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991.
992.
Long ER Dutch M Aasen S Welch K Hameedi MJ 《Environmental monitoring and assessment》2005,111(1-3):173-222
A survey was designed and conducted to determine the severity, spatial patterns, and spatial extent of degraded sediment quality
in Puget Sound (Washington State, USA). A weight of evidence compiled from results of chemical analyses, toxicity tests, and
benthic infaunal analyses was used to classify the quality of sediments. Sediment samples were collected from 300 locations
within a 2363 km2 area extending from the US/Canada border to the inlets of southern Puget Sound and Hood Canal. Degraded conditions, as indicated
with a combination of high chemical concentrations, significant toxicity, and adversely altered benthos, occurred in samples
that represented about 1% of the total area. These conditions invariably occurred in samples collected within urbanized bays
and industrial waterways, especially near the urban centers of Everett, Seattle, Tacoma, and Bremerton. Sediments with high
quality (as indicated by no toxicity, no contamination, and the presence of a relatively abundant and diverse infauna) occurred
in samples that represented a majority (68%) of the total study area. Sediments in which results of the three kinds of analyses
were not in agreement were classified as intermediate in quality and represented about 31% of the total area. Relative to
many other estuaries and marine bays of the USA, Puget Sound sediments ranked among those with minimal evidence of toxicant-induced
degradation. 相似文献
993.
Bioassessment of nonwadeable streams in the United States is increasing, but methods for these systems are not as well-developed as for wadeable streams. In this study, we compared six macroinvertebrate field sampling methods for nonwadeable streams adapted from those used by three major programs: the U.S. Environmental Protection Agencys Environmental Monitoring and Assessment Program-Surface Waters, the U.S. Geological Surveys National Water Quality Assessment Program, and the Ohio Environmental Protection Agency, Division of Surface Water Biocriteria Program. We performed all six methods at 60 sites across four rivers and measured water chemistry and physical habitat at each site to assess abiotic conditon. Sites were divided into two groups: those influenced by navigational lock and dam structures (restricted flow, or RF) and those free-flowing or with lowhead dams (run-of-the-river, or ROR). Metrics based on passive Hester-Dendy artificial substrate samplers differed greatly from active sampling methods (i.e., using nets) but represented abiotic conditions well in both ROR and RF sites. Although metric values were similar across certain sampling methods, the metrics significantly correlated with abiotic variables varied among methods and between ROR and RF sites. These results emphasize that methods are not interchangeable, and the ability to detect certain stressors depends on sampling method.The U.S. Governments right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged. 相似文献
994.
Occurrence of halogenated disinfection by-products (DBPs) (trihalomethanes –THMs– and haloacetic acids –HAAs–) in the waters
of two utilities in Quebec City (Canada) was investigated using two approaches: experimental chlorination studies and full-scale
sampling within distribution systems. Experimental studies were designed to reproduce treatment plant and distribution system
conditions (chlorine dose, water temperature, pH and water residence time). Differences in halogenated DBPs in the two distribution
systems under study were significant and comparable to those observed in experimental laboratory studies. For the waters of
both utilities, chlorination studies better reproduced the occurrence of halogenated DBPs in points of the distribution system
located near the treatment plant (low residence time of water) than in other points. Multivariate regression models for THMs,
HAAs and their species were developed using the data from experimental studies in order to predict halogenated DBP levels
measured in the distribution system. Models were all statistically significant, but showed low ability to predict full-scale
halogenated DBPs, particularly in points located at distribution system extremities. Specifically, experimental chlorination-based
models are not able to simulate the decrease of HAA levels. Results of this research suggest that the use of experimental
data to predict halogenated DBP levels in full-scale distribution systems – for operational, regulatory and epidemiological
purposes – must be done with caution. 相似文献
995.
Hyland JL Balthis WL Engle VD Long ER Paul JF Summers JK Van Dolah RF 《Environmental monitoring and assessment》2003,81(1-3):149-161
Synoptic data on concentrations of sediment-associated chemical contaminants and benthic macroinfaunal community structure were collected from 1,389 stations in estuaries along the U.S. Atlantic and Gulf of Mexico coasts as part of the nationwide Environmental Monitoring and Assessment Program (EMAP). These data were used to develop an empirical framework for evaluating risks of benthic community-level effects within different ranges of sediment contamination from mixtures of multiple chemicals present at varying concentrations. Sediment contamination was expressed as the mean ratio of individual chemical concentrations relative to corresponding sediment quality guidelines (SQGs), including Effects Range-Median (ERM) and Probable Effects Level (PEL) values. Benthic condition was assessed using diagnostic, multi-metric indices developed for each of three EMAP provinces (Virginian, Carolinian, and Louisianian). Cumulative percentages of stations with a degraded benthic community were plotted against ascending values of the mean ERM and PEL quotients. Based on the observed relationships, mean SQG quotients were divided into four ranges corresponding to either a low, moderate, high, or very high incidence of degraded benthic condition. Results showed that condition of the ambient benthic community provides a reliable and sensitive indicator for evaluating the biological significance of sediment-associated stressors. Mean SQG quotients marking the beginning of the contaminant range associated with the highest incidence of benthic impacts (73–100% of samples, depending on the province and type of SQG) were well below those linked to high risks of sediment toxicity as determined by short-term toxicity tests with single species. Measures of the ambient benthic community reflect the sensitivities of multiple species and life stages to persistent exposures under actual field conditions. Similar results were obtained with preliminary data from the west coast (Puget Sound). 相似文献
996.
997.
The distribution of trace metals in sediments of the lower reaches of the New Calabar River, Nigeria was evaluated togetherwith the partitioning of their chemical species between fivegeochemical phases. Samplings were made in five zones at the lower reaches of the New Calaber River. All the trace metals were determined by AAS after selective chemical extractions andconcentrations given in g gm-1 (dry weight basis). The average totalconcentrations found for trace metals in the sediment were (mean ± rsd.) Pb: 41.6 ± 0.29, Zn: 31.60 ± 0.42, Cd: 12.80 ± 0.92, Co: 92 ± 0.25, Cu: 25.5 ± 0.65 and Ni: 3.2 ± 0.25. Maxima and minima concentrations are inconsistent with previous studies in other rivers of this region. Spatial distribution revealed that the sources of trace metals into theriver appeared to be of non-point. Five contamination indices were applied in studying the partitioning of the trace metals inthe sediment. These indices provided bases for ascertaining the potential environmental risk of trace metals in the river system.The results denote high partition levels in the more mobile andmore dangerous phases. 相似文献
998.
悬浮液进样石墨炉原子吸收法直接测定土壤、底泥中的铅、镓、钴、镍 总被引:1,自引:0,他引:1
介绍一种悬浮液进样直接测定土壤、底泥中多种微量金属元素的快速分析方法。基体改进剂的使用,适宜的原子化温度的选择,使用水相标准溶液作校准曲线成为可能.对标准作品的测定证明了此方法的精密度和准确度较好,适合于常规环境样品分析. 相似文献
999.
1000.