含磷物质对铅耐性与敏感性植物生长及磷铅吸收的影响

将耐性植物芥蓝（Brassicacapitata）与敏感植物小白菜（Brassica chinenzis）暴露于含Pb的营养液中,通过添加磷灰石矿尾料（PR）、重过磷酸钙（TSP）及二者混合物（P＋T）处理,研究含磷物质对两种植物吸收Ph的影响以及Pb在植物根表面形态变化过程。结果显示：添加含磷物质降低了耐性植物芥蓝根部Pb的含量,但对地上部Ph吸收的影响不显著;对敏感植物小白菜来说,PR和P＋T处理的植物根部及地上部Pb的含量与对照基本一致,而TSP处理促进了Pb的吸收,表现出小白菜根部及地上部Pb的含量显著高于对照组。含磷物质添加诱导了Pb在植物根表面形成Pb5（PO4）3Cl、Pb5（PO4）3OH的沉淀,但这并没有直接导致两种植物对Pb吸收量的减少。     

大型铜冶炼厂周边农田区大气重金属沉降特征研究

为探索铜冶炼厂周边农田区大气重金属沉降的时空变异特征,以冶炼厂为中心,四周等距离均匀分设8个监测点,于2012年5月至2013年4月,根据酸沉降检测技术规范,采收大气干湿沉降混合样品,利用原子吸收分光光度法分析样品中cu、cd、Pb、zn、cr含量,计算各监测点所代表区域各类重金属沉降通量。结果显示,研究区重金属cu、cd、Pb、zn、cr的年沉降通量分别为638、6．56、70．0、225、22．7mg·m^-1·a^-1。五种重金属沉降量具有一定的时间变化特征,其中cd、zn和cr的月际间变化显著（P〈O．05,n=96）,Pb、zn、cr季节间变化显著（P〈O．05,n=32）,而cu无显著的月间或季间变化。空间上,cu、cd、Pb年沉降通量有极显著性差异（P〈0．Ol,n=8）,以铜冶炼厂西南方向的九牛岗监测点最高,而zn和cr则无显著性差异。     

生物炭/石灰混施对重金属复合污染土壤的稳定化效应

采用室内模拟实验,以南方砷镉铅复合污染的酸性红壤为对象,利用化学钝化原理,探讨钝化材料对重金属稳定化的技术效果及应用配方,以期为砷镉铅复合污染红壤修复与安全利用提供依据。具体做法为：选择生物炭（BC）和石灰（SH）为钝化材料,以土壤重量的1%、4%为材料添加量,单一或混合施用于砷镉铅复合污染土壤,并于恒温（25℃）条件下培养60d,在实验进行至第1天、第30天、第60天时取样,测定红壤酸碱度（pH）和水溶态（Water soluble）有效砷（As）、镉（Cd）、铅（Pb）即WSAs、WSCd、WSPb含量,以及土壤重金属As、Cd、Pb结合态含量与占比的变化,明确生物炭石灰单/混施对重金属的稳定化效应。结果表明：生物炭/石灰无论单施或混施均能不同程度地降低土壤中水溶态WSCd和WSPb含量,钝化效率分别为33.51%～78.89%和9.05%～96.24%。而材料单施（1BC、4SH）和两者混施高用量（4BC4SH）处理,均能大幅降低土壤中有效As含量,钝化效率为10.25%～55.27%,其中以两者混施高用量（4BC4SH）处理对土壤重金属As、Cd、Pb协同钝化的效果最佳,当培养实验进行至第60天时,钝化效率依次达55.27%、76.39%和96.24%。培养后土壤中As形态由易被植物吸收的非专性吸附态、专性吸附态转化为稳定的残渣态,土壤中Cd和Pb则由活性最强的酸可提取态转化为残渣态,土壤中As、Cd、Pb的稳定化效应明显,迁移系数下降;此外,生物炭/石灰的单施及混合施用,均可导致土壤酸碱度（pH）显著提升（P<0.05）,有利于南方酸化土壤的改良。总体而言,本研究中生物炭/石灰两者混施高用量水平下（4BC4SH）土壤重金属的钝化效果最优,可实现对As、Cd和Pb复合污染红壤的稳定化修复。     

鸡粪生物炭表征及其对水和土壤镉铅的修复效果

采用缺氧控温法,在200、400、600和800℃条件下制备鸡粪生物炭(BC200、BC400、BC600和BC800),利用比表面积及孔径分析仪(BETacceleratedsurfaceareaandporosimetrysystem)、扫描电镜(scanningelectron microscopy)、透射电镜(transmission electron microscope)、傅里叶红外光谱仪(Fourier transform infrared spectroscopy)等对其理化性质和结构特征进行表征,并研究了鸡粪不同温度处理下生物炭对水体和土壤中Cd、Pb污染修复效果。结果表明,鸡粪生物炭灰分含量、pH值、BET比表面积及孔径随热解温度的升高而增加,表面出现大量无规则的孔隙结构,且以介孔为主,而生物炭产率则随温度升高而显著降低(P0.05)。鸡粪生物炭对Cd2+、Pb2+的吸附分为快速吸附和慢吸附2个阶段,Elovich模型能更好地模拟Pb2+、Cd2+的动力学过程,平衡时最大吸附量分别达到52.02 mg/g (BC600)和242.59 mg/g (BC800)。添加鸡粪生物炭显著提高了土壤pH值(P0.05),而TCLP提取态Pb、Cd含量降低,最大较对照分别降低16.5%和14.5%。与对照相比,鸡粪生物炭不同程度上降低了Pb、Cd弱酸提取态、可还原态以及可氧化态比例,其残渣态比例则分别增加了5.49%～15.14%和2.51%～6.30%。综上所述,鸡粪生物炭对重金属Pb、Cd具有较强的钝化效果。     

杂交狼尾草对土壤锌／十溴联苯醚复合污染的生理响应及修复

采用室内盆栽试验,研究了杂交狼尾草对土壤中Zn／十溴联苯醚（BDE-209）污染的生理响应及修复效果。结果表明,杂交狼尾草的生物量随着BDE-209浓度增大而升高,低中浓度Zn／BDE-209复合污染明显促进了植株生长;在单-BDE-209和复合两种污染条件下,随着污染物浓度上升,丙二醛（MDA）含量上升,可溶性蛋白质含量、超氧化物歧化酶（SOD）活性均呈下降趋势;植物地下部分对zn和BDE-209的积累均大于地上部分,随着BDE-209浓度增大,植物对zn和BDE-209积累量上升,低中浓度Zn／BDE-209复合污染对积累、转运zn和BDE-209均有促进作用,植物地下部分对zn的富集系数高达7．78;杂交狼尾草对复合污染土壤中BDE-209去除率高达60．73％,不同去除效果为根际去除率〉非根际去除率〉无植物去除率。     

用于表征三七种植区土壤中可利用态砷的化学提取剂的筛选

为正确表征云南文山三七种植区土壤中植物可利用态砷,选取NaH2PO4（0.5mol·L-1）、H2O、H3PO4（0.2mol·L-1）、EDTA（0.0625mol·L-1,pH=7）、NH4C（l1.0mol·L-1）和（NH4）2SO（40.05mol·L-1）6种提取剂,比较了它们对土壤中砷的提取效果,及其所提取的砷与三七植株各部位砷含量之间的相关关系。结果表明,NaH2PO4、H3PO4和（NH4）2SO4这3种提取态砷与土壤总砷呈极显著正相关,相关系数分别为0.8359、0.8177和0.8810。NaH2PO4和H3PO4的提取效率较高,平均提取效率分别为6%和11%;而（NH4）2SO4提取效率较低,平均仅为0.084%。NaH2PO4和（NH4）2SO4提取态砷与三七主根、须根和茎部砷含量呈显著正相关,H3PO4提取态砷与三七主根和须根砷含量呈显著正相关。综合考虑认为NaH2PO（40.5mol·L-1）是最佳提取剂,H3PO（40.2mol·L-1）提取剂次之,这两种提取剂均可较好地表征土壤中砷的三七可利用性。     

不同内源重金属生物炭对Cu和Cd吸附及其对老化作用的响应

为明确老化作用对不同内源污染物生物炭吸附重金属稳定性的影响，该研究以不同污染程度（清洁、中度和重度污染）土壤种植的巨菌草秸秆制备3种不同内源Cu和Cd含量的生物炭RB、SB和JB，分析3种生物炭对Cu和Cd的吸附能力以及干湿和冻融老化对饱和吸附后生物炭中Cu和Cd的生物有效性的影响。结果表明：3种生物炭表面均分布丰富的孔隙结构，RB含有最高的pH值和灰分；生物炭对Cu和Cd的吸附符合Langmuir模型（R2=0.951～0.998），且RB对Cu和Cd的吸附量最大，分别为54.3和37.3 mg/g；与此相同，饱和吸附后RB对Cu和Cd的固持量最大，分别为21.4和4.78 mg/g。与老化前相比，干湿老化较冻融老化更显著地降低了饱和吸附后生物炭中Cu的TCLP浸出含量，促进了Cu从酸溶态和残渣态向还原态和氧化态转化，降低了Cu的环境风险；但是干湿和冻融老化作用增加了饱和吸附后生物炭中Cd的TCLP浸出含量，促进了Cd从残渣态向酸溶态、还原态和氧化态转化，增加了Cd的环境风险。这可能是由于3种生物炭对Cu的吸附主要以表面络合为主，对Cd的吸附以化学沉淀机制为主。总体上，RB生物炭固持最高的Cu和Cd，但是干湿和冻融老化增加了饱和吸附后生物炭Cd环境风险，研究结果对于评估生物炭长期钝化修复稳定性具有一定的指导意义。     

有机物料及其用量对生菜生长与Pb含量的影响

为了降低叶菜中重金属Pb的含量,选择有机肥、猪粪、牛粪、鸡粪和花生麸5种有机物料为材料,分别以0.5%、1%、2%、4%4个水平的用量施入重金属污染土壤,通过种植3茬生菜（Lactuca sativa L.）的盆栽试验研究有机物料对重金属污染土壤上生菜生长及其Pb含量的影响。结果表明,与对照相比,有机物料利于生菜生长,有提高生菜生物量的趋势;大部分有机物料处理没有显著影响生菜地上部分的Pb含量;5种有机物料中,仅牛粪有提高生菜地上部Pb含量的趋势;生菜Pb含量平均值高低的顺序为牛粪〉鸡粪〉花生麸〉有机肥〉猪粪,但不同有机物料之间没有显著差异。与对照相比,大部分处理没有显著影响土壤的DTPA-Pb含量,初步揭示了供试有机物料没有显著影响生菜地上部Pb含量的原因。     

铅镉高污染土壤的钝化材料筛选及其修复效果初探

本研究以重金属高污染农田土壤(全Pb含量为1 277 mg/kg,全Cd含量为39.0 mg/kg)为研究对象,通过土培试验和玉米苗期盆栽试验,探讨海泡石、石灰、腐植酸、钙镁磷肥、磷矿粉、生物质炭等常用稳定材料不同剂量及复配组合对高污染土壤重金属的钝化修复效应。土培试验结果表明,石灰对Pb和Cd钝化效果最好,其次是海泡石,但两者表现为较高添加量处理间没有显著差异;而低剂量生物质炭和腐植酸显著增加土壤有效态Pb和Cd含量,高剂量生物质炭具有较好的钝化效果。盆栽试验表明,海泡石与石灰配施钝化效果较好,与对照相比,土壤氯化钙提取态Pb、Cd含量分别降低了97.5%、81.4%;玉米根和地上部Cd含量分别降低48.5%、34.0%,Pb含量分别降低35.6%、29.6%;但海泡石与磷材料配施显著增加玉米根Pb含量,对玉米Cd吸收没有显著影响。以上结果表明,重金属高污染农田土壤添加合适的改良剂,可较大幅度降低土壤重金属有效性和植物重金属吸收性。     

连续分级提取法研究春季巢湖沉积物中不同结合态氮的赋存特征

为研究沉积物中不同形态氮的释放能力及其生物可利用性大小,为湖泊水环境生态安全评估提供基础依据,以春季巢湖表层沉积物为例,采用连续分级提取法将氮分为游离态氮（FN）、可交换态氮（EN）、酸解态氮（HN）及残渣态氮（RN）,并研究了这4种形态的赋存特征。结果表明,沉积物中总凯氏氮含量（TKN）在1004—2285mg·kg^-1之间,各形态氮含量大小为HN〉EN〉RN〉FN,占总提取态氮比例分别为78．32％、11．50％、9．76％、0．42％。酸解氨基酸态氮是可矿化态氮最有效贡献者,多元逐步回归方法得到“最优”方程为y=0．696AAN-108．918。连续提取法测得总氮值（TSEN）比用凯氏半微量法测得总氮值（TKN）偏小,但在误差允许的范围内,TSEN可替代半微量凯氏法测得的总氮。     

Contribution of arbuscular mycorrhizal fungi and soil amendments to remediation of a heavy metal-contaminated soil using sweet sorghum

Owing to their potential advantages such as waste reduction, recycling, and economic attributes, fast-growing bioenergy crops have the capacity to effectively phytoremediate heavy metal-contaminated soils. However, little is known about the role of microbial and chemical amendments in phytoremediation using bioenergy crops. Here, we studied the contributions of inoculation with the arbuscular mycorrhizal fungus (AMF) Acaulospora mellea ZZ and three soil amendments, i.e., hydroxyapatite (HAP), manure, and biochar, at doses of 0.1% and 1% (weight:weight) to heavy metal phytoremediation using sweet sorghum grown on an abandoned agricultural soil, with environmentally realistic contamination (2.6 mg kg^-1 Cd, 1 796 mg kg^-1 Pb, and 1 603 mg kg^-1 Zn), in a plant growth chamber. Mycorrhizal colonization, plant biomass and metal accumulation, metal availability, and soil pH were determined in harvested seedlings 12 weeks after sowing. The results showed that root colonization by indigenous AMF decreased by 28%-46% with HAP, but increased after manure and biochar applications as compared to the no amendment control (CK). The AMF inoculation increased root colonization rates by 16%-128% and in particular, alleviated the inhibition of HAP. The remediation effects were highly dependent on the amendment type and dose. Among the three soil amendments, HAP was the most effective in promoting plant growth and phytostabilization of Cd, Pb, and Zn and phytoextraction of Cd, particularly at a dose of 1%. Compared to CK, 1% HAP decreased DTPA-extractable Cd, Pb, and Zn concentrations in soil by 31%-43%, 30%-38%, and 22%-23%, respectively. Manure and biochar also exerted positive effects on heavy metal immobilization, as indicated by lower DTPA extractability, but only the 1% manure treatment showed plant growth-promoting effect. The AMF inoculation did not affect plant growth, but increased soil pH and induced synergistic interactions with amendments on the immobilization of Cd and Pb. In conclusion, soil amendments, particularly HAP, produced positive impacts and synergistic interactions with AMF on the phytostabilization of heavy metals using sweet sorghum. Accordingly, sweet sorghum combined with soil amendments and AMF may be an effective strategy for heavy metal phytoremediation.     

湖南某铅锌矿污染土壤稳定化修复研究

使用海泡石、磷酸二氢钙、钙镁磷肥、氧化钙和氧化镁等土壤改良剂及其组合,对湖南省某铅锌矿冶炼厂附近的重金属污染土壤进行了稳定化修复试验,利用BCR连续提取法进行形态分析,并进行稳定化效果的评价。结果表明,各改良剂组合均能够有效改变土壤中Zn、Cd和Pb的形态分布,弱酸提取态含量的减少率分别为Zn:17.03%~83.13%,Cd:45.03%~99.17%,Pb:54.05%~99.44%,降低重金属的不稳定形态和生物可利用性,稳定化效果显著。改良剂对Zn元素的稳定化效果影响程度为:钙镁磷肥+氧化钙钙镁磷肥+氧化镁钙镁磷肥海泡石+磷酸二氢钙海泡石;对Cd元素的稳定化效果影响程度为:钙镁磷肥+氧化钙钙镁磷肥+氧化镁钙镁磷肥海泡石+磷酸二氢钙海泡石;对Pb元素的稳定化效果影响程度为:海泡石+磷酸二氢钙钙镁磷肥+氧化镁钙镁磷肥+氧化钙钙镁磷肥海泡石。该复合污染土壤中,Zn、Cd、Pb稳定效果最优处理为10%钙镁磷肥+5%氧化钙组合。     

Evaluation of fly ash,apatite and rice straw derived-biochar in varying combinations for in situ remediation of soils contaminated with multiple heavy metals

ABSTRACT

In

-situ sorbent amendment is a relatively low-cost, low-impact approach for remediation of soil contaminated with heavy metals (HMs), and thus is considered a way to be favored in developing countries. In this study, materials of non-hazardous, alkaline agronomic and industrial by-products were used as sorbents to explore their capacity of in situ immobilization of multiple HMs in mining-impacted arable soil. These sorbents included fly ash (FA), biochar (BC) and apatite (AP) and they were implemented with varying ratios of combinations. Results of soil microcosm tests showed that after incubation for 90 days, concentrations of Pb, Zn, and Cd in their exchangeable forms determined by a sequential extraction method significantly decreased in amended soils, as opposed to the unamended control. Of the five sets of amendments, the composite of FA, BC, and AP resulted in the maximum reduction (up to 80%) in the mobility of Pb, Zn, and Cd in soils. The mechanisms underlying the immobilization of HMs in amended soils might involve processes of surface precipitation, ion exchange and complexation, in which the physicochemical properties of sorbent materials played an important role. The immobilization efficacy of sorbent amendments on HMs in soil was further supported by pot experiments in which significant inhibition of HM accumulation in the belowground and aboveground tissues of maize was observed after 50-day cultivation in amended soils as compared with control soil. Together, these results suggest that the application of cost-saving and environmentally friendly materials derived from wastes as sorbents to remediate soils contaminated with multiple HMs is promising for developing countries like Vietnam.     

利用土壤改良剂固定污染土壤中铅、镉的研究进展

Since the inception of industrial revolution, metal refining plants using pyrometallurgical processes have generated the prodigious emissions of lead (Pb) and cadmium (Cd). As the core target of such pollutants, a large number of soils are nowadays contaminated over widespread areas, posing a great threat to public health worldwide. Unlike organic pollutants, Pb and Cd do not undergo chemical or microbial breakdown and stay likely in site for longer duration after their release. Immobilization is an in-situ remediation technique that uses cost-effective soil amendments to reduce Pb and Cd availability in the contaminated soils. The Pb and Cd contamination in the soil environment is reviewed with focus on source enrichment, speciation and associated health risks, and immobilization options using various soil amendments. Commonly applied and emerging cost-effective soil amendments for Pb and Cd immobilization include phosphate compounds, liming, animal manure, biosolids, metal oxides, and biochar. These immobilizing agents could reduce the transfer of metal pollutants or residues to food web (plant uptake and leaching to subsurface water) and their long-term sustainability in heavy metal fixation needs further assessment.     

Influence of plant species and phosphorus amendments on metal speciation and bioavailability in a smelter impacted soil: a case study of food-chain contamination

Purpose

The present research aimed to assess the influence of two phosphorous (P) amendments on metal speciation in rhizosphere soil and the soil–plant transfer of metals.

Materials and methods

Complementary experiments were performed: field experiments on a contaminated cultivated soil and laboratory experiments on an uncultivated contaminated soil to highlight the mechanisms involved in metal-phosphorous interactions. In laboratory experiment, P amendments were added at 120 mg P/kg of soluble KH₂PO₄ amendment and 9,000 mg P/kg of solid Ca₅(PO₄)₃OH amendment.

Results and discussion

Field-culture results showed the possible food-chain contamination due to Pb, Cd, Cu, and Zn phytoaccumulation by pea and mustard plants from a cultivated agricultural soil. Moreover, P-metal complexes were observed by microscopy in the rhizosphere soil. In laboratory experiments, the application of P amendments significantly increased Pb and Zn level in rhizosphere soil compared to control. Phosphate amendments significantly increased metal-P fraction and decreased “oxides” and “organic matter” fractions of Pb and Zn. Soluble-P amendment was more effective than solid P amendment in changing Pb and Zn speciation. The changes in metal speciation are higher in the rhizosphere soil of pea than tomato. Application of P amendments increased Pb and Zn TF root/soil but decreased TF shoot/root.

Conclusions

The effectiveness of in situ metal immobilization technique varies with the type and quantity of applied P amendment as well as plant and metal type.     

不同钝化剂配施硫酸锌对石灰性土壤中镉生物有效性的影响研究

为了降低轻度镉（Cd）污染土壤中Cd的生物有效性以确保农产品安全,以低吸收豆类蔬菜（豇豆）作为供试植物,通过田间试验研究了在轻度Cd污染（Cd1.5mg·kg-1）石灰性土壤中施加赤泥、油菜秸秆、玉米秸秆、赤泥＋油菜秸秆等钝化处理并配施硫酸锌肥料对土壤中Cd的生物有效性的影响。结果表明,与对照相比,不同钝化处理可显著（P〈0.05）降低豇豆豆角中Cd浓度和土壤中可溶态Cd浓度;钝化处理条件下豇豆豆角中Cd浓度降低了27%（玉米秸秆）~83%（赤泥＋油菜秸秆）。在施加钝化剂的基础上,配施硫酸锌肥料可进一步降低豇豆对Cd的吸收,各钝化处理在配施锌肥后,豇豆豆角中Cd平均浓度与未施锌肥相比降低了27%。对不同作物秸秆而言,富含巯基的油菜秸秆比富含纤维素的玉米秸秆钝化效果好。由此可见,在轻度Cd污染的石灰性土壤中,无机钝化剂赤泥和富含巯基的油菜秸秆复合使用是一种高效且环境友好的钝化手段。同时,合理施用锌肥可能会进一步降低作物对Cd的吸收。     

宜兴地区水稻土PbCdCuZn污染及垂直分布特性研究

通过测定宜兴地区34个采样点水稻糙米和不同土层（0～20、20～40、40～60和60～80cm）中Pb、Cd、Cu和Zn含量,利用单项污染指数法和内梅罗污染指数法对土壤表层和糙米重金属含量进行评价,同时分析4种重金属在土壤剖面中的分布规律以及在糙米中的富集特性。结果表明,水稻土表层Ph、Cd、Cu和Zn的平均含量都处于未污染水平,综合评价结果属于清洁（安全）等级;糙米Ph、Cd、Cu和Zn的平均含量也都处在未污染水平,综合评价结果也属清洁（安全）等级。水稻土Ph和Cd的剖面分布属于表层富集型,表层主要受人类活动的影响,而下层跟母质有关;Cu和Zn的剖面分布同属均匀分布型,表层含量略高与人为因素有关,20～40cm和40～60cm含量略低,可能是因为水稻的吸收作用,60—80cm含量比上层都稍高,主要是受成土母质的影响。糙米中4种元素的富集能力存在极显著差异,其大小顺序为Zn（0.282）〉Cd（0．234）〉Cu（0．198）〉Pb（0．014）;糙米Pb、Cd、Cu和Zn的含量与土壤表层相应元素的全量具有极显著的正相关关系,相关系数分别达到0．905、0．925、0．939和0．957;糙米中Cd与Cd／Zn比具有极显著的正相关关系（0．837）,糙米Cd／Zn比为0．002,远低于临界值0．015。     

改良剂对镉污染酸性水稻土的修复效应与机理研究

为探明田间条件下施用石灰、钙镁磷肥、海泡石和腐殖酸等改良剂对Cd污染酸性水稻土的修复效应和作用机理, 通过在Cd污染区建立田间小区试验, 研究了改良剂单施和与石灰配施对Cd污染酸性水稻土中Cd作物有效性的影响。结果表明, 施用改良剂有效地改变了土壤中Cd的存在形态, 除腐殖酸外, 其他改良剂均使土壤酸提取态Cd不同程度地转化为可还原态Cd和残渣态Cd; 施用改良剂可使0.1 mol·L^-1 NaNO₃和 0.01 mol·L^-1CaCl₂提取态Cd 降低26%~97%, 降低效果为石灰+海泡石>海泡石>石灰+钙镁磷肥>钙镁磷肥>石灰>石灰+腐殖酸>腐殖酸; 改良剂使水稻地上部分的Cd吸收量降低6%~49%。试验结果还显示, 施用改良剂提高土壤pH是引起土壤中Cd作物有效性降低的主要原因之一。根据田间试验的结果, 海泡石可推荐作为Cd污染酸性水稻土的改良剂, 而腐殖酸则不宜使用。     

长期污灌农田土壤重金属污染及潜在环境风险评价

以西安市某典型污灌区农田土壤为研究对象,分析长期污水灌溉对表层土壤重金属含量及富集状况的影响,采用内梅罗指数法和Hakanson潜在生态危害指数法对其污染现状及潜在环境风险进行评价。结果表明：长期污灌已导致农田土壤Cd、Cr、Cu、Hg、Ni、Pb和Zn7种重金属相对自然背景有不同程度累积,其富集比例依次为100%、82.69%、100%、100%、80.77%、98.08%和100%,仅有土壤As平均含量低于其背景水平;以国家土壤环境质量标准二级限量值作为污染评价阈值,其中Cd和Hg污染表现突出,按其污染指数平均值排序为Cd〉Hg〉Ni〉Cu〉Zn〉As〉Cr〉Pb;土壤重金属综合潜在环境风险为＂强＂等级,Hg、Cd的环境影响占据主导;随污灌年限增长,离灌渠越近,农田土壤重金属的污染水平和环境风险越高。鉴于该区土壤重金属已呈现较强生态危害性,应及时采取必要防治措施,调整土地利用结构,确保农田环境及农产品安全生产。