Temporal trends and sources of PCDD/Fs, pentachlorophenol and chlornitrofen in paddy field soils along the Yoneshiro River basin, Japan

In order to understand the long-term behaviors of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), pentachlorophenol (PCP), and 2,4,6-trichlorophenyl-4′-nitrophenyl ether (chlornitrofen, CNP) in paddy soil, we measured their concentrations in paddy soil samples collected in 1982 and 1984 (1980s) and in 2000 and 2002 (2000s) from the Yoneshiro River basin, Japan. The concentrations of PCP and CNP decreased from the 1980s to the 2000s, whereas the concentrations of PCDD/Fs and their toxic equivalency (WHO2006-TEQ) remained. The major sources of PCDD/Fs in the paddy soil samples were attributed to impurities in PCP and CNP as a result of comparisons of homologue and congener profiles and principal component analysis. Based on the results of comparison of total input and remaining amount, it is estimated that more than 99% of PCP and CNP applied to the paddy fields had disappeared, whereas most of the applied PCDD/Fs and TEQ remained.     

Long‐Term Streamflow Response to Climatic Variability in the Loess Plateau,China1

Abstract: The Loess Plateau region in northwestern China has experienced severe water resource shortages due to the combined impacts of climate and land use changes and water resource exploitation during the past decades. This study was designed to examine the impacts of climatic variability on streamflow characteristics of a 12‐km² watershed near Tianshui City, Gansu Province in northwestern China. Statistic analytical methods including Kendall’s trend test and stepwise regression were used to detect trends in relationship between observed streamflow and climatic variables. Sensitivity analysis based on an evapotranspiration model was used to detect quantitative hydrologic sensitivity to climatic variability. We found that precipitation (P), potential evapotranspiration (PET) and streamflow (Q) were not statistically significantly different (p > 0.05) over the study period between 1982 and 2003. Stepwise regression and sensitivity analysis all indicated that P was more influential than PET in affecting annual streamflow, but the similar relationship existed at the monthly scale. The sensitivity of streamflow response to variations of P and PET increased slightly with the increase in watershed dryness (PET/P) as well as the increase in runoff ratio (Q/P). This study concluded that future changes in climate, precipitation in particular, will significantly impact water resources in the Loess Plateau region an area that is already experiencing a decreasing trend in water yield.     

有机高分子絮凝剂的应用与研究进展

絮凝沉淀法是水处理中的有效方法,絮凝剂的选择是该方法中的关键因素,根据其化学成分的不同,一般分为无机、有机、微生物絮凝剂三种。有机高分子絮凝剂由于其用量小、絮凝速度快和受外界因素影响小等优势得到广泛的应用。本文详细介绍了有机高分子絮凝剂的种类、使用情况及研究进展,并对有机高分子絮凝剂的发展趋势进行了展望。     

Occurrence and sources of polychlorinated dibenzo-p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls in surficial sediments of Lakes Superior and Huron

Concentrations and congener profile patterns of 2378-substituted PCDD/Fs and DLPCBs in offshore, nearshore and tributary sediments of Lakes Superior and Huron are reported, and spatial trends and source contributions assessed. PCDD/F concentrations ranged from 5 to 18 000 pg/g dw (Lake Superior) and 3 to 6100 pg/g dw (Lake Huron); DLPCBs ranged from 9 to 11 000 pg/g dw (Lake Superior) and 9 to 27 000 pg/g dw (Lake Huron). Our analysis indicated atmospheric deposition is a primary source to depositional areas of both lakes; however, greater PCDD/F and DLPCB concentrations were observed at several nearshore and tributary sites, and were attributed to corresponding land use in the watershed. Statistical analysis and pattern comparison suggested that industrial inputs mainly associated with wood treatment plants, pulp and paper mills, mining operations, and chlorine-based chemical manufacturing also contributed to contamination by PCDD/Fs and DLPCBs in certain nearshore and offshore areas of Lakes Superior and Huron.     

滇池北岸入湖河流水质变化趋势分析

文章采用WPI水污染指数法评价滇池北岸各片区河道的水质,并分析其变化趋势,同时采用pearson相关分析方法研究旱季和雨季各片区河道WPI指数变化趋势的相关度。结果表明:1988-2001年滇池北岸河道水质污染主要为减轻的趋势;2001-2007年随着昆明市的大规模扩张,其加重趋势非常明显;2007-2009年,随着河道水环境综合整治工程的大规模开展,又主要表现为减轻趋势,且旱季水质污染减轻的趋势比雨季明显,在纳入统计的5个片区河道中,旱季有4个片区河道水质好转,雨季有3个片区河道水质好转。这是由于2007-2009年间开展的河道水环境综合整治工程主要针对点源污染控制。此外,由于面源污染特征在5个片区中的4个片区都非常相似,雨季各片区河道WPI指数变化趋势的相关度比旱季高。     

中国西北地区持续干期日数时空变化特征

采用1961-2011 年111 个地面观测站逐日降水量资料,分析了中国西北地区近51 a 四季持续干期日数变化趋势。结果表明：近51 a 来西北全区春季和冬季持续干期日数都呈明显的下降趋势,冬季的下降幅度达到-1.6 d·(10 a)^-1,而夏季和秋季变化趋势不太明显。空间分布上该区大部分地区持续干期日数变化倾向率春季呈减少趋势,变化倾向率在-5.0～5.0d·(10 a)^-1之间;夏季不同的区域变化趋势不同;秋季西北西部呈减少趋势,而西北东部则呈增加趋势;冬季除陕西南部的关中平原和秦巴山地外,其他大部分地区呈减少趋势,变化倾向率在-6.0～3.0 d·(10 a)^-1之间。持续干期日数年代际变化和空间变化趋势在不同自然区变化趋势也存在差异。     

果园土壤有机氯农药残留的时间趋势研究

以天然荒地和蔬菜基地作为对照 ,于 1993年和 2 0 0 3年对北京市某果园中具有不同树龄的老果园和新果园的土壤有机氯农药 (HCH ,DDT)残留情况进行了定位监测 .结果表明 ,在禁用 2 0年后 ,土壤中的有机氯农药残留水平大幅度降低 ,其中老果园的有机氯农药残留浓度显著高于新果园 (P <0 0 5 ) .果园土壤有机氯残留浓度显著高于荒地和蔬菜基地对照 (P <0 0 5 ) .DDT是当地主要的有机氯污染物 ,利用绿色食品生产基地环境质量标准作为评价标准对该果园土壤的污染程度进行了评估 .评估结果表明 ,新果园的土壤质量能够满足绿色食品生产的要求 ,老果园由于土壤中DDT和HCH残留超标严重不适合作为绿色食品生产基地     

玉溪市降水化学特征及变化趋势分析

根据2004—2013年降水和环境空气监测资料,统计分析了玉溪市中心城区降水p H值的年变化、季节变化和月变化,结果表明:10年来玉溪市中心城区酸雨频率为1.14%,降水p H最低值4.96,最高值8.66。用spearman秩相关系数法检验分析,降水p H年均值呈平稳偏升趋势,降水p H维持在6.36~7.42,但降水电导率、SO2-4、NO-3、Ca2+、K+呈显著上升趋势;降水出现酸雨的频率按春、夏、秋递减,集中分布在3月、4月、7月、8月。降水酸型为燃煤型,降水阴离子的影响来源主要为工业、生活燃煤、石化燃料的燃烧及机动车排放的尾气;阳离子影响的主要来源为城市工地扬尘和裸露地表土壤尘埃。     

反渗透在水处理技术中的应用

简要介绍了反渗透的原理和常见流程,着重论述了反渗透在水处理技术中的应用,就其存在的问题和发展趋势作了初步的归纳和展望。     

1990～2017年中国地区气溶胶光学厚度的时空分布及其主要影响类型

为准确了解中国地区气溶胶光学特性,通过1990~2017年的MERRA2数据集中的气溶胶光学厚度数据,采用Man-Kendall趋势检验法和Sen''s slope变化趋势分析法,从不同的时空尺度和气溶胶类型上分析中国地区AOD值的时空变化特征.结果表明：①从年际尺度上看,1990~2017年AOD年均值整体呈波动上升趋势;从季节尺度上看,月均值整体呈春夏秋依次递减,冬季有所提升的趋势,地形和气候环境是其主要影响因素.②在空间上,AOD年均值呈现东南高西北低的特征,西南部四川盆地、西北的塔里木与吐鲁番盆地等为AOD值的高值区,青藏高原地区为AOD值的低值区,同时AOD的MK值和Sen''s slope值也呈现由东南向西北递减的趋势.③沙尘气溶胶和硫酸盐气溶胶影响分布具有明显的区域差异.与地形、气候变化以及人类活动强度有着密切联系.