Deriving ecological risk thresholds for soil molybdenum in China based on interspecies correlation estimation and quantitative ion character-activity relationship models.

Soil molybdenum (Mo) levels can reach ecologically hazardous levels. China has not yet established the relevant thresholds, posing challenges for environmental management. Therefore, we present our data relevant to Mo toxicity for several important species. By normalizing soil properties, we obtained a correlation model of Mo toxicity to Hordeum vulgare, as well as 31 models for the toxicity of other elements including Cu and Ni to invertebrates and microbial processes. Using interspecies correlation estimation (ICE) extrapolation, the sensitivity coefficient (0.12-0.71) for five plants were found. For invertebrates and microbial processes lacking Mo data, we used regression analysis to establish Mo toxicity models based on the soil quantitative ion character-activity relationships (s-QICAR; R2 =0.70-0.95) and known toxicities of other metal elements to invertebrate and microbial processes. Furthermore, combining species sensitivity distribution calculations, the HC5 values for protecting 95% of soil species from Mo in three typical soil scenarios in China were calculated. After correction, the predicted no-effect concentrations were 6.8, 4.8, and 3.4 mg/kg, respectively. This study innovatively combined ICE and s - QICAR to derive soil Mo thresholds. Our results can provide a basis for decision-making in the assessment and management of soil Mo pollution.

PlexinA1 promotes gastric cancer migration through preventing MICAL1 protein ubiquitin/proteasome-mediated degradation in a Rac1-dependent manner.

Metastasis promotes the development of tumors and is a significant cause of gastric cancer death. For metastasis to proceed, tumor cells must become mobile by modulating their cytoskeleton. MICAL1 (Molecule Interacting with CasL1) is known as an actin cytoskeleton regulator, but the mechanisms by which it drives gastric cancer cell migration are still unclear. Analysis of gastric cancer tissues revealed that MICAL1 expression is dramatically upregulated in stomach adenocarcinoma (STAD) samples as compared to noncancerous stomach tissues. Patients with high MICAL1 expression had shorter overall survival (OS), post-progression survival (PPS) and first-progression survival (FPS) compared with patients with low MICAL1 expression. RNAi-mediated silencing of MICAL1 inhibited the expression of Vimentin, a protein involved in epithelial-mesenchymal transition. This effect correlates with a significant reduction in gastric cancer cell migration. MICAL1 overexpression reversed these preventive effects. Immunoprecipitation experiments and immunofluorescence assays revealed that PlexinA1 forms a complex with MICAL1. Importantly, specific inhibition of PlexinA1 blocked the Rac1 activation and ROS production, which, in turn, impaired MICAL1 protein stability by accelerating MICAL1 ubiquitin/proteasome-dependent degradation. Overexpression of PlexinA1 enhanced Rac1 activation, ROS production, MICAL1 and Vimentin expressions, and favored cell migration. In conclusion, this study identified MICAL1 as an important facilitator of gastric cancer cell migration, at least in part, by affecting Vimentin expression and PlexinA1 promotes gastric cancer cell migration by binding to and suppressing MICAL1 degradation in a Rac1/ROS-dependent manner.

Mercury pollution risks of agricultural soils and crops in mercury mining areas in Guizhou Province, China: effects of large mercury slag piles.

The historical large mercury slag piles still contain high concentrations of mercury and their impact on the surrounding environment has rarely been reported. In this study, three different agricultural areas [the area with untreated piles (PUT), the area with treated piles (PT), and the background area with no piles (NP)] were selected to investigate mercury slag piles pollution in the Tongren mercury mining area. The mercury concentrations of agricultural soils ranged from 0.42 to 155.00 mg/kg, determined by atomic fluorescence spectrometry of 146 soil samples; and mercury concentrations in local crops (rice, maize, pepper, eggplant, tomato and bean) all exceeded the Chinese food safety limits. Soil and crop pollution trends in the three areas were consistent as PUT > PT > NP, indicating that mercury slag piles have exacerbated pollution. Mercury in the slag piles was adsorbed by multiple pathways of transport into soils with high organic matter, which made the ecological risk of agricultural soils appear extremely high. The total hazard quotients for residents from ingesting mercury in these crops were unacceptable in all areas, and children were more likely to be harmed than adults. Compared to the PT area, treatment of slag piles in the PUT area may decrease mercury concentrations in paddy fields and dry fields by 46.02% and 70.36%; further decreasing health risks for adults and children by 47.06% and 79.90%. This study provided a scientific basis for the necessity of treating large slag piles in mercury mining areas.

Cytoplasmic localization of IRF5 induces Wnt5a/E-cadherin degradation and promotes gastric cancer cells metastasis.

IRF5, a nucleoplasm shuttling protein, is a pivotal transcription factor regulating immune system activity. It's well known that immunosuppression is involved in the development of gastric cancer. However, no data exist for the expression and function of IRF5 in gastric cancer. This study demonstrated that IRF5 was cytoplasm-enriched in gastric cancer cells. IRF5 promoted gastric cancer cell migration, which involved the inhibition of Wnt5a and E-cadherin proteins expression. IRF5 (LA) localized in nucleus had no significant effect on Wnt5a and E-cadherin expressions, while mutation of IRF5 (ΔNLS), which prevents IRF5 nuclear translocation, had more impact on these inhibitory effects. In addition, degradation rates of both Wnt5a and E-cadherin were enhanced by resiquimod, an IRF5 agonist. Further in vivo experiments indicated that IRF5 knockout of gastric cancer cells repressed their pulmonary metastasis in nude mice. Finally, the expression and clinical significance of IRF5 were analyzed using gastric cancer tissue microarrays, which suggested that the expression of IRF5 varied procedurally in different progressive stages of gastric cancer. Our data revealed that IRF5 cytoplasmic localization were associated with Wnt5a and E-cadherin degradation and gastric cancer cell metastasis. Inhibiting IRF5 expression and/or its cytoplasmic localization may provide a novel target for gastric cancer therapy.

Incorporating soil mercury species and fractions into multi-objective risk assessment of a residue disposal site in China.

Environmental problems in soil and water caused by solid waste dumps have become a growing concern. This study proposes an integrated risk assessment model aimed at multi-objectives including human, ecology and groundwater and develops remediation target values at different tiers associated with soil mercury species and fractions in a typical residue disposal site of China. The results show that the residue disposal site was severely contaminated with mercury, with the maximum mercury content in the soil reaching 579.14 mg/kg. The average concentration of vapour mercury, bioaccessible mercury, bioavailable mercury and leachable mercury tested in laboratory was 87.65 mg/kg, 3.15 mg/kg (intestinal phase), 1.654 mg/kg and 0.045 mg/L, respectively. The hazard index calculated using total mercury, bioaccessible mercury and vapour mercury was 7.43 E + 01, 4.42 E + 01, and the remediation target values were7.79 mg/kg and 13.1 mg/kg, respectively. The ecological risk for total mercury and bioavailable mercury was calculated using measured site soil mercury background values of 6390.92 and 94.52, and the remediation target was 0.7 mg/kg and 47.33 mg/kg, respectively. Under Class IV water conditions, the measured and three-phase equilibrium model simulations of leachable mercury resulted in remediation targets of 6 mg/kg and 10 mg/kg for soil mercury. Compared to total mercury, the remediation target values calculated using mercury species and fractions were significantly larger under human health protection, ecology protection and groundwater protection. This results in a reduction in the area of soil to be remediated by 20.3-85.7%, resulting in significant savings in remediation costs. It was concluded that when conducting risk assessment and reuse of mercury-contaminated sites, it is important to consider the species and fractions of mercury in the soil in order to reasonably determine the remediation criteria and scale of remediation to avoid over-remediation and incomplete remediation. At the same time, a comprehensive protection target remediation mechanism should be established by combining different receptors.

Comprehensive Analysis of MICALL2 Reveals Its Potential Roles in EGFR Stabilization and Ovarian Cancer Cell Invasion.

Molecules interacting with CasL (MICALs) are critical mediators of cell motility that act by cytoskeleton rearrangement. However, the molecular mechanisms underlying the regulation of cancer cell invasion remain elusive. The aim of this study was to investigate the potential role of one member of MICALs, i.e., MICALL2, in the invasion and function of ovarian cancer cells. We showed by bioinformatics analysis that MICALL2 expression was significantly higher in tissues of advanced-stage ovarian cancer and associated with poor overall survival of patients. MICALL2 was strongly correlated with the infiltration of multiple types of immune cells and T-cell exhaustion markers. Moreover, enrichment analyses showed that MICALL2 was involved in the tumor-related matrix degradation pathway. Mechanistically, MMP9 was identified as the target gene of MICALL2 for the regulation of invadopodium formation and SKOV3, HO-8910PM cell invasion. In addition, EGFR-AKT-mTOR signaling was identified as the downstream pathway of MICALL2 in the regulation of MMP9 expression. Furthermore, MICALL2 silencing promoted EGFR degradation; however, this effect was abrogated by treatment with the autophagy inhibitors acadesine and chloroquine diphosphate. Silencing of MICALL2 resulted in a suppressive activity of Rac1 while suppressing Rac1 activation attenuated the pro-EGFR, pro-MMP9, and proinvasive effects induced by the overexpression of MICALL2. Collectively, our results indicated that MICALL2 participated in the process of immune infiltration and invasion by ovarian cancer cells. Moreover, MICALL2 prevented EGFR degradation in a Rac1-dependent manner, consequently leading to EGFR-AKT-mTOR-MMP9 signaling activation and invadopodia-mediated matrix degradation.

High MICAL1 expression correlates with cancer progression and immune infiltration in renal clear cell carcinoma.

BACKGROUND: Molecule interacting with CasL 1 (MICAL1), a multidomain flavoprotein monooxygenase, is strongly involved in the biological processes related to cancer cell proliferation and metastasis. However, there were few reports on the clinical significance of MICAL1 in renal clear cell carcinoma. METHODS: The expression and prognostic value of MICAL1 in renal clear cell carcinoma were explored using immunohistochemical assays, public TCGA-KIRC databases and multiple analysis methods, including survival analysis, univariate and multivariate analyses, KEGG and GSEA. Wound healing and Transwell assays were performed to check the 786-O cell and Caki-1 cell migration abilities after knockdown of MICAL1. Western blotting was used to assess the regulatory effect of MICAL1 on the Rac1 activation. Additionally, the function of MICAL1 and the correlations between MICAL1 and immune infiltration levels in KIRC were investigated using TIMER and TISIDB. RESULTS: MICAL1 expression was significantly higher in carcinoma tissue compared with non-cancerous tissue. A survival analysis revealed that patients with high MICAL1 expression had shorter overall survival (OS) and disease-specific survival (DSS) compared with patients with low MICAL1 expression. ROC analysis also confirmed that MICAL1 has a high diagnostic value in KIRC. Importantly, the univariate and multivariate Cox analysis further confirmed that high MICAL1 expression was an independent risk factor for OS in patients with KIRC. In accordance with this, knockdown of MICAL1 expression decreased Rac1 activation and cell migration. KEGG and GSEA analysis revealed that the immune infiltration and Ras signaling pathways were significantly upregulated in the high MICAL1 expression group. In terms of immune infiltrating levels, MICAL1 expression was positively associated with CD8+/Treg cell infiltration levels. Specifically, bioinformatic analysis showed that MICAL1 expression had strong relationships with various T cell exhaustion markers. CONCLUSIONS: MICAL1 expression may act as a prognostic biomarker for determining the prognosis in renal clear cell carcinoma and plays an important role in regulating tumor immune microenvironment and cell migratory capacity.

Effects of the Foliar Application of Water-soluble Chitosan or Na2SiO3 Fertilizer on the Pb Accumulation by a Low-Pb Accumulator Brassica napus Grown on Farmland Surrounding a Working Smelter.

Field experiments were conducted to investigate the effects of two foliar fertilizers, water-soluble chitosan (WSC) and Na2SiO3 (Si), on the accumulation of Pb by a low-Pb accumulator Brassica napus cultivar (QY-1) grown at two mildly Pb-contaminated farmland sites surrounding working smelters in Jiyuan city, Henan province, China. Regardless of the frequency of the fertilizer treatments, the foliar application of WSC (0.01%) or Si (0.15%) significantly increased the QY-1 biomass and decreased the grain Pb concentrations. Compared with the control treatment, spraying plants once with WSC or Si during the flowering period achieved the best effect in the two soils with different pollution, which may be because inhibiting the accumulation of Pb in grains by decreasing the husk-to-grain transfer coefficient. Thus, the foliar application of WSC or Si combined with the cultivation of a low-Pb accumulator is a promising approach for optimizing the utility of Pb-contaminated farmland affected by atmospheric deposition.

MICAL2 contributes to gastric cancer cell migration via Cdc42-dependent activation of E-cadherin/ß-catenin signaling pathway.

BACKGROUND: Gastric cancer is a common and lethal human malignancy worldwide and cancer cell metastasis is the leading cause of cancer-related mortality. MICAL2, a flavoprotein monooxygenase, is an important regulator of epithelial-to-mesenchymal transition. The aim of this study was to explore the effects of MICAL2 on gastric cancer cell migration and determine the underlying molecular mechanisms. METHODS: Cell migration was examined by wound healing and transwell assays. Changes in E-cadherin/ß-catenin signaling were determined by qPCR and analysis of cytoplasmic and nuclear protein fractions. E-cadherin/ß-catenin binding was determined by co-immunoprecipitation assays. Cdc42 activity was examined by pulldown assay. RESULTS: MICAL2 was highly expressed in gastric cancer tissues. The knockdown of MICAL2 significantly attenuated migratory ability and ß-catenin nuclear translocation in gastric cancer cells while LiCl treatment, an inhibitor of GSK3ß, reversed these MICAL2 knockdown-induced effects. Meanwhile, E-cadherin expression was markedly enhanced in MICAL2-depleted cells. MICAL2 knockdown led to a significant attenuation of E-cadherin ubiquitination and degradation in a Cdc42-dependent manner, then enhanced E-cadherin/ß-catenin binding, and reduced ß-catenin nuclear translocation. CONCLUSIONS: Together, our results indicated that MICAL2 promotes E-cadherin ubiquitination and degradation, leading to enhanced ß-catenin signaling via the disruption of the E-cadherin/ß-catenin complex and, consequently, the promotion of gastric cell migration. Video Abstract.

Characteristics, sources and risk assessments of heavy metal pollution in soils of typical chlor-alkali residue storage sites in northeastern China.

In this study, thirty-four soil samples from a typical chlor-alkali slag residue storage site near the city of Qiqihar in northeastern China were collected and their arsenic, cadmium, chromium, copper, mercury, nickel, lead and zinc concentrations were determined. Sources of these heavy metals were analyzed with a positive matrix factorization model, and the health risks associated with different pollution sources were calculated. The results showed that mercury was the main heavy metal pollutant at the site (maximum concentration of 112.19 mg.kg-1) and the soil was also contaminated with arsenic, copper and lead. The sources of eight heavy metals were: mixed oil refinery wastewater and parent material (arsenic, chromium, copper and lead), vinyl chloride waste source (mercury), parent material (cadmium, nickel and zinc). The average potential ecological risk of the soil was 22344.39, with vinyl chloride waste source contributing 99.85% of this risk. The average carcinogenic risk of a mixture of oil refinery wastewater and parent material for children and adults was 9.06×10-6 and 6.36×10-6, respectively, accounting for 99.9% (children) and 99.48% (adults) of the total average carcinogenic risk. The average hazard index of vinyl chloride waste source for children and adults was 0.6 and 0.38, respectively, which accounted for 64.13% (children) and 52.34% (adults) of the total hazard index. These results provide a reference for soil pollution risk assessments at this type of site.

International student perceptions of online medical education during the COVID-19 epidemic.

This study aimed to investigate how international students enrolled on medical and surgical bachelor's degree programs (MBBS) in China perceived online medical education course, compared to native Chinese students during the Covid-19 pandemic. The perceptions of 38 MBBS and 31 Chinese sophomores were surveyed using the Chaoxing platform. The international student group's mean satisfaction with online teaching was 2.737 on a 5-point scale, much lower than the Chinese students' mean score of 4.355 (p < 0.05). Similarly, the international students expressed less satisfaction than the Chinese learners with other aspects of the course, including the teacher's level, at 3.964 ± 0.818 versus 4.445 ± 0.548 (p < 0.05); curriculum organization, at 3.651 ± 0.848 versus 4.333 ± 0.568 (p < 0.05); and self-learning level, at 3.634 ± 0.996 versus 3.686 ± 0.949 (p > 0.05), respectively. There were also noteworthy differences between the progress made by the international students in Chinese language learning, which was positively correlated with satisfaction with teaching on the online medical education (p < 0.05). The results suggest that, while online teaching was a necessary response to the Covid-19 pandemic, satisfaction with this mode of education is lower among international students than their Chinese counterparts.

High MICAL-L2 expression and its role in the prognosis of colon adenocarcinoma.

BACKGROUND: MICAL-like protein 2 (MICAL-L2), a member of the molecules interacting with CasL (MICAL) family of proteins, is strongly associated with the malignancy of multiple types of cancer. However, the role of MICAL-L2 in colon adenocarcinoma (COAD) has not been well characterized. METHODS: In this study, we analyzed the role of MICAL-L2 in COAD using datasets available from public databases. The mRNA and protein expression of MICAL-L2 was investigated using TCGA, UALCAN, and independent immunohistochemical assays. Overall survival (OS) and disease-specific survival (DSS) of COAD patients were assessed based on the MICAL-L2 expression level using the Kaplan-Meier method. Univariate and multivariate analysis was employed to determine whether MICAL-L2 could serve as an independent prognostic indicator of OS. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and gene set enrichment analysis (GSEA) were further utilized to explore the possible cellular mechanism underlying the role of MICAL-L2 in COAD. In addition, the correlation between MICAL-L2 expression and immune cell infiltration levels was investigated via single-sample gene set enrichment analysis (ssGSEA). RESULTS: Data from TCGA, HPA, and UALCAN datasets indicated that MICAL-L2 expression was significantly higher in COAD tissue than in adjacent normal tissues, and this was confirmed by immunohistochemical assays. Kaplan-Meier survival analysis revealed that patients with MICAL-L2 had shorter OS and DSS. Furthermore, multivariate Cox analysis indicated that MICAL-L2 was an independent risk factor for OS in COAD patients. ROC analysis confirmed the diagnostic value of MICAL-L2, and a prognostic nomogram involving age, M stage, and MICAL-L2 expression was constructed for OS. Functional enrichment analyses revealed that transport-related activity was closely associated with the role of MICAL-L2 in COAD. Regarding immune infiltration levels, MICAL-L2 was found to be positively associated with CD56bright NK cells. CONCLUSIONS: Our results suggested that MICAL-L2 is a promising biomarker for determining prognosis and correlated with immune infiltration levels in COAD.

Water-soluble chitosan and phytoremediation efficiency of two Brassica napus L. cultivars in cadmium-contaminated farmland soils.

Pot and field trials were conducted to investigate Cd uptake and phytoremediation efficiency of two Brassica napus cultivars (QY-1 and SYH) with applied water-soluble chitosan (WSC, Pot: 0, 2% and 4%; Field: 0 and 10 g·m-2) grown in Cd-contaminated soils. The results from the pot and field trials generally showed that WSC treatments significantly increased Cd concentrations in shoot and root tissues by 33.77-159.71% (except for SYH/JY) and 7.42-168.71% of two B. napus cultivars compared with the control (p < 0.05). The uptake of Cd by shoots of SYH was obviously higher than by shoots of QY-1 treated with WSC under pot and field conditions, which was 1.54-2.22 times than that of QY-1 (p < 0.05). The results indicated that 2% WSC treatment significantly increased the water-soluble and acid extractable Cd in rhizosphere soils of both B. napus cultivars. Furthermore, Cd concentrations in the oils of two B. napus cultivars with applied WSC (10 g·m-2) grown under field conditions were not significantly different from commercial rapeseed oils. Rapeseed oil of B. napus is not only an edible oil with high nutritional value, but it can also be converted into biomass diesel that can be used as a substitute for petroleum diesel.

Antimony Immobilization in Primary-Explosives-Contaminated Soils by Fe-Al-Based Amendments.

Soils at primary explosives sites have been contaminated by high concentrations of antimony (Sb) and co-occurring heavy metals (Cu and Zn), and are largely overlooked and neglected. In this study, we investigated Sb concentrations and species and studied the effect of combined Fe- and Fe-Al-based sorbent application on the mobility of Sb and co-occurring metals. The content of Sb in soil samples varied from 26.7 to 4255.0 mg/kg. In batch experiments, FeSO4 showed ideal Sb sorption (up to 97% sorption with 10% FeSO4·7H2O), whereas the sorptions of 10% Fe0 and 10% goethite were 72% and 41%, respectively. However, Fe-based sorbents enhanced the mobility of co-occurring Cu and Zn to varying levels, especially FeSO4·7H2O. Al(OH)3 was required to prevent Cu and Zn mobilization. In this study, 5% FeSO4·7H2O and 4% Al(OH)3 mixed with soil was the optimal combination to solve this problem, with Sb, Zn, and Cu stabilizations of 94.6%, 74.2%, and 82.2%, respectively. Column tests spiked with 5% FeSO4·7H2O, and 4% Al(OH)3 showed significant Sb (85.85%), Zn (83.9%), and Cu (94.8%) retention. The pH-regulated results indicated that acid conditioning improved Sb retention under alkaline conditions. However, no significant difference was found between the acidification sets and those without pH regulation. The experimental results showed that 5% FeSO4·7H2O + 4% Al(OH)3 without pH regulation was effective for the stabilization of Sb and co-occurring metals in primary explosive soils.

High expression of S100A2 predicts poor prognosis in patients with endometrial carcinoma.

BACKGROUND: S100A2, a member of the S100 protein family, is abnormally expressed and plays a vital role in multiple cancers. However, little is known about the clinical significance of S100A2 in endometrial carcinoma. METHODS: Clinicopathological data were obtained from The Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx), Gene Expression Omnibus (GEO), and Clinical Proteomic Tumor Analysis Consortium (CPTAC). First, the expression and prognostic value of different S100 family members in endometrial carcinoma were evaluated. Subsequently, the Kaplan-Meier plotter and Cox regression analysis were used to assess the prognostic significance of S100A2, while the association between S100A2 expression and clinical characteristics in endometrial carcinoma was also analyzed using logistic regression. A receiver operating characteristic (ROC) curve and a nomogram were constructed. The putative underlying cellular mechanisms were explored using Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis and gene set enrichment analysis (GSEA). RESULTS: Our results revealed that S100A2 expression was significantly higher in endometrial carcinoma tissue than in non-cancerous tissue at both the mRNA and protein levels. Analysis of Kaplan-Meier plotter data revealed that patients with high S100A2 expression had shorter overall survival (OS) and disease specific survival (DSS) compared with those of patients with low S100A2 expression. Multivariate Cox analysis further confirmed that high S100A2 expression was an independent risk factor for OS in patients with endometrial carcinoma. Other clinicopathologic features found to be related to worse prognosis in endometrial carcinoma included age, clinical stage, histologic grade, and tumor invasion. Importantly, ROC analysis also confirmed that S100A2 has a high diagnostic value in endometrial carcinoma. KEGG enrichment analysis and GSEA revealed that the estrogen and IL-17 signaling pathways were significantly upregulated in the high S100A2 expression group, in which estrogen response, JAK-STAT3, K-Ras, and TNFα/NF-κB were differentially enriched. CONCLUSIONS: S100A2 plays an important role in endometrial carcinoma progression and may represent an independent diagnostic and prognostic biomarker for endometrial carcinoma.

Source Apportionment of Heavy Metals Based on Multiple Approaches for a Proposed Subway Line in the Southeast Industrial District of Beijing, China.

Apportioning the sources of heavy metals (HMs) in soil is of great importance for pollution control. A total of 64 soil samples from 13 sample points at depths of 0-21 m were collected along a proposed subway line in the southeast industrial district of Beijing. The concentrations, distribution characteristics, and sources of eight HMs were investigated. The results showed that the concentrations of Hg, Cd, Cu, Pb, As, and Zn in the topsoil (0-2 m) exceeded the Beijing soil background values. Three sources were identified and their respective contribution rates calculated for each of the HMs using multiple approaches, including correlation analysis (CA), top enrichment factor (TEF), principal component analysis (PCA), and positive matrix factor (PMF) methods. As (63.11%), Cr (61.67%), and Ni (70.80%) mainly originated from natural sources; Hg (97.0%) was dominated by fossil fuel combustion and atmospheric deposition sources; and Zn (72.80%), Pb (69.75%), Cu (65.36%) and Cd (53.08%) were related to traffic sources. Multiple approaches were demonstrated to be effective for HM source apportionment in soil, whilst the results using PMF were clearer and more complete. This work could provide evidence for the selection of reasonable methods to deal with soils excavated during subway construction, avoiding the over-remediation of the soils with heavy metals coming from natural sources.

Safe utilization of cadmium- and lead-contaminated farmland by cultivating a winter rapeseed/maize rotation compared with two phytoextraction approaches.

Compared with phytoextraction, growing suitable crops may be a more profitable and practical approach for managing contaminated farmland, especially when there are multiple pollutants. In this 5-year field study, the phytoaccumulator Hylotelephium spectabile, the high-biomass species amaranth (Amaranthus hypochondriacus), and a winter rapeseed/maize rotation crop were cultivated on farmland contaminated with cadmium (Cd) and lead (Pb). Over 4 consecutive years, the annual Cd uptake and extraction efficiency of H. spectabile was 117.6 g hm-2 and 2.36%, respectively. The Cd extraction efficiency of amaranth was equivalent to that of H. spectabile because of its high biomass, and it extracted more Pb (660-2210 g hm-2) from the soil than did H. spectabile. However, neither of these species was able to remediate contaminated farmland rapidly and inexpensively, even with enhancing strategies such as variety screening and the addition of fertilizers and a chelating agent. A safe utilization approach to cultivate rapeseed instead of wheat significantly reduced the carcinogenic and noncarcinogenic risks. The concentrations of heavy metals in rapeseed oil were below the limits specified in the Chinese national food standard, and the heavy metal concentrations in the byproducts (rapeseed meal and straw) were below the limits specified in Chinese national standards for organic fertilizer and feed. The cost of safe utilization was one-quarter that of phytoextraction, and the net economic benefit was 33.5%-123.5% higher than that of wheat crops. Therefore, the rapeseed/maize rotation is a profitable and feasible approach for the safe utilization of Cd- and Pb-contaminated farmland on the northern plains of China.

[Quantitative Assessment of Human Health Risks Based on Soil Heavy Metals and PAHs Sources:Take a Polluted Industrial Site of Beijing As an Example].

In this study, 130 surface soil samples were collected at an industrial pollution site in Beijing and the contents of As, Be, Cd, Cu, Cr, Hg, Ni, Pb, Sb, Ti, Zn, and 16 PAHs were determined. The positive matrix factorization (PMF) model was used to analyze the sources of heavy metals and PAHs, and the contributions of these sources to carcinogenic risk and hazard index in the study area were calculated. The results showed that the contents of Cd, Cu, Pb, Hg, As, Zn, and Cr in the soil exceeded the background values in different degrees; Cd, Hg, Pb, Zn, and Cu exceeded the background values by>50%. Low molecular weight PAHs (two and three rings) and high molecular weight PAHs (four to six rings) accounted for 39.6% and 60.4% of the total content of 16 PAHs. The PAH content at 77% of the sampling points at the target site was more than 1000 µg ·kg-1, which suggests severe PAH pollution at the site. Heavy metals Be, Ti, As, and Ni mainly originated from natural sources. There are three major sources of 7 heavy metals and 16 PAHs at the site: coal combustion (Hg and ∑16PAHs), smelting (Cu, Cr, Pb, and Zn), and traffic (Sb and Cd). The contribution rates of these sources to the total average contents of seven heavy metals and sixteen PAHs at 130 sampling sites were 8.46% (coal combustion), 90.61% (smelting), and 0.94% (traffic). Human health risk assessment results showed that the carcinogenic risk of seven heavy metals and ∑16PAHs ranged from 4.17×10-6 to 39.38×10-4, and the hazard index ranged from 0 to 32.23. The maximum carcinogenic risk and hazard index values were calculated near the coking plant. Benzo[α]pyrene was the PAH that posed the highest carcinogenic risk and Zn was the heavy metal that had the highest hazard index value. The average carcinogenic risk of coal combustion was 2.16×10-4, accounting for 50.26% of the total average carcinogenic risk. The average hazard index of smelting was 0.834, accounting for 56.43% of the total average non-carcinogenic risk. These two pollution sources are responsible for the high levels of heavy metals and PAHs in the soil of the steel smelting sites that pose the most severe health risks. The results of this study can provide reference for soil remediation and process optimization at other heavily polluted industrial sites.

Peculiar attenuation of soil toluene at contaminated coking sites.

In the soil of contaminated coking sites, polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene and xylene (BTEX) are typical indicator compounds. Generally, PAHs are enriched in the topsoil layer. BTEX, with higher water solubilities and lower organic carbon-water partitioning coefficients (Koc), are distributed deeper than PAHs. However, current models have employed predictions using single compounds to mimic the migration of BTEX at contaminated coking sites. Such models have not considered the influence of the upper soil layer, where PAHs are enriched. An attempt to fill this gap was made by setting up a control soil column experiment in this study. One column was filled with undisturbed soil (column #1) and the other with PAH-contaminated soil (column #2) to simulate the theoretical and actual surface soil layers, respectively. The results showed that in column #2, the toluene gas concentration of the headspace and time required to reach steady state were notably greater than those in column #1. High-throughput sequencing revealed that there were large microbial community structure differences between the two soil columns throughout the experiment, while some genera that degrade toluene with high efficiency emerged noteworthily in column #2. This implied that the upper soil layer enriched with PAHs was conducive to the degradation of toluene vapor. Applying this finding to human health exposure assessment of toluene suggests that the potential exposure level should be reduced from the current predicted level given the unanticipated attenuation at contaminated coking sites.

Heavy metal pollution and human health risk assessment at mercury smelting sites in Wanshan district of Guizhou Province, China.

The Wanshan district of Guizhou Province has a long history of mercury mining and smelting. Previous studies have been carried out on heavy metal (HM) pollution in the soil around Wanshan (such as in urban and farmland areas), but these studies have not been conducted at mercury smelting sites. In this study, the distribution characteristics of As, Be, Cd, Cr, Cu, Hg, Ni, Sb, Pb and Zn and their sources in the shallow stratum (<10 m) of the mercury smelting site in the Wanshan district were analyzed. Human health risks were evaluated using deterministic risk assessment (DRA) and probabilistic risk assessment (PRA) models. The contribution rates of different HM sources to human health risks were also calculated. The maximum HM concentration in mercury smelting site soil occured in the shallow soil (0-1 m), and the concentration sequences were as follows: 358.51 mg kg-1 (Hg) > 248.6 mg kg-1 (Zn) > 67.42 mg kg-1 (As) > 59.04 mg kg-1 (Ni) > 57.56 mg kg-1 (Pb) > 49.59 mg kg-1 (Cr) > 46.65 mg kg-1 (Sb) > 15.65 mg kg-1 (Cu) > 2.02 mg kg-1 (Be) > 0.78 mg kg-1 (Cd). The variable coefficients (CVs) were 1.64 (As), 0.67 (Be), 3.15 (Cd), 1.89 (Cr), 0.95 (Cu), 3.08 (Hg), 0.79 (Ni), 1.41 (Sb), 0.68 (Pb) and 1.13 (Zn), respectively. The HM concentrations in deep soils (9 m) still exceed the local background values, suggesting that heavy metals in shallow soil have migrated downward in the site. Three pollution sources identified with the shallow soil (0-1 m) HMs using the positive matrix factorization (PMF) model, were mercury smelting and coal combustion mixed sources (As, Hg and Zn), parent material sources (Ni, Cu, Cr, Cd and Sb) and wastewater discharge sources (Cu and Pb), respectively. DRA indicated that oral ingestion was the main pathway affecting the carcinogenic risk (CR) and hazard quotient (HQ) of heavy metals. The total-CR of twenty-five sampling points is between 1.219 × 10-6 and 3.446 × 10-4, and the total-HQ is between 0.37 and 43.56. PRA results indicated that DRA will underestimate the health risk of all populations in Guizhou Province, especially female, and BWa is the most influential variable for the PRA results. Smelting and coal combustion mixed sources contributed the most CR (99.29%) and with an HQ of 89.38% were the major sources of pollution affecting human health.