Influence of the turbulence typing scheme upon the cumulative frequency distributions of the calculated relative concentrations for different averaging times

Over a period of three consecutive years (1977–1979) hourly meteorological measurements at the Nuclear Energy Research Centre (SCK/CEN) Mol, Belgium and simultaneous synoptic observations at the nearby military airport of Kleine Brogel, have been compiled as input data for a bi-Gaussian dispersion model. The available information has first of all been used to determine hourly stability classes in ten widely used turbulent diffusion typing schemes. Systematic correlations between different systems were rare. Twelve different combinations of diffusion typing scheme-dispersion parameters were then used for calculating cumulative frequency distributions of 1 h, 8 h, 16 h, 3 d and 26 d average ground-level concentrations at receptors respectively at 500 m, l km, 2 km, 4 km and 8 km from a continuous ground-level release and an elevated release at 100 m height. Major differences were noted as well in the extreme values, the higher percentiles, as in the annual mean concentrations. These differences are almost entirely due to the differences in the numerical values (as a function of distance) of the various sets of dispersion parameters actually in use for impact assessment studies. Dispersion parameter sets giving the lowest normalized ground-level concentration values for groundlevel releases give the highest results for elevated releases and vice versa. While it was illustrated once again that the applicability of a given set of dispersion parameters is restricted due to the specific conditions under which the given set was derived (theoretically, experimentally and/or empirically), it was also concluded that systematic experimental work to validate certain assumptions is urgently needed.     

Monitoring, modelling and environmental exposure assessment of industrial chemicals in the aquatic environment

Monitoring and laboratory data play integral roles alongside fate and exposure models in comprehensive risk assessments. The principle in the European Union Technical Guidance Documents for risk assessment is that measured data may take precedence over model results but only after they are judged to be of adequate reliability and to be representative of the particular environmental compartments to which they are applied. In practice, laboratory and field data are used to provide parameters for the models, while monitoring data are used to validate the models' predictions. Thus, comprehensive risk assessments require the integration of laboratory and monitoring data with the model predictions. However, this interplay is often overlooked. Discrepancies between the results of models and monitoring should be investigated in terms of the representativeness of both. Certainly, in the context of the EU risk assessment of existing chemicals, the specific requirements for monitoring data have not been adequately addressed. The resources required for environmental monitoring, both in terms of manpower and equipment, can be very significant. The design of monitoring programmes to optimise the use of resources and the use of models as a cost-effective alternative are increasing in importance. Generic considerations and criteria for the design of new monitoring programmes to generate representative quality data for the aquatic compartment are outlined and the criteria for the use of existing data are discussed. In particular, there is a need to improve the accessibility to data sets, to standardise the data sets, to promote communication and harmonisation of programmes and to incorporate the flexibility to change monitoring protocols to amend the chemicals under investigation in line with changing needs and priorities.     

New PEC definitions for river basins applicable to GIS-based environmental exposure assessment

By means of GREAT-ER (Geo-Referenced Regional Exposure Assessment Tool for European Rivers) aquatic chemical fate simulations can be performed for river basins. To apply the resulting digital maps with local (river stretch specific) predicted concentrations in regional aquatic exposure and risk assessment, the output has to be aggregated to a (single) value representative of exposure in the catchment. Two spatially aggregated PEC definitions are proposed for this purpose: PECinitial (unweighted aggregation of concentrations just downstream of wastewater emissions) and PECcatchment (weighted aggregation of all average stretch concentrations). These PECs were tested using simulations for two pilot study catchments (Calder and Went, UK). This confirmed the theoretical considerations which led to the definitions, and it illustrated the need for weighting to resolve scale-dependencies.     

Degradation half-life times of PCDDs, PCDFs and PCBs for environmental fate modeling

Literature search of the knowledge on the degradation of persistent organic pollutants (POPs) in environmental compartments air, water, soil and sediment was done in purpose to find properties of POPs of interest for modeling. One degradation process, hydrolysis (chemical degradation), was omitted as negligibly slow for POPs studied. The other two, photolysis and biodegradation processes, were considered separately in purpose to develop estimation procedures. The estimates can be given as pseudo first-order rate constants kP for photolysis and kB for biodegradation. For each compartment, an overall degradation rate is k(tot) = kP + kB and lifetime t(1/2) = ln 2/k(tot). The latter values, lifetimes in each compartment, will be used as input parameters to the Baltic Sea model.     

Dose-dependent induction of heat shock protein 70 synthesis in Raphidocelis subcapitata following exposure to different classes of environmental pollutants

In this study an enzyme-linked immunosorbent assay (ELISA) was developed to detect the stress protein Hsp70 in the green alga Raphidocelis subcapitata. Using this ELISA, the response to a variety of pollutants, including ZnCl2, SeO2 (heavy metals), lindane (organochlorine pesticide), pentachlorophenol (PCP, chlorinated hydrocarbon insecticide and fungicide), carbaryl (carbamate pesticide) and sodium dodecyl sulphate (SDS; surfactant) was tested. Our results show that Hsp 70 is produced in a dose-dependent way in response to most chemicals investigated (except PCP) and at concentrations below the range of classical cytotoxicity testing (i.e. growth inhibition, lethality). Still, the potential to induce Hsp70 varied among the pollutants tested, the heavy metals ZnCl2 and SeO2 being the strongest inducers of Hsp70. Combined with the existing literature, these results indicate that Hsp70 in R. subcapitata is a sensitive biomarker for a wide range of environmental pollutants.     

Improving bioaerosol exposure assessments of composting facilities — Comparative modelling of emissions from different compost ages and processing activities

We present bioaerosol source term concentrations from passive and active composting sources and compare emissions from green waste compost aged 1, 2, 4, 6, 8, 12 and 16 weeks. Results reveal that the age of compost has little effect on the bioaerosol concentrations emitted for passive windrow sources. However emissions from turning compost during the early stages may be higher than during the later stages of the composting process. The bioaerosol emissions from passive sources were in the range of 10³–10⁴ cfu m⁻³, with releases from active sources typically 1-log higher. We propose improvements to current risk assessment methodologies by examining emission rates and the differences between two air dispersion models for the prediction of downwind bioaerosol concentrations at off-site points of exposure. The SCREEN3 model provides a more precautionary estimate of the source depletion curves of bioaerosol emissions in comparison to ADMS 3.3. The results from both models predict that bioaerosol concentrations decrease to below typical background concentrations before 250 m, the distance at which the regulator in England and Wales may require a risk assessment to be completed.     

The acute toxicity of chlorobenzenes for earthworms (Eisenia andrei) in different exposure systems

Earthworms (Eisenia andrei) were exposed to different concentrations of two chlorobenzenes (1,2,3-trichloro- and pentachlorobenzene) using different routes of administration: in water, in soil, via food and on filter paper. Except for the contact paper toxicity test, lethal body burdens (LBBs) measured in these different exposure systems were similar for the same test chemical. LBBs for 1,2,3-trichlorobenzene varied between 0.44 and 2.1 μmol/g and for pentachlorobenzene between 1.29 and 2.34 μmol/g. These values correspond with literature data for fish. For 1,4-dichloro- and 1,2,3,4-tetrachlorobenzene LBBs measured with the contact paper toxicity test were 0.33 and 3.2 μmol/g, respectively. Exposure to hexachlorobenzene and hexabromobenzene using the contact toxicity test did not result in death within 48 hours.     

Susceptibility of different yeast species to environmental toxic metals

The purpose of the study reported here was to investigate the relative resistance of yeast species to various metallic and metalloid ions, with a view to gaining more knowledge on this subject, as resistant species may become dominant in habitats contaminated with the relevant metals. Saccharomyces cerevisiae, Candida albicans and Candida tropicalis were grown in media containing different concentrations of mercury (as HgCl(2)), cadmium (as CdCl(2)), lead (as Pb(CH(3)COO)(2)), arsenic (as Na(2)HAsO(4)) and selenium (as Na(2)SeO(3)) for various intervals. Invariably, the two Candida species turned out to be more resistant to all the metals studied than S. cerevisiae. The metal showing the highest toxicity for these species was mercury, with cadmium being the second, lead, the third and arsenic and selenium being the least toxic elements. Strains showing resistance to mercury were isolated, even in the case of S. cerevisiae.     

Comparison of different stomatal conductance algorithms for ozone flux modelling

A multiplicative and a semi-mechanistic, BWB-type [Ball, J.T., Woodrow, I.E., Berry, J.A., 1987. A model predicting stomatal conductance and its contribution to the control of photosynthesis under different environmental conditions. In: Biggens, J. (Ed.), Progress in Photosynthesis Research, vol. IV. Martinus Nijhoff, Dordrecht, pp. 221-224.] algorithm for calculating stomatal conductance (g(s)) at the leaf level have been parameterised for two crop and two tree species to test their use in regional scale ozone deposition modelling. The algorithms were tested against measured, site-specific data for durum wheat, grapevine, beech and birch of different European provenances. A direct comparison of both algorithms showed a similar performance in predicting hourly means and daily time-courses of g(s), whereas the multiplicative algorithm outperformed the BWB-type algorithm in modelling seasonal time-courses due to the inclusion of a phenology function. The re-parameterisation of the algorithms for local conditions in order to validate ozone deposition modelling on a European scale reveals the higher input requirements of the BWB-type algorithm as compared to the multiplicative algorithm because of the need of the former to model net photosynthesis (A(n)).     

Effect of chronic exposure to cadmium on hepatic drug metabolism

In an attempt to examine the chronic effect of low levels of cadmium on hepatic drug-metabolizing enzyme system, an experiment was carried out in which growing male rats were given 0, 5, 10, and 20 ppm of cadmium in drinking water for a period of 8 weeks. An ip administration of a hypnotic dose of pentobarbital to the cadmium-treated and the control rats 24 hr following the termination of the experiment exhibited that there was no significant difference in the drug metabolism in control and any of the treated groups. Next, liver microsomes were isolated from animals in all groups to study their ability to metabolize drugs in vitro. The results indicated that the activity of benzphetamine N-demethylase and aniline hydroxylase, and the concentration of microsomal cytochrome P-450 were almost identical in the control and treated groups. On the other hand, a single ip dose of cadmium (2 mg/kg) caused significant decrease in the vivo and in vitro microsomal drug metabolism. These results suggest that although a single ip dose of cadmium (2 mg/kg) causes significant inhibition of drug metabolism, chronic exposure to cadmium up to 20 ppm in drinking water over a period of 8 weeks is unlikely to affect hepatic drug metabolism.     

Effect of chronic exposure to cadmium on hepatic drug metabolism

Abstract

In an attempt to examine the chronic effect of low levels of cadmium on hepatic drug‐metabolizing enzyme system, an experiment was carried out in which growing male rats were given 0, 5, 10, and 2 0 ppm of cadmium in drinking water for a period of 8 weeks. An ip administration of a hypnotic dose of pentobarbital to the cadmium‐treated and the control rats 2 4 hr following the termination of the experiment exhibited that there was no significant difference in the drug metabolism in control and any of the treated groups. Next, liver microsomes were isolated from animals in all groups to study their ability to metabolize drugs in vitro. The results indicated that the activity of benzphetamine N‐demethylase and aniline hydroxylase, and the concentration of microsomal cytochrome P‐450 were almost identical in the control and treated groups. On the other hand, a single ip dose of cadmium (2 mg/kg) caused significant decrease in the in vivo and in vitro microsomal drug metabolism. These results suggest that although a single ip dose of cadmium (2 mg/kg) causes significant inhibition of drug metabolism, chronic exposure to cadmium up to 2 0 ppm in drinking water over a period of 8 weeks is unlikely to affect hepatic drug metabolism.     

The acute and chronic toxicity of lanthanum to Daphnia carinata

The rare earth elements (REEs) are increasingly being used as trace supplements in agriculture. This study measured the acute and chronic toxicity of one REE, lanthanum (La), to Daphnia carinata. The 48-h EC50 of La to Daphnia was measured in three media of differing composition and hardness. Lanthanum was most toxic to Daphnia in soft tap water (TW) with an acute 48-h EC50 of 43 microg/l compared with 1180 microg/l in ASTM hard water (ASTM). In the third daphnid growth medium (DW), based on diluted sea water, the acute 48-h EC50 was 49 microg La/l, however, there was significant precipitation of La in this media. The chronic toxicity of La to Daphnia was measured in the DW and ASTM media. Nominal exposure concentrations were 100, 200, 400, 600, 800, and 1000 microg La/l. Mortality was a more sensitive endpoint than growth or reproduction in both chronic experiments. Very little La was detected in either media after 24 h and the measured concentrations below were estimated by logarithmic mean of nominal and measured values. There was 100% mortality at concentrations > or = 80 microg La/l (400 microg/l nominal) by day six of the experiment using DW media, but no effect on survival growth or reproduction at lower concentrations. In the ASTM media, La caused significant mortality to Daphnia at concentrations > or = 39 microg/l (200 microg/l nominal), however, at least one animal survived to the end of the study at each of the tested concentrations. There was no effect of La on growth of surviving daphnids at concentrations < or = 57 microg/l (400 g/l), however, second brood clutch sizes were significantly increased at 30, 39, and 57 microg/l (100, 200, 400 g/l nominal) compared with controls. Lanthanum also caused a delayed maturation in Daphnia.     

Circulating microRNAs as biomarkers of environmental exposure to polycyclic aromatic hydrocarbons: potential and prospects

Environmental Science and Pollution Research - Exposure to polycyclic aromatic hydrocarbons (PAHs) produced from various pyrogenic and petrogenic&nbsp;sources in the environment has been linked...     

Health risks of environmental exposure to metals and herbicides in the Pardo River,Brazil

Mixture of metals and herbicides in rivers may pose relevant risks for the health of surrounding communities. Humans may be exposed to river pollution through intake of contaminated water and fish, as well as irrigated agricultural products. The aim of this study was to assess the human health risks of environmental exposure to metals and herbicides through water and fish intake in the Pardo River. Metals (Al, As, Be, Cd, Cr, Cu, Pb, Mn, Hg, Ni, Tl, Sn, V, and Zn) were analyzed in river water and in edible fish. Herbicides (ametryn, atrazine, diuron, hexazinone, simazine, and tebuthiuron) were analyzed in river water. Seasonal variances were also studied. Aluminum, Cd, Cu, Mn, Pb, and Zn levels in river water were higher than the USEPA benchmarks. Non-carcinogenic risks due to pollutants mixture exposure were above the limit, and carcinogenic risks of As exposure were >10^?6 in the sampling points during the rainy season. Metal levels in fish were lower than the Brazilian legislation and do not pose a threat to public health. Herbicides were detected in four sampling points, with atrazine concentrations (range 0.16–0.32 μg/L) below the Brazilian standard (2.0 μg/L), but above the European Union standard (0.1 μg/L). Considering the water supply needs of cities located in the Pardo River Basin and the persistence of metals and herbicides, the present study indicated that there was a seasonal influence on non-carcinogenic and carcinogenic risks to human health, especially in the rainy season. Studies for water treatment plants implantation should consider the risks of exposure to persistent substances, in order to protect the population.     

Use of OECD premarket data in environmental exposure analysis for new chemicals

As part of the OECD Chemicals Group program, much effort has gone into trying to identify and develop methodologies for predicting human and environmental exposure to new chemicals. This paper reviews this activity and discusses the applicabilities and limitations of the methodologies. Of special interest is the model developed by Mackay and adapted by Wood that can be used at several levels of sophistication depending on the chemical and environmental data available.     

挥发性有机污染物与恶臭的生物处理技术及其工艺选择

本文介绍了生物滤池、生物洗涤塔和生物滴滤池处理挥发性有机污染物及恶臭的特性、近期发展状况及其应用。阐述了亨利系数在选择生物处理技术中的作用 ,以及生物反应器内填料、微生物的选择     

Assessing vegetation exposure to ozone: properties of the AOT40 index and modifications by deposition modelling

A discussion is presented on the application of micrometeorological deposition modelling principles to improve the characterisation of vegetation exposure to ozone and thus the use of critical levels as the basis of targeted emission control. The AOT40 (accumulated exposure over a threshold of 40 ppb or nl l(-1)) ozone exposure index is shown to impose a differential weighting that results in a high sensitivity, by a factor of two to 10 depending on the pollution climate, with respect to concentration. This makes it necessary to correct for systematic effects, such as the concentration profile below the measurement height, in order to justify a comparison with the biological data obtained from well-mixed exposure chambers. Available studies indicate a 50-70% lower AOT40 at the vegetation height. The resistance method for estimating the profile is extended to allow for stomatal effects that potentially bias the plant response predicted with an exposure index. This integrated profile-uptake correction refines the current approach and serves as a transitional step towards a real flux-based approach. For the latter, a new deposition parameterisation is tested against field observations.