Remediation technologies for metal-contaminated soils and groundwater: an evaluation

Metals including lead, chromium, arsenic, zinc, cadmium, copper and mercury can cause significant damage to the environment and human health as a result of their mobilities and solubilities. The selection of the most appropriate soil and sediment remediation method depends on the site characteristics, concentration, types of pollutants to be removed, and the end use of the contaminated medium. The approaches include isolation, immobilization, toxicity reduction, physical separation and extraction. Many of these technologies have been used full-scale. This paper will review both the full-scale and developing technologies that are available. Contaminants can be isolated and contained to minimize further movement, to reduce the permeability of the waste to less than 1×10⁻⁷ m/s (according to U.S. guidelines) and to increase the strength or bearing capacity of the waste. Physical barriers made of steel, cement, bentonite and grout walls can be used for isolation and minimization of metal mobility. Another method is solidification /stabilization, which contains the contaminants in an area by mixing or injecting agents. Solidification encapsulates contaminants in a solid matrix while stabilization involves formation of chemical bonds to reduce contaminant mobility. Another approach is size selection processes for removal of the larger, cleaner particles from the smaller more polluted ones. To accomplish this, several processes are used. They include: hydrocyclones, fluidized bed separation and flotation. Addition of special chemicals and aeration in the latter case causes these contaminated particles to float. Electrokinetic processes involve passing a low intensity electric current between a cathode and an anode imbedded in the contaminated soil. Ions and small charged particles, in addition to water, are transported between the electrodes. This technology have been demonstrated in the U.S. full-scale, in a limited manner but in Europe, it is used for copper, zinc, lead, arsenic, cadmium, chromium and nickel. The duration of time that the electrode remains in the soil, and spacing is site-specific. Techniques for the extraction of metals by biological means have been not extensively applied up to this point. The main methods include bioleaching and phytoremediation. Bioleaching involves Thiobacillus sp. bacteria which can reduce sulphur compounds under aerobic and acidic conditions (pH 4) at temperatures between 15 and 55°C. Plants such as Thlaspi, Urtica, Chenopodium, Polygonum sachalase and Alyssim have the capability to accumulate cadmium, copper, lead, nickel and zinc and can therefore be considered as an indirect method of treating contaminated soils. This method is limited to shallow depths of contamination. Soil washing and in situ flushing involve the addition of water with or without additives including organic and inorganic acids, sodium hydroxide which can dissolve organic soil matter, water soluble solvents such as methanol, nontoxic cations, complexing agents such as ethylenediaminetetraacetic acid (EDTA), acids in combination with complexation agents or oxidizing/reducing agents. Our research has indicated that biosurfactants, biologically produced surfactants, may also be promising agents for enhancing removal of metals from contaminated soils and sediments.

In summary, the main techniques that have been used for metal removal are solidification/stabilization, electrokinetics, and in situ extraction. Site characteristics are of paramount importance in choosing the most appropriate remediation method. Phytoremediation and bioleaching can also be used but are not as well developed.     

铬污染土壤和地下水的修复技术研究进展

上海20世纪70年代含铬废水排放量大,其中六价铬毒性大、溶解度高、迁移性强,极易随水淋溶污染地下水系统。开展高效、经济的土壤和地下水中铬污染修复方法的研究,具有重要的现实意义。本文系统地综述了铬污染场地修复技术现状,包括还原稳定、渗透反应墙、电动修复、生物修复等,重点探讨了上海地区污染深度大于4m的低渗透性的铬污染场地电动反应墙联合修复技术的发展趋势。     

Mathematical model for hydraulically aided electrokinetic remediation of aquifer and removal of nonanionic copper

One of the most cost-effective in situ technologies for soil and groundwater (i.e., aquifer) remediation is electrokinetic remediation. In electrokinetic remediation, electromigration due to electric field is combined with hydromigration due to hydraulic flow by purge water to remove pollutants from aquifers through the pore water. This study aims at investigating theoretically the role of electromigration (as active movement) of pollutants and the role of hydromigration (as passive movement) of pollutants in electrokinetic remediation, and making it clear that the control variables for electrokinetic remediation are the applied voltage and the hydraulic flow rate. These aims are pursued by construction of a mathematical model based on physico-chemical considerations and by model simulations of the electrokinetic remediation applied to the virtual aquifer polluted by heavy metals of copper sulfate. According to numerical simulations with the model: (1) heavy metal (nonanionic copper) is removed from the upstream anode region and accumulated in the downstream cathode region; (2) to carry away the heavy metal outside the aquifer (global removal), hydromigration by purge water flow is essential; and (3) electromigration contributes mainly to the redistribution of heavy metals within the aquifer (local removal and local accumulation).     

Electrokinetic iron pan generation in unconsolidated sediments: implications for contaminated land remediation and soil engineering

Electrokinetic remediation is an emerging technology that has generated considerable interest as a technique for the in situ remediation of clay-rich soils and sediments. Despite promising experimental results, however, at present there is no standardised universal electrokinetic soil/sediment remediation approach. Many of the current technologies are technically complex and energy intensive, and geared towards the removal of 90% or more of specific contaminants, under very specific field or laboratory-based conditions. However, in the real environment a low-tech, low-energy contaminant reduction/containment technique may be more appropriate and realistic. Such a technique, FIRS (Ferric Iron Remediation and Stabilisation), is discussed here. The FIRS technique involves the application of a low magnitude (typically less than 0.2 V/cm) direct electric potential between two or more sacrificial, Fe-rich, electrodes emplaced in, or either side of, a contaminated soil or sediment. The electric potential is used to generate a strong pH (and E_h) gradient within the soil column (pH 2–13), and force the precipitation of an Fe-rich barrier or “pan” in the soil between the electrodes. Geochemical and geotechnical data for FIRS-treated sediments from the Ravenglass estuary, Cumbria, UK indicate that the technique can significantly reduce contaminant concentration in treated soil, by remobilisation of contaminants and concentration on, or around, the Fe-rich barrier. Arsenic, in particular, seems highly amenable to the FIRS treatment, due to its solubility under the high pH conditions generated near to the cathode, and its marked geochemical affinity with the freshly precipitated Fe oxides and oxyhydroxides in the Fe barrier. Geotechnical tests indicate that the Fe barrier produced by the technique is practically impervious (permeability = 10⁻⁹ m/s or less), and has moderate mechanical strength (UCS ∼11 N/mm²). Notably, a large increase in shear strength in the treated soil near to the anode electrode (due to Fe cementation and/or dewatering) is also observed, without significant loss of porosity. The data indicate that the FIRS technique shows considerable promise as an in situ method for contaminated land remediation and soil water containment, and for improving the mechanical properties of soils (contaminated or otherwise) for civil engineering purposes.     

Heavy metal distribution in soil and plant in municipal solid waste compost amended plots

A field study was carried out to evaluate long-term heavy metal accumulation in the top 20 cm of a Tunisian clayey loam soil amended for four consecutive years with municipal solid waste compost at three levels (0, 40 and 80 t/ha/y). Heavy metals uptake and translocation within wheat plants grown on these soils were also investigated. Compared to untreated soils, compost-amended soils showed significant increases in the content of all measured metals: cadmium, chromium, copper, nickel, lead and zinc in the last three years, especially for plots amended with municipal solid waste compost at 80 t/ha/y. Wheat plants grown on compost-amended soils showed a general increase in metal uptake and translocation, especially for chromium and nickel. This heavy metal uptake was about three folds greater in plots amended at 80 t/ha/y as compared to plots amended at 40 t/ha/y. At the end of the experimental period, the diluting effect resulting from enhanced growth rates of wheat plants due to successive compost applications resulted in lower concentrations in the plants (grain part) grown on treated plots. On the other hand, chromium and nickel were less mobile in the aerial part of wheat plants and were accumulated essentially in root tissues. Plant/soil transfer coefficients for compost-amended treatments were higher than threshold range reported in the literature, indicating that there was an important load/transfer of metal ions from soils to wheat plants.     

Fundamental aspects of prolonged electrokinetic flows in kaolinites

Electrokinetic flows include the migration of fluid, chemicals, fine particles, bacteria, and electrons through a soil–fluid–chemical system driven by an externally applied direct-current (d.c.) electric field. The promising potential of electrokinetic remediation of contaminated fine-grained soils has stimulated recent interest in the study of electrokinetic flow processes, in particular the impact of a prolonged application of a d.c. electric field on fine-grained soils. The results of a bench-scale laboratory experimental investigation on some of the fundamental aspects of prolonged electrokinetic flows in kaolinites, including gas generation rates at power electrodes, electrochemical behaviour of the soil–fluid–chemical system, time variation of electric current intensity flowing through the soil, pH gradient development in the soil, effects of reservoir chemistry on electro-osmotic fluid volume flow rate and flow direction through the soil, time variation of electro-osmotic volume flow rate, and energy requirements per unit volume of fluid transported, are presented in this paper. Effects of soil type and pore fluid chemistry on these aspects were also studied.     

pH influence on sorption characteristics of heavy metal in the vadose zone

Sorption is an important process in the modelling and prediction of the movement of heavy metals in unsaturated clay barriers. This experimental study investigates the effect of pH changes in the acidic range on the sorption characteristics of heavy metals such as: lead, copper and zinc in an unsaturated soil. A series of one-dimensional coupled solute and moisture leaching column tests, using different heavy metal solutions, were conducted on an unsaturated illitic soil at varying pH values. Variations of volumetric water content (VWC) with distance were measured for different time durations, and concentrations of heavy metals in the liquid and solid phases were analysed. Partitioning coefficient profiles of contaminants along the soil column were determined for each individual layer in the soil.

Results from column leaching tests showed that the sorption characteristics of heavy metals are controlled by many factors which should be taken into consideration, i.e. the VWC, time of wetting, soil pH, and the influent heavy metal concentrations. Simplification of K_d as a constant and of the VWC as a linear function cannot be considered a good assumption and may lead to an improper evaluation of the sorption phenomena and also to serious errors in predicting contaminant transport through unsaturated soils.     

Heavy metal pollution in the soil surrounding a thermal power plant in Playas de Rosarito,Mexico

The generation of electricity has been identified as one of the main pollutant activities, and some studies have established an increment of heavy metals in soil in the areas surrounding these plants. The aim of this study was to evaluate the soil concentrations of heavy metals in the zone surrounding a thermoelectric power in Mexico. Thirty-two top soil samples (0–5 cm) were collected; additionally, four depth profiles (1 m) were investigated. Median concentrations for chromium, vanadium, nickel, mercury, and cadmium were 47, 47, 73, 0.02, and 0.01 mg/kg, respectively. Higher Cr, Ni, and V concentrations were observed in the soil depth profiles located closer to the plant in comparison with the concentrations found in the soil depth profile located further away from the plant; these results may indicate a possible accumulation of these metals. The geoaccumulation index results indicated that most of the sites were in the classifications of unpolluted and unpolluted to moderately polluted (classes 1 and 2). The statistical results showed that downwind of the plant in relation to the prevailing winds, there was a strong correlation between soil concentrations of chromium, copper, nickel, and vanadium. Based on the results of this study, it can be concluded that the use of fuel oil at the thermoelectric plant contributed to the accumulation of vanadium and nickel in the soil of the surrounding areas, as well as chromium and copper.     

Heavy metals contamination in water and sediments of an urban river in a developing country

Water and sediment samples were collected from 20 location of the Buriganga river of Bangladesh during Summer and Winter 2009 to determine the spatial distribution, seasonal and temporal variation of different heavy metal contents. Sequential extraction procedure was employed in sediment samples for the geochemical partitioning of the metals. Total trace metal content in water and sediment samples were analyzed and compared with different standard and reference values. Concentration of total chromium, lead, cadmium, zinc, copper, nickel, cobalt and arsenic in water samples were greatly exceeded the toxicity reference values in both season. Concentration of chromium, lead, copper and nickel in sediment samples were mostly higher than that of severe effect level values, at which the sediment is considered heavily polluted. On average 72 % chromium, 92 % lead, 88 % zinc, 73 % copper, 63 % nickel and 68 % of total cobalt were associated with the first three labile sequential extraction phases, which portion is readily bioavailable and might be associated with frequent negative biological effects. Enrichment factor values demonstrated that the lead, cadmium, zinc, chromium and copper in most of the sediment samples were enriched sever to very severely. The pollution load index value for the total area was as high as 21.1 in Summer and 24.6 in Winter season; while values above one indicates progressive deterioration of the sites and estuarine quality. The extent of heavy metals pollution in the Buriganga river system implies that the condition is much frightening and may severely affect the aquatic ecology of the river.     

Ultrasonically enhanced electrokinetic remediation for removal of Pb and phenanthrene in contaminated soils

Electrokinetic and ultrasonic remediation technologies were studied for the removal of heavy metal and polycyclic aromatic hydrocarbon (PAH) in contaminated soils. The study emphasized the coupled effects of electrokinetic and ultrasonic techniques on migration as well as clean-up of contaminants in soils. The laboratory soil flushing tests combined electrokinetic and ultrasonic technique were conducted using specially designed and fabricated devices to determine the effect of both techniques. The electrokinetic technique was applied to remove mainly the heavy metal and the ultrasonic technique was applied to remove mainly organic substance in contaminated soil. A series of laboratory experiments involving electrokinetic and electrokinetic and ultrasonic flushing tests were carried out. Natural clay was used as a test specimen and Pb and phenanthrene were used as contaminants. An increase in out flow, permeability and contaminant removal rate was observed in electrokinetic and ultrasonic tests. Some practical implications of these results are discussed in terms of technical feasibility of in situ implementation of electrokinetic ultrasonic remediation technique.     

Modification of the properties of salt affected soils using electrochemical treatments

In this project, an in situ soil treatment technique using the principles of electrokinetics was tested using laboratory experimental models in order to identify the potential of this approach in modifying and reinstating the physical properties of salt affected soils. Experiments were conducted in the laboratory using saline-sodic soils collected from two salt affected regions in central Victoria, Australia. Soil specimens were compacted in glass tanks to reproduce in situ density and in situ water content. Using mild steel electrodes inserted into the soil, a direct current was passed through the soil under a constant potential gradient of 0.5 V/cm for a period of 14 days. In separate experiments, distilled water and a saturated lime solution were introduced to the soil via the anode over this experimental period. It was observed that the soil dispersion, otherwise known as soil sodicity (measured as ESP—Exchangeable Sodium Percentage and SAR—Sodium Absorption Ratio) decreased by up to 90% in most regions of the soil between the electrodes. The compressive strength of the soil increased in excess of 100% with electrokinetic treatment alone while the lime-enhanced electrokinetic treatment led to an almost 200% strength increase. The liquid limit and plastic limit of the soil increased causing the plasticity index to decrease, indicating increases in soil compressive strength and workability. These results indicate the potential of this technique for improving the physical properties of salt affected soils both effectively and efficiently, and in particular gives hope for the remediation of salt affected land for infrastructure management and development.     

Characterization of heavy metal contaminated soils in Northern Cyprus

The Lefke region of Northern Cyprus was a site of intense copper mining and smelting activities until the 1970s, which produced large tailings. This study was initiated to characterize the heavy metal contamination of soils of the area and to assess the influence of this site on the surface seawater quality along the coastline. Soil and seawater samples were collected and analysed. Copper and arsenic concentrations exceeded the limits for 'extremely polluted' soils for some samples, which can be classified as 'polluted' by zinc, cadmium and lead. The results showed that seawater was seriously polluted by chromium, nickel and copper in the vicinity of the smelting facility. Copper and iron concentrations increased tenfold after rainfall (wet period), indicating the contribution of tailings to marine pollution. There is an urgent need for remediation treatment for the site.     

Heavy metals contamination of the Quaternary coral reefs, Red Sea coast, Egypt

In order to assess pollutants and impact of environmental changes along the Egyptian Red Sea coast, seven recent and Pleistocene coral species have been analyzed for Zn, Pb, Mn, Fe, Cr, Co, Ni, and Cu. Results show that the concentration of trace elements in recent coral skeletons is higher than those of Pleistocene counterpart except for Mn and Ni. In comparison with recent worldwide reefs, the present values are less than those of Central America coast (iron), Gulf of Aqaba, Jordan (lead, copper), Gulf of Mannar, India (chromium, zinc, manganese), Costa Rica, Panama (chromium, nickel), North-west coast of Venezuela and Saudi Arabia (copper). The present values are higher than those of Gulf of Aqaba, Jordan (iron, zinc, manganese), Gulf of Mannar, India (lead, cobalt, nickel), North-west coast of Venezuela (lead, zinc, chromium, manganese), Australia (copper, nickel, zinc, manganese). The highest values were recorded in Stylophora pistillata (iron, lead and copper), Acropora cytherea (cobalt), Pocillopora verrucosa (zinc) and the lowest concentrations were recorded in Goniastrea pectinata (iron, chromium, copper and nickel), Favites pentagona (lead, zinc and manganese), and Porites lutea (cobalt). The differences in metals content among the studied species are attributed to differences in microstructure and microarchitecture.     

Effects of heavy metal pollution on the soil microbial activity

The effects of heavy metals on soil microbial processes were investigated over a period of six weeks. Analytical grade (Sigma) sulphate salts of copper, zinc and nickel were added individually and in combinations to soil samples and incubated in different plastic pots. Samples were taken from the pots forthnightly and the rates of microbial carbon and nitrogen mineralization, microbial biomass carbon and respiration were measured. The results showed the effect of metals on the measured parameters were significant (P<0.05.). By the 6^th week postreatment, the rates of carbon accumulated were high in the copper (6.03 %) and copper:Zinc (5.80 %) treatments but low in the nickel and zinc (4.93 % and 5.02 % respectively). The rates of Nitrogen mineralization were 0.41 and 0.44 % in samples treated with copper and copper:zinc compared to 0.22 %–0.24 % obtained at the beginning of the experiments. Soil microbial biomass carbon declined from average value of 183.7–185.6 μg/g before treatment to as low as 100.8 and 124.6 μg/g in samples treated with copper:zinc and copper respectively.The rate of respiration of the soil microbial populations was equally inhibited by the metals. From an average rate of 2.51–2.56 μg of C/g respiration of the soil microbes declined to 0.98, 1.08 and 1.61 μg of C/g in the copper:zinc, copper and zinc treated soils by the end of the experiment. The results suggest additive or synergistic effects of the metals.     

Efficiency of compost in the removal of heavy metals from the industrial wastewater

Authorities have been applying very strict regulations for the treatment of industrial wastewater recently because of the threatening level of the environmental pollution faced. Industrial wastewater containing heavy metals is a threat to the public health because of the accumulation of the heavy metals in the aquatic life which is transferred to human bodies through the food chain. Therefore, recently, researchers have been oriented toward the practical use of adsorbents for the treatment of wastewater polluted by heavy metals. The aim of this research was to determine the retention capacity of compost for copper, zinc, nickel and chromium. For this purpose, experiments in batch-mixing reactors with initial metal concentrations ranging from 100 to 1,000 mg/l were carried. It was also observed that compost could repeatedly be used in metal sorption processes. The experiments conducted indicated that compost has high retention capacities for copper, zinc and nickel, but not for chromium. Thus, compost has been approved as a potential sorbent for copper, zinc and nickel and may find place in industrial applications. Thus, solid waste which is another source of significant environmental pollution will be reduced by being converted into a beneficial product compost.     

含单裂隙非饱和带中轻非水相流体修复的数值模拟

针对非饱和带中油类污染物时空分布的研究,室内实验很难定量分析运移机理,野外检测成本高且破坏地层。数值模拟法作为一种应用广且成熟的方法,可以用来分析油类污染物在非饱和带中的运移规律。为了研究单井抽提及原位冲洗修复时,含单裂隙非饱和带中轻非水相流体（Light non-aqueous phase liquids,LNAPL）的时空变化规律,建立了数值模型,分析不同条件下LNAPL的修复效果及时空变化规律。模拟结果发现,LNAPL注入时优先流入裂隙,停止注入时优先流出裂隙。单井抽提修复模拟表明,抽提流量越大,修复效率越高。原位冲洗技术能有效补充地下水,防止产生新的环境问题;注水井起到“冲洗”及稀释污染物的作用,模拟最优方案修复面积达到96%,修复率达到75%,LNAPL饱和度控制在约0.05;对比分析发现,注水井布设在污染物范围的上边界时修复效果最好,能有效“冲洗”污染物并携带至抽提井中抽出地表。该研究为受轻油污染的土壤及地下水修复提供了科学的理论依据及有效的评估方法。     

Technical Challenges to In-situ Remediation of Polluted Sites

Throughout the world, subsurface contamination has become a widespread and pervasive problem. Toxic chemicals such as heavy metals and organic compounds are commonly used in a myriad of industries. However, largely through inadvertent or accidental release, these chemicals are presently polluting sites across the United States. In order to protect public health and the environment, further pollution must be prevented and sites with existing contamination urgently need remediation. Unfortunately, remediating subsurface contamination has proved to be a daunting task. Heavy metals and organic compounds often coexist and their distribution within the subsurface is highly dependent on particle and macro-scale heterogeneities. Vast resources have been invested to develop efficient remediation technologies, yet very few of these technologies have been successful. In-situ remediation is often preferred due to minimal site disturbance, safety, simplicity, and cost-effectiveness. The effectiveness of in-situ remediation technologies depends largely on the contaminant chemistry and subsurface heterogeneities (including particle-scale heterogeneities such as fine-grained soils, soils with reactive minerals, and/or soils rich in organic matter as well as macro-scale heterogeneities such as irregular soil layers and/or lenses). Under such heterogeneous conditions, integrated electrokinetic remediation technology has great potential. As a safe and economical remedial option for so many contaminated sites, the application of integrated electrokinetic remediation offers enormous public health, environmental, and financial benefits.     

考虑温度电动淋洗法去除污染软土中铬试验研究

针对铬污染软土,自行设计了电动淋洗试验装置,开展了铬污染软土室内土柱淋洗试验,分析了试验过程中电流、电解质溶液pH的变化以及淋洗液种类、外加电压、温度对重金属铬去除特性的影响。结果表明:电动淋洗试验可以有效去除土壤中的重金属铬;相对于单一淋洗试验,用10 V电压强化淋洗试验显著提高了重金属铬去除效果,淋洗液为十二烷基苯磺酸钠（SDS）时Cr（VI）和Cr（总）去除效率是单一淋洗法的2.79,3.12倍。当电压为10 V,温度升高至45 ℃时,淋洗液为柠檬酸（CA）和草酸（OA）的各组试验表明Cr（Ⅵ）与Cr（总）去除率均相应提高;而淋洗液为十二烷基苯磺酸钠时的试验组中Cr（VI）去除率提高了5.84%,Cr（总）去除率降低了4.25%,表明升高温度使部分Cr（VI）还原成不易迁移的Cr（III）;淋洗液为草酸的试验组中升高温度时Cr（Ⅵ）与Cr（总）去除率最高,分别达到了82.08%、77.57%,分别相应提高了27.65%、26.01%。电动淋洗试验后,铬污染软土土粒结构变得更紧密,土粒之间的孔隙减小且被填充的更加密实。     

The retention of heavy metals in sewage sludge applied to a freshwater tidal wetland

The hypothesis that freshwater tidal wetlands act as sinks for heavy metals was tested using sewage sludge applied biweekly from March to October 1981 at low treatment (25 g m^?2 wk^?1) and high treatment (100 g m^?1) levels. No differences in aboveground macrophyte standing crop were found except in June when high and low treatment sites had significantly higher (p=0.05) standing crops than control sites. Except for chromium, metal standing stocks in the vegetation on treatment sites did not increase as a result of sludge application. The March litter had significantly higher (p=0.05) concentrations of chromium, copper, lead, and nickel at all sites than the October vegetation, but only high and low treatment litter chromium levels were significantly higher (p=0.05) than control litter. When sludge application terminated in October, the top 5 cm of soil at the high and low treatment sites had retained, respectively, 47 and 43% of the cadmium, 53 and 28% of the chromium, 52 and 0% of the copper, 51 and 0% of the zinc, 31 and 0% of the lead, and 0 and 0% of the nickel applied; only cadmium (15 and 46%, respectively) and chromium (12 and 28%, respectively) were still retained the following March. Thus, freshwater tidal wetlands can retain significant quantities of heavy metals associated with sewage sludge. The vegetation and litter play minor roles while the soil plays a major role in heavy metal retention.     

Effect of electrode configuration on pH distribution and heavy metal ions migration during soil electrokinetic remediation

Generation, migration, and distribution of H⁺ and OH^? have remarkable influence on heavy metal removal from soil during electrokinetic remediation. A series of experiments were carried out to investigate the effects of electrode configuration and voltage on pH distribution and heavy metal migration, based on the preliminary exploratory experiments. In the first phase, three soil samples were used to observe the effect of electrode configuration on pH distribution. Then, three more soil samples were used to explore the effect of voltage on ion migration. Finally, three other soil samples were used to explore the effect of electrode configuration (i.e. angle CAC) on pH distribution and heavy metal migration. The results showed that the soil was divided into acid, base, and pH-jump zones and that heavy metals migrated under low pH conditions and were deposited at the pH-jump zone. Heavy metal distribution was fairly consistent with pH distribution. Under the optimal condition of $ \angle $ CAC 60º and voltage 2.33 V/cm, 4.22 mg copper and 0.51 mg zinc migrated from acid zone and deposited in pH-jump zone with 6.44 kJ energy consumption.