Hakanson Potential Ecological Risk Index Research Articles

Heavy metals pollution and potential ecological risk assessment in farmland soils from typical mining area: a case study

ABSTRACT The research aimed to investigate HMS, utilizing the Pearson correlation coefficient for speciation distribution analysis, PCA for assessing pollution characteristics and identifying sources, the Muller index to evaluate ecological risk level, and the Hakanson potential ecological risk index to determine the order of risk from heavy metals. The topsoil near SA was collected, and the contents of seven kinds of HMS, As, Cd, Pb, Zn, Ni, Cu and Cr were determined, so as to evaluate the types of high-risk heavy metal pollution further accurately. The research recorded valuable data showing that the concentration values of all seven HMS in the investigated area exceeded prescribed agricultural soil contamination limits. The concentrations of As, Cd, and Pb were found to be 8.30, 46.20, and 6.08 times higher than the screening values in Hunan Province, respectively. In the GYB sampling area, the coefficient of variation (CV) values for Cu, Pb, As, Zn, and Cd are all between 0.50 and 1.00. Notably, the CV value for Cd reaches 0.82, indicating a significant variation. Significant correlations were found between Cd and Zn (Cd-Zn), Pb and Zn (Pb-Zn), Ni and Cr (Ni-Cr) in the tested soils. The ecological risk index () results showed that Cd was the primary pollutant in the study area, with the potential ecological hazards in the tested soils ranked as Cd>As>Pb>Cu>Zn>Ni>Cr. Combining both evaluation methods, the study area’s potential ecological risk order is SZY>GYB>CTL.

Pollution Risk and Contribution Analysis of Pb, Cd, and As in Soils and Crops Under Different Land Use Types in Longyan City

A total of 174 soil samples and 87 grain samples were collected in two typical fields in Longyan City. The pollution index method, Hakanson potential ecological risk index method, and EPA human exposure risk assessment model were used to evaluate the pollution status, ecological risk, and health risks of heavy metals Pb, Cd, and As in soil of different land use types. The contributions of Pb, Cd, and As to soil and crop pollution risk were also analyzed. The results indicated that the pollution levels of Pb, Cd, and As in soils and crops of different utilization types in regionⅠwere low. Cd was the main soil pollutant and ecological risk factor, contributing 55.3% to comprehensive soil pollution and 60.2% to comprehensive potential ecological risk, respectively. The pollution levels of Pb, Cd, and As in soils and crops in regionⅡwere high. Pb and Cd were the main soil pollutants and ecological risk factors, contributing 44.2% and 51.6% to comprehensive pollution and 23.7% and 67.3% to comprehensive potential ecological risk, respectively. Pb was the main pollution factor of crops, contributing 60.6% and 51.7% to the comprehensive pollution of coix and rice, respectively. The carcinogenic risks of Cd and As in soil of the two typical regions for adults and children were all within the acceptable range under the oral-soil exposure pathway. The contribution of Pb, Cd, and As to the total non-carcinogenic risk in regionⅠwas Pb (68.1%)>As (30.5%)>Cd (1.38%). There was no carcinogenic risk of Pb in rice in the two typical regions under the oral-rice intake pathway. The contribution of Cd and As to carcinogenic risk in adults and children were As (76.8%)>Cd (22.7%) and Cd (69.1%)>As (30.3%), respectively. Three pollutants in regionⅠand Ⅱ had high non-carcinogenic risk, and As was the most significant contributor (84.0% and 52.0%, respectively), followed by Cd and Pb.

Spatial Distribution Characteristics and Potential Risk Assessment of Heavy Metals in Sludge of Shanghai Sewage Treatment Plant: A Case Study

Sewage treatment is an important indicator of the urban environment and an important method of sustainable development. In this paper, the spatial distribution characteristics of 8 heavy metals in sewage sludge from 44 sewage treatment plants in Shanghai were analyzed. The pollution degree and potential ecological risk of heavy metals in sludge were evaluated by the Nemerow comprehensive pollution index and Hakanson potential ecological risk index. First, the single factor pollution index of heavy metals was ranked. The Nemerow comprehensive pollution index showed that five sewage treatment plants in Nanxiang, Dongqu, Liantang, Songjiang west, and Xinhe were heavily polluted. Second, the single factor potential ecological risk index of each heavy metal was analyzed. Finally, it is concluded that in the monitoring and control of sewage treatment, Shanghai should pay attention to the sewage treatment plants with high potential ecological risks and gain an excellent performance in the reduction in the emissions of pollution sources, so as to improve environmental quality and reduce the potential ecological risks. This paper provides the basis for studying the characteristics of heavy metal pollution of sewage sludge.

Response of macrofaunal assemblages to different pollution pressures of two types of ports

Pollution status and benthic ecological quality of the two types of ports were assessed based on heavy metals and macrofaunal assemblages. Macrofaunal abundance and biomass in the industrial port were significantly higher than those in the fishing port. The dominant species of the two ports were Echinocardium cordatum and Nephtys oligobranchia. The AZTI marine biotic index (AMBI), multivariate AMBI, and Shannon-Wiener diversity index demonstrated that the benthic ecological quality of the two ports was moderate to good. The benthic ecological quality of the distant port sites was better than those of the nearby port sites. The geoaccumulation index and the Hakanson potential ecological risk index indicated that mercury posed a serious threat to port sediment pollution. AMBI, multivariate AMBI, and Shannon-Wiener diversity index were not good indicators for heavy metal pollution. The dominant species and Pielou’s evenness index were significantly correlated with heavy metal pollution and were good biological indicators.

Ecological risk assessment based on soil adsorption capacity for heavy metals in Taihu basin, China

Due to the toxicity, bioaccumulation, non-biodegradability and perseverance of heavy metals, their risk assessment is essential for soil quality management. The Hakanson potential ecological risk index (RI), which considers the effects of heavy metal concentration and toxicity, has been widely used in soil ecological risk assessment. However, RI overlooks the influence of soil properties on the mobility and availability of heavy metals in risk assessment. To fill this gap, this study sought to develop an improved ecological risk index (IRI), which incorporates soil adsorption into RI, and applied it to evaluate the ecological risk of heavy metals in the soil of the Taihu basin, China. The soil adsorption models based on the Gradient Boosting Decision Tree (GBDT) was used to predict the soil adsorption capacity of five heavy metals (i.e. cadmium, chromium, copper, lead, zinc). The soil adsorption capacity in 1446 sites in the Taihu basin was predicted by the GBDT models and was assigned as the weight of IRI. The risk assessment results of the five metals in the Taihu basin showed that 40% of the sites were at a moderate risk level and 60% of the sites were at a slight risk level based on the RI. The value of IRI in the basin ranged from 11.1 to 75.5, with a mean value of 28.1. IRI differed from RI in spatial distribution due to the influence of soil adsorption. The comparative analysis between the metal contents in sediments and surrounding soils confirmed the tremendous influence of soil adsorption on ecological risks, indicating that soil adsorption should be taken into consideration in soil risk assessment.

Variation Feature, Pollution Risk Assessment, and Source Analysis of Heavy Metals in Lanzhou City, Northwestern China

Lanzhou is located in the northwest of China and is famous for its petrochemical and heavy industries of China. The city has suffered long-term pollution of heavy metals in recent years. Significant efforts, such as tax subsidies for new energy vehicles and treating solid waste, have been launched by the Lanzhou municipal government to address the pollution of heavy metals since 2010. What is the current status of heavy metal pollution in Lanzhou? In this study, the concentrations of 12 heavy metals (V, Cr, Mn, Co, Ni, Cu, Zn, As, Mo, Cd, Sb, and Pb) were tested from 20 sediment samples. Mn, Zn, V, and Cr are the predominant heavy metals, with mean concentrations of 534.65, 65.85, 56.29, and 36.05 mg/kg; Ni, Cu, Pb, Co, and As are in moderate amounts, with mean concentrations of 25.2, 21.5, 16.7, 9.87, and 4.86 mg/kg; Mo and Cd have the lowest mean concentrations of 0.54 and 0.15 mg/kg. A low ecological risk is confirmed by two indices, the Hakanson potential ecological risk index ( R I ) and the geoaccumulation index ( I geo ). The R I index has lower E i r values (<40) and R I values (<150), which range from 18.11 to 37.95, with an average value of 25.61. Co, V, Cd, Cu, Zn, As, Cr, Ni, Pb, and Mn metals are classified as an uncontaminated environment (level 0) and a moderately to heavily contaminated environment (level 2-level 3) by I geo values. Seven heavy metals (Pb, Cd, Cr, As, Cu, Zn, and Ni) in Lanzhou are the relatively lowest amount in the 5 cities in China. The changing trends of heavy metal concentrations firstly increase and then decrease gradually from 2005 to 2022. The time turning point of concentration shrinking occurred in approximately 2014, which is in response to the increased efforts of addressing the pollution launched by the Lanzhou municipal government since 2010. Source analysis by Pearson’s correlation and principal component analysis revealed that the accumulation of Mo metal was caused by the enrichment of MnO2 in the oxidic condition; the accumulations of Cu, Co, Ni, Mn, Cr, Zn, Cd, and Pb metals are influenced by natural sources and human activities (vehicle exhaust and industrial pollution), respectively.

Characteristics and Assessment of Soil Heavy Metals Pollution in the Xiaohe River Irrigation Area of the Loess Plateau, China

Heavy metals in soil are a potential threat to ecosystems and human well−being. Understanding the characteristics of soil heavy metal pollution and the prediction of ecological risk are crucial for regional eco−environment and agricultural development, especially for irrigation areas. In this study, the Xiaohe River Irrigation Area in the Loess Plateau was taken as the study area, and the concentration, as well as their accumulation degree and ecological risk and distribution of soil heavy metals, were explored based on the geo−accumulation index (Igeo) and Hakanson potential ecological risk index methods. The results showed that the concentrations of soil heavy metals were all lower than the second grade Environmental Quality Standard for Soils of China. However, the average concentrations of Cu, Hg, Cd, Pb, Zn, Ni and As were higher than the above−mentioned standard. Compared with the soil background values of Shanxi Province, eight heavy metals of all samples presented different accumulation degrees, with the highest accumulation degree in Hg, followed by Cd, and the values were 11.3 and 4.0 times more than the background value, respectively. Spatially, the distribution of soil heavy metals in the Xiaohe River irrigation area was quite different, generating diverse pollution patterns with significant regional differences and complex transportation routes. The content of soil heavy metals in the Xiaohe River irrigation area was highly affected by land use types. The pollution degree varied with the distance to an urban area, declining from the urban area to suburban farmland, and the outer suburban farmland. Among these heavy metals, Hg and Cd were the principal contamination elements, and transportation, service industry and agricultural activities were the main potential contamination sources. The potential ecological risk of soil heavy metal positioned as follows: Hg > Cd > Pb > Zn > Cu > As > Ni > Cr. As indicated by the Hakanson potential ecological risk index strategies, except for the Wangwu examining site, the other six sampling sites experienced extremely strong risks, and as a whole, the entire study region was in a condition of incredibly impressive perils. Consequently, these results suggest that improving soil environmental investigation and assessment, setting up soil heavy metal contamination prevention and control innovation framework and reinforcing contamination source control are effective approaches for soil heavy metal contamination anticipation and control in irrigated areas of the Loess Plateau.

Synthetic Evaluation on the Potential Ecological Risks of Heavy Metal Pollution in Sediments in the Sea near Bohe Port of Maoming

The pollution index method and Hakanson potential ecological risk index method were used to study and analyze the pollution factors (Hg, Cu, Pb, Zn, Cd, As, Cr) in surface sediments of the sea near Bohe Port of Maoming. The results show that the overall contamination level and potential ecological risk of typical pollutants are at the low level in this sea area. The sequence of the pollution degree of heavy metals in surface sediments is As> Cr >Zn> Hg>Cu>Pb>Cd; and the potential ecological risk sequence is Hg>As>Cd>Cu>Pb>Cr >Zn. Hg is the major factor of potential ecological risk in surface sediments of this sea area.

Distribution and Ecologica Risk of Sediment Heavy Metals in the Water-Level-Fluctuation Zone of the Shawan River Section of Yelang Lake

With the aim of revealing the potential ecological risk and distribution characteristics of heavy metals on the surface sediment at the Shawan River section of Yelang Lake, the following three analyses were first performed: (1) analysis of grain-size composition on sediment samples collected at seven different sites in the water-level-fluctuation zone (WLFZ); (2) analysis of bulk sediment content of six heavy metals, namely, Cd, Cr, Pb, Mn, Zn, and Cu; and (3) the correlation analysis of grain-size composition and heavy metal content in the sediment. Afterwards, the approach of Hakanson potential ecological risk index was employed to analyze the risk of heavy metal pollution in sediments of seven WLFZ plots. The outcomes indicate that (1) the mean sediment grain size at each sampling site was generally >0.063 mm, with gravel grains (>1 mm) and sand grains (0.22–1 mm) accounting for the largest proportions; (2) the site-averaged mean sediment content of each of the six heavy metals was significantly higher than their respective geochemical background contents in the sediment of Guizhou Province, and the grain-size dependence of the bulk sediment content of heavy metals was not significant; (3) the distribution of Cr was relatively independent of other metals, which was in contrast to notable positive correlations observed between other metals; and (4) in accordance with the approach of Hakanson potential ecological risk index, for these heavy metals, their potential ecological risk reduced by the order of Zn < Cr < Cu < Pb < Cd, with Cd having a mean potential risk index (Ei) of 566.13, suggestive of a very high level of potential ecological risk, Zn, Cr, and Cu having a mild potential ecological risk, and Pb having moderate potential ecological risk. Cd largely contributes to the comprehensive ecological risk index RI is the largest, thereby having important environmental implications.

Probabilistic-fuzzy risk assessment and source analysis of heavy metals in soil considering uncertainty: A case study of Jinling Reservoir in China

Considering the uncertainty caused by the random error of the sample measurement, the heterogeneity of spatial and temporal distribution of pollutants, and the traditional method of selecting a single parameter for evaluation, based on fuzzy theory, Hakanson potential ecological risk index (considering heavy metal enrichment, ecotoxicity and bioavailability) and United States Environmental Protection Agency health risk assessment system, the fuzzy ecological risk and health risk assessment methods for of heavy metals in soil were established. In the soil of the Jinling Reservoir area, Cd, which has high bioavailability, had the highest average contribution rate to RI, and thus was, regarded as a priority metal for ecological risk. Sites JL9 and JL11 were the priority areas. The heavy metals did not pose a clear hazard to human health, but children had a higher health risk. Pb and As were regarded as the priority metals for health risk. Fuzzy evaluation provided the risk interval and membership degree, contained more parameter information, quantified and reduced the uncertainty of parameters, provided more comprehensive results, and compensated for the deficiency of deterministic evaluation. As the main source of heavy metals, the intensity of agricultural activities in the study area must be controlled to avoid excessive input and accumulation of heavy metals, which may damage the ecological environment and endanger human health.

Geochemical Baseline Establishment and Source-Oriented Ecological Risk Assessment of Heavy Metals in Lime Concretion Black Soil from a Typical Agricultural Area.

To accurately assess the potential ecological risk posed by heavy metals in lime concretion black soil and quantify the risk contributions from different sources, an investigation of 217 surface soil samples and 56 subsoil samples was performed in the southern part of Suzhou City. Geochemical baseline values of soil heavy metals (Cr, Zn, Pb, Ni, Hg, Cu, Cd, As, Mn and Co) in the study area were calculated as 53.6, 61.5, 19.8, 27.6, 0.08, 18.4, 0.13, 12.9, 416.1 and 11.0 mg/kg, respectively, by using reference metal normalization and cumulative frequency curve methods. Subsequently, four potential sources of soil heavy metals were identified by the positive matrix factorization. Finally, the potential ecological risks arising from the identified sources were determined by the integrated model of positive matrix factorization and Hakanson potential ecological risk index. Results showed that the ecological risk posed by soil heavy metals in the study area ranged from low to moderate level. Hg and Cd were the two largest risk contributors, supplying 36.0% and 30.3% of total risk value. The origin of heavy metals in the soils is mostly related to four sources including agricultural activities, natural dispersion, coal consumption and traffic pollution. Source apportionment of the potential ecological risks revealed that the dominant risk source in the study area was natural dispersion (42.0%), followed by coal related industries (26.5%), agricultural activities (20.4%) and traffic pollution (11.1%). This work gives a clear baseline information of the heavy metal accumulations in lime concretion black soil and provides a successful case study for the source-oriented ecological risk assessment.

Distribution and Ecological Risk of Heavy Metals in the Soil of Redevelopment Industrial Sites

Fifty typical redevelopment industrial sites in the Putuo, Baoshan, Minhang, and Jiangding districts of Shanghai were chosen to evaluate the ecological risk of heavy metals in the soil. The contents of heavy metal (Hg, Cd, Pb, Cr, and As) in 1847 soil samples, taken from vertical sections, were determined, and their risks were evaluated using the Nemero composite index and Hakanson potential ecological risk index. The average contents of Hg, Cd, Pb, Cr, and As in topsoil samples were 0.33, 0.37, 74.55, 69.23, and 9.05 mg·kg-1, respectively. The contents of Hg, Cd, and Pb exceeded the soil background values of Shanghai, which were 2.75, 2.85, and 2.93 times the background values, respectively. The contents of five heavy metals in soil decreased gradually with increased depth. The contents of heavy metals in deep and saturated soils were close to, or below, the background values, indicating that the anthropic activity disturbance was mainly confined to the topsoil. The accumulation of Hg, Cd, and Pb was the most obvious in Putuo topsoil, with the average contents being 4.25, 4.85, and 3.09 times the background values, respectively. The average contents of Hg and Pb in Baoshan were 4.92 and 6.43 times the background values, respectively. The Nemero Composite Index of Baoshan and Putuo districts were 3.70 and 3.20, respectively, representing heavy pollution level at these sites. The Hakanson potential ecological risk indexes of the Putuo and Baoshang districts were 398.59 and 303.08, respectively, with considerable ecological risk levels. The content and ecological risk of heavy metals at the Minhang and Jiading sites were relatively low. In summary, the pollution of heavy metal in the redeveloped industrial sites is influenced by the operating time, industry type, and past management level of the enterprises. The heavy metal accumulation in the Putuo and Baoshan districts, whose industries developed earlier, were higher than those in the Minhang and Jiading districts. The pollution of heavy metal Hg, Cd, and Pb in soil should be a focus of future work.

Geochemical baseline determination and contamination of heavy metals in the urban topsoil of Fuxin City, China

Urban topsoil is the most frequent interface between human society and natural environment. The accumulation of heavy metals in the urban topsoil has a direct effect on residents’ life and health. The geochemical baseline of heavy metals is an objective description of the general level of heavy metals in the urban topsoil. Meanwhile, the determination of geochemical baseline is necessary for regional environmental management, especially in coal cities prone to heavy metal pollution. Heavy metal pollution has become an environmental problem in Fuxin City, China for a long time. To establish the geochemical baseline of heavy metals in the topsoil of Fuxin City and to evaluate the ecological risk of the topsoil, we collected 75 topsoil samples (0–20 cm) and analyzed the concentrations of Cu, Ni, Zn, Pb, Cr, Cd, Hg and As through X-ray fluorescence spectrometry, atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry. We determined the geochemical baseline of heavy metals in the topsoil of Fuxin City by using iteration removal, box-whisker plot, cumulative frequency curve and reference metal normalization; evaluated the contamination risk and ecological risk of the topsoil by using the baseline factor index, Nemerow index and Hakanson potential ecological risk index; and identified the source category of heavy metals in the topsoil by using a pedigree clustering heatmap. Results showed that the geochemical baseline values were 42.86, 89.34, 92.23, 60.55, 145.21, 0.09, 0.08 and 4.17 mg/kg for Cu, Ni, Zn, Pb, Cr, Cd, Hg and As, respectively. The results of Nemerow index and Hakanson potential ecological risk index indicated that the urban topsoil in the study area was slightly contaminated and suffering low potential ecological risk. The main contaminated areas dominated in the middle part and northeast part of the study area, especially in the western Haizhou Strip Mine. The result of baseline factor index indicated that Hg and Cd were the major pollution elements. Using a pedigree clustering heatmap, we divided the sources of these heavy metals into three types: type I for Ni and Cr, largely represented the enrichment of heavy metals from natural sources; type II for Cu, Pb, Zn, Cd and As, mainly represented the enrichment of heavy metals from anthropogenic sources; and type III for Hg, represented the form of both natural and anthropogenic inputs.

As-Hg Compound Pollution: Rice Growth, Yield, and Environmental Safety Limits

With rapid economic and industrial development, the potentially toxic element (PTE) pollution of farmlands in China has become increasingly serious. Based on the Hakanson potential ecological risk index (RI) and national food pollutant limit standards (GB 2762-2017), the effects of exogenous potentially toxic elements (PTEs), i.e., arsenic (As) and mercury (Hg), on rice growth were studied. Common varieties of hybrid (YY 538, CY 84) and conventional (XS 134, JH 218) rice were grown in pots having representative paddy soil from Zhejiang Province, China. The results showed that As and Hg in soil significantly inhibited growth; however, the plant height of hybrid rice was less affected. Further, there were significant correlations between concentrations of PTEs in soil and rice grains; however, hybrid rice had a stronger ability to absorb and accumulate PTEs. The comprehensive potential ecological RI of soil PTEs was 39.4–89.9, which is below the level of ‘minor ecological hazard’, and the contribution rate of Hg was 79.9%–84.2%; as such, Hg posed the greatest potential ecological risk in the study area. The ecological risk limits of As and Hg in the safe production of different rice varieties decreased in the order XS 134 > JH 218 > YY 538 > CY 84. The ecological risk limits of As and Hg for conventional rice were higher, and the risk limits of As and Hg for hybrid rice were lower, than the limit of the soil environmental quality assessment index in the national “Soil quality control criteria for soil pollution in agricultural land (for trial implementation) (Trial)” (GB15618-2018). The health risk limit of soil As in the typical paddy soil of China decreased in the order XS 134 > JH 218 > CY 84 > YY 538. The health risk limit of Hg decreased in the order XS 134 > JH 218 > YY 538 > CY 84. The health risk limit of As was lower, whereas the risk limit of Hg was higher, than the limit of the soil environmental quality evaluation index in the national “Soil quality control criteria for soil pollution in agricultural land (for trial implementation) (Trial)”(GB15618-2018).

Mapping and risk assessment of heavy metals in agricultural soils of the Siakh Darengoun Region, Shiraz, Iran

Four heavy metals were measured in forty-nine topsoil samples collected fromagricultural areas in Siakh-Darengoun, Iran. The goals were to investigate soil spatialdistribution patterns of metals; their potential ecological risk; and sources. The Hakansonpotential ecological risk index and index of geo-accumulation (Igeo) were used forevaluating the condition of soil heavy metal enrichment and the extent of potentialecological risk. Results demonstrated that the mean concentrations in the agricultural soilswere 2.23 mg/kg for Cd, 5.3 mg/kg for Cu, 38.002 mg/kg for Pb, and 13.84 mg/kg for Zn.The average concentrations of Cd and Pb in the agricultural soils were higher than averageworldwide soils and for Cu and Zn, values were lower than average worldwide soils. Thespatial mapping of the distribution of heavy metals produced by kriging interpolationshowed similar patterns for all heavy metals, and higher concentrations of all heavy metalswere observed in the western and southern parts of the study area. Our findingsdemonstrated that in the Siakh-Darengoun plain, natural sources affect the levels of Cu andZn, however, anthropogenic sources such as chemical fertilizers, especially phosphatefertilizers could be the major sources of Cd and Pb. Hossain Abad agro industry in the westof the study area can be considered as one of the most important heavy metal sources. Thegeo-accumulation index classified Cu and Zn into no pollution levels, Cd and Pb intounpolluted to moderately polluted level. Cd produced serious ecological risk in agriculturalsoils and was the main pollutant, while the Cu, Pb and Zn had low ecological risk.Comprehensive potential ecological risk indexes of all metals showed that the soils in SiakhDarengoun were suffering from high level of ecological risk.

Assessing heavy metal pollution and potential ecological risk of tea plantation soils

Accumulation of heavy metals in agricultural soils tends to increase crop uptake of heavy metals, and can adversely impact human health through food chains. This study assessed the heavy metal pollution status and the potential ecological risk of tea plantation soils in southern Shaanxi Province, China. A total of 330 topsoil samples were collected to analyze the concentrations of seven heavy metals (Pb, Zn, Cu, Cr, Hg, As and Cd) and the pH level. The Hakanson potential ecological risk index was used based on the background levels of soil heavy metals in Shaanxi. Results showed that the averaged concentrations of soil Pb, Zn, Cu, Cr, Hg, As, and Cd were 10.0, 87.6, 16.4, 12.4, 0.2, 6.9 and 0.1 mg/kg, respectively. Cd and Hg concentrations exceeded level II of China’s Soil Environment Quality Standard (GB 15618–2009) in 9.3% and 7.0% of the total samples, respectively. The coefficient of variation ranged from 29.2% to 52.2% for different elements, and was 49.3% for Cd and 48.6% for Hg. The averaged comprehensive potential ecological risk index was 95.4, and the overall potential ecological risk was low, with 82.4% of the total samples at a low level of potential ecological risk. Cd and Hg contributed most to the potential ecological risk (35.5% and 46.5%, respectively), and the risks associated with other elements were relatively minor. This study suggested that soil Cd and Hg pollution should be controlled to ensure the safe production of tea in the study area. Keywords: ecological risk, heavy metal, soil pollution, tea plantation DOI: 10.25165/j.ijabe.20191206.4363 Citation: Zhao Z P, Yan S, Duan M, Fu J, Wang Q, Liu Z F, et al. Assessing heavy metal pollution and potential ecological risk of tea plantation soils. Int J Agric & Biol Eng, 2019; 12(6): 185–191.

Spatial distribution and ecological risk assessment of heavy metals in soil from the Raoyanghe Wetland, China.

Wetlands are recognized as one of the most important natural environments for humans. At the same time, heavy metal pollution has an important impact on wetlands. China's Raoyanghe Wetland is one of the most important natural wild species gene banks in China. Eight heavy metal elements (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) in surface layer and deep layer soils were analyzed using statistical-, pollution index-, and Nemerow index-based methods, the Hakanson potential ecological risk index method, and principal component and cluster analyses. The results showed that the maximum concentrations of heavy metals exceeded the background values in the core area and buffer zone of the wetland, but the heavy metal content of the soils was generally low and did not exceed 30%. With the exception of Hg, heavy metal concentrations showed strong spatial differentiation. The differences between the surface layer and deep layer soils of the core area were smaller than in the buffer zone. With the exception of Cd, a clear vertical zonation in the buffer zone soils was observed, showing greater evidence of external influences in this zone than the core. With the exception of partial surface soils, which indicated a safe level of pollution in the core area, all other soils were classified as having a ‘mild’ level of pollution. Thus, the wetland is moderately polluted, with both the core area and the buffer zone presenting a low level of potential ecological risk. According to the results of the present study, heavy metal contaminants in the wetland soils were found to be derived mainly from the natural sources.

Comparative geochemical evaluation of toxic metals pollution and bacterial communities of industrial effluent tributary and a receiving estuary in Nigeria

Toxic metals/metalloid contaminations of estuarine sediments due to compromised tributaries arouse significant interest in studying bacterial community that triggers natural attenuation processes. Geo-accumulation index (Igeo), contamination factor (CF), pollution load index (PLI), and Hakanson potential ecological risk index (RI) as a sum of risk factors (Er) were used to quantify toxic metal/metalloid-pollution status of Lagos Lagoon (2W) and ‘Iya-Alaro’ tributary (4W) sediments in comparison with pristine ‘Lekki Conservation Centre’ sediment (L1-B). Bacteriology of the ecosystems was based on culture-independent analyses using pyrosequencing. 2W and 4W were extremely contaminated with mercury (Igeo > 7), whereas, cadmium contamination was only observed in 4W. The two ecosystems were polluted with toxic metal based on PLI, where mercury (Er = 2900 and 1900 for 4W and 2W, respectively) posed very high ecological risks. Molecular fingerprinting revealed that Proteobacteria, Firmicutes, and Acidobacteria predominately contributed the 20 most abundant genera in the two ecosystems. The 240 and 310 species present in 2W and 4W, respectively, but absent in L1-B, thrive under the metal concentrations in the polluted hydrosphere. Whereas, the 58,000 species missing in 2W and 4W but found in L1-B would serve as indicators for systems impacted with metal eco-toxicity. Despite toxic metal pollution of the ecosystems understudied, bacterial communities play vital roles in self-recovery processes occurring in the hydrosphere.

Heavy metal and soil nutrient accumulation and ecological risk assessment of vegetable fields in representative facilities in Shandong Province, China.

Shandong is one of the main areas for protected vegetable cultivation in China. A total of 88.5% of the facility soil samples had a pH between 7.0 and 8.4, indicating the majority of the soils were alkaline. Key properties, including total nitrogen (TN), organic matter (OM), electrical conductivity (EC), available phosphorus (AP), and available potassium (AK), showed an increasing trend with the number of years. The geoaccumulation index (Igeo) indicated that the Cd and Hg contents ranged from uncontaminated to moderate contaminated, while the risk of Hg and Cd reached the class of considerable risk as indicated by the potential ecological risk factor ([Formula: see text]). The mean of Hakanson potential ecological risk index (RI) was 234.00, with the highest contribution from Hg (55.26%), followed by Cd (38.81%). It indicated that the survey area was at the moderate-risk level and Hg had the highest potential ecological risk factor, followed by Cd.

Assessing heavy metal pollution and potential ecological risk of tea plantation soils

Accumulation of heavy metals in agricultural soils tends to increase crop uptake of heavy metals, and can adversely impact human health through food chains. This study assessed the heavy metal pollution status and the potential ecological risk of tea plantation soils in southern Shaanxi Province, China. A total of 330 topsoil samples were collected to analyze the concentrations of seven heavy metals (Pb, Zn, Cu, Cr, Hg, As and Cd) and the pH level. The Hakanson potential ecological risk index was used based on the background levels of soil heavy metals in Shaanxi. Results showed that the averaged concentrations of soil Pb, Zn, Cu, Cr, Hg, As, and Cd were 10.0, 87.6, 16.4, 12.4, 0.2, 6.9 and 0.1 mg/kg, respectively. Cd and Hg concentrations exceeded level II of China’s Soil Environment Quality Standard (GB 15618–2009) in 9.3% and 7.0% of the total samples, respectively. The coefficient of variation ranged from 29.2% to 52.2% for different elements, and was 49.3% for Cd and 48.6% for Hg. The averaged comprehensive potential ecological risk index was 95.4, and the overall potential ecological risk was low, with 82.4% of the total samples at a low level of potential ecological risk. Cd and Hg contributed most to the potential ecological risk (35.5% and 46.5%, respectively), and the risks associated with other elements were relatively minor. This study suggested that soil Cd and Hg pollution should be controlled to ensure the safe production of tea in the study area. Keywords: ecological risk, heavy metal, soil pollution, tea plantation DOI: 10.25165/j.ijabe.20191206.4363 Citation: Zhao Z P, Yan S, Duan M, Fu J, Wang Q, Liu Z F, et al. Assessing heavy metal pollution and potential ecological risk of tea plantation soils. Int J Agric & Biol Eng, 2019; 12(6): 185–191.