Distribution,fractionation,and contamination assessment of heavy metals in offshore surface sediments from western Xiamen Bay,China

Surface sediment samples were collected at 21 offshore sites in western Xiamen Bay, Southeast China.Total concentrations of Li, V, Cr, Co, Ni, Cu, Zn, Sr, Mn,Pb, Ba, Fe, and Ti were determined by inductively coupled plasma-optical emission spectrometry; Hg was determined by atomic fluorescence spectrometry. A modified BCR sequential extraction procedure was used to extract fractions of the above elements. Concentrations of Pb, Cr, and Hg at most sites met the primary standard criteria of Marine Sediment Quality except site S12 for Pb and S7 for Cr, while concentrations of Zn at 17 sites and Cu at seven sites exceeded the criteria. The mean concentration of Hg was three times higher than the background, with a possible source being the Jiulong River. Fe, Ti, Ba, Co, V, and Li dominated the residual phase, mainly from terrestrial input.Ni, Cr, Pb, and Hg in the non-residual phase varied largely between sites. Sr, Mn, Cu, and Zn were mainly in the nonresidual fraction. Most sites showed considerable ecological risk; exceptions were site S7(very high) and sites S10,S11, and S14(moderate). Cu showed moderate-to-high pollution and Pb exhibited no-to-low pollution, while other metals had a non-pollution status according to their ratios of secondary phase to primary phase(RSP). Results of two assessment methods showed moderate pollution and a veryhigh ecological risk for Cu, Zn, Ni, and Cr at site S7, which might be due to the local sewage treatment plant.

Bioavailability of heavy metals in soil of the Tieguanyin tea garden, southeastern China

The bioavailability of 22 heavy metals was investigated at 19 sampling sites in Tieguanyin tea garden in Anxi County,Fujian Province,southeastern China.Heavy metal concentrations were determined by inductively coupled plasma-mass spectrometry(ICP-MS)and evaluated by geo-accumulation index(I_(geo)).Dilute nitric acid extraction was used to evaluate biological activity.Cu,Pb,and Cd were highly bioavailable and most easily absorbed by tea trees.Heavy metal bioavailability in the surface soil was as the ratio of the effective state to the total amount.Cd had the highest I_(geo)values,and the respective samples and sites were classified as moderately/strongly contaminated.Cd element is considered the main factor of heavy metal pollution in the tea garden in Anxi.The other heavy metals studied were present in lower concentrations;thus,the samples were classified as uncontaminated or slightly contaminated.

修正的铅锶同位素混合模型定量解析大气PM_(2.5)的来源

本文在2014年3月至2015年1月采集了泉州市城区5个采样点的大气PM_(2.5)样品,并同步采集泉州市主要大气PM_(2.5)潜在污染源样品.采用电感耦合等离子质谱(ICP-MS)和热电离质谱(TIMS)分析样品中铅、锶含量及铅、锶同位素的组成,利用铅、锶二元同位素示踪了大气PM_(2.5)的污染来源.结果表明,泉州市大气PM_(2.5)主要来自建筑尘、交通源、燃煤尘、垃圾焚烧厂飞灰和土壤扬尘.通过对传统的同位素混合模型计算方法的修正,尝试解决"二元同位素混合模型"无法定量解析3个以上PM_(2.5)潜在污染源的问题.根据修正的同位素混合模型计算采样期间大气各个PM_(2.5)潜在污染源的平均贡献率,分别为建筑尘(23.3%～35.4%)、交通源(22.4%～52.9%)、燃煤尘(10.1%～24.1%)、垃圾焚烧飞灰(2.1%～4.8%)和土壤扬尘(2.1%～14.5%),表明该修正方法具有一定的应用价值.

Chemical characteristics and Pb isotopic compositions of PM2.5 in Nanchang, China

In mid-September 2013, PM2.5 samples were collected at six sites in Nanchang, Jiangxi Province, China, to quantify nine water-soluble ions （Ca2＋, Mg2＋, K＋, Na＋, NH4＋, SO42-, Cl-, F , NO3 ）, 29 trace elements （Ba, Zn, Pb, Ni, Mo, Cr, Cu, Sr, Sb, Rb, Cd, Bi, Zr, V, Ga, Li, Y, Nb, W, Cs, Tl, Sc, Co, U, Hf, In, Re, Be, and Ta）, and to characterize Pb isotopic ratios （^207pb/^206pb, ^208pb/^206pb, and ^207pb/^204pb） for identifying the main source（s） of Pb. The results showed that the average daily PM2.5 concentration （53.16 ± 24.17） Dg/m3 was within the secondary level of the Chinese ambient air quality standard. The combined concentrations of SO42-, NH4＋, and NO3- to total measured water-soluble ion concentrations in PM2.5 ranged from 79.40% to 95.18%, indicating that anthropogenic sources were significant. Coal combustion and vehicle emissions were both contributors to PM2.5 based on the NO3-/SO4^2- ratios. Wushu School experienced the lowest concentrations of PM2.s and most trace elements among the six sampling sites. Enrichment factor results showed that TI, Cr, In, Cu, Zn, Pb, Bi, Ni, Sb, and Cd in PM2.5 were affected by anthropogenic activities. Cluster analysis suggested that Cd, Sb, Pb, Re, Zn, Bi, Cs, Tl, Ga, and In were possibly related to coal combustion and vehicle exhaust, while Ni, Nb, Cr, and Mo may have originated from metal smelting. Pb isotopic tracing showed that coal dust, cement dust, road dust and construction dust were the major Pb sources in PM2.5 in Nanchang. Combined, these sources contributed an average of 72.51% of the Pb measured, while vehicle exhaust accounted for 27.49% of Pb based on results from a binary Pb isotope mixed model,

Effective alleviation of Cd stress to microbial communities in mining reclamation soils by thiourea-modified biochar amendment

Reclaimed soils in mining area usually display low fertility and present Cd stress.The amendment of modified biochar effectively fixes Cd in soils,enhances soil fertility,and reduces Cd stress in soil microorganisms.However,the effect of thiourea-modified biochar(TBC)on microbial adaptability to Cd stress in mining reclamation soils is still unclear.The present work studied the Cd immobilization and microbial community changes in a mining reclamation soil displaying extreme Cd contamination under TBC amendment.The results indicated that the amendment of TBC significantly enhanced(P<0.05)soil pH,the content of available phosphorus(AP),and the activities of urease and polyphenol oxidase by 1.3%,463.4%,54.4%,and 84.0%,respectively,compared to the control without amendment.The amount of toxicity characteristic leaching procedure-extracable Cd decreased(P<0.05)by 68.0%in the TBC-amended soil compared with the unamended soil.The structure of soil microbiota was reorganized and the alpha diversity index was increased in the TBC treatment.The TBC amendment increased the relative abundances of Proteobacteria,Bacteroidota,and Zoopagomycota,which were strongly associated(P<0.01)with higher soil pH and AP.Structural equation model results demonstrated that Cd immobilization was directly influenced by soil pH,AP,and urease,and indirectly affected by bacterial structure in the TBC treatment.The TBC amendment can effectively improve the structural composition of soil bacteria under Cd stress and enhance the pathways of decreasing soil Cd availability as well.The results might facilitate the development of in-situ remediation programs in Cd-contaminated soils in the future.