Distribution and accumulation of biogenic silica in the intertidal sediments of the Yangtze Estuary

Sedimentary biogenic silica is known to be all important parameter to understand biogeochemical processes and paleoenviromental records in estuarine and coastal ecosystems. Consequently, it is of great significance to investigate accumulation and distribution of biogenic silica in sediments. The two-step mild acid-mild alkaline extraction procedure was used to leach biogenic silica and its early diagenetic products in intertidal sediments of the Yangtze Estuary. The results showed that total biogenic silica(t-BSi)in the intertidal sediments varied from 237. 7-419. 4 μmol Si/g. while the mild acid leachable silica(Si-HCl)and the mild alkaline leachable silica(Si-Alk)were in the range of 25. 1-72. 9μmol Si/g and 208. 1-350. 4 μmol Si/g. respectively. Significant correlations were observed for the grain size distributions of sediments and different biogenic silica pools in intertidal sediments. This confirms that grain size distribution Can significantly affect biogenic silica contents in sediments. Close relationships of biogenic silica with organic carbon and nitrogen Were also found, reflecting that there is a strong coupling between biogenic silica and organic matter biogeochemical cycles in the intertidal system of the Yangtze Estuary. Additionally, the early diagenetic changes of biogenic silica in sediments are discussed in the present study.     

江苏省机动车和非道路移动机械排气污染防治立法探索和思考

随着燃煤、工业、扬尘等大气污染源的治理力度不断加强，机动车和非道路移动机械等移动源的排放贡献率逐步增加，已成为城市最主要的大气污染源之一。《江苏省机动车和非道路移动机械排气污染防治条例》已于2022年11月25日通过江苏省第十三届人民代表大会常务会员会第三十三次会议审议， 自2023年5月1日起施行。该条例的施行将为协同开展机动车和非道路移动机械排气监管，深入打好污染防治攻坚战提供有力的法规支撑。介绍了这部法规的背景、立法修订的必要性、制度设计的主要内容及创新亮点，分析了存在的不足并提出建议，为未来移动源立法工作提供地方经验和参考。