Partitioning of copper at the confluences of Andean rivers

The fate of copper (Cu) in rivers impacted by acid drainage remains poorly studied in waters with comparatively low Al and Fe concentrations. This work addresses the role of confluences in controlling the physical and chemical fate of Cu in a system with total molar ratio Cu/Al > 0.2 and Cu/Fe > 0.15. Two consecutive confluences were studied in the upper Mapocho watershed, a densely populated basin with intensive mining located in the Chilean Andes. The inflow had acidic conditions with seasonal variations and Cu up to 9 mg L^-1. Lability measurements with diffusive gradient in thin films showed that Cu entered as a dissolved labile form. However, downstream from the confluences a higher pH shifted Cu toward nonlabile compounds and solid phases enriched with Cu. Measurements of x-ray absorption spectroscopy of freshly formed particles showed that composition was dominated by sorbed Cu and Cu(OH)₂(s) precipitates, with a higher proportion of sorbed Cu downstream from confluences when pH < 5. Particle size distributions (PSD) measured in field showed that downstream from the confluences the total volume and average diameter of the suspended particles grew progressively, with estimated mean settling velocities increasing from 0.3 to 4.2 cm s^-1. As a result, 7-30% of the influent Cu was removed from the river flow. These results highlight that shifts in chemical partition and PSDs in river confluences and the hydrodynamic environments at the river reach level control the mobility of Cu in systems with high Cu/Al and Cu/Fe.

HiLi-chip: A high-throughput library construction chip for comprehensive profiling of environmental microbial communities

Investigating the contribution and associations of environmental microbes to ecological health and human well-being is in great demand with the goal of One Health proposed. To achieve the goal, there is an urgent need for accurate approaches to obtaining a large amount of high-resolution molecular information from various microbes. In this study, we developed a high-throughput library construction chip (HiLi-Chip) for profiling environmental microbial communities and evaluated its performance. The HiLi-Chip showed high conformity with the conventional Pacbio method in terms of α-diversity, community composition of abundant bacteria (>83%), as well as rare taxa (>84%) and human pathogens detection (>67%), indicating its advantages of accuracy, high-throughput, cost-efficiency, and broad practicability. It is suggested that the optimal strategy of the HiLi-Chip was a 2.4 μL PCR mixture per sample (∼2.4 ng DNA) with a 216-sample × 24-replicate format. We have successfully applied the HiLi-Chip to the Jiulongjiang River and identified 51 potential human bacterial pathogens with a total relative abundance of 0.22%. Additionally, under limited nutrients and similar upstream environments, bacteria tended to impose competitive pressures, resulting in a more connected network at the downstream river confluence (RC). Whereas narrow niche breadth of bacteria and upstream environmental heterogeneity probably promoted niche complementary and environment selection leading to fewer links at RC in the midsection of the river. Core bacteria might represent the entire bacterial community and enhance network stability through synergistic interactions with other core bacteria. Collectively, our results demonstrate that the HiLi-Chip is a robust tool for rapid comprehensive profiling of microbial communities in environmental samples and has significant implications for a profound understanding of environmental microbial interactions.