Stabilization of arsenic and antimony Co-contaminated soil with an iron-based stabilizer: Assessment of strength, leaching and hydraulic properties and immobilization mechanisms.

Soils with relatively high concentrations of arsenic (As) and antimony (Sb) in mining areas would impose significant risks to human health and ecosystem. A new stabilizer PFSC composed of polymerized ferric sulfate (PFS) and calcium hydroxide (Ca(OH)2) is proposed to stabilize the soil with co-existed As and Sb sampled at an abandoned arsenic factory site. The effects of stabilizer dosage on the properties of the stabilized soil including leached concentrations of As and Sb, unconfined compressive strength (UCS), and hydraulic conductivity (kw) were investigated. The mechanisms of As and Sb immobilization in the soils were interpreted by Tessier's sequential extraction procedure (SEP), scanning electron microscope (SEM), and X-ray diffraction (XRD) results. The results showed increasing PFSC dosage was effective for reducing leached concentrations of As and Sb. When the PFSC dosage increased from 2% to 10%, the UCS and kw increased from 84 to 206 kPa and decreased from 6.48 × 10-8 to 6.33 × 10-9 m s-1, respectively. Tessier's SEP results showed that the leachable As and Sb fractions decreased from 12% to 5.6% and 7.5% to 3.8%, while the Fe-Mn oxides bound fractions increased from 22.3% to 29.4% and 13.2% to 19.5%. The SEM images and XRD patterns of untreated and PFSC stabilized contaminated soils indicated that hematite and calcite (CaCO3) were the main products of PFSC stabilization processes. Adsorption on ferrihydrite, entrapment in hematite lattices, and co-precipitate with calcite might were the main mechanisms of As and Sb immobilization.

Cumulative health risk assessment of disinfection by-products in drinking water by different disinfection methods in typical regions of China.

Disinfection was essential to keep human healthy from microorganisms in drinking water. Meanwhile, disinfection by-products (DBPs) have been proved to be associated with some adverse health effects. The DBP levels were different in drinking water disinfected by different methods and may cause diverse health risks. However, studies in this field and systematic analysis about risk characteristics are limited. We estimated the health risks of DBPs exposure in drinking water through multi-pathways, and systematically analyzed the characteristics of different disinfection methods and influence factors of health risk of DBPs in China. Drinking water samples were collected and analyzed for DBPs from some representative water treatment plants in several typical regions in China. We adopted the additive method to estimate the health risks of DBPs exposure in drinking water through multi-pathways, and used descriptive and hierarchical analysis to understand their characteristics and influence factors. The concentrations of the six DBPs in drinking water ranged from 1.6 µg/L to 13.3 µg/L. The cumulative cancer risk of DBPs exposure through multi-pathways was 8.63 × 10-5. The total HI of DBPs exposure was 1.70 × 10-1. The health risks of DBPs in drinking water disinfected by chlorine dioxide and sodium hypochlorite were lower than by other disinfection methods. The health risk of DBPs in drinking water was dominated by risk through oral and inhalation route. The health risks in wet season were higher than that in dry season. There is no significant difference in health risk for males and females, but children experienced higher health risks than adults. Our study suggested the situation of that a large population experienced the high cancer risk of DBPs in drinking water in typical regions of China. It was suggested that potential higher risk should be concerned, and possible measures could be considered to decrease the health risks.

Calibration of a low-cost PM2.5 monitor using a random forest model.

BACKGROUND: Particle air pollution has adverse health effects, and low-cost monitoring among a large population group is an effective method for performing environmental health studies. However, concern about the accuracy of low-cost monitors has affected their popularization in monitoring projects. OBJECTIVE: To calibrate a low-cost particle monitor (HK-B3, Hike, China) through a controlled exposure experiment. METHODS: Our study used a MicroPEM monitor (RTI, America) as a standard particle concentration measurement device to calibrate the Hike monitors. A machine learning model was established to calibrate the particle concentration obtained by the low-cost PM2.5 monitors, and ten-fold validation was used to test the model. In addition, we used a linear regression model to compare the results of the machine learning model. A calibration method was established for the low-cost monitors, and it can be used to apply the monitors in future air pollution monitoring projects. RESULTS: The values of the random forest model calibration results and observations were more condensed around the regression line y = 0.99x + 0.05, and the R squared value (R2 = 0.98) was higher than that for the linear regression (R2 = 0.87). The random forest model showed better performance than the traditional linear regression model. CONCLUSIONS: Our study provided an effective calibration method to support the accuracy of low-cost monitors. The machine learning method based on the calibration model established in our study can increase the effectiveness of future air pollution and health studies.

Assessment of PM2.5 monitoring using MicroPEM: A validation study in a city with elevated PM2.5 levels.

Portable monitors such as MicroPEM can accurately characterize personal exposure of pollutants, which is critical for linking exposure and health effects of air pollution. The RTI (RTI International, Research Triangle Park, NC, USA) MicroPEM V3.2A provides both real-time fine particulate matter (PM2.5) concentrations and time-integrated PM samples collected onto Teflon filters that can be used to correct real-time data as well as allow further lab chemical analysis of species on filters (e.g., metal, black carbon). Due to the optical reflectivity of local PM sources can be very different from available standard reference particles used for calibration by RTI, there is a need for gravimetric correction and validation at each study location. However, assessments of MicroPEM have been limited in locations with severe air pollution, such as Beijing. We selected a variety of weather and air quality conditions, including both clear and hazy days in Beijing, to compare PM2.5 data among MicroPEMs as well as between MicroPEM and other types of samplers. We also compared MicroPEM real-time PM2.5 concentrations with data from nearby fixed-sites. The results show MicroPEM performed well across a wide range of PM2.5 concentrations (6-461 µg/m3) and MicroPEM data, after gravimetric correction, were consistent with those from moderate-volume samplers. Good agreement was also found between real-time data from MicroPEM and fixed-site data. The present study covered a wide range of pollution levels in actual environments and validated the usage of MicroPEM as a PM2.5 monitor in locations with elevated PM2.5 levels.

[Assessment of haze-related human health risks for four Chinese cities during extreme haze in January 2013].

OBJECTIVE: To evaluate the human health risks (premature death risk as an indicator) in Beijing, Shanghai, Guangzhou and Xi'an during extreme haze in January 2013. METHODS: The daily average particulate matter ≤ 2.5 µm in aerodynamic diameter (PM2.5) concentrations of Beijing, Shanghai, Guangzhou and Xi'an in January 2013 were collected and their characteristics explored. The populations and mortality rate of four cities in 2010 were collected from the statistical yearbook, the exposure-response relationships selected from the reference and then the premature death calculated according to the proportion risk model of Poisson regression. RESULTS: In January 2013, the 24 h mean concentrations of PM2.5 in Beijing, Shanghai, Guangzhou and Xi'an were (240 ± 165) , (83 ± 27), (94 ± 49) and (210 ± 98) µg/m(3) respectively and they were all above the secondary level of Ambient Air Quality Standards (GB 3095-2012). The 24 h mean concentrations of PM2.5 in Beijing and Xi'an were much higher than those in Shanghai and Guangzhou. Approximately 86.4% (19/22) , 58.1% (18/31), 54.8% (17/31) and 93.5% (29/31) of 24 h mean PM2.5 concentrations in Beijing, Shanghai, Guangzhou and Xi'an respectively exceeded the secondary level of Ambient Air Quality Standards (GB 3095-2012). The number of premature death due to the exposure to haze were 725 (95%CI: 457-977) for Beijing, 296 (95%CI: 96-502) for Shanghai, 310 (95%CI: 189-434) for Guangzhou and 85 (95%CI: 21-141) for Xi'an respectively in January 2013. CONCLUSION: The PM2.5 pollutions of four cities in January 2013 were serious enough to pose elevated risks of human health.