Voltammetric determination of the herbicide Bifenox in drinking and river water using a silver solid amalgam electrode

A new method for the determination of submicromolar and nanomolar concentrations of herbicide Bifenox using differential pulse voltammetry at a mercury meniscus modified silver solid amalgam electrode is described. This new type of working electrode is non-toxic, environmentally friendly, and compatible with principles of green analytical chemistry, and its surface can be easily electrochemically renewed in the case of passivation. The newly developed direct differential pulse voltammetric determination of Bifenox gives limit of determination 6.7·10^?7 and 6.9·10^?7?M in drinking and river water, respectively. Both the selectivity and the sensitivity can be further increased by preliminary separation and preconcentration using solid phase extraction. This combination enables to reach limit of determination 0.9?×?10^?9 and 1.5?×?10^?9?M for drinking and river water, respectively. Because of lower running and investment costs, this electroanalytical method can be used for large scale monitoring of possible water contamination with tested herbicide.     

Gravity currents in two-layer stratified media

An analytical, experimental and numerical study of boundary gravity currents propagating through a two-layer stratified ambient of finite vertical extent is presented. Gravity currents are supposed to originate from a lock-release apparatus; the (heavy) gravity current fluid is assumed to span the entire channel depth, H, at the initial instant. Our theoretical discussion considers slumping, supercritical gravity currents, i.e. those that generate an interfacial disturbance whose speed of propagation matches the front speed, and follows from the classical analysis of Benjamin (J Fluid Mech 31:209?C248, 1968). In contrast to previous investigations, we argue that the interfacial disturbance must be parameterized so that its amplitude can be straightforwardly determined from the ambient layer depths. Our parameterization is based on sensible physical arguments; its accuracy is confirmed by comparison against experimental and numerical data. More generally, measured front speeds show positive agreement with analogue model predictions, which remain strictly single-valued. From experimental and numerical observations of supercritical gravity currents, it is noted that this front speed is essentially independent of the interfacial thickness, ??, even in the limiting case where ?? = H so that the environment is comprised of a uniformly stratified ambient with no readily discernible upper or lower ambient layer. Conversely, when the gravity current is subcritical, there is a mild increase of front speed with ??. Our experiments also consider the horizontal distance, X, at which the front begins to decelerate. The variation of X with the interface thickness and the depths and densities of the ambient layers is discussed. For subcritical gravity currents, X may be as small as three lock lengths whereas with supercritical gravity currents, the gravity current may travel long distances at constant speed, particularly as the lower layer depth diminishes.     

贵阳市区地表灰尘重金属污染分析与评价

以贵阳市区为研究地点,采集了贵阳城区工业区、交通区、商业区、居民区、文教区、公园广场、对照区7个类别共80个采样点的地表灰尘,分析了地表灰尘重金属在不同区域的分布特征,并分析其可能来源。最后,应用潜在生态危害指数法对6个功能区（工业区、交通区、商业区、居民区、文教区、公共区）样品中重金属的潜在生态危害进行评价。结果表明：贵阳市地表灰尘重金属的平均质量分数均高于贵州省土壤环境背景值,Cd、As、Cu污染质量分数都超过4倍以上背景值水平,其余重金属污染水平大多处于1~3倍背景值水平。就单个重金属潜在生态危害系数平均值来看,地表灰尘的潜在生态危害最大的是Hg,其次是Cd,生态危害最低的是Cr。6个功能区生态危害水平均属于强生态危害水平,其中工业区和公共区生态危害水平最高。     

水生植物种植场磷素分布特征与植物吸收

研究了水生植物种植场水体、沉积物及植物的磷含量及分布特征,结果表明进水的P浓度高于V类水标准,水生植物种植区内的由于受到沉淀、吸附及植物吸收的影响,水体P浓度远低于进水,水体不同形态P与TP之间呈现良好的相关关系;沉积物的TP质量分数在335～672 mg.kg-1之间,表层沉积物P质量分数是影响底层沉积物P质量分数的主要因素之一,沉积物中的TP和IP、OP之间同样存在相关性;水生植物对P均具有较好的吸收富集能力,不同水生植物的迁移系数均在0.5以上,平均为0.82,其中的黄花蔺(Limnocharis flava)与欧慈菇(Sagittaria sagittifolia)显示对P的良好吸收和迁移能力。基于本次调查的水生植物P质量分数统计分析表明,95%的水生植物地上部P质量分数正常值范围在1 415～4 947mg.kg-1之间,而地下部的P质量分数正常值范围在2 178～5 702 mg.kg-1之间。     

DNDC模型对川中丘陵区稻田CH_4、N_2O排放的模拟对比分析

利用IKONOS高分辨率(1m)卫星遥感图,进行典型抽样和地形→土地利用→土地覆盖→综合信息提取的方法,选定了代表川中丘陵区类特征的四川省金堂县为研究区域,通过对研究区域中不同固定耕作制度下代表性田块的选取,于2005年5月—2006年5月对田块管理者进行作物田间管理、作物产出等农业生产实际情况调查和分析,进行土壤理化性状、水样的测定,并结合当地的气象资料,利用DNDC模型模拟川中丘陵区不同耕作制度下稻田温室气体的排放情况。结果表明:冬水田-水稻田(PF)水稻生长期CH4排放通量为2.24 kg.hm-2.d-1,占年排放量的80.73%;水稻生长期和冬闲期N2O通量分别为0.033和0.003 6 kg.hm-2.d-1,水稻生长期排放量为4.28 kg.hm-2,占年总排放量的83.59%。CH4和N2O排放量在水稻整个生季节存在明显的互为消长关系。油菜-小麦田(RR)水稻生长期CH4排放通量为1.16 kg.hm-2.d-1,是休闲期的20.71倍,水稻生长期CH4排放量占年排放量的90.48%;水稻生长期和非水稻生长期N2O排放通量分别为0.070和0.027 kg.hm-2.d-1,水稻生长期N2O...     

HgCl2对斑马鱼SOD,AChE酶活性和基因相对转录量的影响

以HgCl2为实验毒物,研究其对斑马鱼的毒性效应,经染毒后,分别在第1天和第7天取斑马鱼的肌肉测定超氧化物歧化酶(SOD)、乙酰胆碱酯酶(AChE)活性,半定量RT-PCR检测肌肉中乙酰胆碱酯酶、细胞色素P450(CYP 1A)和超氧化物歧化酶(Cu/Zn-SOD)基因的相对转录量.结果显示HgCl2对斑马鱼的毒性很强...     

Allozyme polymorphisms in horseshoe crabs, Carcinoscorpius rotundicauda, collected from polluted and unpolluted intertidal areas in Peninsular Malaysia

It has been widely reported that allozyme frequency variation is a potential indicator of heavy metal-induced impacts in aquatic populations. In the present study, wild populations of horseshoe crab (Carcinoscorpius rotundicauda) were collected from contaminated and uncontaminated sites of Peninsular Malaysia. By adopting horizontal starch gel electrophoresis, seven enzyme systems were used to study allozyme polymorphisms. Nine polymorphic loci were observed in C. rotundicauda. The relationships of allozyme variations with the concentrations of Cd, Cu, Ni, and Zn in sediments and in muscle tissues of horseshoe crabs were determined. Based on genetic distance, the lower mean value of Nei??s D (0.017) indicated that both of the contaminated populations of Kg. Pasir Puteh and Kuala Juru were very closely related when compared to the relatively uncontaminated Pantai Lido population. Higher heterozygosities were shown by the contaminated populations when compared to the uncontaminated population. Different allelic frequencies could be observed for the aldolase (ALD; E.C. 2.7.5.1) locus between the contaminated and uncontaminated populations of C. rotundicauda. The dendrogram of genetic relationships of the three populations of C. rotundicauda showed the same clustering pattern as the dendrograms are based on heavy metals in the sediments and in the horseshoe crabs?? abdominal muscles. From the F statistics, the present study showed that the three populations of horseshoe crabs were considered to have undergone moderate genetic differentiation with a mean F _ST value of 0.092 .The current results suggest that allozyme polymorphism in horseshoe crabs is a potential biomonitoring tool for metal contamination, although further validation is required.     

Concentration and distribution characteristic of main toxic metals in suspended particle material in Nanjing reach, Changjiang River

Six stations in the lower reach region of Changjiang River within Baguazhou Island, Nanjing reach were chosen to investigate the toxic metals pollution characteristic in suspended particle material (SPM). SPM concentration, as well as reflectance spectroscopy characteristic, toxic metal concentrations, and lead isotopes of suspended particle material were studied. SPM concentrations were obtained from fluvial cross-sectional sampling near the surface (20 cm) and the study presents the cross-sectional averages. SPM concentrations varied around 170?C300 mg L^???1. Reflectance spectroscopy measurements differed from each other over each cross-section but no common pattern characterizing the cross-sectional behavior of the measurements was observed. The metal concentrations in the SPM decreased in the sequence: Mn > Zn > Cu > Cr > Pb > Cd. The result of lead isotopes analysis proved that lead isotopes composition in SPM are mainly produced by natural contributions and influenced by anthropogenic activity at the same time.     

Characteristics of atmospheric non-methane hydrocarbons in Foshan City, China

Foshan is the most air-polluted city in Pearl River Delta. Non-methane hydrocarbons (NMHCs) were investigated for the first time in Foshan in winter 2008. Ethene, ethane, ethyne, propane, i-pentane, and toluene were the most abundant hydrocarbons and observed to be higher in Foshan than those in many other cities in China. Different from other cities, ethene and ethane were observed to be the two highest compounds in Foshan. Generally, the most abundant hydrocarbons showed high mixing ratios in the morning (0930-1030 hours), decreased to the lowest level in the afternoon (1430-1530 hours), and increased to higher value in the evening (1930-2030 hours). But i-pentane exhibited a different diurnal pattern with the highest level (13.4 ± 5.8 ppbv) in the afternoon, implying the acceleration of solvent evaporation resulting from higher temperature. Correlation coefficients (R(2)?= 66% for n = 6 at 95% confidence level) of the individual hydrocarbons with ethyne and i-pentane indicated vehicular emissions were the main sources of ethene, propene, i-butene, isoprene, benzene and toluene, while gasoline evaporation was responsible for n-pentane, n-hexane, and n-heptane. The good correlation of most of the hydrocarbons with ethyne, indicating vehicular emissions, were the main sources of NMHCs. B/T ratio was 0.36 ± 0.06, implying vehicular emissions acted as the major contributors as well as additional emissions of toluene emitted from solvent usage. According to investigation, it also suggested that LPG leakage was the main source of propane, while NG leakage was responsible for ethane in Foshan City.     

Distribution and chemical partitioning of heavy metals in marine near-shore sediment cores: a case study from the Xugou, Lianyungang, China

The concentrations and chemical partitioning of heavy metals (Co, Cr, Ni, Zn, Cu, and Pb) in the marine near-shore sediment cores were investigated. Typically, the mean concentrations from Core B sediment samples were 98.6, 21.1, 47.0, 46.4, 107.6, and 31.9 mg kg^???1 for Cr, Co, Ni, Cu, Zn, and Pb, respectively. The heavy metal concentrations were normalized to commonly used reference elements Al, Li, Sc, and total organic carbon. Based on Pearson coefficients, Li was found to be a good normalizer for Co (r?= 0.974), Cr (r?= 0.967), Ni (r?= 0.898), and Zn (r?= 0.929) in 80 sediment samples from three sampling sites. However, the correlation coefficients between Li and Cu, and Li and Pb were relatively low. Multivariate statistic approaches (Principal Component Analysis and Cluster Analysis) were adopted for data treatment, allowing the identification of two main factors controlling the heavy metal variability in the sediments. Heavy metals in the enrichment sections were evaluated by a sequential extraction method for possible chemical forms in sediments. The results showed that the residual, Fe/Mn oxides and Organic/sulfide fractions were dominant geochemical phases in the enriched sections, indicating low bioavailability of heavy metals in sediments.