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971.
Chen Ziang Ren Gengbo Ma Xiaodong Ding Ye Hui Yunmin Qin Pingping Xu Zhuoqi Gu Xiujun Yuan Fang Liu Yanhai 《Environmental science and pollution research international》2020,27(31):38580-38590
Environmental Science and Pollution Research - In this study, the occurrence, spatial distribution, sources, and ecological risks of perfluoroalkyl substances (PFASs) in the surface waters of the... 相似文献
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Emergy studies have suffered criticism due to the lack of uncertainty analysis and this shortcoming may have directly hindered the wider application and acceptance of this methodology. Recently, to fill this gap, the sources of uncertainty in emergy analysis were described and analytical and stochastic methods were put forward to estimate the uncertainty in unit emergy values (UEVs). However, the most common method used to determine UEVs is the emergy table-form model, and only a stochastic method (i.e., the Monte Carlo method) was provided to estimate the uncertainty of values calculated in this way. To simplify the determination of uncertainties in emergy analysis using table-form calculations, we introduced two analytical methods provided by the Guide to the Expression of Uncertainty in Measurement (GUM), i.e., the Variance method and the Taylor method, to estimate the uncertainty of emergy table-form calculations for two different types of data, and compared them with the stochastic method in two case studies. The results showed that, when replicate data are available at the system level, i.e., the same data on inputs and output are measured repeatedly in several independent systems, the Variance method is the simplest and most reliable method for determining the uncertainty of the model output, since it considers the underlying covariance of the inputs and requires no assumptions about the probability distributions of the inputs. However, when replicate data are only available at the subsystem level, i.e., repeat samples are measured on subsystems without specific correspondence between an output and a certain suite of inputs, the Taylor method will be a better option for calculating uncertainty, since it requires less information and is easier to understand and perform than the Monte Carlo method. 相似文献
974.
贫营养型水库中罗非鱼对浮游植物的影响:围隔实验 总被引:1,自引:0,他引:1
于2009年9~11月在贫营养型的大型深水水库(流溪河水库)中进行了围隔(体积约为85 m3)实验,分析了罗非鱼对浮游植物的影响.根据水库中现有鱼类的生物量,设置加鱼处理组(2 g/m3)和无鱼对照组两组.每组有3个重复,实验开始后每周采样一次,测定水质与采集浮游生物定性和定量样品.实验结果表明,加鱼处理组和对照组的总氮、可溶性无机氮没有明显差别,实验后期的总磷与正磷有一定差别,处理组略高于对照组.加鱼处理组浮游植物丰度及生物量、叶绿素a的含量显著高于对照组(P<0.05),且透明度低于对照组,个体小于30μm的浮游植物种类的丰度与生物量较明显增加,浮游动物丰度显著低于对照组(P<0.05),但是生物量差异不显著(P>0.05).总的来说,在贫营养条件下,低生物量的罗非鱼对水库浮游植物群落结构仍有着明显的影响,罗非鱼排泄产生的上行效应大于摄食产生的下行效应. 相似文献
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976.
Marmolejo-Rodríguez AJ Sánchez-Martínez MA Romero-Guadarrama JA Sánchez-González A Magallanes-Ordóñez VR 《Journal of environmental monitoring : JEM》2011,13(8):2182-2189
Extensive waste deposits (tailings) and ash from the ignition oven of the abandoned gold mine of mining district El Triunfo (MD-ET) in Baja California Sur, Mexico have released trace elements into the sediments of the Hondo-Las Gallinas-El Carrizal arroyo, which connects to the Pacific Ocean through an evaporitic basin. Migration of these elements through the arroyo is mainly caused by winds or tropical hurricanes that occur sporadically during the summer and cause the otherwise dry arroyo to overflow. To evaluate the concentration and distribution of the elements As, Hg, Pb, and Zn along the 48 km arroyo, surface sediments were collected from 26 sites, ranging from close to the MD-ET to the mouth of the arroyo at the Pacific Ocean. Concentrations in tailings and ash were for As 8890 and 505?000 mg kg(-1); for Hg 0.336 and 54.9 mg kg(-1); for Pb 92,700 and 19,300 mg kg(-1); and for Zn 49,600 and 1380 mg kg(-1). The average of the Normalized Enrichment Factor (Av-NEF) in surface sediments, calculated using background levels, indicates that the sediments are severely contaminated with As and Zn (Av-NEF = 22), Pb (Av-NEF = 24) and with a moderate contamination of Hg (Av-NEF = 7.5). The anthropogenic influence of those elements is reflected in the arroyo sediments as far as 18 km away from the MD-ET, whereas the samples closest to the discharge into the Pacific Ocean show a natural to moderate enrichment for As and Zn and low or no enrichment for Hg and Pb. A principal components analysis identified four principal components that explained 90% of the total variance. Factor 1 was characterized by a high positive contribution of the anthropogenic source elements, especially As, Pb, and Zn (37%), whereas Factor 2 was strongly correlated with the oxy-hydroxides of Fe and Mn (27%). Factor 3 was correlated with Li (16%) and Factor 4 with Al (10%), which indicates more than one source of lithogenic composition, though they played a minor role in the distribution of the elements. 相似文献
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978.
高压电晕放电对五氯酚的降解研究 总被引:1,自引:1,他引:0
研究了放电电压、溶液pH等因素对高压电晕放电降解PCP效果的影响,并对高压电晕放电处理PCP的动力学进行了初步探讨,同时对高压电晕放电降解PCP的COD和TOC的变化进行了分析。结果表明:放电电压和溶液pH值对PCP降解性能影响很大,放电电压和溶液pH值越高,PCP的降解速度越快。当溶液pH值为11.2、PCP初始质量浓度40 mg/L、电晕放电电压为25 kV时,经30 min电晕放电,PCP的降解率达90%以上,电晕放电降解PCP的反应符合一级反应动力学。在氧化过程中PCP可能转化为苯醌等中间产物,TOC几乎无变化,PCP分解成的小分子有机物使COD升高,可生化性提高。 相似文献
979.
沈阳市冬季一次严重污染天气过程成因分析 总被引:1,自引:1,他引:0
为探讨沈阳市冬季重污染天气的初步成因。以2013年1月11日~16日沈阳市发生的一次严重污染天气为例,利用中国气象局的MICAPS系统和美国的HYSPLT模式,从污染形成的天气背景、污染物扩散受地形的影响情况以及外来污染物输送的气流轨迹等几方面综合分析,从而探讨此次严重污染过程的成因:长白山小高压和西部倒槽双重系统的控制下,地面吹东北风,风速较小,湿度大,不利于污染物的水平扩散;有较强接地逆温存在时,不利于污染物的垂直扩散,导致近地面污染物累积;受来自于北部和东北部低层气流的影响,将内蒙古、辽宁东北部的污染物携带到沈阳地区汇聚。 相似文献
980.