The importance of different forms of Pb on diminishing biological activities in a calcareous soil

In this experimental study, we evaluated the effect of different lead (Pb) fractions on biological properties in soil spiked with 0, 600, 1200 and 1800 mg kg^?1 Pb, during a 90-day incubation period at 25?28°C. Different Pb fractions were measured by sequential extraction at days 1 and 90 after soil treatment. Diethylenetriaminepentaacetic acid (DTPA)-extractable Pb and soil biological properties at days 1, 5, 15, 45 and 90 were measured. The concentration of Pb in soluble and exchangeable fractions was very high at day 1, but it showed remarkable transfer into carbonate and residual fractions by day 90. Substrate-induced respiration, basal respiration, acid and alkaline phosphatases, microbial populations (bacterial, fungal and actinomycetes) and biomass carbon decreased significantly with soil contamination compared with the control. With Pb ageing, these biological properties increased. Metabolic quotient (qCO₂) increased significantly compared with the control with increasing Pb concentration. The toxicity of various forms of Pb for the biological status of the soil was in the following order: KNO₃ extractable>NaOH extractable>EDTA extractable>HNO ₃ extractable>total content Pb. Thus, the bioavailable fractions are better indicators of Pb pollution in soils.     

重金属Zn、Pb和Cd对可口革囊星虫的急性毒性作用

研究了必需元素Zn及非必需元素Pb、Cd对可口革囊星虫(Phascolosoma esculenda)的急性毒性作用,得到Zn2 的48 h LC50和96 h LC50分别为61.09、10.91 mg/L;pb2 的48 h LC50和96 h LC50分别为29.44、10.59 mg/L;Cd2 的48 h LC50和96hLC50分别为10.69、4.46mg/L.估算得到Zn、Pb和Cd对可口革囊星虫的安全浓度分别为0.55、0.53和0.22mg/L.     

Effect of temperature on single and competitive adsorptions of Cu(II) and Zn(II) onto natural clays

This study conducted a combined adsorption-sequential extractionanalysis (CASA), by which five phases (i.e., exchangeable, carbonate, Mn-Oxide, organic, and Fe-Oxide phases) of adsorbed heavy metals were analyzed, to investigate temperature effects on single and competitive adsorptions of Zn(II) and Cu(II) ontonatural clays. In the case of single adsorption of Zn, the exchangeable phase adsorption decreased from 65 to 40%, but thecarbonate phase adsorption increased from 30 to 40%, with an increase in temperature from 15 to 55 °C. However, in itscompetitive adsorption with Cu, Zn was mostly present in the exchangeable phase (over 90%), and with an increase in temperature, the exchangeable phase adsorption decreased only 10%. In the case of Cu, over 50% among the total amount of adsorption was present in the carbonate phase in both cases ofsingle and competitive adsorptions. The carbonate phaseadsorption of Cu increased from 56 to 61% and from 60 to 66% in single and competitive adsorptions, respectively, with atemperature increase. These results show that in the case of Zn,the major mechanism of retention in natural clay soils might beexchangeable phase adsorption, especially in the case of competitive adsorption with Cu. However, in the case of Cu, the major mechanism might be carbonate phase adsorption, which is known to be a more immobile phase than exchangeable phase adsorption. It seems that the adsorption of Zn and Cu onto natural clays is an endothermic reaction, which represents thatthe adsorption equilibrium constants and capacities increase with a temperature increase, with the exception of exchangeablephase adsorption.     

空气颗粒物中铅、镉超声浸取-原子吸收测定方法研究

用超声波震荡方法对大气滤膜样品进行前处理,提取待测元素。研究了浸取液种类、酸度、浸取时间和干扰因素等,确定了颗粒物样品溶液制备的最佳条件,与流动注射在线富集——原子吸收技术结合,建立了大气颗粒物样品测定Pb、Cd方法。结果表明,方法快速、准确,标准样品测定回收率在97％以上,6次测定方目对标准偏差小于2.6％。     

微波消解-原子吸收光度法测定土壤中铜锌铅镉镍铬

用微波消解－原子吸收光度法测定土壤中铜，锌，铅，镉，镍和铬。通过硝酸－氢氟酸－过氧化氢体系消解液对土壤样品消解，选择出微波最佳消解条件。对硝酸－盐酸－过氧化氢体系消解液和硝酸－氢氟酸－过氧化氢体系消解液进行消解对比试验，发现前者不能将土壤样品完全消解，后者能将样品消解完全，但需将消解液中剩余的酸赶尽，否则测定结果将明显偏低。微波消解土壤与传统电热消解相比，操作简便快速，可提高工作效率。     

基于贝叶斯理论的小麦籽粒镉铅超标风险预测

对农作物污染风险进行预测具有重大意义.基于贝叶斯定理及数据分布特征,建立了贝叶斯风险预测模型,并使用区域大田调查土壤-小麦重金属含量数据,预测小麦籽粒Cd和Pb超标风险并验证该模型的准确度.结果表明,该模型预测小麦籽粒Cd超标风险时相对偏差较小,以小麦籽粒Cd含量为变量的预测相对偏差仅为(2.66±1.87)%,以土壤DTPA-Cd含量和土壤Cd全量为变量时预测相对偏差则分别为(5.11±3.77)%和(5.88±3.87)%, 3个变量均能使预测结果与真实超标概率的平均相对偏差小于10%.预测小麦籽粒Pb超标风险时,仅小麦籽粒Pb含量的预测相对偏差小于10%.数据来源、数据分布特征和变量的选择是影响贝叶斯风险预测模型预测相对偏差的重要因素.该模型基于大田数据的先验分布,能够有效反映大田生产条件下小麦籽粒重金属与土壤因子间的相互关系,预测较准确,具有应用潜力.     

Elemental sulfur effects on Pb and Zn uptake by Indian mustard and winter wheat

A pot experiment was conducted to investigate the influence of elemental sulfur to contaminated soil on plant uptake by a heavy metal hyperaccumulator, Indian mustard( Brassica juncea ) and a field crop, winter wheat( Triticum. aestivum). Elemental sulfur(S) with different rates was carried out, they were 0(S0 ), 20(S20 ), 40(S40 ), 80(S80 ), and 160(S160 ) mmol/kg respectively. Extra pots with the same rates of S but without plants were used for soil sampling to monitor pH and CaCl2-extractable heavy metal changes. The results showed that S enhanced phytoextraction of Pb and Zn from contaminated soil. Application S effectively decreased soil pH down to 1.1 as the most at the rate of Sl60. The concentrations of CaCl2-extractable Pb and Zn in soil and uptake of Pb and Zn by the plants were increased with soil pH decreased. A good correlation between CaCl2-extractable Pb/Zn and soil pH was found( Rpb^2 = 0.847 and RZn^2 = 0,991, n = 25). With S application, soil CaCl2-extractable Pb and Zn concentrations, concentration of Pb and Zn in plants and the amount of removal by plant uptake were significanfly higher than those without S. Under the treatment of S160, the highest CaCl2-extmctable Pb and Zn were observed, they were 4.23 mg/kg and 0.40 mg/kg, 2.7 and 2.0 times as that of the control(So ) respectively. At the highest rates of S( Sl~0 ), both Indian mustard and winter wheat reached the highest uptake of Pb and Zn. The highest Pb concentrations in wheat and Indian mustard were 32.8 mg/kg and 537.0 mg/kg, all 1.8 times as that of the control, and the highest Zn concentrations in wheat and Indian mustard were 215.5 mg/kg and 404.0 mg/kg, 2.4 and 2.0 times as that of the control respectively. The highest removals of Pb and Zn from the contaminated soil were 0.41 rag/pot and 0.31 nag/pot by Indian mustard in the treatment of S160 through 50 days growth.     

Regeneration of commercial selective catalyst reduction catalysts deactivated by Pb and other inorganic elements

The regeneration of commercial SCR(Selective Catalyst Reduction) catalysts deactivated by Pb and other elements was studied.The deactivated catalyst samples were prepared by chemical impregnation with mixed solution containing K_2SO_4,Na_2SO_4,CaSO_4,Pb(NO_3)_2and NH_4H_2PO_4.A novel method combining Ethylenediaminetetraacetic acid disodium salt(EDTA-2Na) and H_2SO_4solution(viz.catalysts treated by dilute EDTA-2Na and H_2SO_4 solution in sequence) was used to recover the activity of deactivated samples,and the effect was compared with single H_2SO_4,oxalic acid,acetic acid,EDTA or HNO_3 solutions.The surface structure,acidity and reducibility of samples were characterized by N_2adsorption–desorption,inductively coupled plasma optical emission spectrometer(ICP-OES),scanning electron microscopy(SEM),X-ray diffraction(XRD),X-ray fluorescence(XRF),H-2-temperature programmed section(H_2-TPR),NH3-temperature programmed desorption(NH3-TPD) and in situ DRIFTS.Impurities caused a decrease of specific surface area and surface reducibility,as well as Br?nsted acid sites,and therefore led to severe deactivation of the SCR catalyst.The use of an acid solution alone possibly eliminated the impurities on the deactivated catalyst to some extent,and also increased the specific surface area and Br?nsted acid sites and promoted the surface reducibility,thus recovered the activity partially.The combination of EDTA-2Na and H_2SO_4 could remove most of the impurities and improve the activity significantly.The removal of Pb should be an important factor for regeneration.Due to a high removal rate for Pb and other impurities,the combination of EDTA-2Na and H_2SO_4 solutions provided the best efficiency.     

黑曲霉（Aspergillus niger）对Pb2+的吸附特性研究

以黑曲霉菌丝体作为吸附剂,通过静态吸附实验研究了各种因素对其吸附去除废水中Pb2+的影响。结果表明：当Pb2+初始浓度为50 mg/L,吸附剂用量为1．0 g/L,吸附时间为45 min,pH为5．0时,吸附效果最佳。此时吸附量为44．1 mg/g,去除率为90．86%。使用准二阶动力学方程可较好的拟合黑曲霉对Pb2+的吸附,表明该吸附过程以化学吸附为主。等温吸附过程可用Freundlich方程描述,说明该吸附为多分子层吸附。傅立叶红外光谱分析表明,黑曲霉吸附剂表面的酯羰基(-COO-)、羧基(-COOH )和羟基(-OH )在吸附Pb2+的过程中发挥主要作用。     

Interactions between lead(II) ions and dissolved organic matter derived from organic fertilizers incubated in the field

This work was to study composition characteristics and the subsequent effect on the lead (Pb) binding properties of dissolved organic matter (DOM) derived from seaweed-based (SWOF) and chicken manure organic fertilizers (CMOF) during a one-year field incubation experiment using the excitation-emission matrix-parallel factor (EEM-PARAFAC) and two-dimensional correlation spectroscopy (2DCOS) analysis. Results showed that high aromatic and hydrophobic fluorescent substances were enriched in CMOF-derived DOM and SWOF-derived DOM and enhanced over time. And phenolic groups in the fulvic-like substances for SWOF-derived DOM and carboxyl groups in the humic-like substances for CMOF-derived DOM had the fastest responses over time, respectively. Moreover, both non-fluorescent polysaccharides and fluorescent humic-like substances or fulvic-like substances with aromatic (C=C) groups first participated in the binding process of Pb to SWOF-derived DOM on day 0 and 180 during the lead binding process. In contrast, humic-like substances associated with aromatic (C=C) and phenolic groups gave a faster response to Pb binding on day 360. Regarding CMOF-derived DOM, the fulvic-like substances associated with aromatic (C=C) and carboxylic groups displayed a faster response to Pb ions on day 0. Nonetheless, polysaccharides and humic-like associated with phenolic groups had a faster response on days 180 and 360. It is noteworthy that the polysaccharides, which participated in Pb binding to CMOF-derived DOM, posed a higher risk of Pb in the environment after 360 days. Therefore, these findings gave new insights into the long-term applications of commercial organic fertilizers for the amendment of soil.