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991.
992.
The discrimination of excess toxicity from narcotic effect plays a crucial role in the study of modes of toxic action for organic compounds. In this paper, the toxicity data of 758 chemicals to Daphnia magna and 993 chemicals to Tetrahymena pyriformis were used to investigate the excess toxicity. The result showed that mode of toxic action of chemicals is species dependent. The toxic ratio (TR) calculated from baseline model over the experimentally determined values showed that some classes (e.g. alkanes, alcohols, ethers, aldehydes, esters and benzenes) shared same modes of toxic action to both D. magna and T. pyriformis. However, some classes may share different modes of toxic action to T. pyriformis and D. magna (e.g. anilines and their derivatives). For the interspecies comparison, same reference threshold need to be used between species toxicity. The excess toxicity indicates that toxicity enhancement is driven by reactive or specific toxicity. However, not all the reactive compounds exhibit excess toxicity. In theory, the TR threshold should not be related with the experimental uncertainty. The experimental uncertainty only brings the difficulty for discriminating the toxic category of chemicals. The real threshold of excess toxicity which is used to identify baseline from reactive chemicals should be based on the critical concentration difference inside body, rather than critical concentration outside body (i.e. EC50 or IGC50). The experimental bioconcentration factors can be greatly different from predicted bioconcentration factors, resulting in different toxic ratios and leading to mis-classification of toxic category and outliers. 相似文献
993.
994.
伴随着我国城镇化进程的不断加快,城市环境污染问题备受关注。本文以城镇居民生活垃圾污染行为为起点,通过比较居民与政府目标函数,首先从理论上做出判断,城镇人口数量增加以及居民生活质量提高均会导致城市生活垃圾数量增长,从而对城市环境产生影响。随后,进一步采取Panel data的分析方法,以我国2004-2008年省级面板数据为样本,从城市生活垃圾污染的角度对我国城镇人口增长、居民收入水平与城市环境间的关系进行计量检验。结果显示:我国城市生活垃圾产生数量分别与城镇人口增长、居民收入水平间存在着长期正向协整关系,即在我国城镇化水平和居民生活质量不断提升的背景下,城市生活垃圾数量的增长以及对城市环境的污染存在着内在必然性;另外,我国城市生活垃圾数量的自发增长对平均增长的偏离逐年下降,可见,存在政策、制度、行为等外生因素抑制我国城市生活垃圾数量的增长。最后,文章从生活垃圾控制和处理的角度,就改善我国城市环境和促进城市环境可持续发展提出了简要的政策建议。 相似文献
995.
天津城郊土壤中PAHs含量特征及来源解析 总被引:4,自引:1,他引:3
以天津市郊环城四区为研究对象,系统采集了环城四区95个表层土壤样品,利用高效液相色谱仪对16种PAHs进行分析测定,结果表明,西青、东丽、津南和北辰土壤中16种PAHs的总量范围分别为62.6~1 994.9、36.1~4 074.7、20.1~2 502.5、22.1~707.7μg/kg;平均含量分别为445.8、841.8、509.5、242.5μg/kg。四区中都以高环多环芳烃为主,西青、东丽、北辰和津南高环多环芳烃分别占多环芳烃总比例的45.4%、42.2%、38.8%和38.7%。空间分析的结果表明,靠近天津市市区样点土壤中多环芳烃的含量要明显高于远离市区土壤中多环芳烃的含量。利用环数PAHs的相对丰度和比值法对天津市郊环城四区土壤中多环芳烃的污染来源进行了解析,研究区土壤监测样点的PAHs主要来自燃烧源,少部分来自石油类来源或几种污染源的共同复合累加的作用。 相似文献
996.
废水处理用聚乙烯生物填料表面改性与表征研究 总被引:6,自引:1,他引:5
采用化学氧化-铁离子覆盖和化学氧化-表面接枝2种方法对聚乙烯生物填料进行表面改性,并使用接触角、扫描电镜及X射线光电子能谱等手段对改性前后的填料表面进行表征,同时还考察其在废水处理中的挂膜速度和处理效果。结果表明,2种改性方法都能使填料表面形成腐蚀坑而增加了表面粗糙度,并引入基团使填料表面呈正电性,使得填料的亲水性与生物亲和性增强,有利于微生物的粘附。2种改性方法可将挂膜时间分别缩短37.5%和60%,挂膜量分别提高54.8%和76.1%,COD的去除率也分别提高10.63%和8.64%。 相似文献
997.
Sheng XF Xia JJ Jiang CY He LY Qian M 《Environmental pollution (Barking, Essex : 1987)》2008,156(3):1164-1170
Two lead (Pb)-resistant endophytic bacteria were isolated from rape roots grown in heavy metal-contaminated soils and characterized. A pot experiment was conducted for investigating the capability of the two isolates to promote the growth and Pb uptake of rape from Pb-amended soil. The two isolates were identified as Pseudomonas fluorescens G10 and Microbacterium sp. G16 based on the 16S rDNA gene sequence analysis. Strains G10 and G16 exhibited different multiple heavy metal and antibiotic resistance characteristics and increased water-soluble Pb in solution and in Pb-added soil. Root elongation assays demonstrated increases in root elongation of inoculated rape seedlings compared to the control plants. Strain G16 produced indole acetic acid, siderophores and 1-aminocyclopropane-1-carboxylate deaminase. Increases in biomass production and total Pb uptake in the bacteria-inoculated plants were obtained compared to the control. The two strains could colonize the root interior and rhizosphere soil of rape after root inoculation. 相似文献
998.
999.
1000.
Haiquan Zhao Jie Hong Xiaohong Yu Xiaoyang Zhao Lei Sheng Yuguan Ze Xuezi Sang Suxin Gui Qingqing Sun Ling Wang Fashui Hong 《Chemosphere》2013
Environmental pollution from lanthanides (Ln) has been recognized as a major problem due to a grab exploitation of Ln mine in China. Exposure to Ln has been demonstrated to cause the nephrotoxicity, very little is known about the mechanism of oxidative damage to kidney in animals. In order to understand Ln-induced nephrotoxicity, various biochemical and chemical parameters were assayed in mouse kidney. Intragastric exposures of LaCl3, CeCl3, and NdCl3 at doses of 2, 5, and 10 mg kg−1 BW for 90 consecutive days caused nephritis or epithelial cell necrosis and oxidative stress to kidney. An increase in coefficients of the kidney, La, Ce, and Nd accumulation and histopathological changes in the kidney could be observed, followed by increased reactive oxygen species production and peroxidation levels of lipid, protein and DNA, and decreased activities of superoxide dismutase, catalase, glutathione-S-transferase and glutathione reductase as well as antioxidants such as glutathione, ascorbic acid and thiol contents. Furthermore, La, Ce, and Nd significantly suppressed expression of genes and proteins of these antioxidative enzymes in mouse kidney. In addition, kidney functions were disrupted, including an increase of the creatinine, and reductions of uric acid, urea nitrogen, calcium and phosphonium. These findings suggest that nephritis generation or epithelial cell necrosis in mice following exposure to Ln is closely associated with oxidative stress. Of these damages, the most severe was in the Ce3+-exposed kidneys, next in the Nd3+-exposed kidneys, and the least in the La3+-exposed kidneys, which may be attributed to the 4f electron of Ln. 相似文献