Fugacity model covering abiotic and biotic matrices to investigate the transfer and fate of perfluoroalkyl acids in a large shallow lake of eastern China.

Solving the challenges faced during the measurement of the cross-interface transfer of perfluoroalkyl acids (PFAAs) in lakes is crucial for clarifying environmental behaviours of these chemicals and their efficient governance. This study developed a multimedia fugacity model based on the quantitative water-air-sediment interaction (QWASI) covering abiotic/biotic matrices to investigate the cross-interface transfer and fate of PFAAs in Luoma Lake, a typical PFAA-contaminated shallow lake in eastern China. The accuracy and reliability of the established model were confirmed using Percent bias and Monte Carlo simulation, respectively. Using the QWASI model, the multimedia transfer of the PFAAs and their accumulation and persistence in different sub-compartments were described and measured, and the differences among individual PFAAs were explored. The simulation results showed that the sedimentation and resuspension of PFAAs were the most intense cross-interfacial transfers, and the sediments served as a chemical sink in the long term. A significant negative correlation of NC-F (the number of CF bonds) with the relative outflow flux (TW·out-ct) but a positive correlation with the relative net transfer across the interface between water and aquatic plants (Tp-ct) was detected, indicating that the PFAA migration capacity decreased but the bioaccumulation potential increased with the CF bond number. The persistence in water (Pw) of individual PFAAs ranged from 19.65d (PFOA) to 32.22d (PFOS), with an average of 26.15d; their persistence in sediment (Ps) ranged from 432d (PFBA) to 3216d (PFOS), with an average of 1524d, increasing linearly with an increase in NC-F. The water advection flows into and out of the lake (QW·in and QW·out), the PFAA concentration of water inflow (CW·in), and bioconcentration factor of aquatic plants (BCFp) were the primary parameters sensitive to PFAAs in all sub-compartments, which are essential indexes for exploring promising remediation pathways for lacustrine PFAA contamination based on the fugacity model simulation.

Dynamics of antibiotic resistance genes in the sediments of a water-diversion lake and its human exposure risk behaviour.

The dynamics and exposure risk behaviours of antibiotic resistance genes (ARGs) in the sediments of water-diversion lakes remain poorly understood. In this study, spatiotemporal investigations of ARG profiles in sediments targeting non-water (NWDP) and water diversion periods (WDP) were conducted in Luoma Lake, a typical water-diversion lake, and an innovative dynamics-based risk assessment framework was constructed to evaluate ARG exposure risks to local residents. ARGs in sediments were significantly more abundant in the WDP than in the NWDP, but there was no significant variation in their spatial distribution in either period. Moreover, the pattern of ARG dissemination in sediments was unchanged between the WDP and NWDP, with horizontal gene transfer (HGT) and vertical gene transfer (VGT) contributing to ARG dissemination in both periods. However, water diversion altered the pattern in lake water, with HGT and VGT in the NWDP but only HGT in the WDP, which were critical pathways for the dissemination of ARGs. The significantly lower ARG sediment-water partition coefficient in the WDP indicated that water diversion could shift the fate of ARGs and facilitate their aqueous partitioning. Risk assessment showed that all age groups faced a higher human exposure risk of ARGs (HERA) in the WDP than in the NWDP, with the 45-59 age group having the highest risk. Furthermore, HERA increased overall with the bacterial carrying capacity in the local environment and peaked when the carrying capacity reached three (NWDP) or four (WDP) orders of magnitude higher than the observed bacterial population. HGT and VGT promoted, whereas ODF covering gene mutation and loss mainly reduced HERA in the lake. As the carrying capacity increased, the relative contribution of ODF to HERA remained relatively stable, whereas the dominant mechanism of HERA development shifted from HGT to VGT.

Spatio-temporal distribution and dynamics of antibiotic resistance genes in a water-diversion lake, China.

The distribution and dynamics of antibiotic resistance genes (ARGs) in water-diversion lakes are poorly understood. In this study, two comparative in situ investigations of ARG profiles targeting water diversion (DP) and non-diversion periods (NDP) were conducted in Luoma Lake, a vital transfer node for the eastern route of the South-to-North Water Diversion Project in China. The results demonstrated significant spatiotemporal variations in ARG contamination and notable differences in the co-occurrence patterns of ARGs and bacterial communities between DP and NDP. Correlations among ARGs with the 16 S rRNA, and mobile genetic elements indicate that horizontal gene transfer (HGT) and vertical gene transfer (VGT) in NDP, but only HGT in DP, were the primary mechanisms of ARG proliferation and spread, implying that water diversion could be an essential control of the transfer pattern of ARGs in a lake environment. The null model analysis indicated that stochastic processes, with predominant driver of ecological drift in the lake mainly drove the assembly of ARGs. Partial least squares structural equation modeling was developed to analyze the causal effects of the factors in shaping ARG dynamics and identify the major driving forces in the DP and NDP.