The transport of Cu and Zn from agricultural soils to surface water in a small catchment

Long-term manure-borne copper and zinc inputs (18-324 mg Cu m⁻² yr⁻¹ and 100-800 mg Zn m⁻² yr⁻¹) to grassland soils resulted in their catchment in water concentrations that often exceeded the surface water quality criteria (2 μg Cu l⁻¹ and 5 μg Zn l⁻¹). This paper compares retention and release of Cu and Zn by two types of soil, a mineral soil (MS) and a dark colored soil rich in organic matter (OS). On the basis of dry soil mass, the OS has a higher retention/affinity for Cu and Zn than the MS, but much less Zn accumulated in the MS when compared on an areal basis. This is largely because of the much smaller bulk OS density and larger dissolved metal concentrations in the OS drainage than that for the MS. However, because of the greater water retention capacity of the OS, elevated metal concentrations in the soil solution do not necessarily cause greater loss to water. It is concluded that artificially drained OS can contribute significantly to the observed elevated Cu and Zn concentrations of the river, especially during relatively dry weather conditions when the contribution of water seeping from OS to the total river water discharge becomes increasingly important.     

Soft and sour: The challenge of setting environmental quality standards for bioavailable metal concentration in Fennoscandinavian freshwaters

The European Union Water Framework Directive (WFD) requires member states to ensure that all inland and coastal waters achieve ‘good’ water quality status. To this end, the WFD has set environmental quality standards (EQS) or Water quality criteria (WQC) for priority pollutants that include the four metals Cd, Ni, Pb and Hg. Many states have also chosen to set EQS for Cu and Zn. The use of bioavailability models to set EQS, paves the way for accepting higher local metal concentrations in waters where metal bioavailability is deemed low. The Biotic Ligand Model (BLM) concept has been proposed as a tool for estimating metal bioavailability and for calculating local EQS in the EU guidance document. The BLM estimates metal bioavailability based on the dissolved metal concentration and key ancillary water chemistry parameters (acidity, hardness and organic carbon content). The BLMs developed so far, have only been validated for water chemistry input parameters typical of Central Europe. However, the pH, alkalinity and dissolved organic carbon levels of a significant fraction of Fennoscandinavian (Finland, Norway and Sweden) freshwaters are outside the calibration range of currently available BLMs. The levels of Ca²⁺, alkalinity and pH in 75%, 29% and 22%, respectively, of the ca. 2500 Fennoscandinavian freshwater bodies investigated in this survey were outside the calibration range of tested BLMs. Moreover, a comparison of the ability of the tested BLMs to predict the acute and chronic copper toxicity to Daphnia magna and Rainbow trout indicated that the BLMs should be used with caution outside their current validation range. We conclude that more work is needed to extend the application of BLMs in the practical risk assessment to encompass a broader range of European freshwater bodies.     

膜电解法处理含镍废水的研究

镍作为合金化元素得到广泛应用,不锈钢占全球镍消费量的大约一半,因价格昂贵,故镍的回收有很大的意义.采用单阴膜电解法对含镍废水中的镍离子进行电沉积回收,研究膜种类、电流密度、温度、电解时间、搅拌速度等因素对镍离子去除效果.实验结果表明:在电流密度为60 A/m2,温度为40℃,pH为3.5,电解时间为5h,搅拌速度为300 r/min的条件下,镍离子去除率可达到85.3％,阴极电流效率为56.8％.     

SDS对两性修饰膨润土吸附Cd2+的影响

采用十二烷基磺酸钠(SDS)复配修饰十二烷基二甲基甜菜碱(BS-12)修饰的两性修饰膨润土,以批处理法研究了不同修饰比例、温度、pH和离子强度下,SDS对两性修饰膨润土吸附Cd2+的影响,并从吸附等温线、温度效应和热力学角度探讨了吸附机制.结果表明,SDS复配修饰显著增强了两性修饰膨润土对Cd2+的吸附能力,修饰土对Cd2+的吸附量呈现BS+150SDS(BS-12+150%SDS)>BS+100SDS(BS-12+100%SDS)>BS+50SDS(BS-12+50%SDS)>BS+25SDS(BS-12+25%SDS)>BS(BS-12)>CK(原土)的顺序.修饰土对Cd2+的吸附等温线符合Langmuir模型.SDS复配修饰后,温度效应由CK和BS两性修饰土的增温正效应逐渐向BS+150SDS两性复配修饰土的增温负效应转变.pH对修饰土吸附Cd2+影响不大.离子强度增加,修饰土对Cd2+的吸附能力下降,但SDS修饰比例增加可以减弱离子强度对修饰土吸附Cd2+的影响.热力学参数结果表明,修饰土对Cd2+吸附是熵增控制的自发性过程,当SDS复配修饰比例<100%CEC时,修饰土对Cd2+吸附为焓增、熵增过程;当SDS复配修饰比例≥100%CEC时,修饰土对Cd2+吸附为焓减、熵增过程.     

平菇菌糠对废水中铜离子的生物吸附性能

针对重金属污染和农业固体废弃物资源化问题,利用平菇菌糠作为吸附剂对废水中Cu2+吸附性能进行研究.通过单因素实验测定pH、吸附时间、温度、Cu2+初始浓度对吸附效果的影响;利用扫描电镜-能谱、红外光谱和X射线衍射对其吸附机制进行了初步探究.结果表明,菌糠浓度为10 g·L-1,pH为6,吸附时间为120 min,吸附温度为30℃,铜离子初始浓度为8mg·L-1的条件下,吸附率可达到74.46%,吸附容量为0.744 6 mg·g-1.实验数据较好地吻合Langmuir吸附等温模型,其相关系数为0.994 9,表明吸附过程主要为单层化学吸附.扫描电镜-能谱、红外光谱和X射线衍射分析显示,平菇菌糠吸附Cu2+过程主要为物理吸附和化学吸附,包括静电吸附、络合和配位等反应,其中起主要作用的基团为—OH、—COOH、—NH等.     

北京城区大气氮湿沉降特征研究

采用离子交换树脂法研究2012年6~10月北京五环内城区大气中不同形态氮在不同月份环路(五环、四环、三环和二环)以及功能区(文教区、环路、生活区、火车站和公园)的湿沉降差异,探索城市区域内不同形态氮在时间、空间和功能区上沉降的特征.结果表明氨氮、硝态氮和亚硝态氮的沉降均体现出明显的时间特征.其中,在研究时段内,氨氮和硝态氮沉降均呈现出先升高后降低的趋势,7月达到最大值;亚硝态氮沉降呈现出先降低后上升的趋势,9月达到最大值.大气氨氮和硝态氮沉降量受到降雨量的影响显著(P<0.05).在空间沉降特性方面,氨氮、硝态氮和亚硝态氮在不同环路上沉降没有显著的差别,环路和火车站等功能区氮沉降高于其它功能区.     

无机离子与胡敏酸对零价铁去除水中Pb（Ⅱ）、Hg（Ⅱ）的影响

研究了Ca2+、Cl-和胡敏酸(HA)对零价铁(ZVI)去除水中Pb(Ⅱ)、Hg(Ⅱ)的影响及其动力学特征,应用X-射线衍射分析(XRD)初步探讨了ZVI对Pb(Ⅱ)、Hg(Ⅱ)的去除机制.结果表明,ZVI主要通过吸附-共沉淀作用去除水中的Pb(Ⅱ),氧化还原作用去除Hg(Ⅱ).随着Ca2+浓度的增加,Hg(Ⅱ)和Pb(Ⅱ)的去除率分别呈逐渐升高和轻微下降的趋势;增加Cl-浓度有利于Hg(Ⅱ)的去除,但Pb(Ⅱ)去除率增加不明显;Pb(Ⅱ)、Hg(Ⅱ)去除率随HA浓度的增加分别呈缓慢升高和缓慢下降的趋势.当Cl-、Ca2+和HA共存时,Pb(Ⅱ)、Hg(Ⅱ)的去除率分别达到99.71%和97.95%.在Cl-、Ca2+、HA单独存在和共存时,ZVI去除Pb(Ⅱ)、Hg(Ⅱ)的过程均符合准一级反应动力学特征;Pb(Ⅱ)的去除速率常数以5 mg·L-1HA单独存在时最大(0.0240 min-1),而Hg(Ⅱ)以0.80 mmol·L-1Ca2+单独存在时最大(0.0169 min-1).     

重铬酸钾法测特定化学需氧量几种屏蔽氯离子干扰方法比较

探讨了COD为60mg/L的情况下,氯离子对测定值的影响。氯离子浓度在100mg/L时,固态硫酸汞可完全屏蔽其干扰;氯离子浓度在500 mg/L时,液态硫酸汞可完全屏蔽其干扰;绘制COD-氯离子标准曲线,屏蔽氯离子浓度可达2000mg/L,但操作较为繁琐;在水样环境单纯的情况下,用低浓度重铬酸钾法,可忽略氯离子的干扰。     

油田污水中可溶性硫化物快速检测方法

采用硫离子选择电极法快速检测油田水中硫化物,优化了操作条件,在溶液pH值大于11.5和中速搅拌（800 r/min左右）条件下,单个样品分析时间少于15 min.空气中的氧对测定结果干扰明显,通过取样时加入硫化物稳定剂方法可消除空气中氧的影响.方法的精密度小于4.0％,与碘量法相比,相对偏差小于15％,方法检测下限为0.35 mg/L.     

离子色谱法测定水中氯离子的不确定度评定

分析了用离子色谱法测试洁净水中氯离子的过程中不确定度和系统误差的来源,对各不确定度分量进行了评定及合成,并计算得出合成不确定度和扩展不确定度。结果表明,体积不确定度分量对整个试验的不确定度影响较小,质量不确定度分量相对影响较大。