A complete set of procedure for determination of multiresidue of pesticides in vegetables was presented in this paper.The complete set of procedure included three steps:bioassay,cholinesterase inhibition and GLC analysis.The samples could be identified to be contaminated with pesticides if 5% of house flies was knocked down in 50 tested house flies. Those samples contaminated with pesticides needed to be detected by AChE inhibition method.The qualitative and quantitative analyses were carried out by GLC.Recoveries ranged from 83.7% in Chinese cabbages to 105.6% in tomatoes for pyrethroids,and 84.0% in tomatoes to 102.7% in sweetbell redpeppes for organophosphorus compounds.Coefficients of variations ranged from 0.59% to organophosphorus compounds.Coefficients of variations ranged from 0.59% to 7.87% for pyrethroids. and 0.33% to 9.88% for organophosphorus compounds with vegetables. The complete set of procedure has been used successfully to analyze 7000 samples collected in Beijing. About 1% of the samp 相似文献
Black carbon (BC) in surface sediments from Henan section of Yellow River and Huaihe River, China, was determined. Average content of BC in Huaihe River was 0.33%, higher than that in Yellow River (n?=?23) with mean value of 0.15%. Distribution patterns of BC in Yellow River and Huaihe River were similar, namely that tributaries had higher BC content than main stream. In addition, BC content in the mainstream of Yellow River and Huaihe River decreased with altitude. The BC content presented a significant positive correlation with clay (r?=?0.672; p?<?0.01) content in Yellow River, while neither did in Huaihe River. The ratio of BC/TOC ranged from 1.8–57.4% (median 29.6%), evidencing pyrogenic fossil fuel source of BC in Yellow River. Relatively low values of BC/TOC in Huaihe River (5.3%–28.8%, median 7.5%,) reflected that the origin of BC is from burning of biomass. In addition, Pearson rank correlation analysis showed that BC was in strong correlation with lighter PAH in Yellow River, while BC was in significant correlation with heavier PAH in Huaihe River. The ratio of BC/TOC indicated that BC in Yellow River mainly came from fossil fuel combustion, while BC in Huaihe River was primarily from biomass burning. 相似文献
The levels of metals in sediments of urban river ecosystems are crucial for aquatic environmental health and pollution assessment. Yet little is known about the interaction of nutrients with metals for environmental risks under contamination accumulation. Here, we combined hierarchical cluster, correlation, and principal component analysis with structural equation model (SEM) to investigate the pollution level, source, toxicity risk, and interaction associated with metals and nutrients in the sediments of a river network in a city area of East China. The results showed that the pollution associated with metals in sediments was rated as moderate degree of contamination load and medium-high toxicity risk in the middle and downstream of urban rivers based on contamination factor, pollution load index, and environmental toxicity quotient. The concentration of mercury (Hg) and zinc (Zn) showed a significant correlation with toxic risks, which had more contribution to toxicity than other metals in the study area. Organic nitrogen and organic pollution index showed heavily polluted sediments in south of the study area. Though correlation analysis indicated that nutrients and metals had different input zones from anthropogenic sources in the urban river network, SEM suggested that nutrient accumulation indirectly intensified toxicity risk of metals by 13.6% in sediments. Therefore, we suggested the combined consideration of metal toxicity risk with nutrient accumulation, which may provide a comprehensive understanding to identify sediment pollution.
Toxicity rate of metals in sediments from urban river network indirectly intensified by nutrients accumulation
