Distribution and health risk assessment of potentially toxic elements in soils around coal industrial areas: A global meta-analysis

Coal production and utilization are recognized as two principal sources of potentially toxic elements in the environment. Here the published literature (2008-2018) was searched to collect data on As, Ni, Cd, Cu, Cr, Hg, Pb and Zn concentrations in soils near different types of coal industrial areas such as coal mines, thermal power plants, coal chemical plants, coal mining cities and coal waster piles. The contamination levels of soils and associated health risks were assessed using global reference materials and multiple contamination indices. The results revealed that average concentrations of potentially toxic elements varied widely, yet most of them exceeded global averages in background soils and upper continental crust concentrations. Spatial distribution analysis suggested the concentrations of potentially toxic elements varied according to coalification and combustion conditions. Higher concentrations were found in Southeast Asia, South Europe, and North Africa compared with other regions. Assessment of the geoaccumulation index revealed that contamination levels of Cd and Hg were higher than those of other elements. In particular, Ni, Cd, Zn, and Hg were most likely to accumulate in soils near coal mining areas, while Cd and Hg tended to accumulate near coal chemical plants. Regarding non-carcinogenic risks, oral ingestion was the major pathway of exposure to potentially toxic elements in coal industry-associated soils, followed by dermal contact and inhalation. Tolerable non-carcinogenic risk of potentially toxic elements and relatively high carcinogenic risks of As were observed. Children were most vulnerable to non-carcinogenic risks, while the carcinogenic risks estimated for adult and children populations were similar. Accordingly, As should be designated as top candidates for priority control to protect human health in the vicinity of coal industry-associated areas. This study provides timely information for developing control and management strategies to reduce soil contamination by potentially toxic elements in different types of coal industrial areas.

Microplastics influence the adsorption and desorption characteristics of Cd in an agricultural soil

Microplastics (MPs) in terrestrial ecosystems particularly agroecosystem are attracting increasing attention worldwide. However, the influences of MPs on adsorption and desorption of contaminants in agricultural soils remain unknown. Here, batch experiments were conducted to study the effects of polyethylene MPs on Cd adsorption and desorption in a farmland soil under varying conditions. Both Cd adsorption and desorption in soils with or without MPs reached equilibrium within 120 min. Cd adsorption kinetics followed the pseudo-second order model, and the adsorption isotherm fitted to the Langmuir model more precisely than the Freundlich model. Overall, addition of MPs decreased Cd adsorption but increased desorption, and the effects varied with MPs dose and particle size, and solution pH. MPs-induced decrease in Cd adsorption and increase in Cd desorption were more pronounced at higher MPs dose and larger particle size, but varied differently from solution pH. EDS analysis confirmed Cd adsorption on MPs surface. Both MPs before and after Cd adsorption showed similar XRD patterns, indicating MPs maintained a high crystallinity and no new crystalline phases formed. In conclusion, the input of MPs into soil might enhance the mobility of Cd via mitigating soil adsorbing capacity, thereby posing additional risks of Cd to agroecosystem.

Foliage application of selenium and silicon nanoparticles alleviates Cd and Pb toxicity in rice (Oryza sativa L.)

Direct discharge of untreated industrial waste water in water bodies and then irrigation from these sources has increased trace metals contamination in paddy fields of southern China. Among trace metals, cadmium (Cd) and lead (Pb) are classified as most harmful contaminants in farmland to many organisms including plants, animals and humans. Rice is a staple food which is consumed by half population of the world; due to longer growth period it can easily absorb and accumulate the trace metals from soil. The objective of study was to check the efficacy of Se and Si NPs (nanoparticles) alone or in combination on metals accumulation and Se-fortified rice (Oryzasativa L.) production as their efficiency remained untested. Alone as well as combined application of Se- and Si-NPs (5, 10 and 20 mg L^-1) was achieved along with CK. All the treatments significantly reduced the Cd and Pb contents in brown rice, except CK, Se3, Si1 and Se1Si3. Combined application of Se and Si (Se3Si2) was more effective in reducing the Cd and Pb contents by 62 and 52%, respectively. In addition, foliar application of both NPs improved the rice growth and quality by increasing the grain yield, rice biomass, and Se contents in brown rice. Highest concentration of Se (1.35 mg kg^-1) in brown rice was observed with combined application of Se- and Si-Nps (Se3Si2). Selenium speciation revealed the presence of organic species (74%) in brown rice. The combinations of different doses of Se- and Si-Nps are the main determining factor for total concentration of metals in grains. These results demonstrate that foliage supplementation of Se and Si-Nps alleviate the Cd and Pb toxicity by reducing the metals' concentration in brown rice. Additionally foliage supplementation improved the nutritional quality by reducing the phytic acid contents in rice grains.

Effects of lead ions on germination, initial growth, and physiological characteristics of Lolium perenne L. species and its bioaccumulation potential

The present study was conducted to investigate the responses of Lolium perenne L. species to lead ions. To do this, the effects of lead ions at five levels: control (blank), 250, 500, 750, and 1000 mg/kg or mg/L (depending on germination in the soil or petri dish) on the germination, initial growth, and physiological characteristics of Lolium perenne were investigated. The results showed that the difference between various lead concentrations was statistically significant at 1% confidence level in all of the germination, vegetative, and physiological characteristics. In addition, the results of translocation and stress factors indicated that there was a significant difference between the control treatment and the concentrations of 250, 500, 750, and 1000 mg/L of lead ions. Results show that the mean value of stress, which was 0.3196 in the control value, reached 0.4154 at the concentrations 1000 mg/L. Different levels of lead ions had significant effect on the estimated characteristics including germination percentage, seed vigor, germination index, chlorophyll a, chlorophyll b, carotenoids, root, and shoot. The average germination percentage in the control was 46.66%, which decreased by 5% at the highest lead concentration. In addition, the average of seed vigor, which was 34.06 in the control conditions, decreased to 0.72 at the highest lead concentration. Also, the chlorophyll a dropped from 0.5261 mg/g in the control conditions to 0.3149 mg/g. On the other hand, increase in lead ion concentration affected the physiological characteristics of Lolium perenne species. Results suggest that Lolium perenne is capable of accumulating lead and is well tolerant to lead in soil. Therefore, it is concluded that it can be used for sowing on lands which are polluted to this heavy metal (up to the concentration of 1000 mg/kg).

From classic methodologies to application of nanomaterials for soil remediation: an integrated view of methods for decontamination of toxic metal(oid)s

Soil pollution with toxic elements is a recurrent issue due to environmental disasters, fossil fuel burning, urbanization, and industrialization, which have contributed to soil contamination over the years. Therefore, the remediation of toxic metals in soil is always an important topic since contaminated soil can affect the environment, agricultural safety, and human health. Many remediation methods have been developed; however, it is essential to ensure that they are safe, and also take into account the limitation of each methodology (including high energy input and generation of residues). This scenario has motivated this review, where we explore soil contamination with arsenic, lead, mercury, and chromium and summarize information about the methods employed to remediate each of these toxic elements such as phytoremediation, soil washing, electrokinetic remediation, and nanoparticles besides elucidating some mechanisms involved in the remediation. Considering all the discussed techniques, nowadays, different techniques can be combined together in order to improve the efficiency of remediation besides the new approach of the techniques and the use of one technique for remediating more than one contaminant.

Probabilistic estimates of prenatal lead exposure at 195 toxic hotspots in low- and middle-income countries

BACKGROUND

Prior estimates of pediatric lead-related disease burden in low- and middle-income countries (LMICs) used population estimates of maternal blood lead levels (BLLs). This approach may underestimate fetal BLLs by not considering potentially high prenatal lead exposure from toxic hotspots. OBJECTIVES: We developed a probabilistic approach to using the Adult Lead Methodology (ALM) to estimate fetal BLLs from prenatal exposure to lead-contaminated soil at hotspots in the Toxic Site Identification Program (TSIP).

METHODS

We created distributions for each ALM parameter using published literature and extracted soil lead measurements from the TSIP database. Each iteration of the probabilistic ALM randomly selected values from the input distributions to generate a site-specific fetal BLL estimate. For each site, we ran 5000 model iterations, producing a site-specific fetal BLL distribution.

RESULTS

195 TSIP sites, in 33 LMICs, met our study inclusion criteria; an estimated 820,000 women of childbearing age are at risk for lead exposure at these sites. The predicted geometric means (GM) for site-specific fetal BLLs ranged from 3.3 μg/dL to 534 μg/dL, and 98% of sites had estimated GM fetal BLLs >5 μg/dL, the current reference level of the United States Centers for Disease Control and Prevention (CDC), while 11 sites had estimated GM fetal BLLs above the CDC chelation threshold of 45 μg/dL.

DISCUSSION

The TSIP soil lead data and this probabilistic approach to the ALM show that pregnant women living near TSIP sites may have BLLs that put their fetus at risk for neurologic damage and other sequelae, underscoring the need for interventions to reduce lead exposure at toxic hotspots.

Environmental, ecological and health risks of trace elements, and their sources in soils of Harran Plain, Turkey

Soil pollution with trace elements (TEs) has become an increasingly serious environmental concern, however, assessment of ecological and human health risks especially in intensive agricultural regions remains limited. In this study, the contents of ten TEs (Al, As, Pb, Cr, Cu, Zn, Ni, Co, Mn and Fe) in soil samples from 204 sampling sites in the Harran Plain (Turkey) were examined to evaluate possible sources, pollution status and environmental, ecological and health risks of these elements. Only As and Ni exceeded the upper continental crust concentrations. Among ten TEs, Ni and As had the highest mean values of enrichment factor (EF) and contamination factor (Cf), indicating that soils showed moderate enrichment and moderate contamination with these elements. Ecological risk factor and ecological risk index values of all samples were <40 and <150, respectively, indicating low ecological risk in the study area. Factor analysis and correlation analysis indicated that Al, Pb, Cr, Cu, Zn, Co, Mn and Fe mainly originated from natural sources, Ni from mixed sources of anthropogenic and lithogenic origins, while arsenic primarily originated from anthropogenic activities. The hazard quotient values for both adults and children did not exceed 1, suggesting that all TEs in soil through ingestion, dermal contact and inhalation pathways had no significant non-carcinogenic risks. Children were more susceptible to non-carcinogenic health effects of TEs in soils. The carcinogenic risk values of As, Co, Cr and Ni were within the acceptable risk range, indicating that carcinogenic risks were not expected.

Atmospheric deposition of hazardous elements and its accumulation in both soil and grain of winter wheat in a lead-zinc smelter contaminated area, Central China

Hazardous elements (HEs) and its deposition from atmosphere have become a major healthy and environmental concern worldwide, however, the risks to food safety of deposited HE are still largely unknown, especially for wheat grains (Triticum aestivum L.). This research was to characterize atmospheric deposition of high HEs [such as lead (Pb), cadmium (Cd) and arsenic (As)] at deposited site (TS) and assess its impacts on the soil and winter wheat accumulation in a lead‑zinc smelter contaminated area of Central China. Results indicated that deposited As, Cd and Pb at TS site were 31.15, 15.94 and 281.86 mg m^-2 during the winter wheat growing season, contributing 86.9%, 81.7% and 80.4% to the annual total, respectively. Most of deposited HEs were retained in top 35-cm soil, resulting in soil Cd concentration above the national soil regulatory limit (0.6 mg kg^-1; GB 15618-2018). The newly deposited HEs could contribute 57.7-88.2% and 16.2-29.1% to total HEs of wheat grains in clean soil based on a soil transplanted experiment and in contaminated soil based on a two-year in-situ experiment, respectively. Moreover, the newly deposited HEs significantly increased HE concentration of wheat grain by 22.9-57.5% in the contaminated soil when an immobilizing amendment were applied (p < 0.05), and grain Cd concentration exceeded the national grain limit (0.1 mg kg^-1; GB 2762-2017). Thus, deposited HE could be accumulated in soil and wheat grain and decrease the remediation effectiveness of passivation amendments in contaminated soils, which would raise a public awareness of HE deposition and provide a scientific data in support of environmental pollution control and remediation.

Cost-effective in-situ remediation technologies for complete mineralization of dyes contaminated soils

Dyes & dyes intermediates are one of the important and critically polluted industrial sectors, generating a large environmental liability. Therefore characterization of microbial community structure and diversity of contaminated soils helps to optimize the bioremediation strategies and performance. This study investigated the roles of environmental variables and contamination levels in shaping microbial community structure at an abandoned aged. In total, 20 bacterial and 4 fungal phyla were identified across soils with different physiochemical properties and concentration of the contaminants. Taxonomic analysis revealed the Proteobacteria, Firmicutes, Ascomycota and Basidiomycota represented the lineages and accounted for 49.5%-51.2%, 5.1%-15.3%, 2.5%-3.8% and 1.6%-2.1% of the total population, respectively. Microbial community (site 1) achieved decolorization rate of 972 ± 1.21 mg dyes kgsoil^-1d^-1 after 15d and 692 ± 1.4 mg kg-soil^-1d^-1 COD removal rate after 30 day of the experiment. Microbial community mineralized intermediates, 4-amino benzenesulfonate, 6-amino naphthalene sulfonate and benzene/naphthalene sulfonate in TCA cycle and stimulate the growth of selected soil bacteria, primary nutrient as well as plant growth of contaminated soil.

Evaluating vanadium bioavailability to cabbage in rural soils using geochemical and micro-spectroscopic techniques

Assessing the vanadium (V) fractionation and speciation to predict its bioavailability using a combined approach of geochemical extractions and micro-spectroscopic techniques is still not well studied. Therefore, we aimed to determine the bioavailability of V in rural soils using single extractants, sequential extraction procedure, and the X-ray absorption near edge structure (XANES) spectroscopy. We collected and characterized ninety four samples originated from horizons of seventeen soil profiles in Taiwan. We determined the total content of V and its geochemical fractions using the BCR sequential extraction procedure to predict its potential mobility. We also assessed the bioavailability of V in the soils using four availability indices i.e., CaCl₂, HCl, ethylenediaminetetraacetic acid (EDTA), and NaHCO₃ and related them to its uptake by Chinese cabbage (Brassica chinensis L.). Additionally, we determined the V speciation by vanadium K-edge XANES spectra. Moreover, we studied the elemental compositions of the soils using Electron Probe Micro Analysis (EPMA). Vanadium was mainly distributed in the residual fraction (81-98% of total V). Among the potential mobile fractions, V was mainly associated with Fe oxides, as identified by the BCR sequential extraction and EMPA. The XANES analysis indicated that V mainly existed in the soils as V(IV) and V(V). The EDTA and NaHCO₃ extracted more V than CaCl₂ and HCl, and both, particularly NaHCO₃ were positively and significantly correlated with the total soil content and plant shoot concentrations of V; therefore NaHCO₃ might be recommended as a bioavailability index for soil V. We hypothesize that the NaHCO₃ may extract vanadate from soil surfaces and also vanadate transformed from vanadyl at alkaline pH during the extraction. The NaHCO₃-extracted V can be predicted by a function of soil total V, CEC, and pH. Our results should be verified using different soils and plants in the future.

Influence of soil characteristics and leaching rate on copper migration: column test

Soil copper (Cu) supply is used to correct Cu deficiency in many crops grown in southern Mediterranean areas. Oversupply of this fertilizer may contaminate soil and groundwater. This study aims to assess Cu migration in different soils of Moroccan agricultural areas. Three soil samples were collected from different areas. For each soil, three annual leaching rates were tested: 35 mm, 237 mm, and 565 mm for a sandy soil; 35 mm, 70 mm, and 140 mm for a clay calcareous soil; and 35 mm, 103 mm, and 247 mm for silty clay soil. The leaching experiments were conducted in columns filled identically up to 30 cm with each soil sample. Then, 0.6 mg of Cu kg⁻¹ was added to the soil surface in the sulfate form (CuSO₄.5H₂O). The results showed that soil Cu loss increased mainly with leaching rate: y = 0.004 x – 0.10 (R² = 0.97) where y: soil Cu loss (10⁻⁴ meq 100 g⁻¹) and x: leaching rate (mm). The regression analysis did not reveal a significant influence of the soil properties on Cu leaching. However, the Cu loss seems insignificant regarding the no recurrence of high annual leaching rate (over 500 mm), in south Mediterranean areas. Also, soil Cu accumulation risk occurred in all studied soils. For sandy soil, available Cu content was 78% higher in the top layer (0–10 cm) than its content in the middle (10–20 cm) and lower (20–30 cm) layers. Furthermore, a release of bioavailable Cu was recorded in silty clay and clay calcareous soils at a leaching rate of over 70 mm.

Chickens bred extensively as sentinels from soil contamination by Toxocara

Environmental contamination by Toxocara spp eggs can be verified by parasitological techniques, which are mostly laborious, have low sensitivity, and may require repeated tests to establish the contamination status of a certain area. Given the significance of this parasite as an agent of infections in humans, that may cause blindness, especially in children, broilers chickens created extensively were evaluated as possible markers of parasite environmental contamination, through the detection of anti-Toxocara serum antibodies. Eighteen 15-day-old Label Rouge broilers were released on a farm with a history of dogs with Toxocara infection. At 0, 15 and 30 days after the release birds blood samples were taken, as well as soil samples. At the end of the experiment the birds were slaughtered, and the gastrointestinal tract was collected for coprological exams. The presence of anti-Toxocara antibodies resulted in increased reactivity indexes with time, and at 15 days five of the birds were positive and at 30 days, seven birds showed seroconversion. Examination of the soil samples by the centrifugation-flotation method in hyper saturated zinc sulfate solution revealed contamination by embryonated or infertile eggs of Toxocara at all times of collection, as well as the presence of Ascaridia eggs at 15 days after release of birds. Examination of bird's stool samples at the end of the experiment demonstrated 100% infection by Ascaridia galli, however there was no correlation between the counts of this parasite and the ELISA reactivity indices for anti-Toxocara antibodies. The results obtained allow us to infer the possibility of using anti-Toxocara spp-specific antibodies determination in birds raised extensively, which could then serve as sentinels of environmental contamination by this parasite.

Seasonal fluctuations of Zn, Pb, As and Cd contents in the biomass of selected grass species growing on contaminated soils: Implications for in situ phytostabilization

Phytostabilization aims to immobilize contaminants at the rhizosphere level using the root system of adapted plants. In order to exploit wild grasses with potential for phytostabilization, a screening throughout the year was conducted at a site contaminated by Pb and Zn. Three plant species were chosen: Agrostis capillaris, Arrhenatherum elatius and Calamagrostis epigeios. Rhizospheric soil and biomass was used for chemical characterization. Above- and below-ground was analyzed. For each sample, arbuscular mycorrhiza fungi colonization was determined. The highest concentrations of Pb were found in the A. capillaris rhizosphere (3417 mg kg^-1), and in A. elatius for Zn (3876 mg kg^-1). CaCl₂-extractable Zn in the rhizosphere of C. epigeios was the lowest and Pb was lower for A. elatius. CaCl₂-extractable Cd was neither species-dependent nor time-dependent. Arsenic was not species-dependent. The fractionation of target elements did not show differences between separate sampling campaigns and Pb was the only element that showed differences during the year. A. capillaris showed the best capacity to take up elements. The colonization by AMF did not show significant differences for different sampling times, or interactions between time and species, however differences were found for different species, i.e., C. epigeios showed significantly lower colonization by arbuscular mycorrhiza fungi. Our results indicate that A. capillaris appears to be a good indigenous candidate for phytostabilization.

Petroleum hydrocarbons degradation in contaminated soil using the plants of the Aster family

Oil extraction is one of the causes of soil contamination with the total petroleum hydrocarbons. The objective of this study was to clarify the effect of Asteraceae plants on the degradation of petroleum hydrocarbon in contaminated soil. Initial soils with 40 and 90 g kg^-1 of total petroleum hydrocarbon (TPH) were prepared. There were three treatments: (1) no addition, (2) addition of FeCl₃ and nitrilotriacetic acid (NTA) solution, and (3) addition of FeCl₃ + NTA and the cultivation of nine Asteraceae plants. The concentration of TPH was measured using infrared spectrophotometer, 2 and 3 months after transplanting (MAT). Shoot and root dry weights were measured 3 MAT. The concentration of TPH in soil cultivated with Cosmos caudatus was lower than that of the initial soil (40 g kg^-1 TPH), 2 MAT. The concentrations of TPH in soils cultivated with Calendula officinalis, Callistephus chinensis, C. caudatus, and Tagetes sp. were also lower than that in the initial soil, 3 MAT. The concentrations of TPH in soils cultivated with Achillea filipendulina, Anthemis tinctoria, Tagetes erecta, Chrysanthemum coronarium, C. officinalis, C. chinensis, and C. caudatus were lower than that in the initial soil (90 g kg^-1 TPH), 2 MAT. The concentrations of TPH in soils cultivated with T. erecta, A. tinctoria, Zinnia elegans, C. chinensis, C. caudatus, and Tagetes sp. were lower than that in the initial soil, 3 MAT. A. filipendulina and C. coronarium died at both 40 and 90 kg^-1 TPH soils. These results suggest that the roots of Asteraceae plants degrade petroleum hydrocarbon in contaminated soil and C. chinensis and Z. elegans are more suitable for using TPH remediation. Plant survival and extensive root system are important factors for the remediation of TPH in contaminated soil.

Sensitivity to Copper and Development of Culturing and Toxicity Test Procedures for the Antarctic Terrestrial Nematode Plectus murrayi

Environmental quality guideline values and remediation targets, specific to Antarctic ecosystems, are required for the risk assessment and remediation of contaminated sites in Antarctica. Ecotoxicological testing with Antarctic soil organisms is fundamental in determining reliable contaminant effect threshold concentrations. The present study describes the development of optimal culturing techniques and aqueous toxicity test procedures for an endemic Antarctic soil nematode, Plectus murrayi, which lives within interstitial waters between soil particles. Toxicity tests were of extended duration to account for the species' physiology and life-history characteristics. Plectus murrayi was sensitive to aqueous copper with a 50% effective concentration for egg-hatching success of 139 µg/L. Hatched juveniles that were first exposed to copper as eggs appeared to be less sensitive than those first exposed at the hatched J2 stage, indicating a potential protective effect of the egg. Sensitivity of juveniles to copper increased with exposure duration, with 50% lethal concentrations of 478 and 117 µg/L at 21 and 28 d, respectively. The present study describes new methods for the application of an environmentally relevant test species to the risk assessment of contaminants in Antarctic soil and provides the first estimates of sensitivity to a toxicant for an Antarctic terrestrial microinvertebrate. Environ Toxicol Chem 2020;39:482-491. © 2019 SETAC.

Prevalence, risk factors and genotype distribution of Toxoplasma gondii DNA in soil in China

In the present study, we performed a cross-sectional survey to determine the occurrence and genotype distribution of T. gondii DNA in soil samples collected from different sources from six geographic regions in China. Between March 2015 and June 2017, 2100 soil samples were collected from schools, parks, farms and coastal beaches, and examined for T. gondii DNA using three PCR assays targeting 529-bp repeat element (RE) sequence, B1 gene and ITS-1 gene sequences. Also, we investigated whether geographic region, soil source and type, and sampling season can influence the prevalence of T. gondii DNA in the soil. Soil samples collected from farms and parks had the highest prevalence, whereas samples collected from school playgrounds and coastal beaches had the lowest prevalence. PCR assays targeting 529-bp RE and ITS-1 gene sequences were more sensitive than the B1 gene-based assay. Positive PCR products were genotyped using multi-locus PCR-RFLP, and ToxoDB #9 was the predominant genotype found in the contaminated soil samples. Multiple logistic regression identified factors correlated significantly with the presence of T. gondii DNA in the soil to be the source of the soil, including farms (odds ratio 3.10; 95% confidence interval [CI], 1.52 to 6.29; p = 0.002) and parks (2.59; 95% CI 1.28 to 5.27; p = 0.009). These results show that Chinese soil hosts T. gondii of the most prevalent genotype in China (ToxoDB#9) and that the soil type influences infection patterns.

Potential of asphalt concrete as a source of trace metals

Asphalt concrete is one of the most important building materials in the modern world, but the leaching potential of metals from this composite material to the environment is poorly understood. In this study, metals leaching from four hot-mix asphalt samples were analyzed: two fresh samples of low-traffic and high-traffic composition and their weathered equivalents collected from roads in the city of Edmonton, Alberta, Canada. A sequential extraction, based on the Community Bureau of Reference method, was applied to study the speciation and potential mobility of metals and metalloids in those samples. Major trace metals identified in all four samples were Mn, P, Ba, Sr, Zn, V, and Ni, with the highest metals concentrations generally found in weathered asphalt concrete. Of the major trace metals, P, Mn, Sr, and Zn were relatively mobile, having large portions of their total concentrations in the exchangeable/acid-soluble and reducible fractions. When considering the most mobile fraction (exchangeable/acid soluble) and using Canada as a model country, up to 180 t P, 440 t Mn, 50 t Ba, 36 t Sr, 11 t Zn, and 0.11-3.2 t of other metals and metalloids (including Cr, Ni, Cu, As, and Pb) could potentially leach from the top layer of Canada's total of paved public roads. To place these amounts into perspective, they were estimated to make up to 22‰ of Canada's annual release numbers into soil, water and air for these same metals and metalloids. However, they are concentrated in a small area around roads and highways, creating the potential for localized soil and groundwater contamination.

Impact of bonfires on soil properties in an urban park in Vilnius (Lithuania)

Lighting bonfires in urban parks is a widespread practice. However, few studies have examined their impact on soil properties. The aim of this study was to analyze the impact of bonfires on the soil properties of an urban park in Vilnius, Lithuania. The properties studied were soil water repellency (SWR), aggregate stability (AS), soil organic matter (SOM) content, total nitrogen (TN), inorganic carbon (IC), pH, electrical conductivity (EC), extractable calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), aluminum (Al), manganese (Mn), iron (Fe), zinc (Zn), copper (Cu), boron (B), chromium (Cr), available phosphorus (P), silicon (Si) and sulfur (S). Soil ratios calculated were carbon/nitrogen ratio (C/N), Ca + Mg/(Na + K)^1/2 (SPAR), Ca:Al and Ca:Mg. Three areas were studied: Site 1) Pinus sylvestris L. and Quercus robur L.; Site 2) Aesculus glabra Wild.; and Site 3) Pinus sylvestris L. and Acer plantanoides L. At each site, 20 samples were collected (10 within the bonfire area, 10 from a control area). The results showed significantly higher values of SOM, IC, pH, EC, Ca, Mg, Na, K, P, Al, Zn, Cu, Cr, S, C/N ratio, Ca:Al ratio and Ca:Mg ratio in bonfire soils than in control unburned soils. In bonfire soils, significantly lower values were recorded of SWR, AS, TN, SOM, Al, Mn, Fe, Cr, S and SPAR comparing to control soils. Most affected area by the bonfire was Site 1, which presented a marked increase in heavy metal content comparing to the control. The impact of soil heating was evident in AS, IC, pH, extractable Ca, Mg, Na, K, P, Al, Zn, Cu, Cr, S, and in its ratios. Protective measures are needed to limit bonfires and prohibit the burning of hazardous materials.

Quantitative assessment of exposure of heavy metals in groundwater and soil on human health in Reasi district, Jammu and Kashmir

The assessment of heavy metal contents in environmental sectors is important to estimate the carcinogenic and non-carcinogenic doses and risks for the mankind associated with it. The present work deals with the assessment of the risk exposure related to heavy metal contents in groundwater and soil samples to two different age groups via three different transits, i.e., ingestion, inhalation and dermal. The concentrations of heavy metals (Zn, Cd, Cu, Pb and Cr) were measured in the villages of lower Himalayas of Reasi district by using microwave plasma atomic emission spectrometer. The calculated mean contamination factors of heavy metals in soil samples were as: Zn, 0.73; Cu, 0.70; Pb, 0.74; and Cr, 0.33; which led to pollution load index less than unity. The overall carcinogenic risks have been varied from 6.4E-08 to 5.1E-07 in soil samples and from 7.3E-06 to 1.1E-04 in ground water samples and were found to be well within the range prescribed by USEPA (Screening level ecological risk assessment protocol for hazardous waste combustion facilities, appendix E: toxicity reference values, US Environmental Protection Agency, Washington, D.C., 1999). The mean values of heavy metal contents except lead and chromium in water samples were found to be less than the values prescribed by various agencies. Geo-accumulation Index showed that Pb contribute to the highest contamination (0 < I_geo < 1) among the other heavy metals. Cluster analysis and principal component analysis identified that Zn, Cu, Pb and Cr had a relationship and the presence of these heavy metals could be related to vehicle emissions, traffic sources and industrial sources. The overall mean values of the non-carcinogenic doses and associated hazard risks in soil and water samples calculated for children were found to be higher than the adults which may be due to hand to mouth activities.

Comparable effects of manure and its biochar on reducing soil Cr bioavailability and narrowing the rhizosphere extent of enzyme activities

Chromium (Cr) contamination is especially hazardous to soil biota. Application of manure and biochar has been frequently proposed to remediate Cr-contaminated soil. However, the understanding of mechanisms behind manure and biochar impacts on soil enzyme activities requires advanced visualization technologies. For the first time, we compared manure and its biochar influence on the spatial distribution of β-glucosidase, N-acetyl-glucosaminidase and phosphomonoesterase activities in Cr-contaminated soil using direct zymography. Maize was planted for 45 days in (a) soil mixed with manure, (b) soil mixed with manure-derived biochar and (c) soil without any addition. Soil pH decreased over 45 days, inducing an increase in acid soluble Cr. The concomitant decrease in β-glucosidase and N-acetyl-glucosaminidase activities explained the narrowing rhizosphere extent of enzyme activities by 13-44%, indicating that increased Cr bioavailability decreases microbial activities. A larger maize performance index and the greatest plant shoot/root ratio after biochar application suggested enhanced maize growth (p < 0.05). In contrast, manure induced the narrowest extent of β-glucosidase and phosphomonoesterase activities due to the addition of labile organic compounds and nutrients following its application. Our study emphasizes the importance of pH on Cr bioavailability and enzyme activities and demonstrates that biochar application is more ideally suited for remediating Cr-contaminated soil.

Geochemical fractionation of thallium in contaminated soils near a large-scale Hg-Tl mineralised area

Enriched levels of thallium (Tl) in the environment are not only derived from anthropogenic sources but also have potential natural origins owing to Tl-rich sulphide mineralization. However, little is known regarding the geochemical fractionations of Tl in contaminated soils from geogenic sources. This study aims to reveal the Tl geochemical fractionations in different types of soils from a large-scale independent Tl mine in southwestern China, via a modified Institute for Reference Materials and Measurement (IRMM) sequential extraction (four-step) scheme. The results revealed that a large percentage of Tl was related to the labile portions (including reducible, weak-acid-exchangeable, and oxidizable fraction) of the soils (68.8-367 mg kg^-1). Further analyses by Scanning Transmission Electron Microscopy-Energy Dispersive X-ray Spectrometer (STEM-EDS) found that Tl mainly existed in the Fe-containing minerals (such as jarosite and hematite) with fine particles (∼1 μm). These results highlight that, apart from the anthropogenically induced Tl pollution, the naturally occurring Tl contamination in soils may also pose significant risks to human health and ecological safety. Owing to the relatively high mobility and bioavailability of Tl in the labile fractions, it is important to understand geochemical fractionations of this element for alleviating Tl pollution and effective management of naturally occurring Tl contaminated soils.

Ecological risk assessment of mercury and chromium in greenhouse soils

Very little information is available about Hg and Cr evolution in greenhouse soils. This paper presents the results of determining Hg and Cr in greenhouse soils in a semi-arid region in the southern Iberian Peninsula (Almería, Spain), and assessing the enrichment level and the Potential Ecological Risk Index (PERI) according to crop age. Hakanson's approach was used to evaluate the PERI. To investigate the behaviour of Hg and Cr in greenhouse soils over time, samples were grouped into values in soils for blocks according to crop age: 0 years, 5-10 years, 10-20 years, more than 20 years. The results showed that 74% of GS exceeded the obtained background level (37.1 μg kg^-1) for Hg, with 43% (48.9 mg kg^-1) for Cr. Temporal patterns indicated that these elements are accumulating in greenhouse soils and this trend was very significant for Hg. After more than 20 intensive crop-farming years, concentrations and the PERI had clearly increased. Although the ecological risk was moderate, our observations suggest that the farming practices performed in the last 35 years have allowed these metals to accumulate. In fact, the 15% of the studied soils presented a considerable potential risk and were the soils that had been used longer.

Assessment of sunflower germplasm for phytoremediation of lead-polluted soil and production of seed oil and seed meal for human and animal consumption

Phytoremediation is a valuable technology for mitigating soil contamination in agricultural lands, but phytoremediation without economic revenue is unfeasible for land owners and farmers. The use of crops with high biomass and bioenergy for phytoremediation is a unique strategy to derive supplementary benefits along with remediation activities. Sunflower (Helianthus annuus L.) is a high-biomass crop that can be used for the phytoremediation of polluted lands with additional advantages (biomass and oil). In this study, 40 germplasms of sunflower were screened in field conditions for phytoremediation with the possibility for oil and meal production. The study was carried out to the physiological maturity stage. All studied germplasms mopped up substantial concentrations of Pb, with maximum amounts in shoot > root > seed respectively. The phytoextraction efficiency of the germplasm was assessed in terms of the Transfer factor (TF), Metal removal efficiency (MRE) and Metal extraction ratio (MER). Among all assessed criteria, GP.8585 was found to be most appropriate for restoring moderately Pb-contaminated soil accompanied with providing high biomass and high yield production. The Pb content in the oil of GP.8585 was below the Food safety standard of China, with 59.5% oleic acid and 32.1% linoleic acid. Moreover, amino acid analysis in meal illustrated significant differences among essential and non-essential amino acids. Glutamic acid was found in the highest percentage (22.4%), whereas cysteine in the lowest percentage (1.3%). Therefore, its efficient phytoextraction ability and good quality edible oil and meal production makes GP.8585 the most convenient sunflower germplasm for phytoremediation of moderately Pb-contaminated soil, with fringe benefits to farmers and landowners.

Contamination by As, Hg, and Sb in a region with geogenic As anomaly and subsequent human health risk characterization

Arsenic (As) is among the most harmful toxic elements to human health with severe carcinogenic and non-carcinogenic effects. The present study aims to (1) characterize a site with geogenic As anomaly (Emet basin) in Kutahya, Turkey via soil (urban, agriculture, forest; n = 53 total), water (n = 11), and agricultural product (n = 19) samples; and, (2) characterize human health risks for different receptors under specific exposure scenarios. Soil As levels were very high (range, 22.4-765 mg kg^-1). Previous literature suggested some evidence of Sb and Hg combined with As in mineral forms in the region; the present study found elevated Sb (up to 76.0 mg kg^-1) in two regions with very high As levels, but Hg concentrations were low in the region. Soils from urban/agricultural zones (representing anthropogenic impact) did not have statistically different As levels compared with forest soils (representing low/no human impact). As water concentrations were also very high (range, 14.0-729 μg L^-1), however, uptake by agricultural products was low, mostly limited to wheat (up to 0.7 mg kg^-1). Exposure assessment/risk characterization showed that non-carcinogenic risk following exposure to soils was very high for children (hazard index up to 37 under reasonable maximum exposure) as well as carcinogenic risk (probability up to 1.19E-3). The risk was even higher considering intake of water, and in this case, both for children and adults (HI, 4.0-66.6; cancer risk, 1.29E-4-1.84E-2). The potential adverse outcomes of the As anomaly in the region may be grave, thus further geochemical investigation of As speciation and mobile fractions as well as gastrointestinal As bioaccessibility supplementing probabilistic human health risk characterization are recommended.

Environmental impacts of abrasive blasting of transmission towers in protected areas

In Australia, and other parts of the world, tower infrastructure in electricity transmission networks are nearing the end of their asset life. In changing economic, political and regulatory environments Transmission Network Service Providers are implementing new approaches to asset management and reinvestment, such as refurbishment to extend the life of existing assets, instead of replacement. As part of these refurbishment efforts, abrasive blasting and recoating is being employed to remove corrosion and extend the life of steel electricity transmission towers. New controls and procedures have been developed to manage the most likely impacts associated with the abrasive blasting of transmission towers. However, little or no data have been available on the environmental impacts of abrasive blasting or the effectiveness of management procedures currently being used to mitigate potential adverse environmental impacts.We conducted an integrated study on the impacts of abrasive blasting, which brought together on-site research; modelling; and controlled laboratory trials. The study was undertaken during a transmission tower refurbishment project within the World Heritage listed Wet Tropics Region in Queensland, Australia. Measured metal deposition around towers due to blasting, was primarily as large particles (>PM10) at 12-30 m from the tower. Soil concentrations of metals were highest under towers, with a small number of samples showing elevated zinc at 12-30 m. The presence of spent abrasive media and dust on the geofabric material used under the towers and up to 15 m from the tower base, as part of control measures used to contain the abrasive products, indicates that deposition also occurs between 0 and 12 m from the tower.The potential impacts of the abrasive blasting technique on plants and invertebrates appear to be low. Five species of tropical rainforest tree seedlings exposed to abrasive blasting dust at worst-case levels had no negative impact on physiological performance or plant health. This research will assist Transmission Network Service Providers and other operators of corroded linear infrastructure to plan and implement mitigating management actions and procedures during abrasive blasting projects and assist regulators and the community to better understand the impacts of the practice.