不同初始氧化还原条件下土壤中重金属的运移研究Ⅰ：单一Cd、Cu、Zn的土柱实验

以重金属离子镉、铜、锌为研究对象,通过室内土柱混合置换实验,分析了五种不同氧化还原电位对Cd、Cu、Zn在土壤中运移的影响。结果表明,氧化条件的土壤中Cd的穿透曲线(BTCs)峰值大小的顺序为Eh=490 mV>350 mV>240 mV;还原条件的土壤中Cd的BTCs的峰值为Eh=20 mV>100 mV>240 mV。在氧化条件下,高Eh能明显促进Cu在土壤中的迁移;还原条件下,低Eh会抑制Cu的迁移,抑制程度与还原剂浓度无关。与原土(氧化还原电位240 mV)相比,氧化性土壤中Zn运移较快,表现为相对浓度峰值较高,而不同的还原条件对Zn的迁移影响并不明显。三种重金属Cd、Cu、Zn出流液的pH均表现为先下降后上升最后趋于平缓,氧化条件土壤出流液的pH小于还原条件;而Eh正好相反。     

铅-锌-镉复合污染物在土壤-芥菜/油菜系统中的迁移及交互作用

了解重金属复合污染物在土壤-植物系统中的迁移分配情况对污染土壤的安全利用、土壤环境质量标准的修订以及重金属污染土壤的植物修复具有重要意义。通过盆栽试验,以芥菜和油菜为例,研究了铅-锌-镉复合污染物在土壤-植物系统中的迁移分配情况。结果表明：与对照相比,复合污染条件下,芥菜和油菜体内重金属含量显著提高,且Cd含量的提高程度要远远高于Pb和Zn;芥菜和油菜对Cd的吸收达到了100 m g/kg以上,表现出超富集植物的吸收水平。重金属的富集系数大小依次为Cd〉Zn〉Pb,地下部富集系数要高于地上部,转运系数大小为Cd≈Zn〉Pb。Pb、Zn、Cd的富集系数均随各自元素在土壤中含量增大而减小,而且表现为低含量时显著减小,高含量时缓慢减小;重金属在土壤-植物系统的迁移分配深受共存元素的影响,且在不同元素之间和不同浓度范围内表现出不同的特点。Pb、Zn、Cd在芥菜和油菜体中积累量,均与其各自在土壤中的含量成正相关;Zn和Cd对Pb的吸收积累以及Pb对Zn的吸收积累具有明显的抑制作用;Zn-Cd对Zn的吸收积累具有正的交互作用,而对Cd的吸收积累具有负的交互作用。     

铅-锌-镉复合污染物在土壤-芥菜/油菜系统中的迁移及交互作用

了解重金属复合污染物在土壤-植物系统中的迁移分配情况对污染土壤的安全利用、土壤环境质量标准的修订以及重金属污染土壤的植物修复具有重要意义。通过盆栽试验,以芥菜和油菜为例,研究了铅-锌-镉复合污染物在土壤-植物系统中的迁移分配情况。结果表明:与对照相比,复合污染条件下,芥菜和油菜体内重金属含量显著提高,且Cd含量的提高程度要远远高于Pb和Zn;芥菜和油菜对Cd的吸收达到了100 m g/kg以上,表现出超富集植物的吸收水平。重金属的富集系数大小依次为Cd>Zn>Pb,地下部富集系数要高于地上部,转运系数大小为Cd≈Zn>Pb。Pb、Zn、Cd的富集系数均随各自元素在土壤中含量增大而减小,而且表现为低含量时显著减小,高含量时缓慢减小;重金属在土壤-植物系统的迁移分配深受共存元素的影响,且在不同元素之间和不同浓度范围内表现出不同的特点。Pb、Zn、Cd在芥菜和油菜体中积累量,均与其各自在土壤中的含量成正相关;Zn和Cd对Pb的吸收积累以及Pb对Zn的吸收积累具有明显的抑制作用;Zn-Cd对Zn的吸收积累具有正的交互作用,而对Cd的吸收积累具有负的交互作用。     

BCR法在污染农田黑土重金属形态分布研究中的应用

通过对东北地区污染农田黑土剖面的取样调查分析，对重金属Cd、Ph、Cu、Zn在农田黑土中的污染状况及其迁移特征进行了对比研究，并就BCR（the Community Bureau of Reference）连续提取法在农田土壤重金属污染评估中的应用进行了探讨。结果表明，重金属的迁移率大小依次为：Cd〉Cu〉Pb〉Zn，Cd的酸可溶态占全量的比率高于其它重金属。Pb的酸可提取态浓度随土壤深度增加而增大，公路附近土壤中PL、Cu及城市郊区土壤中Cd、Pb和Zn的氧化物结合态含量均随土壤深度的增加而升高，已存在向下迁移的趋势。4种重金属有机结合态在采样区土壤中基本都表现为耕层高于非耕层。研究表明，应用BCR连续提取法有助于确定土壤重金属污染以及重金属向下迁移状况，借助该法可以有效、可靠地对土壤重金属污染进行评估。     

农田土壤重金属淋洗剂筛选与效应分析

为分析不同淋洗剂在不同淋洗条件下对重金属淋洗效果的影响,采用振荡淋洗法对比研究4种淋洗剂(柠檬酸(CA)、酒石酸(TA)、乙二胺四乙酸二钠盐(EDTA)和氨三乙酸三钠盐(NTA))不同浓度、淋洗时间、pH和固液比对重金属复合污染农田土壤中Pb、Cd、Cu和Zn的淋洗效果及单因素最佳淋洗条件下土壤淋洗前后重金属不同形态含量的变化。结果表明,CA和TA的最佳淋洗浓度为0.3mol/L,EDTA和NTA为0.05mol/L;CA和NTA的最佳淋洗时间为480min,EDTA和TA为720min;4种淋洗剂的最佳淋洗pH均为3,最佳固液比均为1∶20。单因素最佳淋洗条件下,EDTA对土壤重金属去除效果最佳,对Pb、Cd、Zn和Cu的去除率分别为67.4%,61.0%,13.8%和76.0%;NTA效果次之,去除率分别为41.6%,42.4%,9.9%和54.3%。土壤重金属去除率随淋洗剂pH的降低而升高,随固液比的增加而增加,随淋洗剂CA与TA浓度增大而增大。淋洗剂对土壤重金属的解吸动力学曲线符合准二级动力学模型,解吸过程为化学解吸,且解吸反应速率受土壤重金属含量与淋洗剂浓度控制。土壤重金属在淋洗剂作用下的解吸速率为Cd>Pb≈Zn≈Cu。EDTA和NTA淋洗显著降低土壤中Pb、Cd、Zn和Cu铁锰氧化态和有机结合态的含量,CA和TA显著降低Pb、Cd、Zn和Cu铁锰氧化态的含量。淋洗剂对重金属的去除效率为EDTA>NTA>CA>TA。     

绿化植物废弃物对重金属迁移的影响

采用土柱模拟实验,比较研究了覆盖绿化植物废弃物与土壤之上和绿化植物废弃物与土壤混合处理对城市绿地土壤中重金属淋溶的影响。结果表明,Zn、Pb和Cd均在80天后淋溶完全,而Cu有所不同,在80天后又有增加的趋势,原因可能跟重金属与有机质的结合能力有关。此外,绿化植物废弃物与土壤相混合能抑制Cu、Zn、Pb和Cd向下淋溶,而绿化植物废弃物覆盖于土壤之上则有促进Cu、Zn、Pb和Cd淋溶的趋势,且不论是混合处理还是覆盖处理,20cm厚绿化植物废弃物的处理均比10cm厚绿化植物废弃物处理对Cu、Zn、Pb和Cd的促进或抑制作用大。研究还得知,Cu、Zn、Pb和Cd的迁移还与土壤pH有关,低pH土壤有利于重金属的淋溶。     

Cd/Cu/Pb对磺胺嘧啶在土壤中吸附迁移的影响

通过室内批平衡实验和土柱出流实验,探讨了不同浓度镉(Cd)及相同浓度的Cd、铜(Cu)、铅(Pb)对磺胺嘧啶在土壤中吸附、迁移的影响,并分别用Freundlich、Langmuir、Linear方程及Hydrus-1D中的单点和两点吸附模型模拟其在土壤中的吸附、运移过程。结果表明:当Cd浓度为10.0mg·kg~(-1)时促进磺胺嘧啶的吸附;Cd浓度为1.0、300.0mg·kg~(-1)时抑制磺胺嘧啶吸附;Cd浓度为100.0 mg·kg~(-1)时对磺胺嘧啶的吸附无影响;300 mg·kg~(-1)的Cd、Cu、Pb存在时,磺胺嘧啶吸附量大小顺序为:CdCuPb。土柱出流实验中,当Cd浓度为10.0mg·kg~(-1)时,磺胺嘧啶在土柱中的迁移速度最慢,其他浓度对迁移影响不明显;Cd、Cu、Pb相比较而言,Cu存在时磺胺嘧啶的迁移最快,Cd存在时迁移最慢。在对静态吸附特征的拟合过程中,Linear方程拟合效果最好,决定系数R~2均在0.98以上;Hydrus-1D模拟时,两点模型可更好地拟合磺胺嘧啶的运移特征,R~20.907,均方根误差RMSE0.051,瞬时吸附f所占分数较高,说明磺胺嘧啶在迁移过程中存在较大程度的瞬时吸附。     

重金属的土水分配行为研究——根际土壤溶液采样器的应用

采用根际土壤溶液采样器(Rhizon-SMS)原位采集河南平原耕地土壤溶液.用土壤溶液中重金属浓度对数作为因变量、土壤溶液理化性质作为自变量,进行多元线性逐步回归,结果表明:只有有机碳进入Cu的相关方程,pH进入Cd的相关方程.土壤溶液pH和土壤中的Zn都作为自变量进入Zn的相关方程.土壤溶液中的Cu与pH没有线性关系,而Cd和Zn与土壤溶液pH有显著的线性关系(p＜0.01).计算了土壤中Cu、Cd、Zn在土壤与土壤溶液中的分配系数Kd.本研究中,3种重金属的Kd大小顺序为:Cu＞Zn＞Cd.根据Freeze 和Cherry模型,联合log(Kd-Cd)、log(Kd-Zn)与pH的线性关系,估计了Cd和Zn在土壤中的迁移速度.     

EDTA和柠檬酸对污染土壤中重金属的解吸动力学及其形态的影响

利用批处理振荡解吸平衡法研究了0.05 mol/L的乙二胺四乙酸钠(EDTA)和柠檬酸对污染土壤中Cd,Pb,Cu,Zn的解吸动力学特征,并采用优化的BIER(European Community Bureau of Reference)连续提取法分析了EDTA和柠檬酸处理前后土壤中重金属形态和生物有效性的变化.结果表明,污染土壤中重金属Cd,Pb,Cu,Zn的解吸率随着解吸时间的延长而不断增加,但解吸速率随解吸时间的延长而不断降低.EDTA对Pb,Cu的解吸能力显著大于柠檬酸,柠檬酸对Zn的解吸能力显著大于EDTA,柠檬酸和EDTA对Cd的解吸能力相差不大.EDTA和柠檬酸对4种重金属解吸能力的顺序分别为:Pb＞Cd＞Zn＞Cu和CA＞Zn＞Pb＞Cu.双常数方程是描述污染土壤中Cd,Pb,Cu,Zn解吸动力学过程的最佳方程.EDTA去除的重金属主要以酸提取态和可还原态存在,柠檬酸去除的重金属主要以酸提取态存在.EDTA和柠檬酸处理后.污染土壤中Cd,Pb,Cu,Zn的生物有效性降低.     

重金属在矿区土壤——蔬菜系统的吸收与迁移特性研究

重金属污染土壤的农产品安全倍受大家的关注。研究选择某铅锌矿区周边的蔬菜地,采集叶菜类蔬菜及土壤样品,研究Cd、Pb、Cu、Zn在土壤中的赋存形态及其在土壤-蔬菜系统中的迁移特性。结果表明,污染土壤中Cd、Pb、Zn超标,分别为国家标准限值的1.44～6.44倍、2.97～3.88倍和1.30～2.30倍。BCR连续提取结果显示,Cd、Pb以可还原态为主,Cu、Zn以可还原态和残渣态为主,可还原态Cd、Pb、Cu、Zn分别占总量的70.6%、79.0%、34.4%和38.1%;残渣态Cu、Zn分别占总量的34.6%和30.2%。酸可提取态Zn、Cd分别达13.2%和6.3%。供试蔬菜茎叶中Pb含量超标,为国家标准限值的1.50～5.83倍。蔬菜茎叶中Cd、Pb含量与其土壤中可还原态含量显著正相关,Cd含量与土壤酸可提取态Cd含量显著正相关。蔬菜Cd的富集系数(BCF)相对较高(0.61～3.34),其中水芹和香芹Cd、Pb、Zn的BCF值显著高于其他蔬菜。蔬菜中Zn的迁移系数(TF)较高(0.54～2.07)。叶用芥菜中Cd、Pb、Zn的TF值较高,分别为1.02、2.25、1.62。因此,在污染土壤蔬菜风险评价中需要考虑不同蔬菜品种对重金属吸的吸收迁移特性的差异。     

Modeling Surfactant LAS Influenced PAHs Migration in Soil Column

The objective of the present work was to study the transport of Polycyclic Aromatic Hydrocarbons (PAHs) in artificially contaminated and oil field soil columns while Linear Alkylbenzene Sulfonate (LAS) was used as leaching solvent. Through soil column leaching experiments, the through curves (BTCs) of the tracer (Br^?) and PAHs were obtained. The batch equilibrium experiments were conducted. The partition coefficients, and the retardation factor (R) were calculated. Nonlinear least-squares optimization approach was used to fit BTCs of Br^? and PAHs. The symmetrical BTC for Br^? was fitted using equilibrium convention-dispersion equation (CDE) model, and the physical and hydrodynamic parameter, i.e. the dispersion coefficient (D) was calculated. Based on these, the equilibrium and non-equilibrium CDE models were applied to fit the asymmetrical and tailing BTCs of PAHs. Results showed that two-site CDE model is better in fitting the observed data. The concentration distributions of PAHs with leaching time at different depth in the soil column were also estimated using two-site CDE model.     

Influence of pH on the release and chemical fractionation of heavy metals in sediment from a suburban drainage stream in an arid mine-based oasis

Purpose

The objectives of this study were to explore the influences of pH on the release of Cu, Zn, Cd, Pb, Ni, and Cr in sediments derived from the upstream, middle, and downstream reaches of Dongdagou stream in Gansu Province, Northwest China, and to examine the fractionation changes of heavy metals in the sediments after reaching their release equilibrium under different pH conditions.

Materials and methods

Sediment samples were obtained using a stainless steel grab sampler to collect the uppermost 10 cm of sediment from the channel bed. The pH-dependent release experiment was conducted in the solid-to-liquid ratio of 1:20 at different pH values (2, 4, 6, 8, 10, and 12) at room temperature. The total Cu, Zn, Cd, Pb, Ni, and Cr concentrations in the sediments were digested using an acid digestion mixture (HNO₃ + HF + HClO₄) in an open system. Metal fractionation of selected sediments was obtained using the Tessier sequential extraction procedure. Heavy metal concentrations in the samples were determined using atomic absorption spectrophotometry.

Results and discussion

The mean concentrations of heavy metals in sediments decreased in the following order: Zn (1676.67 mg kg^?1) > Pb (528.65 mg kg^?1) > Cu (391.34 mg kg^?1) > Cr (53.48 mg kg^?1) > Ni (34.27 mg kg^?1) > Cd (11.53 mg kg^?1). Overall, the solubility of Cu, Zn, Cd, Pb, and Ni decreased with increasing pH, and they were strongly released at pH 2. Moreover, the solubility of Cr increased with increasing pH, and its release was highest at pH 12. After reaching the release equilibrium of heavy metals under different pH conditions, the percentages of organic Cu, Zn, Cd, and Fe-Mn oxyhydroxide Pb decreased, compared to their initial fractions. The residual fractions of Ni and Cr were dominant, regardless of pH.

Conclusions

The average concentrations of Cu, Zn, Cd, and Pb in sediments were highly elevated compared with the soil background values in Gansu Province, China. The results of this pH-dependent release experiment showed that the release behaviors of Cu, Zn, Pb, and Cr followed an asymmetric V-shaped pattern, whereas Cd and Ni followed an irregular L-shaped pattern. The changes in the release of heavy metals in sediments were related to their redistribution between chemical fractionations.

     

镉在中性和碱性土柱中不同深度处的运移模拟

Human health has been potentially threatened by cadmium (Cd) contained in sewage irrigation water.Previous studies of Cd transport in soils were mainly conducted using small soil cores with pH values less than 6.The objectives of this study were to determine the parameters of the convection-dispersion equation (CDE) for Cd transport in relatively larger columns with neutral and alkaline soils,and to investigate the parameters' variability with depth.The soil columns were 50 cm in length and 12.5 cm in diameter.Ceramic suction lysimeters were buried at depths of 2.5,7.5,17.5,27.5,and 37.5 cm to abstract soil solution.Cd concentration in the soil solution samples were subsequently analyzed to obtain breakthrough curves (BTCs).Equilibrium and nonequilibrium models in CXTFIT program were used to estimate parameters of the CDE.The results suggested that both equilibrium and non-equilibrium models performed well in modeling Cd transport.The hydrodynamic dispersion coefficient (D) ranged from 0.18 to 10.70 cm 2 h 1,showing large differences among different depths.The retardation factor (R d) ranged from 25.4 to 54.7 and the standard deviation of R d value was lower than 30% of the mean value.Precipitation coefficient (R p) decreased consistently with increasing depth,varying from 1.000 × 10 10 to 0.661 h 1.Sensitivity tests showed that D was less sensitive than R d.These results would be helpful in understanding the transport and retention of Cd in non-acidic soils.     

低分子有机酸对土壤中重金属的解吸及影响因素

研究了柠檬酸、草酸、酒石酸和苹果酸对矿区土壤中重金属Pb、Cd、Cu和Zn的解吸行为,并探讨了介质pH值对其解吸土中重金属的影响。振荡解吸试验结果表明四种低分子有机酸对供试污染土壤中Pb、Cd、Cu和Zn都具有一定的解吸能力。由于土壤中重金属有效态含量较低,各重金属的解吸率都不高。在对Pb和Cd的解吸中,各低分子有机酸能力大小顺序为柠檬酸>酒石酸≈苹果酸>草酸;Cu的解吸顺序为柠檬酸>草酸>酒石酸≈苹果酸;Zn的解吸顺序为酒石酸>柠檬酸≈苹果酸>草酸。低分子有机酸随浓度的增加,其解吸能力提高。低分子有机酸对重金属的解吸量随pH值的降低而增加。     

Comparison of three models describing bromide transport affected by different soil structure types

This study was conducted to investigate the effects of soil structure on bromide (Br) transport through three soils with granular, prismatic, and single-grain structures. The breakthrough curve (BTC) of the single-grain structure was sigmoidal, symmetrical and similar to a piston flow, showing the dominance of mass flow. In contrast, the BTCs of the granular and prismatic structures were initially steep, becoming more gradual at high pore volumes (PVs). The stable structure and preferential pathways caused the early breakthrough of Br in the leachate of these columns. The convection–dispersion equation (CDE), mobile–immobile water (MIM), and dual-permeability (DP) models were fitted to observed data using the program HYDRUS-1D. The equilibrium transport model (CDE) was not as successful as non-equilibrium (MIM and DP) models in describing the Br transport in prismatic and granular soil columns, although it was able to describe the Br transport in single-grain column well. Overall, the results demonstrated the importance of soil structure in pollutant transport through soils.     

石灰石和海泡石组配对水稻糙米重金属积累的影响

为了研究组配改良剂(石灰石+海泡石,LS)对于重金属Pb、Cd、Cu和Zn复合污染稻田的修复效果,在湘南某矿区附近稻田中进行了组配改良剂的田间试验。结果表明:施用0~1.8 kg m-2的组配改良剂LS使土壤pH和CEC显著增加,使土壤中Pb、Cd、Cu和Zn交换态含量显著降低。土壤Pb、Cd、Cu和Zn交换态含量的降低是pH升高,土壤胶体的CEC增加及土壤吸附能力增强的共同作用。施用组配改良剂LS显著降低了3个水稻品种(黄华占、丰优9号、Ⅱ优93)糙米中Pb、Cd和Cu的累积量,最大降幅分别为55.8%、66.9%、37.4%,而对糙米中Zn的含量没有明显影响。当LS施用量为1.8 kg m-2时,能使丰优9号糙米中Cd含量(0.195 mg kg-1)达到国家食品中污染物限量标准(0.20 mg kg-1)以下。土壤中交换态Pb、Cd和Cu含量的降低是糙米中重金属累积量减少的原因。土壤交换态Pb、Cd和Cu含量的对数值(lnC交换态)与其糙米中含量(lnC糙米)的对数值之间存在显著的线性相关关系。     

Differential Sorption Behavior of Cadmium,Lead, Zinc,and Copper in Some Tropical Soils and Their Environmental Implications

This study evaluated cadmium (Cd), lead (Pb), zinc (Zn), and copper (Cu) sorption characteristics of three tropical soils. Data obtained conformed to Freundlich sorption model and the S-shaped isotherm curve. Sorption efficiency of Zn and Pb were highest in alkaline soil while slightly acid soil had the highest Cd and Cu sorption efficiency for monometal sorption. In competitive sorption, metals were more sorbed in slightly acid soil while the least efficiency was recorded in acid soil. Distribution coefficient; K_d (average across soil types) in monometal sorption followed the order: Pb > Zn > Cd > Cu. For competitive sorption, the order was Zn > Pb > Cu > Cd. When in competition, Cd was preferentially sorbed in slightly acid and alkaline soils and Zn for acid soil. Conclusively, lead is more in equilibrium solution when in competition with Cd, Zn and Cu making it potential agent of soil and groundwater pollution.     

海泡石改良土壤效果研究

通过连续三季盆栽试验研究海泡石提高油菜生物量,降低油菜Cd、Pb、Cu、Zn浓度及土壤Cd、Pb、Cu、Zn有效态浓度的效果。结果表明:海泡石在不同程度上提高了三季油菜的生物量,适量的海泡石可降低油菜中Cd、Pb、Cu、Zn浓度及土壤Cd、Pb、Cu、Zn有效态浓度。海泡石降低油菜中重金属浓度效果,第一季,Zn>Pb>Cd>Cu,第二季,Pb>Zn>Cd>Cu,第三季,Zn>Cd>Pb>Cu;降低有效态浓度的效果,第一季,Cd>Cu>Pb>Zn,第二季,Cu>Cd>Zn>Pb,第三季,Pb>Cd>Cu>Zn。因此,海泡石可用于土壤改良,提高油菜生物量,降低油菜中Cd、Pb、Cu、Zn浓度及土壤中Cd、Pb、Cu、Zn有效态浓度。海泡石降低油菜中重金属浓度总效果为Zn>Pb>Cd>Cu;降低土壤重金属有效态浓度总效果为Cd>Cu>Pb>Zn。     

Prediction of available heavy metals by six chemical extractants in a sewage sludge‐amended soil

Abstract

In a field experiment conducted during three years in a sandy‐loam, calcareous soil, one aerobically digested sewage sludge (ASL) and another anaerobically digested sewage sludge (ANSL) were applied at rates of 400, 800, and 1,200 kg N/ha/year, and compared with mineral nitrogen fertilizer at rates of 0, 200, 400, and 600 kg N/ha/year in a cropping sequence of potato‐corn, potato‐lettuce, and potato, the first, second, and third year, respectively. Results showed that the highest values of soil extractable metals were obtained with aqua regia, whereas the lowest levels with DTPA. All metal (Zn, Cu, Cd, Ni, Pb, and Cr) gave significant correlations between metal extracted with the different extractants and metal loading applied with the sludges. The metal extractable ion increased over the control for Zn, Cu, Cd, Ni, Pb, and Cr extracted with DTPA, EDTA (pH 8.6) and 0.1 N HC1, for Zn, Cd, Ni, Pb, and Cr extracted with EDTA (pH 4.65) and AB‐DTPA, and for Zn, Cd, Ni, and Cr extracted with aqua regia. The level of metal‐DTPA extractable resulted highly correlated with that obtained by the other methods, except the Ni‐aqua regia extractable. The soil extractable elements which showed significant correlations with metals in plant were: Zn, Cu, Cd, and Ni in potato leaves, Cd, Ni, and Pb in corn grain, and Zn and Cd for lettuce wrapper leaves. In general, all the chelate based extractants (DTPA, EDTA pH 4.6, EDTA pH 8.6, AB‐DTPA) were equally useful as indicator of plant available metals in the soil amended with sludge.