pH Effect on kinetics of Heavy Metal Sorption in Soils

The pH effect on the sorption kinetics of heavy metals in soils was studied using a constant flow leaching method.The soil samples were red soil collected from Yingtan,Jiangxi,and yellow-brown soil from Nanjing,Jiansu,The heavy metals tested were zinc and cadmium.Assuming that the experimental data diffed to the following kinetic rate equation:1/c.dx/dt=kx∞-kx,the rate constant k of sorption could be determined from the slope of the straight line by plotting of 1/c,dx/dt vs.x.The results showed that the pH effect on the rate constants of heavy mental sorption in soils was very significant.The values of k decreased with increasing pH.The sorptions were more sensitive to pH in red soil than in yellow-brown soil.     

降雨空间分布不均匀性对流域径流和泥沙模拟影响研究

对降雨空间分布变化的不完全理解，以及缺乏足够的数据来描述降雨的空间分布．阻碍了分布式水文模型的发展。以黄河下游洛河卢氏水文站以上流域为研究区．在GIS技术支持下．采用目前分布式水文模型中应用广泛的Thiessen多边形法确定降雨空间分布，选取分布式水文模型SWAT(Soil and Water Assessnlent Tools)研究降雨空间分布不均匀性对流域径流和泥沙模拟的影响。结果表明雨量站密度、雨量站分布和降雨空间分布变化均对模拟结果产生了较大影响．这在一定程度上限制了分布式水文模型的应用和参数识别。此外，Thiessen多边形法对面雨量的估算结果是令人满意的，但对降雨空间分布的描述能力较差。     

pH及共存金属离子对生物质炭吸附铅稳定性的影响

生物质炭对重金属吸附性能的稳定性是评价生物质炭修复效果的重要指标。本文研究了不同pH、金属离子Cd和Al存在下,Pb在不同炭化温度(100℃、400℃、700℃)生物质炭上的脱附性能及脱附过程。结果表明,pH越低,Pb的脱附率越大。其主要是由于H~+的竞争效应,以及生物质炭表面官能团的质子化,促进了Pb的重新活化。在Cd和Al共存时,Pb的脱附率进一步增加。当pH=3.5时,Cd和Al的存在分别使Pb从CM100、CM400和ZKZ700上的脱附率提高了13.9%、1.0%、3.4%和26.8%、13.0%、11.3%。这主要归因于多金属的水解使得更多的H~+得以释放,进而促进了Pb的脱附。Pb在生物质炭上的脱附率随脱附时间的延长而不断增加,反应前4 h,脱附率迅速增加并均已达最大脱附率的70%,4 h后脱附速率减慢。Pb的脱附动力学符合伪一级动力学模型及颗粒内扩散模型(前4 h)。当Cd和Al存在时,解吸液对Cd、Al易解吸态的优先脱附降低了Pb的脱附速率并延长了其脱附所达平衡的时间。     

保护地蔬菜栽培对土壤盐分积累及pH值的影响

对辽宁省沈阳市于洪地区保护地土壤盐分含量及其离子组成和土壤pH值进行测定分析,研究保护地蔬菜栽培对土壤盐分和土壤pH值的影响.结果表明,保护地土壤的盐分含量和电导率均明显高于露地土壤,露地土壤平均盐分含量为0.29 g/kg,露地改为保护地10年左右土壤的平均含盐量上升至1.56 g/kg,相应的EC值达到0.53 mS/cm,已超过作物的生育障碍临界点(EC＞0.50 mS/cm).保护地土壤酸化趋势明显,建成保护地栽培蔬菜6年,土壤pH值从6.50降低至5.50以下,超过了蔬菜出现生理障碍的临界土壤pH5.52,保护地土壤NO-3,SO2-4,Cl-和Ca2+,Mg2+,K+,Na+等盐分离子含量均较露地土壤大大增加,但HCO-2则低于露地土壤;保护地土壤pH值的下降与NO-3,SO2-40,Cl-的大量积累关系密切,而全盐中Ca2+,Mg2+,Na+相对比例的下降在土壤pH值下降的过程中也起着重要作用.     

2种固化剂对重金属和砷复合污染底泥的稳定化处理效果

通过底泥交换态重金属和砷含量的分析以及毒性浸出测试,考察磷酸氢二铵和碳酸钙对底泥中重金属和砷的稳定化处理效果。结果表明,随着磷酸氢二铵添加量的增加底泥pH值逐步降低,随着碳酸钙添加量的增加底泥pH值逐步升高。磷酸氢二铵对底泥中Pb的稳定有良好效果,然而对Zn、As却产生了极大的活化作用。碳酸钙对底泥中Pb、Cd、Zn的稳定有良好效果,但对As的稳定没有明显作用。相对而言,碳酸钙更适合用来稳定化处理重金属和砷复合污染底泥。     

滇池沉积物金属污染及潜在生态风险研究

对滇池126个采样点沉积物0～5 cm、5～10 cm和10-20 cm中Cu、Zn、Pb、Cr、Cd、Hg和As等7种金属的含量进行了分析测定,各金属含量测定结果均高于相应的参比值,表明滇池沉积物受到了不同程度的金属污染.各金属含量的水平分布很不均衡,Zn、Pb、Cd、Hg和As含量随沉积物深度的减小而增大,Cu和Cr含量则随沉积物深度减小而减小,表明滇池沉积物中Cu和Cr污染整体上出现了减缓的趋势,而Zn、Pb、Cd、Hg和As污染在不断加剧.用H(a)k(a)nson潜在生态风险指数对滇池沉积物金属污染的生态风险进行了分析,结果表明:滇池沉积物存在轻微的Cu、Zn、Pb、Cr和As污染生态风险,以及中等的Hg和Cd污染生态风险;全湖沉积物金属污染的平均生态风险指数RI值为205.03,属中等生态风险,但有快速加大的趋势.     

土壤和沉积物中重金属形态分析

介绍了一种土壤和沉积物中重金属形态分析方法,将重金属的形态分为水溶态、弱酸态、可还原态、可氧化态和残渣态,用水提取水溶态,0.11 mol/L的醋酸提取弱酸态,0.5 mol/L的盐酸羟胺提取可还原态,过氧化氢和1.0 mol/L的醋酸铵提取可氧化态,盐酸-硝酸-氢氟酸-高氯酸提取残渣态.方法适用于Cu、Pb、Zn、Cd、Cr、Co、Mn、Mo、As、Sb、Ni等 11种重金属元素的形态分析研究,检出限在0.001 ～ 1 μg/g 之间,方法的精密度＜11%(RSD).     

四平市条子河底泥中重金属特征研究

通过1987-1995年对对四平市条子河底泥和水质的同步监测,指出四平市条子河底泥中重金属含量较高,污染河段底泥中重金属的含量比背景含量要高出1～3.97倍,年际变化出现波状起伏的特征。底泥的含量受到河流水质的酸（碱）特性和氧化特征的影响,同时受区域环境背景的影响和工业废物排放的影响。控制条子河底泥中重金属含量应采取化学和生态重建与修复的措施。     

基于SWAT模型的中尺度流域产流产沙模拟研究

以黄河下游小花间（小浪底-花园口）区域洛河卢氏水文站以上流域为研究区,在GIS技术支持下,应用分布式模型SWAT（Soil and Water Assessment Tool）进行了流域产流产沙模拟。采用卢氏水文站1992～1997连续6年的实测月均径流和泥沙数据对模型进行了校准:在模型校准过程采用自动数字滤波技术将径流总量划分为直接径流和基流,并分别对直接径流和基流进行了校准,以达到径流总量的拟合,在此基础上对流域泥沙负荷进行了校准;采用1998～1999连续2年的实测月均径流和泥沙数据对模型的适用性进     

Modeling Osmotic Salinity Effects on Yield Characteristics of Substrate-Grown Greenhouse Crops

Abstract

In a series of experiments with different osmotic potentials in the root environment, various vegetables, and ornamentals were grown in a substrate system. The osmotic potential was varied by addition of nutrients. Yield characteristics of the crop were related to the osmotic potential of the nutrient solution. Experimental results were fitted to a discontinuous piecewise linear response model introduced by Maas and Hoffman in 1977 and this study extended the investigation by introducing a polynomial and an exponential test model. The correlation coefficients for the polynomial and exponential model were generally higher than with the piecewise linear model. The polynomial model has the drawback that calculation of the salinity yield decrease (SYD) value is not possible. Salinity threshold values could be calculated with all models tested. The average values did not show great differences and the EC values found were 2.4, 2.1, and 2.2 dS m^?1 for the polynomial, exponential, and peace wise linear model, respectively. It is argued that the exponential equations showed the closest relationships between the EC in the root environment and the yield characteristics of the crops. Fifth order polynomial equations yielded at least equal or even higher correlation coefficients, but these equations are very responsive to accidental positions of observations. The traditional discontinuous linear fitting gave reasonable results, but only when experimental observations below the threshold value were selected and discarded. This undermines the power of this model, because exclusion of observations is always arbitrary. Furthermore, a discontinuous relationship between crop yield and EC in the root environment is not likely, because yield response is of biological nature. Nevertheless, when the number of observations is not sufficient for the quantification of the exponential equation, mostly reasonable estimations of the salinity parameters can be obtained with the Maas and Hoffman model.     

Heavy Metal Fractionation and Extractability in Dredged Sediment Derived Surface Soils

The objective of this study was to characterise pollution with heavy metals in surface soils sampled at various dredged sediment disposal sites in the Flemish region (Belgium). The sites selected varied in the period since sediment disposal ceased and in current vegetation and land use. Total metal contents (Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn) in the surface soils varied widely. For some disposal sites Cd and Zn concentrations greatly exceeded reference values for clean soil. The distribution of the metals as determined by sequential extraction differed between elements, but was simular for all the soils. This suggested that metals in these sediment derived surface soils were accumulated and transformed in a similar way. Residual fractions were low compared to total contents (2 – 4% for Cd, 25% – 35% for Co, 7 – 18% for Mn, 4 – 22% for Zn, 12 – 41% for Ni, 11 – 42% for Pb, 20 – 45% for Cu, < 10% for Zn). High metal concentrations in the acid-extractable and reducible fractions may indicate pollution from anthropogenic sources. DTPA-extractable metals, which may be considered indicative of plant-available contents, were relatively high compared to the total contents. The relative extractability, expressed as the ratio of DTPA-extractable to total contents, decreased in the order Cd (38%) > Cu (28%) = Zn (26%) > Pb (13%) > Ni (10%) > Co (3%). Most of the sites studied would be of concern if they were used for agricultural activities. No trends in metal availability in the period following disposal were apparent from the data.     

黄土高原典型流域水沙关系对退耕还林(草)的响应

利用北洛河上游吴旗站实测水文资料,采用Pettitt、Mann-Kendall非参数检验以及流量历时曲线等方法,对比1963-1979年水沙特征,分析了1980-2002年间水土流失综合治理,尤其2003-2011年间退耕还林(草)工程实施等效应背景下流域水沙行为的变化规律。结论表明,近50a来,流域水沙量均呈显著减少趋势。对比1963-1979年,1980-2002年间平均径流量和平均输沙量分别减少了22.80%,45.63%,2003-2011年间减少幅度更大,分别达到53.03%,89.33%。三阶段5%,50%概率时的丰水、平水期径流量和输沙量均呈下降趋势,输沙量的减少幅度更大,而枯水期的基流量为逐阶段增加趋势,输沙量则在2003-2011年间完全消失。三阶段的年尺度水沙关系,在2003-2011年间发生了统计上的显著变化。与1963-1979年间比,单位径流的产沙能力,1980-2002年间降低了12.80%,流域泥沙赋存量减少了17.27%,而2003-2011年间则分别减少了约1/4和1/3。月尺度含沙量-流量关系表现为"8"字环形,环的延展度逐阶段下降,尤其在2003-2011年间降低幅度最大。50a来,在不断的水土流失综合治理,尤其退耕还林(草)工程实施推动下,流域径流量和输沙量、径流和输沙情势、年/月水沙关系均表现为逐阶段减少、降低或动力削弱状态。表明,退耕还林(草)生态工程发挥了良好的蓄水保土、增加基流、削弱侵蚀、减少泥沙输移的良好的生态功能和效益。     

降雨产沙资料整理方法对两者关系的影响

合理的水土流失资料整理方法是挖掘数据内在规律的基础,通过采集江西省赣县花岗岩次生马尾松林地不同植被恢复类型小区2010—2011年2 a的降雨产沙资料,研究了4种整理方法对降雨产沙关系的影响。结果表明:加大资料整理的时间尺度和降雨间隔时间,可以显著提高降雨产沙之间的相关性,同时整理方法对拟合曲线的性质产生影响,综合考虑拟合优度和曲线性质的一致性,可以采取周晴方法的幂函数来描述不同类型小区降雨产沙之间的内在关系;植被恢复减弱了产沙速率,随着降雨量的增加,纯林小区的产沙速率下降,百喜草恢复小区变化缓慢,低郁闭度胡枝子恢复小区增加迅速,因此侵蚀严重的林地应首先实施草本植被恢复,逐步实现乔灌草生态结构恢复。     

The Effect of Salinity on Tire Leachate Toxicity

Previous whole animal bioassays with scrap tireleachates demonstrated an antagonistic interactionbetween salinity and toxicity, but it is unknown ifthe effect is due to an interaction between saltsand toxic mode of action, or release of toxicantsfrom the rubber matrix. Microtox® bacterialluminescence bioassays were performed on tireleachate solutions in a gradient of salinities from0 to 25 ppt to assess salt/toxicant interactions.Leachate solutions generated at specific salinitieswere amended to higher salinities to assess theeffect of sea salt on toxicity vsleachability/solubility of toxicants. Salineleachate solutions were also diluted with freshwaterleachate. Original leachates and samples amendedwith additional salt were aged for 8 days andretested to assess longer term interactions betweensalt and toxicants. The toxicity of leachatesdecreased with increasing salinity up to 15 ppt,with no significant change at higher salinities.Adding sea salt to leachate solutions did notimmediately decrease toxicity significantly, exceptfor samples starting at zero salinity. This wasinterpreted as an indication of interaction betweensea salt and the toxic constituent(s) in theleachate. Salinity decreases also indicated a directeffect of sea salt on toxicants. Ageing samplesindicated a long term interaction between sea saltand leachate toxicants, but not degradation, over atleast a two week period. Tire leachates are probablya greater threat to freshwater habitats thanbrackish or marine habitats, but bioaccumulation ofpersistent organic contaminants from tires is an unknown.     

pH对闽江河口湿地沉积物氮素转化关键过程的影响

以闽江河口湿地沉积物为研究对象,通过单变量的沉积物培养试验(pH=2.5,3.5,4.5,5.5,6.5),研究pH对湿地沉积物氮元素硝化、反硝化、矿化3个关键过程的影响。结果表明:低pH(pH=2.5)对硝化活性有明显的抑制作用,其余pH对沉积物的硝化速率影响不大,硝化细菌的数量和活性在强酸条件下限制明显。随时间推移,沉积物反硝化速率减小,反硝化活性增强。偏酸条件对反硝化活性有一定抑制作用,主要由于沉积物中反硝化细菌在酸性条件下不活跃或耐酸细菌数偏少。不同pH条件下,矿化速率基本无规律可循,表明pH对湿地沉积物矿化过程无直接影响。     

基于实测高光谱和Landsat 8 OLI影像的土壤盐化和碱化程度反演研究

针对宁夏银北地区土壤盐碱化定量监测的需要,利用实测土壤高光谱和Landsat 8 OLI多光谱影像数据采用多项式、多元线性回归等方法进行土壤含盐量和pH值反演研究,并对影像光谱反演模型进行校正,以提高遥感定量反演精度。结果表明:(1)基于实测光谱的土壤含盐量反演精度均高于基于OLI影像反演精度;基于实测光谱敏感波段反射率反演精度高于实测盐分指数反演精度,其中实测光谱经平滑后敏感波段建立的模型效果最佳(R²=0.695)。(2)基于实测光谱平滑后敏感波段建立的pH值反演模型精度最高且最稳定(R²=0.545),基于OLI影像光谱反演精度低于实测光谱,但也通过了显著性检验和精度验证。(3)经实测光谱模型校正后的Landsat 8 OLI影像光谱的土壤含盐量反演模型R²从0.347提高到0.623。研究结果可以为准确、快速地定量监测当地土壤盐分含量、pH值的变化提供科学依据和技术手段。     

重金属在土壤载体中的行为和环境响应

综述了21世纪初重金属在土壤环境中发生的吸附/解吸、溶解/沉淀、氧化/还原、络合(螯合)等行为的影响因素,如粘土矿物类型、微生物、腐殖质、pH、重金属性质、土壤酶和人为活动等方面的研究结果,得到了比较深入的进展。同时也显现了在复杂的野外条件下,重金属的行为特征研究明显不足;与植物的吸富关系研究尚处于起步阶段;不同区域和土壤类型中重金属及其化合物的行为差异缺乏科学的解释;重金属污染土壤的修复技术还存在风险;重金属复合污染研究也需进一步定量化。     

新疆克里雅绿洲土壤盐分、pH和盐基离子空间异质性分析

以克里雅绿洲盐渍化土壤为研究对象,以野外调查与实地数据为基础,采用空间自相关分析与径向基函数插值法,定量分析了克里雅绿洲土壤的含盐量、pH及盐基离子的空间异质特征。结果表明:绿洲盐渍土表聚性强、呈碱性,土壤含盐量从南至北呈现逐渐增大趋势。土壤含盐量、Na~+、Ca(2+)、K~+、Mg2~+、Cl–、SO_4~(2-)均属于强空间变异,HCO_3~–属于中等强度的空间变异,而pH属极弱变异。土壤盐分含量、pH和盐基离子的Moran’s I指数均通过了显著性检验,研究区土壤含盐量、p H与盐基离子在空间上呈现低聚集性。Pearson相关性分析结果显示,土壤盐分含量与Na~+、K~+、Cl~–和SO_4~(2-)含量具有强正相关性(P0.01),与Ca~(2+)和Mg~(2+)含量中等程度正相关(P0.05);土壤pH与土壤含盐量及盐基离子含量极弱相关。该研究结果可为绿洲水资源合理开发与农业可持续发展提供科学依据,同时可作为盐渍土改良和沙漠化防治等环保工作的决策支撑。     

丹河水系表层沉积物重金属污染及生态风险评价

采用原子吸收分光光度法和原子荧光光谱法,测定了丹河水系干流及主要支流表层沉积物中重金属（Mn、Zn、Cu、Pb、Cd、Cr、Hg、As）的含量,同时用沉积物质量基准法（SQG）和Hakanson潜在生态风险指数法,对重金属的毒性效应、污染程度及潜在生态风险进行了评价,并分析了重金属的主要来源。结果表明,丹河水系表层沉积物中Mn、Zn、Cu、Pb、Cd、Cr、Hg、As的平均含量分别为115.1、18.78、8.46、6.49、2.85、60.6、0.047、14.22mg·kg-1。Cd、As和Cr的含量介于最低效应水平（LE-L）与严重效应水平（SE-L）之间。根据SQG,丹河表层沉积物中重金属含量处于中度污染水平,可能会对河流生物产生一定的毒性效应,而Pb、Cu、Zn则尚无毒性效应。除了As和Cr之外,其他重金属元素之间均呈现较明显的正相关,表明在沉积物中这些重金属的含量具有共同的变化趋势,且具有一定的同源性。工业排污是造成丹河水质恶化的主要原因之一,也是重金属的主要来源。以山西省土壤背景值为参比进行Hakanson潜在生态风险指数评价发现,丹河水系表层沉积物呈现由强至极强的生态风险,其中Cd生态风险最大,Hg、As次之。对单个重金属的潜在生态风险系数和多个重金属的潜在生态风险指数进行分析显示,生态风险较大的样点是高平市、巴公河和水东。研究结果旨在得到单一污染物的环境影响和多种污染物的综合效应的评价结果,为丹河水系沉积物及水体重金属污染防治和决策管理提供科学依据。     

Assessment of Salinity Variations in TBT Adsorption onto Kaolinite and Montmorillonite at Different pH Levels

Adsorption onto solid phases is an important process in controlling the distribution of toxic tributyltin (TBT) compounds in aqueous systems. In the present study, the TBT adsorption onto two types of clay, kaolinite (KGa) and montmorillonite (SWy), as a function of salinity (0, 8, 16, 24, 32‰) was investigated using the conventional batch technique. Experiments were carried out under different pHs (4, 6 and 8). For the different clay types examined, the highest TBT adsorption was found at a salinity of 0‰ and pH 6. In general, the TBT adsorptiondecreased with increasing salinity due to the growing competition with metallic cations to the surface sites of the clay minerals. Only at pH 4, the TBT adsorption onto kaolinite did not show any effect by changing the salinity. This was attributed to the pH_ZPC of 4.9 determined for the kaolinite sample. The results clearly demonstrated the importanceof identifying and characterizing the sorbents and determining the environmental conditions, in order to predict TBT distribution in natural systems or to compare partitioning coefficients of TBT ontosediment phases from different locations.