Assessing the environmental availability of heavy metals in geogenically contaminated soils of the Sierra de Aracena Natural Park (SW Spain). Is there a health risk?

Environmental assessment of phosphogypsum: A comprehensive geochemical modeling and leaching behavior study

Understanding the variations in the geochemical composition of phosphogypsum (PG) destined for storage or valorization is crucial for assessing the safety and operational efficacy of waste management. The present study aimed to investigate the environmental behavior of PG using different leaching tests and to evaluate its geochemical behavior using geochemical modeling. Regarding the chemical characterization, the PG samples were predominantly composed of Ca (23.03-23.35 wt%), S (17.65-17.71 wt%), and Si (0.75-0.82 wt%). Mineralogically, the PG samples were primarily composed of gypsum (94.2-95.9 wt%) and quartz (1.67-1.76 wt%). Moreover, the automated mineralogy revealed the presence of apatite, fluorine and malladrite phases. The overall findings of the leaching tests showed that PG could be considered as non-hazardous material according to US Environmental Protection Agency limitations. However, a high leachability of elements at a L/S of 2 under acidic conditions ([Ca] = 166.52-199.87 mg/L, [S] = 207.9-233.59 mg/L, [F] = 248.62-286.65 mg/L) is observed. The weathering cell test revealed a considerable cumulative concentration over 90 days indicating potential adverse effects on the nearby environment (S: 8000 mg/kg, F: 3000 mg/kg, P: 700 mg/kg). Based on these results, it could be estimated that the surface storage of PG could have a serious impact on the environment. In this context, a simulation model was developed based on weathering cell results showed encouraging results for treating PG leachate using CaO before its disposal. Additionally, PHREEQC was used to analyze the speciation of major elements and calculate mineral phase saturation indices in PG leaching solutions. The findings revealed pH-dependent speciation for Ca, S, P, and F. The study identified gypsum, anhydrite, and bassanite as the key phases governing the dissolution of these elements.

Phytoaccumulation of trace elements (As, Cd, Co, Cu, Pb, Zn) by Nicotiana glauca and Euphorbia segetalis growing in a Technosol developed on legacy mine wastes (Domingo Rubio wetland, SW Spain)

Sulfidic mine wastes have the potential to generate acid mine drainage (AMD) and release acid leachates containing high levels of iron, sulfate and potentially toxic elements (PTEs). Soils receiving AMD discharges are generally devoid of vegetation. Only a few metal-tolerant plant species can survive under such adverse soil conditions. This work investigates two plant species, Nicotiana glauca and Euphorbia segetalis, that have successfully colonized an AMD-impacted wetland area in south-western Spain. The uptake of PTEs from the soil by roots and their transfer and accumulation in the above-ground biomass were quantified. Results showed that these pioneer plants grew in patches of neutral soil within the wasteland despite the high concentrations of PTEs in the rhizosphere soil (up to: 613 mg kg-1 As, 18.7 mg kg-1 Cd, 6370 mg kg-1 Cu, 2210 mg kg-1 Pb and 5250 mg kg-1 Zn). The target organs of As, Cu and Pb accumulation were: root > leaf > stem in N. glauca, and root > stem > leaf in E. segetalis. Zinc and Cd showed a significant decrease in roots relative to aerial parts of N. glauca, and Co was preferentially partitioned in stems of N. glauca and leaves of E. segetalis. The soil-plant transfer coefficient values of PTEs in all parts of both plants were well below unity with the only exception of Cd in leaves of N. glauca (1.254), suggesting that roots acted as a barrier limiting the uptake of PTEs by plants. Interestingly, under the same soil conditions, N. glauca absorbed Cd in considerable proportions from soil and accumulated it in its leaves, while E. segetalis was not effective in transferring PTEs from roots shoots except for Co. In conclusion, soil pH and plant-related factors greatly influence the stabilization of PTE in the rhizospheric soil and produce inconsistencies in PTE phytoavailability. The findings of this study provide criteria to assist in natural remediation in other legacy contaminated sites worldwide.

Inhibition Roles of Calcium in Cadmium Uptake and Translocation in Rice: A Review

Cadmium (Cd) contamination in rice grains is posing a significant threat to global food security. To restrict the transport of Cd in the soil-rice system, an efficient way is to use the ionomics strategy. Since calcium (Ca) and Cd have similar ionic radii, their uptake and translocation may be linked in multiple aspects in rice. However, the underlying antagonistic mechanisms are still not fully understood. Therefore, we first summarized the current knowledge on the physiological and molecular footprints of Cd translocation in plants and then explored the potential antagonistic points between Ca and Cd in rice, including exchange adsorption on roots, plant cell-wall composition, co-transporter gene expression, and transpiration inhibition. This review provides suggestions for Ca/Cd interaction studies on rice and introduces ionomics research as a means of better controlling the accumulation of Cd in plants.

Mobility, bioaccessibility, pollution assessment and risk characterization of potentially toxic metals in the urban soil of Lahore, Pakistan

The present study is based on the measurement of potentially toxic metal contents employing various extraction methodologies aimed at the evaluation of their mobility, bioaccessibility and bioavailability in the urban soil (n = 56) of Lahore, Pakistan. Selected metal levels in the soil were quantified using flame atomic absorption spectrometry. On the average basis, aqua regia and glycine extracts revealed comparatively higher contents for most of the metals; average concentrations of Fe, Mn, Zn, Pb, Cu, Cr, Co and Cd were found at 1566, 451.1, 114.8, 52.84, 39.15, 24.82, 12.59 and 3.953 mg/kg in aqua regia extract, while in glycine extract the metal levels were found at 579.6, 174.2, 74.72, 49.74, 19.28, 7.103, 4.692 and 3.357 mg/kg, respectively. However, Cd, Pb, Cu and Zn showed significantly higher mobility and bioavailability in the soil, while Co, Fe and Mn were least mobile/bioavailable. The pollution index was assessed in terms of enrichment factor and modified degree of contamination which revealed severe to significant contamination and anthropogenic enrichment of Cd, Pb, Cu and Zn. Multivariate analysis showed mostly anthropogenic contributions for Zn-Cu-Cr-Pb-Cd. Health risk assessment revealed relatively higher exposure of the metals through ingestion, while only minor contributions were noted for inhalation and dermal contact. Hazard quotient index was within the safe limit (< 1.0) in all soil extractions, thereby indicating no significant non-carcinogenic health risks. The incremental lifetime cancer risk for Cr (4.1E-06) through ingestion was comparatively higher than the safe limit which showed significant lifetime cancer risk to the local population.

Improving biofortification success rates and productivity through zinc nanocomposites in rice (Oryza sativa L.)

Rice (Oryza sativa L.) is a staple food crop; most of it is consumed in nations where malnutrition is a serious problem, and its enrichment through biofortification can be used to efficiently combat hidden hunger. Here, we studied the effect of two zinc forms, i.e., zinc oxide nanoparticles (ZnO NPs) and sulfate salt (ZnSO₄), at four different concentrations during the grain development period (after anthesis and continued once a week for up to 5 weeks) of the rice plant. During the rice growing season 2021-2022, all the experiments were conducted in a greenhouse (temperature: day 30 °C; night 20 °C; relative humidity: 70%; light period: 16 h/8 h, day/night). The main aim was to identify the effects of ZnO NPs on physical growth, biochemical parameters, nutrient acquisition, and crop yield. We have also highlighted the effects of NPs on zinc biofortification, and the end results illustrated that both zinc forms are capable of increasing grain yield. However, we found that even at low concentrations, ZnO NPs showed a significant increase in growth yield, whereas bulk did not show eminent results even at higher concentrations. Spikelet number per panicle was more than 50% and 38% in the case of ZnO NPs and ZnSO₄, respectively. Similarly, stimulation in plant height was 25% with NPs treatment and only 3% with bulk treatment. The increase in grain per spike was 19% with ZnO NPs as compared to the control. Total chlorophyll, soluble sugar, amylose, and soluble protein contents were enhanced under ZnO NP treatment, which plays an excellent role in the regulation of various transcriptional pathways related to biofortification. We identified that foliar application at the flowering stage is more effective in comparison to the basal and tillering stages of the rice life cycle. ZnO NPs increased zinc content in rice grain by 55% as compared to traditional fertilization (~ 35%), with no adverse effects on human health. This study highlights that ZnO NPs could be used to increase zinc efficiency and as a safe fertilizer in the rice harvesting ecosystem.

A typical case study from smelter-contaminated soil: new insights into the environmental availability of heavy metals using an integrated mineralogy characterization

Mineralogy was an important driver for the environmental release of heavy metals. Therefore, the present work was conducted by coupling mineral liberation analyzer (MLA) with complementary geochemical tests to evaluate the geochemical behaviors and their potential environmental risks of heavy metals in the smelter contaminated soil. MLA analysis showed that the soil contained 34.0% of quartz, 17.15% of biotite, 1.36% of metal sulfides, 19.48% of metal oxides, and 0.04% of gypsum. Moreover, As, Pb, and Zn were primarily hosted by arsenopyrite (29.29%), galena (88.41%), and limonite (24.15%), respectively. The integrated geochemical results indicated that among the studied metals, Cd, Cu, Mn, Pb, and Zn were found to be more bioavailable, bioaccessible, and mobile. Based on the combined mineralogical and geochemical results, the environmental release of smelter-driven elements such as Cd, Cu, Mn, Pb, and Zn were mainly controlled by the acidic dissolution of minerals with neutralizing potential, the reductive dissolution of Fe/Mn oxides, and the partial oxidation of metal sulfide minerals. The present study results have confirmed the great importance of mineralogy analysis and geochemical approaches to explain the contribution of smelting activities to soil pollution risks.

Long-Term Sustainability of Marble Waste Sludge in Reducing Soil Acidity and Heavy Metal Release in a Contaminated Mine Technosol

A field-based experiment was set up to evaluate the effectiveness of a single application of marble waste sludge (MWS) on chemical immobilization of potentially hazardous trace elements (PHE) within the soil profile of a mine Technosol under natural assisted remediation for 12 years. Results showed that MWS amendment significantly reduced soil acidity and PHE mobility compared to unamended soil, thus improving soil health and plant growth. The amendment application had a sustained acid-neutralizing action, as soil pH remains relatively constant at between 5.8 and 6.4 throughout the entire profile (70 cm depth). In addition to diluting pollutants, the treatment triggered a redistribution of trace elements among the various operationally defined geochemical pools, shifting the PHE speciation from water-soluble forms to fractions associated with carbonates (29% Cd), metal oxides (40–48% Zn, Cd, Cu, and Ni), organic matter (22% Cu and Ni), and insoluble secondary oxidation minerals and residual phases (80–99% As, Cr, Sb, Tl, and Pb), thereby effectively limiting its potential environmental significance. MWS treatment to immobilize PHE in the contaminated mine Technosol was effective and persistent while in the untreated soil metal release is continuing over time.

Enrichment and environmental availability of cadmium in agricultural soils developed on Cd-rich black shale in southwestern China

The enrichment of cadmium (Cd) in black shale-derived soils is of increasing concern due to its wide occurrence, high Cd concentrations, and potential risks. However, characteristics of enrichment and environmental availability of Cd in these soils are not well understood, which has restricted pollution control and land management. In this study, agricultural soils with elevated Cd concentrations resulting from weathering of Cd-bearing black shale in southwestern China were collected and analyzed. The results showed that Cd could be retained in soils through mechanical inheritance and/or associated with secondary minerals and organic materials. Cd concentrations in soils of the study area ranged between 0.83 and 21.6 mg/kg (average of 5.20 mg/kg), exceeding the risk screening value for agricultural land in China. The heterogeneity of Cd in these soils was highly related to geochemical composition of parent rock and other natural factors. The 0.01 M CaCl₂ and 0.05 M EDTA extraction showed that Cd in these soils had high environmental availability and potential risks. Mobile Cd pool (CaCl₂ extractable Cd, average: 0.24 mg/kg) accounted for 0.07-38.9% of the total Cd, depending on soil pH. Mobilizable Cd pool (EDTA extractable Cd, average: 2.18 mg/kg) accounted for 22.0-100%. These results showed the significance of geochemical background on enrichment of Cd in soils, documented high environmental availability of Cd in black shale-derived soils, and influence of soil pH.

Predicting the relative oral bioavailability of naturally occurring As, Cd and Pb from in vitro bioaccessibility measurement: implications for human soil ingestion exposure assessment

Chestnut soils developed over mineralized areas of southwestern Spain are characterized by high baseline concentrations of geogenic trace elements, notably Pb (up to 14,562 mg kg^-1), As (up to 346 mg kg^-1) and Cd (up to 319 mg kg^-1), which could pose an unacceptable risk to the health of the hand-harvest workers who are being exposed to surface soil by incidental ingestion and dermal contact. Oral bioaccessibility, as determined by simulating the human digestion process in a test-tube environment (Unified BARGE Method), followed the increasing order of As (3.1%) < Pb (21.5%) < Cd (35.6%) in the gastric phase, and As (3.4%) < Pb (4.5%) < Cd (13.2%) in the gastrointestinal extract. Relative bioavailability (RBA) of As (3.1-2.1%), Pb (17.8-17.5%) and Cd (34.4-23.3%), predicted from in vitro bioaccessibility measurement through linear regression models, seems to be influenced not only by the pH and composition of digestive solutions but also by geochemical partitioning of trace elements among the soil constituents. The integration of RBA data in the risk calculations had a considerable effect on the site-specific risk estimations. After RBA adjustment, the level of carcinogenic risk associated with As exposure (< 1.5E-06) and the hazard index for non-carcinogens (< 0.4) was within the regulatory limits, indicating that occupational risks are not of concern. Hence, it can be concluded that the use of a default value of 100% for bioavailability may dramatically overestimate the chronic exposure to geologically sourced trace elements.

Effect of ZnO nanoparticles on the productivity, Zn biofortification, and nutritional quality of rice in a life cycle study

Zinc oxide nanoparticles (ZnO NPs), have been commonly used in agriculture, and have attracted more attention for researchers. In this study, a 2-year experiment was conducted involving two Zn types (ZnO NPs and ZnSO₄), two concentrations of Zn (25 and 100 mg kg^-1), and three Zn application stages (basal stage, tillering stage, and panicle stage). This study comprehensively evaluated the effects of ZnO NPs on rice yield, nutrient uptake, Zn biofortification and grain nutritional quality. Our results showed that both ZnO NPs and Zn salt increased grain yield, NPK uptake, and grain Zn concentration. ZnO NPs application enhanced NPK content in rice, with subsequence increasing panicle number (3.8-10.3%), spikelet number per panicle (2.2-4.7%), and total biomass (6.8-7.6%), thereby promoting the rice yield. Compared with conventional fertilization, ZnO NPs enhanced Zn concentration of brown rice by 13.5-39.4%, this had no negative impact on human health. ZnO NPs application at panicle stage have a higher effectiveness in improving Zn concentration of brown rice than at basal and tillering stage. Furthermore, the application of ZnO NPs at panicle stage was more efficient in increasing Zn concentration of brown rice than for Zn salt. ZnO NPs application slightly altered the amino acids content of rice grains, but had no significant impact on total amino acids content. This study highlights that ZnO NPs could be used as a high performance and safe Zn fertilizer in rice production ecosystem.

Pollution status and health risk caused by heavy elements in the flooded soil and vegetables from typical agricultural region in Vojvodina Province, Serbia

The investigation conducted in the Vojvodina Province, as a typical European and one of the biggest agricultural regions in the Balkans, offers the research methodology that could be used for any non/flooded agricultural region. The flood impact on heavy elements (HE) content in the flooded arable soil (n = 16) in relation to the control soil (n = 16) was examined, as well as their accumulation in the most often cultivated vegetables (n = 96) in the studied area. Results revealed that the flood did not significantly change the pseudo total HEs concentration in the soil as well as their amounts accumulated in different soil fractions. In both soils, only the average content of Ni exceeded the maximum permissible values set by Serbian soil quality standard which is in line with the Dutch standard. In comparison with the background values, notable enrichment is found for most of analyzed elements in both soils. Soil pollution status was assessed through several indices indicating that contamination range was in the domain from a moderate to a highly polluted. The principal component analysis demonstrated that soil contamination was probably originated from agricultural/anthropogenic activities (Cd, Cu, As, Pb), apart from Ni, Cr, and Co which came from natural weathering of the parent material. Carcinogenic and non-carcinogenic risks of selected HEs for Serbian population in the investigated region were below the threshold values. The average levels of Pb in investigated potato and carrot samples were higher than the maximum allowable concentrations established by EU/Serbian regulation. The total hazard quotients (THQ) of HEs through intake of analyzed vegetables were below the safe threshold (˂ 1), suggesting the absence of adverse health effects.

Methodology for scenario-based assessments and demonstration of treatment effectiveness using the Leaching Environmental Assessment Framework (LEAF)

A methodology for developing scenario-based leaching assessments as part of the Leaching Environmental Assessment Framework (LEAF) is illustrated using a hypothetical management/treatment scenario of contaminated soil from a copper and lead smelter. Scenario assessments refine the process beyond screening-level assessments by considering site- and scenario-specific information about the disposal or utilization environment. LEAF assessments assume (i) granular materials leach at local equilibrium with percolating water, while (ii) monolithic materials (e.g., low permeability solidified/stabilized soils) leach by diffusion-based mass transport toward surrounding contact water. Leaching concentrations, estimated using LEAF leaching test data and estimated or measured scenario information, are compared to threshold values. Demonstration results indicate that leaching from untreated soil is significantly (>10x) greater from solidified/stabilized soil than treated material, except for highly soluble constituents (Cl-, NO3-2) or when constituents have similar equilibrium concentrations in both materials (As, Pb). Comparison between wet and dry environments show that while dry environments lead to lower COPC mass-based rates of leaching, the leaching concentrations may be higher due to lower liquid-to-solid ratios. The presented assessment methodology can be used to evaluate treatment effectiveness when both physical and chemical retention characteristics of the material are altered.

Large-scale evaluation of deposition, bioavailability and ecological risks of the potentially toxic metals in the sediment cores of the hotspot coral reef ecosystems (Persian Gulf, Iran)

Coral reefs of the Persian Gulf are vulnerable to the potentially toxic metals (PTMs) accumulated in the ambient sediments. Nonetheless, few studies have investigated the PTMs pollution and risk in the hotspot coral ecosystems of the Persian Gulf at a large-scale. Hereupon, this study focused on the PTMs contamination, their potential ecological risks, historical depositions, geochemical controls and the plausible pollution sources in the core sediments (0-40 cm) collected from the ten coral ecosystems of the Persian Gulf, Iran. Both total and fraction analysis indicated considerable metal pollution levels. Contamination was steadily decreasing towards the bottom of the sediment core, revealing the impact of a recent anthropogenic input. High metal association with the exchangeable and other mobile fractions was observed, indicating their high bioavailability. Of all the elements analyzed, toxic metals Cd, Hg and As exhibited the highest potential ecological risk (RI). Site rank index (SRI), modified degree of contamination (_mCd), and contamination severity index (CSI) based approaches identified stations ST5, ST9 and ST10 as the most contaminated sites of the study area. The same stations were also found to possess considerable ecological risk. Principal component analysis (PCA) revealed that the stations located in the zone of the highest anthropogenic impact contain pollution sources for all the metals analyzed, whereas areas with low anthropogenic activity are mainly affected by the river runoff and urban emissions.

Human health and ecological risk assessment of heavy metal(loid)s in agricultural soils of rural areas: A case study in Kurdistan Province, Iran

BACKGROUND

Agricultural soils pollution with heavy metal (loid) s (HMs) can create significant ecological and health problems. The aims of present study were to characterize HMs pollution profile of dry farmland soils in rural areas of Kurdistan province in Iran and evaluate potential associated ecological and health risks.

METHODS

Different indices of Geo-accumulation index (I_Geo), Individual contamination factor (ICF), Nemerow composite pollution index (NCPI) and Potential Ecological Risk Index (PERI) were employed to assess the bio-accumulation of the HMs and evaluate associated ecological risks. Human health risks estimated with total hazard index (THI) and total carcinogenic risk (TCR) indices based on ingestion, inhalation and dermal exposure pathways for children and adults.

RESULTS

As, Cd, Cr, Ni and Pb exceeded the soil standards. The spatial maps of the I_Geo showed that As pollution was at severe level in eastern part of the study region. According to the ICF results, the studied soils were extremely contaminated with As, Cd, Cr, Ni and Zn. Furthermore, based on the pollution indices, some of sampling sites were critically polluted by abovementioned HMs. For children and adults groups, the THI values in 13 and 97% of sampling sites were more than 1 and the TCR in 7 and 14% of sampling sites were more than 10^-4, respectively. The farmland soil pollution of the study area by As and Cr were found to be quite serious and dangerous.

CONCLUSION

The findings of this study suggest that further attention should be paid by decision-makers to control the HMs pollution in the agricultural soils of the study area.

Phytostabilization potential of Erica australis L. and Nerium oleander L.: a comparative study in the Riotinto mining area (SW Spain)

Phytostabilization is a green, cost-effective technique for mine rehabilitation and ecological restoration. In this study, the phytostabilization capacity of Erica australis L. and Nerium oleander L. was assessed in the climatic and geochemical context of the Riotinto mining district, southwestern Spain, where both plant species colonize harsh substrates of mine wastes and contaminated river banks. In addition to tolerating extreme acidic conditions (up to pH 3.36 for E. australis), both species were found to grow on substrates very poor in bioavailable nutrients (e.g., N and P) and highly enriched with potentially phytotoxic elements (e.g., Cu, Cd, Pb, S). The selective root absorption of essential elements and the sequestration of potentially toxic elements in the root cortex are the main adaptations that allow the studied species to cope in very limiting edaphic environments. Being capable of a tight elemental homeostatic control and tolerating extreme acidic conditions, E. australis is the best candidate for use in phytostabilization programs, ideally to promote early stages of colonization, improve physical and chemical conditions of substrates and favor the establishing of less tolerant species, such as N. oleander.

Soil accumulation and chemical fractions of Cu in a large and long-term coastal apple orchard, North China

PURPOSE

Coastal orchards, with greater humidity and precipitation, are favorable for fruit production, as well as mildew fungi development, thus becoming hot spots of Cu concentrations in soils due to the use of copper-based fungicides. However, little is known on the variation tendencies of Cu availability and mobility from these soils. This study aims to investigate the accumulation, spatial-temporal distribution, and chemical fractions of soil Cu in one of the largest coastal apple-producing area with over 40-year intensive cultivation in China.

MATERIALS AND METHODS

A total of 104 orchard and 31 farmland topsoil samples were collected from Jiaodong Peninsula, Shandong Province. The total Cu concentration (T-Cu) and major element components (MnO, TiO₂, SiO₂, Fe₂O₃, and Al₂O₃) in the soil were determined by X-ray fluorescence spectroscopy. Available Cu concentration (A-Cu) was extracted with HCl or DTPA. Chemical fractionations of Cu were determined via sequential extraction method. The variation tendencies of T-Cu, A-Cu, Cu available ratio (AR), and chemical fractions with planting duration in the orchards were explored while a cokriging method was selected to predict their spatial distributions. Moreover, Pearson's correlation and multiple linear stepwise regressions were constructed to distinguish the vital factors in controlling Cu availability and mobility from these soils.

RESULTS AND DISCUSSION

The results showed that long-term application of Cu-containing fungicides had increased Cu concentrations in orchard soils (85.77 mg kg^-1) 3.5 times higher than the background value (24.0 mg kg^-1) of local agricultural soils, in which 23.8% existed in the available form. Cu in the weak acid-soluble fraction (F1, 5.0 ± 3.5 %), reducible fraction (F2, 24.7 ± 6.6%), and oxidizable fraction (F3, 18.5 ± 7.8%) in orchard soils increased significantly with increasing planting durations whereas the residual fraction (F4, 51.7 ± 15.4%) exhibited a reverse trend. Total content, available content, and chemical fractions of Cu showed strong spatial heterogeneity. The availability and mobility of Cu in orchard soils were mainly controlled by total Cu content, pH, and soil organic carbon.

CONCLUSIONS

Coastal orchards under warm and humid climate condition in China exhibited higher Cu input, along with acidification and rapid organic carbon turnover in the soils, eventually leading to large accumulation and high mobility of Cu in the soils.

Exploring the bioavailability of nickel in a soil system: Physiological and histopathological toxicity study to the earthworms (Eisenia fetida)

Nickel (Ni) contamination in soils, at high concentrations, is considered to be very common. Knowledge of the total content of Ni is frequently insufficient to estimate environmental risk. Our explored findings showed that the earthworms adding reduced the available Ni, along with the superior performance of HCl than CaCl₂. The bioaccumulation of Ni in earthworms was aggravated with increasing Ni dosage and exposure time. Bioaccumulation factor was significantly correlated with the extractable Ni, which was the most suitable predicting the variations of Ni bioavailability. LC₅₀ of earthworms on 7 and 14 days were 1202.444 mg kg^-1 and 1069.324 mg kg^-1, respectively along with the recovery rate in 500 mg kg^-1 Ni polluted soil reached up to 92.5%. Earthworms' respiration was sensitive presenting a significant dose-effect relationship with the Ni concentration. Five biochemical indices in earthworms were induced along with the relevance of a dose- and time-response pattern. Additionally, histological damage in earthworm's body wall, intestine and seminal vesicles were observed under high level of Ni exposure. Overall, we believe that our current study will open a new window for deeper insights into the potential availability of Ni along with other associated metals on the function of soil ecosystem.

Complementary assessment of As, Cu and Zn environmental availability in a stabilised contaminated soil using large-bore column leaching, automatic microcolumn extraction and DGT analysis

Soil pollution with trace elements is a concerning issue worldwide. Monitoring of soil pollution and remediation protocols need still from valid complementary analytical approaches able to detect changes in speciation and lability of metals in soils (e.g. stabilization or mobility). In this work, we compare three different analytical approaches to assess potential changes in environmental availability of Cu, As and Zn in a Mediterranean polluted soil that was amended with different combinations of iron sulphate and alkaline paper sludge waste. The studied methods were: (i) a standard large-bore flow-through column system (macrocolumn), (ii) an automatic dynamic flow-through microcolumn extraction system, and (iii) the diffusive gradients in thin gels technique (DGT). The three analytical approaches tested showed immobilization of Zn and Cu in contaminated mine soils after co-application of paper sludge and iron sulphate, but they differ quantitatively in terms of As mobility. Interconversion between oxidation states of inorganic As is observed to occur to a larger extent in macrocolumn. Because this may only occur in very specific Mediterranean scenarios (i.e. organic matter application to intermittently flooded mine soils), macrocolumn extraction procedures might not appropriately mimic the environmental availability of As in soils with organic amendments (e.g., paper sludge waste). Microcolumn leaching is the fastest screening tool to ascertain the efficiency of chemical amendments, but DGT is a good alternative with less technical demands.

Pollution and Health Risk Assessments of Potentially Toxic Elements in Soil and Sediment Samples in a Petrochemical Industry and Surrounding Area

The pollution state and health risk assessment of potentially toxic elements (PTE) in soil and sediment samples of the petrochemical industry and its surrounding area are evaluated in this study. The pseudo-total contents of Ba, Cd, Co, Cu, Cr, Mn, Ni, Pb, V, Zn, As, Hg, and Se were measured by inductively coupled plasma–optical emission spectrometry (ICP/OES) in analyzed samples. Instead of determining total content, we performed aqua regia of the samples. The silicate matrix remained, and the quantities of elements that are within the silicate matrix do not represent an environmental danger. The soils from the chlor–alkali plant are highly polluted by Hg (the enrichment factor values were above 6000), and by Cu, Cd, Pb, and Zn, while the sediment samples from the wastewater channel are polluted with Cr, Cd, and Hg. The measured element contents are used for calculating health risk criteria for a composite worker (a worker who is exposed, long-term, during the work day) and for residential people. Hg is the element that mainly contributes to non-carcinogenic risks within the petrochemical area. The highest value of total carcinogenic risk obtained in the sediment sample from the wastewater channel, and the metal that mostly contributes is Cr. The areas closest to the petrochemical industry have higher values of health risk criteria parameters and pollution indices. The areas that are located further to the north and south from the petrochemical industry are less burdened with the analyzed elements, which is significant because the closest city and village are situated in those directions.

Clay mineralogy affects the efficiency of sewage sludge in reducing lead retention of soils

Recent studies have shown the feasibility of using of sewage sludge for the remediation of heavy metal-contaminated soils. However, there are no researches to check the influence of clay mineralogy on the efficiency of the sewage sludge to remediation of contaminated soils with heavy metals. For this purpose, we use two contrasting soils: Oxisol rich in hematite and gibbsite and Inceptisol rich in kaolinite. Thermal-treated sludge was applied to Pb-contaminated soil samples and incubated for 40 days. The soil samples were submitted to seven sequential extractions: soluble-Pb, exchangeable-Pb, precipitated-Pb, organic matter-Pb, Fe and Mn oxide-Pb, gibbsite and kaolinite-Pb, and residual-Pb. The reduction of soluble Pb forms by thermal sludge application was more pronounced in the Oxisol than in the Inceptisol because of the conversion of soluble-Pb into more stable forms, such as precipitated-Pb and oxides-Pb. For Inceptisol was necessary to apply high rates of thermal sludge to reach a significant reduction in soluble-Pb contents. The addition of humic fractions in the form of thermal sludge increased the concentration of organic matter-Pb. In confined area, the use of sewage sludge to reduce the heavy metals levels in soils must be better considered, mainly in more weathered soils.

A critical prospective analysis of the potential toxicity of trace element regulation limits in soils worldwide: Are they protective concerning health risk assessment? - A review

Trace elements (TEs) may have toxic effects to plants and humans; thus, countries and organizations impose maximum allowable regulation limits of their concentrations in soils. Usually such limits are placed in different categories according to soil use, soil properties or based on both attributes. However, some countries have regulation limits irrespective of differentiation in soil properties. In this review, we aimed at collecting TE regulation limits in soils from major countries and organizations around the globe, and critiquing them by assessing potential human health risks in the case of soils attaining the maximum allowable values. We explored the soil-to-human pathway and differentiated among three major exposures from TEs, i.e., residential, industrial and agricultural. We observed the existence of problems concerning TE regulation limits, among which the fact that limits across countries do not regulate the same TEs, not even a minimum number of TEs. This indicates that countries do not seem to agree on which regulation limits of TEs pose a high risk. Also, these regulation limits do not take into account TE mobility to neighbouring environment interphases such as plant, especially edible, and water matrices. Moreover, limits for same TEs are vastly diverse across countries; this indicates that those countries have conflicting information concerning TE-related health risks. Subsequently, we addressed this problem of diversity by quantifying resultant risks; we did that by calculating human health risk indices, taking into consideration the cases in which the highest allowable TE limits are attained in soil. Arsenic limits were found to generate a relatively high hazard quotient (HQ_i, accounting for human intake over the maximum allowable oral reference dose for that same TE), indicating that its risk tends to be underestimated. Other TE limits, such as those of Cd, Cu, Ni, Pb, and Zn typically result in low HQ_i, meaning that limits in their cases are rather overprotective. Our approach reveals the need of reducing diversity in regulation limits by drafting soil legislations of worldwide validity, since risks are common across countries. We suggest that new directions should strategically tend to (a) reduce limits of TEs with underestimated contribution to health risk (such as As), (b) cautiously increase limits of TEs that currently cause minor health risks, (c) quantify TE risks associated with uptake to edible plants and potable water, and (d) consider multi-element contamination cases, where risks are cumulatively enhanced due to TE synergism.

First report of geochemical fractionation distribution, bioavailability and risk assessment of potentially toxic inorganic elements in sediments of coral reef Islands of the Persian Gulf, Iran

Metal contamination is a serious environmental concern in the Middle East. Herein, geochemical fractionation distribution and potential sources of thirteen metals (Fe, Al, Mn, Zn, Cu, Co, Cr, Ni, V, As, Hg, Pb and Cd) were investigated in sediments from ten coral reef Islands in the Persian Gulf, Iran. To properly assess availability and mobility of elements, enrichment factor (EF), pollution load index (PLI), pollution index (PI), contamination index (CI), sediment pollution index (SPI) and ecological risk assessment were provided. Sediment grain size showed an outstanding role in controlling the levels of potentially toxic inorganic elements (PTIEs). The highest values of total organic matter (TOM) were detected in Kharg and Lavan Islands. Different metals fractionation distribution was found across sites. As was noticed in carbonate (F₂), exchangeable (F₁), Fe-Mn oxy-hydroxide (F₃), organic (F₄) and residual (F₅) fractions, Hg primarily associated with F₂ and F₁, whereas Pb and Cd with F₂, followed by F₁, F₃, F₅ and F₄. Conversely, Ni and V accumulated in F₁, suggesting their high mobility and bioavailability, and thus environmental risk to aquatic biota. All metals (except Al, Fe and As) had geological and anthropogenic sources. Based on modified risk assessment analysis, the sediments from Kharg, Lavan, Siri and Lark Islands showed medium adverse effects. Overall, results from this study corroborate that petroleum industry is the main source of pollution of PTIEs in the Persian Gulf, and offer a scientific basis for monitoring and preventing metal pollution in the environment.

An experimental design for the optimization of the extraction methods of metallic mobile fractions from environmental solid samples

The evaluation of the cadmium and lead mobile forms from environmental solid samples provides information about their mobility and bioavailability. In the present study, the Cd and Pb mobile fractions were obtained by two modified extraction methods applied to industrial and acidic pH soils or to polluted sediments. In order to highlight that the extraction procedure does not significantly influence the quantitative atomic absorption spectrometric determination of cadmium and lead, the robustness of the extraction methods was evaluated and proven applying a Youden and Steiner factorial design. Within this experimental design, the shaking rate, the shaking time, and the solid/liquid extraction ratio were modified. The measurement uncertainty of the whole analytical procedure was assessed, the contribution of the factors involved in the extraction process being insignificant compared to the other uncertainty sources. The importance of the study is related to the fact that it proves the applicability in the routine laboratory practice of the modified extraction methods by increasing the extraction ratio following thorough optimization and robustness studies.

Temporal variations and spatial distributions of heavy metals in a wastewater-irrigated soil-eggplant system and associated influencing factors

Heavy metal pollution in farmlands is highly concerned as crops' easy-uptake of heavy metal can ultimately affect consumers. In order to offer suggestions on cultivating safe quality vegetable, specifically eggplant which is widely consumed for its nutritional value and antioxidant activity, a field study was undertaken to investigate the temporal variations and spatial distributions of heavy metals in a wastewater-irrigated soil-eggplant system. In the present study, eggplants were planted in the farmlands of Weichuan village (WC) (relatively unpolluted field), Liangzhuang village (LZ) (moderately polluted field) and Minqin village (MQ) (seriously polluted field) to elucidate their temporal uptake processes of heavy metals described by the sigmoid model. Eggplant tissues from severely polluted farmlands were found with higher heavy metal concentrations and lower yields compared with other two groups. What is more, 25 farmlands along the Dongdagou stream (heavy metals polluted stream) were chosen to analyze the spatial distribution of heavy metals in soils and eggplants. Heavy metal concentrations in eggplants decreased with the decline of heavy metal concentrations in soil from upstream (pollution source) to downstream. Moreover, several methods were employed to assess bioavailability of heavy metals in soils. All the bioavailable heavy metals were found in linear positive correlations with heavy metal concentrations. Meanwhile, linear correlations were found between heavy metals in soils and eggplants. At last, redundancy analysis was used to investigate the effects of soil properties (pH, organic matter and texture of soils) and heavy metals on eggplants' uptake. The results indicated that soil heavy metals had a dominant impact on their accumulations in eggplant fruit, with a variance contribution of 78.0%, while soil properties had a regulatory effect, with a variance contribution of 5.2%.

Unraveling the impact of chronic exposure to metal pollution through human gallstones

This study aims to explore the impact of chronic metal exposure derived from persistent pollution from mining activity using human gallstones as proxies. The samples were obtained from patients residing in geologically and environmentally contrasting areas in the Province of Huelva, SW Spain, allowing for the evaluation of the regional effect of metal pollution. The study group resides in the Iberian Pyrite Belt characterized by natural and anthropogenic metal pollution from mining activities, whereas the control group resides in the Ossa Morena Zone famous for its natural parks. A total of 68 gallstones were first classified based on their phase composition and structure and subsequently their chemical composition was studied using solution Inductively Coupled Plasma-Mass Spectrometry. The metal concentrations increased in the cholesterol-rich gallstones from pure, to mixed and composite cholesterol stones along with the increasing amount of minor phases, such as bilirubinate, carbonate, and phosphate. These cholesterol stones did not show an evident enrichment tendency. On the contrary, pigment stones, composed of bilirubinate, carbonate, and phosphate phases, were rich in a variety of elements and the regional comparison showed that the pigment stones from the study area were enriched in sulfide-associated metal(loid)s, Mn, Fe, Cu, Zn, Sr, As, Ag, Sb, and Pb with respect to the control group. Inhalation of polluted airborne particulate matter is considered as one of the main exposure routes among the residents of the study area. Additionally, consumption of local water and locally produced food products such as fruit and vegetables and dermal contact may be possible sources of exposure, but no direct connection was observed.

Partitioning and potential mobilization of aluminum, arsenic, iron, and heavy metals in tropical active and post-active acid sulfate soils: Influence of long-term paddy rice cultivation

Drainage of potential acid sulfate soils (PASS) for paddy rice cultivation results in the formation of active acid sulfate soils (AASS) and subsequently post-active acid sulfate soils (PAASS). The drainage of PASS causes severe environmental problems including acidification and metal contamination of soil and water resources. This study examined the vertical distribution and partitioning of Al, As, Co, Cu, Fe, Mn, Ni, Pb, and Zn in six tropical acid sulfate soils representing AASS and PAASS under long-term paddy rice cultivation (>145 years). The bulk soil samples were analyzed for total concentrations of Al, As, Co, Cu, Fe, Mn, Ni, Pb, and Zn. The partitioning of these elements was examined by a sequential extraction procedure. Labile Al is higher in ASS which is associated with low soil pH. During drainage, mobilization of As, Cu, and Pb is limited by coprecipitation with (poorly) crystalline Fe oxides minerals in the topsoil and partly oxidized layer of both soil types. These elements are associated with iron (mono) sulfides in unoxidized layer. When PASS are exposed to air, Co, Mn, Ni, and Zn are leached from the soils and are dominantly associated with iron sulfides in the unoxidized sediments. Labile Mn, Ni, and Zn are elevated in the unoxidized layer of PAASS because these elements are leached from the partly oxidized layers and adsorbed onto soil constituents. Cobalt is probably precipitated or adsorbed onto (poorly) crystalline minerals.

Toxic responses of microorganisms to nickel exposure in farmland soil in the presence of earthworm (Eisenia fetida)

Nickel (Ni)-contamination impairs soil ecosystem, threatening human health. A laboratory simulation of Ni-polluted farmland soil study, in the presence or absence of earthworm, was carried out to investigate the toxic responses of soil microorganisms, including microbial biomass C (MBC), soil basal respiration (SBR), metabolic quotient (qCO₂), urease (UA) and dehydrogenase activities (DHA). Additionally, the variations of Ni bioavailability were also explored. Results manifested that MBC and SBR were stimulated at 50 and 100 mg·kg^-1 of Ni but inhibited by further increasing Ni level, showing a Hormesis effect. Earthworm input delayed the occurrence of a maximum SBR inhibition rate under the combined double-factors of time and dose. No specific effect of Ni concentration on the qCO₂ was observed. UA was significantly suppressed at 800 mg·kg^-1 Ni (P < 0.05 or 0.01), whereas DHA was more sensitive and significantly inhibited throughout all the treatments (P < 0.01), indicating a pronounced dose-response relationship. The addition of earthworm facilitated all the biomarkers above. The time-dependent of dose-effect relationship (TDR) on MBC and SBR inhibition rates suggested that the peak responsiveness of microorganisms to Ni stress were approximate on the 21st day. The bioavailable form of per unit Ni concentration declined with time expanded and concentration increased, and the changeable process of the relative amount of bioavailability was mainly controlled by a physicochemical reactions.

Geostatistical interpolation of available copper in orchard soil as influenced by planting duration

Mapping the spatial distribution of available copper (A-Cu) in orchard soils is important in agriculture and environmental management. However, data on the distribution of A-Cu in orchard soils is usually highly variable and severely skewed due to the continuous input of fungicides. In this study, ordinary kriging combined with planting duration (OK_PD) is proposed as a method for improving the interpolation of soil A-Cu. Four normal distribution transformation methods, namely, the Box-Cox, Johnson, rank order, and normal score methods, were utilized prior to interpolation. A total of 317 soil samples were collected in the orchards of the Northeast Jiaodong Peninsula. Moreover, 1472 orchards were investigated to obtain a map of planting duration using Voronoi tessellations. The soil A-Cu content ranged from 0.09 to 106.05 with a mean of 18.10 mg kg^-1, reflecting the high availability of Cu in the soils. Soil A-Cu concentrations exhibited a moderate spatial dependency and increased significantly with increasing planting duration. All the normal transformation methods successfully decreased the skewness and kurtosis of the soil A-Cu and the associated residuals, and also computed more robust variograms. OK_PD could generate better spatial prediction accuracy than ordinary kriging (OK) for all transformation methods tested, and it also provided a more detailed map of soil A-Cu. Normal score transformation produced satisfactory accuracy and showed an advantage in ameliorating smoothing effect derived from the interpolation methods. Thus, normal score transformation prior to kriging combined with planting duration (NSOK_PD) is recommended for the interpolation of soil A-Cu in this area.

Importance of lithology in defining natural background concentrations of Cr, Cu, Ni, Pb and Zn in sedimentary soils, northeastern Brazil

The sedimentary basins of Recôncavo and Tucano, Bahia, represent the most important Brazilian Phanerozoic continental basin system, formed during fracturing of Gondwana. The northern basin of Tucano has a semiarid climate (Bsh) while the southern basin of Recôncavo has a tropical rainforest climate (Af). The aim of this study was to determine the distribution of trace metals in soils derived from various sedimentary rocks and climates. Soils were collected at 30 sites in 5 geological units at 0-20 cm and 60-80 cm deep under native vegetation. Physical and chemical attributes (particle size distribution, pH, Al, exchangeable bases, organic matter) were determined, as well as the pseudo-total concentrations (EPA 3050 b) and the total concentrations (X-ray fluorescence) of Cr, Cu, Ni, Pb and Zn. The concentrations of metals were overall correlated to soil texture, according to lithologic origin. Shales resulted in Vertisols 30.4 (Zn), 27.2 (Ni), 16.9 (Cu), 7.5 (Cr) and 2.5 (Pb) times more concentrated than Arenosols derived from the sandstones. High Cr and Ni values in clay soils from shales were attributed to diffuse contamination by erosion of mafic rocks of the Greenstone Belt River Itapicuru (from 3 km northwest of the study area) during the late Jurassic. Tropical rainforest climate resulted in a slight enrichment of Pb and Cr, and Ni had the higher mobility during soil formation (enrichment factor up to 6.01). In conclusion, the geological environment is a much more controlling factor than pedogenesis in the concentration of metals in sedimentary soils.

Risk assessment of heavy metals in soil of Tongnan District (Southwest China): evidence from multiple indices with high-spatial-resolution sampling

Assessment of heavy metal (HM) pollution in soil is critical for human health, ecological remediation, and soil conservation. In this study, statistical analyses and geochemical approaches such as enrichment factor (EF), the index of geoaccumulation (Igeo), and potential ecological risk index (RI) were used for characterization and risk assessment of soil HMs through a high-spatial-resolution 385 samples from Tongnan District, an important agricultural practice area in Chongqing Municipality in Southwest China. Igeo and EF indicated that Hg and Cd could be considered as low and moderate polluted, respectively, and others HMs were not a major concern. Comprehensive ecological risk information further demonstrated that the HMs have caused a moderate risk. Principal component analysis (PCA) extracted two principal components (PCs) with eigenvalue >1 explaining about 66.1% of the total variance in the HM data sets, demonstrating major source of anthropogenic activity, phosphate fertilizers, vehicle, and pesticides. These multi-index methods have the capacity of HM assessment in soil, which are useful for soil conservation and ecological remediation.

Arsenic, chromium, molybdenum, and selenium: Geochemical fractions and potential mobilization in riverine soil profiles originating from Germany and Egypt

The fractionation and potential mobilization of As, Cr, Mo, and Se in four floodplain soil profiles collected along the Nile (Egypt) and Wupper (Germany) Rivers were assessed using the BCR sequential extraction procedure. The concentrations of total and the geochemical fractions (acid soluble (F1), reducible (F2), oxidizable (F3), and residual (F4) fraction) of the elements were determined. The Wupper soils had the highest total concentrations (mg kg^-1) of As (378) and Cr (2,797) while the Nile soils contained the highest total Mo (12) and Se (42). The residual fraction of As, Cr, Mo, and Se was dominant in the Nile soils suggesting the geogenic source of the elements in these soils. The residual fraction of As and Mo and the oxidizable fraction of Cr and Se were dominant in the Wupper soils. Among the non-residual fractions (potential mobile fractions; PMF = ∑F1-F3), the oxidizable fraction was dominant for Cr, Mo, and Se in the Nile soils and for Mo in the Wupper soils, while the reducible fraction was dominant for As in both soils. The PMF of As, Cr, and Se was higher in the Wupper than in the Nile soils which might reflect the anthropogenic sources of these elements in the Wupper soils, while the opposite was the case for the PMF of Mo. The high PMF of Se (87%), Cr (87%), and As (21%) in the Wupper soils suggested that a release of these toxic elements may happen which increase the potential environmental risks in the anthropogenically polluted soils.

Spatial health risk assessment and hierarchical risk management for mercury in soils from a typical contaminated site, China

Due to rapid urbanization and the implementation of ecological civilization construction in China, many industrial factories have been closed or relocated. Therefore, numbers of contaminated sites were generated with contaminated soils which may pose a risk to receptors living nearby. This study presented a spatial health risk assessment and hierarchical risk management policy making for mercury (Hg) in soils from a typical contaminated site in the Hunan Province, central China. Compared with the second class value (0.3 mg/kg) of the Chinese Environmental Quality Standard for Soils, the mean concentrations of Hg in the three soil depths exceeded the second class value. The non-carcinogenic risk of Hg probably posed adverse health effects in 41, 30 and 36 % of the surface soil, the moderate soil and subsoil, respectively, under a sensitive land scenario. The non-carcinogenic risk temporarily posed no adverse health effects in most areas under an insensitive land scenario except for the area around sampling site S29. Spatially, the central, southwest and northeast parts of the contaminated land under a sensitive land scenario should be regarded as the priority regions. For non-carcinogenic effects, the exposure pathways that resulted in the higher levels of exposure risk were ingestion and inhalation of vapors, followed by dermal contact and inhalation of particles. A risk-based integrated risk management policy including the hierarchical risk control values for different soil depths and the calculated remediation earthwork was proposed with consideration of the cost-benefit effect for the related decision-makers.

Heavy metals distribution and risk assessment in soil from an informal E-waste recycling site in Lagos State, Nigeria

Informal E-waste recycling can pose a risk to human health and the environment which this study endeavours to evaluate. The distribution of a number of heavy metals in soil from an informal recycling site in the largest market for used and new electronics and electrical equipment in West Africa was investigated. The potential bioavailability of heavy metals, extent of contamination, potential risk due to the recycling activities and impact of external factors such as rainfall were also assessed. The concentrations of all the heavy metals tested were higher in the area where burning of the waste occurred than at the control site, suggesting an impact of the recycling activities on the soil. The order of total metal concentrations was Cu > Pb > Zn > Mn > Ni > Sb > Cr > Cd for both the dry and wet seasons. The total concentrations of Cd, Cu, Mn, Ni and Zn were all significantly higher (p < 0.001) in the dry season than in the wet season. The concentrations of Cu (329-7106 mg kg^-1), Pb (115-9623 mg kg^-1) and Zn (508-8178 mg kg^-1) were consistently higher than international soil guideline values. Using a sequential extraction method, the potential bioavailability of the heavy metals was indicated as Cd > Sb > Zn > Cu > Ni > Pb > Cr. When the risk was assessed using the Potential Ecological Risk Index (PERI), Cu was found to contribute the most to the potential ecological risk and Cd gave rise to the greatest concern due to its high toxic-response factor within the study site. Similarly, utilising the Risk Assessment Code (RAC) suggested that Cd posed the most risk in this site. This research establishes a high level of contamination in the study site and underscores the importance of applying the appropriate chemical speciation in risk assessment.

Assessment of Cr, Ni and Pb Pollution in Rural Agricultural Soils of Tonalite-Trondjhemite Series in Central India

Chromium (Cr), nickel (Ni) and lead (Pb) contamination was investigated in wheat cultivated rain-fed and irrigated rural agricultural soils (n = 31) of Tonalite-Trondjhemite Series in Central India. The soil sampling was carried out by using stratified random sampling method. The mean concentrations of Cr, Ni and Pb were 54.8, 38.1 and 68.9 mg/kg, respectively. The average values of enrichment factor (EF), geoaccumulation index (I _geo ) and contamination factor (CF) followed the order as: Pb > Ni > Cr. Distribution patterns of soil parent material and weathering processes govern mineral enrichments, irrespective of rainfed or irrigated agricultural practices. Principal component analysis (PCA) showed strong loading of Cr and Ni (PC1) and Pb and clay (PC3). The strong loading on Cr and Ni indicates soils are originating from basic and volcanic rocks in the study area. The strong loading of Pb and clay indicates Pb is strongly adsorbed on clay minerals and Fe-oxides. The cancer risk (CR) index showed negligible carcinogenic risk to the residing population. However, hazard index (HI) values for children exceed the safe limit (HI > 1) for Cr and Pb. Spatial distribution of pollution load index suggest highest pollution in the northeastern part of the district. The study revealed that geogenically enriched soils of the area are suitable for agricultural activities under present conditions.

Combined microstructural and mineralogical phase characterization of gallstones in a patient-based study in SW Spain - Implications for environmental contamination in their formation

This study explores the environmental impact of metal exposure on humans through detailed phase and structural characterization of gallstones from two environmentally contrasting populations in Huelva Province (SW Spain). A total of 42 gallstone samples, obtained after surgical intervention at the Riotinto Hospital, were studied by powder X-ray diffraction (XRD), Fourier Transformed Infra-Red spectroscopy (FTIR), FTIR-μ-ATR (Attenuated Total Reflection) coupled with an optical microscope, and by Environmental Scanning Electron Microscope with Energy Dispersive X-ray Spectroscopy (ESEM-EDS), and subsequently classified according to their phase composition and structure. Additionally, the patients were enquired for their living habits in order to analyze the source of possible exposure to metal contamination. The gallstones were classified into pure, mixed and composite cholesterol stones, black and brown pigment stones, and carbonate stones. The patients from the study group residing in a region with acknowledged metal contamination of both natural and anthropogenic origin have a higher risk of metal exposure through contaminated soil, particle matter in the air, and consumption of local water and food products. According to our findings, the metal exposure is related to a higher tendency of forming black pigment stones in the study group in comparison to the control group residing in a natural park with nearly pristine environmental conditions. Moreover, the gallstones from the study group showed to contain more abundant metal components, such as Cu, Fe, Ni, and Zn, than those from the control group. To our knowledge this is the first study to examine the regional environmental impact of metal exposure on human gallstones.