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There is ample experimental evidence that complications in water flow and pesticide transport can occur in cultivated humic-sandy and loamy-sandy soils. As a result, pesticide leaching to groundwater and water courses can be higher than expected. We made an inventory of mechanistic/deterministic model concepts that may be suitable for simulating preferential water flow and pesticide transport in these soils. The convection-dispersion approach, the mobile-stagnant concept, the dual-velocity concept, the explicit description of horizontal diffusion, the soil column approach and a concept of finger flow are discussed. Only for comparatively simple concepts it is feasible to ever obtain the parameter values. Ideally, the data sets to be used for testing the models concepts should be detailed and complete. Discrimination between the validity of the model concepts requires the variation in the measuring results to be limited. Testing of the model concepts under various representative field conditions is needed, to gain confidence in their results.

We tested the effects of the herbicide metsulfuron-methyl on growth of the submerged macrophyte Myriophyllum spicatum under laboratory conditions using different exposure scenarios. The exposures of each scenario were comparable in the concentration×time factor, viz., the same 21-d time-weighted average (TWA) concentrations but variable in peak exposure concentrations (ranging from 0.1 to 21000ngaiL(-1)) and exposure periods (1, 3, 7, 14 or 21d). To study recovery potential of the exposed M. spicatum plants we continued the observation on shoot and root growth for another 21d in herbicide-free medium so that the total observation period was 42d. Non-destructive endpoints, length and number of new shoots and roots, were determined weekly from day 14 onwards. Destructive endpoints, dry-weight (DW) of main shoots, new shoots and new roots, were measured at the end of the experiment (t=42d). Metsulfuron-methyl exposure in particular inhibited new tissue formation but was not lethal to main shoots. On days 21 and 42 after start exposure, EC(10)/EC(50) values for new tissues expressed in terms of peak concentration (=measured concentration during exposure periods of different length) showed large differences between exposure scenarios in contrast to EC(10)/EC(50) values for days 21 and 42 expressed in terms of 21-d and 42-d TWA concentrations, respectively. At the end of the experiment (day 42), 42-d TWA EC(x) values were remarkably similar between exposure scenarios, while a similar trend could already be observed on day 21 for 21-d TWA EC(x) values. For the macrophyte M. spicatum and exposure to the herbicide metsulfuron-methyl the TWA approach seems to be appropriate to use in the risk assessment. However, the data from the toxicity experiment suggest that on day 21 also the absolute height of the pulse exposure played a (minor) role in the exposure - response relationships observed

We study non-stationary flow in open discharge channels. A model is derived from basic principles, conservation of mass and momentum, which is solved numerically for the cross sectional area and discharge as a function of time and position along the channel. The model describes the effect of external inflow from fields adjacent to the channel. Several scenarios are calculated, both for very slowly, and more rapidly flowing water courses.

There is ample experimental evidence that complications in water flow and pesticide transport can occur in cultivated humic-sandy and loamy-sandy soils. As a result, pesticide leaching to groundwater and water courses can be higher than expected. We made an inventory of mechanistic/deterministic model concepts that may be suitable for simulating preferential water flow and pesticide transport in these soils. The convection-dispersion approach, the mobile-stagnant concept, the dual-velocity concept, the explicit description of horizontal diffusion, the soil column approach and a concept of finger flow are discussed. Only for comparatively simple concepts it is feasible to ever obtain the parameter values. Ideally, the data sets to be used for testing the models concepts should be detailed and complete. Discrimination between the validity of the model concepts requires the variation in the measuring results to be limited. Testing of the model concepts under various representative field conditions is needed, to gain confidence in their results.

The HAIR instrument calculates risk indicators related to the agricultural use of pesticides in EU Member States. HAIR combines databases and models for calculating potential environmental environmental effects expressed by the exposure toxicity ratio.

Van de verspreiding van boor- en prachtvliegen in Nederland is nog maar weinig bekend. In dit artikel worden waarnemingen van 17 soorten boorvliegen en drie soorten prachtvliegen behandeld. Het gaat hierbij of om zeldzame het gaat hierbij of om zeldzame soorten of om waarnemingen die een aanzienlijke uitbreiding van het areaal betreffen. Daarnaast wordt een nieuw overzicht gegeven van alle soorten prachtvliegen in Nederland met een verwijzing naar determinatieliteratuur.

Puntbronnen kunnen bijdragen aan emissies naar oppervlaktewater. Activiteiten op het erf die tot puntemissies kunnen leiden zijn vergeleken en gerangschikt. POSSUM (POint Sources SUrface waters Model) vergelijkt de risico’s van verschillende activiteiten op basis van gegevens over activiteiten en bedrijfssituaties; op basis van kennis omtrent depositie van reststromen met gewasbeschermingsmiddelen (in putten, op het erf of op de bodem), en de frequentie waarin verschillende activiteiten ten opzichte van elkaar worden uitgevoerd. De activiteiten worden vergeleken op bedrijfsniveau op de schaal van een bedrijf voor een periode van één jaar. De emissies in dit rapport zijn berekend op basis van gegevens die van 2006 tot 2008 verzameld zijn. Voor de akkerbouw is voor de werkzame stof terbutylazin de grootste emissie berekend voor het vullen van de spuittank. Voor de bloembollenteelt is voor de werkzame stoffen pirimifos-methyl en prochloraz de grootste emissie berekend bij het spoelen van geoogste bollen en het reinigen van kuubskisten. Voor de fruitteelt is voor de werkzame stof imidacloprid de berekende emissie het grootst bij het uitwendig reinigen van de spuitapparatuur.

The use of Pesticide Leaching Models (PLM) for risk assessment may be an efficient and attractive way of assessing solutions to some agricultural and environmental problems. Many countries of the European Union and the USA have been using PLM for risk assessment already for a few decades. This chapter has the aim to present a successful application of two PLM (i.e. MACRO and PEARL) in a Brazilian very intensive agricultural area to simulate moisture profiles and the leaching of a water flow tracer (i.e. bromide) and the pesticides cyproconazole and thiamethoxam. Also attempts to summarize the available knowledge about the processes governing pesticide behavior in soil, types and classifications of PLM, the use of PLM for risk assessment at European Union, a theoretical description of PEARL and MACRO models and their testing in a Brazilian agricultural field scenario.

Metingen van concentraties van gewasbeschermingsmiddelen in het Nederlandse oppervlaktewater worden met een geostatistische methode opgeschaald naar landelijke waarden. De methode maakt gebruik van ruimte-tijd regressie-kriging, waarbij zowel informatie in de metingen zelf als in landsdekkende kaarten van gecorreleerde omgevingsvariabelen wordt benut. De methode berekent eveneens de onzekerheid in de opgeschaalde waarde zodat ook de statistische significantie van temporele trends in landelijke waarden kan worden bepaald. Toepassing van de methode op metribuzin en carbendazim voor de periode 1997-2006 geeft plausibele resultaten die voor metribuzin in alle jaren rond 12 ng/liter liggen en voor carbendazim een dalende trend van 170 ng/liter in 1997 naar 100 ng/liter in 2006 laat zien. De methode is bewerkelijk en stelt hoge eisen aan de beschikbaarheid van data. Belangrijke aandachtspunten voor toekomstig onderzoek zijn statistische validatie van modeluitkomsten, analyse van de gevoeligheid van het model voor gemaakte aannames en de verbeterde verwerking van metingen beneden de kwantificeringslimiet. Trefwoorden: gewasbeschermingsmiddelen, kriging, milieu, regressie, statistische modellering, trend, waterkwaliteit

Het is inmiddels een bekend feit dat ontwormingsmiddelen die aan vee worden gegeven, giftig kunnen zijn voor de mestfauna, de insecten die zich met mest voeden en er hun eieren in leggen. Het verdwijnen van bepaalde soorten mestfauna kan er in bepaalde gevallen toe leiden dat de afbraak van mest in het veld vertraagd wordt, zo blijkt uit buitenlandse studies. Enquêtes wezen eerder uit dat ontwormingsmiddelen in veel Nederlandse natuurgebieden worden toegediend aan grote grazers. Komen dit soort ecologische effecten dus ook in onze natuurgebieden voor? Dit is de afgelopen jaren door Alterra onderzocht in opdracht van het ministerie van EL&I.

Metingen van concentraties van gewasbeschermingsmiddelen in het Nederlandse oppervlaktewater worden met een geostatistische methode opgeschaald naar landelijke waarden. De methode maakt gebruik van ruimte-tijd regressie-kriging, waarbij zowel informatie in de metingen zelf als in landsdekkende kaarten van gecorreleerde omgevingsvariabelen wordt benut. De methode berekent eveneens de onzekerheid in de opgeschaalde waarde zodat ook de statistische significantie van temporele trends in landelijke waarden kan worden bepaald. Toepassing van de methode op metribuzin en carbendazim voor de periode 1997-2006 geeft plausibele resultaten die voor metribuzin in alle jaren rond 12 ng/liter liggen en voor carbendazim een dalende trend van 170 ng/liter in 1997 naar 100 ng/liter in 2006 laat zien. De methode is bewerkelijk en stelt hoge eisen aan de beschikbaarheid van data. Belangrijke aandachtspunten voor toekomstig onderzoek zijn statistische validatie van modeluitkomsten, analyse van de gevoeligheid van het model voor gemaakte aannames en de verbeterde verwerking van metingen beneden de kwantificeringslimiet. Trefwoorden: gewasbeschermingsmiddelen, kriging, milieu, regressie, statistische modellering, trend, waterkwaliteit

The risk assessment of pesticides for freshwater ecosystems in the Amazon has relied on the use of toxicity data and water quality criteria derived for temperate regions due to a lack of ecotoxicological studies performed with indigenous species. This leaves an unknown margin of uncertainty for the protection of Amazonian ecosystems, as differences in environmental conditions and species sensitivity are not taken into account. To address this issue, the acute toxic effects of malathion (an organophosphorus insecticide) and carbendazim (a benzimidazole fungicide) were assessed on five fish and five freshwater invertebrates endemic to the Amazonian region. Subsequently, the intrinsic sensitivity of Amazonian and temperate freshwater species was compared using the species sensitivity distribution (SSD) concept. Amazonian species sensitivity to malathion was found to be similar to that of their temperate counterparts, with LC50 values ranging between 111 and 1507 g/l for fish species and 2.1426 g/l for arthropod species. However, Amazonian fish appeared to be slightly less sensitive for carbendazim than temperate fish with LC50 values ranging between 1648 and 4238 g/l, and Amazonian invertebrates were found to be significantly more resistant than their temperate counterparts, with LC50 values higher than 16000 g/l. The results of this study suggest that for these compounds, the use of water quality criteria derived with laboratory toxicity data for temperate species will result in a sufficient protection level for Amazonian freshwater organisms. Recommendations for further research include the validation of threshold concentrations derived with temperate standard test species and with the SSD model with semi-field experiments considering larger assemblages of indigenous species under local environmental conditions.

Environmental variables (including natural and anthropogenic stressors) and meiobenthic communities were sampled in a 'natural' (Rooiels) and a 'disturbed' (Lourens) estuary in the Western Cape, South Africa, bimonthly for 20 months. A primary aim of the study was to assess if the meiobenthic community structure is driven by different variables when comparing 'natural' versus 'disturbed' system. Due to the much smaller catchment of the Rooiels Estuary, many environmental variables were significantly different (p< 0.001) from the variables in the Lourens Estuary, e.g. salinity, temperature, pH, total suspended solids, nitrate and depth. No pesticide concentrations were expected in the Rooiels Estuary due to the absence of agricultural development in the catchment. However, chlorpyrifos (8.9 µg/kg), prothiofos (22.0 µg/kg) and cypermethrin concentrations (0.42 µg/kg) were detected frequently, with the highest concentrations recorded during the summer months. Principal response curve analysis showed that temporal variability between sampling dates explained 42% of the variance in environmental variables and pesticide concentrations and spatial variability between the 2 estuaries explained 58%. Variables contributing most to the differences were higher concentrations of endosulfan, p, p-DDE and nitrate concentrations in the Lourens Estuary and larger grain size and higher salinity at the bottom in the Rooiels Estuary. In general the meiofaunal community in the Rooiels Estuary showed a significantly higher number of taxa (p< 0.001), a significantly higher Shannon Wiener Diversity Index (p

It is now more than ten years ago that the Water Framework Directive (WFD) was adopted by the European Parliament. The main objectives of the WFD are (i) to achieve good ecological and chemical status for inland surface waters, transitional waters and coastal waters in EU Member States, (ii) to assess the ecological and chemical status of these water bodies by means of monitoring programmes, and (iii) to implement programmes of measures to reduce environmental stress to an acceptable level. By adopting the WFD a fundamental change in management objective was introduced in the European Union, from merely pollution control to ensuring ecosystem integrity as a whole [1]. The ecological status of WFD water bodies is assessed by monitoring of biological quality elements (e.g. fish, macroinvertebrates, macrophytes, benthic diatoms, phytoplankton), general chemical and physico-chemical quality elements (e.g. pH, alkalinity, nutrients) and hydromorphological quality elements. These quality elements monitored in water bodies are compared with the status of more or less pristine reference ecosystems. If in WFD water bodies the ecological status deviates too much from the reference condition action is needed for achieving the acceptable ecological status. The chemical status of water bodies is assessed by comparing chemical monitoring data with Environmental Quality Standards (EQS) for priority (hazardous) substances and other relevant substances. Currently, 41 priority (hazardous) substances are listed in the European Union, but a regular update of this list with emerging substances is anticipated. If in water bodies exposure concentrations of one or more of these priority (hazardous) substances are not in compliance with the officially published EQS’s for these pollutants a good chemical status is not reached and action is needed to improve this. In contrast to the EU-level priority (hazardous) substances the other relevant substances are river basin or Member State specific. These other relevant substances have been selected because they are believed to potentially impair the ecological status of specific WFD water bodies and/or related human health aspects. The methodology to derive the EQS’s for other relevant substances is similar to that of the priority (hazardous) substances. This methodology is described in the new Technical Guidance Document for deriving Environmental Quality Standards (will be officially released in 2011). In European river basins the priority (hazardous) substances and river specific pollutants have to be measured on a regular basis. Under the umbrella of the WFD, EQS derivation is primarily based on a single substance toxicity assessment approach. In exceptional cases EQS’s for mixtures may be derived when their qualitative and quantitative composition is well-defined and/or well described (e.g. biocide preparations, PCB’s, dioxins). The concentration addition (CA) concept is used as a default when setting EQS’s for mixtures. Although compliance with good chemical status is primarily based on EQS’s for individual substances, cumulative stress (including mixtures) of toxicants may be identified as a main pressure affecting ecological status. In that case the cumulative risks caused by pollutants have to be reduced.

As part of the ‘Surface Waters Decision Tree’ project a new authorisation procedure for plant protection products (PPPs) has been developed. The feedback of monitoring results in the authorisation procedure consists of 3 main steps: 1. Identification and ranking of problematic substances 2. Analysis of plausible causes 3. Feedback procedure In this report, a methodology for all three steps is described

BACKGROUND: For the registration of pesticides in the European Union, model simulations for worst-case scenarios are used to demonstrate that leaching concentrations to groundwater do not exceed a critical threshold. A worst-case scenario is a combination of soil and climate properties for which predicted leaching concentrations are higher than a certain percentile of the spatial concentration distribution within a region. The derivation of scenarios is complicated by uncertainty about soil and pesticide fate parameters. As the ranking of climate and soil property combinations according to predicted leaching concentrations is different for different pesticides, the worst-case scenario for one pesticide may misrepresent the worst case for another pesticide, which leads to ‘scenario uncertainty’. RESULTS: Pesticide fate parameter uncertainty led to higher concentrations in the higher percentiles of spatial concentration distributions, especially for distributions in smaller and more homogeneous regions. The effect of pesticide fate parameter uncertainty on the spatial concentration distribution was small when compared with the uncertainty of local concentration predictions and with the scenario uncertainty. CONCLUSION: Uncertainty in pesticide fate parameters and scenario uncertainty can be accounted for using higher percentiles of spatial concentration distributions and considering a range of pesticides for the scenario selection

We study non-stationary flow in open discharge channels. A model is derived from basic principles, conservation of mass and momentum, which is solved numerically for the cross sectional area and discharge as a function of time and position along the channel. The model describes the effect of external inflow from fields adjacent to the channel. Several scenarios are calculated, both for very slowly, and more rapidly flowing water courses.

It is now more than ten years ago that the Water Framework Directive (WFD) was adopted by the European Parliament. The main objectives of the WFD are (i) to achieve good ecological and chemical status for inland surface waters, transitional waters and coastal waters in EU Member States, (ii) to assess the ecological and chemical status of these water bodies by means of monitoring programmes, and (iii) to implement programmes of measures to reduce environmental stress to an acceptable level. By adopting the WFD a fundamental change in management objective was introduced in the European Union, from merely pollution control to ensuring ecosystem integrity as a whole [1]. The ecological status of WFD water bodies is assessed by monitoring of biological quality elements (e.g. fish, macroinvertebrates, macrophytes, benthic diatoms, phytoplankton), general chemical and physico-chemical quality elements (e.g. pH, alkalinity, nutrients) and hydromorphological quality elements. These quality elements monitored in water bodies are compared with the status of more or less pristine reference ecosystems. If in WFD water bodies the ecological status deviates too much from the reference condition action is needed for achieving the acceptable ecological status. The chemical status of water bodies is assessed by comparing chemical monitoring data with Environmental Quality Standards (EQS) for priority (hazardous) substances and other relevant substances. Currently, 41 priority (hazardous) substances are listed in the European Union, but a regular update of this list with emerging substances is anticipated. If in water bodies exposure concentrations of one or more of these priority (hazardous) substances are not in compliance with the officially published EQS’s for these pollutants a good chemical status is not reached and action is needed to improve this. In contrast to the EU-level priority (hazardous) substances the other relevant substances are river basin or Member State specific. These other relevant substances have been selected because they are believed to potentially impair the ecological status of specific WFD water bodies and/or related human health aspects. The methodology to derive the EQS’s for other relevant substances is similar to that of the priority (hazardous) substances. This methodology is described in the new Technical Guidance Document for deriving Environmental Quality Standards (will be officially released in 2011). In European river basins the priority (hazardous) substances and river specific pollutants have to be measured on a regular basis. Under the umbrella of the WFD, EQS derivation is primarily based on a single substance toxicity assessment approach. In exceptional cases EQS’s for mixtures may be derived when their qualitative and quantitative composition is well-defined and/or well described (e.g. biocide preparations, PCB’s, dioxins). The concentration addition (CA) concept is used as a default when setting EQS’s for mixtures. Although compliance with good chemical status is primarily based on EQS’s for individual substances, cumulative stress (including mixtures) of toxicants may be identified as a main pressure affecting ecological status. In that case the cumulative risks caused by pollutants have to be reduced.

Assessment of leaching of plant protection products to groundwater is an important aspect of the environmental risk assessment of these substances. Analysis of available Dutch groundwater monitoring data for these substances triggered a critical review of the current Dutch leaching assessment. As a result, proposals were developed for improving this assessment. These include: (i) a procedure for correcting systematic errors in measured sorption coefficients, (ii) a preliminary procedure for a quality check of Freundlich exponents, (iii) a flow chart for obtaining parameters describing the relationship between the organic-matter/water distribution coefficient, Kom, and the pH for weak acids, (iv) a procedure for obtaining an average Kom from a population of Kom values including lower and upper limits, (v) a procedure for estimating the total amount of substance in soil from a concentration profile (needed for assessment of degradation half-lives from field experiments). We recommend to test the feasibility of proposals to a few dossiers before implementing them in the leaching assesssment.

Recent advances in modeling the processes of the toxicity of chemicals-toxicokinetics (TK) and toxicodynamics (TD)-are improving environmental risk assessment (ERA) through prediction of effects from time-varying exposure. This has been achieved by linking chemical fate and toxicological effects mechanistically, based on internal concentrations, through the tissue residue approach. However, certain questions remain: for example, how do TK and TD differ among species and how does this relate to differences in species sensitivity? In a series of experiments, we studied the TK of [(14)C]chlorpyrifos in 15 freshwater arthropod species, two of which were studied in juvenile and adult life stages. Uptake (k(in)) and elimination (k(out)) rate constants were fitted using a one-compartment single first-order kinetic model. The application of two complementary parameter estimation methods facilitated the calculation of bioconcentration factors (BCF) with prediction intervals and 95% depuration times (t(95)) for all tested species. Extremely slow elimination was observed in some species as well as high overall variation in k(in), k(out), BCF, and t(95) across the tested aquatic arthropod species. This variation has implications for the development of TKTD approaches in ERA, including assessing fluctuating exposure concentrations and the interpretation of observed toxicity responses in the laboratory and in the field.

The problem of how to deal with species sensitivity differences to toxic substances has been addressed successfully with the species sensitivity distribution (SSD), yet this has not increased understanding about the underlying mechanisms of sensitivity. Other researchers have identified the mode of action of chemicals and also biological traits of species as determinants for sensitivity, yet no systematic approach combines these factors. To achieve this, first existing data on organophosphate, carbamate, and pyrethroid toxicity and mode of action and also species trait information were mined. Second, we linked taxon sensitivity to their traits at the family level to generate empirical and mechanistic hypotheses about sensitivity-trait relationships. In this way, a mode-specific sensitivity (MSS) ranking method was developed, and tested at the taxonomic level of family and genus. The application of several quality criteria indicated overall confidence in rankings, but confidence in exact taxon rank was less certain, due to data insufficiency for certain groups. The MSS rankings were found to be applicable for trait-based approaches and were successfully linked to existing trait data to identify traits with predictive potential. Although this empirical analysis cannot test causality relationships between traits and sensitivity, testable hypotheses were generated, for further experimental investigation. Single traits as well as combinations of traits can be used to predict laboratory sensitivity to the substances tested, although associations were not as strong as in previous studies. We conclude that existing trait data are not suitable for every trait-based research question and that important traits remain to be identified and quantified in relation to the processes of toxicity, i.e., the toxicokinetics and toxicodynamics.

Under typical agricultural use of an insecticide, it is likely that only part of an edge-of-field drainage ditch will be directly contaminated by spray drift. The response, including recovery, of aquatic macroinvertebrates in sprayed ditch sections may be affected by immigration of organisms from adjacent nonsprayed ditch sections, but also the population dynamics in nonsprayed sections (refuges) may be affected by nearby contaminated patches (known as action at a distance). Experimental ditches were used to study the influence of the presence of nearby refuges on the responses of macroinvertebrates in ditch sections directly sprayed with the insecticide lufenuron, and vice versa. The treatment regimes differed in the proportion of the ditch (0, 33, 67, and 100% of surface area) that was sprayed to reach a lufenuron concentration of 3 µg/L in the water column of the sprayed ditch section. In sprayed ditch sections, clear treatment-related effects were observed for adult midges in the emergence traps and for aquatic arthropods (mainly juveniles) in the artificial substrate/sweep net samples. The extent in magnitude and duration of effects in sprayed ditch sections was overall larger when a larger proportion of the ditch was sprayed and/or the distance to the refuge was larger. In nonsprayed ditch sections of partially treated ditches, treatment-related effects were absent or minor for macroinvertebrates that predominantly dwell on or in the sediment compartment, particularly at a larger distance from the sprayed ditch sections. More mobile arthropods that predominantly dwell in the water column showed clear treatment-related effects in the nonsprayed ditch sections as well, but action at a distance was smaller if a smaller proportion of ditch was treated. Environ. Toxicol. Chem. 2010;29:1994–2008. © 2010 SETAC

How much stress can one take? It depends, on the combination of your mental and physical characteristics (traits), but it’s hard to predict. Chemicals can have devastating effects on ecosystems and they can cause stress in animals and plants. Thus, their risk for ecosystem health needs to be assessed, before use. Species show very different tolerances to the diversity of chemicals due to the combination of both their traits and the molecular mechanism of causing damage in the cell. The challenge lies in finding the relevant species traits and their link to the chemical. In this project an insecticide and 15 freshwater species were used to develop and test a framework for the prediction of responses to stress using traits. Time dependent processes, such as exposure patterns, uptake and excretion of the chemical, but also compensation, detoxification and thresholds were investigated and modelled. These processes were successfully linked to several traits such as size, lipid content, breathing strategy, exoskeleton thickness and evolutionary descent.

In dit project werd gezocht naar zuiveringssystemen voor de verwerking van restwater die gemakkelijk op bedrijven zijn te implementeren. Daarbij is voor agrariërs belangrijk dat de systemen goedkoop en betrouwbaar zijn, met een minimum aan arbeid, maar hoog rendement.

Behavioural observations of the two female western lowland gorillas (Gorilla gorilla gorilla) composing an all-female group in Artis Royal Zoo (Amsterdam, the Netherlands) were evaluated. The two females had been observed for one-hr periods over a 166- day period, divided into a period before, and a period after the introduction of a new silverback male. Step intervention analysis showed that in both females locomotion and stereotypic behaviour significantly decreased after the introduction of the silverback. In one of the two females the public interaction also decreased significantly

The risk of leaching of agricultural pesticides from soil to groundwater and water courses has to be evaluated. Complications in water flow and pesticide transport in humic-sandy and loamy-sandy soil profiles can be expected to increase the risk of leaching. Much of the precipitation water is intercepted by the crop canopy, after which stemflow and leafdrip lead to peaks in water load at the soil surface. Water infiltration at the soil surface can be highly non-uniform, e.g. due to differences in soil structure, presence of micro-depressions and water-repellency. Water flow in the soil profile is affected by sedimentation pattern, soil forming processes, differences in soil structure, antecedent soil moisture content, etc. The heterogeneous transport of pesticides in soils is reflected by the wide range of concentrations measured at the various depths. The leaching of substances from sandy soil profiles can occur in 'hot spots', which indicates that there are preferential flow and transport paths. A special situation is presented by fields with ridges and furrows (e.g. used for growing potatoes), in which much of the precipitation water can infiltrate in the furrow soil. In view of the conditions inducing preferential pesticide transport in sandy soils, the possibilities to describe/predict this type of transport by modelling should be investigated further.

A reasonably accurate estimate of the water temperature is necessary for a good description of the degradation of plant protection products in water which is used in the surface water model TOXSWA. Based on a consideration of basic physical processes that describe the influence of weather on the energy balance of natural water bodies, we propose to extend TOXSWA with a 1D bulk approach to estimate water temperature. Evaluation of such a system confirmed that it is physically realistic and yet simple, with limited data requirements. It is expected to perform reasonably well in most conditions, and fits well into the present structure of the TOXSWA model. In particular the estimation of degradation rates in shallow and turbid water will benefit from introducing the proposed system.

Bayesian approaches are discussed throughout this book. Unfortunately, because frequentist methods are typically presented in introductory statistics courses, most environmental scientists do not clearly understand the basic premises of Bayesian methods. This lack of understanding could hamper appreciation for Bayesian approaches and delay the adaptation of these valuable methods for analyzing uncertainty in risk assessments.

Regime shifts in shallow lakes may significantly affect partitioning of sediment-bound hydrophobic organic chemicals (HOCs) such as polychlorobiphenyls (PCB) and polycyclic aromatic hydrocarbons (PAH). In replicated experimental model ecosystems mimicking the alternative stable states ‘macrophyte-dominated’ and ‘suspended solid – phytoplankton dominated’, we tested the effects of macrophytes and benthivorous fish presence on mass distribution and bioaccumulation of hexachlorobenzene, PCBs and PAHs. HOC mass distributions and lipid-normalized concentrations in sediment (Soxhlet- and 6-h Tenax-extractable), suspended solids, macrophytes, periphyton, algae, zooplankton, invertebrates and carp revealed that mobile, i.e. less hydrophobic or less aged HOCs were more susceptible to ecological changes than their sequestered native counterparts. Macrophytes were capable of depleting considerable percentages of the bioavailable, fast desorbing HOC fractions in the sediment upper (bioactive) layer, but did not have a significant diluting effect on lipid-normalized HOC concentrations in carp. Carp structured invertebrate communities through predation and stimulated partitioning of HOCs to other system compartments by resuspending the sediment. These results show that shifts in ecosystem structure have clear effects on fate, risks and natural attenuation of sediment-bound organic contaminants.

We study stationary flow in open discharge channels. A model is derived from basic principles, which is solved numerically for the water level and discharge as a function of position along the channel. The model describes the effect of external inflow from fields adjacent to the channel. Several scenarios are calculated, both for very slowly, and more rapidly flowing water courses.

The user-friendly shell DROPLET, acronym for DRinkwater uit OPpervlaktewater- Landbouwkundig gebruik Evaluatie Tool, assists the Dutch Board for the Authorisation of Plant Protection Products and Biocides (Ctgb) in evaluating whether pesticides may exceed the 0.1 μg/L standard in one of the Dutch surface water abstraction points for drinking water production. It operationalises the methodology developed by a Dutch expert group described in Adriaanse et al (2008). This manual explains how to use (i) SWASH to enter compound properties and application pattern, (ii) to run MACRO to calculate the drainage fluxes, (iii) to enter the deposition according to the Dutch Drift Table in TOXSWA, next (iv) to run TOXSWA to obtain an edge-of-field concentration in the FOCUS D3 ditch and finally (v) to run DROPLET to obtain the concentrations in the nine Dutch abstraction points plus the Bommelerwaard. DROPLET maintains a central database (in addition to the SWASH database) and combines the peak concentration of the FOCUS D3 ditch with intake area and compound specific factors, such as crop areas and compound degradation to calculate concentrations in the abstraction points.

De eenvoudigste manier om effecten van mengsels van bestrijdingsmiddelen te beoordelen is om de effecten van de individuele stoffen bij elkaar op te tellen (concentratieadditie). In het algemeen laten experimenten zien dat de stoffen elkaars werking niet versterken (geen synergisme). Als er toch sprake is van versterking, is dat effect doorgaans gering. Het concept concentratieadditie is daarom geschikt om de schadelijke effecten van mengsels van bestrijdingsmiddelen te schatten. Dit blijkt uit een overzicht van recente literatuur over de toxiciteit van mengsels van bestrijdingsmiddelen dat het RIVM met het kennisinstituut Alterra heeft gemaakt. De inventarisatie is een update van een analyse uit 2000 en bevestigt het beeld van toen. Het ministerie van VROM wilde als opdrachtgever in kaart brengen welke ontwikkelingen spelen op het gebied van het beoordelen van mengsels van bestrijdingsmiddelen. De studie beschrijft daarom ook methodologische vernieuwingen die de risicoschatting van mengsels kunnen verfijnen.

Tadpoles of two sister species of Ameerega are described. Tadpoles of Ameerega parvula can be distinguished from those of A. bilinguis based on slight differences in their oral disc structure and configuration of the tail fin. Both tadpoles have a tooth row formula 2/3 that is typical for many Ameerega, Epipedobates, and Allobates species. The two species differ in the relative length of the second lower tooth row (P-2). Ameerega parvula tadpoles have a slightly longer P-2 than P-1 row, whereas the P-2 row of A. bilinguis tadpoles is shorter than their P-1. The upper fin at midtail is slightly wider than the lower fin in A. parvula, whereas the lower fin is slightly wider than the upper fin in A. bilinguis tadpoles. Both tadpoles can be discriminated from those of sympatric species based on color and oral disc morphology. However, the oral disc morphology of Ameerega tadpoles provides no synapomorphic characteristics to distinguish Ameerega tadpoles from other dendrobatoid genera.