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Arsenic contamination of groundwater is a major public health concern worldwide. The problem has been reported mainly in southern Asia and, especially, in Bangladesh. Slow-sand filters (SSF) augmented with iron were proven to be a simple, low-cost and decentralized technique for the treatment of arsenic-contaminated sources. In this research, three pilot-scale SSF (flowrate 6 L·h−1) were tested regarding their capability of removing arsenic from groundwater in conditions similar to those found in countries like Bangladesh (70 µg As(III) L−1, 26 °C). From the three, two filters were prepared with mixed media, i.e., sand mixed with corrosive iron matter (CIM filter) and iron-coated sand (ICS filter), and a third conventional SSF was used as a reference. The results obtained showed that the CIM filter could remove arsenic below the World Health Organization (WHO) guideline concentration of 10 µg·L−1, even for inlet concentrations above 150 µg·L−1. After 230 days of continuous operation the arsenic concentration in the effluent started increasing, indicating depletion or saturation of the CIM layer. The effluent arsenic concentration, however, never exceeded the Bangladeshi standard of 50 µg·L−1 throughout the whole duration of the experiments.

Beschikbare reken- en informatiesystemen op het gebied van natuur- en landschap, humane effecten, blootstellingsroutes en kringlopen, waterverontreiniging, bodem- en grondwaterverontreiniging, luchtverontreiniging, stralingsbelasting, geluidsbelasting, afvalstoffen en continue emissies en calamiteuze emissies zijn geinventariseerd. Het rapport beoogt niet meer dan een overzicht te geven van binnen en buiten het RIVM beschikbare of in ontwikkeling zijnde systemen. De verkregen resultaten dienen mede als basis voor een thans bij het RIVM in uitvoering zijnde definitiestudie over integrale milieumodellering.

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Modelling and monitoring of Aquifer Thermal Energy Storage Impacts of heterogeneity, thermal interference and bioremediation Wijbrand Sommer PhD thesis, Wageningen University, Wageningen, NL (2015) ISBN 978-94-6257-294-2 Abstract Aquifer thermal energy storage (ATES) is applied world-wide to provide heating and cooling to buildings. Application of ATES, instead of traditional heating and cooling installations, reduces primary energy consumption and related CO2 emissions. Intensified use of the subsurface for thermal applications requires more accurate methods to measure and predict the development of thermal plumes in the subsurface related to thermal interference between systems and address issues concerning subsurface urban planning and wide spread presence of contaminants in urban groundwater systems. In this thesis, subsurface heat transport in ATES and the associated influence on storage performance for thermal energy was assessed. Detailed monitoring of subsurface temperature development around the wells of an existing system was achieved by a unique application of Distributed Temperature Sensing (DTS) using glass fibre optical cables. The measurements reveal unequal distribution of flow rate over different parts of the well screen and preferential flow due to aquifer heterogeneity. Heat transport modelling shows that heterogeneity causes preferential flow paths that can affect thermal interference between systems, mainly depending on well-to-well distance and hydrogeological conditions. At present, design rules are applied in such way that all negative interference is avoided. However, this limits the number of ATES systems that can be realized in a specific area, especially as these systems generally use only 60% of their permitted capacity. To optimize the use of available aquifer volume, the amount of thermal interference that is acceptable from an economical and environmental perspective was studied for different zonation patterns and well-to-well distances. Selecting the hydrogeological conditions of Amsterdam, the Netherlands, as a case study, this method shows that it is cost-effective to allow a limited amount of thermal interference, such that 30–40% more energy can be provided than compared to the case in which all negative thermal interference is avoided. Because many urbanized areas deal with contaminated soil and groundwater, ambitions to increase the number of ATES systems are confronted with the presence of groundwater contaminants. This is of concern, because groundwater movement induced by the ATES system can result in increased mobility and spreading of these contaminants. However, the combination between ATES and soil and groundwater remediation could be a promising integrated technique, both for improving groundwater quality and development of ATES. Opportunities to use ATES as a continuous biostimulation tool for enhanced reductive dechlorination (ERD) have been explored with a reactive transport model.

Sinds de jaren negentig wordt internationaal onderzoek verricht naar ‘duurzaam stortbeheer’. Het idee hierachter is dat de bron, de stortplaats zelf, schoner wordt, zodat er minder verontreinigingen uit de stortplaatsen kunnen weglekken. Op deze manier worden de bodem en het nabijgelegen grondwater beschermd. Tot nu toe zijn er nog geen technieken beschikbaar waarvan het effect op grote schaal bewezen is. In dat verband heeft het RIVM, in samenwerking met het Energieonderzoek Centrum Nederland (ECN), onderzoek gedaan voor drie vuilstortlocaties in Nederland. Voor deze locaties zijn ‘emissietoetswaarden’ afgeleid, waarmee kan worden vastgesteld hoeveel schadelijke stoffen er maximaal in het water afkomstig van de stortplaats mag zitten.

Modelling and monitoring of Aquifer Thermal Energy Storage Impacts of heterogeneity, thermal interference and bioremediation Wijbrand Sommer PhD thesis, Wageningen University, Wageningen, NL (2015) ISBN 978-94-6257-294-2 Abstract Aquifer thermal energy storage (ATES) is applied world-wide to provide heating and cooling to buildings. Application of ATES, instead of traditional heating and cooling installations, reduces primary energy consumption and related CO2 emissions. Intensified use of the subsurface for thermal applications requires more accurate methods to measure and predict the development of thermal plumes in the subsurface related to thermal interference between systems and address issues concerning subsurface urban planning and wide spread presence of contaminants in urban groundwater systems. In this thesis, subsurface heat transport in ATES and the associated influence on storage performance for thermal energy was assessed. Detailed monitoring of subsurface temperature development around the wells of an existing system was achieved by a unique application of Distributed Temperature Sensing (DTS) using glass fibre optical cables. The measurements reveal unequal distribution of flow rate over different parts of the well screen and preferential flow due to aquifer heterogeneity. Heat transport modelling shows that heterogeneity causes preferential flow paths that can affect thermal interference between systems, mainly depending on well-to-well distance and hydrogeological conditions. At present, design rules are applied in such way that all negative interference is avoided. However, this limits the number of ATES systems that can be realized in a specific area, especially as these systems generally use only 60% of their permitted capacity. To optimize the use of available aquifer volume, the amount of thermal interference that is acceptable from an economical and environmental perspective was studied for different zonation patterns and well-to-well distances. Selecting the hydrogeological conditions of Amsterdam, the Netherlands, as a case study, this method shows that it is cost-effective to allow a limited amount of thermal interference, such that 30–40% more energy can be provided than compared to the case in which all negative thermal interference is avoided. Because many urbanized areas deal with contaminated soil and groundwater, ambitions to increase the number of ATES systems are confronted with the presence of groundwater contaminants. This is of concern, because groundwater movement induced by the ATES system can result in increased mobility and spreading of these contaminants. However, the combination between ATES and soil and groundwater remediation could be a promising integrated technique, both for improving groundwater quality and development of ATES. Opportunities to use ATES as a continuous biostimulation tool for enhanced reductive dechlorination (ERD) have been explored with a reactive transport model.

Sinds de jaren negentig wordt internationaal onderzoek verricht naar ‘duurzaam stortbeheer’. Het idee hierachter is dat de bron, de stortplaats zelf, schoner wordt, zodat er minder verontreinigingen uit de stortplaatsen kunnen weglekken. Op deze manier worden de bodem en het nabijgelegen grondwater beschermd. Tot nu toe zijn er nog geen technieken beschikbaar waarvan het effect op grote schaal bewezen is. In dat verband heeft het RIVM, in samenwerking met het Energieonderzoek Centrum Nederland (ECN), onderzoek gedaan voor drie vuilstortlocaties in Nederland. Voor deze locaties zijn ‘emissietoetswaarden’ afgeleid, waarmee kan worden vastgesteld hoeveel schadelijke stoffen er maximaal in het water afkomstig van de stortplaats mag zitten.

Testing of pesticide leaching models is important to increase confidence in their use in pesticide registration procedures world-wide. The chromatographic PEARL model was tested against the results of a field leaching study on a cracking clay soil with a tracer (bromide), a mobile pesticide (bentazone) and a moderately sorbing, persistent pesticide (imidacloprid). Input parameters for water flow and solute transport were obtained from site-specific measurements and from literature. The model was tested using a stepwise approach in which each sub-model was sequentially and separately tested. Uncalibrated simulations for the water flow resulted in moisture profiles that were too wet. Calibration of the hydraulic relationships resulted in a good description of the moisture profiles. Calibration of the dispersion length was necessary to obtain a good description of bromide leaching. The calibrated dispersion length was 61 cm, which is very long and indicates a large non-uniformity of solute transport. The half-life of bentazone had to be calibrated to obtain a good description of its field persistence. The calibrated half-life was 2.5 times shorter than the half-life derived from the laboratory studies. Concentrations of bentazone in drain water and groundwater were described reasonably well by PEARL. Although measured and simulated persistence of imidacloprid in soil corresponded well, the bulk of the imidacloprid movement was overestimated by PEARL. However, imidacloprid concentrations in drain water were underestimated. In spite of the extensive calibration of water flow and tracer movement, the behaviour of the moderately sorbing pesticide imidacloprid could not be simulated. This indicates that the convection-dispersion equation cannot be used for accurate simulation of pesticide transport in cracking clay soils (even if extremely long dispersion length is used). Comparison of the model results from a poorly sorbed chemical (bentazone) and a moderately sorbed chemical (imidacloprid) were useful in defining the limitations of using a chromatographic flow model to simulate the effects of preferential flow.

A nutrient emission modelling system, called STONE, has been developed for the Netherlands. The approach of STONE and its use in evaluating environmental policies in the Netherlands are discussed. This specific approach is then compared with that of other nutrient emission modelling systems. Emphasis is put on both the scientific–technical aspects and on the applications in quantifying environmental effects of policy interventions at different scales. Results from STONE show, for example, the areas in the Netherlands where maximally acceptable nitrate concentrations in groundwater may be exceeded in the future, the effectiveness of implemented or intended policy measures on nutrient emissions, and the advantage of its mechanistic, spatially distributed approach. Such a detailed modelling approach is shown to be required to take into account the strong and complex interacting effects of, e.g. nutrient supply, groundwater level and management on nutrient emissions.

This paper summarises the results of both an ex-post evaluation of the Dutch Mineral Accounting System (MINAS) and an ex-ante evaluation of the effect of different levy-free surplus values. The MINAS system has been introduced in 1998 in order to reduce nitrate and phosphate leaching from agricultural soils. MINAS resulted in a reduction of the N surplus on dairy farms of approximately 50 kg ha-1 to limited or no costs to the farms involved. MINAS resulted in higher costs for manure removal for intensive livestock farmers. Though emissions of N and P have decreased significantly during the last five years effects of this reduction in environmental quality cannot be observed, except for a small decrease in nitrate concentration of the upper groundwater. The ex-ante evaluation of different variants for possible future levy-free surplus levels indicated that under the lowest variant, the nitrate concentration in groundwater will exceed 50 mg per litre on 14% of the area. The environmental effect of the different variants for P were not distinguished. The lowering of the levy-free surplus for P will have a drastic effect on the intensive livestock farms. The incorporation of fertiliser P under the MINAS system would be a cheap option to reduce the P surplusThis paper summarises the results of both an ex-post evaluation of the Dutch Mineral Accounting System (MINAS) and an ex-ante evaluation of the effect of different levy-free surplus values. The MINAS system has been introduced in 1998 in order to reduce nitrate and phosphate leaching from agricultural soils. MINAS resulted in a reduction of the N surplus on dairy farms of approximately 50 kg ha(-1) to limited or no costs to the farms involved. MINAS resulted in higher costs for manure removal for intensive livestock farmers. Though emissions of N and P have decreased significantly during the last five years effects of this reduction in environmental quality cannot be observed, except for a small decrease in nitrate concentration of the upper groundwater. The ex.-ante evaluation of different variants for possible future levy-free surplus levels indicated that under the lowest variant, the nitrate concentration in groundwater will exceed 50 mg per litre on 14% of the I area. The environmental effect of the different variants for P were not distinguished. The lowering of the levy-free surplus for P will have a drastic effect on the intensive livestock farms. The incorporation of fertiliser P under the MINAS system would be a cheap option to reduce the P surplus.

This study explores the effects of manure policy options for agricultural land in The Netherlands on nitrate leaching to groundwater, ammonia and nitrous oxide emissions to the atmosphere and on eutrophication of surface waters. The implementation of the farm gate balance MINAS at farm level, with levy-free N surpluses in the range of 300 to 40 kg per ha per year, and levy-free P surpluses in the range of 17.5 to 0.4 kg of P per ha per year, have been examined. Results indicate that nitrate concentrations in the upper groundwater are related to N surplus, land use, soil type and groundwater level. On dry sandy soils, the N surplus has to be below 60 to 140 kg of N per ha per year, depending on land use, to decrease the nitrate concentrations in the upper groundwater to below 50 mg nitrate per litre. Decreases of N and P concentrations in surface waters, upon lowering levy-free surpluses appear relatively small. For improving the ecological state of surface waters, we recommend a combination of low levy-free N and P surpluses with dredging P rich sediments, flushing of ditches, and decreasing discharges from other sources.

Effects of differences in both land use history and levels of nitrogen (N) application on nitrate concentration in the groundwater were studied for permanent pastures located on a single soil series in the Frisian Woodlands in the north of the Netherlands. The study was carried out for three fields: A, B and C. Field A was an old pasture, field B was a reseeded pasture and field C had been previously used for growing silage maize. The models SWAP and ANIMO were used for long-term simulations of the soil organic matter and soil N dynamics. The soil data from fields A, B and C were combined with different N application levels derived from commercial dairy farms on the same soil series for 2000. Soil organic matter and soil organic N were lower in field C than in fields A and B. In field C also the probability of exceeding the environmental threshold for nitrate in groundwater of 50 mg l−1 was lowest, which was ascribed to net immobilization irrespective of the high levels of N applied. However, this probability increased rapidly when the soil properties were similar to those of the old pasture (field A). Simulated levels of N uptake were higher for field A than for fields B and C at all levels of N applied. On old pasture, reducing N application levels can lower the probability of exceeding the environmental threshold for nitrate by up to 20% whilst hardly affecting N uptake.

Effects of differences in both land use history and levels of nitrogen (N) application on nitrate concentration in the groundwater were studied for permanent pastures located on a single soil series in the Frisian Woodlands in the north of the Netherlands. The study was carried out for three fields: A, B and C. Field A was an old pasture, field B was a reseeded pasture and field C had been previously used for growing silage maize. The models SWAP and ANIMO were used for long-term simulations of the soil organic matter and soil N dynamics. The soil data from fields A, B and C were combined with different N application levels derived from commercial dairy farms on the same soil series for 2000. Soil organic matter and soil organic N were lower in field C than in fields A and B. In field C also the probability of exceeding the environmental threshold for nitrate in groundwater of 50 mg l–1 was lowest, which was ascribed to net immobilization irrespective of the high levels of N applied. However, this probability increased rapidly when the soil properties were similar to those of the old pasture (field A). Simulated levels of N uptake were higher for field A than for fields B and C at all levels of N applied. On old pasture, reducing N application levels can lower the probability of exceeding the environmental threshold for nitrate by up to 20% whilst hardly affecting N uptake.

Agricultural nutrients can be a significant source of groundwater pollution. This paper studies the possible effects on farm management of a newly introduced policy instrument to control nitrogen and phosphorus pollution of groundwater bodies in The Netherlands. Ecological, technical, political, as well as financial issues, associated with the agricultural nutrient pollution problem, are considered. In response to the concern of the European Community (EC) for pollution of groundwater, The Netherlands implemented the Mineral Accounting System (MINAS), which focusses on nutrient (nitrogen and phosphorus flows) on individual farms, and taxes farms whose nutrient surplus exceeds a defined limit. To investigate the implications of MINAS for individual farm performance, financial and nutrient bookkeeping data of 194 farms, distributed over five farm types, were collected from 1997 through 1999. This paper shows that nutrient management performance of farmers varied largely between and within farm types, not only in absolute figures but also in terms of nutrient efficiency. The study also indicated that levies or taxes for excess nutrient surpluses could be high, ranging from 179 ha −1 for arable farmers to 404 ha −1 for mixed dairy and intensive livestock producers. These levies would reduce gross margin (GM) by 8% on average and can threaten continuity on an individual farm level. Therefore, current performance has to change considerably for farmers to be able to make the final surplus standards in 2003. Furthermore, as a consequence of objections of the EC to the Dutch policy, application standards for manure were introduced. This study showed that this does not prove to guarantee safe nutrient management as well as MINAS does, but will impact financial performance more, due to higher manure disposal costs.

Bij de bewaring van aardappelen wordt als kiemremmer de werkzame stof chloorprofam gebruikt. Na verwerking van de aardappelen in de fabriek blijft chloorprofam en haar omzettingsprodukt 3-chlooraniline in de resterende tarragrond aanwezig. De tarragrond wordt hergebruikt in grootschalige bodemtoepassingen. Omzetting, adsorptie en uitloging van chloorprofam en haar metaboliet 3-chlooraniline zijn onderzocht met tarragrond van aardappelen (onbelast en belast met chloorprofam) en met bouwvoorgrond. De omzettingssnelheid van chloorprofam en 3-chlooraniline is bepaald in bouwvoorgrond, in onverzadigde onbelaste tarragrond en in waterverzadigde onbelaste tarragrond. De adsorptieparameters van de Freundlich sorptie isotherm zijn bepaald voor 3-chlooraniline in onbelaste tarragrond en in bouwvoorgrond. De uitloogproeven zijn gedaan met onverzadigde belaste tarragrond en met waterverzadigde belaste tarragrond. De omzettingssnelheden en adsorptieparameters uit deze studie worden gebruikt voor het bepalen van het risico van uitspoeling van chloorprofam en 3-chlooraniline uit grote bodemtoepassingen naar het grondwater.

Bij de bewaring van aardappelen wordt als kiemremmer de werkzame stof chloorprofam gebruikt. Na verwerking van de aardappelen in de fabriek blijft chloorprofam en haar omzettingsprodukt 3-chlooraniline in de resterende tarragrond aanwezig. De tarragrond wordt hergebruikt in grootschalige bodemtoepassingen. Omzetting, adsorptie en uitloging van chloorprofam en haar metaboliet 3-chlooraniline zijn onderzocht met tarragrond van aardappelen (onbelast en belast met chloorprofam) en met bouwvoorgrond. De omzettingssnelheid van chloorprofam en 3-chlooraniline is bepaald in bouwvoorgrond, in onverzadigde onbelaste tarragrond en in waterverzadigde onbelaste tarragrond. De adsorptieparameters van de Freundlich sorptie isotherm zijn bepaald voor 3-chlooraniline in onbelaste tarragrond en in bouwvoorgrond. De uitloogproeven zijn gedaan met onverzadigde belaste tarragrond en met waterverzadigde belaste tarragrond. De omzettingssnelheden en adsorptieparameters uit deze studie worden gebruikt voor het bepalen van het risico van uitspoeling van chloorprofam en 3-chlooraniline uit grote bodemtoepassingen naar het grondwater.

The performance of in situ bioremediation to remove organic contaminants from contaminated aquifers depends on the physical and biochemical parameters. We characterize the performance by the contaminant removal rate and the region where biodegradation occurs, the biologically active zone (BAZ). The numerical fronts obtained by one-dimensional in situ bioremediation modeling reveal a traveling wave behavior: fronts of microbial mass, organic contaminant and electron acceptor move with a constant velocity and constant front shape through the domain. Hence, only one front shape and a linear relation between the front position and time is found for each of the three compounds. We derive analytical approximations for the traveling wave front shape and front position that agree perfectly with the traveling wave behavior resulting from the bioremediation model. Using these analytical approximations, we determine the contaminant removal rate and the BAZ. Furthermore, we assess the influence of the physical and biochemical parameters on the performance of the in situ bioremediation technique.

Air sparging in an aquifer below a less permeable horizontal layer is modeled using a two-phase flow approach. Supported by numerical simulations, we show that a steady state situation is reached. For an analysis of the steady state, we distinguish three different flow regimes, which occur between the well screen and the unsaturated zone. Just below the interface that separates the high and the low permeable layers a regime with almost hydrostatic capillary pressures develops. We use this observation to derive an ordinary differential equation for the pressure at the interface, which leads to an approximation of the air flow pattern just below and within the low permeable layer. The approximation provides an estimate for the radius of influence as a function of the physical parameters. The agreement between the analytical approximation and the numerical steady state results is almost perfect when heterogeneity is increased. With a few modifications the analysis applies also to a dense non-aqueous phase liquid (DNAPL) spill above a less permeable layer. Comparison with an illustrative numerical simulation shows that the analytical approximation provides a good estimate of the radial spreading of the DNAPL flow on top of and within the low permeable layer.

Voor een 3,5 jaar oude bufferstrook met gras langs een sloot op zandgrond zijn gedurende twee opeenvolgende uitspoelseizoenen de stikstofconcentraties in het bovenste grondwater regelmatig bemonsterd op diverse afstanden van de sloot. De stikstofconcentraties onder de bufferstrook waren significant lager dan onder de aangrenzende akker en namen in de richting van de sloot af. Deze verlaging is te wijten aan denitrificatie, hetgeen is aangetoond op basis van verandering in de verhouding chloride-nitraat én de natuurlijke variatie in 15N. In de bestudeerde periode bleek dat de nitraatconcentraties in het bovenste grondwater vaak boven de nitraatnorm uitkwamen. De bufferstrook zorgde dus niet voor een voldoende verlaging van de concentratie nitraat

In 2000 startten diverse onderzoeksinstellingen het project 'Sturen op Nitraat', waarin gezocht werd naar eenvoudig af te leiden indicatoren voor het monitoren van nitraatgehalten in het grondwater. Reden om hiernaar te zoeken was onder andere de zorg over de haalbaarheid van de milieukwaliteitsdoelstellingen voor oppervlakte- en grondwater die konden worden afgeleid uit de Nitraatrichtlijn. Aangescherpte MINAS-normen en het stelsel van mestafzetovereenkomsten leken met name voor de droge zandgronden niet ver genoeg te gaan. Een regionale aanpak met monitoring zou daarvoor een oplossing moeten bieden. Intussen is het einde van MINAS en mestafzetovereenkomsten in zicht. Maar met de komst van een nieuwe mestwetgeving is een regionale aanpak nog net zo actueel

Het LMM volgt sinds 1992 de landbouwpraktijk en waterkwaliteit op geselecteerde landbouwbedrijven in Nederland. Dit meetnet vervult twee functies: toetsing of het mestbeleid effectief is en invulling van zowel Europese als nationale monitorings-verplichtingen. In de afgelopen twintig jaar is de hoeveelheid stikstof en fosfaat (nutriënten) die via mest op het land is gebracht, grosso modo afgenomen. Als gevolg van het in 2006 aangescherpte mestbeleid versnelde deze daling. De afname is ook zichtbaar in de hoeveelheid nutriënten die uitspoelt naar de ondergrond of afspoelt naar het oppervlaktewater (bodemoverschot). Dit komt tot uiting in een daling van de nitraatconcentratie in het uitspoelingswater.

De Nationale Milieu Indicator NMI 3 is gebruikt om een overzicht te maken van de uitspoeling naar het grondwater door het gebruik van gewasbeschermingsmiddelen in het jaar 2008 in de Nederlandse land- en tuinbouw. Vrachten op jaarbasis zijn gegeven per werkzame stof en per gewas, voor het landbouwoppervlak ter hoogte van grondwaterlichamen, die in de Kaderrichtlijn Water worden onderscheiden. De meest uitspoelingsgevoelige stoffen worden momenteel toegepast als herbicide in de teelt van snijmaïs. Controle van de vrachten met een geavanceerd model heeft geleid tot een bevestiging dat de combinaties van stof en gewas op de juiste manier zijn gerangschikt.

Dit rapport beschrijft de opzet, evaluatie en resultaten van een modellering van uitloging van metalen en metalloïden uit bodems naar het grondwater. Deze studie had de volgende doelen: 1. het bepalen van representatieve concentraties van metalen en metalloïden in het ondiepe (eerste meter) grondwater; 2. het bepalen van representatieve waarden voor bodemparameters, die de uitloging van metalen en metalloïden bepalen, zoals reactiviteit van opgelost organische koolstof, gehalten aan oxiden en reactiviteit van metalen en metalloïden; 3. het verbeteren van het bestaande modelinstrumentarium voor het modelleren van de uitloging van metalen en metalloïden uit de bodem, inclusief de onzekerheid van deze modellen.

De Nationale Milieu Indicator NMI 3 is gebruikt om een overzicht te maken van de uitspoeling naar het grondwater door het gebruik van gewasbeschermingsmiddelen in het jaar 2008 in de Nederlandse land- en tuinbouw. Vrachten op jaarbasis zijn gegeven per werkzame stof en per gewas, voor het landbouwoppervlak ter hoogte van grondwaterlichamen, die in de Kaderrichtlijn Water worden onderscheiden. De meest uitspoelingsgevoelige stoffen worden momenteel toegepast als herbicide in de teelt van snijmaïs. Controle van de vrachten met een geavanceerd model heeft geleid tot een bevestiging dat de combinaties van stof en gewas op de juiste manier zijn gerangschikt.

The nitrate concentrations measured in drainage water and groundwater at LMM farms (farms participating in the National Manure Policy Effects Measurement Network (LLM)) in marine clay areas have decreased with 50% since the mid-nineties. The nitrate concentrations in marine clay areas are on average below 50 mg/L EU target value. A geographical analysis of the monitoring results shows, however, that the nitrate concentrations in 22% of the measurements, mainly taken in the south-western and central marine clay areas, exceed the EU target. The Ministry of Economic Affairs (EZ) commissioned a study to investigate the possible causes of the differences in nitrate concentrations between clay regions. This study shows that the differences in nitrate concentrations are largely due to the specific form of land use combined with the volume of seepage water occurring at LMM farms. This accounts for 43% to 62% of the variation in nitrate concentrations in samples taken from drain pipes at LMM farms from 2006 to 2008. Statistical analysis shows that the average nitrogen surplus of the soil balance of the LMM farms in marine clay areas does not explain the differences in measured (average) nitrate concentrations between these farms. However, the number of farms on clay soils of the LMM-dataset is limited (83 farms in total).

Het LMM volgt sinds 1992 de landbouwpraktijk en waterkwaliteit op geselecteerde landbouwbedrijven in Nederland. Dit meetnet vervult twee functies: toetsing of het mestbeleid effectief is en invulling van zowel Europese als nationale monitorings-verplichtingen. In de afgelopen twintig jaar is de hoeveelheid stikstof en fosfaat (nutriënten) die via mest op het land is gebracht, grosso modo afgenomen. Als gevolg van het in 2006 aangescherpte mestbeleid versnelde deze daling. De afname is ook zichtbaar in de hoeveelheid nutriënten die uitspoelt naar de ondergrond of afspoelt naar het oppervlaktewater (bodemoverschot). Dit komt tot uiting in een daling van de nitraatconcentratie in het uitspoelingswater.

Dit rapport beschrijft de opzet, evaluatie en resultaten van een modellering van uitloging van metalen en metalloïden uit bodems naar het grondwater. Deze studie had de volgende doelen: 1. het bepalen van representatieve concentraties van metalen en metalloïden in het ondiepe (eerste meter) grondwater; 2. het bepalen van representatieve waarden voor bodemparameters, die de uitloging van metalen en metalloïden bepalen, zoals reactiviteit van opgelost organische koolstof, gehalten aan oxiden en reactiviteit van metalen en metalloïden; 3. het verbeteren van het bestaande modelinstrumentarium voor het modelleren van de uitloging van metalen en metalloïden uit de bodem, inclusief de onzekerheid van deze modellen.

The nitrate concentrations measured in drainage water and groundwater at LMM farms (farms participating in the National Manure Policy Effects Measurement Network (LLM)) in marine clay areas have decreased with 50% since the mid-nineties. The nitrate concentrations in marine clay areas are on average below 50 mg/L EU target value. A geographical analysis of the monitoring results shows, however, that the nitrate concentrations in 22% of the measurements, mainly taken in the south-western and central marine clay areas, exceed the EU target. The Ministry of Economic Affairs (EZ) commissioned a study to investigate the possible causes of the differences in nitrate concentrations between clay regions. This study shows that the differences in nitrate concentrations are largely due to the specific form of land use combined with the volume of seepage water occurring at LMM farms. This accounts for 43% to 62% of the variation in nitrate concentrations in samples taken from drain pipes at LMM farms from 2006 to 2008. Statistical analysis shows that the average nitrogen surplus of the soil balance of the LMM farms in marine clay areas does not explain the differences in measured (average) nitrate concentrations between these farms. However, the number of farms on clay soils of the LMM-dataset is limited (83 farms in total).

Ondergrondse opberging wordt thans in het buitenland toegepast. De hoeveelheden afvalstoffen die voor berging in Nederland in aanmerking komen zijn geinventariseerd en er is een prognose voor de hoeveelheden omstreeks het jaar 2000 gemaakt. Minimaal zal dan een hoeveelheid van ruim een half miljoen ton/jr beschikbaar zijn. Ondergrondse opberging biedt een meervoudige barriere tegen verspreiding in de biosfeer. De scenario's die tot onverhoopt vrijkomen aanleiding kunnen geven zijn beschreven alsmede de consewuenties in globale zin. Uit indicatieve berekeingen blijkt dat zelfs na een waterinbreuk in de opbergmijn de verontreiniging zeer beperkt is.

Het sorptieproces alsmede de kinetiek van sorptie van chloorfenolen in natuurlijke en synthetische grondsoorten werd bestudeerd met behulp van laboratoriumexperimenten. Uit de resultaten bleek dat sorptie van chloorfenolen kan worden beschouwd als tweestapsproces. De eerste stap verloopt snel. De tweede stap verloopt langzaam. In kalkrijke gronden kan fenolaatsorptie van tetrachloor- en pentachloorfenol een rol spelen. Uit de resultaten blijkt dat potentiele mogelijkheden van uitspoeling van alle chloorfenolen aanwezig zijn bij kalkhoudende en humusarme gronden, zoals kleigrond, podzol en duinzand.