膨润土和沸石在镉污染土壤治理中的应用

采用通过盆栽试验,研究了膨润土和沸石对镉污染土壤的治理效果。结果表明,施加膨润土后不同污染程度土壤的交换态、碳酸盐结合态镉的质量分数都有所下降,铁锰氧化物结合态、有机结合态和残渣态镉的质量分数则有所上升。沸石和膨润土对轻度、中度镉污染土壤都表现出钝化作用,对重度镉污染土壤,膨润土对镉的钝化效果明显,而沸石却起到了激活镉的作用。在不同程度镉污染土壤上,膨润土可增加乌塌菜的生物量,并可抑制其对镉的吸收,降低乌塌菜植株体内镉的浓度,对乌塌菜的生长具有显著的促进作用。沸石对轻度和中度镉污染土壤均可降低乌塌菜植株体内镉的浓度,促进乌塌菜的生长并增加其生物量;对重度镉污染土壤,沸石对乌塌菜的生长影响较小,乌塌菜植株体内镉的积累显著增加。     

生物炭与沸石混施对不同污染土壤镉形态转化的影响

采用室内培养模拟了低(1.0 mg/kg)、高(10 mg/kg)镉污染的土壤,通过向镉污染土壤中添加0.4%,2%,10%的1∶1的生物炭和沸石的混合物,探究了生物炭及沸石混施对不同程度镉污染土壤的pH和镉形态变化的影响。结果表明:2种不同程度镉污染土壤的pH均较CK有所提高,且随钝化剂用量的增加而增大。随着培养时间的延长,低污染土壤pH呈现降低趋势,而高污染土壤pH先升高后降低最后趋于稳定。培养后期,低污染和高污染土壤在混合物添加量分别为2%和10%时有效态镉降低比例最大,降低比例分别为56.78%和27.33%。各处理土壤随生物炭和沸石混合物添加量的增加交换态镉降低比例逐渐增大,培养后期,低污染土壤的交换态镉较CK分别降低8.35%,13.81%,20.65%,高污染土壤的交换态镉较CK分别降低10.02%,22.34%,33.01%。各处理的钝化剂能够明显的降低交换态镉的含量,增加碳酸盐结合态、铁锰氧化物结合态、有机结合态和残渣态镉的含量,低污染土壤的有机结合态明显高于高污染土壤。由此可见,生物炭与沸石混施能够降低土壤重金属的生物有效性,为农田土壤修复奠定了理论基础。     

秸秆炭化后还田对不同镉污染农田土壤中镉生物有效性和赋存形态的影响

通过土壤培养试验和生物盆栽试验,研究不同镉污染土壤上作物秸秆炭化后还田对不同镉污染土壤中镉的赋存形态和生物有效性影响,结果表明：在碱性的镉污染土壤上,秸秆炭化后还田降低了玉米地上部生物量,但对玉米地上部镉含量和镉吸收量无显著影响;在酸性的模拟镉污染土壤上秸秆炭化后还田对玉米生长无影响,但还田含镉的油菜秸秆黑炭显著增加了玉米地上部镉含量和镉吸收量;还田不含镉的玉米秸秆黑炭对镉污染土壤中DTPA提取态镉含量没有明显影响,但还田含镉的油菜秸秆黑炭显著增加了镉污染土壤中DTPA提取态镉含量;施用含镉的油菜秸秆黑炭增加了镉污染土壤中水溶和交换态镉含量;施用玉米和油菜秸秆黑炭均显著降低了模拟镉污染土壤中水溶和交换态镉含量;增加了松有机结合态、碳酸盐结合态和紧有机结合态镉含量;模拟镉污染土壤施用玉米和油菜秸秆黑炭6个月后土壤中水溶和交换态镉仍然是土壤镉的主要赋存形态,水溶和交换态镉占土壤全镉的70%以上。综合以上结果可知,秸秆黑炭不能降低污染土壤中镉的生物有效性和植物对土壤镉的吸收量。     

石灰与生物炭配施对不同浓度镉污染土壤修复

通过室内培养试验,研究生物炭与石灰不同用量配施对镉污染土壤pH和镉赋存形态的影响。结果表明,生物炭与石灰配施能够明显提高污染土壤pH,且随着施入量的增加pH提升效果显著。随着石灰和生物炭配施用量的增加,土壤交换态镉降低比例逐渐增大。培养60天后,镉污染浓度为5mg/kg的土壤交换态镉含量同对照处理相比依次减少36.80%,49.12%和57.38%;而土壤镉污染浓度为20mg/kg的土壤交换态镉含量较对照相比分别降低29.27%,31.68%和39.03%。2个浓度中土壤碳酸盐结合态镉、铁锰氧化物结合态镉和有机结合态镉均有所增加,残渣态镉虽有所增加,但在不同浓度之间存在差异。总体来看,本试验用量条件下,石灰和生物炭配施对污染浓度为5mg/kg的土壤镉钝化效果优于污染浓度为20mg/kg的土壤。     

巯基膨润土钝化修复镉污染水稻土的研究

通过田间种植水稻试验,探究了巯基膨润土（Bent-SH）对镉污染土壤的修复效果及钝化机理。结果表明:添加Bent-SH对土壤理化性质的影响很小,土壤有效态镉含量随Bent-SH添加量的增加逐渐降低,与对照相比,其最大下降率为48.57%。添加Bent-SH降低了土壤镉的迁移能力,降低了大米、秸秆对土壤镉的吸收,其最大下降率分别为72.73%、70.97%。土壤离子交换态镉（EX-Cd）含量最大下降率为54.17%,而铁锰氧化物结合态镉（FMO-Cd）和强有机质结合态镉（SO-Cd）含量最大增长率分别为117.40%和75.00%。Bent-SH添加量与土壤有效态镉、大米镉、秸秆镉含量呈极显著负相关,与土壤FMO-Cd、SO-Cd含量呈显著正相关,与土壤EX-Cd含量呈显著负相关。结果表明Bent-SH可以使土壤中的镉由EX向FMO和SO转化,有效降低镉的活性和生物可利用性,从而实现了镉污染土壤的钝化修复。     

秸秆还田对镉污染农田土壤中镉生物有效性的影响

通过温室盆栽试验和土壤培养试验,研究了重金属镉污染水稻土和人为模拟镉污染土壤上不同种类和不同量的作物秸秆还田后,土壤中可提取态镉的动态变化规律以及对白菜生长和吸收重金属镉的影响。结果表明,秸秆还田显著提高了2种镉污染土壤的pH值。镉污染水稻土上还田玉米和菜豆秸秆显著提高了土壤中醋酸铵提取态镉和DTPA提取态镉含量,秸秆还田后2周时醋酸铵提取态镉含量增加了17%~33%,随时间延长,土壤中可提取态镉增加变的不明显。模拟镉污染土壤上还田玉米和菜豆秸秆对土壤中醋酸铵提取态镉和DTPA提取态镉含量影响不明显。镉污染水稻土上秸秆还田量2%时显著降低了白菜体内镉含量,还田菜豆秸秆和玉米秸秆白菜体内镉含量分别降低了18%和27%。还田玉米秸秆影响了白菜生长,降低了白菜的产量;模拟镉污染土壤上还田菜豆秸秆对白菜生长和镉含量影响不明显,但还田2%玉米秸秆降低了白菜生物量,增加了白菜镉含量。     

不同有机肥对镉污染土壤镉形态及小麦抗性的影响

为了探讨有机肥钝化修复镉污染土壤对小麦生理抗性及小麦体内镉含量的响应,通过盆栽试验研究了不同有机肥对镉污染土壤Cd形态、小麦体内脯氨酸、丙二醛及小麦各部位镉含量的影响。结果表明:在镉污染土壤上施用有机肥后土壤可交换态Cd与碳酸盐结合态Cd含量有所下降,铁锰氧化物结合态Cd、有机结合态Cd和残留态Cd含量有所增加。施用羊粪、鸡粪的处理SH、CHSM、CMSL、CL。施用猪粪的处理PMPHPL。施用有机肥后小麦体内脯氨酸、丙二醛含量和小麦各部位Cd含量显著下降,施用羊粪、鸡粪的处理随施肥量的增加小麦体内脯氨酸、丙二醛含量和Cd含量明显降低,施用猪粪的PM处理的小麦脯氨酸、丙二醛含量和小麦根、茎、叶、籽粒中的Cd含量显著低于其他处理,其综合效果猪粪羊粪鸡粪。有机肥可通过改变污染土壤中的重金属形态而降低其生物有效性,可用于重金属污染土壤修复。     

不同惰性有机碳物料对土壤镉赋存形态和生物有效性的影响

通过温室盆栽试验和土壤培养试验,研究镉污染土壤和模拟镉污染土壤中加入草炭、活性碳和风化煤3种物料对土壤镉赋存形态和生物有效性的影响,探讨其作为重金属镉污染土壤修复剂的可行性。研究结果表明：3种有机碳物料均降低了土壤pH值,镉污染土壤加入不同惰性有机碳修复剂后,土壤中醋酸铵提取态Cd含量和DTPA提取态Cd含量变化不明显。在模拟Cd污染土壤上则不同,加入不同惰性有机碳修复剂后土壤中醋酸铵提取态Cd含量和DTPA提取态Cd含量均明显降低,降低幅度以风化煤最高,且随加入时间延长降低幅度增加。土壤中加入风化煤和草炭可显著增加土壤中轻组有机质含量,风化煤对土壤中镉有较强富集作用。两种土壤镉赋存形态均为酸提取态〉可还原态〉可氧化态,镉污染土壤加入有机物料后酸提取态镉含量无显著性变化,可还原态镉草炭和活性碳处理显著降低,草炭处理可氧化态镉也显著降低,模拟镉污染土壤加入有机物料后,酸提取态镉风化煤处理显著性降低,可还原态镉活性碳处理显著提高,可氧化态镉无显著性变化。在镉污染土壤上,3种有机碳物料对玉米生长没有显著影响,但增加了玉米体内镉含量;风化煤处理显著降低了白菜生物量,增加了白菜体内镉含量。模拟镉污染土壤上3种有机碳物料对白菜和玉米的生长和体内镉含量均没有显著影响。     

油枯对镉污染土壤的钝化研究

为了研究油枯对镉(Cd)污染土壤的钝化效果,以油枯为外源添加物(质量比:1%、2%、3%、4%、5%),模拟田间条件在塑料桶中进行为期45 d的培养,对镉污染土壤中Cd形态分布特征、DTPA提取态Cd(DTPA-Cd)含量、pH、有机质含量进行分析。结果表明,添加油枯可显著降低镉污染土壤中可交换态镉(Ex-Cd)的比例,提高碳酸盐结合态镉(Cb-Cd)、铁锰氧化物结合态镉(Fe-Mnb-Cd)以及有机质及硫化物晶格态镉(OMb-Cd)的比例,而残渣晶格结合态镉(RLb-Cd)变化不明显。添加油枯显著降低镉污染土壤中DTPA-Cd含量,降幅最高可达49%。镉污染土壤p H值维持在6.0左右,1%~4%添加处理中土壤pH波动幅度较大;而5%添加处理的土壤pH波动幅度小。添加油枯均能显著提高镉污染土壤中有机质含量。由此可见,油枯对镉污染土壤有较好的钝化效果,这为重金属污染土壤的修复和农业废弃物的循环利用提供了参考。     

油菜连作及施用堆肥对土壤镉赋存形态和生物有效性的影响

通过温室土培盆栽试验,研究了重金属镉污染土壤上连作油菜及施用堆肥对土壤中镉赋存形态及生物有效性的影响。结果表明：（1）在油菜连作体系下,施用堆肥显著降低油菜地上部镉含量。施用堆肥改变了土壤镉赋存形态,显著降低土壤易溶态和碳酸盐结合态镉含量而增加土壤铁锰氧化物结合态镉含量,从而降低土壤镉的生物有效性。（2）在相同堆肥处理下,种植两茬油菜后的土壤易溶态和碳酸盐结合态镉含量与不种植油菜的处理相比显著降低;而土壤硫化物及有机结合态镉含量较对照有所上升,种植油菜对土壤铁锰氧化物结合态镉和残渣态含量影响不显著,但是不同积累镉能力油菜朱苍花籽和川油Ⅱ-93之间对土壤镉形态的影响差异不显著。     

施肥对铅镉污染土壤上芥菜铅镉含量及生理的影响

盆栽试验研究了不同化学肥料组合处理对铅镉污染土壤上芥菜(Brassica juncea)Pb、Cd含量及其生理特性的影响。结果表明, 与对照相比, 各肥料处理在显著提高芥菜生物量的基础上, 显著降低了芥菜地上部Cd含量(P<0.05), 其中碳酸氢铵+磷酸二氢铵+硫酸钾处理的效果最佳, 芥菜Cd含量仅为对照的41.0%; 施肥处理提高了芥菜地上部Pb含量, 但Pb没有健康风险; 施肥提高了叶菜的叶绿素含量, 但丙二醛、脯氨酸、细胞质膜透性与芥菜地上部Pb、Cd含量无显著相关性。重金属污染土壤施肥处理是一种值得推广的降低叶菜有害重金属含量的有效技术。     

Effect of Clay Minerals on Immobilization of Heavy Metals and Microbial Activity in a Sewage Sludge-Contaminated Soil (8 pp)

Background   Aims, and Scope. Reducing heavy metal solubility and bioavailability in contaminated area without removing them from the soil is one of the common practices in decreasing the negative impacts on the environment and improving the soil quality. Therefore, our aim was to study the effect of clay minerals: Na-bentonite, Ca-bentonite, and zeolite applied to a contaminated soil on immobilization of heavy metals, as well as on some soil parameters related with microbial activity. Methods   A soil derived from sewage sludge was incubated with clay minerals of either Na-bentonite, Ca-bentonite, or zeolite for 111 days (d). During the incubation experiment, concentrations of water soluble Zn, Cd, Cu, and Ni were measured after extraction of 2 g air-dry soil with 50 ml of H2O for 2 h. After the water extraction, the soil sediment was extracted with 50 ml of 1 M NH4NO3 for 2 h to estimate the exchangeable amounts of heavy metals. Furthermore, soil microbial respiration, microbial biomass C, Corg mineralization, metabolic quotient (qCO2), and inorganic N were also investigated. Results and Discussion   Water extractable and exchangeable forms of heavy metals were changed by incubation and addition of clay minerals. Incubation of soil without addition of clay minerals (control) increased water extractable Cu by 12, 24 and 3.8% of initial content after 21, 62, and 111 d of incubation, respectively. The water extractable Zn decreased by 9% during 62 d of incubation and it tended to increase by 14% at the end of the incubation, as compared with the initial soil. Water extractable Cd decreased by 71, 66 and 33% of initial content, and Ni decreased by 54, 70, and 58%, after 21, 62, and 111 d of incubation, respectively. During the incubation experiment, the exchangeable form of all tested metals was decreased by incubation. The addition of clay minerals led to a significant decrease in water soluble and exchangeable forms of heavy metals during the incubation experiment, resulting in low metal extractability. The reduction in metal extractability was greater due to the addition of Na-bentonite or Ca-bentonite than that due to the addition of zeolite. During the first 3 weeks after addition of clay minerals, the studied biological parameters were not affected. However, as incubation progressed, the addition of Na- or Ca- bentonite led to a significant increase in soil respiration, microbial biomass C, Corg mineralization, and inorganic N; and a significant decrease in qCO2. This result is explained by sorption of heavy metals on Na-bentonite and Ca-bentonite and strong reduction of their toxicity. Conclusions   Our results clearly show that the addition of clay minerals, especially of Na-bentonite and Ca-bentonite, decreased the extractability of four metals during incubation. The decreased metal extractability was accompanied by an increase of soil respiration, Corg mineralization, microbial biomass C, and inorganic N and a decrease of metabolic quotient (qCO2), showing positive effect of clay mineral addition on soil biological parameters. Recommendations and Outlook   The use of Na-bentonite and Ca-bentonite is promising tool for reduction the extractability and possible toxicity of heavy metals in sewage sludge-contaminated soil. Therefore, the soils polluted with heavy metals may be ameliorated by addition of clay minerals, especially Na-bentonite and Ca-bentonite.     

Remediation of a soil contaminated with heavy metals by immobilizing compounds

The labile fraction of heavy metals (HM) in soils is the most important for toxicity for plants and microorganisms. Thus, it is crucial to reduce this fraction in contaminated soils to decrease the negative effect of HM. In a greenhouse experiment, the effects of several additives on the labile fractions of Zn, Cd, Cu, Ni, and Pb were investigated in a soil contaminated during long‐term sewage‐sludge application. The accumulation of HM was studied in the aboveground biomass of wheat (Triticum aestivum L.). The additives used were the clay minerals Na‐bentonite, Ca‐bentonite, and zeolite; the Fe oxides hematite and goethite; the phosphate fertilizers superphosphate and Novaphos. Wheat was planted three times during 5 months, allowed to grow for 7 w, and harvested. Dry matter and HM content of shoots were determined after each harvest. Soil samples were taken after the first and third harvest, and the NH₄NO₃‐extractable HM contents were determined. After the addition of 2% Na‐bentonite as well as 2% Ca‐bentonite, a strong reduction of the labile HM soil fraction and shoot HM concentration was observed. At the end of the experiment, the labile fraction was reduced due to the addition of Na‐bentonite and Ca‐bentonite by 24% and 31% for Zn, by 37% and 36% for Cd, by 41% and 43% for Cu, by 54% and 61% for Ni, and by 48% and 41% for Pb, respectively. Furthermore, the shoot HM concentrations with the exception of Zn were reduced below the phytotoxicity range. Accordingly, the shoot dry‐matter production was significantly increased. The addition of phosphate fertilizers (notably Novaphos) strongly reduced the bioavailability of Pb for wheat plants. By addition of 0.05% Novaphos, the labile fraction and the shoot concentration of Pb were lowered by 39% and 64%, respectively. However, the addition of Fe oxides and zeolite resulted only in a small reduction in HM bioavailability to wheat plants. Among the studied additives, Na‐bentonite and Ca‐bentonite have the most promising potential to reduce the bioavailability for the studied HM.     

重金属Cd Zn对长穗偃麦草生理生化特性的影响及其积累能力研究

以长穗偃麦草为材料,采用土培试验方法,研究了重金属Cd、Zn单一及复合污染对长穗偃麦草的生物量、保护酶（SOD和POD）、丙二醛（MDA）、脯氨酸（Pro）的影响,及长穗偃麦草对Cd、Zn的积累能力。结果表明,Cd、Zn单一及复合污染下,长穗偃麦草生物量随Cd和Zn浓度的升高而降低,与对照存在显著差异（P〈0.05）;Cd和Zn单一污染下,随着Cd、Zn浓度的升高,SOD、POD、MDA、Pro含量增加;Cd和Zn复合污染下,随处理质量浓度的增加,SOD呈下降趋势,POD和MDA呈增加趋势。Cd10Zn200处理下Pro含量减少,随Cd和Zn质量浓度的增加,其他复合处理下的Pro含量增加;植株根部的Cd和Zn积累量均大于地上部的积累量。综合实验结果,可初步判断长穗偃麦草能积累和忍受一定量的Cd、Zn,Cd和Zn复合污染对上述各指标的毒害效应大于同水平单元素污染的效应。长穗偃麦草根茎发达,生物量大,在生长过程中可通过生物量带走部分重金属Cd、Zn,因此长穗偃麦草具有修复重金属Cd和Zn污染土壤的潜能。     

生物炭与沸石复配对碱性土壤铅镉有效性的影响

【目的】以生物炭单施及其与沸石复配为钝化剂,研究其对铅镉复合污染碱性土壤理化性质及铅镉有效性的影响,以期用钝化技术为碱性土壤重金属污染原位修复提供理论和实践支持。【方法】以河南某金属冶炼厂附近铅(Pb)镉(Cd)污染的碱性菜地土壤(Pb 227.75 mg kg^-1、Cd 3.38 mg kg^-1)为研究对象,采用盆栽试验,研究生物炭单施及其与沸石复配(生物炭∶沸石=1∶1)不同施入量(0、1%、2.5%、5%)对土壤理化性质、土壤Pb、Cd有效态含量、青菜根和叶中Pb、Cd含量以及青菜富集转运Pb、Cd的影响。【结果】与对照相比,生物炭单施及其与沸石复配处理,使土壤pH提高了0.03～0.17个单位,与对照无显著差异,但显著提高了土壤有机质、碱解氮、有效磷和速效钾含量(P <0.05)。土壤有效态Pb、Cd含量随钝化剂施用量增加呈下降趋势,分别下降了10.69%～32.75%和7.63%～26.72%,相同施用量下复配处理效果优于单施处理。生物炭及其复配沸石促进了青菜生长,降低了青菜Pb的含量,根部和茎叶中Pb的含量比对照分别下降了2...     

土壤、蔬菜Cd污染相关性分析与土壤污染阈限值研究

为探求土壤重金属污染和蔬菜污染的相关性，为绿色蔬菜生产提供技术支持，该研究以郑州市常见的5种叶菜类蔬菜(油麦菜、荆芥、蕹菜、生菜、苋菜)为试验材料，采用温室盆栽土培试验方法研究了土壤不同浓度 Cd污染与蔬菜污染的相关性，并对绿色蔬菜生产要求的土壤污染阈限值进行了分析。研究结果表明：低浓度Cd污染的土壤对蔬菜生长、产量有促进作用；随着Cd浓度的增加，5种蔬菜中的Cd含量都呈现增加趋势。蔬菜中的Cd含量与土壤中的含量相关性较好；模拟得出土壤Cd阈限值为：油麦菜(0.3199±0.0349)mg/kg，荆芥(0.3335±0.01904)mg/kg，蕹菜(0.1952±0.1072)mg/kg，生菜(0.1554±0.0064)mg/kg，苋菜(0.2690±0.0532)mg/kg；对Cd富集能力由大到小排序为：生菜、蕹菜、苋菜、油麦菜、荆芥。     

6种固化剂对土壤Pb Cd Cu Zn的固化效果

通过在重金属污染土壤中分别施加沸石、石灰石、硅藻土、羟基磷灰石、膨润土和海泡石6种固化剂,研究了这6种固化剂对土壤中Pb、Cd、Cu、Zn的固化效果,筛选出几种效果较好的固化剂。实验结果表明：沸石、石灰石和羟基磷灰石均能够有效地降低土壤中交换态Pb、Cd的含量,并且明显减少了土壤中Pb、Cd的毒性浸出量,其中沸石最多降低土壤中交换态Pb、Cd含量分别达到48.7%和56.2%,减少土壤中Pb、Cd的毒性浸出量达到37.1%和30.1%;沸石、石灰石均能够有效降低土壤中交换态Cu的含量,降低量分别高达68.1%和85.2%,膨润土能有效减少土壤中Cu的毒性浸出量,减少量最高达到66.51%;石灰石对土壤中Zn有着良好的固化效果。     

我国稻田土壤镉污染现状及安全生产新措施

水稻是我国重要的粮食作物,由于受重金属污染威胁日益增大,其安全生产问题备受关注。通过综述我国稻田土壤及稻米镉污染现状、镉污染土壤改良剂研究进展以及稻米对镉富集的品种间差异,认为在土壤中镉的去除修复技术无法在短时间内实现的前提下,镉排异型水稻品种的筛选与利用是实现其安全生产的一个新的有效措施。在此基础上,配合一些污染土壤改良剂的使用,会进一步增强其安全生产水平。