Evaluation of models for metal partitioning and speciation in soils and their use in risk assessment

In this thesis models were developed and evaluated which describe metal partitioning and speciation in soils. Both partition-relations and multisurface models were developed and evaluated on their performance for a large set of element

Validation of transfer functions predicting Cd and Pb free metal ion activity in soil solution as a function of soil characteristics and reactive metal content.

According to recent insight, the toxicity of metals in soils is better related to the free metal ion (FMI) activity in the soil solution than to the total metal concentration in soil. However, the determination of FMI activities in soil solution is a difficult and time-consuming task. An alternative is to use empirical equations (so called transfer functions (TFs)) that relate FMI activity in solution to the reactive metal concentration in the solid phase and to soil properties (pH and organic matter content). Here we test the applicability of two sets of TF for Cd and Pb using independent data from a wide range of soil types and regions that are not represented in the datasets used to derive the TFs. From these soils, soil solution was extracted using four different methods. For all these extracts, FMI activities were calculated from total concentrations in solution using the speciation program WHAM VI. In some of the soils, Cd and Pb FMI activities were also measured using a Donnan membrane technique. Most of these FMI activities deviated from the TF predictions by less than one order of magnitude and were within the 95% confidence interval of the TFs, irrespective of the method used to extract soil solution. Predictability was higher for Pb than for Cd and differed also between the two TF sets

Simulation of phosphate leaching in catchments with phosphate-saturated soils in the Netherlands

The effects on phosphate leaching to surface waters of two scenarios for net phosphate input to sandy agricultural soils were estimated. WATBAL and ANIMO simulations for manure surplus areas in the Netherlands were used. The methodology and models were verified by comparing model results with measured values of the Schuitenbeek catchment. Simulated values of phosphate loads to surface waters and phosphate concentrations were underestimated by 10 and 30% respectively. Phosphate leaching to surface waters and phosphate concentrations hardly increase in the lower scenario with a net P2O5 input or `loss' of 10 kg per ha per year. With a P2O5 surplus of 40 kg per ha per year both leaching fluxes and concentrations increase

Critical loads and excess loads of cadmium, copper and lead for European forest soils

Recently, concern has arisen about the impact of the dispersion of heavy metals in Europe. Therefore, a study (ESQUAD) was initiated to assess critical loads and steady-state concentrations of cadmium, copper and lead for European forest soils. The calculation methods used strongly resemble those used to compute critical loads for acidifying compounds. Results show that the computed critical loads and associated excess loads for forest soils strongly depend on the threshold values chosen and on the soil phase (adsorbed/dissolved) considered. Further research is needed to improve input data and the modelling of heavy metal adsorption

Validation and application of soil acidification models at local, national and European scale; a compilation of articles on the models NuCSAM, ReSAM and SMART

An overview is given of three dynamic soil acidification models for application on different spatial scales. NUCSAM, the model for the local scale, was validated on data from two intensively monitored research sites. Results of annual average soil solution concentrations and fluxes calculated with the validated NUCSAM model agreed well with those of the national-scale model RESAM and to a lesser extent with those of the European-scale model SMART. Various deposition scenarios for SOx, NOx and NHx on soils were evaluated with the three acidification models

Critical loads of copper, nickel, zinc, arsenic, chromium and selenium for terrestrial ecosystems at a European scale; a preliminary assessment

This reports provides a preliminary assessment of critical loads of Cu,Ni,Zn,Cr, As and Se for Europe. Critical loads were computed according to existing methods, for forest soils and agricultural soils. Critical loads were assessed aiming at groundwater protection and for avoiding ecotoxilogical effects on soil organisms. Methods and input data for the models are described as well as critical limits used. Maps are provided showing the geographical distribution of 5 percentile critical loads for Europe for each metal and effect seperately. Results of the study are discussed in terms of geographical patterns and critical load ranges, and some indication of uncertainties and possible improvements of the applied methods and data is provided

SMASS - a simulation model of physical and chemical processes in acid sulphate soils; Version 2.1

The Simulation Model for Acid Sulphate Soils (SMASS) has been developed to predict the effects of water management strategies on acidification and de-acidification in areas with acid sulphate soils. It has submodels for solute transport, chemistry, oxygen transport and pyrite oxidation. The model must be used together with the water transport model SWACROP. It combines physical and chemical processes. The output includes the acidity and chemical quality of soil and groundwater, and the occurrence of toxic compounds. This user's manual presents an outline of input and output files, guidelines for installation on a VAX-VMS computer, and the description of an application

Risico-analyse van met chroom, arseen en zware metalen verontreinigde vloeivelden 'Zandleij' Tilburg; literatuur- en verkennend onderzoek

Om het risico op verspreiding en het ecotoxicologische risico van de chroom- en arseenverontreiniging van de vloeivelden `Zandleij' in Tilburg te bepalen is een literatuuronderzoek uitgevoerd naar de chemie en ecotoxicologie van beide elementen. De oxidatietoestand van chroom en arseen is van groot belang voor hun mobiliteit en toxiciteit. De oxidatietoestand hangt af van bodemeigenschappen zoals pH en organisch stofgehalte. In de delen met hoge concentraties Cr kunnen toxische effecten verwacht worden voor de bodemfauna. Dit is bevestigd met een verkennend experiment met regenwormen. Het effect op de vegetatie is waarschijnlijk gering. De kans op verspreiding is onder de huidige omstandigheden klein

Uitspoeling van zware metalen uit landbouwgronden; schatting van de bijdrage van uitspoeling uit landbouwgronden aan de belasting van het oppervlaktewater: modelaanpak en resultaten

Uitspoeling vanuit de bodem vormt mogelijk een belangrijke bijdrage aan de totale belasting van het oppervlaktewater met metalen. In een modelstudie is de uitspoeling op landelijke schaal gekwantificeerd middels een combinatie van een hydrologisch model en een bodemchemisch model. De totale bijdrage van uitspoeling op landelijke schaal aldus berekend varieert van 11% voor Pb tot bijna 50% voor Cd en Zn. Dit geeft aan dat de natuurlijke belasting vanuit de bodem voor de meer mobiele elementen als Cd en Zn significant bijdraagt aan de belasting van het oppervlaktewater. Mogelijk kan dit ook de verklaring vormen voor het voorkomen van verhoogde gehalten in het oppervlaktewater in niet specifiek belaste gebieden. Lokaal kunnen ook afwijkingen van Ni en Cu op deze wijze voor een deel verklaard worden