Heavy Metal Contamination in Farmland Soil and Bioremediation Measures: A Case Study of the Mining Area in Shaoguan

With the rapid development of mining,the soil heavy metal contamination is increasingly serious in Shaoguan,directly affecting the production of crops. This paper analyzes the farmland soil heavy metal contamination in the mining area of Shaoguan and the causes of heavy metal contamination in recent years,brings forward the bioremediation measures to control soil heavy metal contamination,and points out the development direction of bioremediation in farmland soil heavy metal contamination in the mining area.

Effect of Heavy Metal Contamination on Soil Enzymes Activities

Several enzymes catalyze much of the processes that exist in the soil. Enzymes in polluted soils are usually less active due to their exposure to heavy metals. The main goal of this study was to see how bioavailable types of Cd affected the behavior of catalase, urease, and dehydrogenases, as well as to compare the findings from naturally and artificially polluted samples. An experiment was conducted on two types of farmland (garden) soil: natural soil and soil that had been chemically polluted with Cd. The total content of heavy metal graded these soils as very highly polluted with Cd. The experiment was repeated four times to test the effects of increasing concentration and days (time). Extracellular enzymes from farmland performed enzymatic activity tests that lasted 6 to 29 days after soil sampling. After 0, 5, 10, 20, 30, and 45 days of incubation, soil samples were taken for testing respectively. However, even though no nutrient was added, dehydrogenase and urease activity increased as Cd concentration increased from 0 to 5 mg/L as the days passed. This is a result of enzymes engaging in respiratory and other living activities because of the low cadmium concentration and respiratory soil properties. However, there were significant variations in enzyme activity between naturally polluted and artificially contaminated soils. Dehydrogenases, Urease, and Catalase all showed a common pattern of enzyme sensitivity, which could be ordered as Dehydrogenase > Urease > Catalase. Dehydrogenase enzyme activity has been discovered to be more Cd resistant.

Effects of Heavy Metal Contamination on Microbial Biomass and Community Structure in Soils

Zinc smelting near Magu Town, Hezhang County, Guizhou Province, resulted in vegetation destruction and the accumulation of heavy metals, to varying extent, in adjacent soils, where up to 162.2- 877.9 mg·kg -1 Zn, 37.24- 305.6 mg·kg -1 Pb, and 0.50- 16.43 mg·kg -1 Cd, were detected. These values greatly exceed the background levels of these elements in soils. The concentrations of heavy metals (particularly Pb, Zn) were positively correlated with the contents of Fe 2O 3 and Al 2O 3 in the soils, showing that Fe and Al oxides play an important role in retaining heavy metals. Chemical fractionation indicates that Pb and Zn were associated mainly with Fe and Mn oxides and minerals, whereas Cd was dominated by exchangeable form. Microbial biomass in the soils was relatively low, in the range of 57.00- 388.0μg C·g -1, and was negatively correlated with heavy metal concentrations in the soils. The correlation coefficient of microbial biomass C to Zn concentrations in the soils was as high as -0.778 (p< 0.01), indicating that the heavy metal contamination has toxic effects on microorganisms in soil. The results of Biolog measurements demonstrated that there were no significant changes in microbial community structure in the heavy metal contaminated soils. Gene fragments were similar to one another after the DNA was extracted from soil microbes and experienced PCR (polymerase chain reaction) and DGGE (denaturing gradient gel electrophoresis) reactions. These results indicated that light heavy-metal pollution may not result in any change in soil microbial community structure.

Analysis and Assessment on the Heavy Metals in a Severely Degraded Subtropical Red Soil Region

5 different forests of Pinus massoniana, Schima superba, Liquidambar formosana, P. massoniana × S. superba, P. massoniana × L. formosana as the research object were set up to study the Cr, Cu and Zn content of degraded red soil region in subtropics. The soil heavy metal pollution degree was evaluated by national environmental quality standard (II class). The results showed that three soil metals of P. massoniana × S. superba were the highest, and the soil metals enrichment ability was strong. The order of single factor pollution index of metal elements was Cu (1.38) > Cr (0.81) > Zn (0.42), and moderately pollution, pollution warning and no pollution, respectively. There was no significant correlation between three soil heavy metals and soil total carbon (TC), total nitrogen (TN) and total phosphorus (TP). These results suggested that the accumulation of heavy metal elements was not derived from the parent material of soil. There was a significant positive correlation between the three metal elements which indicated that the sources of the three elements were similar. The structural equation model showed that the direct and indirect effects among the influencing factors ultimately affected the activity of heavy metals by cascade effects.

Soil Heavy Metal Pollution Evaluation around Mine Area with Traditional and Ecological Assessment Methods

As a widespread problem, heavy metals contamination in soil has drawn considerable study interest, especially for the farmlands around mine area. A variety of pollution evaluation methods have been compared including both traditional physical and chemical analysis methods as well as ecological assessment methods. And the combination of multiple assessment methods was recommended to get a comprehensive and through soil heavy metal pollution evaluation.

Evaluation on Ecological Risks of Soil Heavy Metals in a Certain Area of Sichuan by Improved Fuzzy Mathematics Method

Taking a certain area in Sichuan Province as the object of this study, this paper adopts fuzzy mathematics method to make an evaluation on ecological risks of heavy metal in soil of this area. On calculation of factors’ weights, the traditional method of giving weight according to pollutants’ concentrations fails to consider the toxicity of heavy metals, and can’t reflect their actual ecological effect. With reference to the toxicity coefficient in potential ecological risk index evaluation, this article revises the traditional fuzzy mathematics evaluation model and puts forward a new method to calculate factors’ weight by incorporating toxicity levels in weight setting. The results of this study indicate: surface soil of this area was good in general, with 91.2% samples belonging to the first level, 7.77% samples belonging to the second level, and only 1.03% belonging to the third level. Compared with the results of the evaluation method of the reality content of soil, soil quality is better than the results of the quantitative evaluation, and is closer to the actual local conditions.

An Assessment of Heavy-Metal Contamination in Soils within Auto-Mechanic Workshops Using Enrichment and Contamination Factors with Geoaccumulation Indexes

Soil characterization and heavy metals in different layers (0 - 15 cm;15 - 30 cm and 30 - 45 cm depth) of automobile mechanic waste dumps were studied. The soils showed remarkably high levels of all the metals above background concentrations with most (Ni, Cu, Fe, Cr and Cd) decreasing with soil depth. The distribution pattern were in the following order Fe > Cu > Zn > Pb > Cr > Ni > Cd. Across all the sampling locations and profiles, Fe and Cd showed the highest (476.4 μg·g-1) and least (37.5 μg·g-1) mean concentrations respectively. Pollution load index (PLI) and index of geoaccumulation (Igeo) revealed overall high and moderate contamination respectively but the enrichment factors (EFs) for Pb Ni and Cd are severe. The inter-element relationship revealed the identical source of elements in the soils of the studied area. The accuracy of the results has been cheeked using the standard reference material;SRM (PACS-2). The mechanic waste dumps represent potential sources of heavy metal pollution to environment. The elevated levels of heavy metals in these soil profiles constitute a serious threat to both surface and groundwater.

Evaluation on Heavy Metal Content in Soil of Rural Landfill in Chongqing

To understand heavy metal content in soil of rural landfill in Chongqing, samples were collected at 10 sampling sites of different counties. Zn, Cr, Cu, Cd and Pb contents were analyzed, and their pollution degrees were evaluated by single-factor evaluation and index of geoaccumulation. Results displayed that there was no Cr pollution in soil of rural landfill in Chongqing, but Cd pollution was very serious. Pb, Zn and Cu showed spatial difference in different counties. Dispersion degrees of Zn and Pb pollution were lower, and their pollution degrees were also relatively lower. Dispersion degree of Cu pollution was higher, and its pollution degree was also relatively higher.

Review of Soil Environmental Contamination Caused by Heavy Metals from Electronic Wastes

The reports about soil environmental contamination from heavy metals in electronic wastes were reviewed. The production, sources and disposition of electronic wastes were introduced. The negative impacts of electronic wastes on the environment were analyzed, and soil pollution from electronic wastes in several typical districts were discussed and summarized.

Evaluation on Potential Ecological Risk of Heavy Metals in Soil from Penglai Fairyland Park

This study aims at evaluating the heavy metals pollution in soil collected from Penglai Fairyland Park in Guiyang,and predicting the harm of heavy metals to human health. Based on the background value of soil in Guizhou and Soil Environment Quality Standard( GB15618-1995),by using the geoaccumulation index method and Hakanson potential ecological risk assessment method,we research pollution characteristics and ecological risk of heavy metals in soil from the study area. The results show that from the index of geoaccumulation,the pollution level of heavy metals in agricultural soil from Penglai Fairyland Park is in the order of Ni > Cu > Hg > Cd > As > Zn > Cr > Pb. From the potential ecological harm index evaluation,soil is at slight ecological risk level in the park and the potential ecological hazard degree is in the order of Hg > Cd > Ni > As > Cu > Cr > Pb > Zn. The soil ecological environment in research area is only mildly damaged. Thus,the soil in research area is at the level of security,and it is suitable for cultivation of crops and less harmful to human health.

Removal of heavy metals from a contaminated soilusing tartaric acid

This study reports the feasibility of remediation of a heavy metal （HM） contaminated soil using tartaric acid, an environmentally-friendly extractant. Batch experiments were performed to test the factors influencing remediation of the HM contaminated soil. An empirical model was employed to describe the kinetics of riM dissolution/desorption and to predict equilibrium concentrations of HMs in soil leachate. The changes of HMs in different fractions before and after tartaric acid treatment were also investigated. Tartaric acid solution containing HMs was regenerated by chestnut shells. Results show that utilization of tartaric acid was effective for removal of riMs from the contaminated soil, attaining 50%-60% of Cd, 40%-50% of Pb, 40%-50% of Cu and 20%-30% of Zn in the pH range of 3.5-4.0 within 24 h. Mass transfer coefficients for cadmium （Cd） and lead （Pb） were much higher than those for copper （Cu） and zinc （Zn）. Sequential fractionations of treated and untreated soil samples showed that tartaric acid was effective in removing the exchangeable, carbonate fractions of Cd, Zn and Cu from the contaminated soil. The contents of Pb and Cu in Fe-Mn oxide fraciton were also significantly decreased by tartaric acid treatment. One hundred milliliters of tartaric acid solution containing HMs could be regenerated by 10 g chestnut shells in a batch reactor. Such a remediation procedure indicated that tartaric acid is a promising agent for remediation of HM contaminated soils. However, further research is needed before the method can be practically used for in situ remediation of contaminated sites.

Heavy metals contamination characteristics in soil of different mining activity zones

Depending upon the polluted features of various mining activities in a typical nonferrous metal mine,the contaminated soil area was divided into four zones which were polluted by tailings,mine drainage,dust deposition in wind and spreading minerals during vehicle transportation,respectively.In each zone,soil samples were collected.Total 28 soil samples were dug and analyzed by ICP-AES and other relevant methods.The results indicate that the average contents of Zn,Pb,Cd,Cu and As in soils are 508.6,384.8,7.53,356 and 44.6 mg/kg,respectively.But the contents of heavy metals in different zone have distinct differences.The proportion of oxidizing association with organic substance is small.Difference of the association of heavy metals is small in different polluted zones.

A Comparative Analysis of Environmental Quality Assessment Methods for Heavy Metal-Contaminated Soils

Four assessment methods(two pollution indexes and two fuzzy mathematical models) were employed to investigate the environmental quality of four soils around a ferroalloy plant in Nanjing City.Environmental quality was assessed as class IV(moderately polluted) for each soil with single-factor index method,and was identified to be classes IV,III(slightly polluted),III,and III for soils A,B,C,and D,respectively,with the comprehensive index model.In comparison with the single-factor index method,the comprehensive index model concerned both dominant parameter and average contribution of all factors to the integrated environmental quality.Using the two fuzzy mathematical methods(single-factor deciding and weighted average models),the environmental risks were determined to be classes IV,III,II(clean),and II for soils A,B,C,and D,respectively.However,divergence of the membership degree to each pollution class still occurred between the two methods.In fuzzy mathematical methods,membership functions were used to describe the limits between different pollution degrees,and different weights were allocated for the factors according to pollution contribution.Introduction of membership degree and weight of each factor to fuzzy mathematical models made the methods more reasonable in the field of environmental risk assessment.

Investigation and Analysis of Soil Pollution of Heavy Metals(Hg,As) in Duanzhou District,Zhaoqing City

The soil heavy metals(Hg and As)in Duanzhou District of Zhaoqing City were determined by AFS200 T atomic fluorescence spectropho-tometer,and the soil environment in Duanzhou District was evaluated by several evaluation methods of soil heavy metal pollution,such as single factor index method,pollution load index method and Nemerow comprehensive pollution index method.Finally,according to the data and conclu-sions,the soil pollution situation in Duanzhou District of Zhaoqing was analyzed.The results will let more people pay attention to the changes of the environment and realize the harm of the environment,and the government can formulate a new plan conducive to the coordinated development of the environment and economy.

Potential of weed species applied to remediation of soils contaminated with heavy metals

To screen out a series of ideal plants that can effectively remedy contaminated soils by heavy metals is the main groundwork of phytoremediation engineering and the first step of its commercial application on a large scale. In this study, accumulation and endurance of 45 weed species in 16 families from an agricultural site were in situ examined by using the pot-culture field experiment, and the remediation potential of some weed species with high accumulation of heavy metals was assayed. The results showed that Solanum nigrum and Conyza canadensis can not only accumulate high concentration of Cd, but also strongly endure to single Cd and Cd-Pb-Cu-Zn combined pollution. Thus 2 weed species can be regarded as good hyperaccumulators for the remediation of Cd-contaminated soils. Although there were high Cd-accumulation in Artemigia selengensis, Znula britannica and Cephalanoplos setosum, their biomass was adversely affected due to action of heavy metals in the soils. If the problem of low endurance to heavy metals can be solved by a reinforcer, 3 weed species can be perhaps applied commercially.

Phytoremediation Mechanisms of Heavy Metal Contaminated Soils: A Review

Phytoremediation is a green emerging technology used to remove pollutants from environment components. Mechanisms used to remediate soils contaminated by heavy metal are: phytoextraction, phytostabilisation, phytovolatilization and rhizofiltration. The two first mechanisms are the most reliable. Many factors influence the choice of the suitable phytoremediation strategy for soil decontamination. It depends on soil properties, heavy metal levels and characteristics, plant species and climatic conditions. The present review discusses factors affecting heavy metals uptake by plant species, the different phytoremediation strategies of heavy metal contaminated soils and the advantages and disadvantages of phytoremediation and each of its mechanisms.

Phytoremediation Potential of Sorghum as a Biofuel Crop and the Enhancement Effects with Microbe Inoculation in Heavy Metal Contaminated Soil

Phytoremediation is an eco-friendly and low-cost biotechnology using plants to extract, contain, degrade, or immobilize pollutants from the contaminated environment. Selection of the ideal plant species and suitable enhancing measures to obtain high remediation efficiency and large valuable biomass are essential requirement for a successful phytoremdaition. Sorghum (Sorghum bicolor L.) is one of the most attractive bioenergy crops for producing biofuels with high biomass production. In this study, the phytoremediation potential of sorghum to heavy metals and the promotion effects by a lead-tolerant fungus (LTF) were investigated using a multiple heavy metal contaminated soil with Pb, Ni, and Cu. The results showed that the sorghum survived the heavy contamination, and LTF inoculation promoted the plant growth and increased the phytoextraction yields of Pb, Ni, and Cu. The phytoextraction potential (μg/plant) of the whole sorghum for Sorghum were 410 (Pb), 74 (Ni), and 73 (Cu), and for Sorghum with LTF inoculation were 590 (Pb), 120 (Ni), and 93 (Cu), respectively. The results suggested that sorghum would be one of the ideal candidates for phytoremediation of contaminated soil because of its high phytoremediation potential, large biomass production, and utilization in biofuel production.

Heavy Metal Pollution of Topsoil in the Vicinity of an Industrial Estate Co-Located with a Housing Estate in Southwestern Nigeria

Heavy metals were determined in topsoils around a major industrial estate co-located with a housing estate in the southwestern region of Nigerian. Samples were collected on three-monthly basis for 18 months, from the industrial waste dumpsites, industrial area, residential area, around an effluent channel, outskirts of the estate and control sites. Average levels of Cu (2850 ± 3340 mg/kg), Pb (768 ± 450 mg/kg) and Ni (105 ± 30 mg/kg) at the dumpsites were significantly higher than other locations. At the industrial area and effluent channels, Pb and Cr levels were slightly elevated compared with other metals. Metal levels at the residential area and outskirts of the estate were about the levels in the control. Generally, the degree of contamination within the vicinity of the estate was of the order Cu>Pb>Ni>Cd>Co>Cr. Average total bioavailable (non-residual) fraction of the metals consisted of 52.0% of the metal load, with this fraction for Cd and Pb being 73.9% and 60.7% respectively. Topsoils around the dumpsite were evidently polluted with high levels of copper and lead. Seepage of leachate from the dumpsite has the potential of contaminating ground water reserves. Improper disposal of industrial solid wastes appears to be the likely source of metal pollution in the industrial estate. Heavy metal pollution in the estate can therefore be significantly reduced by prompt and proper disposal of generated solid wastes, and the application of particulate scrubbers in the industries.