[Characteristics of Heavy Metal Pollutants of PM2.5 from Open Burning of Municipal Solid Waste (MSW) and the Associated Exposure Health Risks].

The characteristics and health risk assessment for heavy metal pollutants in PM2.5 discharged from the open burning of municipal solid waste (MSW) in different functional areas were studied using a flue gas diluted sampling system. The two common open burning modes of barrel and natural pile-up burning were considered. The results show that the concentration of zinc (Zn) was the highest among the heavy metals produced by five different components of waste incineration, ranging from 1324.03 to 3703.12 mg·kg-1. The concentration of cadmium (Cd) was the lowest, ranging from 20.25 to 63.68 mg·kg-1. According to the geo-accumulation index, lead (Pb), Zn, arsenic (As), and Cd were highly polluted in the measured MSW samples, and all four of these metals reached moderate or higher levels of pollution under natural pile-up burning methods. The geo-accumulation index of Cd was much higher than 5. The results of the human health risk assessment showed that non-carcinogenic risk values for 8 heavy metals (Pb, Zn, Cu, Mn, As, Cd, Cr, and Ni) by respiratory exposure were less than 1, which is within the safe range. For natural pile-up burning, the total non-carcinogenic risk values for As and Pb for children were higher than 1, indicating a non-carcinogenic risk. The carcinogenic risk values for four carcinogenic elements (As, Cd, Cr, and Ni) were less than 1.0×10-4, but still represented a low potential carcinogenic risk under exposure for long periods of time.

[Emission Characteristics and Chemical Components of PM2.5 from Open Burning of Municipal Solid Waste].

Source emission measurements were employed to investigate open burning of municipal solid waste (MSW). Both barrel and natural pile-up burning of MSW were investigated using a self-designed dilution sampling system. PM2.5 was collected for three types of waste, including rubber and plastic, paper, and wood and bamboo. Then, components in the samples were analyzed and emission factors of PM2.5, organic carbon (OC), elemental carbon (EC), water-soluble ions and inorganic elements were calculated. The PM2.5 emission factor was highest for wood and bamboo, and lowest for paper, and was calculated to be (7.44±0.76) g·kg-1 and (2.72±0.52) g·kg-1, respectively. Barrel burning resulted in much higher pollutant emissions. The PM2.5 emission factor for barrel burning was 2.5-3.5 times that of natural pile-up burning. OC and EC were the main components of PM2.5, with a proportion of 46.6%-67.2%. MSW composition had a greater effect on the OC/EC ratios than burning mode. The ratios could be helpful in the analysis of the emission contributions of different MSW components. The proportions of NH4+ and Cl- were the highest in water-soluble ions, accounting for 2.28%-6.35% and 1.04%-14.31%, respectively. Among inorganic elements, Ca, K, Fe, and Ba showed high emission factors. The emission factor of Zn was the highest among heavy metals, and other elements such as Cu, Cr, Sb, and Pb were also enriched. Zn emission was mainly determined by the burning mode; emissions from barrel combustion were approximately 20 times more than that of natural pile-up burning.