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• High level of PFOA was found in fluoropolymer raw materials and products made in China. • The concentration of PFOA in fluoropolymer raw materials was higher than products. • Hexafluoropropylene oxide oligomers have been heavily used to substitute PFOA in fluoropolymer manufacture in China. • HFPO-TrA, a PFOA substitute, was found in high level in some emulsion samples. Perfluorooctanoic acid (PFOA), its salts, and related compounds were listed as new persistent organic pollutants by the Stockholm Convention in 2019. In this study, the occurrence of residues of PFOA and other per- and polyfluoroalkyl substances (PFASs) in raw materials and fluoropolymer products from the Chinese fluoropolymer industries are reported for the first time. The PFOA concentrations in raw materials and fluoropolymer products were in the range of 6.7 to 1.1 × 106 ng/g, and

The migration mechanisms, sources, and environmental risks of 29 legacy and emerging perfluorinated and polyfluoroalkyl species present in an oxidation pond (Ya'Er Lake) were investigated for treating sewage based on the analysis of their occurrence and distribution. The concentration of per- and polyfluoroalkyl substances (PFAS) in pond area was between 0.30 and 63.2 ng/g dw (dry weight), with the overall average concentration of 8.00 ng/g dw. Notably, the PFAS concentrations in the surface sediments near the sewage outlet in Pond-1 (50.2 ng/g dw) and Pond-5 (average 15.1 ng/g dw) were 1–2 orders of magnitude higher than those in other areas. In general, the legacy PFAS, i.e., perfluorooctane sulfonic acid was considered to be the major pollutant in the polluted area, on average, accounting for 73.0% of the total concentration of PFAS pollutants. By evaluating the regional distribution of different PFAS homologs, the short-chain PFAS pollutants with lower K ow were found to migrate farther in both horizontal and vertical directions. The sewage outlets in Pond-1 and Pond-5 are the main pollution sources in polluted area and the emerging PFAS pollutants in Pond-5 have replaced the legacy PFAS pollutants as the main pollutants. Based on positive matrix factorization analysis, three main industrial sources of PFAS pollutants in the study area were identified: protective coating, fire-fighting, and food packaging sources. Moreover, the environmental risk assessment results showed that most study areas exhibited medium environmental risk (0.01 ≤ Risk quotient (RQ) < 1), indicating that the ecological environment risks in this area need further attention. [Display omitted] [ABSTRACT FROM AUTHOR]

Previous studies commonly used dual laterolog or induction logging in vertical wells to study fractured reservoirs. However, there are few studies about the response characteristics of dual induction logging of horizontal wells in fractured reservoirs, which interferes with the evaluation of horizontal wells in fractured reservoirs. In this study, firstly, the finite element method is used to establish the fractured reservoir model and the dual induction instrument of horizontal well. Then, the response characteristics of dual induction logging in fractured reservoirs with different fracture conductivity, fracture dip angle, fracture width and fracture length are simulated and analyzed. The results show the response characteristics as follows: (1) The apparent conductivity of dual induction logging increases first and then decreases along with the increase of fracture conductivity, when the fracture conductivity is lower than formation conductivity, the apparent conductivity is similar to formation conductivity; (2) The fracture dip angle has little effect on the apparent conductivity of induction logging, when the fracture conductivity is high, the apparent conductivity decreases with the increase of the fracture dip angle; (3) The effect of fracture width and fracture length on apparent conductivity is similar. The larger the fracture width or length, the greater their influence on the apparent conductivity, which is different from the response characteristics of laterologs. In applications, these characteristics can be demonstrated by two wells in the southwest Ordos Basin, China. Finally, advantages and disadvantages of the simulation method, applications, logging responses discussed in detail, as well as the response characteristics and the shielding effect of fractures on electromagnetic waves of dual induction instrument are discussed in detail. The applications and discussions show that this study can provide response characteristics and novel understandings for the evaluations of horizontal wells in fractured reservoirs, especially in areas where dual induction logging is widely used. • The dual induction logging responses of horizontal well in fractured reservoirs were simulated. • The influences of fracture occurrence on dual induction logging were analyzed. • The shielding effect of fractures on the electromagnetic signal of dual induction tools is discussed. [ABSTRACT FROM AUTHOR]