Bioavailability of Heavy Metals in Sewage Sludge-Amended Thai Soils

Plough and subsoil layers of two majoragricultural soil series, Rangsit and Thonburi, foundin Bangkok area of Thailand were studied fordetermining the bioavailability and solubilitybehavior of heavy metals (Cd, Cu, Zn, Mn, and Fe)following application of sewage sludge from awastewater treatment plant and a series of laboratoryexperiments. The soils contained low indigenous heavymetals while the sludge contained higher amounts ofheavy metals but in an acceptable range forapplication as plant nutrient source in agriculturalsoil. Applications of sewage sludge increased pH ofthe acid soil and available plant nutrients to thesoils. The heavy metal concentration levels in thesoils also increased. Most partitioned into easilymobile pools and later into sparingly mobile poolsfollowing 12 weeks of incubation time. Bioavailabilityforms of Cd in soil solution were low but that of Cu,Zn, and Mn remained elevated even at 12 weeks of thereaction time. Applied inorganic Zn depressed Cdsorption capacity of two soils studied but it had noeffect on Cd desorption.     

污泥改良沙土中重金属及营养元素的迁移转化

为探究城市污水厂离心脱水污泥改良沙土对重金属及营养成分迁移转化的影响,利用掺混量为15%的污泥改良沙土作为0—20 cm土层土壤,通过饱和淋洗的方式分析了重金属及营养成分在土层中含量及形态转化,揭示了土层中重金属及营养成分迁移转化规律。结果表明:从重金属总量来看,试验淋洗10次后,土壤表层Cu,Pb,Zn,Cr滞留率较高,分别为78.57%,78.72%,86.35%,76.61%,Ni滞留率较低,为40.37%。但随着淋融次数的增加,重金属都存在一定淋失或向下层土壤迁移的风险;从重金属形态来看,各重金属Ni,Zn,Cr,Cu,Pb活性系数（MF）分别为1.657,0.531,0.265,0.113,0,由此可以得出,Ni,Zn在土壤环境中性质不稳定,Cr,Cu性质较为稳定,Pb最为稳定;改良沙土中氮磷营养元素在淋洗后含量下降,氮的流失率为39.36%,磷的流失率为18.67%,氮素较磷素易发生流失,下层沙土氮提升量高于磷。     

蚯蚓活动对城市生活污泥重金属的影响

采用塑料温棚内垄式堆积污泥培养蚯蚓方式,研究了蚯蚓处理对污泥重金属的影响。结果表明,污泥经蚯蚓处理后,理化性质发生了显著的变化,污泥的pH值、有机质、总氮和总磷都有不同程度的降低;蚯蚓能吸收富集污泥中的重金属,其中对重金属Cd有较强的富集能力;蚯蚓处理使污泥中重金属含量均出现不同程度的下降,重金属Cr、Zn、Pb、Cd、Cu、Ni分别减少27.98%、31.46%、32.81%、13.85%、23.86%和22.92%。利用盆栽试验,研究了污泥施用于土壤后生菜体内重金属积累的情况,结果表明,生菜体内重金属Zn、Cu、Pb和Ni的含量为污泥处理高于蚓粪处理;Cr和Cd则分别为差异不显著和略有降低。     

Behavior of heavy metals from sewage sludge in a Chernozem of the dry belt in Saxony‐Anhalt/Germany

In a small‐plot trial different doses of sewage sludge (equivalent 82‐330 tons of dry matter per hectare) were incorporated in 0—25 cm depth (1982—1985). The aim of the investigations was to study the fate of the heavy metals Zn, Cd, Cu, Ni, Pb, and Cr, to determine their concentration in different soil fractions using a sequential extraction method and to ascertain their uptake by Zea mays L. plants. Eleven years after the last application the metals supplied with the sludge had moved as far as 50 cm in depth. The concentrations of Zn, Cd, Cu, Ni, and Cr in the saturation extract of the sampled soil layers were closely correlated with the concentrations of dissolved organic carbon (DOC). This result suggests that the heavy metal displacement was partly connected with the DOC movement in the soil. Considerable amounts of Zn and Cd coming from sewage sludge were found in the mobile fractions of the soil. Cu, Ni, and Pb were located especially in organic particles, and Cr was obviously bound by Fe‐oxides. Nine years after the last application the binding species of heavy metals were still different compared with those in the untreated soil. The whole withdrawal of heavy metals by plants yielded <1 % of the applied amounts. In the case of Zn the uptake from the sludge amended soil decreased during the experimental period. No similar tendency was observed for the other elements. In any case their annual variations of uptake exceeded the effect of sludge application.     

Effect of solid-phase speciation on metal mobility and phytoavailability in sludge-amended soil

Sequential extraction was utilized for partitioning Cd, Cr, Ni, and Zn, in soil and sludge samples into five operationally-defined fractions: exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter and residual. The highest amounts of Cd, Ni, and Zn, expressed as per cent of the total, were found in the Fe-Mn oxide fraction of the sewage sludge. Chromium was significantly associated with the organic fraction of the sludge. The residue was the most abundant fraction for all metals studied in the untreated soil, and for Cd and Ni in the sludge-treated soil. The concentration of exchangeable Cd and Cr was relatively low in the untreated soil and did not change much after sludge application, whereas the concentrations of exchangeable Zn increased about 50 times and the concentrations of exchangeable Ni doubled in the sludge-treated soil. The lysimetric experiment revealed an increase in Zn and Ni uptake by ryegrass and in the percentage of metals leached from the soil profile after massive sludge application. In contrast only negligible changes were observed for Cd and Cr. The assumption that mobility and biological availability are related to metal speciation was confirmed by the agreement between the distribution pattern of Cd, Cr, Ni and Zn in the soils, the uptake of the metals by plants and their capacity for leaching out from the soils.     

肥料重金属含量状况及施肥对土壤和作物重金属富集的影响

本文对肥料中重金属的含量状况以及施肥对土壤和农作物重金属累积影响的研究进展进行了系统分析和总结。过磷酸钙中锌（Zn）、 铜（Cu）、 镉（Cd）、 铅（Pb）含量高于氮肥、 钾肥和三元复合肥,有机-无机复混肥料中的Pb含量高于其他化肥。有机肥如畜禽粪便、 污泥及其堆肥中的重金属含量高于化肥,猪粪中的Cu、 Zn、 砷（As）、 Cd含量明显高于其他有机废弃物,鸡粪中铬（Cr）含量高;污泥和垃圾堆肥中Pb或汞（Hg）含量高。商品有机肥Zn、 Pb和镍（Ni）含量高于堆肥,Hg含量高于畜禽粪便。多数研究表明,氮磷钾配施与不施肥相比土壤Cd和Pb含量增加,施用有机肥比不施肥提高土壤Cu、 Zn、 Pb、 Cd含量。施用化肥对农作物重金属富集的影响不明确,而施用有机肥可提高作物可食部位Cu、 Zn、 Cd、 Pb 的含量,影响大小与有机肥种类、 用量、 土壤类型和pH以及作物种类等有很大关系。在今后的研究中应着重以下几个方面, 1）典型种植体系下土壤重金属的投入/产出平衡; 2）不同种植体系下长期不同施肥措施对土壤重金属含量、 有效性影响的动态趋势; 3）典型种植体系和施肥措施下土壤对重金属的最高承载年限; 4）现有施肥措施下肥料中重金属的最高限量标准。     

Comparative availability to wheat of metals from sewage sludge and inorganic salts

A greenhouse experiment was conducted to evaluate the availability of metals from sewage sludge and inorganic salts, and the effect of pH and soil type on yield and metal (Zn, Cu, Cd and Ni) uptake by wheat (Triticum aestivum L. var. ‘holly’). Soils used in this study were Hartsells sandy loam (fine-loamy, siliceous Thermic Typic Hapludult) and Decatur silty clay loam (Clayey, kaolinitic, Thermic Rhodic Paleudult). Two treatments of sewage sludge containing metals were applied at the rate of 20 and 100 mt ha^?1. Inorganic Salts of Zn, Cu, Cd, and Ni were applied (as sulfate salts) at concentrations equivalent to those found in the 20 and 100 mt ha^?1 sludge. One treatment consisted of inorganic metals plus sewage at the 20 Mg ha^?1 rate. Two soil pH levels, one at field pH (below 6.0) and another pH adjusted between 6.5 and 7.0 were used. Wheat plants were harvested four weeks after germination. Two more subsequent harvests were made at four week intervals. For each harvest, dry matter yield increased as the rate of sludge application increased for both soil types. The soil pH also influenced the dry matter yield. High yield was observed when the pH was adjusted between 6.5 to 7.0 for both soils. An increase in yield was also observed at each subsequent harvest for most of the treatments. Inorganic salt treatments produced lower dry matter yields when compared with the sludge. Both sludge application and metal salts increased plant tissue concentration of Zn, Cu, Cd, and Ni at field pH for both soils. However, increasing the pH of the soil for both sludge and inorganic salt treatments generally decreased the tissue concentration of the above metals.     

Heavy‐Metal Contamination of Soil and Vegetables in Wastewater‐Irrigated Agricultural Soil in a Suburban Area of Hanoi,Vietnam

The To Lich and Kim Nguu Rivers, laden with untreated waste from industrial sources, serve as sources of water for irrigating vegetable farms. The purposes of this study were to identify the impact of wastewater irrigation on the level of heavy metals in the soils and vegetables and to predict their potential mobility and bioavailability. Soil samples were collected from different distances from the canal. The average concentrations of the heavy metals in the soil were in the order zinc (Zn; 204 mg kg^?1) > copper (Cu; 196 mg kg^?1) > chromium (Cr; 175 mg kg^?1) > lead (Pb; 131 mg kg^?1) > nickel (Ni; 60 mg kg^?1) > cadmium (Cd; 4 mg kg^?1). The concentrations of all heavy metals in the study site were much greater than the background level in that area and exceeded the permissible levels of the Vietnamese standards for Cd, Cu, and Pb. The concentrations of Zn, Ni, and Pb in the surface soil decreased with distance from the canal. The results of selective sequential extraction indicated that dominant fractions were oxide, organic, and residual for Ni, Pb, and Zn; organic and oxide for Cr; oxide for Cd; and organic for Cu. Leaching tests for water and acid indicated that the ratio of leached metal concentration to total metal concentration in the soil decreased in the order of Cd > Ni > Cr > Pb > Cu > Zn and in the order of Cd > Ni > Cr > Zn > Cu > Pb for the ethylenediaminetetraaceitc acid (EDTA) treatment. The EDTA treatment gave greater leachability than other treatments for most metal types. By leaching with water and acid, all heavy metals were fully released from the exchangeable fraction, and some heavy metals were fully released from carbonate and oxide fractions. The concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in the vegetables exceeded the Vietnamese standards. The transfer coefficients for the metals were in the order of Zn > Ni > Cu > Cd = Cr > Pb.     

长期化肥配施不同有机肥对土壤和玉米中重金属累积的影响

  【目的】  明确长期化肥配施有机肥对重金属元素在土壤和农作物籽粒、秸秆中积累的影响及其环境效应，为安全高效施肥提供科学依据。  【方法】  在北京市农林科学院新型肥料长期定位试验站进行了为期10年的田间试验，其种植模式为冬小麦–夏玉米轮作，试验处理为不施肥 (CK)、单施化肥 (NPK)、氮磷钾 + 鸡粪堆肥的有机肥料 (NPKJF)、氮磷钾 + 污泥堆肥的有机肥料 (NPKWN)、氮磷钾 + 垃圾堆肥的有机肥料 (NPKLJ) 和氮磷钾 + 秸秆粉碎还田 (NPKJG) 共6个处理，施肥处理依据等氮量施肥原则，每季作物施 N 180 kg/hm2、P₂O₅ 90.0 kg/hm2、K₂O 90.0 kg/hm2。在玉米收获后测定了玉米秸秆、籽粒和0—20 cm耕层土壤中重金属全量。  【结果】  添加污泥处理显著提高了土壤中Cd、Hg、As、Cu、Zn的含量，单因子污染指数分别比对照提高了45.10%、150.00%、104.00%、44.60%、65.80%。不同施肥处理对土壤中全量Cd、Cr、Hg、Cu、Zn存在一定的富集效果。各处理重金属单项污染指数在0.02～0.46，远小于1，综合污染指数为0.23～0.36，均小于0.7，试验区土壤重金属均为无污染等级。施用有机废弃物堆肥的处理玉米籽粒Cd、Cu、Zn含量比对照显著增加，各处理间Hg、As、Cr、Pb、Ni含量差异不显著，连续10年定位施肥后试验站土壤以及玉米籽粒中重金属含量均未超标。同一作物不同部位对重金属的富集能力不同，玉米秸秆对重金属的富集能力大于籽粒。玉米籽粒中Pb、Cu、Zn含量与土壤Pb、Cu、Zn含量存在正相关性，玉米秸秆中Cd、Hg、Cr、Ni含量与土壤中Cd、Hg、Cr、Ni含量呈正相关或者显著负相关。  【结论】  在施氮总量不变的前提下，连续施用供试有机堆肥10年后，土壤重金属含量均未超标，土壤重金属单项污染指数在0.02～0.46，综合污染指数为0.23～0.36，无污染风险。只有污泥堆肥需要加强土壤Cd的监测。玉米秸秆对重金属的富集能力大于籽粒。玉米籽粒中Pb、Cu、Zn含量与土壤相应重金属含量存在正相关性，秸秆中Cd、Pb、Hg、Zn与Cr、Ni含量与土壤中相应重金属含量呈正相关，而秸秆中Cr、Ni含量与土壤中相应重金属含量呈负相关。     

Application of composted sewage sludges contaminated with heavy metals to an agricultural soil

To elucidate the mechanism of transfer of heavy metals into the food chain, an experiment was carried out with a calcareous soil, to which two different doses of a sewage sludge compost contaminated with either Cd or Zn, Cd, Cu, and Ni were applied. A crop of lettuce was then grown in the amended soils. The application of sewage sludge composts to a calcareous soil lowered the soil's pH, although the value was always around 8 at the end of the experiment. Electric conductivity rose with organic amendment. As anticipated, such an amendment improved the nutritional level of the soils, particularly Nand P, both total and available. Plant yields were negatively affected by organic amendments contaminated with heavy metals, the most dangerous in our experiment being Cd and Zn since this metals easily taken up by plants. As Ni and Cu form insoluble complexes with the organic matter of the sewage sludge composts they are not readily absorbed. Of the metals studied, Cd and Zn showed the highest bioavailability index.     

包头市铜厂周边土壤中重金属垂直分布特征与形态分析

为了解包头市铜厂周边地区土壤剖面中重金属污染状况,采用火焰原子吸收分光光度法和Tessier连续提取法,对土壤中6种重金属（Cu,Zn,Mn,Ni,Pb和Cd）的垂直分布特征、形态及潜在生物可利用性进行了分析。结果表明:研究区土壤剖面各层土壤中6种重金属含量均超过内蒙古土壤背景值,Cu,Pb和Cd为主要污染物。随采样深度的增加,Cu,Zn,Pb和Mn的含量呈现下降趋势,且由相关性系数可知重金属Cu,Zn和Pb可能有相同人为或自然污染源;土壤剖面中6种重金属均主要以残渣态存在,含量均在50%以上,对生物危害较小;潜在生物可利用性分析结果为:Cu（32.61%） > Mn（31.85%） > Ni（24.90%） > Zn（16.60%） > Cd（15.23%） > Pb（14.87%）,Cu和Mn的潜在生物可利用性较大,其次为Ni,Zn,Cd和Pb潜在生物可利用性较小。     

Response of the sorption behavior of Cu,Cd, and Zn to different soil management

This study investigated the effect of different farming practices over long time periods on the sorption‐desorption behavior of Cu, Cd, and Zn in soils. Various amendments in a long‐term field experiment over 44 y altered the chemical and physical properties of the soil. Adsorption isotherms obtained from batch sorption experiments with Cu, Cd, and Zn were well described by Freundlich equations for adsorption and desorption. The data showed that Cu was adsorbed in high amounts, followed by Zn and Cd. In most treatments, Cd ions were more weakly sorbed than Cu or Zn. Generally, adsorption coefficients K_F increased among the investigated farming practices in the following order: sewage sludge ≤ fallow < inorganic fertilizer without N ≈ green manure < peat < Ca(NO₃)₂ < animal manure ≤ grassland/extensive pasture. The impact of different soil management on the sorption properties of agricultural soils for trace metals was quantified. Results demonstrated that the soil pH was the main factor controlling the behavior of heavy metals in soil altered through management. Furthermore, the constants K_F and n of isotherms obtained from the experiments significantly correlated with the amount of solid and water‐soluble organic carbon (WSOC) in the soils. Higher soil pH and higher contents of soil organic carbon led to higher adsorption. Carboxyl and carbonyl groups as well as WSOC significantly influenced the sorption behavior of heavy metals in soils with similar mineral soil constituents.     

Assessment of the interactions of metals and nitrilotriacetic acid in soil/sludge mixtures

The solution phase forms of Cu, Mn, Ni, and Zn in digested sewage sludge and a soil/sludge mixture were investigated. Gel filtration chromatographic analysis indicated that Cu and possibly Ni were maintained in solution by association with a soluble, high molecular weight organic fraction; Mn solubility was due to the presence of unbound inorganic species and soluble Zn was distributed equally between the two forms. Speciation of the metals in the solution phase of the soil/sludge mixture generally reflected that of the sludge. However, the total amount of soluble Mn in the soil/sludge mixture was approximately 25 times greater than in the sludge and was attributed to heavy metal induced release of indigenous soil Mn. Increases in the quantities of soluble Ni and Zn in both the sludge and the soil/sludge mixture following equilibration with 40 mg L^?1 NTA were due to conversion of solid phase forms to soluble metal-NTA complexes. The preferential complexation of NTA with Cu already present in soluble organic forms resulted in a change in speciation without a corresponding increase in solubility. The importance of changes in speciation with regard to potential metal mobility and bioavailability within sludge-amended soil is discussed.     

GLDA淋洗参数对污泥中重金属去除效率的影响及其动力学分析

采用GLDA作为淋洗剂对工业污水污泥进行淋洗,确定淋洗的最优参数,为治理工业污泥提供参考依据。通过振荡淋洗研究了GLDA浓度（0.5% ~ 20%）、pH（2 ~ 10）、液固比（10∶1 ~ 80∶1）和淋洗时间（0 ~ 24 h）对污泥中重金属去除率的影响,利用动力学方程对实验数据进行拟合。结果表明,降低pH、增加液固比和延长淋洗时间均可提升重金属的淋洗效率,在pH为2,浓度5%,液固比60∶1,淋洗时间480 min时,GLDA对污泥中的重金属淋洗率达到最优,镍（Zn）、镍（Ni）、镉（Cd）和铬（Cr）的去除率分别为91.21%、76.34%、69.56%和65.01%。准二级动力学方程可以较好的拟合GLDA对4种重金属的淋洗过程,说明重金属淋洗过程以化学淋洗为主。综上所述,在进行淋洗参数优化的基础上,GLDA可用于工业污水污泥中重金属的去除。     

Comparison of routine soil tests and EPA method 3050 as extractants for heavy metals in Delaware soils

Abstract

Agricultural use of sewage sludges can be limited by heavy metal accumulations in soils and crops. Information on background levels of total heavy metals in soils and changes in soil metal content due to sludge application are; therefore, critical aspects of long‐term sludge monitoring programs. As soil testing laboratories routinely, and rapidly, determine, in a wide variety of agricultural soils, the levels of some heavy metals and soil properties related to plant availability of these metals (e.g. Cu, Fe, Mn, Zn, pH, organic matter, texture), these labs could participate actively in the development and monitoring of environmentally sound sludge application programs. Consequently, the objective of this study was to compare three soil tests (Mehlich 1, Mehlich 3, and DTP A) and an USEPA approved method for measuring heavy metals in soils (EPA Method 3050), as extractants for Cd, Cu, Ni, Pb and Zn in representative agricultural soils of Delaware and in soils from five sites involved in a state‐monitored sludge application program.

Soil tests extracted less than 30% of total (EPA 3050) metals from most soils, with average percentages of total metal extracted (across all soils and metals) of 15%, 32%, and 11% for the Mehlich 1, Mehlich 3, and DTPA, respectively. Statistically significant correlations between total and soil test extractable metal content were obtained with all extractants for Cu, Pb, and Zn, but not Cd and Ni. The Mehlich 1 soil test was best correlated with total Cu and Zn (r=0.78***, 0.60***, respectively), while the chelate‐based extractants (DTPA and Mehlich 3) were better correlated with total Pb (r=0.85***, 0.63***). Multiple regression equations for the prediction of total Cu, Ni, Pb, and Zn, from soil test extractable metal in combination with easily measured soil properties (pH, organic matter by loss on ignition, soil volume weight) had R² values ranging from 0.41*** to 0.85***, suggesting that it may be possible to monitor, with reasonable success, heavy metal accumulations in soils using the results of a routine soil test.     

污泥与施污土壤重金属生物活性及生态风险评价

将城市污泥以不同质量比施于土壤中构成污泥混合土壤,研究各污泥配比土壤中重金属的生物活性,并采用三种重金属评价方法(地累积指数法、潜在生态风险指数法、综合毒性指数模型)和黑麦草对重金属的吸收富集效果来对施污土壤中重金属具有的生态风险性进行评价。结果表明:污泥的添加使土壤中生物活性态Cd、Cu和Zn含量显著增加,对三种重金属具有活化作用,但对Pb却起到钝化作用。生态风险评价结果表明:污泥的添加使土壤中Pb呈现无污染和低生态风险;Cu和Zn呈现中度污染和低生态风险;Cd达到强度污染和重度生态风险,重金属潜在生态风险(RI)总体处于强度生态风险水平。当污泥添加比例大于6:10(污泥S3处理)时,施污土壤中重金属的综合毒性指数高于土壤对照。黑麦草对Cd、Pb、Cu和Zn的富集浓度与施污土壤中对应重金属的生物活性态含量存在显著正幂指数关系,同时黑麦草对施污土壤中Cd、Cu和Pb的富集能力大小与地累积指数法和潜在生态风险指数法对三种重金属具有的生态风险性的评价结果具有一致性。     

太原市污灌区土壤重金属污染现状评价

对太原市污灌区土壤重金属分布特征进行了分析评价,结果表明重金属Pb、Zn、Cu、Ni、Mn、Cr、As、Hg、Cd含量均值均未超过土壤环境质量标准（GB15618—1995）,但其平均值均显著高于太原市土壤背景值。各重金属间的相关分析表明,Pb、Zn、Cu、Ni、Mn、Cr、As、Cd之间呈极显著相关,说明这8种元素污染源可能相同。Hg是本区表层土壤重金属污染的主要因子,重金属元素的污染程度依次为Hg〉Cd〉Pb〉As〉Cu〉Zn〉Cr〉Mn〉Ni。土壤重金属单项污染指数均值均大于1,综合污染指数为2.81,总体上,污染水平为中度及其以上。各种重金属单因子污染指数和综合指数在研究区有相似的空间分布格局,总体分布趋势为东南部小店地区和中南部晋源区相对较高,南部清徐县相对较小;通过因子分析并结合污灌区污染源调查,表明Hg除受污水灌溉的影响外,燃煤释放的Hg可能是重要来源之一,Cd、Zn、Pb和Cu可能来自污水灌溉和大气沉降,以污水灌溉的贡献为主,Ni、Mn、As、Cr来自污水灌溉。Hg、Cd是太原市污灌区土壤中需要优先控制的重金属。     

酸雨地区蔬菜对重金属的吸收及重金属健康风险基准的估算

通过盆栽实验,以小白菜(上海青)、大白菜和萝卜为指示作物,研究了酸雨作用下Cu,Zn,Pb,Cd,Cr和Ni复合污染物在土壤-作物系统中的吸收与富集情况。结果表明,酸雨-重金属复合污染处理使Cu,Pb,Cr和Ni在蔬菜中积累量明显高于对照处理;Zn和Cd一般只有在复合污染处理中外源Zn或Cd含量较高时才明显高于对照处理。与对照相比,酸雨-重金属复合污染处理使Pb和Ni的富集系数增大,Cu的富集系数多数情况下增大,Cd的富集系数多数情况下减小,Zn和Cr富集系数的变化在不同蔬菜之间存在较明显的差异;重金属在不同蔬菜中的富集系数一般表现为萝卜>上海青>大白菜,蔬菜中不同重金属富集系数一般表现为Zn>Cd>Ni>Cu>Pb>Cr。酸雨-重金属复合污染条件下蔬菜中重金属积累量与其在土壤中总量之间的相关性均达到显著或极显著水平。以大宗蔬菜上海青、大白菜和萝卜为指示作物对酸雨地区蔬菜地中重金属的健康风险基准进行了估算,这对开展酸雨地区土壤重金属环境容量评价、重金属污染修复目标及地方性土壤环境质量标准的制订提供了参考依据。     

Leaching Behavior of Heavy Metals In Biosolids Amended Sandy Soils

Use of biosolids in agriculture to improve crop production and soil quality have created concerns due to content of heavy metals that may affect surface or ground water quality. A column leaching study was conducted to evaluate the leaching potential of copper (Cu), lead (Pb), zinc (Zn), cdmium (Cd), cobalt (Co), chromium (Cr), and nickel (Ni) from two typical agricultural sandy soils in South Florida (Spodosol and Alfisol) with increasing application of pelletized biosolids (called PB) at the rates of 0, 1.25, 5.0, 10.0 g kg^?1, respectively together with chemical fertilizer (CF). Elevated PB rate resulted in reduced leaching loss of Cu, Pb, Zn, Cd, Co, Ni from Spodosol, but resulted in increased loss of Pb, Zn, Cd, and Co from Alfisol. Significant reduction in Cu loss occurred in both soils, which can be attributed to the strong binding of Cu with organic matter from the applied PB. Percentage of Cd loss as of total Cd was 13% – 41%, the highest in all the heavy metals, whereas loss of Pb as of total Pb was less than 6.6%, though the concentrations of Pb, Cd, Co, and Ni in leachate were mostly above the limits of U.S. EPA drinking water standards or the national secondary drinking water standards. These results indicate that soil properties, PB application rates, and chemical behavior of elements jointly influence the leachate total loads of heavy metals in sandy soils applied with biosolids. Application of CF together with BP at a rate higher than 10.0 g kg^?1 for sandy soils may pose potential threats to water quality due to enhanced leachate loads of Cr and Ni in Spodosol and Pb, Zn, Cd, Co and Ni in Alfisol.     

石灰水对混合试剂洗脱土壤重金属淋洗效果的影响

为了探索石灰水对混合试剂(MC)洗脱后土壤中重金属的淋洗效果,对重金属污染土壤进行了盆栽淋洗试验研究。结果表明:石灰水淋洗MC洗脱土壤,淋出液中Cd、Zn、Pb和Cu浓度均显著高于去离子水淋洗MC洗脱土壤,这主要由于石灰水提高土壤pH,释放土壤所吸附的络合态重金属,这种现象在酸性污染土壤中表现更明显。对于酸性污染土壤,可采用MC+石灰水+去离子水依次进行淋洗处理,其Cd和Zn去除率与MC+去离子水+去离子水依次淋洗处理相比提高22.6%和28.8%;对于中性重金属污染土壤,两处理间重金属去除率差异不显著。石灰水淋洗可提高土壤重金属去除率,并提高土壤pH,改善MC洗脱对土壤的酸化,有利于淋洗后土壤的农业利用。