Seasonal variation regulate the endogenous phosphorus release in sediments of Shijiuhu Lake via water-level fluctuation

Drivers and spatial variations in the concentrations and limitations of carbon, nitrogen, and phosphorus in global alpine lakes

Alpine lakes are highly sensitive to environmental changes and struggle to recover from disturbances. Global climate change and human activities increase carbon (C), nitrogen (N), and phosphorus (P) inputs to alpine lakes. In this study, we had conducted a comparative analysis of C, N, and P concentrations and their limitations for 323 alpine lakes with elevations ranging from 502 to 5,018 m a.s.l., assessing the impact of environmental (climate and land use patterns) and social (population and economic development) factors of catchment on their nutritional status. These alpine lakes were located in Asia, Europe, and North America. Results showed that alpine lakes in Asia have higher concentrations of DOC, TN, and TP compared to Europe and North America. Despite lower N and P concentrations in alpine lakes than plain lakes, the N/P mass ratios are comparable, suggest greater vulnerability in alpine lakes. Chlorophyll-a (Chl-a) is more influenced by N in Asia and North America, while P is a greater factor in Europe. Global changes in TP concentrations in alpine lakes are generally influenced by climate factors. In Asia, alpine lake trophic status is primarily influenced by both catchment land use patterns and local social development. In Europe, multiple factors influence alpine lake nutrition, whereas in North America, the correlation between alpine lake nutrition and catchment environmental and social factors is weaker. This study highlights vulnerability of alpine lake ecosystems and underscores the importance of developing the tailored regional management strategies based on the primary drivers for each area.

Fate of bisphenol A and nonylphenol in the lake riparian zone: Distribution, transport, and microbial response

The lake riparian zone (LRZ) is a key area of material circulation between terrestrial and aquatic ecosystems. However, the exchange of endocrine disrupting compounds (EDCs) in this area is still unknown. Thus, in this study, the distribution, convection and microbial response of two typical EDCs, bisphenol A (BPA) and nonylphenol (NP), in submerged (SS) and temporarily flooded sediment (FS) of LRZ were investigated by in-situ diffusive gradients in thin films technology. Concentrations of BPA (11.07 ± 2.49 μg/kg) and NP (20.42 ± 8.23 μg/kg) in FS significantly fluctuated with depth, conversely, their concentrations in SS increased steadily with depth (BPA: 14.01 ∼ 74.76 μg/kg; NP: 14.14 ∼ 137.01 μg/kg). BPA and NP dynamics analysis based on the DIFS (DGT-induced fluxes in sediments) model and fugacity fraction showed the water-sediment exchange capacity of BPA and NP in SS was on average 2-3 times higher than in FS. Some bacterial genera involved in nitrogen metabolism can effectively transform BPA and NP, such as Pseudomonas, Novosphingobium, and Sphingomonas, which are more active in oxygenic FS than in hypoxic SS. Considering this evidence as well as an increasing EDCs pollution, the behavior and quantification of EDCs at the water-sediment interface of the LRZ merits a further investigation.

Effect of soil-groundwater system on migration and transformation of organochlorine pesticides: A review

Soil is the place where human beings, plants, and animals depend on for their survival and the link between the various ecological layers. Groundwater is an important component of water resources and is one of the most important sources of water for irrigated agriculture, industry, mining and cities because of its stable quantity and quality. Soil and groundwater are important strategic resources highly valued by countries around the world. However, in recent years, the deterioration of the ecological environment of soil-groundwater caused by industrial, domestic, and agricultural pollution sources has continued to threaten human health and ecological security. Among them, organochlorine pesticides (OCPs), as typical organic pollutants, cause very serious pollution of soil and groundwater environment. However, most studies on the pollution of OCPs have focused on the aboveground or surface water environment, and little consideration has been given to the pollution and hazards of OCPs to the deep soil and groundwater environment, especially the effects of different environmental factors on the transport and transformation of OCPs in soil-groundwater. Moreover, in addition to the influence of a single factor on it, the interactions that arise between different factors cannot be ignored. This paper focuses on two major sources of OCPs in soil and groundwater environments, compiles and summarizes the effects of environmental factors such as pH, microbial communities and enzyme activities on the transport and transformation of OCPs in soil and groundwater systems, discusses the synergistic effects of individual environmental factors and others, and comprehensively analyses the effects of synergistic effects of various environmental factors on the transport and transformation of OCPs. In the context of ecological civilization construction, it provides the scientific basis and theoretical foundation for the prevention and treatment of OCPs-contaminated soil and groundwater, and puts forward new ideas and suggestions for the research and development of green, eco-friendly remediation and treatment technologies for OCPs-contaminated sites.

Rainfall seasonality shapes microbial assembly and niche characteristics in Yunnan Plateau lakes, China

Microorganisms are crucial components of freshwater ecosystems. Understanding the microbial community assembly processes and niche characteristics in freshwater ecosystems, which are poorly understood, is crucial for evaluating microbial ecological roles. The Yunnan Plateau lakes in China represent a freshwater ecosystem that is experiencing eutrophication due to anthropogenic activities. Here, variation in the assembly and niche characteristics of both prokaryotic and microeukaryotic communities was explored in Yunnan Plateau lakes across two seasons (dry season and rainy season) to determine the impacts of rainfall and environmental conditions on the microbial community and niche. The results showed that the environmental heterogeneity of the lakes decreased in the rainy season compared to the dry season. The microbial (bacterial and microeukaryotic) α-diversity significantly decreased during the rainy season. Deterministic processes were found to dominate microbial community assembly in both seasons. β-Diversity decomposition analysis revealed that microbial community compositional dissimilarities were dominated by species replacement processes. The co-occurrence networks indicated reduced species complexity for microbes and a destabilized network for prokaryotes prior to rainfall, while the opposite was found for microeukaryotes following rainfall. Microbial niche breadth decreased significantly in the rainy season. In addition, lower prokaryotic niche overlap, but greater microeukaryotic niche overlap, was observed after rainfall. Rainfall and environmental conditions significantly affected the microbial community assembly and niche characteristics. It can be concluded that rainfall and external pollutant input during the seasonal transition alter the lake environment, thereby regulating the microbial community and niche in these lakes. Our findings offer new insight into microbiota assembly and niche patterns in plateau lakes, further deepening the understanding of freshwater ecosystem functioning.

Risk and mechanisms of phosphorus release at the sediment-water interface of lakes in cold and arid regions during non-frozen seasons

In recent years, the eutrophication of lakes has accelerated in cold arid regions; the release of nutrients from sediments is an important contributor. The sequential extraction method, high-resolution peeper (HR-Peeper), and diffusive gradients in thin films (DGT) techniques were used to study the occurrence characteristics, release risk, and release mechanism of phosphorus (P) at the sediment-water interface (SWI) of Ulanor Wetland in the Hulun Lake Basin, Inner Mongolia, China. The mean total P concentration in overlying water was lower in August than that in May. Dissolved organic P (DOP) or particulate P (PP) was the main form of P in the overlying water. PP dominates in May and DOP in August. Refractory P was the main form of P in sediments. The concentrations of soluble reactive P and DGT-active P in the pore water of the sediment column were higher than those in the overlying water, and the concentrations were higher in August than those in May. Release of P in the wetland sediments occurred during the non-frozen seasons, with a higher risk in August than in May. The good linear correlation between dissolved P, Fe, and Mn in the DGT profiles verified their co-release due to the anaerobic reduction of Fe/Mn oxides. Moreover, alkaline sediments are also conducive to the release of sediment P. This study can provide data and theoretical support for eutrophication control in Ulanor Wetland and other similar water bodies in cold and arid regions.