稻草生物质炭对3种可变电荷土壤吸附Cd（Ⅱ）的影响

按土重的3%和5%向采自海南和广西的3种可变电荷土壤中添加由稻草制备的生物质炭,混合培养30 d后用一次平衡法研究了生物质炭对土壤吸附Cd（Ⅱ）的影响及其与土壤表面电化学性质的关系,旨在阐明生物质炭促进可变电荷土壤吸附和固定Cd（Ⅱ）的机制。结果表明,添加稻草炭显著提高了3种土壤的阳离子交换量（CEC）和土壤pH,并使土壤胶体Zeta电位向负值方向位移。因此,添加稻草炭增加了土壤表面的负电荷量,土壤表面对Cd（Ⅱ）的吸附容量增强,使3种可变电荷土壤对Cd（Ⅱ）的吸附量增加,且Cd（Ⅱ）吸附量的增幅随稻草炭添加水平的提高而增加。Freundlich方程和Langmuir方程可以拟合3种土壤对Cd（Ⅱ）的吸附等温线,但Freundlich方程拟合效果更好,该方程表征吸附容量的常数k也随着稻草炭添加水平提高而增大。研究表明在pH3.0~5.0范围内,稻草炭均增加土壤对Cd（Ⅱ）的吸附量。添加稻草炭提高土壤pH,促进Cd（Ⅱ）的吸附,因为Cd（Ⅱ）的吸附量随pH升高而增加。解吸实验表明,添加稻草炭处理Cd（Ⅱ）的解吸量高于对照处理,说明生物质炭提高了土壤对Cd（Ⅱ）的静电吸附量。     

秸秆炭和沸石对土壤吸附Cd(Ⅱ)的影响

为了比较2种类型改良剂对土壤中Cd(Ⅱ)的修复作用,向土壤中添加0.5%和2%的秸秆炭和沸石,培养60d后分析土壤性质的变化,并用一次平衡法研究秸秆炭和沸石对土壤吸附Cd(Ⅱ)的影响。结果表明,添加秸秆炭和沸石均能提高土壤CEC,秸秆炭还可以显著提高土壤pH,0.5%和2%添加量使土壤pH提高0.37和0.66,添加沸石对于土壤pH没有明显提高。等温吸附实验结果表明,添加秸秆炭和沸石均可以增加土壤对Cd(Ⅱ)的吸附量,并且随着添加量的增加而增加,当Cd(Ⅱ)初始浓度为150mg/L时,Cd(Ⅱ)的吸附量提高8.5%~32.5%。随着体系pH的升高,土壤对Cd(Ⅱ)的吸附量增加,在pH较高的体系下,秸秆炭对土壤吸附能力的促进作用更大。解吸实验表明,添加秸秆炭和沸石后土壤Cd(Ⅱ)的解吸量高于对照,说明秸秆炭和沸石提高了土壤对Cd(Ⅱ)的静电吸附量。Freundlich方程更适合拟合添加秸秆炭和沸石后土壤对Cd(Ⅱ)的吸附等温线,R2值均在0.96以上。从该方程表征吸附容量的参数Kf可以看出,秸秆炭促进Cd(Ⅱ)的吸附效果优于沸石,2%添加量的促进效果要优于0.5%添加量。因此,对于辽宁地区的草甸土,秸秆炭对土壤中Cd(Ⅱ)具有更好的修复作用。     

不同pH下两种可变电荷土壤中Cu(II)、Pb(II)和Cd(II)吸附与解吸的比较研究

对两种可变电荷土壤的研宄表明,土壤对Cu(Ⅱ)、Pb(Ⅱ)和Cd(Ⅱ)的吸附量均随pH的增加而增加,但Cu(Ⅱ)与Pb(Ⅱ)吸附量之间的差值随pH增加而减小,Cu(Ⅱ)和Pb(Ⅱ)与Cd(Ⅱ)吸附量之间的差值随pH增大呈增大趋势.土壤吸附的Cd(Ⅱ)的解吸量随吸附平衡液pH的增加而增加;但Cu(Ⅱ)和Pb(Ⅱ)的解吸量先随pH增加而增加,在某一pH时达最大,随后再逐渐减小.3种重金属离子在可变电荷土壤中吸附和解吸行为的不同特征是pH导致的土壤表面电荷的变化和离子水解程度的变化共同作用的结果.本文的研究结果对可变电荷土壤中重金属的控制和污染土壤的修复具有一定的指导意义.     

海泡石对典型水稻土镉吸附能力的影响

通过吸附解吸实验研究了添加海泡石后典型水稻土对Cd的吸附解吸特性及其对吸附溶液pH值变化的响应。结果表明,Freundlich方程可以较好地拟合红黄泥、黄泥田和红沙泥3种典型水稻土对Cd的等温吸附过程（R2〉0.962）。在溶液初始Cd浓度相同的情况下,添加海泡石可使3种水稻土对Cd的吸附量增加20%以上,增强土壤对Cd的吸附强度,有效降低吸附Cd的解吸率,其效果随海泡石添加量的增大而增强。3种水稻土吸附Cd的解吸率均高于70%,而且都随吸附量的增加而上升。溶液的pH值是影响土壤吸附Cd的一个重要因素,在低pH值的条件下（pH〈4）,随着溶液pH值的降低,土壤对Cd的吸附量迅速降低,当溶液pH值高于5时,pH值的变化对吸附量的影响较小。在溶液初始pH值2-8范围内,添加海泡石均能有效提高3种水稻土对Cd的吸附能力。     

生物质炭对茶园土壤水溶性氟吸附特性的影响

采用室内培养试验法对添加生物质炭的茶园土壤水溶性氟吸附特性进行了研究。结果表明,茶园土壤随生物质炭添加量增加对水溶性氟的吸附量和吸附率均逐渐降低,应用等温吸附Langmuir方程、Freundlich方程和Temkin方程均能够较好地描述其吸附规律,其中以Freundlich方程拟合曲线最佳。随生物质炭添加量的增加土壤氟净吸附量逐渐降低。各处理土壤的氟吸附动力学过程包含吸附快反应和慢反应阶段,平衡时间小于120 min区间为吸附量快速上升期,平衡时间达到1 440 min后0.25%和0.50%生物质炭添加量处理土壤基本达到平衡状态。从双常数方程、Elovich方程和一级动力学方程拟合方程计算得到的理论吸附量与试验实测吸附量之间的符合程度较高,可准确描述添加生物质炭土壤对水溶性氟的吸附过程。添加生物质炭使土壤p H值升高与茶园土壤对水溶性氟最大吸附量、吸附强度和净吸附量的降低密切相关。     

水稻秸秆生物质炭对土壤磷吸附影响的研究

以水稻秸秆为原料,分析了不同热解温度下所制备的生物质炭的性质,并采用批处理法,分析了生物质炭添加量和不同热解温度制备的生物质炭对土壤磷吸附特性的影响。结果表明:随着热解温度的升高,生物质炭的碳化程度、比表面积和磷含量增加。添加生物质炭显著减少了土壤对磷的吸附量,而且随着生物质炭热解温度的增加,土壤对磷的吸附量显著增加。Langmuir方程和Freundlich方程都能够较好地拟合添加生物质炭土壤的磷等温吸附曲线。准一级动力学方程和准二级动力学方程可较好地描述添加生物质炭土壤的磷吸附动力学行为。通过以上研究结果可知,水稻秸秆生物质炭可以减少土壤对磷的吸附并增加土壤有效磷的含量,因此在土壤磷肥肥效改良方面具有一定的应用潜力。     

添加H2O2改性和HNO3/H2SO4改性生物质炭对一种酸性水稻土吸附Cd (Ⅱ)的影响

选择稻草、玉米秸秆和油菜秸秆作为制备生物质炭的原料，分别用H2O2和HNO3/H2SO4对生物质炭进行改性处理，以未改性的生物质炭和HCl处理的生物质炭作为对照。按土重3%的比例向采自安徽郎溪的酸性水稻土中添加上述生物质炭，在经历一个干湿交替周期后，进行Cd(Ⅱ)吸附/解吸实验，研究添加生物质炭对水稻土吸附Cd(Ⅱ)的影响及其机制。结果表明，两种改性方法均有效增加了生物质炭表面的质子结合位点数，且HNO3/H2SO4改性对生物质炭表面羧基官能团的扩增效果更显著。官能团的增加使得添加了HNO3/H2SO4改性生物质炭的水稻土对Cd(Ⅱ)的专性吸附能力显著增强。因此，添加HNO3/H2SO4改性生物质炭可以作为酸性水稻土吸附固定重金属Cd的一种新型方法。     

不同热解温度茶渣生物质炭对茶园土壤吸附解吸NH4-N的影响

生物质炭对铵根的吸附解吸影响着土壤的固氮效果,为探讨茶渣生物质炭对茶园土吸附—解吸NH_4~+—N性能的影响,减少土壤中氮素的淋失,提高氮素利用效率,通过模拟培养试验,采用平衡吸附法及HCL解吸法,研究了不同热解温度下制备的茶渣生物质炭在不同添加比例(0.35%,0.70%,1.40%,2.80%)下,茶园土对NH_4~+—N吸附解吸的特性。结果表明:施用生物质炭能有效增强茶园土对NH_4~+—N的吸附,并随生物质炭添加量的增加而增强。同一生物质炭添加量下,4种生物质炭处理下茶园土对NH_4~+—N的吸附量大小表现为BC400BC300BC500BC600。生物质炭的CEC含量是影响土壤吸附NH_4~+—N能力的主要因素。土壤对NH_4~+—N的吸附过程均以Langmuir方程拟合达到显著水平(0.953 7R~20.995 5),以单层吸附为主。施用生物质炭后,土壤产生了解吸滞后,有效降低了茶园土对NH_4~+—N的解吸率,BC400的解吸率最低。茶渣生物质炭能够增强土壤对NH_4~+—N的吸附,降低对NH_4~+—N的解吸,有利于提高土壤对氮素的吸持能力,其中BC400,2.80%处理下效果最佳。     

酸性条件下粉砂质壤土对Cd~(2+)的吸附解吸特性研究

为了解酸性条件下粉砂质壤土对Cd2+的吸附-解吸机制,采用一次平衡法进行了不同pH值条件下壤土对Cd2+的吸附-解吸实验。结果表明:壤土对Cd2+的吸附量和吸附率均随着pH值升高而增加,不同初始浓度下达到的最大吸附率为0.69~0.95,酸性条件下壤土对Cd2+的等温吸附Freundlich方程拟合效果最好,通过拟合的Langmuir方程计算出壤土对Cd2+的饱和吸附量为2 500 mg/kg。Cd2+的解吸量和解吸前的吸附量呈显著正相关线性关系,解吸率随着pH值升高而减小,pH值从2以等间隔1变化到6,平均解吸率依次为1.11、0.33、0.07、0.06、0.06;表明在酸性污水灌溉条件下污灌壤土中的镉易向下迁移,污染深层土壤和地下水。     

可变电荷土壤和恒电荷土壤CI^—吸附特性的研究

对不同浓度KCI和不同pH下，3种可变电荷土壤和4种恒电荷土壤CI^-吸附量进行了测定。结果表明，土壤CI^-吸附量随平衡CI^-浓度C（e）增加而增大，恒电荷土壤呈线性，可变电荷土壤在添加CI^-0.5-5.0mmol/L下，符合Langmuir吸附等温式。同一浓度下的CI^-吸附量及其随浓度增加的速率均为砖红壤＞红壤＞赤红壤＞黄棕壤＞棕壤、暗棕壤和黑土，与这些土壤所带正电荷量顺序相一致。Langmuir方程K值较小且几种土壤差异不大。恒电荷土壤对CI^-的吸附量很小，在浓度较低时常出现负吸附，其吸附机理可能更多的是与K^ 吸附时的同时吸附。7种土壤CI^-吸附量均随pH增加而降低，但降低强度可变电荷土壤远大于恒电荷土壤。     

Cd和Zn在滇池沉积物中的吸附-解吸特征

研究了Cd和Zn在滇池沉积物中的吸附-解吸特征并分析了影响其吸附的因素。结果表明滇池沉积物对Cd和Zn的等温吸附符合Langmuir模型,且Cd和Zn的最大吸附量很高,Cd为6443mg/kg,Zn为13889mg/kg,这表明滇池沉积物对重金属具有很大的吸附潜力。Cd和Zn的吸附和解吸过程都可以分成30min之前的快反应和60min之后的慢反应,且吸附率和解吸率与时间的关系都可以用乘幂函数拟和。沉积物对重金属的吸附受pH的影响,吸附量随着pH的增加而增加,当溶液pH为8.05时,Cd和Zn的吸附百分数都超过了97%。     

蛋白核小球藻对铅、镉和汞吸附速率及其影响因素的研究

通过吸附时间、藻细胞密度和重金属浓度等参数条件的变化,研究蛋白核小球藻（Chlorella pyrenoidosa）对海水中Pb2＋、Cd2＋和Hg2＋的吸附。结果表明,蛋白核小球藻对Pb2＋、Cd2＋和Hg2＋的吸附率分别在2～4d内快速升高后趋于平衡,而吸附量在第1d达到最大值后逐渐变小。藻细胞密度为1×106cell·mL-1时,吸附量最大,当藻细胞密度达到4×106cell·mL-1时,吸附率增幅减小并趋于平衡。随着Pb2＋、Cd2＋和Hg2＋浓度升高,吸附率呈逐渐变小趋势,吸附量却增加。蛋白核小球藻吸附Pb2＋符合Freundlich等温线方程,而吸附Cd2＋和Hg2＋符合Dubimim-Radushkevich等温线方程。蛋白核小球藻对Pb2＋、Cd2＋和Hg2＋的最大吸附量分别为4.84、37.7mg·L-1和5.61μg·L-1,吸附能力顺序为Cd2＋〉Pb2＋〉Hg2＋。     

Isolation of Cadmium-Resistant Bacteria and Their Resistance Mechanisms

In the first series of studies aimed at addressing the environmental problems of soils and drainage systems, we attempted to isolate cadmium (Cd)-resistant bacteria from soils heavily contaminated with Cd and determine their growth rate in media with cadmium. In soils contaminated with heavy metals, there was on increase in the number of Cd-resistant bacteria. Among 14 Cd-resistant bacteria isolated from soils contaminated with heavy metals, only six strains (Flavobacterium sp., Comamonas testosteronii, Methylobacterium fujisawaense, Alcaligenes piechaudii, Alcaligenes xylosoxidans) were identified as new types of Cd-resistant bacteria. All the isolated resistant bacteria grew fast, and reached the maximum growth rates within 24 to 48 h (Growth conditions were as follows. Culture medium: nutrient broth, pH: 6.0, temperature: 30°C and of concentration of added Cd: 0.1, 1.0, 10.0, and 100.0 mg kg^-1).     

Self-purification of agrosoddy-podzolic sandy loamy soils fertilized with sewage sludge

Sandy loamy agrosoddy-podzolic soils and plants growing on them were studied. The soils had been treated with sewage sludge from the Lyubertsy aeration station applied as organic fertilizer for 5–10 years before 1990. Initially, these soils were used for cultivating vegetables and fodder crops. The content and mobility of heavy metal compounds increased in the plow horizons of studied soils under the influence of sewage sludge. The concentrations of Cd and Zn exceeded the tentative permissible concentrations (TPC) for these elements by 8–16 and 2–4 times, respectively. The contaminated layer was found at the depths within 30–50 cm, which attests to a low migration rate of heavy metals added to the studied soils with sewage sludge (SS) 25 years ago. The concentration of Cd exceeded the maximum permissible concentration (MPC) of this element in all vegetable and fodder crops cultivated on the studied soils. The content of heavy metals in plants differed by three–five times in dependence on the capacity of particular plants to accumulate them. The period of soil self-purification from heavy metals was found to depend on the soil contamination level and element mobility, as well as on the element removal with harvested crops and with soil water flows. The maximal time of achieving the normal level of Cd concentration was estimated as 288 years for maximally contaminated soils; the corresponding values for Cu and Zn were estimated as 74 and 64 years, respectively.     

Adsorption isotherms of some heavy metals under conditions of their competitive adsorption onto highly calcareous soils of southern Iran

Recently, application of sewage sludge or effluents resulted in raising the concentrations of some heavy metals in some agricultural soils of Iran. Experiments were conducted to evaluate the competitive adsorption of lead (Pb), copper (Cu), zinc (Zn), and cadmium (Cd) on six calcareous soils. Adsorption characteristics were evaluated by equilibration of 1 g of each soil sample with 20 ml of 0, 10, 20, 30, 40, 50, 100, or 200 mg L^?1 of their nitrate solutions and 0.01 M NaNO₃ as background electrolyte. Furthermore, solid/liquid distribution coefficients (K_d) of studied metals, as an index of soil capacity to resist a change of the soil solution concentration, were calculated. Results indicated that amounts of adsorbed Pb, Cu, Zn, and Cd increased with increase in their concentrations in the contact solutions, but this trend was more pronounced for Pb and Cu than the others. For all studied soils and metals, Langmuir equation described the adsorption behavior fairly well. Furthermore, Langmuir and Freundlich equation parameters were positively correlated to cation exchange capacity (CEC) and smectite contents; whereas, they were negatively correlated to sand content. Considering K_d values, the selectivity sequence of the metal adsorption was Pb > Cu > Zn > Cd. Therefore, the risk of leaching and also plant uptake of Zn and Cd will be higher as compared to those of the other elements.     

山东省露地蔬菜产地土壤重金属含量的环境质量分析与评价

对山东省露地蔬菜产地的土壤进行了重金属Cd、Hg、As、Pb、Cr、Cu、Zn和Ni含量的抽样调查分析,并采用单项质量指数与综合质量指数相结合的方法对重金属的环境质量状况进行了评价。结果表明,莱阳露地蔬菜产地、金乡大蒜、章丘大葱产地土壤各重金属的平均含量均低于＂食用农产品产地环境质量评价标准＂（HJ332—2006）规定的限值,三地土壤重金属的单项质量指数均≤0.7,综合质量指数分别为0.56、0.50和0.43,土壤环境质量均为1级,属于清洁水平,适宜发展无公害蔬菜。同时发现,部分地区有重金属含量超标现象,莱阳Cu的样本超标率为13.64%,金乡Cd、Cu和Hg的样本超标率分别为5.41%、5.41%和2.70%,章丘Ni的超标率为4.76%。重金属含量之间多呈正相关关系,其中Cd与Zn,Cu与Zn,Pb与Cr之间的相关性达到极显著水平（P〈0.01）,As与Ni,Ni与Zn,Zn与Pb,Pb与Cu,Cu与Cr之间的相关性达到显著水平（P〈0.05）。大部分监测点的重金属含量均高于山东农业土壤自然背景值,表明在监测点土壤中产生了重金属累积。对山东省其他露地蔬菜产区土壤的随机调查,没有发现重金属含量超标。     

Assessing cadmium availability of contaminated saline-sodic soils as influenced by biochar using the adsorption isotherm models

ABSTRACT

In arid/semi-arid regions, soil salinization, sodification and contamination by heavy metals (HMs) are the main constrains to plant growth, crop production and human health. Biochar can affect soil behaviors, e.g. adsorption of HMs that is one of the most effective techniques for reducing their bioavailability. Effect of three levels (0%, 2% and 4% wt) of sugarcane bagasse-derived biochar and two cadmium (Cd) levels (0 and 50 mg Cd kg^?1 soil as Cd(NO₃)₂) on Cd adsorption of saline, sodic, saline-sodic and normal soils were evaluated through studying adsorption isotherms. Six isotherm models were fitted to the data and the best model were chosen. The maximum Cd adsorption (694 mg kg^?1) obtained in sodic soils without biochar treatment. Cadmium removal decreased when dosage of the applied biochar increased. The minimum Cd removal obtained as 17%, 21%, and 23% in control, 2% and 4% biochar-treated saline soils, respectively. Biochar increased Cd adsorption in salt-affected soils. Increasing pH in soil solution after biochar addition resulted in an increase in net negative surface charge and the affinity of soil particles for Cd adsorption. Consequently, 2% biochar could ameliorate Cd contamination. However, Cd adsorption decreased when dosage of the applied biochar increased from 2% to 4%.     

长链两性修饰土对Cd2＋的吸附动力学

以两性表面修饰剂十八烷基二甲基甜菜碱（BS-18）修饰的塿土土样为研究对象,在Cd2＋单一条件和与苯酚共存的复合条件下,通过不同的速度参数研究了修饰土样对Cd2＋的吸附动力学特征,并对吸附机制进行探讨。结果显示,在20℃和40℃温度下单一、复合两种处理的条件下,不同修饰比例BS-18修饰土样的各速度参数均大于未修饰土样,且总体上均随着修饰比例的增加而增大,表明修饰可以显著加快塿土土样对Cd2＋的吸附速度;吸附反应分为快速反应和慢速反应2个阶段,总反应平均速度Vt由快速吸附反应速度Vf和慢速吸附反应速度Vs共同决定;温度升高,单一处理Cd2＋的总反应平均速度基本不变,复合处理则下降;加入苯酚可以加快Cd2＋的总反应平均速度,40℃时则表现为抑制效应。Cd2＋吸附速度的描述以双常数方程动力学模型为最佳模型,模型参数A、B值可以用来描述吸附速度的大小。     

Adsorption of Cadmium by Indian Soils

Adsorption behaviour of cadmium (Cd) in soils is an important process which exerts a major influence on its uptake by plant roots. Thirteen soils from various parts of India (tropical region), their pH ranging from 4.2 to 8.4, were subjected to Cd treatment at various concentrations (1 to 100 μg ml-1) and equilibrated at room temperature (25 ± 1 °C). The Cd adsorbed by each soil was calculated as the difference between the amount of Cd present in the solution initially and that remaining after equilibration. Results indicated that the adsorption capacity of the soils for Cd increased with an increase in the pH or alkalinity of the soils. The rate of adsorption was, however, found to decrease with increased pH. All the 13 soils used in this study followed linear and Freundlich adsorption isotherms with highly significant positive correlations (r). The neutral and alkaline soils also followed the Langmuir adsorption isotherm, the adsorption maxima being lowest for the neutral soil and highest for the alkaline soil. The adsorption data, in general, indicated that Cd was in a fixed form at higher pH levels. The results are generally similar to those of the temperate regions; however, Cd adsorption capacity of tropical vertisols was comparatively higher than those of temperate vertisols.