European scenarios for EUSES regional distribution model

The regional multimedia distribution model incorporated into EUSES 1.0 is used for the estimation of regionally predicted environmental concentrations in different European scenarios: a scenario representing a typical region in the north of Europe (high fraction connected to sewer systems, lower environmental temperature, high fractions of surface water and natural soil and a low fraction for agricultural soil) and another scenario representing a typical region in the south of Europe (low fraction connected to sewer systems, higher environmental temperature, low fractions for surface water and natural soil, and a high fraction for agricultural soil). The two scenarios are based on average data of countries in Northern and Southern Europe, but are not realistic for any specific country located in these regions. Scenario calculations were carried out using these two scenarios in addition to the generic standard region, given in EUSES 1.0 as a default scenario, and the North-Rhine Westphalian region. The substance properties, including emissions, were left unchanged for all scenarios. For a number of substances, the calculated concentrations in both the North and the South of Europe turned out to be higher than those calculated with the standard generic scenario. Thus, the standard scenario cannot be considered as a 'worst case' scenario per se. Uncertainties due to the regional heterogeneity within Europe are high. It is recommended to use these two additional scenarios for an improved estimation of possible concentration ranges in Europe.     

Aquatic fate assessment of the polycyclic musk fragrance HHCB. Scenario and variability analysis in accordance with the EU risk assessment guidelines

By means of the environmental fate and distribution models laid down in the Technical Guidance Documents (TGD) and implemented in the European Union System for the Evaluation of Substances (EUSES) environmental concentrations of the polycyclic musk fragrance HHCB (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethyl-cyclopenta-[g]-2- benzopyrane; trade name: e.g. Galaxolide) were calculated for the aquatic environment under consideration of various scenarios. The results were then compared to monitoring data from the region of North Rhine-Westphalia (River Ruhr). An uncertainty analysis was carried out to determine sensitive parameters, to integrate environmental variability and to confirm the model's calculations. The standard scenario of EUSES overestimates the measured concentrations, which confirms the conservative nature of the calculations. The regional-specific scenarios lead to lower deviations from the measured values than the standard scenario. Deviations range from one to two orders of magnitude in the effluent of sewage treatment plants; they amount to one order of magnitude for surface water concentrations on a local scale and conform to monitoring data on a regional scale. The use of measured bioconcentration factors for fish instead of estimated ones reduces deviations remarkably. The investigation reveals that unrealistic worst-case calculations of HHCB can at best be ameliorated by the application of more realistic emission rates and measured bioconcentration factors. The use of regional-specific parameters also diminishes the deviations of the calculations from the measured concentrations.     

Prognosis of environmental concentrations by geo-referenced and generic models: a comparison of GREAT-ER and EUSES exposure simulations for some consumer-product ingredients in the Itter

The aim of this study was the comparison between predicted environmental concentrations (PEC) derived using a generic aspacial model, European Union System for the Evaluation of Substances (EUSES), and a geo-referenced model, the Geo-referenced Regional Environmental Assessment Tool for European Rivers (GREAT-ER). The PECs of some consumer-product ingredients (boron, LAS) and professional uses (EDTA, NTA and Triclosan) were calculated for the river catchment of the Itter, a small tributary to the river Rhine. The PEClocal and PECregional for the water compartment generated by EUSES (default scenario) were subsequently refined with data that realistically reflects the region of North Rhine-Westphalia (NRW scenario) and the Itter catchment (Itter scenario). The results of the three scenarios were then compared with the PECinitial and PECcatchment calculated by GREAT-ER, that was designed as a higher-tiered exposure assessment tool, and with concrete concentrations in the Itter, measured as 24-h composite samples. While the PECregional of all scenarios was close to the lower end of the measured concentrations, the geo-referenced PECs described equally well the real spacial situation. The measured environmental concentrations confirmed the built-in conservatism of the PEClocal calculations by EUSES showing for all investigated chemicals an unrealistically high PEClocal (default). The refinement in the more realistic scenarios could not provide a straight forward general improvement of the PEClocal. In conclusion, when the EUSES prognosis is refined using more detailed substance and regional specific data, it may provide a fairly accurate modelling especially of substances that are not eliminated in the environment. However, in the case of eliminable substances, it does not match the accuracy of higher-tiered geo-referenced exposure models like GREAT-ER.     

BETR-World: a geographically explicit model of chemical fate: application to transport of alpha-HCH to the Arctic

The Berkeley-Trent (BETR)-World model, a 25 compartment, geographically explicit fugacity-based model is described and applied to evaluate the transport of chemicals from temperate source regions to receptor regions (such as the Arctic). The model was parameterized using GIS and an array of digital data on weather, oceans, freshwater, vegetation and geo-political boundaries. This version of the BETR model framework includes modification of atmospheric degradation rates by seasonally variable hydroxyl radical concentrations and temperature. Degradation rates in all other compartments vary with seasonally changing temperature. Deposition to the deep ocean has been included as a loss mechanism. A case study was undertaken for alpha-HCH. Dynamic emission scenarios were estimated for each of the 25 regions. Predicted environmental concentrations showed good agreement with measured values for the northern regions in air, and fresh and oceanic water and with the results from a previous model of global chemical fate. Potential for long-range transport and deposition to the Arctic region was assessed using a Transfer Efficiency combined with estimated emissions. European regions and the Orient including China have a high potential to contribute alpha-HCH contamination in the Arctic due to high rates of emission in these regions despite low Transfer Efficiencies. Sensitivity analyses reveal that the performance and reliability of the model is strongly influenced by parameters controlling degradation rates.     

Evaluation and comparison of multimedia mass balance models of chemical fate: application of EUSES and ChemCAN to 68 chemicals in Japan

The European Union System for Evaluation of Substances (EUSES) and the ChemCAN chemical fate model are applied to describe the fate of 68 chemicals on two spatial scales in Japan. Emission information on the chemicals has been obtained from Japan's Pollutant Release and Transfer Registry and available monitoring data gathered from government reports. Environmental concentrations calculated by the two models for the four primary environmental media of air, water, soil and sediment agree within a factor of 3 for over 70% of the data, and within a factor of 10 for over 87% of the data. Reasons for certain large discrepancies are discussed. Concentrations calculated by the models are generally consistent with the lower range of concentrations that are observed in the environment. Agreement between modeled and observed concentrations is considerably improved by including an estimate of the advective input of chemicals in air from outside Japan. The agreement between the EUSES and ChemCAN models suggests that results of individual chemical assessments are not likely to be significantly affected by the choice of chemical fate model. Primary sources of discrepancy between modeled and observed concentrations are believed to be uncertainties in emission rates, degradation half-lives, and the lack of data on advective inflow of contaminants in air.     

A rule-based screening environmental risk assessment tool derived from EUSES

Within the context and scope of the forthcoming European Union chemical regulations (REACH), there is a need to be able to prioritise the chemicals for evaluation. Therefore, a simple, pragmatic and adequately conservative approach for the identification of substances of very low or no immediate concern at an early stage is presented. The fundamental principles and basic concepts are derived from the EU Technical Guidance Document and EUSES, and are translated into an easy-to-use rule-based system. For this development, the effect on risk characterisation ratios (RCRs) of the key environmental parameters in EUSES was quantified (taking into account several standardised chemical release scenarios). Using statistical analysis, ranges were identified for each key parameter, within which the end result of the assessment was not significantly affected. This information was then translated into a lookup table from which environmental risk characterisation ratios can be directly read as a function of a few parameters.     

Development of a Dynamic Aquatic Model (DynA Model): Estimating Temporal Emissions of DDT to Lake Maggiore (N. Italy)

- DOI: http://dx.doi.org/10.1065/espr2006.01.009 Background, Aims and Scope Most existing models used to describe the fate of chemicals in surface water and sediment generally consider a 'static scenario', in which a contaminant is discharged at a constant rate and environmental input parameters do not change during the simulation time. This approach is not suitable in environmental scenarios characterized by daily or periodic changes of several input parameters. The aim of this study is to estimate approximate emissions of DDT lo Lake Maggiore using a new surface water model, (DynA Model) that describes the fate of a chemical in a dynamic scenario. Methods The model is developed on the grounds of an existing and validated model (QWASI). A numerical solution was adopted to build the fully dynamic version of the model. Results and Discussion The model was applied to Lake Maggiore emitting DDT at a constant rate until steady-state was reached. Emissions were stopped and later sporadic 'pulse' emissions were added. This was done to calculate the amount of DDT needed to simulate concentrations close to those measured in water and sediments. This allowed the evaluation of the order of magnitude of emissions. An uncertainty analysis for sediment resuspension was also performed, given the lack of measured resuspension rates. Conclusion The model showed the time response of the Lake Maggiore system to varying emission scenarios and provided what are regarded as reasonable estimates of DDT emissions. The model demonstrated the importance of sediment-water exchange. Recommendation and Outlook In order to better calculate DDT concentrations the model should be run with different discharge scenarios to clarify the time trends of concentrations, possibly with the use of different sets of measured data (such as biota and sediment deposition/resuspension rates).     

Visualisation of the complexity of EUSES

The interdependencies of parameters applied in the models of EUSES are visualised in a directed connectivity graph. The parameters (inputs, defaults, state variables, outputs) are represented by boxes (nodes) and their relations by lines (edges). The visualisation, on the one hand, clarifies the complexity of the models in EUSES and, on the other hand, creates an overview and transparency. The parameters’ relations to each other can be recognised faster, and the models can be better understood. The complexity was quantified by the number (variety), kind (substance parameter, physico-chemical parameter, concentration, other parameters), and depth (dimension) of the parameter and the number of relations (connectivity). The variety of EUSES (without the modelsSimple Treat andSimple Box whose interior structure is not documented and without the effect and risk characterisation) amounts to 466, the connectivity to 961, and the maximal dimension is 21.     

Calculation of environmental concentration and comparison of output for existing chemicals using regional multimedia modeling

The environmental fate of 40 existing chemicals is discussed using the EUSES multimedia distribution and risk assessment model with site-specific parameter setting in an urban area of Japan including a highly industrial region. There has been a strong need to assess the environmental fate of a huge number of existing chemicals. Data on the emission amounts of chemicals are essential for such prediction, and PRTR surveys may yield this data. The study delivered the following results: (1) Volatile compounds with large amounts of emission showed higher predicted concentrations in air, and the concentrations of several compounds agreed well with averaged monitoring data within an order of magnitude. (2) A close relationship was found between the concentration of water and that of sediment, suggesting that the fate of chemicals in sediment essentially depended on the water environment. (3) A group of volatile solvents had high mass distribution ratio to air. Some compounds having high solubility in water were also included in that group due to the high ratio of air emission. Highly hydrophobic compounds with logK(OW) larger than 6.0 showed a high distribution ratio to soil and sediment. (4) Volatile compounds were mostly taken through air. The exposure through fish is a dominant pathway for highly hydrophobic compounds. (5) Exposure ratio could be gathered from physicochemical properties. The exposure from fish intake was roughly estimated by logK(OW), whereas exposure from air and water intake was difficult to estimate simply by vapor pressure and solubility in water, respectively.     

Differentiation of nitrous oxide emission factors for agricultural soils

Nitrous oxide (N₂O) direct soil emissions from agriculture are often estimated using the default IPCC emission factor (EF) of 1%. However, a large variation in EFs exists due to differences in environment, crops and management. We developed an approach to determine N₂O EFs that depend on N-input sources and environmental factors. The starting point of the method was a monitoring study in which an EF of 1% was found. The conditions of this experiment were set as the reference from which the effects of 16 sources of N input, three soil types, two land-use types and annual precipitation on the N₂O EF were estimated. The derived EF inference scheme performed on average better than the default IPCC EF. The use of differentiated EFs, including different regional conditions, allows accounting for the effects of more mitigation measures and offers European countries a possibility to use a Tier 2 approach.     

Scientific activities of Euro Chlor in monitoring and assessing naturally and man-made organohalogens

In this paper a review of the scientific activities and research programmes carried out by Euro Chlor, the European Federation of chlor-alkali producers is presented according to two main axes: marine risk assessments with statistical analysis of monitoring data, temporal trends of emission levels and environmental concentrations. The methodology applied in each field is briefly presented and then illustrated by several practical examples. As a large part of the uncertainties in assessing the risk of a chemical to a given species or ecosystem often comes from the difficulty in evaluating the exposure level, Euro Chlor has chosen to use a monitoring approach, the exposure level being estimated from a statistical analysis of measured concentrations levels in water and sediment from rivers, estuaries and coastal areas. As the modelling approach often used by the authorities to estimate the predicted environmental concentration value is starting from roughly estimated emission levels, Euro Chlor collated emissions data from about 80 production plants in order to reduce the uncertainty associated with the default values introduced in the modelling approach.A brief review of the European emission levels for chlorinated organic substances is given as well as the temporal trends of both emission and environmental levels. A methodology to quantify the trends in measured concentrations at local and regional scales is briefly described. The observed decreasing trends demonstrate the continuous progress made by the Euro Chlor member companies in protecting the environment.Finally, the problems linked to the simultaneous presence in the environment of naturally and man-made chlorinated substances are briefly reviewed. To stimulate further research in the field, two key questions are raised which have not yet found a satisfactory answer: how to quantify natural background levels and how to quantify global persistence in the environment?     

Estimating national landfill methane emissions: an application of the 2006 Intergovernmental Panel on Climate Change Waste Model in Panama

This paper estimates national methane emissions from solid waste disposal sites in Panama over the time period 1990-2020 using both the 2006 Intergovernmental Panel on Climate Change (IPCC) Waste Model spreadsheet and the default emissions estimate approach presented in the 1996 IPCC Good Practice Guidelines. The IPCC Waste Model has the ability to calculate emissions from a variety of solid waste disposal site types, taking into account country- or region-specific waste composition and climate information, and can be used with a limited amount of data. Countries with detailed data can also run the model with country-specific values. The paper discusses methane emissions from solid waste disposal; explains the differences between the two methodologies in terms of data needs, assumptions, and results; describes solid waste disposal circumstances in Panama; and presents the results of this analysis. It also demonstrates the Waste Model's ability to incorporate landfill gas recovery data and to make projections. The former default method methane emissions estimates are 25 Gg in 1994, and range from 23.1 Gg in 1990 to a projected 37.5 Gg in 2020. The Waste Model estimates are 26.7 Gg in 1994, ranging from 24.6 Gg in 1990 to 41.6 Gg in 2020. Emissions estimates for Panama produced by the new model were, on average, 8% higher than estimates produced by the former default methodology. The increased estimate can be attributed to the inclusion of all solid waste disposal in Panama (as opposed to only disposal in managed landfills), but the increase was offset somewhat by the different default factors and regional waste values between the 1996 and 2006 IPCC guidelines, and the use of the first-order decay model with a time delay for waste degradation in the IPCC Waste Model.     

Effective pollutant emission heights for atmospheric transport modelling based on real-world information

Emission data needed as input for the operation of atmospheric models should not only be spatially and temporally resolved. Another important feature is the effective emission height which significantly influences modelled concentration values. Unfortunately this information, which is especially relevant for large point sources, is usually not available and simple assumptions are often used in atmospheric models. As a contribution to improve knowledge on emission heights this paper provides typical default values for the driving parameters stack height and flue gas temperature, velocity and flow rate for different industrial sources. The results were derived from an analysis of the probably most comprehensive database of real-world stack information existing in Europe based on German industrial data. A bottom-up calculation of effective emission heights applying equations used for Gaussian dispersion models shows significant differences depending on source and air pollutant and compared to approaches currently used for atmospheric transport modelling.     

Spatial variance in multimedia mass balance models: comparison of LOTOS-EUROS and SimpleBox for PCB-153

The aim of this study was to determine whether nested generic box models can be used to predict spatial variance. An inter-comparison study was performed for the nested box model SimpleBox, and the spatially resolved model LOTOS-EUROS, using PCB-153 emissions in Europe as an example. We compared the two models concerning (1) average environmental concentrations, (2) spatial concentration variances, (3) spatial concentration patterns (maps), and (4) agreement with measured concentrations for the air and soil compartments. In SimpleBox, the spatial concentration variances and patterns were calculated subsequently for each separate grid cell surrounded by a regional and a continental shell with homogeneous, averaged circumstances. Average European PCB-153 concentrations calculated by LOTOS-EUROS and SimpleBox for the period 1981-2000 agree well for the air and soil compartments. Moreover, the predicted concentrations of both models are in line with the measured PCB-153 concentrations in Europe during that period. For PCB-153, the prediction of spatial concentration variances with the nested multimedia fate model SimpleBox performs adequately in most cases, except for the lower concentration boundary in the air compartment. It is concluded that SimpleBox can be used to predict the spatial maximum and average concentrations of PCB-153 in the air and soil compartments. The proposed method has to be tested systematically for different types of compounds, emission scenarios, environmental compartments and spatial scales in order to allow conclusions about the general applicability of the method.     

An inventory of nitrous oxide emissions from agriculture in the UK using the IPCC methodology: emission estimate,uncertainty and sensitivity analysis

Nitrous oxide emission from UK agriculture was estimated, using the IPCC default values of all emission factors and parameters, to be 87 Gg N₂O–N in both 1990 and 1995. This estimate was shown, however, to have an overall uncertainty of 62%. The largest component of the emission (54%) was from the direct (soil) sector. Two of the three emission factors applied within the soil sector, EF1 (direct emission from soil) and EF3_PRP (emission from pasture range and paddock) were amongst the most influential on the total estimate, producing a ±31 and +11% to −17% change in emissions, respectively, when varied through the IPCC range from the default value. The indirect sector (from leached N and deposited ammonia) contributed 29% of the total emission, and had the largest uncertainty (126%). The factors determining the fraction of N leached (Frac_LEACH) and emissions from it (EF5), were the two most influential. These parameters are poorly specified and there is great potential to improve the emission estimate for this component. Use of mathematical models (NCYCLE and SUNDIAL) to predict Frac_LEACH suggested that the IPCC default value for this parameter may be too high for most situations in the UK.Comparison with other UK-derived inventories suggests that the IPCC methodology may overestimate emission. Although the IPCC approach includes additional components to the other inventories (most notably emission from indirect sources), estimates for the common components (i.e. fertiliser and animals), and emission factors used, are higher than those of other inventories. Whilst it is recognised that the IPCC approach is generalised in order to allow widespread applicability, sufficient data are available to specify at least two of the most influential parameters, i.e. EF1 and Frac_LEACH, more accurately, and so provide an improved estimate of nitrous oxide emissions from UK agriculture.     

Effects of input uncertainty and variability on the modelled environmental fate of organic pollutants under global climate change scenarios

Global climate change (GCC) is expected to influence the fate, exposure and risks of organic pollutants to wildlife and humans. Multimedia chemical fate models have been previously applied to estimate how GCC affects pollutant concentrations in the environment and biota, but previous studies have not addressed how uncertainty and variability of model inputs affect model predictions. Here, we assess the influence of climate variability and chemical property uncertainty on future projections of environmental fate of six polychlorinated biphenyl congeners under different GCC scenarios using a spreadsheet version of the ChemCAN model and the Crystal Ball® software. Regardless of emission mode, results demonstrate: (i) uncertainty in degradation half-lives dominates the variance of modelled absolute levels of PCB congeners under GCC scenarios; (ii) when the ratios of predictions under GCC to predictions under present day climate are modelled, climate variability dominates the variance of modelled ratios; and (iii) the ratios also indicate a maximum of about a factor of 2 change in the long-term average environmental concentrations due to GCC that is forecasted between present conditions and the period between 2080 and 2099. We conclude that chemical property uncertainty does not preclude assessing relative changes in a GCC scenario compared to a present-day scenario if variance in model outputs due to chemical properties and degradation half-lives can be assumed to cancel out in the two scenarios.     

Sustainable development of food production: a case study on scenarios for pig production

To study future, sustainable production systems, a step-wise method was used to create three future scenarios for pig production based on different sustainability goals. The first scenario focused on animal welfare and the natural behavior of the animals. The second targeted low impacts on the environment and the efficient use of natural resources. The third scenario aimed at product quality and safety. Each scenario fulfilled different aspects of sustainability, but there were goal conflicts because no scenario fulfilled all sustainability goals. The scenarios were then parameterized. The environmental impact was calculated using the life-cycle assessment (LCA) methodology, and the economic cost was calculated from the same data set. The cost per kilo of pork was highest for the animal welfare scenario and similar for the other two scenarios. The environmental scenario had the lowest environmental impact, and the product-quality scenario the highest. The results are discussed based on different future priorities.     

Methyl tertiary hexyl ether and methyl tertiary octyl ether as gasoline oxygenates: assessing risks from atmospheric dispersion and deposition

Methyl tertiary hexyl ether (MtHxE) and methyl tertiary octyl ether (MtOcE) are currently being developed as replacement oxygenates for methyl tertiary butyl ether (MtBE) in gasoline. As was the case with MtBE, the introduction of these ethers into fuel supplies guarantees their introduction into the environment as well. In this study, a screening-level risk assessment was performed by comparing predicted environmental concentrations (PEC) of these ethers to concentrations that might cause adverse effects to humans or ecosystems. A simple box model that has successfully estimated urban air concentrations of MtBE was adapted to predict atmospheric concentrations of MtHxE and MtOcE. Expected atmospheric concentrations of these ethers were also estimated using the European Union System for the Evaluation of Substances (EUSES) multimedia fate model, which simultaneously calculates PECs in the various environmental compartments of air, water, soil, and sediment. Because little or no data are available on the physicochemical, environmental, and toxicological properties of MtHxE and MtOcE, estimation methods were used in conjunction with EUSES to predict both the PECs and the concentrations at which these ethers might pose a threat. The results suggest that these ethers would contaminate the air of a moderately sized U.S. city (Boston, MA) at levels similar to those found previously for MtBE. The risk assessment module in EUSES predicted risk characterization ratios of 10(-3) and 10(-2) for MtHxE and MtOcE, respectively, in Boston, and 10(-2) and 10(-1) in very large urban centers, suggesting that these ethers pose only a minimal threat to ecosystems at the anticipated environmental concentrations. The assessment also indicates that these compounds are possible human carcinogens and that they may be present in urban air at concentrations that pose an unacceptable cancer risk. Therefore, testing of the toxicological properties of these compounds is recommended before they replace MtBE in gasoline.     

Substituting missing data in compositional analysis

Multivariate analysis of environmental data sets requires the absence of missing values or their substitution by small values. However, if the data is transformed logarithmically prior to the analysis, this solution cannot be applied because the logarithm of a small value might become an outlier. Several methods for substituting the missing values can be found in the literature although none of them guarantees that no distortion of the structure of the data set is produced. We propose a method for the assessment of these distortions which can be used for deciding whether to retain or not the samples or variables containing missing values and for the investigation of the performance of different substitution techniques. The method analyzes the structure of the distances among samples using Mantel tests. We present an application of the method to PCDD/F data measured in samples of terrestrial moss as part of a biomonitoring study.