Unveiling the temporal variability of gas transfer coefficients of streams based on high-frequency dissolved oxygen measurements.

Greenhouse gas (GHG) emissions from streams and rivers are important sources of global GHG emissions. As a crucial parameter for estimating GHG emissions, the gas transfer coefficient (expressed as K at water temperature of 20 °C) has uncertainties. This study proposed a new approach for estimating K based on high-frequency dissolved oxygen (DO) data and an ecosystem metabolism model.

S-containing molecular markers of dissolved organic carbon attributing to riverine dissolved methane production across different land uses.

The emission of methane (CH) from streams and rivers contributes significantly to its global inventory. The production of CH is traditionally considered as a strictly anaerobic process. Recent investigations observed a "CH paradox" in oxic waters, suggesting the occurrence of oxic methane production (OMP).

Turnover of dissolved organic carbon fuels nocturnal CO emissions from a headwater catchment reservoir, Southeastern China: Effects of ecosystem metabolism on source partitioning of CO emissions.

Dam reservoirs in headwater catchments, as critical zones for their proximity to terrestrial sources, play important roles in dissolved organic carbon (DOC) cycling. However, the effects of ecosystem metabolism (EM) on DOC cycling are not well known. Here, in-situ diurnal and monthly observations were conducted to measure EM (including gross primary production (GPP), ecosystem respiration (ER) and heterotrophic respiration (HR)), DOC turnover and CO emissions in a headwater catchment reservoir in Southeastern China in 2020.

Enhanced chemodiversity, distinctive molecular signature and diurnal dynamics of dissolved organic matter in streams of two headwater catchments, Southeastern China.

Dissolved organic matter (DOM) is a complicated assembly of organic molecules, including thousands of molecules with various structures and properties. However, how the stream DOM sources respond to carbon compositions and the transformation processes remains unclear. In this study, the chemical characteristics and spectral and mass spectrometry (FT-ICR MS) of DOM were analyzed.

Distinctive Patterns and Controls of Nitrous Oxide Concentrations and Fluxes from Urban Inland Waters.

Inland waters are significant sources of nitrous oxide (NO), a powerful greenhouse gas. However, considerable uncertainty exists in the estimates of NO efflux from global inland waters due to a lack of direct measurements in urban inland waters, which are generally characterized by high carbon and nitrogen concentrations and low carbon-to-nitrogen ratios. Herein, we present direct measurements of NO concentrations and fluxes in lakes and rivers of Beijing, China, during 2018-2020.

Effect of sea surface temperature and precipitation on annual frequency of harmful algal blooms in the East China Sea over the past decades.

Coastal harmful algal blooms (HABs) in China's seas have attracted researchers' attention for decades. Among the four seas of China, the HAB frequency is the highest in the East China Sea (ECS). The impact of climate change and anthropogenic dominant factors on HABs is not well quantified and the response of HABs to the changing climate is also not clear.

Dominance of nitrous oxide production by nitrification and denitrification in the shallow Chaohu Lake, Eastern China: Insight from isotopic characteristics of dissolved nitrous oxide.

In recent decades, most lakes in Eastern China have suffered unprecedented nitrogen pollution, making them potential "hotspots" for NO production and emission. Understanding the mechanisms of NO production and quantifying emissions in these lakes is essential for assessing regional and global NO budgets and for mitigating NO emissions. Here, we measure isotopic compositions (δN-NO and δO-NO) and site preference (SP) of dissolved NO in an attempt to differentiate the relative contribution of NO production processes in the shallow, eutrophic Chaohu Lake, Eastern China.

Enhanced nitrogen imbalances in agroecosystems driven by changing cropping systems in a coastal area of eastern China: from field to watershed scale.

Agricultural activities exacerbate nitrogen (N) imbalances in the agroecosystem by disturbing the N inputs and outputs, yet the influence of changes in cropping systems on the N balance of agroecosystems remains unclear. In this study, at the field scale, we calculated the N balance of four cropping systems, (1) traditional crops with traditional crop rotation (G-G), (2) vegetables with traditional crop rotation (V-G), (3) vegetables with vegetable rotation (V-V), and (4) greenhouse vegetables (GHV); then analyzed the influence of changes in cropping systems from 1995 to 2015 on the N balances in the agroecosystems in sub-watersheds of the Dagu River. The results indicate that N balances were higher in GHV, V-V, and V-G than G-G, due to significantly higher inputs of N fertilizers and lower N use efficiency (NUE) in vegetable cultivation compared to traditional crops.

Nitrogen pollution and sources in an aquatic system at an agricultural coastal area of Eastern China based on a dual-isotope approach.

Nitrogen (N) pollution of water courses is a major concern in most coastal watersheds in eastern China with intensive agricultural production. We use hydrogeological and dual-isotopic approaches to analyze the N concentrations, pollution, transformations, and sources of surface water and groundwater in an agricultural watershed of the Jiaozhou Bay (JZB) area. Results showed that dissolved total N (DTN) concentrations in sub-rivers (SRs) ranged from 6.

Carbon and Nitrogen Burial and Response to Climate Change and Anthropogenic Disturbance in Chaohu Lake, China.

Lakes are a crucial component of the global carbon and nitrogen cycle. As a trend of enhanced human activities and climate change, the mechanisms of burial remain poorly understood. In this study, diverse biogeochemical techniques were applied to analyze the temporal variation of organic carbon and nitrogen burial rates in Chaohu Lake.

Tracking nitrate sources in the Chaohu Lake, China, using the nitrogen and oxygen isotopic approach.

The Chaohu Lake is highly polluted and suffers from severe eutrophication. Nitrate is a key form of nitrogen that can cause water quality degradation. In this study, hydrochemical and dual isotopic approaches were utilized to identify the seasonal variation of nitrate sources in the Chaohu Lake and its inflowing rivers.

Dissolved nitrous oxide and emission relating to denitrification across the Poyang Lake aquatic continuum.

Most aquatic ecosystems contribute elevated NO to atmosphere due to increasing anthropogenic nitrogen loading. To further understand the spatial heterogeneity along an aquatic continuum from the upriver to wetland to lake to downriver, the study was conducted on spatial variations in NO emission along Poyang Lake aquatic continuum during the flood season from 15 July 2013 to 10 August 2013. The results showed the NO concentrations, the ratio of NO/dinitrogen (N) gases production, NO emission and denitrification rates ranged from 0.

Dissolved organic carbon content and characteristics in relation to carbon dioxide partial pressure across Poyang Lake wetlands and adjacent aquatic systems in the Changjiang basin.

Dissolved organic carbon (DOC) plays diverse roles in carbon biogeochemical cycles. Here, we explored the link between DOC and pCO using high-performance size-exclusion chromatography (HPSEC) with UV detection and excitation emission matrix (EEM) fluorescence spectroscopy to determine the molecular weight distribution (MW) and the spectral characteristics of DOC, respectively. The relationship between DOC and pCO was investigated in the Poyang Lake wetlands and their adjacent aquatic systems.

Modeling increased riverine nitrogen export: Source tracking and integrated watershed-coast management.

The global NEWS model was calibrated and then used to quantify the long term trend of dissolved inorganic nitrogen (DIN) export from two tributaries of Jiulong River (SE China). Anthropogenic N inputs contributed 61-92% of river DIN yield which increased from 337 in 1980s to 1662 kg N km(-2) yr(-1) in 2000s for the North River, and from 653 to 3097 kg N km(-2) yr(-1) for the West River. North River and West River contributed 55% and 45% respectively of DIN loading to the estuary.

Controlled incorporation of nanoparticles in metal-organic framework hybrid thin films.

A facile encapsulation strategy was reported for preparing nanoparticles/metal-organic framework hybrid thin films which exhibit both the active (catalytic, magnetic, and optical) properties derived from the NPs and the size-selectivity originating from the well-defined microporous structure of the MOF thin films.

Temporal and spatial changes in nutrients and chlorophyll-a in a shallow lake, Lake Chaohu, China: an 11-year investigation.

Temporal and spatial changes of total nitrogen (TN), total phosphorus (TP) and chlorophyll-a (Chl-a) in a shallow lake, Lake Chaohu, China, were investigated using monthly monitoring data from 2001 through 2011. The results showed that the annual mean concentration ranges of TN, TP, and Chl-a were 0.08-14.