oxide and methane in the soil. In theory this is beneficial for the environment, because these greenhouse gases accumulate in the soil, which becomes a sink for greenhouse gases. But, due to soil dwelling and human activities, like ploughing, these gases escape the soil and are released to the atmosphere. Because there is no human disturbance in the soil in the Broekpolder and the fungi and bacteria are the most suitable microbes to remediate the soil, they respire oxygen, and no greenhouse gases are emitted (Schlesinger & Andrews, 2000).

Soil microbes mediate weathering and decomposition of organic materials. These processes create the typical division of soil horizon; these soil horizons are layers of different materials distributed throughout the soil profile. The materials that these horizons contain are soil aggregates, the composition of these aggregates form the soil structure. Soil aggregates are initiated by the chemical and physical interaction of microbes with parent material and organic matter. Therefore, microorganisms can be seen as the driving force behind the quality of soil and ground conditions (Aislabie, Deslippe & Dymond, 2013). However, in the Broekpolder case it is unlikely that the addition of the specific microorganisms will have a significant effect on the conditions of soil and ground, because they are only a very small part of the whole microorganism ecosystem.

Microbes are found to be able to degrade contaminants in water as well as in soil. By increasing the soil structure, soils can hold more water and flood risk decreases (Wardle, 1992). However, for the application of microbes to remediate the Broekpolder, further research is needed in order to find out whether or not they will be effective, for water aqueous microbes are relevant and might be efficient. But, the contaminants originate from the soil, therefore it might be more efficient to target the soil.

Environmental: Ecology Grade: 4

A healthy microbial ecosystem increases the availability of food due to the fact that the soil becomes very fertile (Wardle, 1992). The application of bioremediation will not result in direct disturbance of the ecosystem of the Broekpolder. However, it might lead to a disturbance in the microbial ecosystem, because for instance there is a fungi abundance. But, overall it is not so likely that the Broekpolder will be disturbed by bioremediation.

Stimulation of microbial population in the Broekpolder in order to degrade toxins will result in an increase in microbial activity, which will stimulate the natural resources in the Broekpolder. Thereby, because it is a natural solution, there will be no waste.

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Implementation and completion of bioremediation in the Broekpolder will become very expensive, because microorganisms that have been found to be able to degrade the pollutants in the Broekpolder have never been examined in situ. So, further specific research is required to investigate the efficiency of these microbes in situ at the Broekpolder. All the materials and professionals needed for such a project will be very expensive.

Economic: Indirect economic costs/benefits Grade: 3

In theory, when there has been found an efficient or several efficient microbes that can be stimulated in the Broekpolder to degrade the drins and accumulate the heavy metals, additional costs will be very low. Only a stimulant has to be applied to the soil, which can be for instance glucose and the natural environment will subsequently act by itself without further intervention.

Because it is difficult to measure the amount of toxins and the behavior of specific microbes, it becomes very hard to react to changes in circumstances. Therefore, bioremediation in the Broekpolder has very little economic resilience, i.e. environmental conditions in the Broekpolder change, it might be necessary to restart an in situ investigation to find out whether or not these microorganisms still have the desired efficiency. Microorganisms probably have several positive and negative feedback loops due to climate change, however because of the complexity of microbial systems the actual effects are not yet completely understood.

Human health and safety are not at risk, because bioremediation is a natural solution and it does not require any dangerous substances to humans.

Bioremediation will lead to almost no disturbances in the natural environment of the

Broekpolder, therefore there will not be any social effects due to the changes in site usage and no changes in ecosystems services.

Although, the effect on the community will be very small, transparency and involvement of the community will be hard. The microbial ecosystem eventually will have to do the work, which cannot be overseen by the local environment.

For in situ bioremediation, to be successful, there are several factors that have to be present in the environment, such as the right microbes and degradation circumstances (Boopathy, 2000). Thereby, most research on biodegradation of aldrin, dieldrin and heavy metals are conducted in laboratories with a controlled environment. This complicates the implementation of these microorganisms in the environment of the Broekpolder (National Research Council, 1993). By this knowledge gap, bioremediation is not (yet) applicable for the Broekpolder. In situ research has to be undertaken to decrease the uncertainty and from the evidence gained by this research steps may be taken.

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18 Comparison table

Figure 8: Comparison table of the different environmental remediation methods. Each method is ranked according to its performance in a subdivision of one of the three pillars of

sustainability. Green boxes depict “good” scores, orange boxes “average” scores and red boxes “insufficient” ones. For more detailed information, see: (adapted from Huysegoms &

Cappuyns, 2017).

Conclusion

The focus of this research was to shed light on the advantages and shortcomings of possible remediation methods which can be applied in the Broekpolder to improve the ecosystem services of the area. According to the mutual relative scoring system, phytoremediation has the best cumulative score out of the proposed remediation methods for the Broekpolder. In the environmental pillar, the new methods of phyto- and bioremediation outscore the conventional method of elevation, because of the little disturbance or even positive effects they will have on the ecosystem of the Broekpolder. Economically, phytoremediation and elevation scores are close, however elevation scores very low on “indirect economic costs/benefits” and very high on “project lifespan and flexibility”. Although phytoremediation and elevation scores are close, it should be taken into account that phytoremediation has Bioremediation on the other hands scores the worst, due to all the uncertainties involved, eminently in the economic pillar. Socially, phytoremediation performs the best on average. Because bioremediation does not have any negative effects on “human health & safety” and “neighbourhood & locality”, these scores are very high, however the community cannot be involved and uncertainties regarding efficiency are very high. Elevation scores decent in the social pillar, except for “neighbourhood and locality”, because it completely disturbs the neighbourhood for the period in which the soil will be elevated. Ultimately, the decision on which remediation method to implement is not within the scope of this paper. However, hopefully the involved parties can use the mutual relative scoring system and its specifications to decide which remediation method is most suitable for the Broekpolder, by which the governance system of the SES influences the other subsystems, who together produce ‘improved’ system-outcomes, and in this way more beneficially ecosystem services.

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Discussion

The uncertainties regarding specific remediation methods are for the most part already discussed by the “Uncertainty & Evidence” indicator in the analysis. However, additional comments with regard to this research will be elaborated on below:

The largest analytical problem lies within comparing and discussing three methods, which all have a high uncertainties when it comes to chance of success. On the one hand, although scientific literature on this method is lacking, elevation is a widely applied remediation method. From a great body of ‘grey knowledge’ we could assume that it is effective in preventing the spread of pollutants. However, it scores very poorly when it comes to environmental impact. On the other hand, methods like phyto- and bioremediation have high scores regarding their benefit to the environment, yet harbor great uncertainties when we look at project lifespan and environmental factors which might hamper the project.

While the project lifespan for bioremediation could not be determined, the time it will take to completely phytoremediate the broekpolder from the selected contaminants with the help from Brassica and Cucurbitaceae is between just over a month month to more than 2 millennia. Obviously, this is wildly unrealistic. Therefore, the assistance of other successful hyperaccumulators suitable for the Broekpolder should be considered to speed up the process for metals which Brassica remediates too slowly, such as corn for Pb (Cheng, Huang & Li, 2015) and Thlaspi Caerulescens for Zinc (Vázquez et al., 1994).

Considering elevation, it is unknown what type of soil is used for the elevation remediation method. Every type of soil has their own characteristics, for example clay retains water longer/better than sand (Rawls et al., 1991). This is also making it difficult to say what will happen to the groundwater level and the “groundwater & surface water” indicator as a whole.

Besides issues that certain methods carry along with them, the desires of involved stakeholders must also be taken into account with regard to decision-making (Appendix B). Different stakeholders will perceive the scores differently, as they value the indicators in various ways, based on their own interests. Staatsbosbeheer for example prefers immediate action, what results in probably lower valuation on the indicators of the social pillar, and a high valuation on the “project lifespan & flexibility” indicator (Appendix B4). The Broekpolder Federation has very contradicting interests, as they represent the citizens, thus puting higher values on the social indicators (Appendix B8). DCMR will likely prioritize the environmental indicators, with their interest in maintaining an optimal ecological functionality (Appendix B5), while the province of South-Holland manages the budget and will therefore probably weigh the economic pillar as more important, since this directly affects the budget (Appendix B1).

Finally, it is important to realize that the Broekpolder could actually contribute to scientific knowledge with regard to the discussed remediation methods. The area offers an extraordinary chance for in situ research, what is useful for the scientific domain, but also enhances the educational function of the Broekpolder with regard to its users. Section 7 for example, as one of the highest contaminated areas in the Broekpolder, could be made available to conduct such research (figure 2).

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CLEANING THE BROEKPOLDER: AN INTERDISCIPLINARY ASSESSMENT. SCORING DIFFERENT ENVIRONMENTAL REMEDIATION METHODS FOR THE BROEKPOLDER