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801.
802.
Exposure to inhaled THM: Comparison of continuous and event-specific exposure assessment for epidemiologic purposes 总被引:2,自引:0,他引:2
Trihalomethanes (THMs) (chloroform, bromoform, dibromochloromethane, and bromodichloromethane) are the most abundant by-products of chlorination. People are exposed to THMs through ingestion, dermal contact and inhalation. The objective of this study was to compare two methods for assessing THM inhalation: a direct method with personal monitors assessing continuous exposure and an indirect one with microenvironmental sampling and collection of time–activity data during the main event exposures: bathing, showering and swimming. This comparison was conducted to help plan a future epidemiologic study of the effects of THMs on the upper airways of children. 30 children aged from 4 to 10 years were included. They wore a 3M™ 3520 organic vapor monitor for 7 days. We sampled air in their bathrooms (during baths or showers) and in the indoor swimming pools they visited and recorded their time–activity patterns. We used stainless steel tubes full of Tenax® to collect air samples. All analyses were performed with Gas Chromatography and Mass Spectrometry (GC-MS). Chloroform was the THM with the highest concentrations in the air of both bathrooms and indoor swimming pools. Its continuous and event exposure measurements were significantly correlated (rs = 0.69 p < 0.001). Continuous exposures were higher than event exposures, suggesting that the event exposure method does not take into account some influential microenvironments. In an epidemiologic study, this might lead to random exposure misclassification, thus underestimation of the risk, and reduced statistical power. The continuous exposure method was difficult to implement because of its poor acceptability and the fragility of the personal monitors. These two points may also reduce the statistical power of an epidemiologic study. It would be useful to test the advantages and disadvantages of a second sample in the home or of modeling the baseline concentration of THM in the home to improve the event exposure method. 相似文献
803.
Nur Okur A. Levent Tuna Bülent Okur Hakan Altunlu H. Hüsnü Kayikçioğlu Hasan S. Civelek 《Environmental monitoring and assessment》2010,165(1-4):389-397
Efficacious botanical derivatives can provide an alternative to synthetic pesticides for organic farming systems. However, there is lack of information regarding the side effects of organic pesticides on key soil ecological processes. In this study, we investigated the effects of aqueous extracts from Urginea maritima and Euphorbia myrsinites exhibiting translaminar and systemic activity against pests on microbial biomass and enzymatic activities in soil. Two grams of plant material was extracted with 100 ml of water and then diluted 1:100, 2:100, and 4:100 with distilled water. Diluted plant extracts were applied around hypocotyl of tomato by soil drench. The effect of both plant extracts on microbial biomass C, amount of total N and organic C, and enzymatic activity in soil was significant. After the last application, the highest microbial biomass C was determined in the lowest U. maritima concentration (U 1:100). Soils treated with the highest concentration of U. maritima (U 4:100) had always lower SMBC content than control soil. All concentrations of E. myrsinites decreased microbial biomass C by 18% to 27% compared to the control. Total nitrogen and organic carbon decreased in soils without (control) and with treated U. maritima extract from first application to last application. Phosphatase, urease, and β-glucosidase activities were monitored in plant extract-treated soils. Except U. maritima 1:100 treatments of second and fourth applications, the other treatments of plant extracts negatively affected enzymatic activity in soil. U. maritima and E. myrsinites plant extracts exhibited different effects on soil microbial biomass and activity, probably because of their different chemical contents. 相似文献
804.
H.C. Agarwal D.K. Singh V.B. Sharma 《Journal of environmental science and health. Part. B》2013,48(1):189-194
Abstract Persistence, metabolism and binding of 14C‐parathion in alkaline sandy loam soil under sub‐tropical conditions of Delhi were studied for 545 days. After 3 days of treatment, 14C‐residues declined to 41% of the amount applied. The dissipation curve was biphasic; an initial rapid phase (up to 7 days) followed by slow dissipation. The half life of dissipation was only 3.36 days for the first phase and 84 days for the slow phase. The overall half life was 64.5 days. The total residues at zero‐time were 10.65 μg/g dry soil and were almost totally extractable. The extracts consisted of parathion, 4‐aminophenol, 4‐nitrophenol and paraoxon. The bound residues gradually increased and accounted for the total residue at the end of one year (0.7 μg/g). 相似文献
805.
Sara P. Bombaci Cooper M. Farr H. Travis Gallo Anna M. Mangan Lani T. Stinson Monica Kaushik Liba Pejchar 《Conservation biology》2016,30(1):216-225
Scientists are increasingly using Twitter as a tool for communicating science. Twitter can promote scholarly discussion, disseminate research rapidly, and extend and diversify the scope of audiences reached. However, scientists also caution that if Twitter does not accurately convey science due to the inherent brevity of this media, misinformation could cascade quickly through social media. Data on whether Twitter effectively communicates conservation science and the types of user groups receiving these tweets are lacking. To address these knowledge gaps, we examined live tweeting as a means of communicating conservation science at the 2013 International Congress for Conservation Biology (ICCB). We quantified and compared the user groups sending and reading live tweets. We also surveyed presenters to determine their intended audiences, which we compared with the actual audiences reached through live tweeting. We also asked presenters how effectively tweets conveyed their research findings. Twitter reached 14 more professional audience categories relative to those attending and live tweeting at ICCB. However, the groups often reached through live tweeting were not the presenters’ intended audiences. Policy makers and government and non‐governmental organizations were rarely reached (0%, 4%, and 6% of audience, respectively), despite the intent of the presenters. Plenary talks were tweeted about 6.9 times more than all other oral or poster presentations combined. Over half the presenters believed the tweets about their talks were effective. Ineffective tweets were perceived as vague or missing the presenters’ main message. We recommend that presenters who want their science to be communicated accurately and broadly through Twitter should provide Twitter‐friendly summaries that incorporate relevant hashtags and usernames. Our results suggest that Twitter can be used to effectively communicate speakers’ findings to diverse audiences beyond conference walls. 相似文献
806.
Assessment of groundwater pollution in West Delhi, India using geostatistical approach 总被引:3,自引:0,他引:3
Partha Pratim Adhikary H. Chandrasekharan Debashis Chakraborty Kalpana Kamble 《Environmental monitoring and assessment》2010,167(1-4):599-615
The exploration, exploitation, and unscientific management of groundwater resources in the National Capital Territory (NCT) of Delhi, India have posed a serious threat of reduction in quantity and deterioration of quality. The objective of the study is to determine the groundwater quality and to assess the risk of groundwater pollution at Najafgarh, NCT of Delhi. The groundwater quality parameters were analyzed from the existing wells of the Najafgarh and the thematic maps were generated using geostatistical concepts. Ordinary kriging and indicator kriging methods were used as geostatistical approach for preparation of thematic maps of the groundwater quality parameters such as bicarbonate, calcium, chloride, electrical conductivity (EC), magnesium, nitrate, sodium, and sulphate with concentrations equal or greater than their respective groundwater pollution cutoff value. Experimental semivariogram values were fitted well in spherical model for the water quality parameters, such as bicarbonate, chloride, EC, magnesium, sodium, and sulphate and in exponential model for calcium and nitrate. The thematic maps of all the groundwater quality parameters exhibited an increasing trend of pollution from the northern and western part of the study area towards the southern and eastern part. The concentration was highest at the southernmost part of the study area but it could not reflect correctly the groundwater pollution status. The indicator kriging method is useful to assess the risk of groundwater pollution by giving the conditional probability of concentrations of different chemical parameters exceeding their cutoff values. Thus, risk assessment of groundwater pollution is useful for proper management of groundwater resources and minimizing the pollution threat. 相似文献
807.
Rainfall trends in twentieth century over Kerala,India 总被引:1,自引:0,他引:1
K.N. Krishnakumar G.S.L.H.V. Prasada Rao C.S. Gopakumar 《Atmospheric environment (Oxford, England : 1994)》2009,43(11):1940-1944
Attempts were made to study temporal variation in monthly, seasonal and annual rainfall over Kerala, India, during the period from 1871 to 2005. Longterm changes in rainfall determined by Man-Kendall rank statistics and linear trend. The analysis revealed significant decrease in southwest monsoon rainfall while increase in post-monsoon season over the State of Kerala which is popularly known as the “Gateway of summer monsoon”. Rainfall during winter and summer seasons showed insignificant increasing trend. Rainfall during June and July showed significant decreasing trend while increasing trend in January, February and April. Hydel power generation and water availability during summer months are the concern in the State due to rainfall decline in June and July, which are the rainiest months. At the same time, majority of plantation crops are likely to benefit due to increase in rainfall during the post-monsoon season if they are stable and prolonged. 相似文献
808.
Hydrogenation units are often operated at high pressure, requiring the use of compressors which are one of the most expensive chemical processing equipment. Optimizing a hydrogen network should therefore take into consideration not only purity and flowrate constraints but also pressure requirements. In this paper, based on the hydrogen surplus diagram approach, the average pressure profiles of hydrogen sources and sinks are proposed through the introduction of a system’s minimum pressure drop Δp. Combined with the traditional purity profiles, whether a source can meet a sink either for hydrogen concentration or for pressure requirements can be determined intuitively. In cases where the pressure of a source is not sufficient for a sink, installing a hydrogen compressor or using another source with higher purity and pressure could be potential solutions. A cost equation is established to determine which of the two solutions is economically more viable. For different matching situations between sources and sinks, strategies for optimum placement of compression equipment within a given hydrogen network are proposed. A case study is used to illustrate the application and effectiveness of the proposed method. 相似文献
809.
Assessing ecological risk on a regional scale 总被引:17,自引:0,他引:17
Carolyn T. Hunsaker Robin L. Graham Glenn W. Suter II Robert V. O'Neill Lawrence W. Barnthouse Robert H. Gardner 《Environmental management》1990,14(3):325-332
Society needs a quantitative and systematic way to estimate and compare the impacts of environmental problems that affect
large geographic areas. This paper presents an approach for regional risk assessment that combines regional assessment methods
and landscape ecology theory with an existing framework for ecological risk assessment. Risk assessment evaluates the effects
of an environmental change on a valued natural resource and interprets the significance of those effects in light of the uncertainties
identified in each component of the assessment process. Unique and important issues for regional risk assessment are emphasized;
these include the definition of the disturbance scenario, the assessment boundary definition, and the spatial heterogeneity
of the landscape.
Although the research described in this article has been funded wholly or in part by the United States Environmental Protection
Agency (EPA) through Interagency Agreement Number DW89932112-01-2 to the U.S. Department of Energy, it has not been subjected
to EPA review and therefore does not necessarily reflect the views of EPA and no official endorsement should be inferred. 相似文献
810.
A. Bleed H. P. Nachtnebel I. Bogardi R. J. Supalla 《Journal of the American Water Resources Association》1990,26(3):479-487
ABSTRACT: Two case studies highlighting the institutional arrangements and decision-making processes used to attempt to allocate water on large scale river systems in two countries are presented. In both cases the implementation of river plans has been blocked by conflicts between those who wish to use water for irrigation, hydropower, or municipal purposes and those who wish to maintain instream flows for fish and wildlife. To date conflict has blocked the implementation of a large hydropower scheme on the Danube River, downstream from Vienna, Austria, and the construction of municipal and agricultural projects, as well as the relicensing of an existing hydropower facility on the Platte River in Nebraska. Analysis of the decision-making processes and institutional settings of both cases led to the identification of problem areas and development of recommendations that would support the achievement of compromise solutions for management. 相似文献