The role of humic acid in the toxicity of arsenite to the diatom Navicula sp.

Dissolved organic matter (DOM) affects arsenite [As(III)] toxicity by altering its sorption equilibrium at the cell wall interface. A better understanding of such mechanism is of great importance to assess As(III) ecotoxicity in aquatic systems. Batch experiments were conducted to study the effects of DOM on the regulation of As(III) sorption and toxicity in the diatom Navicula sp. The influence of humic acid (HA) on As(III) toxicity was assessed by measuring algal growth, chlorophyll a, and reactive oxygen species (ROS), whereas As(III) mobility across the cell wall was estimated by determining the concentration of intracellular, cell-wall-bound, and free As(III) ions in cell media. Results showed that the effects of HA on arsenite toxicity varied depending on various combinations of As(III)-HA concentrations. EC₅₀ had an approximate threefold increase from 8.32 (HA-free control) to 22.39 μM (at 20 mg L^?1 HA) when Navicula sp. was exposed to 1.0–100.0 μM of As(III), compared to an overall low complexation ratio of HA-As(III) in a range of 0.91–6.00 %. The cell wall-bound and intracellular arsenic content decreased by 19.8 and 20.3 %, respectively, despite the lower arsenite complexation (2.10?±?0.16 % of the total As). Meanwhile, intracellular ROS was decreased by 12.6 % in response to 10.0 μM As(III) and 10 mg L^?1 HA vs. the HA-free control. The significant contrast indicated that complexation alone could not explain the HA-induced reduction in arsenite toxicity and other factors including HA–cell surface interactions may come into play. Isotherms describing adsorption of HA to the Navicula sp. cells combined with morphological data by scanning electron microscopy revealed a protective HA floccule coating on the cell walls. Additional Fourier transform infrared spectroscopic data suggested the involvement of carboxylic groups during the adsorption of both HA and As(III) on the Navicula sp. cell surface. Collective data from this study suggest that cell wall-bound HA can moderate As(III) toxicity through the formation of a protective floccule coating occupying As(III) sorption sites and decreased effective functional groups capable of binding As(III). Our findings imply that As(III) toxicity can be alleviated due to the increased hindrance to cellular internalization of As(III) in the presence of naturally abundant DOM in water.     

多元微电解填料对煤制油废水预处理的影响

采用高温烧结型微电解填料预处理煤制油废水,通过正交实验研究了初始pH、微电解时间及曝气强度等对废水的预处理影响。结果表明,微电解影响因素从大到小依次为:微电解时间pH曝气强度;微电解预处理煤制油废水的最佳工艺参数为:初始pH 4.0,微电解90 min,气水比3∶1充氧曝气;通过平行实验,COD平均去除率及出水水质分别为54.7%和1 773 mg/L,废水生物毒性指标EC50由原水12.5%的高毒性转化成48.3%的中毒性,为后续生化系统的正常运行提供了有利条件,是预处理煤制油废水的有效方法之一。     

Phosphorus interception in floodwater of paddy field during the rice-growing season in TaiHu Lake Basin

A field experiment located in TaiHu Lake Basin in China was conducted, by application of superphosphate or a mixture of superphosphate with manure, to elucidate the interception of P export during a typical rice growing season through 'zero-drainage water management' combined with sound irrigation, rainfall forecasting and field drying. P concentrations in floodwater rapidly declined before the first event of field drying, and subsequently tended to return to the background levels. Before the first field drying TPP was the predominant P form in floodwater on fields with no P input, DRP on plots that received superphosphate only, and DOP on plots treated with the mixture of superphosphate and manure. Thereafter TPP became the major form. No P export was found from the paddy fields, but a retention of 0.65kgha(-1), mainly due to soil P sorption. The results recommend the zero-drainage water management for full-scale areas for minimizing P export.     

Tissue-dependent distribution and accumulation of chlorobenzenes by vegetables in urban area

Five seasonal vegetables from three growing sites in Hangzhou city, Zhejiang Province, were studied for the levels of four chlorobenzenes(CBs): o-dichlorobenzene (o-DCB), p-dichlorobenzene (p-DCB), m-dichlorobenzene (m-DCB), and 1,2,4-trichlorobenzene (1,2,4-TCB). Samples of each vegetable from each site were subdivided into leaves, stems, and roots, and these subsamples were analyzed separately for the levels of accumulated CBs. Relations between the levels of CBs in vegetables with the total organic carbon (TOC) of the soil, the lipid content of the vegetable, and the physicochemical properties of CBs were established. Results showed that o-DCB, p-DCB, m-DCB, 1,2,4-TCB were present in all vegetables analyzed. For spinaches (Spinacia oleracea), Chinese cabbages (Brassica rapa var. pekinensis), and celery (Apium graveolens var. dulce), the highest level of CBs was with roots, followed by leaves. While for radishes (Raphanus sativus), and carrots (Daucus carota subsp. sativus), the highest level was with leaves, followed by stems. The accumulation of CBs was found to have a good correlation with the plant-tissue lipid content, the contaminant air-water Henry's coefficient (H), the contaminant octanol-water partition coefficient (K(ow)), and the physiological characteristics of the vegetables.     

我国人群有机磷阻燃剂暴露评估及其健康风险

有机磷阻燃剂的使用量呈现不断增加的趋势,但目前对我国人群有机磷阻燃剂的暴露特征及其健康风险研究甚少.为评估有机磷阻燃剂的暴露水平,本研究采集了全国8个城市中共600名普通成年人的尿液样本,用LC-MS-MS检测了11种有机磷酸酯代谢产物的浓度.研究表明,11种代谢产物均在尿液当中检出,磷酸二(2-氯乙基)酯(BCEP)...     

基于QUAL2K模型的钱塘江流域安全纳污能力研究

针对钱塘江流域污染物总量控制的纳污能力定量问题,选择非感潮河段干流和一级支流,基于QUAL2K模型和一维水质模型,研究了BOD安全纳污能力.研究结果表明,钱塘江流域纳污能力QUAL2K模型计算值大于一维模型计算值;基于QUAL2K模型的m值水体纳污能力计算法,结合了总量控制与浓度控制理念,适用于钱塘江流域水体纳污能力计算;流域各行政区BOD安全纳污能力从大到小依次为:杭州＞金华＞衢州＞绍兴＞丽水.     

EGSB反应器处理链霉素有机废水工业性试验研究

本文介绍了在厌氧中温发酵 (35± l℃ )条件下 ,采用膨胀颗粒污泥床 (EGSB)反应器日处理 2 0 0 t链霉素有机废水的工业性试验研究。试验结果表明 :在控制低浓度进料 ,COD在 2 0 0 0～ 70 0 0 mg/L、COD/SO2 - 4=7～ 1 0的条件下 ,有效地降低了毒性物质的抑制作用 ,使反应器成功启动并培养出颗粒污泥 ;当进料 COD在 70 0 0～ 1 30 0 0 mg/L,HRT为 3～ 5h,p H值为 6.8～ 7.2时 ,COD去除率可达75% ,反应器容积负荷最高可达 1 5.8kg COD/(m3.d) ,而 SO2 - 4去除率可有效地控制在 60 %～ 70 % ,实现了 EGSB反应器对链霉素废水中有机物和硫酸盐的有效去除。     

厌氧水解－好氧两段SBR处理焦化废水的研究

焦化废水含有毒物质多,生物降解性能差,对环境危害大。实验采用厌氧水解（酸化）－好氧（高效复合菌＋活性污泥）工艺处理焦化废水,进水COD、BOD5浓度分别为：698．13mg／l、232．0mg／l,经12h厌氧水解、18h好氧曝气后出水COD、BOD,浓度分别为136．93mg／1、39．3mg／l,NH3一N的去除率为68．37％。出水COD、BOD,满足《污水综合排放标准》（GB8978－96）中的排放要求。     

银川市冬季两次典型持续大气污染过程对比分析

为了探究边界层气象要素时空分布及其变化对银川市冬季持续污染天气过程污染物质量浓度变化的影响机制,利用2016年12月1日-2017年1月31日逐时空气质量以及地面和逐日定时探空气象观测数据,根据大气污染级别和过程持续时间,选取2016年12月9-21日（简称"1211过程"）和2016年12月29日-2017年1月9日（简称"1231过程"）为研究对象,采用统计和天气诊断相结合的方法,在分析比较银川市冬季两次典型持续污染过程演变特征及其与地面气象要素关系的基础上,探讨了大气环流、边界层要素变化对银川市冬季典型污染过程的可能影响机制.结果表明:①银川市冬季两次大气污染过程持续阶段,地面均以偏东或偏南风为主,风速较小,相对湿度较大,能见度较低;在污染清除阶段,地面风向转为西北或偏北风,风速较大,相对湿度较小,能见度较高.②当冬季欧亚大陆中纬度区域500 hPa高空盛行纬向气流,850 hPa高度上银川市受反气旋环流和暖温度脊控制,并且有弱暖平流从西南部向北输送时,银川市易出现静稳型持续污染天气.③冬季银川市持续大气污染过程中,ρ（PM_2.5）与风速呈负相关（R平均值为-0.326）,与相对湿度呈正相关（R平均值为0.688）,与能见度呈显著负相关（R平均值为-0.905）,与边界层高度呈较显著负相关（R平均值为-0.575）.④银川市冬季静稳型持续污染天气主要分为弱西北和平直西风气流型两种,弱西北气流型具有近地面层逆温弱,污染物积累慢,清除快的特征;平直西风气流型具有近地面层逆温强,污染物积累快,清除慢的特征.研究显示,冬季银川市上空500 hPa高度盛行纬向气流,地面主导风向为偏东或偏南风时,随着地面相对湿度增大、近地层风速减小、大气垂直上升运动减弱、边界层高度降低,大气中ρ（PM_2.5）将迅速升高,银川市易出现以PM_2.5为首要污染物的静稳型持续污染天气.      

广州市主要饮用水源中重金属健康风险的初步评价

对广州市主要饮用水源地水中重金属浓度进行了调查研究,并应用US EPA推荐的健康风险评价模型对饮用水源地水中重金属的健康风险作了初步评价.结果表明,西江断面、北江断面、东江断面重金属的平均浓度范围分别为Cd 0.21～3.96μg·L-1,As 1.16～13.75μg·L-1,Cr0.96～13.16μg·L-1,P...