Variability in NO emission controls among different ponds within a hilly watershed.

While it is well established that small water bodies like ponds play a disproportionately large role in contributing to NO emissions, few studies have focused on lowland ponds in hilly watersheds. Here, we explored the characteristics of NO concentrations and emissions from various typical ponds (village, tea, forested, and aquaculture ponds) in a hilly watershed and examined the specific controls influencing NO production. Our findings revealed that tea ponds exhibited the highest NO flux (8.

Historical development, impact mechanism and future trends of nitrogen footprint in Wuxi City, China.

Human activities have changed the biogeochemical cycle of nitrogen, leading to a large amount of reactive nitrogen (Nr) into the environment, aggravating a series of environmental problems, affecting human and ecosystem health. Cities are the core areas driving nitrogen cycling in terrestrial ecosystems, however, there are numerous influencing factors and their contributions are unclear. The nitrogen footprint is an important index to understand the impact of human activities on the environment, however, the calculation of urban nitrogen footprint needs a simplified and accurate system method.

Small ponds have stronger potential for net nitrogen removal: Insight from direct dissolved N measurement.

Growing demands for watershed nitrogen (N) removal have called attention to abundant small bodies of water such as ponds, which have long been heralded as efficient storage and processing systems. Although pond conservation, restoration, and creation have been widely implemented to mitigate N pollution, information is limited regarding the impact of size-that is, whether N removal potential and efficiency are dependent upon pond size. We investigated the dynamics of N removal rates in 56 ponds from a hilly watershed by studying their bimonthly N concentrations and fluxes.

Sustainable nitrogen management strategies based on nitrogen flow in urban human system.

Urban nitrogen discharge has become an important factor leading to urban water environment deterioration, water crisis, and frequent air pollution. Human consumption is the driving force of nitrogen flow and the core of urban nitrogen research. Based on the process of nitrogen flow in the urban human system, combined with the relevant United Nations Sustainable Development Goals (SDGs) and taking Dar es Salaam as an example, we established a generic analytical framework for sustainable nitrogen management and put forward the strategies of sustainable nitrogen management in the urban human system.

Reactive nitrogen budgets in human-nature coupling system in lakeside area with insufficient data - A case study of Mwanza, Tanzania.

Nitrogen (N) is an essential nutrient element for life, and also a major element involved in the composition of greenhouse gases, surface water pollutants, air pollutants, etc. Quantifying and evaluating the nitrogen budget of a region is very important for effectively controlling the nitrogen discharge and scientifically managing the nitrogen cycle. In this paper, the urban Rural Complex N Cycling (URCNC) model was used to analyze the nitrogen budget of Mwanza region, a typical lakeside area with insufficient data, and the nitrogen flow process of livestock subsystem, cropland subsystem, human subsystem and landfill subsystem was clearly described and the nitrogen input sources of atmospheric subsystem and surface water subsystem were clarified.

Examining key impact factors of energy-related carbon emissions in 66 Belt and Road Initiative countries.

Climate change with global warming as the main feature associated with fossil energy use has been recognized as a threat to public health and welfare. Energy-related carbon emission reduction is a more serious challenge for BRI (Belt and Road Initiative) countries with rapid economic development. Examining key impact factors is necessary and helpful.

Strong variability in nitrogen (N) removal rates in typical agricultural pond from hilly catchment: Evidence from diel and monthly dissolved N measurement.

Ponds, depressional submerged landscapes that can store and process nitrogen (N)-enriched runoff from surrounding uplands, are recognized as biogeochemical hotspots for N removal. Despite their strong potential for N removal, information is limited concerning the specifics of their changing nature. Here, we investigated the dynamics of N removal rate in a typical agricultural pond from a hilly catchment, by unraveling the monthly and diel patterns of N concentrations and fluxes.

Decoding river pollution trends and their landscape determinants in an ecologically fragile karst basin using a machine learning model.

Karst watersheds accommodate high landscape complexity and are influenced by both human-induced and natural activity, which affects the formation and process of runoff, sediment connectivity and contaminant transport and alters natural hydrological and nutrient cycling. However, physical monitoring stations are costly and labor-intensive, which has confined the assessment of water quality impairments on spatial scale. The geographical characteristics of catchments are potential influencing factors of water quality, often overlooked in previous studies of highly heterogeneous karst landscape.

Direct measurements of dissolved N and NO highlight the strong nitrogen (N) removal potential of riverine wetlands in a headwater stream.

Increasing levels of nitrogen (N) in aquatic ecosystems due to intensified human activities is focusing attention on N removal mechanisms as a means to mitigate environmental damage. Important N removal processes such as denitrification can resolve this issue by converting N to gaseous emissions. Here, the spatiotemporal variability of N removal rates in China's Zhongtian River, a headwater stream that contains wetlands, was investigated by quantifying gaseous emissions of the main end products, N and NO, using the water-air exchange model.

Influencing mechanism of non-CO greenhouse gas emissions and mitigation strategies of livestock sector in developed regions of eastern China: a case study of Jiangsu province.

The livestock sector not only provides people with meat, eggs, milk, and other nutrients but also causes a large number of non-CO greenhouse gas emissions. It is urgent to explore the influence mechanism of non-CO greenhouse gas emission from the livestock sector and formulate effective mitigation strategies. Taking Jiangsu province as an example, we analyzed the influencing factors of non-CO greenhouse gas emissions from the livestock sector based on sources and modified the STIRPAT (stochastic impact by regression on population, affluence, and technology) model, proposed the directions, designed the generally circular path, and determined the focus of non-CO greenhouse gas emissions reduction from the livestock sector.

Rivers draining contrasting landscapes exhibit distinct potentials to emit diffusive methane (CH).

Methane (CH) is the second most important greenhouse gas, contributing approximately 17% of radiative forcing, and CH emissions from river networks due to intensified human activities have become a worldwide issue. However, there is a dearth of information on the CH emission potentials of different rivers, especially those draining contrasting watershed landscapes. Here, we examined the spatial variability of diffusive CH emissions and discerned the roles of environmental factors in influencing CH production in different river reaches (agricultural, urban, forested and mixed-landscape rivers) from the Chaohu Lake Basin in eastern China.

Restored riverine wetlands in a headwater stream can simultaneously behave as sinks of NO and hotspots of CH production.

Wetlands can improve water quality, but they are also recognized as important sources of greenhouse gases (GHG) such as nitrous oxide (NO) and methane (CH). Emissions of these gases from wetland ecosystems, especially those in headwaters, are poorly understood. Here, we determined monthly concentrations of dissolved NO and CH in a headwater stream of the Taihu Lake basin of China that contains both wetland and non-wetland reaches.

Urban rivers are hotspots of riverine greenhouse gas (NO, CH, CO) emissions in the mixed-landscape chaohu lake basin.

Growing evidence shows that riverine networks surrounding urban landscapes may be hotspots of riverine greenhouse gas (GHG) emissions. This study strengthens the evidence by investigating the spatial variability of diffusive GHG (NO, CH, CO) emissions from river reaches that drain from different types of landscapes (i.e.

[Spatiotemporal Variations in Nutrient Loads in River-lake System of Changdang Lake Catchment in 2016-2017].

Eutrophication of shallow lakes in the middle and lower reaches of the Yangtze River has become an increasingly serious problem. In this study, we investigated the temporal and spatial variations in nutrient loads (nitrogen, N and phosphorus, P) in the Changdang Lake Catchment located to the northwest of Lake Taihu through field sampling and laboratory analysis in 2016-2017. The results show the severity of the N and P pollution in the Changdang Lake catchment.

Remotely monitoring ecosystem respiration from various grasslands along a large-scale east-west transect across northern China.

Background: Grassland ecosystems play an important role in the terrestrial carbon cycles through carbon emission by ecosystem respiration (R) and carbon uptake by plant photosynthesis (GPP). Surprisingly, given R occupies a large component of annual carbon balance, rather less attention has been paid to developing the estimates of R compared to GPP.

Results: Based on 11 flux sites over the diverse grassland ecosystems in northern China, this study examined the amounts of carbon released by R as well as the dominant environmental controls across temperate meadow steppe, typical steppe, desert steppe and alpine meadow, respectively.

Surface nitrous oxide (NO) concentrations and fluxes from different rivers draining contrasting landscapes: Spatio-temporal variability, controls, and implications based on IPCC emission factor.

Increasing indirect nitrous oxide (NO) emission from river networks as a result of enhanced human activities on landscapes has become a global issue, as NO has been widely recognized as an important ozone-depleting greenhouse gas. However, indirect NO emissions from different rivers, particularly for those that drain completely different landscapes, are poorly understood. Here, we investigated the spatial-temporal variability of NO emissions among the different rivers in the Chaohu Lake Basin of Eastern China.

Differences in the responses of flow and nutrient load to isolated and coupled future climate and land use changes.

Understanding the differences in the responses of river hydrology and water quality to climate and land use changes is particularly crucial for the development and management of water resources in the future. This study was carried out to assess the isolated and coupled effects of future climate change and land use change on the flow and nutrient load of the Xitiaoxi watershed in southeast China by applying the calibrated Hydrological Simulation Program Fortran model. Four representative concentration pathways released by the Intergovernmental Panel on Climate Change and two projected land use change scenarios were used to simulate future conditions.

Modeling phosphorus sources and transport in a headwater catchment with rapid agricultural expansion.

Increasing riverine phosphorus (P) levels in headwaters due to expanded and intensified human activities are worldwide concerns, because P is a well-known limiting nutrient for freshwater eutrophication. Here we adopt the conceptual framework of the SPAtially Referenced Regressions On Watershed attributes (SPARROW) model to describe total phosphorus (TP) sources and transport in a headwater watershed undergoing rapid agricultural expansion in the upper Taihu Lake Basin, China. Our models, which include variables for land cover, river length, runoff depth, and pond density, explain 94% of the spatio-temporal variability in TP loads.

Carbon dynamics and environmental controls of a hilly tea plantation in Southeast China.

Tea plantations are widely distributed and continuously expanding across subtropical China in recent years. However, carbon flux exchanges from tea plantation ecosystems are poorly understood at the ecosystem level. In this study, we use the eddy covariance technique to quantify the magnitude and temporal variations of the net ecosystem exchange (NEE) in tea plantation in Southeast China over four years (2014-2017).

Influence of land use and rainfall on the optical properties of dissolved organic matter in a key drinking water reservoir in China.

The concentration, source and composition of dissolved organic matter (DOM) in aquatic ecosystems are associated with land use and hydrological connectivity between terrestrial and aquatic systems. However, direct evidence of the effects of rainfall and land use on the variability of DOM in aquatic ecosystems is very limited. In this study, chromophoric DOM (CDOM) absorption and fluorescence spectroscopy were used to elucidate how rainfall and land use affect the variability of CDOM in the watershed of Lake Tianmu, a key drinking water reservoir in the Yangtze River Delta.

Nitrogen transport and retention in a headwater catchment with dense distributions of lowland ponds.

The existence of lowland ponds alter watershed nitrogen (N) cycles via combined changes in runoff and N processing potential, which can significantly buffer watershed N transport. Here, we adopt the conceptual framework of the SPAtially Referenced Regressions On Watershed attributes (SPARROW) model to describe N transport and explore the buffering roles of lowland ponds in a small headwater watershed of Taihu Lake Basin, China. Our model, which included variables for nutrient sources, riverine length, precipitation and pond density, explained 95% of the spatio-temporal variability in total N loads.

Spatio-temporal dynamics of nitrogen and phosphorus input budgets in a global hotspot of anthropogenic inputs.

The increased input of anthropogenic nitrogen (N) and phosphorus (P) to watershed ecosystems has been cited as among the most important reasons for widespread water pollution. Revealing spatio-temporal patterns of N and P input budgets in regions with intensified human activity can facilitate a better understanding of human-induced N and P cycles. Here, we present budget inventories including both anthropogenic non-point and point N and P inputs into the Huai River Basin, which has been identified as one of the hotspots of anthropogenic inputs across the world.

Spatio-temporal dynamics of water quality and their linkages with the watershed landscape in highly disturbed headwater watersheds in China.

The water quality of headwater streams is a worldwide concern because of their critical roles in supplying clean water for drinking and other consumptive uses. Here, we evaluate temporal trends and spatial dynamics of the permanganate index (COD), ammonia-nitrogen (AN), and total phosphorus (TP) for 31 sites in headwater watersheds of the Huai River Basin, China. The seasonal Mann-Kendall test and correlation and variance analyses were applied to long-term time series (2003-2010) of water quality data in order to investigate the patterns of water quality trends, as well as their linkages with the watershed landscape.

Hydrodynamic and water quality modeling of a large floodplain lake (Poyang Lake) in China.

Floodplain lakes are valuable to humans because of their various functions and are characterized by dramatic hydrological condition variations. In this study, a two-dimensional coupled hydrodynamic and water quality model was applied in a large floodplain lake (i.e.