Electrochemical determination of the effect of lead(II) on the photochemical degradation of the pesticide metamitron

The complexation of the pesticide Metamitron by lead(II) was investigated by polarography and stripping voltammetry. The influence of the pH on the complexation was determined and a maximum value for the conditional stability constant of the lead‐metamitron complex (logβ’ = 3.1) was obtained at pH 5.6.

An investigation into the photochemical degradation of the pesticide demonstrated that lead decreases the degradation rate of metamitron by 13% within the first 30 days, due to stabilisation by complexation.     

铅与纳米SiO2联合染毒对A549细胞氧化损伤的影响

为了研究铅与纳米SiO2联合染毒所致的细胞损伤特征,并从氧化应激方面探讨其可能的作用机制。用铅和SiO2处理A549细胞,采用四唑盐(MTT)比色法检测细胞存活率,评价铅和SiO2联合染毒所致的细胞损伤特征;采用硫代巴比妥酸(TBA)比色法检测细胞内丙二醛(MDA)含量,评价铅与SiO2联合染毒所致细胞的氧化应激状态;检测了细胞内抗氧化物还原型谷胱甘肽(GSH)含量以及细胞内抗氧化酶的活性,以评价铅与SiO2联合染毒对细胞抗氧化系统的影响。将实验数据进行ANOVA分析。结果表明,铅、SiO2单独染毒组各指标没有明显改变;而联合染毒能造成细胞氧化损伤,表现为细胞存活率、GSH水平、超氧化物歧化酶(SOD)及谷胱甘肽过氧化物酶(GSH-Px)活性显著低于对照组及2个单独染毒组(P<0.05),细胞内MDA含量显著高于对照组及各单独染毒组(P<0.05)。可见,联合染毒可引起明显的细胞毒性,氧化损伤可能是铅与SiO联合染毒致肺细胞毒性损伤的作用机制之一。     

Size-resolved aerosol ionic composition and secondary formation at Mount Heng in South Central China

To understand the size-resolved aerosol ionic composition and the factors influencing secondary aerosol formation in the upper boundary layer in South Central China, size-segregated aerosol samples were collected using a micro-orifice uniform deposit irnpactor （MOUDI） in spring 2009 at the summit of Mount Heng （1269 m asl）, followed by subsequent laboratory analyses of 13 inorganic and organic water-soluble ions. During non- dust-storm periods, the average PM1.8 concentration was 41.8 μg·m^-3, contributing to 55% of the PM10. Sulfates, nitrates, and ammonium, the dominant ions in the fine particles, amounted to 46.8% of the PM1.8. Compared with Mount Tai in the North China Plain, the concentrations of both fine and coarse particles and the ions contained therein were substantially lower. When the air masses from Southeast Asia prevailed, intensive biomass burning there led to elevated concentrations of sulfates, nitrates, ammonium, potassium, and chloride in the fine particles at Mount Heng. The air masses originating from the north Gobi brought heavy dust storms that resulted in the remarkable production of sulfates, ammonium, methane sulfonic acid, and oxalates in the coarse particles. Generally, the sulfates were primarily produced in the form of （NH4）2SO4 in the droplet mode via heterogeneous aqueous reactions. Only approximately one-third of the nitrates were distributed in the fine mode, and high humidity facilitated the secondary formation of fine nitrates. The heterogeneous formation of coarse nitrates and ammonium on dry alkaline dust surfaces was found to be less efficient than that on the coarse particles during non-dust-storm periods.     

Variation pattern of water-soluble ions in atmospheric at Lin＇an regional background station

为研究我国长江三角洲地区气溶胶污染的区域特征,2008年4月、7月、10月和2009年1月,在临安区域本底站利用安德森（Andersen）分级采样器进行了大气气溶胶采样,样品用离子色谱（IC）进行了分析.结果表明,临安区域本底站SO2/4-、NH4＋、K＋的浓度在粒径0.43—1.1μm出现峰值;Ca2＋、Mg2＋的浓度在粒径3.3—5.8μm出现峰值;NO3-、Cl-、Na＋的浓度在粒径0.43—1.1μm和3.3—5.8μm出现峰值.气溶胶各个粒径段上的阳、阴离子电荷比均小于2.在降水过程个例分析中,降水之后临安区域本底站的总离子浓度增加了10.9μg·m-3;粒径分布除SO2/4-和K＋有明显变化以外,其它离子没有明显变化.通过霾日和非霾日的浓度变化分析发现,细粒子中SO2/4-、NH4＋的浓度的增加是造成霾天气的主要原因.     

海水中金属铅水质基准定值研究

为建立符合我国海洋生物对金属铅耐受能力的海水水质基准,依据可代表我国生物区系特征的生态毒理学数据基于评价因子法及物种敏感度分布模型,对金属铅的海水水质基准进行了推导.推导结果显示,不同的推导方法定值存在明显差异.基于物种敏感度分布模型法,铅的海水水质基准高值(HSWC)定值为275 μg/L;基于评价因子法,铅的海水水质基准低值(LSWC)定值为0.8 μg/L.推导结果可为我国海水水质标准的修订提供有益参考.     

湿地挺水植物根际金属离子的分布及界面扩散通量

挺水植物作为湿地生态系统的重要组成部分,其根系的生长发育过程影响其环境功能的发挥及其根土和水土界面环境生物地球化学过程。界面的氧化还原异质环境是金属离子发生扩散、沉淀和溶解以及吸附和解析等许多瞬时过程的重要场所,这些过程对金属离子在固相和水相的分配起着重要的作用。获取金属离子赋存特征和定量评估大型挺水植物生长对其界面行为的影响,是了解金属离子在界面环境生物地球化学过程的关键环节。利用高分辨率沉积物原位间隙水采样技术（Pore Water Equilibrators,Peeper）获得芦苇、香蒲和茭草3种挺水植物根际与非根际溶液中Al3＋、Fe3＋、Mn2＋和Ca2＋的剖面分布特征,并利用Fick第一定律定量估算它们在沉积物-水界面的扩散通量。结果表明：湿地沉积物孔隙水中Al3＋、Fe3＋、Mn2＋和Ca2＋的含量较上覆水存在着明显的富集现象。其中Fe3＋、Mn2＋分布受大型挺水植物影响最为显著,且随沉积物深度增加,富集效应有进一步加剧趋势。从剖面垂向分布来看,Al3＋含量的峰值靠近沉积物的表层,而Fe3＋、Ca2＋和Mn2＋含量峰值出现位置相对较深存在于沉积物中下层。与无植被的对照区域相比,4种金属离子含量在植物根区附近显著升高（P〈0.05）,其中Al3＋、Fe3＋和Ca2＋受芦苇生长过程影响最为明显,其在根际孔隙水中峰值含量达18.3、513和5408μmol·L-1,较对照分别增加了6.0、2.5及25.8倍,芦苇根际效应显著高于香蒲和茭草。多重比较分析结果显示,Mn2＋在根区的分布受茭草影响最大,在根区孔隙水中浓度为21~97μmol·L-1较对照区的1.1~52.5μmol·L-1,平均浓度增加65%。受植物根区环境的影响,Fe3＋和Ca2＋在植物根区释放速率明显加快,其中茭草根区释放速率分别为（35.38±3.05）和（240.18±20.71）μmol·m-2·d-1较对照区增加10倍;另外湿地植物存在直接导     

Removal of Cu（ll） ions from aqueous solution by activated carbon impregnated with humic acid

Humic acid （HA） was impregnated onto powdered activated carbon to improve its Cu（II） adsorption capability. The optimum pH value for Cu（II） removal was 6. The maximum adsorption capacity of HAimpregnated activated carbon was up to 5.98mg.g-1, which is five times the capacity of virgin activated carbon. The adsorption processes were rapid and accompanied by changes in pH. In using a linear method, it was determined that the equilibrium experimental data were better represented by the Langmuir isotherm than by the Freundlich isotherm. Surface charges and surface functional groups were studied through zeta potential and FTIR measurements to explain the mechanism behind the humicacid modification that enhanced the Cu（II） adsorption capacity of activated carbon.     

Removal of lead from aqueous solution by hydroxyapatite/manganese dioxide composite

A novel composite adsorbent, hydroxyapatite/manganese dioxide (HAp/MnO₂), has been developed for the purpose of removing lead ions from aqueous solutions. The combination of HAp with MnO₂ is meant to increase its adsorption capacity. Various factors that may affect the adsorption efficiency, including solution pH, coexistent substances such as humic acid and competing cations (Ca²⁺, Mg²⁺), initial solute concentration, and the duration of the reaction, have been investigated. Using this composite adsorbent, solution pH and coexistent calcium or magnesium cations were found to have no significant influence on the removal of lead ions under the experimental conditions. The adsorption equilibrium was described well by the Langmuir isotherm model, and the calculated maximum adsorption capacity was 769 mg·g⁻¹. The sorption processes obeyed the pseudo-second-order kinetics model. The experimental results indicate that HAp/MnO₂ composite may be an effective adsorbent for the removal of lead ions from aqueous solutions.     

柠檬酸-施氏矿物复合体对Cd和Pb的吸附研究

施氏矿物(Schwertmannite)是酸性矿区废水污染环境中典型的铁硫酸盐次生矿物,由于其较好的吸附能力成为矿区多种重金属的沉积库.环境中同时广泛存在着各种有机质,易与矿物结合形成有机质矿物复合体,从而影响矿物对重金属的吸附行为.目前关于有机质与施氏矿物形成的复合体对重金属的吸附研究相对较少.因此,本研究选取柠檬酸作为天然有机质的代表,研究不同环境条件下柠檬酸施氏矿物复合体对重金属Cd、Pb的吸附.结果表明,复合体保持着施氏矿物基本的矿物学特征,对重金属Cd和Pb的吸附行为表现出不同的趋势:复合体对Cd的吸附量整体上随着Cd浓度和pH值的升高而上升;相反,复合体对Pb的吸附量均比纯施氏矿物要低,并且随着柠檬酸含量的升高吸附量下降越明显;体系中共存的硫酸根离子(SO₄^2-)抑制了复合体对Cd的吸附,而对Pb的吸附则起到促进作用.XRD分析表明柠檬酸抑制了高pH下Pb在矿物表面形成PbSO₄沉淀.FTIR红外谱图进一步证明结合在复合体上的柠檬酸参与了对Cd和Pb的吸附过程.本研究结果有助于更好地预测Cd和Pb在矿区的迁移和归宿.     

老化微塑料对水体中重金属铜和锌的吸附行为研究

微塑料（Microplastics,MPs）在水环境中可以作为重金属载体,对金属离子的迁移和毒性效应产生较大影响.本文开展了紫外光老化后的聚丙烯（Polypropylene,PP）和聚乙烯（Polyethylene,PE）对两种重金属离子Cu²⁺和Zn²⁺在单一和二元复合体系中的吸附行为研究.通过拟一级和拟二级动力学模型研究发现,微塑料对重金属离子的吸附过程更符合拟二级动力学过程,利用Langmuir模型和Freundlich模型对吸附等温线结果进行拟合,结果表明,在单一体系中,相同老化条件下的PP相比PE对金属离子的平衡吸附量更高,且对Cu²⁺的吸附量均大于对Zn²⁺;在二元复合体系中,由于竞争吸附作用,MPs对重金属离子的吸附量小于在单一体系中的吸附量,且MPs对重金属离子的吸附过程更符合Freundlich模型,即吸附主要以多层吸附为主.吸附热力学研究表明,老化PP和PE微塑料对Cu²⁺和Zn²⁺的吸附行为属于自发吸热过程.微塑料PP和PE吸附前后对莱茵衣藻的毒性试验结果表明,微塑料存在均对藻类的生长有抑制作用,但吸附重金属后的微塑料对藻的生长抑制率有所降低.通过藻的酶活性（包括超氧化歧化酶（SOD）,丙二醛（MDA）和过氧化氢酶（CAT））的测定结果表明,微塑料对藻造成一定的氧化损伤,而吸附重金属后的微塑料的毒性作用下降.本论文可以为环境中微塑料存在下复合污染物的竞争吸附行为和联合生态效应研究提供理论依据.