The report presents maps on soil protection areas in the Netherlands and gives more insight on different aspects of the environmental lity in these areas.

This report discusses the reliability of environmental indicators obtained from calculations, used by RIVM in the composition of reports on the state of the environment. The considered calculation chain (for the Netherlands) starts at the emission of nitrogen compounds in 1992 and ends with forecasts of the nitrate concentration in untreated water in 2100. To this end the notion of reliability is specified in terms of a reliability factor and a confidence interval. The structure of the chain is depicted with flow diagrams. It is composed of measurement data, registration data, model operations and GIS operations. The primary data with respect to the nitrogen load are obtained from sources outside RIVM. They are based on registrated data, for example agricultural surveys. For the nitrogen emissions a reliability was postulated. The applied RIVM models are respectively OPS (atmospheric transport), DEADM (atmospheric deposition), NLOAD (nitrate leaching from agricultural soils), BOSMODEL (nitrate leaching from forest soils and heathland) and FLOPZ1 (groundwater streamlines and residence times). The measurement data are obtained from the National Monitoring Networks for Air Quality (LML, wind velocities and NOy concentrations) and Groundwater Quality (LMG, nitrate concentration in deep groundwater). Applying uncertainty analyses on models and using statistical techniques, uncertainties in the various indicators are determined, where uncertainties are propagated through the chain. The reliability of the indicators, as reported for 1992, is calculated on the basis of the resulting uncertainties. Most of the calculations are performed on three different scales, 5 x 5 km blocks, Acidification Areas (20 areas in the Netherlands) and on national scale. The reliability of nitrate concentration in untreated water is assessed for two different drinking water stations. Results of the project are presented in the form of tables and graphics, such as histograms and geographical plots of indicators and reliability factors. Table 7.1 on page 73 summarizes the reliability of the investigated indicators. A subsequent goal of this report is to contribute to a (discussion about a) generally applicable method to determine the reliability in the calculation of environmental indicators.

The technical background to supporting the policy decisions on allocating phosphate-saturated soils and tackling the problems which these soils cause are presented here. Since 1987 the Dutch government has taken several steps to diminishing the problem of phosphate-saturated soils.New legislation will become available in 1998 for regulating the use of nutrients. The Ministries of Agriculture, Nature Management and Fisheries (LNV) and of Housing, Spatial Planning and the Environment (VROM) are planning to issue a general administrative order (GAO) to regulate phosphate use on phosphate-saturated soils. Several choices have to be made beforehand (1) Should the GAO cover the total agricultural area or should it be limited to, for example, the areas with known high historical loads? (2) What method should be used to identify phosphate-saturated soils? (3) Should management of all phosphate-saturated soils be restricted by the GAO or only the most polluted ones? (4) What level of net phosphorus export from the fields for which the GAO prescribes management restrictions should be implemented? Alternative answers to each of these questions have been formulated, with the pro's and cons for each given. Answers from the perspective of the GAO regulating farm management pertain to the national scale. The alternatives described can also be used for regulation limited to selected areas, such as those for nature conservation. In this case, methods described here can be used to select fields within the selected areas. In conclusion, several suggestions for future research are given, such as focusing on the effects in the long and medium term of soil phosphorus depletion on both agriculture and the environment. Although there are still questions to be answered, it has been made clear that the phosphorus status of most soils in the Netherlands at the moment is unnecessarily high from both the agricultural (plant production) and the environmental viewpoints.

The Natureplanner is essentially a computer system to predict the effects of environmental and spatial scenarios on nature for national and regional policy. It supports further the decisions on setting environmental standards, on detection of the dominant stress factor and the choice between area specific or general or mitigation measures and the costs. The smallest spatial resolution is 250*250 m. The dominant stress factor will be the most cost effective target for policy making; in some areas this will be desiccation and in others it may be eutrophication caused by deposition of NH3 from agriculture. The system has functions for viewing databases and maps of species distribution, soil or environmental scenario's. It is possible to choose a new vegetation structure in certain grid cells and than to compute the probability of occurrence of species under the given environmental conditions of soil, groundwater and acid or N-deposition. Another important application of the Nature Planner on a more regional scale is the computation of the specific critical N-load for a nature reserve. Further development is going on in close co-operation with other research institutes and some provinces with respect to: aquatic ecosystems, ecotoxicological aspects, succession/management practices, salinity, climate, and a separate module for effects of environmental changes and landscape fragmentation on birds and other fauna.

The aim of this study was to support the policy on preventive soil protection with information on the diffuse (non-local) emissions to soil and the influence on future soil quality. This study is related to inventories on (potential) sources of local soil pollution (e.g. industrial areas, landfills, oil-storage tanks, public sewerage systems, pipelines, roads and motorways, railways etc.). The diffuse sources included in this study are: atmospheric deposition, manure, fertilizer, pesticides, purifying sludge, compost, dredging sludge, corrosion of metals, leaching of preserved wood and hunting. The study focused on heavy metals, some pesticides, chlorinated hydrocarbons, chlorinated aromatic hydrocarbons, polycyclic aromatic hydrocarbons, aromatic hydrocarbons and oil(products). A survey was made on present and future soil quality. Four types of land use were distinguished: nature conservation areas/forest, agricultural land, infrastructural and urban areas. Conclusions have been made on (1) the contribution of the different sources to the total emissions to the soil and on (2) the expected exceedance of pollutant target values in soil affected by emissions. Important sources of non-local emissions to soil are atmospheric deposition, manure, fertilizer, dredging sludge, corrosion and leaching of impregnated wood. To guard the soil quality in the future, the emissions of cadmium, lead, copper, zinc, chromium, pesticides, trichloroethylene, chlorinated phenols and PAHs will have to decrease. The present emissions of arsenic, endosulfan, HCB, 1,1,1-trichloroethane and benzene to soil are probably acceptable. For many other substances little is known about the influence of the present load on future soil quality. Therefore more calculations to estimate the development of soil quality are recommended. Also actualization and differentiation of the emission data needs more attention.

The project 'Monitoring soil remediation policy results' represents a co-operative effort in the Netherlands of provinces (IPO), municipalities (VNG) and the Soil Directorate of the Ministry of Housing, Spatial Planning and the Environment (VROM) to develop a set of monitoring indicators. These would illustrate the extent of the soil pollution, the progress and costs of the soil cleanup actions, and the use of legal and financial policy instruments in line with the goals of National Environmental Policy Plan 3 and the Dutch Cabinet as standpoint on 'soil remediation in the Netherlands'. To structure future data collection, data were subdivided into periodical and historical data. The periodical data, to be collected annually (starting in the first year of the actual monitoring), cover all proposed indicators. The historical data, to be collected once for the preceding period, cover only some of the proposed indicators. The aim of this subproject, reported on by RIVM and Tauw Consulting Engineers, was to review the feasibility of the proposed indicators on the basis of availability and quality of the necessary data. Only the data in databases and archives of the soil remediation authorities (12 provinces and 4 major cities), and the Ministry of VROM were considered. A questionnaire on the availability and the quality of the necessary data was followed, after completion, by interviews with representatives of each targeted party. The results were assessed with a scoring method. The main conclusions on availability and quality of data for monitoring are summarized as follows: 1) necessary historical data are rarely completely available from databases and will require a search in the archives, while a collection of necessary periodical data for annual monitoring is more feasible; 2) the indicators for monitoring the progress of the soil cleanup are feasible when based on numbers of sites; 3) for collection of data on the polluted surface size, the volume of the polluted groundwater, the (average) costs of remedial action paid for by private funds and new cases of soil pollution (after 1986) will require a relatively large effort; 3) data for the the actual monitoring), cover all proposed indicators. The historical data, to be collected once for the preceding period, cover only some of the proposed indicators. The aim of this subproject, reported on by RIVM and Tauw Consulting Engineers, was to review the feasibility of the proposed indicators on the basis of availability and quality of the necessary data. Only the data in databases and archives of the soil remediation authorities (12 provinces and 4 major cities), and the Ministry of VROM were considered. A questionnaire on the availability interviews with representatives of each targeted party. The results were assessed with a scoring method. The main conclusions on availability and quality of data for monitoring are summarized as follows: 1) necessary historical data are rarely completely available from databases and will require a search in the archives, while a collection of necessary periodical data for annual monitoring is more feasible; 2) the indicators for monitoring the progress of the soil cleanup are feasible when based on numbers of sites; 3) for collection of data on the polluted surface size, the volume of the polluted groundwater, the (average) costs of remedial action paid for by private funds and new cases of soil pollution (after 1986) will require a relatively large effort; 3) data for the proposed indicator on social stagnation due to soil pollution are currently unregistered and consequently not available. In general, most indicators will be feasible, depending on how acceptable the effort is to find the historical missing data. The costs of the archive searches needed to complete all historical indicators are estimated at ca. 4 million Dutch guilders (1.8 million Euro). Results should be considered as preliminary; these will be used to compose the final list of indicators to be nationally implemented and to serve as an aid in defining the necessary efforts to implement the monitoring.

In the framework of the Dutch "Woningwet" (housing law) an approach is developed with the aim of assessing ecological risks of contaminated land. This approach is part of a more general decision support system, on which the assessment of soil quality in granting a building permit for a parcel will be based. Theoretical backgrounds of ecological risk assessment of contaminated sites are given. Within the context of the housing law there are very important limitations with respect to data availability and time available for decision making. This restricts very strongly the possibilities for ecological risk assessment of building parcels and forces to make a choice for a very pragmatic approach. Consequently, one is compelled to accept considerable sources of uncertainty. The proposed approach consists of three elements that are integrated in an assessment scheme. (1) The amount of pollution induced toxic stress on the ecosystem. This is estimated by adding pollution units of the individual contaminating chemicals. A pollution unit consists of the soil concentration of a chemical divided by its Hazardous Concentration 50% (HC50). (2) An estimate of exposure judged by the land-use type of the parcel. (3) An estimate of ecological accessibility based on the land-use in the neighbourhood of the parcel. The assessment scheme is based on the supposition that higher pollution induced stress is acceptable in situations with low chance of exposure and scarce ecological accessibility. Risk levels in this scheme should be given by policy makers because reliable technical and scientific arguments are lacking. Uncertainties of the proposed method are discussed and possibilities are given how improvements in reliability can be made.

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.

The impact of dispersion on the concentration of pesticide in the saturated groundwater was studied using scenario-type computer simulations for an area in the eastern part of the Netherlands (Lochem). The simulations demonstrated concentrations to decrease with depth; however, the rate of reduction is not systematic and varies throughout the area. On the boundaries between maize-land and grassland the reduction is considerable. In other parts of the area the reduction is limited and the concentrations gradually approach input concentrations, especially for long-term applications (i.e. > 10 years). The decrease in concentration by dispersion is based on the mixing of contaminated water with water from the surrounding areas. Therefore, the reduction for diffuse contamination or in cases where the load is maintained at a certain level for a long period of time, will be low. The most important effect of dispersion is the leveling out of peaks. The final rate of dilution depends highly on the situation in the surrounding area. Occurrence of dispersion itself is no guarantee that concentrations at a depth of 10 m will be reduced to below the threshold level, when they are above the threshold level in the uppermost groundwater.

This report describes a simple model for the calculation of accumulation of chemical substances in soils, SOACAS (Soil Accumulation Assessment). The model is based on a simple and specific analytical solution for the accumulation of chemicals in one completely mixed soil compartment. The model accounts for the distribution of chemicals between the gaseous, liquid and solid phase, as well as for plant uptake, volatilization, degradation and leaching. The method is applied for cadmium, chromium, copper, mercury, lead, zinc and benzo(a)pyreen for a number of combinations of soil type and land use. In view of the simplicity of the model it is not suitable for analysis of local soil pollution problems. It's prime goal of application is support of national and regional environmental policy. The model can easily be incorporated into a GIS environment. In this report an example is given in which the model is used to estimate the maximum permissible soil load, based on the present soil pollution status and the given standard for soil quality.