TSR-Derived Authigenic Calcites in Triassic Dolomite,NE Sichuan Basin,China-A Case Study of Well HB-1 and Well L-2

It has been proven that thermochemical sulfate reduction （TSR） took place extensively in the Lower Triassic carbonate reservoirs in Northeast （NE） Sichuan （四川） basin. We have carried out analyses on bulk rock compositions and isotope ratios together with petrography and fluid inclusions to assess the impact of TSR on diagenetic process of Triassic dolomites. In this article, TSR-related burial diagenesis is characterized by precipitation of calcite cement with negative 613C values and high ho- mogenization temperature. The light carbon isotopic compositions of this phase indicate that carbon incorporated in this cement was partly derived from oxidation of hydrocarbon. The high homogeniza- tion temperatures indicate that the thermochemical reduction of sulfates has been taking place in the deep part of NE Sichuan basin. Additional evidence supporting this interpretation is the high Sr values of this calcite cement. Moreover, the calcites have a 6180 of -8.51%o to -2.79%0 PDB and are interpreted to have precipitated from high salinity fluids with 6180 of ＋5%0 to ＋13%o SMOW. Under cathodolumi- nescence, these calcite cements appear dark brown or black, and both Mg concentrations and Mn/Sr ratios are low. It is therefore indicated that seawater was the principal agent of precipitation fluids. Finally, it should be noted that although H2S and CO2 increased as TSR continued, porosity has been ultimately destroyed by calcite cementation.

Removing microplastics from aquatic environments:A critical review

As one of the typical emerging contaminants,microplastics exist widely in the environment because of their small size and recalcitrance,which has caused various ecological problems.This paper summarizes current adsorption and removal technologies of microplastics in typical aquatic environments,including natural freshwater,marine,drinking water treatment plants(DWTPs),and wastewater treatment plants(WWTPs),and includes abiotic and biotic degradation technologies as one of the removal technologies.Recently,numerous studies have shown that enrichment technologies have been widely used to remove microplastics in natural freshwater environments,DWTPs,and WWTPs.Efficient removal of microplastics via WWTPs is critical to reduce the release to the natural environment as a key connection point to prevent the transfer of microplastics from society to natural water systems.Photocatalytic technology has outstanding pre-degradation effects on microplastics,and the isolated microbial strains or enriched communities can degrade up to 50%or more of pre-processed microplastics.Thus,more research focusing on microplastic degradation could be carried out by combining physical and chemical pretreatment with subsequent microbial biodegradation.In addition,the current recovery technologies of microplastics are introduced in this review.This is incredibly challenging because of the small size and dispersibility of microplastics,and the related technologies still need further development.This paper will provide theoretical support and advice for preventing and controlling the ecological risks mediated by microplastics in the aquatic environment and share recommendations for future research on the removal and recovery of microplastics in various aquatic environments,including natural aquatic environments,DWTPs,and WWTPs.