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.

To support the policy on preventive soil protection a measure to assess the emission to soil has been derived for sustaining soil quality on the basis of target values. This measure can be used to compare different sources of potential soil pollution and to derive directives for emission reduction. The study from which this measure is forthcoming is reported in two parts: Part 1 (report no. 715810015) is devoted to deriving a critical load for the unsaturated top layer of the soil and in part 2 (this report) the critical load is applied to the various combinations of soil, land use and emission sources. Emission reduction percentages were calculated for several combinations of sources and substances. It was concluded that a distinction could be made among a number of combinations as to levels of the critical load and target value exceedance in a 100 year period. Up to 90% emission reduction was calculated for the corrosion of zinc and lead along motorways, copper along railways and zinc in the combination of corrosion of guard-rails and motorways. In a 100-year period target values will certainly be exceeded and intervention values possibly. The method presented could form the base for soil protection policy insight into the extent of problems and for setting priorities. To define emission reduction with respect to priority combinations of sources and substances, further differentiation of specific loads and the loaded surface will be necessary.<br>

Estimates of emissions of pesticides from agricultural soils to the atmosphere and to the groundwater are needed. The most important processes determining the fate of pesticides are transformation, partitioning between the solid, liquid and gas phases, transport, and uptake by plant roots. The interaction between these processes is complex and non-linear. As these processes are functions of soil temperature and soil water status the use of a dynamic simulation model in prediction is indispensable. For this reason, the model PESTRAS has been developed. This model has been composed of existing models, i.e. the soil water transport submodel SWIF, the heat transport model HEATRAS, part of the pesticide leaching and accumulation model PESTLA, and the gas transport model GAS. This report comprises the incorporation of the model GAS and a partitioning point model into the PESTRAS model. A description is given of the model theory, the numerical scheme, and the model verification. Results are presented to show the sensitivity of the model to important input parameters, and the application of the model in a case study for 1,3-dichloropropene. The appendix contains a full manual of the programme. The model will be used on a routine basis for the generation of the annual reports 'State-of-the-Environment', published by RIVM. The model is also used in pesticide registration procedures. The incorporation of a gas transport submodel extends the scope of the model to volatile pesticides (Henry coefficient > 10 exp. -5 m3 m-3).

This report contains the results of the National Soil Monitoring Network of the Netherlands in 1994, the second year of sampling. The network represents a cooperative effort of the National Institute of Public Health and the Environment (RIVM), the Agriculture Economics Research Institute (LEI-DLO) and the Research Institute for Agrobiology and Soil Fertility (AB-DLO). The primary objective of the network is to identify changes in soil quality over time. The network's secondary objective is to identify the actual quality of soil and upper groundwater. Attention is focused primarily on rural areas. The monitoring program involves sampling 40 locations yearly over a period of five years. In 1993 the network started by sampling the soil and upper groundwater on 35 dairy-cattle farms in the sandy regions of the Netherlands. In 1994, 20 intensively managed cattle farms (i.e. farms with a high phosphate production) and 20 forest sites (deciduous, pine and mixed vegetation) on sandy soils were sampled. Concentrations of heavy metals, polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides and triazines in the topsoil (0-10 cm) and the litter layer of the forest sites have been reported. Concentrations of macroparameters, nutrients and heavy metals in the upper groundwater are also presented. The measured concentrations are compared with the Dutch objectives for soil and groundwater quality (target values).

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).<br>

This study represents a survey into whether mobilisation of heavy metals and nutrients can be a restrictive factor for the development of natural areas in the Beerze-Reusel basin. General risks of soil contamination for development of natural areas are first described, followed by calculations for determining risks for two specific soil types in the Beerze-Reusel basin, by means of coupling models on hydrology, acidification, heavy-metal behaviour and bioaccumulation. Considering the uncertainties in the methodology, this study has been explicitly restricted to a survey. Calculations on the risks of the combination of soil contamination (cadmium and copper), acidification (business-as-usual and an improved scenario) and (no) seepage for a meadow turned into a grassland ecosystem showed that ongoing acid atmospheric deposition in combination with soil contamination can lead to problems for the development of the grassland ecosystem. This happens both directly through acidification effects on vegetation and indirectly through effects of cadmium and copper on different species, and on biological functions of the soil. Effects on soil fauna can also lead to accumulation of organic matter, which can finally result in low species diversity. Copper generally caused less risks than cadmium, but due to ongoing increasing copper concentrations in litter and hence in soil fauna, long-term effects can occur. A scenario in which acid deposition was improved usually showed decreased risks for future ecosystems, but showed that this could also cause higher risks for a longer period due to slower leaching. A scenario comprising seepage up to 20 cm below surface showed hardly any differences in risks for development of natural areas.

Part one of the evaluation report gives a complete outline of the soil ecological research that was carried out between 1984 and 1993, by the section Terrestrial Ecology (LBG/RIVM). Practical research in the laboratory and field has been done, as a basis for general advisory tasks to support of the process of legislation for soil protection. For reasons of feasibility, the research was emphasized on the ecology and ecotoxicology of the free-living soil nematodes. Eighteen projects were carried out between 1984 and 1993. They can be grouped in 4 themes: 1) Ecological soil typology. 2). Effects of disturbance and pollution. 3) Ecological recovery. 4) biomonitoring. It was estimated that in total 46 'man-year' were invested in the nematode research program. Theme 2 was the main area of research (27 man-year). Further project management aspects are given in paragraph 3.6. The research resulted in 17 publications, 10 RIVM-reports and 22 student- reports. The development of the research was discussed with policymakers from the Soil Department. Comparison was made with former and recent need for knowledge of soil ecological processes. The nematode research itself was examined for its scientific value and innovation, collaboration network and future possibilities in new (and applied) soil biological studies.

No Observed Effect Concentrations of species or processes are used to derive statistical sensitivity distributions. Hazardous Concentrations (HC5 and HC50) derived from these distributions define the ecotoxicological risk limits. The project 'Validation of Toxicity Data and Risk Limits for Soils' was set up to evaluate the ecological relevance of (1) laboratory toxicity data and (2) ecotoxicological risk limits, and to identify which factors introduce uncertainties. Toxic effects of zinc and other metals were studied on selected species (Trifolium pratense, Folsomia candida, Enchytraeus crypticus, Eisenia andrei) and on microbial degradation activities. Differences in bioavailability between soil types were found to be of prime importance in laboratory-to-field extrapolation of toxicity data. Studies with mixtures suggested that each contaminant should be taken into account in risk assessment. Variable exposure conditions appeared to modulate toxicity moderately. Toxic effects of zinc on community endpoints were determined at an experimental field plot and a heavy-metal contaminated field site using enchytraeids, nematodes and micro-organisms. No or weak responses were found at the HC5 level, while measurable effects were present at the HC50 level. This was confirmed by data from the literature. The scientific underpinning of HC values may be improved if toxicity-modulating factors such as bioavailability are taken into account in the interpretation of laboratory toxicity data and if long-term effects of contaminants are focused on.<br>

In this literature survey to assess the accumulation of micropollutants in activities regulated by General Administrative Order (GAO) of the Dutch Soil Protection Act, seven GAOs were considered. The main aim was to determine by means of a critical load approach if the annual accumulation of micropollutants from activities regulated by the GAOs would cause exceedance of the Dutch target value within a 100-year period. A secundary aim was to evaluate this critical load approach, as described and used in earlier RIVM studies. In this approach, the actual annual loads to soil (kg.ha-1.yr-1) from activities mentioned above are compared with critical loads for micropollutants. Critical loads are calculated using a model called SOACAS and represent the annual loads which will prevent the target value for soil being exceeded for a defined time period. The annual input of micropollutants is compared with these critical loads. To avoid accumulation of micropollutants in groundwater, a critical load is introduced to protect the soil water. In conclusion, additional policy measures will have to be generated to avoid accumulation of micropollutants exceeding Dutch target values for soil and groundwater. Sharp emission reduction is especially necessary for copper and zinc from pig manure. Recommendations considered for advanced research, monitoring and policy have been proposed for each of the GAOs.