Construction of biochar-based organohalide-respiring bacterial agent for remediation of 2,4,6-trichlorophenol contaminated soil.

Construction of an efficient bio-reductive dechlorination system remains challenging due to the narrow ecological niche and low-growth rate of organohalide-respiring bacteria during field remediation. In this study, a biochar-based organohalide-respiring bacterial agent was obtained, and its performance and effects on indigenous microbial composition, diversity, and inter-relationship in soil were investigated. A well-performing material, Triton X-100 modified biochar (BC600-TX100), was found to have the superior average pore size, specific surface area and hydrophicity, compared to other materials. Interestingly, Pseudomonas aeruginosa CP-1, which is capable of 2,4,6-TCP dechlorination, showed a 348 times higher colonization cell number on BC600-TX100 than that of BC600 after 7 d. Meanwhile, the dechlorination rate in soil showed the highest (0.732 d-1) in the BC600-TX100 bacterial agent than in the other agents. The long-term performance of the BC600-TX100 OHRB agent was also verified, with a stable dechlorination activity over six cycles. Soil microbial community analysis found the addition of the BC600-TX100 OHRB agent significantly increased the relative abundance of genus Pseudomonas from 1.53 % to 11.2 %, and Pseudomonas formed a close interaction relationship with indigenous microorganisms, creating a micro-ecological environment conducive to reductive dechlorination. This study provides a feasible bacterial agent for the in-situ bioremediation of soil contaminated organohalides. ENVIRONMENTAL IMPLICATION: Halogenated organic compounds are a type of toxic, refractory, and bio-accumulative persistent compounds widely existed in environment, widely detected in the air, water, and soil. In this study, we provide a feasible bacterial agent for the in-situ bioremediation of soil contaminated halogenated organic compounds. The application of biochar provides new insights for "Turning waste into treasure", which meets with the concept of green chemistry.

Exploring efficient strategies for air quality improvement in China based on its regional characteristics and interannual evolution of PM2.5 pollution.

Fine particulate matter (PM2.5) harms human health and hinders normal human life. Considering the serious complexity and obvious regional characteristics of PM2.5 pollution, it is urgent to fill in the comprehensive overview of regional characteristics and interannual evolution of PM2.5. This review studied the PM2.5 pollution in six typical areas between 2014 and 2022 based on the data published by the Chinese government and nearly 120 relevant literature. We analyzed and compared the characteristics of interannual and quarterly changes of PM2.5 concentration. The Beijing-Tianjin-Hebei region (BTH), Yangtze River Delta (YRD) and Pearl River Delta (PRD) made remarkable progress in improving PM2.5 pollution, while Fenwei Plain (FWP), Sichuan Basin (SCB) and Northeast Plain (NEP) were slightly inferior mainly due to the relatively lower level of economic development. It was found that the annual average PM2.5 concentration change versus year curves in the three areas with better pollution control conditions can be merged into a smooth curve. Importantly, this can be fitted for the accurate evaluation of each area and provide reliable prediction of its future evolution. In addition, we analyzed the factors affecting the PM2.5 in each area and summarize the causes of air pollution in China. They included primary emission, secondary generation, regional transmission, as well as unfavorable air dispersion conditions. We also suggested that the PM2.5 pollution control should target specific industries and periods, and further research need to be carried out on the process of secondary production. The results provided useful assistance such as effect prediction and strategy guidance for PM2.5 pollution control in Chinese backward areas.