Geochemical distribution,bioavailability and potential toxicity of some trace metals in a complex micro-tidal estuary,Southwest India

The spatial and temporal variations of some trace metals in the surface sediments of Cochin Estuary were analyzed along with their geochemical associations to identify the possible sources, bioavailability and the health risks posed by them. The dominance of kaolinite and suggested that clay minerals distribution is influenced by sediment sorting. Total metal analysis revealed enrichment for Cd, Pb and Zn due to anthropogenic activities. The speciation analysis established that notwithstanding the large availability, carbonate as well as organic and sulfides bound fractions showed negligible associations with most of the metals. Hydrous Fe–Mn oxides appeared to play a major role in controlling the fate and transport of these metals in the sediments of Cochin Estuary. Lower contribution of the residual fractions for Cd (21%–26%), Pb (<60%) and Zn (24%–42%) indicated an obvious increase of other geochemical fractions. Risk assessment analysis revealed that regardless of total concentration, none of the analyzed metals were at safe levels in the estuary as appreciable percentages were found to be associated with mobile geochemical forms. The speciation study conspicuously established that the metals originating from non-geogenic sources are largely associated with the labile fractions and hence are more detrimental to the aquatic biota.     

桑沟湾表层沉积物性质及对磷的吸附特征

通过研究桑沟湾表层沉积物对磷的吸附动力学曲线和吸附等温线,并结合沉积物的表面电荷性质及磷的形态分析,考察了沉积物对磷的吸附性能和吸附机制.结果表明,桑沟湾表层沉积物对磷的吸附过程包括快吸附过程和慢吸附过程,可用快慢二段一级动力学方程描述,等温线符合Langmuir交叉式模型.夏季沉积物样品的最大吸附量高于春季样品,粒级较小的沉积物吸附能力较强.沉积物样品对磷的最大吸附量Qm在0.047 1~0.123 0 mg·g-1之间,吸附/解吸平衡磷浓度(EPC0)范围在0.059 6~0.192 7 mg·L-1,沉积物充当"磷源"的作用.不同站位表层沉积物中无机磷(IP)是磷在沉积物中的主要赋存形态,吸附后的沉积物样品中弱吸附态磷(Ex-P)、铁结合态磷(Fe-P)明显增加.吸附过程包括物理吸附和化学吸附,以物理吸附为主.     

Metal distribution characteristic of MSWI bottom ash in view of metal recovery

Bottom ash is the major by-product of municipal solid waste incineration(MSWI), and is often reused as an engineering material, such as road-base aggregate. However, some metals(especially aluminum) in bottom ash can react with water and generate gas that could cause expansion and failure of products containing the ash; these metals must be removed before the ash is utilized. The size distribution and the chemical speciation of metals in the bottom ash from two Chinese MSWI plants were examined in this study, and the recovery potential of metals from the ash was evaluated. The metal concentrations in these bottom ashes were lower than that generated in other developed countries. Specifically, the contents of Al,Fe, Cu and Zn were 18.9–29.2, 25.5–32.3, 0.7–1.0 and 1.6–2.5 g/kg, respectively. Moreover,44.9–57.0 wt.% of Al and 55.6–75.4 wt.% of Fe were distributed in bottom ash particles smaller than 5 mm. Similarly, 46.6–79.7 wt.% of Cu and 42.9–74.2 wt.% of Zn were concentrated in particles smaller than 3 mm. The Fe in the bottom ash mainly existed as hematite, and its chemical speciation was considered to limit the recovery efficiency of magnetic separation.     

Study of cyanide removal from contaminated water using zinc peroxide nanomaterial

The present study highlights the potential application of zinc peroxide(ZnO_2)nanomaterial as an efficient material for the decontamination of cyanide from contaminated water. A process patent for ZnO_2 synthesis has been granted in United States of America(US Patent number 8,715,612; May 2014),South Africa,Bangladesh,and India. The ZnO_2 nanomaterial was capped with polyvinylpyrrolidone(PVP)to control the particle size. The PVP capped ZnO_2nanomaterial(PVP-ZnO_2)before and after adsorption of cyanide was characterized by scanning electron microscope,transmission electron microscope,X-ray diffractometer,Fourier transform infrared spectroscopy and time of flight-secondary ion mass spectrometry. The remaining concentration of cyanide after adsorption by PVP-ZnO_2 was determined using ion chromatograph. The adsorption of cyanide over PVP-ZnO_2 was also studied as a function of p H,adsorbent dose,time and concentration of cyanide. The maximum removal of cyanide was observed in p H range 5.8–7.8 within 15 min. The adsorption data was fitted to Langmuir and Fruendlich isotherm and it has been observed that data follows both the isotherms and also follows second order kinetics.     

Arsenic biotransformation and an arsenite S-adenosylmethionine methyltransferase in plankton

<正>Arsenic(As)is a well-recognized toxicant and carcinogen.Chronic exposure to inorganic arsenic causes a range of human cancers(e.g.,skin,bladder,and lung)and increases the risk of developing diabetes,hypertension,and cardiovascular and neurological diseases.The prevalence of arsenic species and the severity of their health effects continue to drive and demand for extensive research(Carlin et al.,2016).     

粉煤灰综合利用过程中汞的二次释放规律研究

我国粉煤灰年产生量4亿t左右,近年来利用率稳定在65%～68%,主要利用方式包括建材生产、道路施工、建筑工程和农业利用.建材生产包括高温工序,可能存在粉煤灰中汞的二次释放.本研究设计实验模拟了水泥生产、蒸养砖生产的主要环境因素,利用程序升温脱附的方法研究粉煤灰利用过程中的汞迁移转化规律,并对全国范围内粉煤灰利用过程汞的二次释放量做出估算.研究发现,粉煤灰中的汞以HgCl2(Hg2Cl2)、HgS和HgO的形式存在;水泥生产过程中,粉煤灰中98%以上的汞会释放;蒸养砖生产过程中,粉煤灰中汞的平均释放率为28%,释放率主要受到粉煤灰中的HgCl2(Hg2Cl2)比例的影响.我国粉煤灰利用过程中的汞二次排放量由2002年的4.07 t.a-1增至2008年的9.18 t.a-1,其中水泥行业的贡献率占到96.6%.     

原子吸收火焰法次灵敏线测定污水和电镀污泥中高含量的锌

对采用原子吸收火焰法次灵敏线测定污水和电镀污泥中高含量的锌进行了研究。试验结果表明：在锌浓度50．0～600．0mg/L之间,溶液锌含量与吸光度呈线性关系。线性回归方程为y＝0．000661x-0．0007,相关系数γ＝0．9998。方法检出限为25．0mg/L,相对标准误差（RSD）＜2．96％,加标回收率为92．5％～105％,与标准法的相对误差＜2．76％。     

湖泊沉积物质量基准研究进展

当前湖泊沉积物污染问题日益引起广泛关注,建立切实可行的沉积物环境质量基准,是对受污染沉积物进行科学评价和有效治理的重要前提。本论文介绍了沉积物质量基准的概念和国内外在该领域的最新研究进展,阐述了建立沉积物质量基准的主要方法,并对当前沉积物质量基准存在的关键问题和未来研究前景进行了分析。作者认为,当前亟待开展复合污染条件下的沉积物环境质量基准研究,应注重数值型沉积物质量基准和生物响应型沉积物质量基准的有机结合,加快建立沉积物毒性试验的标准方法体系,加强沉积物污染物的赋存形态与迁移转化规律研究,探索建立符合我国区域特点的沉积物质量基准理论、技术和方法体系,提高沉积物质量基准的准确性、针对性和适用性。     

Transport and fate of mercury under different hydrologic regimes in polluted stream in mining area

Seepage from Hg mine wastes and calcines contains high concentrations of mercury (Hg). Hg pollution is a major environmental problem in areas with abandoned mercury mines and retorting units. This study evaluates factors, especially the hydrological and sedimentary variables, governing temporal and spatial variation in levels and state of mercury in streams impacted by Hg contaminated runo . Samples were taken during di erent flow regimes in theWanshan Hg mining area in Guizhou Province, China. In its headwaters the sampled streams/rivers pass by several mine wastes and calcines with high concentration of Hg. Seepage causes serious Hg contamination to the downstream area. Concentrations of Hg in water samples showed significant seasonal variations. Periods of higher flow showed high concentrations of total Hg (THg) in water due to more particles being re-suspended and transported. The concentrations of major anions (e.g., Cl??, F??, NO3?? and SO4 2??) were lower during higher flow due to dilution. Due to both sedimentation of particles and dilution from tributaries the concentration of THg decreased from 2100 ng/L to background levels (< 50 ng/L) within 10 km distance downstream. Sedimentation is the main reason for the fast decrease of the concentration, it accounts for 69% and 60% for higher flow and lower flow regimes respectively in the upper part of the stream. Speciation calculation of the dissolved Hg fraction (DHg) (using Visual MINTEQ) showed that Hg(OH)2 associated with dissolved organic matter is the main form of Hg in dissolved phase in surface waters in Wanshan (over 95%).     

水中汞形态分析研究进展

水环境中的汞毒性很大,不同形态的汞毒性不同,测定汞总量不能揭示汞的毒性,需要进行汞形态分析的研究。文章介绍了近年来水环境中汞形态分析的前处理技术及检测进展。