Spatial Eco-Risk Assessment of Heavy Metals in the Surface Soils of Industrial City of Aran-o-Bidgol, Iran

Assessment of environmental and health risks of potentially toxic elements associated with desert dust particles affected by industrial activities in Isfahan metropolitan

Dust particles and their associated compounds can adversely affect human health and ecosystems. The aim of this study was to investigate the concentration, health, and ecological risks of selected potentially toxic elements (e.g. Pb, Cd, Cr, Co, Cu, Zn, V, Ni, and As) bound to air particles generated by dust storms in the Sejzi plain desert area within the industrial district of Isfahan metropolitan, Iran. The enrichment factor revealed the highest values for Zn, Pb, and Cd which among them Zn showed the highest value (8.1) with the potential source of industrial activities confirmed by the integrated pollution index, accumulation coefficient, and ecological risk index. Regarding health risk analysis (non-cancer and cancer risks) the elements including Co, As, and Cr showed a significant risk for adults and children across all seasons. It's concluded that mitigation of air particles originated from both natural and industrial activities is necessary to reduce their relevant risks to human being and ecosystems in the region.

Assessment of land use effect, mapping of human health risks and chemometric analysis of potential toxic elements in topsoils of Aran-o-Bidgol, Iran

This study examines topsoil contamination in Aran-o-Bidgol urban region of central Iran, with a focus on potentially toxic elements (PTEs). A total of 135 topsoil samples in different land types were characterized, ranging from areas with agricultural farms, desert, industrial and residential activity, and brick kilns. The average concentrations of Cd, Pb, Cu, Ni, Cr, Co, Fe, Zn, and Mn were 0.72, 11.41, 14.82, 29.87, 51.13, 106.69, 8741.87, 48.59, and 346.42 mg kg-1, respectively, which all exceed the local background levels. The results reveal that land use significantly affected PTE concentrations. Cr, Co, Mn, and Fe concentrations in soils of residential and brick kiln areas were especially high. In contrast, concentrations of Cu, Ni, and Zn were higher in agricultural and residential areas. Risk assessment analysis showed that the sum of toxic units for PTEs for brick kilns (1.72), residential (1.82), and agricultural (1.79) areas exceeded those of other land types and that Ni and Cr contributed the most to the high toxic risk index values. Both carcinogenic and non-carcinogenic risk indices of PTEs in soils were within an acceptable limit, except for the cancer risk of Ni (3.52E-04) and Cr (3.00E-04) among children. The spatial hazard index and carcinogenic health risk of PTEs showed that samples from the southwestern parts of the study area might pose significant health problems to adults and children. This study demonstrates how combining different techniques can help spatially characterize PTE accumulation and protect populations at risk.

Receptor model-based sources and risks appraisal of potentially toxic elements in the urban soils of Bangladesh

Rapid urbanization and industrial development have prompted potentially toxic elements (PTEs) in urban soil in Bangladesh, which is a great concern for ecological and public health matters. The present study explored the receptor-based sources, probable human health and ecological risks of PTEs (As, Cd, Pb, Cr, Ni, and Cu) in the urban soil of the Jashore district, Bangladesh. The USEPA modified method 3050B and atomic absorption spectrophotometers were used to digest and evaluate the PTEs concentration in 71 soil samples collected from eleven different land use areas, respectively. The concentration ranges of As, Cd, Pb, Cr, Ni, and Cu in the studied soils were 1.8-18.09, 0.1-3.58, 0.4-113.26, 0.9-72.09, 2.1-68.23, and 3.82-212.57 mg/kg, respectively. The contamination factor (CF), pollution load index (PLI), and enrichment factor (EF) were applied to evaluate the ecological risk posed by PTEs in soils. Soil quality evaluation indices showed that Cd was a great contributor to soil pollution. The PLI values range was 0.48-2.82, indicating base levels to continuous soil degradation. The positive matrix factorization (PMF) model showed that As (50.3 %), Cd (38.8 %), Cu (64.7 %), Pb (81.8 %) and Ni (47.2 %) were derived from industrial sources and mixed anthropogenic sources, while Cr (78.1 %) from natural sources. The highest contamination was found in the metal workshop, followed by the industrial area, and brick filed site. Soil from all land use types revealed moderate to high ecological risk after evaluating probable ecological risks, and the descending order of single metal potential ecological risk was Cd > As > Pb > Cu > Ni > Cr. Ingestion was the primary route of exposure to potentially toxic elements for both adults and children from the study area soil. The overall non-cancer risk to human health is caused by PTEs for children (HI=0.65 ± 0.1) and adults (HI=0.09 ± 0.03) under USEPA safe limit (HI>1), while the cancer risks from exclusively ingesting As through soil were 2.10E-03 and 2.74E-04 for children and adults, respectively, exceeding the USEPA acceptable standard (>1E-04).

Environmental Controls to Soil Heavy Metal Pollution Vary at Multiple Scales in a Highly Urbanizing Region in Southern China

Natural and anthropogenic activities affect soil heavy metal pollution at different spatial scales. Quantifying the spatial variability of soil pollution and its driving forces at different scales is essential for pollution mitigation opportunities. This study applied a multivariate factorial kriging technique to investigate the spatial variability of soil heavy metal pollution and its relationship with environmental factors at multiple scales in a highly urbanized area of Guangzhou, South China. We collected 318 topsoil samples and used five types of environmental factors for the attribution analysis. By factorial kriging, we decomposed the total variance of soil pollution into a nugget effect, a short-range (3 km) variance and a long-range (12 km) variance. The distribution of patches with a high soil pollution level was scattered in the eastern and northwestern parts of the study domain at a short-range scale, while they were more clustered at a long-range scale. The correlations between the soil pollution and environmental factors were either enhanced or counteracted across the three distinct scales. The predictors of soil heavy metal pollution changed from the soil physiochemical properties to anthropogenic dominated factors with the studied scale increase. Our study results suggest that the soil physiochemical properties were a good proxy to soil pollution across the scales. Improving the soil physiochemical properties such as increasing the soil organic matter is essentially effective across scales while restoring vegetation around pollutant sources as a nature-based solution at a large scale would be beneficial for alleviating local soil pollution.

Evaluation of potential ecological risks in potential toxic elements contaminated agricultural soils: Correlations between soil contamination and polymetallic mining activity

Extensive mineral exploitation activities in history have aggravated potential toxic elements (PTEs) contamination in agricultural soils in China. Comprehensive ecological risk assessment is of great significance to orientate the restoration of contaminated soils, especially for those with high background values and multiple sources. The study area is located in the major rice producing area of China. Historically, there was a silver mine and a lead-zinc mine in the area, which were successively closed during the investigation. The intensive mining activities caused serious PTEs pollution in the agricultural soils around the mining area. In this study, five PTEs (As, Cd, Cr, Hg and Pb) selected to assessed the potential of geoaccumulation index in assessing agricultural soil potential risk assessment by identifying ecological risk sources. 315 of soil samples collected in 2009, 2014, 2018 were comprehensively analyzed by single pollution index evaluation (single factor index, geoaccumulation index), comprehensive evaluation (Nemerow index, potential ecological risk index) and trend analysis. Single factor index analysis showed that geoaccumulation index considered the impact of natural diagenesis of background values and human activities on the environment, ensuring high evaluation accuracy comparing to other methods used in typical complex agricultural soils. The modified potential ecological risk index revealed that the high background area did not represent high risk area, which was consistent with the implementation effect of governance measures. This study can provide important insights for policymakers and environmental engineers to quantitatively recognize the soil pollution and the effectiveness of governance based on applicable and reasonable evaluation methods.

Trends in soil mercury stock associated with pollution sources on a Mediterranean island (Majorca, Spain)

Hg is a global concern given its adverse effects on human health, food security and the environment, and it requiring actions to identify major local Hg sources and to evaluate pollution. Our study provides the first assessment of Hg stock trends on the entire Majorca surface, identifying major Hg sources by studying the spatiotemporal soil Hg variation at two successive times (2006 and 2016-17). The Hg soil concentration ranged from 14 to 258 μg kg^-1 (mean 52 μg kg^-1). Higher concentrations (over 100 μg kg^-1) were found in two areas: (i) close to the Alcudia coal-fired power plant; (ii) in the city of La Palma. During the 11-year, the total Hg stock in Majorcan soil increased from 432.96 tons to 493.18 tones (14% increase). Based on a block kriging analysis, soil Hg enrichment due to power plant emissions was clearly detectable on a local scale (i.e. a shorter distance than 18 km from the power plant). Nonetheless, a significant island-wide Hg increase due to diffuse pollution was reported. This result could be extrapolated to other popular tourist destinations in the Mediterranean islands where tourism has increased in recent decades In short, more than 60 tons of Hg have accumulated on Majorca island in 11 years.

Spatial and temporal assessment of cadmium and chromium contamination in soils in the Karditsa region (Central Greece)

In this work, we aimed at monitoring Cd and Cr levels in surface soils in the Karditsa region (Central Greece). Soil samples were obtained throughout 3 years (2010 to 2012) and analyzed for extractable (DTPA) and for "pseudo"-total concentrations (aqua regia) of Cd and Cr. The temporal variability, recorded twice per year, was also assessed. Significant spatial variability was recorded and illustrated by the respective thematic maps created using geostatistics, with the use of ordinary kriging. We found a possible geochemical connection and interactions between the two studied metals that indicated common lithogenic origin, while Cd was found further enriched due to likely applied phosphate fertilizers over long periods of time. We conclude that although the mapping of soil properties and metal contents is a useful tool when initially visiting an area, further in-depth studies should be conducted; such studies should address issues related to bioavailability of soil pools that may be linked to plant concentrations and possible risks of metals being transferred to plants or even humans.

Pollution and Ecological Risk Evaluation of Heavy Metals in the Soil and Sediment around the HTM Tailings Pond, Northeastern China

Tailings ponds are a main heavy metal pollution source in mining areas. In this study, the geo-accumulation index (Igeo) and the potential ecological risk index (RI) are used to evaluate the environmental impact of Hongtou Mountain (HTM) tailings pond on the surrounding area. Farmland soil, surface water, and sediment samples in the Hun River around the HTM tailings pond were collected. Heavy metal contents in the samples were analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Results show that Cu, Zn, and Cd content in the farmland soil and sediment around the lower reaches of the Hun River (HTM tailings pond section) are obviously higher than the upper reaches. The Igeo values show that the farmland soil near the outlet of the tailings pond is the most polluted area. Cu was classified as moderate-strongly pollution, Zn was moderately pollution, and Cd was strongly pollution. Cd is the major pollutant in farmland soil, the monomial ecological risk (Eri) for Cd is a very high potential ecological risk. The potential ecological risk of sediment in the dry season is more serious than in the raining season. In the dry season, the Igeo index shows strong pollution for Cu and Cd at the confluence of the Hun River and the tributary from the HTM tailings pond, and a moderate-strongly pollution for Zn. Whereas, the Eri index shows that the monomial ecological risk for Zn at H3 is low, and Cu is moderate. The potential ecological risk at H3 is high, and Cd is the main source of the ecological risk around the HTM tailings pond.

Effects of Mercapto-functionalized Nanosilica on Cd Stabilization and Uptake by Wheat Seedling (Triticum aestivum L.) in an Agricultural Soil

In the present study, a pot-culture experiment was conducted to investigate the influences of mercapto-functionalized nanosilica (MPTS/nano-silica) on Cd stabilization and uptake by wheat seedling. Four different dosages of MPTS/nano-silica were applied: 0%, 0.3%, 0.6% and 1% (w/w), and the changes of DTPA-extractable Cd in soil, soil properties, wheat biomass, and uptake of Cd to wheat tissues (shoots and roots) were measured throughout the experiment. The results showed that the application of MPTS/nano-silica (at dose of 1%) reduced the DTPA-extractable Cd from 4.21 to 1.45 mg/kg in the soil. Whereas the addition of MPTS/nano-silica hardly changed soil properties and slightly decreased the biomass of wheat seedling. In addition, Cd concentration in wheat tissues decreased from 6.388 to 2.625 mg/kg for shoot, and from 18.622 to 6.368 mg/kg for root. These results indicated that MPTS/nano-silica is an ideal candidate for remediation of Cd contaminated agricultural soil.

Pollution assessment of potentially toxic elements in soils of different taxonomy orders in central Greece

Four hundred fifty soil samples of the orders of Alfisols, Inceptisols, Endisols, and Vertisols from Karditsa, Trikala, and Larissa (Central Greece) were collected over a three-year period. In these samples we analyzed potentially toxic elements (PTEs) and soil properties known to affect their mobility. High regression coefficients were observed between soil pH and PTE concentrations in Alfisols, reflecting that soil pH is the dominant characteristic influencing PTEs. In Inceptisols, there was a significant interaction among the studied PTEs, probably due to PTEs having the same origin. The Endisol samples had high sand content and electrical conductivity values, resulting in high availability of all studied PTEs. In Vertisols, clay content proved to be the most important parameter influencing PTE levels. Factor analysis was also used in order to clarify the possible sources of metals in the studied areas.

Tissue distribution and oral exposure risk assessment of heavy metals in an urban bird: magpie from Central Iran

Direct ingestion of soil and/or soil attached to the food items is a potential rout for wildlife exposure to contaminants. In this study, bioaccumulation of five heavy metals (HMs) in internal tissues of an urban bird (Pica pica) collected from Aran-O-Bidgol City, Central Iran and their related soil were investigated. A total of 15 magpie specimens were collected in autumn 2013 and then their internal tissues were digested using a mixture of HNO₃ and H₂O₂, and finally, concentrations of HMs were detected by ICP-OES. In addition, in order to show level of HM exposure risk to magpie, an exposure risk assessment was modeled. Results indicated that HMs were accumulated as follows: liver > kidney > muscle. Zn and Cu were significantly higher in magpie's tissues collected from agricultural site; on the other hand, Pb and Cd were significantly higher in industrial site (p < 0.05). Level of Cd in male's livers (2.11 μg/g dw) was significantly higher than in females (1.85 μg/g dw) (p < 0.05). Levels of Cd, Pb, and Ni in liver, muscle, and kidney, respectively, were significantly higher in adults than in subadults (p < 0.05). Soil exposure doses of all HMs were lower than tolerable daily intake (Zn 4.35, Cu 1.34, Ni 5.65, Pb 0.35, and Cd 0.53). The calculated hazard quotations (HQs) for HMs were as follows: Pb > Zn > Cu > Ni > Cd and for all HMs were at no risk level (HQ < 1). The amounts of hazard index for three sites were as follows: urban (1.032) > agriculture (0.943) ≥ industry (0.941) and only for urban area was at low risk (1 < HQ < 2). It seemed that birds living in a safe environment and/or HM contaminations in soil separately had no negative effects on magpies. We can also suggest that low levels of HMs in magpie's tissues can be due to low levels of HMs in soil.