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211.
The aim of this study was to evaluate the sediment quality in the mesotidal Douro River estuarine environment, in order to identify areas where sediment contamination could cause ecosystem degradation. Samples were obtained in five locations and sediment characterised for grain size, total organic matter, total-recoverable metals (Al, Fe, Cu, Pb, Cr, Ni, Cd, Zn and Mn), as well as acid volatile sulfide (AVS) and simultaneously extracted metals (SEM). In situ effects were evaluated by examining the macrobenthic community structure. An elutriate sediment toxicity test (ESTT) was used to estimate the amount of metals and nutrients that could be exchanged with the water column through resuspension, and its positive or negative effects on the growth of the micro-alga Emiliania huxleyi in a 10 day test. Anthropogenic metal contamination was identified at the north bank of the Douro estuary, with deleterious effects on the macrobenthic community, namely decrease in number of species and diversity. This contamination could possibly also be toxic for water column organisms, in case of resuspension, as shown by the ESTT. Sediments from the salt marsh at the south bank showed an impoverished macrobenthic community and elutriate toxicity, which appeared to be due to anaerobic conditions. This study clearly shows the usefulness of the ESST approach to assess the biological effect of resuspension of estuarine sediments. 相似文献
212.
Sánchez López FJ Gil García MD Martínez Vidal JL Aguilera PA Garrido Frenich A 《Environmental monitoring and assessment》2004,93(1-3):17-29
Water quality assessment in the Aznalcollar area was attempted using multivariate methods based on heavy metal concentrations in red swamp crayfish (Procamburus clarkii). Trace levels of four heavy metals, copper (Cu), zinc (Zn), cadmium (Cd) and lead (Pb), were detected in crayfish from eleven different stations. Principal component analysis (PCA) highlighted a gradient of contamination between the sampling stations. Cluster analysis (CA) distinguished three groups of stations. Discriminant analysis also differentiated three groups. The group centroids of the first discriminant function were used to devise an index that varies according to the source of the crayfish. These standardized values are proposed for use as a water quality index. The ability of this index to successfully predict environmental quality was proved with random samples. 相似文献
213.
In this work a comparison is made between the different approaches that can be taken to evaluate the mobility of elements in compost. The practical consequences of the results obtained are also discussed in terms of methods for cleaning up compost and using compost in environmental remediation. The mobility of potentially toxic elements in compost is evaluated by leaching with four selected eluents, i.e. diluted sulfuric acid, oxalate, citrate and EDTA. In contrast to the chelating agents, diluted sulfuric acid was found to generally have a low leaching capability for removal of heavy metals from compost. This implies that the risk of heavy metal leaching caused by natural rainfall is likely to be low. The results obtained in the leaching experiment were compared with previous results obtained from sequential fractionation. This comparison confirmed that both methods gave similar results for predicting the lability of elements in compost. A non-linear regression analysis of the leaching curves was also conducted. The leaching curves for elements with high lability could be fitted with a two components model. The labile components identified by the kinetic model are approximately in accordance with the fractions obtained from the first step of the sequential extraction method. The kinetic speciation method is shown to be a relatively rapid and simple procedure for compost which gives more information about element lability than simple leaching experiments. The leaching reagents used in this work were not effective enough to be used for cleaning up compost with a high metal content. Compost was however shown to have a high affinity for heavy metals, with the order of affinity of metal for the compost being very similar to that seen for humic acid. Compost may therefore prove to be a good remediation material for metal contaminated waste. 相似文献
214.
Solvent extraction and evaporative concentration steps are often used in procedures for the measurement of butyltins in environmental samples. As part of a larger study utilizing radiolabeled butyltins, the loss and fractionation of butyltins during sample preparation was investigated. TBT, DBT, and MBT were extracted from acidified seawater by hexane with efficiencies of about 95–99, 50–60 and 11% respectively. In addition, losses of about 70% of DBT were found during evaporative concentration of hexane. A variety of sediment extraction procedures were tested and none were found to be highly efficient for total butyltin extraction. 相似文献
215.
Thomas W. Custer Grey Pendleton Harry M. Ohlendorf 《Environmental monitoring and assessment》1990,15(1):83-89
Within-clutch variability of DDE and PCB residues in eggs from 62 clutches of black-crowned night-herons (Nycticorax nycticorax) was small (12% and 17%) compared to among-clutch variability (88% and 83%). Significant correlations between concentrations of DDE (median r=0.8885) and of PCBs (median r=0.8244) occurred when 501 correlations were run on two randomly selected eggs from within the same clutch; no significant correlation occurred for either concentrations of DDE (median r=0.0353) or PCBs (median r=–0.0843) when eggs were not restricted to the same clutch but were restricted to the same colony. The probability of finding infrequently detected organochlorine contaminants (e.g., DDT, cis-chlordane) in eggs from the same clutch varied from 43–96% and increased as the chemical became more prevalent and the number of eggs per clutch became smaller. These results further support one of the basic assumptions of the sample egg technique, that the chemical residues in one egg in a clutch accurately reflect residues in the remaining eggs of the clutch. 相似文献
216.
In the Puget Sound region of the United States a task force of community volunteers using bees monitored environmental pollution. This paper discusses advantages and limitations of public involvement in the assessment of regional environmental problems, particularly with respect to biological monitoring. This approach not only yielded extensive information about pollution levels but also was very cost effective.Work supported by Cooperative Agreement CR-810035-01-0 with the U.S. Environmental Protection Agency, Environmental Research Laboratory, Corvallis, Oregon, U.S.A. 相似文献
217.
The degradation of several biodegradable polymers was measured as a result of exposure to an anaerobic medium. The polymers investigated included materials based upon polylactic acid, polylactone, and poly(hydroxy butyrate/valerate) as well as those incorporating starch-based materials. The degradation was monitored by methane and carbon dioxide evolution. In addition, the physical and chemical changes were noted as a result of exposure. These measurements included changes in mass, dimension, and molecular weight. FTIR, UV-vis, proton, and13C NMR spectra were also recorded prior to and after exposure. The results clearly indicated that several biological and chemical degradation processes were occurring with the biodegradable polymers studied.Paper presented at the Bio/Environmentally Degradable Polymer Society—Second National Meeting, August 19–21, 1993, Chicago, Illinois.Issued as NRCC No. 37549. 相似文献
218.
P. M. Lutz Selena Bauer N. L. Gale J. Hewett P. E. Phillips F. M. Looney H. Bengsch 《Environmental geochemistry and health》1994,16(3-4):179-189
Lead has been found to depress the immune system in animal studies at levels far below those responsible for overt toxicity. Literature studies in animal systems most clearly showed an effect of lead on response to a specific immunogenic stimulus. Data are sparse concerning the effects of lead on the immune system in the human population at greatest risk for exposure-children up to six years of age. This portion of the Phase I study reports concentrations of IgG, IgM, IgA, and IgE, as well as antibody titers to the specific antigenic stimuli provided by the vaccines against diphtheria, tetanus, and Rubella. The study population consisted of a group of 193 children, ages 9 months to 6 years, who participate in the WIC (Women, Infants and Children) and Lead Poisoning Prevention Programs in the urban area of Springfield-Greene County Missouri. Blood lead levels ranged from 1 to 50 g dL–1. Total Ig levels were determined and the data were analysed. No consistent significant differences were observed among the risk categories in the five age groups examined. A single Ig class in each of three age groups showed apparent significant differences among the various risk categories, but these differences were not correlated with blood lead. An analysis of specific antibody titers to diphtheria, tetanus, and Rubella was performed. Regression analyses of current data in Phase I of this study suggest a detrimental effect of lead on the antibody titres to diphtheria and Rubella. 相似文献
219.
The authors used a global High Resolution Biosphere Model (HRBM), consisting of a biome model and a carbon cycle model, to estimate the changes of carbon storage in the major pools of the terrestrial biosphere from 18 000 BP to present. The climate change data to drive the biosphere for 18 000 BP were derived from an Atmospheric General Circulation Model. Using the AGCM anomalies interpolated to a 0.5 degrees grid, the HRBM data base of the present climate was recalculated for 18 000 BP. The most important processes which influenced the carbon storage include (1) climate-induced changes in biospheric processes and vegetation distribution, (2) the CO(2) fertilization effect, (3) the inundation of lowland areas resulting from the sea level rise of 100 m. Two scenarios were investigated. The first scenario, which ignored the CO(2) fertilization effect, led to total carbon losses from the terrestrial biosphere of -460 x 10(9) t. Scenario 2, which assumed that the model formulation of the CO(2) fertilization effect as used for preindustrial to present could be extrapolated to the glacial 200 microl litre(-1) (ppmv, parts per million per volume), gave a carbon fixation in the terrestrial biosphere of +213 x 10(9) t. The two scenarios were compared with CO(2) concentration data and isotopic ratios from air in ice cores. The results of Scenario 1 are not in agreement with the data. Scenario 2 gives realistic delta(13)C shifts in the atmosphere but the biospheric carbon storage at the end of the glacial period seems too large. The authors suggest that the low atmospheric CO(2) concentration may have favoured the C-4 plants in ice age vegetation types. As a consequence the influence of the low CO(2) concentration was eventually reduced and the glacial carbon storage in vegetation, litter, and soil was increased. 相似文献
220.
This study was designed to evaluate the ability of an in-situ bioassay to assess the impact of complex effluents on freshwaters and to identify toxic components. Reductions in the feeding rate of Gammarus pulex proved to be a sensitive indicator of the impact of metalliferous effluents on receiving water quality. The effluents contained a mixture of five potentially toxic metals. By combining information on feeding rates with bioaccumulation data, two metals, iron and manganese, were identified as the probable toxic agents. Laboratory experiments validated the conclusions reached from the field study and confirmed that iron was a major toxicant. The sensitivities of Gammarus pulex from a metal-contaminated site and a clean site were compared during both the field and laboratory studies. Interpopulation differences in the response of G. pulex to toxicants were detected in the field study but not in the laboratory experiments. Possible reasons for this are discussed. 相似文献