A multi-stress model has been developed in the Netherlands on a national scale to forecast changes in plant species composition due to acidification, eutrophication and dessication. This model, called SMART-MOVE, consists of: a soil module (SMART2) used for calculating changes in groundwater level, pH and nutrient availability, and a vegetation module, consisting of regression equations that describe the relationships between the probability of occurrence and environmental factors. These environmental factors represent average Ellenberg indication values for pH, availability of water and nutrient availability. Salinity was also included since in large parts of the Netherlands salinity is of major importance for species composition. Essential input data for these modules, such as groundwater level and seepage flux, can be calculated with the National Groundwater Model, for example. In this study relationships were calculated between the Ellenberg indication values and the relevant soil factors: pH, average spring groundwater table, biomass production, nitrogen production, concentrations of several nutrients and chloride concentration for both terrestrial and aquatic systems. Where it was possible to use a sigmoid model, to cope with the original ordinal and limited scale of indication values, the explained variance increased by 5-10%. In the regression analyses, almost 7000 vegetation releves from a variety of ecosystems could be used, satisfying relationships with Ellenberg values were found for pH, average spring groundwater table and biomass and nitrogen production. These relationships are used to connect the soil module with the vegetation module and quantify the confidence of the model outcomes. Average Ellenberg indication values can be concluded to be succesful as estimates for the abiotic conditions in models like SMART-MOVE.

Analogous to the CSOIL model, which estimates human exposure to contaminated soils, an exposure model called SEDISOIL has been developed to quantify human exposure to sediments. When using this model it should be kept in mind that calculations are not very accurate, certainly when measurements in surface water and on fish have not been performed. SEDISOIL can be used for determinating the urgency of remediation in the case of seriously contaminated soils.

A preliminary investigation was conducted on the occurrence of particular pesticides in the soil. The aim was to gain insight into the appearance and behaviour of pesticides in soil from the plough layer in order to support the admission policy. Seven pesticides were chosen for determination on the basis of their accumulation properties and their market share. Four pesticides were found in the plough layer: atrazine, fenpropimorph, parathion and simazine. The amounts measured did hardly exceed the detection limit, with the exception of atrazine which showed relatively high levels for a number of plots, but also a decline in time. Paraquat, pencycuron and pirimicarb could not be detected in any of the plots. The measured amounts correspond reasonably well with the amounts calculated with the simulation model PESTLA.

The aim of this Programming Study on 'Behaviour of Accumulated Contaminants in relation to Land Use Changes and Recoverability of Ecosystems' was to determine: 1) the available knowledge and 2) the short-, medium- and long-term research, needed to develop a risk assessment for the effects of mobilisation of nutrients and contaminants due to land-use changes from agriculture to nature or forest conservation. The most relevant changes in soil condition, which can take place after afforestation, are concluded to be acidification and increase in dissolved organic carbon. The development of wetlands can lead to decreases in redoxpotential and acidification. These changes in soil condition can result in mobilisation of phosphate and heavy metals. Risks from organic micropollutants are probably lower ; however, as yet not much is known about this. Increased contaminant mobility can lead to a decrease in decomposition, an increase in internal concentrations of toxicants in soil fauna and secondary poisoning of terrestrial fauna. The study also concludes that risk assessment for land-use changes will require integration of existing models. A 'quick-and-dirty' model integration is recommended as a 1 to 2-year research programme, along with research on existing nature-development projects to be used as model systems for medium-term research programmes. For long-term research priority will be given to monitoring, process research and model integration.

The CSOIL exposure model was developed for derivation of ntervention Values for soil and groundwater clean-up. These Intervention Values are based on potential risks to humans exposed to soil contaminants. Theoretical evaluation of the CSOIL's volatilization module has shown to be not suitable for actual risk-assessment. For this reason, the VOLASOIL model has been developed for actual risk assessment in case of volatile soil contaminants. The VOLASOIL model calculates the indoor air concentration for the Dutch situation in buildings situated on soils contaminated with volatile compounds. The VOLASOIL model can be seen as an optimum between scientifically sound and applicable in practice. The model can be used for site-specific risk assessment because of the possibility of flexible combination of modelling and measurements and calculations being made for several specific contamination cases. Some of these are floating contaminant layers, pure contaminant in the open capillary zone, contaminated groundwater in crawl spaces, et cetera. The VOLASOIL model could be used as a decision-support tool within the framework of soil clean-up priority (Soil Protection Act), construction permit issues (Housing Act), and soil quality management (spatial planning). A user-friendly Windows-application has been developed for using the VOLASOIL model in practice. This computer program can be obtained at the RIVM.

EUPHIDS (EUropean Pesticide Hazard Information and Decision-support System) is the result of a research project carried out during 1993-1995 with the support of the Environment Research Programme (1990-1994) of the European Union. The system is meant to become an aid in the process of registering a plant-protection product (pesticide) in the European Union, including its Member States and their respective regions. The system is meant to fill the gap between the general criteria, set by the Uniform Principles which define the relevant targets and the general procedures of assessment, and the need for detailed methods and procedures for the quantitative risk assessment of each relevant target. EUPHIDS provides these methods, taking into account the specific environmental characteristics of areas. The risks to humans and the environment, expressed as ratio of exposure to (no) effect levels, are presented in maps. The structure of the system and the implementation of the main modules (leaching, run-off, spray-drift, and exposure of operators during application and exposure of the general population through diet) are complete, and at the moment several submodules are being developed. The system is, therefore, not fully operational. Data provided by the system describe study areas as well as toxicological and ecotoxicological characteristics of eight pesticides. In order to establish a fully operating system on all scales (continental, national, local) and for all pesticides, more pesticide data and geographical information have to be gathered. Besides the report the project has resulted in the production of a prototype of the system, which is available on floppy-disk, complete with user manual and technical description.

The distribution of calculated potential exposure due to soil contamination is quantified to gain insight into the reliability of the human exposure calculated with the CSOIL model. The study is focused on the distribution of exposure due to uncertainty in the input parameters caused by spatial variability and lack of information. A Monte Carlo-based sensitivity and uncertainty analysis is performed for this purpose using the UNCSAM computer package. Also investigated is the chance of occurrence of the deterministically calculated potential exposure underlying the intervention values, using the probability density function of the calculated potential exposure. Finally, the most important input parameters for the exposure distribution are derived for both potential and actual exposure. The study is focused on five contaminants, differing widely in their contaminant characteristics. The exposure via separate exposure routes is also evaluated so as to indicate the distribution of the exposure and contribution of the input parameters to exposure to other contaminants. To achieve this, other contaminants have to be characterised according to the contribution of these separate exposure routes to the total exposure. Because of large uncertainties in the calculation of the contents in the contact media (indoor air, plant content), for some contaminants one should consider performing measurements in these contact media. On the basis of probalistically derived exposure, Maximal Permissable Risk (MPR) for intake and ecotoxicological serious soil-contamination concentration (ECOTOX EBVC), it is recommended in the future to consider deriving probalistically based guidelines (e.g. intervention values) or other environmental quality objectives (e.g. final contaminant level after remediation).

Column experiments were carried out for the project "in situ bioremediation of an oil-polluted subsoil". The experiments were aimed at examining the possibility of remediating soil in situ with the help of microorganisms. The six undisturbed columns were filled at a location contaminated with petrol in Asten (the province of North Brabant). Different nutrients were applied to the columns to examine the effect on the activity of the microorganisms. From the results the petrol components can be shown to be eliminated from the soil by leaching and degradation carried out by microorganisms, the relative importance of the process depending on the additions. The columns were cleaned, first where the percolation water enters the column. Almost all the oxygen supplied was used in the columns. Aerobic conversions are concluded to have taken place. In column 5 a large amount of nitrogen was used in the column. Probably conversions under anaerobic conditions took place in this column due to the nitrate supply. It is not clear if this took place in the other columns. The lowest residues of petrol components were found in columns 3 and 4, in which hydrogen peroxide was supplied. Nevertheless, the largest amount of petrol was dissipated in column 5. Whether this is caused by anaerobic conversions during the first phase of the experiments or by recirculation during the second phase is not known. Good results were achieved in column 6, in which only the effluent was recirculated. The residues of petrol components in the lower part of the columns were below the detection limit in all columns, except column 1. Only in column 4 was this also found in the upper part. The best results were achieved in the columns in which hydrogen peroxide was supplied and in the columns where the effluent water was recirculated. Since the operation time in columns 4 and 5 was the longest, the results in these columns were better by comparison than columns 3 and 6, respectively. It is not certain, however, that the Dutch target values will be met in all columns. The research shows in situ bioremediation to be a promising technique for the remediation of soil with oil compounds. Further development of this technique through large-scale bioremediation is recommended.

Een van de uitgangspunten van het bodembeschermingsbeleid is het handhaven van de streefwaarde als maat voor duurzame bodemkwaliteit. Om een bodembelastingsmaat vast te stellen waarbij ook op lange termijn de streefwaarden niet worden overschreden is het begrip kritische bodembelasting ge-introduceerd. Op basis hiervan kunnen emissiereductiedoelstellingen worden berekend en prioriteiten gesteld worden voor de aanpak van verschillende bronnen van bodembelasting. De gevolgde methode is in een eerste rapportage "Kritische bodembelasting voor prioritaire stoffen ; afleiding en toepassing. Deel 1" uitgewerkt. In deel 2 zijn voor verschillende bron/stof combinaties emissiereductiepercentages berekend. Hiertoe is een selectie gemaakt van belangrijke bron/stof combinaties. Voor de onderzochte bron-stof combinaties zijn een aantal groepen te onderscheiden naar de mate waarin de interventiewaarde en de kritische bodembelasting overschreden worden in een periode van 100 jaar. Vooral de eerste en tweede groep situaties behoeven vanuit beleidsoogpunt aandacht. Voor de eerste groep situaties worden binnen 100 jaar de streefwaarden vrijwel zeker en mogelijk de interventiewaarden overschreden en zijn op basis van de kritische bodembelasting emissiereductiepercentages berekend van meer dan 90%. Binnen deze groep vallen: corrosie van zink ; lood langs autosnelwegen ; koper langs spoorwegen en ; de combinatie van corrosie van vangrails en autosnelwegen (Zn). Voor de tweede groep situaties wordt binnen 100 jaar een overschrijding van de streefwaarde verwacht en is een emissiereductiepercentage berekend van minimaal 10% (bij de minst sterke sorptie). Dit geldt voor de belasting door: atmosferische depositie van kwik en 1,1,1-trichloorethaan ; koper en kwik via meststoffen ; lood door baggerspecie ; uitloging van fenantreen en koper uit hout ; zink en fenantreen langs autosnelwegen ; en voor de gecombineerde situatie van meststoffen en baggerspecie (Cu, Zn, Hg, Pb). De gehanteerde methode kan een basis voor het bodembeschermingsbeleid vormen en de omvang van problemen inzichtelijk maken. Om tot een werkelijke reductie van de belasting te kunnen komen is het noodzakelijk voor bronnen met een bepaalde prioriteit de belastinggegevens te differentieren om de inzichtelijkheid te vergroten.<br>

Het belangrijkste doel van de uitgevoerde studie was om uit te vinden of multi- spectrale en multi-temporele classificatie van AVHRR-satelliet-gegevens een operationele methode op zou kunnen leveren om een pan-Europees landbedekkingsbestand op een schaal van 1 kilometer af te leiden. De classificatietechniek is toegepast op een groot gebied dat Frankrijk en buurgebieden omvat. De belangrijkste conclusies: besluitregels moeten ontwikkeld worden die zowel multi-temporele composieten als multi- spectrale gegevens benutten ; de huidige classificatiemethode laat alleen het afleiden van de belangrijkste landbedekkingsklassen toe ; vanwege het 'mengpixel'-probleem kan de inhoud van een AVHRR- landbedekkingsklasse substantieel verschillen door Europa heen ; de belangrijkste voordelen van een uit AVHRR afgeleid landbedekkingsbestand voor milieumonitoring op Europese schaal zijn het grote ruimtelijke detail en de consistente kwaliteit. Het belangrijkste nadeel is het ontbreken zoals specifieke klassen and permanente gewassen, welke laatste zeer belangrijk is voor de berekening van pesticide- belastingen van de grond.