Ethanol-diluted turbidimetry method for rapid and accurate quantification of low-density microplastics in synthetic samples.

Retention and transport behaviours of microplastics (MPs) and their associated pollutants in porous media are of great concern. The homogeneity of the studied MPs in artificially controlled lab-scale studies makes rapid and accurate MP quantification feasible. In this study, an economical ethanol-diluted turbidimetry method for polypropylene (PP) and polyethylene (PE) MPs was developed. With ethanol dilution, the MP dispersion system exhibited an excellent suspension performance. Strong linear relationships were observed between MP concentrations and turbidities in both low (<1.3 mg L-1) and high (<170 mg L-1) MP concentration ranges. Solution density and MP agglomeration governed the MP suspension performance. For low surface tension and high molecular mass, the addition of ethanol decreased the contact angles of PP-MPs with solutions from 81.73 to 15.5°, and consequently improved the MP suspension performance. The suspension system was optimised to an ethanol/water (v/v) ratio of 3:2 and 4:1 for PP- and PE-MPs, when the slopes of standard curves were determined to be 1.252 and 0.471 with the recovery of 100.54 ± 3.09% and 103.19 ± 1.66%, and the limit of detection and quantification values of 0.025 and 0.082 mg L-1, and 0.060 and 0.201 mg L-1, respectively. Solution pH, salinity, and dissolved organic matter in the selected range induced acceptable fluctuations in the MP recovery and matrix effect values. The Derjaguin-Landau-Verwey-Overbeek (DLVO) energy barriers were calculated to be > 20 kT, indicating excellent tolerance to the solution matrix. Additionally, applications in real water samples were validated to demonstrate the potential of the developed method.

Effective abatement of 29 pesticides in full-scale advanced treatment processes of drinking water: From concentration to human exposure risk.

This study investigated the occurrence and removal of 29 pesticides in 4 drinking water treatment plants (DWTPs) with conventional and advanced treatment processes (i.e., ozonation + biological activated carbon, and ultrafiltration) in Shanghai, China from 2018 to 2019. The concentration levels of target pesticides in raw waters ranged from below the limit of quantification (

Deiodination of iopamidol by zero valent iron (ZVI) enhances formation of iodinated disinfection by-products during chloramination.

Iodinated X-ray contrast media (ICM) is considered as one of iodine sources for formation of toxic iodinated disinfection byproducts (I-DBPs) during disinfection. This study investigated transformation of a typical ICM, iopamidol (IPM) by zero valent iron (ZVI) and the effect of transformation on the formation of I-DBPs during chloramination. It was found that the presence of ZVI could deiodinate IPM into I- and the transformation of IPM exhibited a pseudo-first-order kinetics. Acidic circumstance, SO42-, Cl- and monochloramine could promote the transformation of IPM by ZVI, while SiO32- inhibited the transformation of IPM. Moreover, the transformation of IPM by ZVI changed both the formed species and amounts of I-DBPs during chloramination. During the chloramination of IPM-containing water, CHCl2I and iodoacetic acid were the predominant iodinated trihalomethanes (I-THMs) and iodinated haloacetic acids (I-HAAs), respectively in the absence of ZVI, while CHI3 and triiodoacetic acid became the predominant ones with 1.0 g L-1 ZVI. The addition of 5.0 g L-1 ZVI increased I-DBPs formation amounts by 6.0 folds after 72 h and maximum formation of I-DBPs occurred at pH 5.0. Enhanced I-DBPs formation was also observed with various real water sources. Given that ZVI ubiquitously exists in the unlined cast iron distribution pipes, the deiodination of IPM by ZVI during distribution may increase the formation of I-DBPs, which needs receive enough attention.