Potentially toxic metals and the risk to children's health in a coal mining city: An investigation of soil and dust levels, bioaccessibility and blood lead levels.

Coal is a primary energy source in the world. Potentially toxic metals (PTMs) emission from coal mining and combustion are posing a serious public health concern. In order to quantify and evaluate the effect of PTMs on children's health, the concentrations of 12 PTMs (As, Co, Cr, Cu, Mn, Ni, Pb, Sr, Zn, Ca, Fe, and Mg) bound in urban soil and street dust are determined and blood lead levels of these PTMs in 229 children (0-6 years old) are collected from the coal mining city of Yulin, China. In vitro pulmonary bioaccessibilities of PTMs are evaluated by artificial lysosomal fluid and Gamble's solution, and gastrointestinal bioaccessibilities by the unified BAGRE method (UBM); correlations between chemical speciation of PTMs and their bioaccessibility are examined, and children's (0-6 years old) health risks are systematically studied. Similar distribution levels of PTMs are found in soils and dusts, with the most polluted metals being Co, Sr, Ca and Pb. All PTMs (except Cr, Fe) are from the considerable artificial lysosomal fluid extraction both in soil and dust, while Ca and Co are favorably extracted in gastro and intestinal phases than others. Significant correlations are observed between the bioaccessibilities (lung and gastrointestinal) and Fe/Mn hydroxide-bound and carbonate-bound phases, which are key factors influencing and determining PTMs' bioaccessibility. Blood lead levels for children (0-6 years old) are 27.47 (21.65, 33.30) for 0-1 year olds, 32.29 (26.39, 38.19) for 1-2 year olds, 36.99 (28.16, 45.81) for 2-3 year olds, 30.79 (22.56, 39.01) for 3-4 year olds, 27.12 (17.31, 36.93) for 4-5 year olds, 34.59 (24.22, 44.97) for 5-6 year olds and 37.83 (24.15, 51.51) µg/L for 6-7 year olds, respectively, with 3.93%, 3.49%, 4.80%, 2.62%, 1.31%, 1.75% and 1.31% exceeding 50 µg/L, respectively. This indicates that the blood lead levels elevate for 1-2 year and 5-6 year old groups, which should be paid more attention. Although the non-carcinogenic and carcinogenic risks of most PTMs are under the acceptable level, the higher carcinogenic risk of Ni and non-carcinogenic risk of Pb should be monitored continuously. We suggest that further actions will be taken to reduce PTMs exposure for children through sustainable clean and ecological energy technology for coal mining, especially for those infants of 1-2 years old.

Occurrence, fate, and transport of potentially toxic metals (PTMs) in an alkaline rhizosphere soil-plant (Maize, Zea mays L.) system: the role of Bacillus subtilis.

Utilization of microbes is one of the most promising methods to remediate potentially toxic metals (PTMs) from soil. In this study, a systematic investigation was conducted to study the influence of Bacillus subtilis on PTMs occurrence, fractionation, translocation, and accumulation in the rhizosphere soil of Maize (Zea mays L.) in pot experiments. B. subtilis showed strong effects on the fate and mobility of Pb, Sb, Ni, Zn, Cu, and Cr, and it also affected PTMs' distribution in the rhizosphere soil, maize growth, and microbial community structure. Results showed that it was easier for Zn to accumulate in maize roots than other PTMs. According to chemical fractionation, B. subtilis tended to immobilize Pb, Sb, Ni, Zn, and Cu in the rhizosphere soil. Compared with other PTMs, Cr tended to be more available and more mobile, which indicated a higher health risk to the eco-environment. These findings suggested that B. subtilis could be used as a geomicrobiological stabilizer to immobilize PTMs (Pb, Sb, Ni, Cu, Zn) in alkaline soils and decrease their uptake by plants, thus reducing the risks of a potential transfer into the food chain.

Multipotential Toxic Metals Accumulated in Urban Soil and Street Dust from Xining City, NW China: Spatial Occurrences, Sources, and Health Risks.

A total of 155 urban soil and 157 dust samples were collected from Xining city (NW, China) with the objective to systematically investigate the spatial occurrences, sources, and health risk status of potential toxic metals (PTMs) bound in urban soil and street dust. Results established by Geographic Information System tools with inverse distance weighted interpolation technique indicated that the spatial status of 24 multi-PTMs varied with their concentration levels in urban soils and street dusts in monitored local areas. However, they had the similar sources in soil and dust. It was found that Bi, Ga, Nb, Ni, Rb, Sr, Th, U, Y, Zr, As, Mn, Nb, Ti, and V would be possibly predominated by nature material, whereas contamination of Ba, Cr, Cu, Pb, and Zn was clearly related to traffic-related sources. Peculiar associations among Sb, Sn, Ce, and Co were possibly enriched in soil and dust very close to the industrial activities. It was noted that PTMs in urban soil was an important contributor to them in dust. Compared with the potential ecological risk index of all PTMs, Sb posed very high risk. The calculated hazard index and cancer risk of all PTMs suggested the acceptable range both to noncarcinogenic and carcinogenic risk to children and adults except for the case of Cr. However, the noncarcinogenic risk for children was usually higher compared with adults. Although the noncarcinogenic and carcinogenic risk were not significant, the risk of Cr above the threshold for children and adults were observed in most local sites, which should be given more attention.

In vitro bioaccessibility of potentially toxic metals (PTMs) in Baoji urban soil (NW China) from different functional areas and its implication for health risk assessment.

In order to better understand both the conceptual and operational aspects of bioaccessibility and phytobioavailability of PTMs (Co, Cr, Cu, Li, Mn, Ni, Pb, Zn) in different urban soils, a total of 30 soil samples from agricultural region, entertainment district, education area, traffic area, residential area and industrial area (IA) in Baoji urban city (NW China) were collected and the bioaccessibility and phytobioavailability were measured by multi-in vitro models of PBET, SBET, citric acid leaching and Tessier sequential extraction procedure, respectively. The suitable in vitro measurement of bioaccessibility and phytobioavailability for each PTM was selected and would be reliably applied for health risk assessment. The results indicated that the bioaccessibility and phytobioavailability for each PTM evaluated by in vitro models depended on PTM total concentration and anthropologic activity influence. The health risks associated with bioaccessibility of PTMs exposure showed that the carcinogenic and non-carcinogenic risks in all areas for children and adults were below the threshold or acceptable risk levels except lead exposure on children in IA, indicating there were more health risks to the children in than that in other functional areas. It was worth that the highest observation of Pb in IA would strongly correlate with lead-acid battery industries, which the emissions would influence on the occurrences of Pb distributing in the other functional areas, which were supported from the analysis results of XPS. Therefore, the continuous monitoring and attention to the health risk of inhabitants in different functional areas should be paid.

A Novel Pb-Resistant Bacillus subtilis Bacterium Isolate for Co-Biosorption of Hazardous Sb(III) and Pb(II): Thermodynamics and Application Strategy.

The present work is the first to study co-biosorption of Pb(II) and Sb(III) by a novel bacterium and its application strategy. The biosorption characteristics of Pb(II) and Sb(III) ions from aqueous solution using B. subtilis were investigated. Optimum pH, biomass dosage, contact time and temperature were determined to be 5.00, 6.00 mg/L, 45 min and 35 °C, respectively. Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) models were applied to describe the biosorption isotherm of the metal ions by B. subtilis. Results showed that Langmuir model fitted the equilibrium data of Pb(II) better than others, while biosorption of Sb(III) obeyed the Freundlich model well. The biosorption capacity of B. subtilis biomass for Pb(II) and Sb(III) ions was found to be 17.34 ± 0.14 and 2.32 ± 0.30 mg/g, respectively. Kinetic data showed the biosorption process of Pb(II) and Sb(III) ions both followed the pseudo-second-order kinetic model, with R² ranging from 0.974 to 0.999 for Pb(II) and from 0.967 to 0.979 for Sb(III). The calculated thermodynamic parameters, negative ∆G and positive ∆H and ∆S values, indicated the biosorption of Pb(II) and Sb(III) ions onto B. subtilis biomass in water was feasible, endothermic, and spontaneous. Bacterial bioleaching experiment revealed B. subtilis can increase the mobility of Pb(II) and Sb(III) in polluted soil when pH was close to 6 at low temperature. Consequently, B. subtilis, as a cheap and original bacterial material, could be a promising biomass to remove Pb or isolate Sb from industrial wastewater and to assist phytoremediation of Pb and Sb from weak acid or near neutral pH polluted soils at low temperature.

Use of a Survey to Assess the Environmental Exposure and Family Perception to Lead in Children (<6 Years) in Four Valley Cities, Northwestern China.

With the growth of industry, the extensive use of lead, and urban expansion in Northwestern Valley Cities (NVC) China, there is probable reason for presuming an increasing risk of lead exposure. However, little is known about the lead exposure of children less than 6 years old in NVC. As a first investigation, this study uses a survey to systematically determine the influences of various risk factors within the family environment, parents' background, children's behavior, mother's behavior during pregnancy, and parental perception about children's blood lead (CBL). A total of 596 families were recruited from the general population in Urumqi, Lanzhou, Xining and Yan'an. Parents, and their children (<6 years old), were asked about the environment and behaviors which could possibly relate with lead exposure. The results indicated that in the typical NVC of China, children's environment and behavior, parents' education level, and mother's pregnancy behavior, were associated with potential CBL. It was noted that not all parents in NVC China recognized the importance of children's lead exposure. Therefore, children's health care and medical screening campaigns need to be designed to improve family's fundamental knowledge of lead hazards, associated health effects, and prevention in the NVC of China.

Multi-Elements in Source Water (Drinking and Surface Water) within Five Cities from the Semi-Arid and Arid Region, NW China: Occurrence, Spatial Distribution and Risk Assessment.

The purpose of this study was to identify the concentration of multi-elements (MEs) in source water (surface and drinking water) and assess their quality for sustainability. A total of 161 water samples including 88 tap drinking waters (DW) and 73 surface waters (SW) were collected from five cities in Xi'an, Yan'an, Xining, Lanzhou, and Urumqi in northwestern China. Eighteen parameters including pH, electrical conductivity (EC), total organic carbon (TOC) total nitrogen (TN), chemical compositions of anions (F-, Cl-, NO3-,HCO3-, SO42-), cations (NH4⁺, K⁺, Na⁺, Ca2+,Mg2+), and metals (lead (Pb), chromium (Cr), cadmium (Cd), copper (Cu)) were analyzed in the first time at the five cities . The results showed that pH values and concentrations of Cl-, SO42-, Na⁺, K⁺, Ca2+, Mg2+ and Cd, Cr, Cu in DW were within the permissible limits of the Chinese Drinking Water Quality Criteria, whereas the concentrations of other ions (F-, NO3-, NH4⁺ and Pb) exceeded their permissible values. In terms of the SW, the concentrations of F-, Cl-, NO3-, SO42- were over the third range threshold i.e., water suitable for fishing and swimming of the Surface Water Quality Standards in China. The spatial distributions of most MEs in source water are similar, and there was no clear variation for all ions and metals. The metals in DW may be caused by water pipes, faucets and their fittings. The noncarcinogenic risk of metals in DW for local children are in decreasing order Cr > Cd > Pb > Cu. The carcinogenic risk from Cr exposure was at the acceptable level according to threshold of USEPA. Although the comprehensive index of potential ecological assessment of Cr, Cd, Pb and Cu in SW ranked at low risk level and was in the order of Huang River in Xining > Peaceful Canal in Urumqi > Yan River in Yan'an > Yellow River in Lanzhou, their adverse effects to ecology and human health at a low concentration in local semi-arid and arid areas should not be ignored in the long run.