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971.
Xiaoliang LI Xiaomin CHEN Xia LIU Lianchuan ZHOU Xinqiang YANG 《Frontiers of Environmental Science & Engineering》2012,6(2):195-203
Soil low-molecular-weight (LMW) organic acids play important roles in the soil-forming process and the cycling of nutrients in Karst regions. In this study, we quantified the contents of LMW organic acids (including lactate, acetate, formate, malate, and oxalate) in soil solution over the Karst region of Guizhou Province, China using ion chromatography. The concentration of total LMW organic acids in topsoil solution ranged from 0.358 to 1.823 μmol·g-1, with an average of 0.912 μmol·g-1. The mean concentrations of lactate, acetate, formate, malate, and oxalate were 0.212±0.089, 0.302±0.228, 0.301±0.214, 0.014±0.018 and 0.086±0.118 μmol·g-1, respectively. There were also significant difference in the contents of these acids among four phases of rocky desertification, and their concentrations decreased with the aggravation of rocky desertification. The concentrations of the LMW organic acids were significantly positive correlated each other. Significant positive correlations were also observed among individual LMW organic acids in soil solution, and between them and soil available P, available K, exchangeable Ca, respectively. Furthermore, the concentrations of LMW organic acids were significantly positively correlated with inorganic anions (chlorides, nitrates, and sulfates) in Karst topsoil solution. Therefore, the concentrations of soil LMW organic acids might be one of driving force in the Karst rock desertification process in Guizhou Province. 相似文献
972.
Economic analysis of optimal ecosystem management in the presence of a threshold has typically ignored the potential for induced behavioral responses. This paper contributes to the literature on non-convex ecosystem management by considering the implications of a particular behavioral response in a regional economy – that of amenity-led growth – to changes in ecosystem services generated by a lake ecosystem subject to a eutrophication threshold. The essential policy challenge is to achieve optimal levels of lake nutrients and urbanization given that improvements to water quality will induce additional migration and urbanization in the region with attendant ecological impacts. We show that policies that ignore the recursive relationship between urbanization and water quality unintentionally exacerbate boom-bust cycles of regional growth and decline and risk pushing the system towards long-run economic decline. In contrast, the optimal policy accounts for the behavioral feedbacks to improved ecosystem services, and balances regional growth and ecological degradation. 相似文献
973.
974.
以南京江北新区分流制雨水管道沉积物为研究对象,考察不同粒径沉积物中铵态氮(NH3-N)和硝态氮(NO3--N)干期分布特征,分析其随干期长度的变化关系,并探讨沉积物理化性质及微生物菌群结构对NH3-N和NO3--N干期分布的影响.结果表明:粒径≤0.075mm的沉积物中NH3-N占比最高(交通区30.8%,商业区36.7%);交通区粒径≤0.075mm的沉积物中NO3--N占比最高(33.0%),而商业区粒径0.075~0.15mm沉积物中NO3--N占比最高(34.4%);干期长度与交通区0.075~0.15mm粒径段的沉积物中NO3--N含量及商业区粒径≥0.3mm的沉积物中NH3-N含量之间的相关性均最显著;雨水管道沉积物中NH3-N和NO3--N的干期分布与O-H和N-H等官能团、表面极性和亲水性、微观形貌等有一定关联;交通区雨水管道沉积物中Gemmobacter等反硝化优势菌种(相对丰度总和为20.15%)对NO3--N干期分布影响更显著. 相似文献
975.
976.
In China, although improvements to the pesticide registration process have beenmade in last thirty years, no occupational exposure data are required to obtain a commercial license for a pesticide product. Consequently, notably little research has been conducted to establish an exposure assessment procedure in China. The present study monitored the potential dermal operator exposure from knapsack electric sprayer wheat field application of imidacloprid in Liaocheng City, Shandong Province and in Xinxiang City, Henan Province, China, using whole-body dosimetry. The potential inhalation exposure was determined using a personal air pump and XAD-2 sample tubes. The analytical method was developed and validated, including such performance parameters as limits of detection and quantification, linear range, recovery and precision. The total potential dermal and inhalation exposures were 14.20, 16.80, 15.39 and 20.78 mL/hr, respectively, for the four operators in Liaocheng and Xinxiang, corresponding to 0.02% to 0.03% of the applied volume of spray solution. In all trials, the lower part (thigh, lower leg) of the body was the most contaminated, accounting for approximately 76% to 88% of the total exposure. The inhalation exposure was less than 1% of the total exposure. Such factors as the application pattern, crop type, spray equipment, operator experience and climatic conditions have been used to explain the exposure distribution over the different parts of the body. As indicated by the calculated Margin of Exposure, the typical wheat treatment scenarios when a backpack sprayer was used are considered to be safe in terms of imidacloprid exposure. 相似文献
977.
为了准确分析影响行人交通事故严重程度的各项因素,引入累积Logistic模型研究人、车、路、环境及事故特征与行人事故严重程度之间的关系.以美国北卡罗来纳州夏洛特市2016年的行人交通事故数据为样本,通过聚类压缩、共线性检验和预测力分析,从人、车、路、环境及事故特征5个方面选取16个因素作为自变量,事故严重程度作为因变量,构建行人交通事故严重程度预测模型来分析仅财产损失事故、受伤事故和死亡事故的影响因素,并引入弹性分析量化各显著因素的影响程度,检验结果显示模型拟合良好.结果表明,在0.05的显著性水平下,事故形式、事故发生时段、车辆类型、照明条件、行人年龄段、行人饮酒情况6个因素与事故严重程度显著相关.最后针对性地提出了行人事故预防对策.研究结果有助于交通管理者采取合理的策略来降低行人交通事故严重程度. 相似文献
978.
为充分解析文本形式的危化品事故案例,探讨事故类型与大量事故致因间的因果关联,从化工行业入手,通过扎根理论对175起危化品事故案例进行因素提取,共确定5个子系统、19个因素、80个子因素,提出基于事故生命周期的事故致因框架;在此基础上,提出改进的Gra-Apriori算法,以解决经典的Apriori无法考虑属性类别关系的... 相似文献
979.
速灭菊酯在水稻-水-鱼系统中的动态 总被引:11,自引:1,他引:11
采用同位素示踪技术和模拟生态系统试验法,对水田施用速灭菊酯后对邻近水域的污染、水域中鱼类对速灭菊酯残留物的浓缩和排除等进行了研究,结果表明,在田表水中,残留物浓度随处理后时间而迅速降低。水系中淤泥对水中残留物有明显的吸附净化作用,鱼对水中速灭菊酯残留物的摄取和排除均很迅速。 用二室模型对速灭菊酯残留物在田表水中的消失、用一级输入和输出的单室模型对鱼体中残留物浓度随时间的变化动态研究表明,在田表水中,土壤对水中残留物起着强烈的吸附净化作用;在水系中,鱼体中残留物浓度的消长主要取决于残留物自身在水中的消失速率,只是在前期同时依赖于鱼体对残留物的排除效应,鱼体的摄入常数只对鱼体累积浓度最大值及到达最大值的时间T_m产生影响。 相似文献
980.
In this study, organic fractions, namely, humic acid, fulvic acid, hydrophobic base and neutral, and hydrophilic acid, base, and -neutral, were extracted from source water. First, the characteristics of the organic fractions, such as carboxylic acidity, phenolic acidity, ultraviolet absorbance, and aromatic content, were analyzed. Further, a systematic study was carried out to the by-products obtained when organic fractions, to which various amounts of bromide had been added, were oxidized with ozone. Samples after ozonation were analyzed for several brominated organics. The results indicate that the characteristics of the aquatic organic matter, including carboxylic/phenolic acidity, aromatic/aliphatic content, and ultraviolet absorbance, appear to affect the formation of halogenated organics. In general, hydrophobic organics having higher phenolic acidity, aromatic content, and ultraviolet absorbance have higher ozone consumption and produce higher concentrations of brominated organics than hydrophilic organics. It was also found that humic acid demonstrated the highest bromoform (CHBr(3)), dibromoacetic acid (DBAA), and 2,4-dibromophenol (2,4-DBP) formation, whereas hydrophilic neutral produced less CHBr(3) and 2,4-DBP than the rest of the organic fractions but produced the highest amount of dibromoacetone (DBAC) and dibromoacetonitrile (DBAN). 相似文献