Long-term characteristics of criteria air pollutants in megacities of Harbin-Changchun megalopolis, Northeast China: Spatiotemporal variations, source analysis, and meteorological effects.

The hourly concentration of six criteria air pollutants in the Harbin-Changchun region were used to investigate the status and spatiotemporal variation of target air pollutants and their relationships with meteorological factors. The annual concentrations of particulate matters during 2013-2017 were two times higher than the Chinese Ambient Air Quality Standards (CAAQS) Grade Ⅱ. The annual O3 concentration increased by two times during 2013-2018 in Harbin. The concentration of PM, SO2, NO2, and CO depicted a similar seasonal trend with an order of winter > autumn > spring > summer. The consistent interannual variation trends of PM2.5/CO, NO2 and SO2 indicated that the formation of secondary inorganic aerosols in the annual scale was dominated by the concentrations of NO2 and SO2. The interannual variations of the individual meteorological factors causing on PM2.5 and O3 during 2013-2018 varied significantly in seasonal scale. The interannual variations were stable in annual scale indicating that the continuous decline of PM2.5 during 2014-2018 can be attributed to the comprehensive and strict prohibition of small coal-fired boilers and straw burning in the study area. Meanwhile, the increase in O3 during 2013-2018 in the study area were mainly attributed to the rapid growth of the emission of its precursor (VOCs and NOx). The influence of meteorology on PM2.5 and ozone were the most stable and strongest in winter than that in the other three seasons.

Occurrence, composition profiles and risk assessment of polycyclic aromatic hydrocarbons in municipal sewage sludge in China.

A nationwide survey, including 75 sludge samples and 18 wastewater samples taken from different wastewater treatment plants (WWTPs) from 23 cities, was carried out to investigate the occurrence and composition profiles of polycyclic aromatic hydrocarbons (PAHs) in China. In total, the concentrations of ∑16PAHs in sludge ranged from 565 to 280,000 ng/g (mean: 9340 ng/g) which was at a moderate level in the world. The composition profiles of PAHs were characterized by 3- and 4-ring PAHs in textile dyeing sludge and 4- and 5-ring PAHs in domestic sludge. Significant variations in regional distribution of PAHs were observed. Both the principal components analysis and diagnostic ratios revealed that vehicle exhaust, coal and natural gas combustion were the main sources of PAHs in China. The estimated concentrations of PAHs were 3820 ng/L and 1120 ng/L in influents and effluents of the WWTPs, respectively. The high toxic equivalent quantity (TEQ) values of PAHs are ascribed to the high PAH levels. Risk quotient values (RQs) in sludge indicated that there was low potential risk to soil ecosystem after sludge had been applied one year except for indeno [1,2,3-cd]pyrene (IcdP) detected in Huaibei, Anhui province.