Bioavailability of chemicals in the environment has been the topic of scientific research for a number of years. Following up on requests from within the field of risk assessment and standard setting, the Stearing Group "Integral Standard Setting" (INS) asked for an advice on the future role of biological availability in standard setting and risk assessment. A workshop was organised in response to this request. In this report the main recommendations of the workshop are given. In addition, a number of policyrelated advises are incorporated, including an assessment of the time frames needed. The aim of the report is to review the utility of bioavailability-related research for standard setting and risk assessment and to put the expected applicability of the results of this research in a realistic time frame. It is foreseen that implementation of the topics with potential for future implementation in risk assessment or standard setting, will result in a more realistic risk assessment. The reliability of the present policy on chemical substances will benefit without defecting the environment. An active attitude from regulating bodies is essential for implementing the potentially favourable options and to stimulate researchers to focus their research activities on those topics that are most relevant from a policy making point of make. In addition to these general conclusions, detailed information on all options dealing with bioavailability of metals and organic substances in water, sediment and soil is given in the report.<br>

This report, representing the fourth in a series on a biological monitoring programme, describes the nematodes found in the mineral soil of 18 dairy-cattle farms located on grasslands with peat soils. These nematodes are also compared with the nematodes found on earlier sampled dairy-cattle farms on sandy soils. The farms had different numbers of cattle (mainly cows) per ha, leading to differences in the amounts of manure per ha which were supposed to be indicated by the concentrations of phosphate. The average number of nematodes found (9400 per 100 g soil ) comes very close to the number found on the extensive cattle farms on the sandy soils (10,000 per 100 g soil). The numbers of nematodes found in the intensive farms on sandy soils are higher (12,400 per 100 g soil), while those of the most intensive farms (6600 per 100 g soil) are lower. Increases in cattle intensity lead, on average, to the different farm types showing higher numbers of bacterivores and lower numbers of plantfeeders. The different indices, trophic diversity index T, maturity indices MI and Sigma MI, Shannon-Weaver index H', index of richness SR and the index of 'evenness' J', as well as the number of taxa N, are highest in the peat and sandy soils of the extensive farms, while lowest in the intensive farms. The number of nematodes from c-p group 1 (colonizers) increases with higher manure production.

The PEARL model is used to evaluate the leaching of pesticide to the groundwater in support to the Dutch and European pesticide registration procedures. PEARL is an acronym for Pesticide Emission Assessment at Regional and Local scales. The model is a joint product of Alterra Green World research and the National Institute of Public Health and the Environment, and it has replaced the models PESTLA and PESTRAS since June first, 2000. Model and data can be accessed through a user-friendly Graphical User Interface for Windows 95/98/NT. All data are stored in a relational database. Both the Dutch standard scenario and the European standard scenarios as suggested by the FOCUS modeling working group can be accessed through the User Interface. This report gives a description of the processes and parameters included in PEARL version 1.1. It also contains a description of the Pearl User Interface and the input and output files. The Dutch standard scenario is described briefly.

The Gorleben salt dome is considered as a potential disposal site for radioactive waste. In the safety assessment study, a number of pumping tests are carried out in the geohydrological system surrounding the salt dome. The Gorleben pumping test is simulated in a number of subsequent steps. In the first modelling step the analytical Theis solution is applied. Significant differences between the calculated and observed drawdowns show that the Theis solution assumptions are inappropriate to describe the Gorleben geohydrological system. In the second modelling attempt, the pumping test is simulated numerically with the METROPOL computer code. Geological borelog data and geohydrological profiles and maps are interpreted to obtain information on the aquifer geometry, anisotropy and possible heterogeneity. Under the assumptions of an anisotropic and heterogeneous geohydrological system, simulations of the Weisses Moor pumping test provide calculated drawdowns which match the observed drawdowns reasonably.

This report is one of the background reports of the evaluation report "MINAS en Milieu" It deals with the impact of fertiliser- and manure application in agriculture on the quality of soil (phosphrus) en groundwater (phosphorus/nitrogen). It is based on monitoring data carried out in the period 1984-2000. The report describes the actual status of quality standards with respect to nutrients. The agricultural soils in the Netherlands are in general phosphorus-rich. Nitrate concentrations in groundwater are high in shallow groundwater (in 2000 in sandy areas ca 125 mg/l: more than twice the standard value) but show a decrease since 1995, due to lower N-surpluses in dairy farming. At greater depths, concentrations are lower due to a combination of slow travel time, hydrology and decay (denitrification). In certain areas the abstracted groundwater for public water supply shows an increase of co-products of denitrifiaction e.g. sulphate, metals (nickel) and hardness.<br>

Four main natural resources can be distinguished: chemical elements, energy carriers, environmental resources (air, water, soil), and bioresources. Within bioresources can be distinguished: biomass (e.g. stock of wood or fish), and biodiversity. Biodiversity can be described in terms of genes, species or ecosystems. Although genetic variety is the most fundamental concept, species are mostly used as a more practical alternative. The Dutch environmental policy aims for the protection of 95% of the species. The Dutch policy for nature conservation selected "aim-species" on criteria as international rareness/distribution area, national rareness and declining trend. More attention should however be paid to: - the genetic information value per species (cladistic value), - the use of risk analysis. The motives of biodiversity consists of - financial or other utilitarian motives, - more spiritual or religious motives: . stewardship . esthetic, religious feelings of alliance with nature, . partnership (between man and nature based on mutual respect). The main functions are production, carrier, regulation and information. These functions can be subdived in at least 37 subfunctions. A summary of concrete and often monetised examples of functions is given to illustrate and underpin the importance of different functions. An overview of evaluation methods of biodiversity is given.

This report describes the results of a pilot study on the ammonia emission, deposition and critical load exceedances in the ROM area of south-east Friesland in the Netherlands. For this area an emission inventory was made describing the emission on a 1x1 km grid scale. A distinction was made between the emissions from stables and storage, application of manure and meadows. The stable emission of 300 (of a total of 1200) farms situated near areas sensitive to acidification was distinguished from the total stable emissions in the area. Deposition for the current situation (1993) averaged over the whole area, and for each nature area sensitive to acidification (>5 ha), was calculated using the OPS model. A distinction was made between the deposition due to emissions from foreign sources, the Dutch sources outside the ROM area, the sources within the area and the 300 farms. Critical load maps for nature areas, and for groundwater and surface water pollution, were derived from landuse data, species composition maps, the NLOAD model and critical load values for different ecosystems. Exceedances of the critical loads were estimated to determine the current environmental risk. Several scenarios were developed for the ammonia emissions in the area. The deposition and critical load exceedances were also determined for these scenarios. A pilot study on the optimization of emissions, given the critical deposition loads for nature areas, was also carried out. The results of this pilot study showed the optimization to be a good tool for determining future emission levels and spatial distributions to prevent exceedances of critical loads for all sensitive areas.<br>

The quality of environmental monitoring and forecasting on a European scale is influenced significantly by the accuracy of land use and land cover data. Due to an urgent need for a geo-referenced European Land Use (ELU) database the National Institute of Public Health and the Environment (RIVM) initiated the construction of a digital 10 minutes Pan-European land use database in 1994. This version distinguishes seven classes including arable land, grassland for agricultural use, permanent crops, forest and urban areas. The database consists of three parts, all in digital format: LuStat, LuGrid and LuVec. LuStat is a tabular database, containing land use statistics on NUTS-2 (regional, if available) or NUTS-1 (national) level. LuStat is compiled from various statistical sources. LuVec is a land use map in vector format which is compiled from all map sources. LuGrid is derived from LuVec and LuStat using a calibration routine. LuGrid consists of two parts: a 'pseudo grid' in vector format covering Pan-Europe, and an attribute table. The former consists of cells measuring 10 (geographical) minutes. This map is linked to the attribute table in which for all cells the distribution of the various land use classes is stored, as a percentage of the area of the entire cell. This report documents the enhancement which were made to the land use database. The result is a second version of the European Land Use database. ELU-2 was improved on a number of items when compared to ELU-1. In the course of 1994 and 1995, more statistical sources became available, as well as more spatial (map) data. The ELU-1 class forest was split into coniferous+mixed and deciduous forest. The calibration routine for matching statistical and map data, and assigning land use to the unit cells was improved. This allowed a better spatial distribution of the land use over the NUTS regions. The database was compared with a number of high-resolution land use and land cover databases at national level, and with a European-wide forest database. In general, ELU-2 compares well with these databases.

To evaluate, and indicate possible adjustment of, the current Dutch Intervention Values for cyanides (CN) a review has been made of sources of CN soil contamination, behaviour of CN species and present environmental concentrations related to soils contaminated before 1987. Knowledge on ecotoxicological effects of CN species in soils is insufficient to derive Intervention Values. Consequently these have to be based on human exposure. Consumption of crops is the major contributing factor to the current soil Intervention Values. Recent plant physiological studies indicate that soil contamination will not lead to CN concentration in crops which effect human health. Critical human exposure can occur via inhalation of free CN in ambient air, or after a one time peak ingestion by children of soil contaminated with complex CN. Therefore provisionally 25 ug/m3 HCN in soil air or in ambient air is suggested as a possible soil Intervention Value, equal to the Tolerable Concentration in Air. Further research is indicated to obtain a sound base for CN Intervention Values for soil. Consumption of untreated groundwater contaminated with ferrohexacyanide or thiocyanate can lead to critical exposure. For thiocyanate the Tolerable Daily Intake for children will be reached with 75 ug total CN per dm3, which may be proposed as an Intervention Value for groundwater.

The Hupselse beek catchment area is located in the sandy eastern part of the Netherlands. Its hydrological borders are well defined. Water, nitrogen, and phosphorus balances are calculated for the periode April 1985 to April 1994. Mean precipitation is 845 mm.a-1, actual evapotranspiration 515 mm.a-1, and discharge 330 mm.a-1. Discharge components are surface runoff (3% of total discharge), groundwater flow to tile drains (55-75%), and groundwater flow to ditches and the brook (20-40%). Roughly 40% of the water has a travel time in the soil of less than 1 year and more than 90% leaves the area within 5 years. Roughly 20% of the soil surface nitrogen load is transported by drainage, equal to 110 kg ha-1 a-1 N. The average concentration in brook discharge is 32 mg l-1. There is no trend in the nitrogen load during the period mentioned. The mean annual phosphorus load of the brook is 1 kg ha-1 a-1 P, resulting in an average concentration of 0.21 mg l-1 and corresponding to 1% of the soil surface load. The phosphorus load is decreasing with time during the period of investigation.