Sources Of Potentially Toxic Elements Research Articles

Impacts of parent material on distributions of potentially toxic elements in soils from Pearl River Delta in South China

Assessing the impacts of parent material on distributions of potentially toxic elements (PTEs) in soils has significant consequences in the apportionment of their sources. In this study, geochemical distributions and sources of PTEs in the soils developed in quaternary sediments and granite plutons of Pearl River Delta (PRD), South China, were investigated. The results indicate that there are systematic differences between the concentrations of oxides and PTEs in the soils developed in these two parent materials. The parent material predominantly determines the element distributions in the soils. The PTEs of the deep soils developed in quaternary sediments originated mainly from mafic, felsic, and carbonate sources materials as well as polymetallic deposits. For the deep soils developed in granite plutons, the element associations are governed mainly by their geochemical affinities and behaviors and the mineral compositions of granite plutons. Anthropogenic activities impact the features of the PTEs in the surface soils of PRD. However, superimposed regional-scale pollution was found to not hide the effect of the parent material on the distribution of PTEs in the surface soils.

The application of geostatistical analysis and receptor model for the spatial distribution and sources of potentially toxic elements in soils.

This study aimed to identify the spatial patterns of potentially toxic elements (PTEs), including the spatial distribution, spatial autocorrelation, and risk probability, and to quantify the sources of PTEs, to provide guidelines for soil management. Spatial distributions and probabilities of PTEs were determined by empirical Bayesian kriging (EBK), while spatial autocorrelation was estimated by Moran's I. Positive matrix factorization (PMF) was adopted for the quantitative source contributions of PTEs. More than 64.6% of Co, Cr, Mn, and Ni were derived from geogenic sources, with high regions and high-high clusters both correlated to sandstone. Thus, it can be deduced that parent materials dominated the spatial patterns of these PTEs. In addition, some hotspots were situated in urban areas, and the influence of human activities on these four PTEs should be considered. Industry-traffic discharge and parent materials both influenced As, Cu, Pb, and Zn. Nonetheless, the spatial patterns of As, Cu, Pb, and Zn were formed by anthropogenic emissions since hotspots and high-high clusters were contiguously situated in urban areas. 58.5% of Hg originated from atmospheric deposition related to industrial emissions, and 47.2% of Cd was controlled by the application of chemical fertilizers. High levels of Hg and Cd mainly corresponded with industrial sites and cultivated land, suggesting that industrial and geoponic production played major roles in the generation of spatial patterns for Hg and Cd, respectively. Furthermore, the Cd and Hg posed a severe risk to soils, with a high probability to surpass 1.5 times the backgrounds. The EBK, Moran's I, and PMF results showed that all ten PTEs were enriched to some degree due to natural or anthropogenic factors. The results of geostatistical analysis and the receptor model can be mutually verified, indicating the reliability of these methods.

Concentration, likely sources, and ecological risk assessment of potentially toxic elements in urban soils of Shiraz City, SW Iran: a preliminary assessment

Potentially toxic elements (PTE) are considered as hazardous pollutants that could have adverse effects on the environment. In recent decades, Shiraz, one of the largest cities of Iran, has been faced with extensive development and its environmental consequences. In this paper, urban soils of Shiraz were collected for preliminary evaluation of potential ecological risk as well as likely source identification of PTE (As, Pb, Cu, Co, Cr, Ni, Sr, and Zn). The concentrations of PTE were analyzed by inductively coupled plasma-optical emission spectrometry (ICP-OES). Geochemical indices (geo-accumulation index (Igeo) and enrichment factor (EF)) and potential ecological risk (PER) index were used to measure the contamination level. Correlation coefficient (CA) and principal component analyses (PCA) as statistical models were applied to recognize the probable sources of PTE. The study shows that the average levels of As, Pb, Cu, Co, Cr, Ni, Sr, and Zn in urban topsoil are 3.96, 11.5, 50.0, 11.5, 334.5, 102.0, 339.4, and 49.0 mg/kg, respectively. For both Igeo and EF, the values are Cu > Sr > Pb > Cr > Zn > Ni > Co > Cd > As. Geochemical indices indicate that the studied soils are mostly un-polluted to moderately polluted. Also, potential ecological risk assessment values of PTE are < 150, illustrating a low ecological risk level. Correlation coefficient and PCA suggest likely anthropogenic origins for Zn, Pb, Co, Ni, Cu, and As and geogenic source for Sr, while Cr appears to have a mixed anthropogenic origins.

Level, Source, and Spatial Distribution of Potentially Toxic Elements in Agricultural Soil of Typical Mining Areas in Xiangjiang River Basin, Hunan Province.

The concentrations, chemical availability, distribution, and sources of potentially toxic elements (PTEs) in the soil of Xiangjiang Basin in Hunan Province, China were investigated at 85 sites. The highest mean concentrations of Cd, Cu, Zn, As, and Pb were observed in Hengyang, whereas those for Mn, Co, and Hg were observed in Changde. The pollution index values followed the order: Cd > Hg > Cu > Zn > As > Pb; the mean geo-accumulation index values were in the order: Cd > Hg > Pb > Cu > Zn > As > Co > Mn. Cd was associated with moderate contaminated level, Hg and Pb were associated with moderate contaminated to uncontaminated level, and Cu, Zn, As, Co, and Mn were associated with uncontaminated level of pollution. Furthermore, 64.5% of Cd was water-soluble and exhibited exchangeable fractions; its chemical availability posed a risk to the ecosystem. Spatial analysis, principal component analysis, and a positive matrix factorization model were used to assess the PTE sources. Four principal components contributed to 88.8% of the 8 PTEs concentrations. Mining, smelting, industrial, and agricultural activities, alongside sewage irrigation, the use of agrochemicals, and vehicular emissions are the possible anthropogenic sources that pollute agricultural products and threaten human health in the Xiangjiang Basin.

Spatio-temporal variation and source changes of potentially toxic elements in soil on a typical plain of the Yangtze River Delta, China (2002–2012)

The spatio-temporal variation and temporal changes in the sources of Cr, Pb, Cd, Hg, and As in soil on the Hangzhou–Jiaxing–Huzhou (H-J-H) Plain were analysed based on 4,359 soil samples collected in 2002 and 2012. Geostatistical and spatial analysis methods were used to explore the spatio-temporal variation in the pollution levels and ‘pollution hotspots’ for potentially toxic elements (PTEs), and the positive matrix factor model was used to quantitatively appoint and analyse temporal changes in PTE sources. The results indicated that the PTE content in most parts of the survey area were at a safe level in both 2002 and 2012, but a clearly upward trend was detected for Cr, Pb, and Cd. Moreover the pollution index for Cr, Pb, Cd, and the Nemerow composite pollution index increased in the west but decreased in the east of the H-J-H Plain from 2002 to 2012. The pollution index for Hg and As presented the opposite spatial pattern. It is obvious that there have been changes in the spatial pattern of pollution hotspots for PTEs on the H-J-H Plain from 2002 to 2012. Four sources of PTEs in soil were quantitatively appointed. In 2002, 2012, the dominant sources of Cr, Cd, Hg, and As were soil parent materials, industrial activities, atmospheric deposition and agricultural inputs, respectively. The dominant source of Pb in the soil changed from traffic emissions to soil parent materials, indicating the benefit of banning the use of leaded gasoline in China. This study highlights the importance of monitoring soil environmental quality and highlights the significance of spatio-temporal variation in PTEs in suburban zones or transitional areas undergoing rapid industrialization and urbanization, like the H-J-H Plain.

Pollution, Sources and Human Health Risk Assessment of Potentially Toxic Elements in Different Land Use Types under the Background of Industrial Cities

Residents in industrial cities may be exposed to potentially toxic elements (PTEs) in soil that increase chronic disease risks. In this study, six types of PTEs (Zn, As, Cr, Ni, Cu, and Pb) in 112 surface soil samples from three land use types—industrial land, residential land, and farmland—in Tonghua City, Jilin Province were measured. The geological accumulation index and pollution load index were calculated to assess the pollution level of metal. Meanwhile, the potential ecological risk index, hazard index, and carcinogenic risk were calculated to assess the environmental risks. The spatial distribution map was determined by the ordinary kriging method, and the sources of PTEs were identified by factor analysis and cluster analysis. The average concentrations of Zn, As, Cr, Ni, Cu, and Pb were 266.57, 15.72, 72.41, 15.04, 20.52, and 16.30 mg/kg, respectively. The results of the geological accumulation index demonstrated the following: Zn pollution was present in all three land use types, As pollution in industrial land cannot be neglected, Cr pollution in farmland was higher than that in the other two land use types. The pollution load index decreased in the order of industrial land &gt; farmland &gt; residential land. Multivariate statistical analysis divided the six PTEs into three groups by source: Zn and As both originated from industrial activities; vehicle emissions were the main source of Pb; and Ni and Cu were derived from natural parent materials. Meanwhile, Cr was found to come from a mixture of artificial and natural sources. The soil environment in the study area faced ecological risk from moderate pollution levels mainly contributed by As. PTEs did not pose a non-carcinogenic risk to humans; however, residents of the three land use types all faced estimated carcinogenic risks caused by Cr, and As in industrial land also posed high estimated carcinogenic risk to human health. The conclusion of this article provides corresponding data support to the government’s policy formulation of remediating different types of land and preventing exposure and related environmental risks.

Spatial distribution of potentially toxic elements in urban soils of Abbottabad city, (N Pakistan): Evaluation for potential risk

Potentially toxic elements (PTE) are one of the main sources of soil toxicity with detrimental impacts on the environment due to their persistence, perseverance, and potential health risks. This study investigated the PTE such as nickel (Ni), lead (Pb), cadmium (Cd), cobalt (Co), iron (Fe), manganese (Mn), copper (Cu) and zinc (Zn) contaminations in urban soils of Abbottabad city, (N Pakistan). For this purpose, soils from different land types were collected and assayed for PTE level using atomic absorption spectrometry. Results showed relatively higher Fe and lower Cd contamination. The contamination factor (Cf), pollution load index (PLI) and ecological risk index (ERI) of pollution quantification factors were determined for PTE contamination. Results showed the relatively high Cf values for Ni and low for Pb. The PLI crossed the threshold of 1 in 40% of sampling sites, indicating significant PTE contamination at those sites. The ERI indicated low to considerable risk of PTE contamination across all sampling sites. The PTE were evaluated for carcinogenic and non-carcinogenic risks via ingestion, inhalation and dermal pathways. Health index (HI) values of 1.48E-02 and 1.18E-02 and cancer risk (CR) values of 9.39E-09 and 2.03E-04 were found for adults and children, respectively. Potential sources of PTE were quantitatively allocated by principal component analysis (PCA) along with geo-spatial analysis, indicating natural and anthropogenic inputs.

Identification of the sources and influencing factors of potentially toxic elements accumulation in the soil from a typical karst region in Guangxi, Southwest China

Southwestern China contains the largest and most well-developed karst region in the world, and the potentially toxic elements (PTEs) content in the soils of the region is remarkably high. To explore the internal and external control factors and sources of soil PTEs enrichment in this area and to provide a basis for the treatment of PTE pollution, 113 soil samples were collected from Hengxian County, a karst region in Guangxi Province, southwestern China. The importance of eighteen influencing factors including parent material, weathering, physicochemical properties, topography and human activities were quantitatively analyzed by (partial) redundancy analysis. The sources of PTEs were identified using the Pb isotope ratio and absolute principal component score/multiple linear regression (APCS-MLR) model. The contents of all soil PTEs were higher than the corresponding background values of Guangxi soils. The contents in Cu, Zn, Cd, Hg and Pb were the highest in the soil from carbonate rock. The factor group of geological background and weathering explained 26.5% for the accumulation and distribution of soil PTEs and the influence of physicochemical properties was less than 2% but increased to 25.6% through interaction with weathering. Fe (47.1%), Al (42.1%), Mn (22%), chemical index of alteration (12.8%) and clay (11.9%) were the key factors affecting the soil PTEs, while the influence of human activities was weak. Pb isotope ratio and APCS-MLR classified 62.8–74% of soil PTEs as derived from natural sources, whereas 18.23% and 18.95% were derived from industrial activities and agricultural practice/traffic emissions, respectively. The Pb isotope ratio showed that the natural sources account for up to 90% of the Pb in the soil from carbonate rock, the highest contribution among the studied soils. The results of the study can provide background information on the soil PTEs contamination in the karst areas of China and other areas worldwide.

Pollution Characteristics of Sb, As, Hg, Pb, Cd, and Zn in Soils from Different Zones of Xikuangshan Antimony Mine.

Major sources of pollution during the antimony (Sb) mining and processing are mining waste rock, smelting waste, tailings dam, and underground tunnel wastewater. The aim of the present study was to assess magnitude of pollution from Sb mine by taking four types of samples: soil in the mining waste rock zone, soil in the smelting zone, soil in tailings zone, and soil in underground tunnel wastewater zone. Sixty soil samples from the four zones were taken for experimental work, and the contents and morphological characteristics of the six potentially toxic elements (PTEs) such as Sb, As, Hg, Pb, Cd, and Zn in the soil samples were measured by using a hydride generation atomic fluorescence spectrometer (AFS-9700). The results show that the soil of the mine area is seriously polluted. The average contents of Sb, As, Hg, Pb, Cd, and Zn in the soil reach 1267.20 mg·kg−1, 94.44 mg·kg−1, 1.46 mg·kg−1, 184.19 mg·kg−1, 8.54 mg·kg−1, and 1054.11 mg·kg−1, respectively. There exists good correlation between the PTEs in the soil, with Sb strongly positively correlated with As, Hg, Pb, and Zn. The intensity of pollution is highest in the antimony-smelting zone, where the potential ecological risk index is over 15,000, followed by the tailings zone and mining waste rock zone, with the underground tunnel wastewater zone being the lowest. Using sequential chemical extraction, the elements are associated with the residual fraction, followed by organic-sulfide fraction, and smaller portions in the Fe-Mn oxide, carbonate, and exchangeable fractions. There are great differences in the speciation content of different elements in different sampling zones. The study implicates that Sb-smelting zone is the potential source of PTEs and maximum metals are associated with residual phase, out of which significant portion is associated with mobile fraction or phase.

A multivariate examination of the timing and accumulation of potentially toxic elements at Las Conchas bog (NW Spain)

The inorganic content of the well-preserved 3.2-m record of Las Conchas bog (NW Spain), covering 8000 cal yr BP., was analysed. To study natural vs. human contributions, we applied an innovative approach, namely the sequential study of multivariate statistics (factor analysis followed by clustering of the factor score matrix) and enrichment factors (EFs). The increasing weight of potentially toxic elements (PTEs) such as the geochemical association of Zn, Pb and Cd (EFs higher than 10, 20 and 40 in the last two centuries) was revealed, and corroborated by the contrast between the contents of anthropogenic Pb and total Rare Earth Elements (a suitable proxy for natural geogenic supplies). Furthermore, elements such as Hg, Tl and As also showed enrichment in the most recent samples of the study core. Some of them are commonly associated with global atmospheric transport; however, in this case, their increasing contents could also be explained by nearby industrial and mining activities.In summary, severe pollution was observed in the uppermost part of the record, thereby pointing to an important environmental concern. Given that local and regional sources of PTEs, such as mining and heavy industry, especially Zn smelting, were probably the main historical causes of this contamination and that some of these industries are still active, we consider that our findings deserve further attention.

Profile Distribution and Source Identification of Potentially Toxic Elements in North Nile Delta, Egypt

ABSTRACTVertical distribution and source appointment of potentially toxic elements (PTEs) provide a deeper vision for soil contamination. Contamination factor (CF), contamination degree (CD), enrichment factor (EF), principal component analysis (PCA), and cluster analysis (CA) were used for soil contamination assessment in north Nile Delta, Egypt. Twenty-one soil profiles representing main geomorphic units were dug, and 63 soil samples were collected at three depth intervals (0–30, 30–60 and 60–90 cm). Mean values of the three layers showed that Al, Fe, Mn, Cr, Cu, Pb, Mo, and V did not exceed average natural content of the Earth’s crust, while As, Cd, Co, Ni, and Zn exceeded that limit, except in the sand sheets unit. The studied elements showed irregular vertical distribution trend, except Cr, Ni, and Mo. Both Cr and Ni showed a downward migration, while Mo accumulated in the topsoil. Based on mean values, the CF indicated low contamination with Cr, Cu, Pb, Mn, Mo and V, moderate contamination with Cd and Zn, considerable contamination with As, Co, and Ni, while the CD was low to considerable. Furthermore, the EF indicated safe degree for Cr, Cu, Pb, Mo and V, deficiency to a minimal degree for Cd and Zn, while moderate degree for As, Co, and Ni. The PCA and CA indicated that soil parent materials controlled Al, Fe, Mn, Cu, Cr, Co, Pb, Ni, Mo, and V, while agricultural activities controlled As, Cd and Zn. Similar investigations should be considered in various regions in Egypt to verify potential sources of PTEs and to manage pollution of agricultural fields.

Enrichment of potentially toxic elements in the fine fraction of soils from Iraq and Kuwait

The fine fraction of soils in arid and semi-arid regions can be readily suspended into the atmosphere by winds and transported long distances, carrying potentially toxic elements (PTEs) associated with these source materials. In this study, environmentally available PTE loadings for As, Cd, Cr, Cu, Ni, Pb, V, and Zn were measured in the fine fraction (< 75 μm) of 19 bulk soil samples collected in 2007 from 4 sites in Iraq and 15 sites in Kuwait. Soil samples were mechanically sieved and particle size distribution in the fine fraction was measured using laser diffraction particle sizing. Major and minor element composition was determined in the soil fine fraction using energy-dispersive X-ray fluorescence. Sub-samples were digested using strong acids and analyzed using high-resolution inductively coupled mass spectrometry to assess the maximum environmental availability of PTEs in each fine fraction of each soil sample. Measured environmentally available PTE loadings were normalized to soluble iron to allow for an assessment of soil contamination at and between sites that included weathering effects and was more focused on the mobile fraction of the total PTE load. Physiologically based fluid extractions were also performed on select samples to assess potential bioavailability of PTEs through ingestion and inhalation. Results show significant PTE loadings and anthropogenic contamination in the fine fraction of soils from Iraq and Kuwait. All sites showed moderate-to-high Ni contamination but loadings and contamination levels for all PTEs varied among sites in Iraq and Kuwait as a function of weathering, local geology, and inputs from non-local and/or anthropogenic sources. PTE contamination tended to be higher in the fine fraction of soil collected at the sites in Iraq, and the lowest overall PTE loadings were found at sites in northern Kuwait where the mean measured particle diameter was largest. Potential bioavailability of PTEs via inhalation was generally low (< 10% of loading) but a significant portion of the PTE load for As, Cu, and Pb (and V and Zn at select sites) was available via ingestion. The fine fraction of soils collected from Iraq and Kuwait in this study had significant environmentally available PTE contamination. Sites from Lower Mesopotamia in Iraq were the most impacted. PTE loadings and contamination were strongly influenced by local-scale weathering and geology, proximity to urban PTE sources, and inputs from non-local and/or anthropogenic sources. Sites with a smaller mean particle diameter had the greatest levels of PTE contamination. Potential bioavailability of PTEs was generally low.

Risk-based assessment of soil pollution by potentially toxic elements in the industrialized urban and peri-urban areas of Ahvaz metropolis, southwest of Iran

The main purpose of this research was to assess the level of contamination, source identification, geochemical fractionation, and health risk of potentially toxic elements (PTEs) in industrial soils from urban and peri-urban areas of Ahvaz city. A total of 92 surface soil samples were gathered and concentrations of sixteen PTEs were measured using aqua regia digestion by an inductively coupled plasma mass spectrometry (ICP-MS). Possible sources of PTEs were quantitatively determined by positive matrix factorization (PMF) receptor model combined with geostatistical analyses and geochemical methods. The results showed that long-term industrial activities have enhanced the levels of some PTEs particularly Pb, Hg, Zn, Mo, Sb, Fe, Cu, and Cd to different extents. Contamination indices including geoaccumulation index, pollution index, and Nemerov integrated pollution index along with multivariate statistical analyses confirmed that steel and iron industries are the most contaminating industries in the study area. The outcomes attained from Kruskal-Wallis test affirmed that there was a significant difference among the concentrations of As, Hg, Mn, Cu, Fe, Pb, Mo, Cd, V, Zn, and Sb in soils around different industrial clusters. Among the studied elements, the highest mobility factors belonged to Zn (81.49%), Pb (76.71%), Cu (71.65%), Hg (66.23%), Mn (62.48%), and Mo (59.27%), respectively. Also, the PMF model showed that steel and iron industries (51.2%) and natural sources (23.4%) are the main sources of PTEs, followed by industrial towns (16.7%) and power plants (8.7%). This is in line with the results of principal component analysis (PCA). Majority of the measured PTEs showed the highest bioavailability in surface soils collected from around the steel and iron industries. Also, based on the outcomes of the health risk assessment model, particular attention should be paid to Hg, Pb, Zn, and Cu in industrial soils of Ahvaz.

Contamination Level, Source Identification and Risk Assessment of Potentially Toxic Elements (PTEs) and Polycyclic Aromatic Hydrocarbons (PAHs) in Street Dust of an Important Commercial Center in Iran.

The geochemical nature and health hazards of potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs) in the street dust of Bandar Abbas, Iran, are investigated in this study based on 27 street dust samples. Mean concentrations of Cu, Pb, Zn, As, Sb, and Hg revealed elevated concentrations as compared to the world soil average. Calculated enrichment factors (EFs) indicated that there is very high contamination in dust particles owing to anthropogenic emissions. Two main sources of PTEs are traffic emissions (Cu, Pb, Zn, Co, Mn, Fe, As, Cd, Sb, and Hg) and resuspended soil particles (Al, Ti, Ni, and Cr). Statistical analysis shows that Al, Mn, Ni, Ti, Cr, Fe, and Co are geogenic, whereas PAHs are mainly derived from traffic emissions. Values of incremental lifetime cancer risk (ILCR), as derived from a modified model of the United State Environmental Protection Agency (USEPA), indicate that Bandar Abbas residents are potentially exposed to high cancer risk, especially via dust ingestion and dermal contact, whereas the level of hazard index (HI), hazard quotients (HQ), and cancer risk associated with exposure to the elements in street dust fall lower than threshold values representative of health risks.

Impact of a severe flood on large-scale contamination of arable soils by potentially toxic elements (Serbia).

Extreme flooding in May, 2014 affected the sub-catchments of six major rivers in Serbia. The goal of the study was to evaluate the contents of potentially toxic elements (PTEs) As, Cd, Pb, Cr, Ni, Cu, and Zn in flood sediments and arable soils within the affected sub-catchments using regulatory guidelines and background levels. The sub-catchment of West Morava was selected to assess the degree of sediments and soils contamination and environmental risk [using the Pollution index (Pi), Enrichment factor, Geo-accumulation index, and Potential ecological risk index (PERI)] as well as to identify main PTEs sources by Principal component (PCA) and cluster analysis. Contents of Ni, Cr, As, Pb, and Cu above both guidelines and background levels, and of Zn and Cd above background levels were detected in the sediments and soils from all the sub-catchments. Pi indicted that about 95% of the soils and sediments were extremely polluted by Ni and about 65% slightly polluted by Cr, whereas about 90% were not polluted by As, Cd, Pb, Cu, or Zn. Ef indicated minor to moderate enrichment of the soils and sediments by Ni, and Cr. PCA differentiated a geogenic origin of Ni, Cr, As, and Pb, a mixed origin of Cd and Zn, and a predominantly anthropogenic origin of Cu. PERI of the soils and sediments suggested a low overall multi-element ecological risk. The ecological risk of the individual elements (E r i ) for soils was Zn < Cr < Pb < Ni < Cu < As < Cd.

Multi-Target Risk Assessment of Potentially Toxic Elements in Farmland Soil Based on the Environment-Ecological-Health Effect.

There are potential impacts of Potentially Toxic Elements (PTEs) (e.g., Cd, Cr, Ni, Cu, As, Zn, Hg, and Pb) in soil from the perspective of the ecological environment and human health, and assessing the pollution and risk level of soil will play an important role in formulating policies for soil pollution control. Lingyuan, in the west of Liaoning Province, China, is a typical low-relief terrain of a hilly area. The object of study in this research is the topsoil of farmland in this area, of which 71 soil samples are collected. In this study, research methods, such as the Nemerow Index, Potential Ecological Hazard Index, Ecological Risk Quotient, Environmental Exposure Hazard Analysis, Positive Matrix Factorization Model, and Land Statistical Analysis, are used for systematical assessment of the pollution scale, pollution level, and source of PTEs, as well as the ecological environmental risks and health risks in the study area. The main conclusions are: The average contents of As, Cd, Cr, Cu, Hg, Zn, Ni, and Pb of the soil are 5.32 mg/kg, 0.31 mg/kg, 50.44 mg/kg, 47.05 mg/kg, 0.03 mg/kg, 79.36 mg/kg, 26.01 mg/kg, and 35.65 mg/kg, respectively. The contents of Cd, Cu, Zn, and Pb exceed the background value of local soil; Cd content of some study plots exceeds the National Soil Environmental Quality Standard Value (0.6 mg/kg), and the exceeding standard rate of study plots is 5.63%; the comprehensive potential ecological hazard assessment in the study area indicates that the PTEs are at a slight ecological risk; probabilistic hazard quotient assessment indicates that the influence of PTEs on species caused by Cu is at a slight level (p = 10.93%), and Zn, Pb, and Cd are at an acceptable level. For the ecological process, Zn is at a medium level (p = 25.78%), Cu is at a slight level (19.77%), and the influence of Cd and Pb are acceptable; human health hazard assessment states that the Non-carcinogenic comprehensive health hazard index HI = 0.16 < 1, indicating that PTEs in soil have no significant effect on people’s health through exposure; the PMF model (Positive Matrix Factorization) shows that the contribution rates of agricultural source, industrial source, atmospheric dust source, and natural source are 13.15%, 25.33%, 18.47%, and 43.05%, respectively.

Background concentrations and quality reference values for some potentially toxic elements in soils of São Paulo State, Brazil

Quality reference values (QRV) for potentially toxic elements (PTE) in soils are established as a tool for prevention and monitoring of soil pollution. These values should be periodically revised in order to ensure soil safety for agricultural purposes. Brazil is market leader for several commodities; therefore, the safety of Brazilian soils is of worldwide strategic importance. The objective of this study was to determine the natural background concentrations and the QRV for As, Ba, Cd, Cr, Ni, Pb, Se, and Zn by investigating 30 representative pedotypes in the São Paulo State, one of the most important agro-industry economy at worldwide level. Multivariate statistical analysis was applied to determine the sources of PTE and their variability. The mean natural background concentrations of PTE in the soils were generally lower to those reported in literature. QRV, calculated for each element as the 75th and 90th percentiles, were lower (75th for As, Cd, Pb, and Zn), similar (75th for Ba, Cr, and Se) or above (90th for Ba, Cr, and Se and 75-90th for Ni) those previously proposed by the Brazilian environmental protection agencies. The results indicate that 75th percentile may be too restrictive. The PTE in the investigated soils appear to have comes mainly from two primary natural sources: a prevalent one of geogenic and a secondary of pedogenic origin. These results confirm the predominant natural source of selected PTE in the investigated soils, thus sustaining the possibility of using the data set to develop QRV for the State of São Paulo.

Source apportionment and health risk assessment of potentially toxic elements in road dust from urban industrial areas of Ahvaz megacity, Iran.

This study investigates the occurrence and spatial distribution of potentially toxic elements (PTEs) (Hg, Cd, Cu, Mo, Pb, Zn, Ni, Co, Cr, Al, Fe, Mn, V and Sb) in 67 road dust samples collected from urban industrial areas in Ahvaz megacity, southwest of Iran. Geochemical methods, multivariate statistics, geostatistics and health risk assessment model were adopted to study the spatial pollution pattern and to identify the priority pollutants, regions of concern and sources of the studied PTEs. Also, receptor positive matrix factorization model was employed to assess pollution sources. Compared to the local background, the median enrichment factor values revealed the following order: Sb>Pb>Hg>Zn>Cu>V>Fe>Mo>Cd>Mn>Cr≈Co≈Al≈Ni. Statistical results show that a significant difference exists between concentrations of Mo, Cu, Pb, Zn, Fe, Sb, V and Hg in different regions (univariate analysis, Kruskal-Wallis test p<0.05), indicating the existence of highly contaminated spots. Integrated source identification coupled with positive matrix factorization model revealed that traffic-related emissions (43.5%) and steel industries (26.4%) were first two sources of PTEs in road dust, followed by natural sources (22.6%) and pipe and oil processing companies (7.5%). The arithmetic mean of pollution load index (PLI) values for high traffic sector (1.92) is greater than industrial (1.80) and residential areas (1.25). Also, the results show that ecological risk values for Hg and Pb in 41.8 and 9% of total dust samples are higher than 80, indicating their considerable or higher potential ecological risk. The health risk assessment model showed that ingestion of dust particles contributed more than 83% of the overall non-carcinogenic risk. For both residential and industrial scenarios, Hg and Pb had the highest risk values, whereas Mo has the lowest value.

Sustainable Soil Washing: Shredded Card Filtration of Potentially Toxic Elements after Leaching from Soil Using Organic Acid Solutions.

Shredded card (SC) was assessed for use as a sorbent of potentially toxic elements (PTE) carried from contaminated soil in various leachates (oxalic acid, formic acid, CaCl2, water). We further assessed SC for retention of PTE, using acidified water (pH 3.4). Vertical columns and a peristaltic pump were used to leach PTE from soils (O and A/B horizons) before passing through SC. Sorption onto SC was studied by comparing leachates, and by monitoring total PTE contents on SC before and after leaching. SC buffers against acidic soil conditions that promote metals solubility; considerable increases in solution pH (+4.49) were observed. Greatest differences in solution PTE content after leaching with/without SC occurred for Pb. In oxalic acid, As, Cd, Pb showed a high level of sorption (25, 15, and 58x more of the respective PTE in leachates without SC). In formic acid, Pb sorption was highly efficient (219x more Pb in leachate without SC). In water, only Pb showed high sorption (191x more Pb in leachate without SC). In desorption experiments, release of PTE from SC varied according to the source of PTE (organic/mineral soil), and type of solvent used. Arsenic was the PTE most readily leached in desorption experiments. Low As sorption from water was followed by fast release (70% As released from SC). A high rate of Cd sorption from organic acid solutions was followed by strong retention (~12% Cd desorption). SC also retained Pb after sorption from water, with subsequent losses of ≤8.5% of total bound Pb. The proposed use of this material is for the filtration of PTE from extract solution following soil washing. Low-molecular-mass organic acids offer a less destructive, biodegradable alternative to strong inorganic acids for soil washing.