Dissolved organic matter (DOM) plays an important role in governing metal speciation and migration in aquatic systems. In this study, various DOM samples were collected from Lakes Erhai, Kokonor, and Chaka, and size-fractionated into high molecular weight (HMW, 1 kDa-0.7 μm) and low molecular weight (LMW, <1 kDa) fractions for measurements of dissolved organic carbon (DOC), spectral properties, and metal binding behaviors. Our results demonstrated that samples from Lake Chaka exhibited the highest DOC concentration and fluorescence indices but the lowest percentage of carbohydrates. Regardless of sampling locations, the HMW-DOM fractions contained higher abundances of aromatic DOM, carbohydrates and protein-like substances, but lower abundance of fulvic acid-like substances compared to those in the LMW fractions. Metal titration experiments coupled with the excitation-emission matrix (EEM)-parallel factor (PARAFAC) modeling revealed that the quenching of the PARAFAC-derived fluorescent components was more pronounced in the presence of Cu(II) compared to Pb(II). Humic-like components emerged as a superior model, exhibiting higher binding affinities for Cu(II) than protein-like substances, while the opposite trend was observed for Pb(II). In samples obtained from Lakes Erhai and Kokonor, the condition stability constants (Log K) for the binding of both Cu(II) and Pb(II) with the HMW-DOM fraction were higher than those with the LMW-DOM fraction. Conversely, a contrasting trend was observed for Lake Chaka. This study highlighted the heterogeneity in spectral properties and metal-binding behaviors of natural DOMs, contributing to an improved understanding of the molecular interactions between DOM components and metal ions and their environmental fate in aquatic ecosystems.
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http://dx.doi.org/10.1016/j.scitotenv.2024.174245 | DOI Listing |
Biogeochemistry
December 2024
Department of Natural Resources and the Environment, University of New Hampshire, 56 College Road, Durham, NH USA.
Unlabelled: Climate and atmospheric deposition interact with watershed properties to drive dissolved organic carbon (DOC) concentrations in lakes. Because drivers of DOC concentration are inter-related and interact, it is challenging to assign a single dominant driver to changes in lake DOC concentration across spatiotemporal scales. Leveraging forty years of data across sixteen lakes, we used structural equation modeling to show that the impact of climate, as moderated by watershed characteristics, has become more dominant in recent decades, superseding the influence of sulfate deposition that was observed in the 1980s.
View Article and Find Full Text PDFEnviron Microbiol
December 2024
Department of Earth System Science, Stanford University, Stanford, California, USA.
Subterranean estuaries (STEs) are critical ecosystems at the interface of meteoric groundwater and subsurface seawater that are threatened by sea level rise. To characterize the influence of tides and waves on the STE microbial community, we collected porewater samples from a high-energy beach STE at Stinson Beach, California, USA, over the two-week neap-spring tidal transition during both a wet and dry season. The microbial community, analyzed by 16S rRNA gene (V4) amplicon sequencing, clustered according to consistent physicochemical features found within STEs.
View Article and Find Full Text PDFEcotoxicol Environ Saf
December 2024
College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China; Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture and Rural Affairs, Yangling, Shaanxi 712100, China. Electronic address:
Dissolved organic matter (DOM) released by straw returning for decomposition interacts with selenium (Se) in soil, which affects the speciation distribution of Se and its bioavailability. However, the relative mechanisms involved are slightly understood. This study investigated the effects of straw-derived DOM on two levels of exogenous selenite (low-Se and high-Se treatments) in two types of soil with distinct pH.
View Article and Find Full Text PDFSci Total Environ
December 2024
College of Geographical Science, Fujian Normal University, Fuzhou 350007, China; Fujian Provincial Key Laboratory for Subtropical Resources and Environment, Fujian Normal University, Fuzhou 350007, China.
The interaction between soil dissolved organic matter (DOM) and bacterial communities is critical for understanding key processes in the global carbon cycle. However, the molecular-level associations between these components remain poorly understood. To address this gap, high-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was combined with high-throughput sequencing to examine how DOM composition and bacterial sub-community diversity respond to different levels of nitrogen (N) addition (0, 40, and 80 kg N ha yr) and to explore the relationships between them.
View Article and Find Full Text PDFWater Res
December 2024
State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Urban Water Supply, Water Saving and Water Environment Governance in the Yangtze River Delta of Ministry of Water Resources, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, PR China. Electronic address:
Restricted to the complex nature of dissolved organic matter (DOM) in various aquatic environments, the mechanisms of enhanced iodinated disinfection byproducts (I-DBPs) formation in water containing both I and IO (designated as I/IO in this study) during the ultraviolet (UV)-chloramine sequential disinfection process remains unclear. In this study, four machine learning (ML) models were established to predict I-DBP formation by using DOM and disinfection features as input variables. Extreme gradient boosting (XGB) algorithm outperformed the others in model development using synthetic waters and in cross-dataset generalization of surface waters.
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