A quantitative understanding of riverine nitrogen (N) export in response to human activities and climate change is critical for developing effective watershed N pollution control measures. This study quantified net anthropogenic N inputs (NANI) and riverine dissolved inorganic N (DIN=NO3-N+NH4-N+NO2-N) export for the upper Jiaojiang River catchment in eastern China over the 1980-2010 time period and examined how NANI, hydroclimate, and land-use practices influenced riverine DIN export. Over the 31-yr study period, riverine DIN yield increased by 1.6-fold, which mainly results from a ~77% increase in NANI and increasing fractional delivery of NANI due to a ~55% increase in developed land area. An empirical model that utilizes an exponential function of NANI and a power function of combining annual water discharge and developed land area percentage could account for 89% of the variation in annual riverine DIN yields in 1980-2010. Applying this model, annual NANI, catchment storage, and natural background sources were estimated to contribute 57%, 22%, and 21%, respectively, of annual riverine DIN exports on average. Forecasting based on a likely future climate change scenario predicted a 19.6% increase in riverine DIN yield by 2030 due to a 4% increase in annual discharge with no changes in NANI and land-use compared to the 2000-2010 baseline condition. Anthropogenic activities have increased both the N inputs available for export and the fractional export of N inputs, while climate change can further enhance riverine N export. An integrated N management strategy that considers the influence of anthropogenic N inputs, land-use and climate change is required to effectively control N inputs to coastal areas.

This study demonstrates the importance of the nitrogen-leaching lag effect, soil nitrogen release, and climate change on anthropogenic N inputs (NANI) and riverine total nitrogen (TN) export dynamics using a 30-yr record for the Yongan River watershed in eastern China. Cross-correlation analysis indicated a 7-yr, 5-yr, and 4-yr lag time in riverine TN export in response to changes in NANI, temperature, and drained agricultural land area, respectively. Enhanced by warmer temperature and improved agricultural drainage, the upper 20 cm of agricultural soils released 270 kg N ha(-1) between 1980 and 2009. Climate change also increased the fractional export of NANI to river. An empirical model (R(2) = 0.96) for annual riverine TN flux incorporating these influencing factors estimated 35%, 41%, and 24% of riverine TN flux originated from the soil N pool, NANI, and background N sources, respectively. The model forecasted an increase of 45%, 25%, and 6% and a decrease of 13% in riverine TN flux from 2010 to 2030 under continued development, climate change, status-quo, and tackling scenarios, respectively. The lag effect, soil N release, and climate change delay riverine TN export reductions with respect to decreases in NANI and should be considered in developing and evaluating N management measures.

Conservation tillage has been widely adopted in agricultural lands worldwide and is considered a potential strategy for climate change mitigation through enhanced carbon sequestration. However, conservation tillage may alter soil N2O emissions, which may diminish the potential climate change mitigation benefits. Based on 212 observations from 40 publications, a meta-analysis was conducted to quantitatively assess the effects of climate regimes, initial soil properties, and type/duration of agricultural practices on soil N2O emission following application of conservation tillage. Overall, conservation tillage significantly increased soil N2O emission by 17.8% compared to conventional tillage. The greatest increase in N2O emission was observed from soils in tropical climates (70.1%) experiencing short-term (29.3%) application of conservation tillage. Soil pH and clay content significantly influenced N2O emission, while overall soil texture and soil organic carbon (SOC) were not effective predictors of soil N2O emission following conservation tillage. According to the categorical meta-analysis, agricultural practices, including water, residue, and rotation managements and crop types, significantly affected soil N2O emission following conservation tillage. Conservation tillage induced N2O emissions were mitigated with rain-fed cropping systems, residue removal, crop rotation and cultivation of beans and some vegetables. Significant categorical variables affecting N2O emission were mainly attributed to soil aeration and substrate availability, which were important factors affecting nitrification and denitrification processes. Overall, the conservation tillage induced N2O emission factor (EFad) increased by 0.40%, suggesting an attenuation of climate change benefits from increased N2O emission. Our meta-analysis provides a scientific basis for assessing the effects of conservation tillage on N2O emissions and provides site-specific information to mitigate N2O emissions associated with conservation tillage practices.

The persistence effect contribution of legacy nutrients is often cited as a reason for little or no improvement in water quality following extensive implementation of watershed nutrient mitigation actions, yet there is limited knowledge concerning factors influencing this response, often called the “persistence effect.” Here, we adopted detrended fluctuation analysis and Spearman analysis methods to assess the influence of land use on the watershed phosphorus (P) persistence effect, using monthly water quality records during 2010–2016 in 13 catchments within a drinking water reservoir watershed in eastern China. Detrended fluctuation analysis was used to calculate the Hurst exponent α to assess watershed legacy P characteristics (α ≈ 0.5, α > 0.5, and α < 0.5 indicate white noise, persistence, and anti-persistence, respectively). Results showed weak to strong P persistence (0.60–0.81) in the time series of riverine P in the 13 catchments. The Hurst exponent α had negative relationships with agricultural land (R = −.47, p =.11) and developed land (R = −.67, p =.01) and a positive relationship with forest land cover (R =.48, p =.10). The persistence effect of riverine P was mainly determined by retention ability (biogeochemical legacy) and migration efficiency (hydrological legacy). A catchment with strong retention capacity (e.g., biomass uptake/storage and soil PO4 sorption) and low migration efficiency results in a stronger persistence effect for riverine P. In practice, source control is more effective in catchments with weak persistence, whereas sink control (e.g., riparian buffers and wetlands) is preferred in catchments with strong persistence effects.

Trend and change-point analyses of water quality time series data have important implications for pollution control and environmental decision-making. This paper developed a new approach to assess trends and change-points of water quality parameters by integrating locally weighted polynomial regression (LWPR) and segmented regression (SegReg). Firstly, LWPR was used to pretreat the original water quality data into a smoothed time series to represent the long-term trend of water quality. Then, SegReg was used to identify the long-term trends and change-points of the smoothed time series. Finally, statistical tests were applied to determine the significance of the long-term trends and change-points. The efficacy of this approach was validated using a 10-year record of total nitrogen (TN) and chemical oxygen demand (COD_Mn) from Shanxi Reservoir watershed in eastern China. Results showed that this approach was straightforward and reliable for assessment of long-term trends and change-points on irregular water quality datasets. The reliability was verified by statistical tests and practical considerations for Shanxi Reservoir watershed. The newly developed integrated LWPR-SegReg approach is not only limited to the assessment of trends and change-points of water quality parameters but also has a broad application to other fields with long-term time series records.

Quantitative information on cropland phosphorus (P) flows at the township scale is critical for developing sustainable P management measures under the smallholder farming system. This study addressed changes in cropland soil surface P budgets (i.e., net of P inputs and crop outputs), use efficiencies (i.e., the ratio between crop P uptake and total P input) and legacy P pools across 21 townships in the Yongan watershed of eastern China in 1980–2010. For the entire watershed, total P input (>98% from synthetic fertilizer and farmyard manure), crop uptake and budgets per cropland area increased from 50.4, 17.3 and 33.1kgPha−1yr−1 in 1980 to 74.6, 20.5 and 55.1kgPha−1yr−1 in 1995, and then sharply declined to 39.6, 11.4 and 28.2kgPha−1yr−1 in 2010, respectively. Estimated P use efficiency decreased from 34% in 1980 to 26% in 1999 before slightly increasing to 28% in 2010. Although the 21 townships had similar temporal variations over the 1980–2010 period, P budgets and use efficiency showed 2–3-fold spatial variability among townships within a given year. Spatio-temporal variations in the P budget and use efficiency were mainly related to changes in P fertilization rates and patterns (i.e., ratio of applied synthetic fertilizer P and farmyard manure P) and cropland types. The 20 townships having soil data had 87–720% and 113–395% increases of Olsen-P and total P contents in the upper 20cm of cropland soils between 1984 and 2009, respectively. Increased soil TP level between 1984 and 2009 suggested that more than 53–79% of the cumulative P budget accumulated as legacy P pools in cropland soils. Based on regression analyses, legacy soil P contribution to annual crop P uptake was estimated to increase from 0.47kgPha−1yr−1 (3%) in 1980 to 3.45kgPha−1yr−1 (31%) in 2010, with 52–80% from synthetic fertilizer and 2–46% from farmyard manure. Improved utilization of soil legacy P pools for crop production and increasing P use efficiency are necessary to minimize P inputs and reduce nonpoint source P pollution load. The high spatial heterogeneity in P budgets and use efficiencies across townships, as well as considerable legacy soil P pools after long-term over-application, should be considered in developing P management strategies under smallholder farm systems.

Heavy metal pollution is a major concern in China because of its serious effects on human health. To assess potential human health and ecological risks of heavy metal pollution, concentration data for seven heavy metals (As, Pb, Cd, Cr, Hg, Cu, Zn) from 14 sites spanning the rural-urban interface of the Wen-Rui Tang River watershed in southeast China were collected from 2000 to 2010. The heavy metal pollution index (HPI), hazard index (HI) and carcinogenic risk (CR) metrics were used to assess potential heavy metal risks. Further, we evaluated the uncertainty associated with the risk assessment indices using Monte Carlo analysis. Results indicated that all HPI values were lower than the critical level of 100 suggesting that heavy metal levels posed acceptable ecological risks; however, one site having an industrial point-source input reached levels of 80-97 on several occasions. Heavy metal concentrations fluctuated over time, and the decrease after 2007 is due to increased wastewater collection. The HI suggested low non-carcinogenic risk throughout the study period (HI < 1); however, nine sites showed CR values above the acceptable level of 10^-4 for potential cancer risk from arsenic in the early 2000s. Uncertainty analysis revealed an exposure risk for As at all sites because some CR values exceeded the 10^-4 level of concern; levels of Cd near an old industrial area also exceeded the Cd exposure standard (2.6% of CR values > 10^-4). While most metrics for human health risk did not exceed critical values for heavy metals, there is still a potential human health risk from chronic exposure to low heavy metal concentrations due to long-term exposure and potential metal interactions. Results of this study inform water pollution remediation and management efforts designed to protect public health in polluted urban area waterways common in rapidly developing regions.

To determine nitrogen (N) fate and environmental impact of applying anaerobic digestion slurry (ADS) to rice paddy (Oryza sativa L.), a field experiment was established using three treatments based on contrasting N application rate. The ADS (with ammonium-N accounting for >80 % of total N) treatment at a conventional application rate of 270 kg N ha-1 was compared to a negative control (no N fertilizer) and a positive control of urea applied at 270 kg N ha-1. The N budget showed the following distribution of applied N from ADS and urea: 41.3 ± 5.1 % for ADS and 36.6 ± 4.4 % for urea recovered by the rice plant (including straw, grain, and root), 16.4 ± 3.7 % for ADS and 7.4 ± 1.8 % for urea lost via ammonia volatilization, 0.26 ± 0.15 % for ADS and 0.15 ± 0.12 % for urea lost by direct N2O emission, 1.9 ± 0.5 % for ADS and 2.3 ± 0.8 % for urea leached downward, 0.70 ± 0.15 % for ADS and 0.67 ± 0.12 % for urea discharged with floodwater drainage, and 39.4 ± 8.4 % for ADS and 53.0 ± 9.1 % for urea retained by soil or lost by N2 emission. Compared to urea application, ADS application impacts the environment mainly through gaseous N losses rather than water N losses. ADS application had a positive impact on rice grain yield and reduced chemical fertilizer use. Considering the wide distribution of paddy fields and the ever-increasing quantities of ADS, ADS may serve as a valuable N source for rice cultivation, although mitigating ammonia and N2O losses should be further investigated. © 2012 Springer-Verlag Berlin Heidelberg.

Background

Kidneys from brain-dead donors are cold preserved until transplanted. However, prolonged cold storage can contribute to allograft failure. Studies suggest that donor preconditioning with dopaminergics may reduce cold-ischemic transplant injury, but whether heme oxygenase (HO)-1 induction is an underlying mechanism is not known.

Objective

To test whether preconditioning with fenoldopam (FD) induce HO-1 and protect kidneys against cold storage injury and whether HO-1 plays a role in protection.

Method

We used human renal proximal tubular epithelial cells, rat kidney transplants, and HO-1 null mice kidneys.

Results

FD preconditioning of cells for 4 hr significantly protected against cell death from 24-hr cold hypoxia and was associated with a dose-dependent increase in HO-1 expression. In a syngeneic rat kidney transplant model, FD preconditioning for 18 hr markedly increased kidney HO-1 expression and protected kidneys against 24-hr cold-ischemic transplant injury. To test the role of HO-1, renal proximal tubular epithelial cells were treated with HO-1 small interfering RNA, followed by FD-preconditioning. Small interfering RNA inhibited the HO-1 messenger RNA expression and reversed the FD protection. Suspension of kidneys of HO-1 null and wild-type mice preconditioned with FD or saline were subjected to 24- and 48-hr cold storage. N-acetyl glucosaminidase, a specific tubular injury marker, was significantly lower in FD-preconditioned wild-type kidneys, but not in HO-1 null kidneys, suggesting a role for HO-1 in FD's preconditioning.

Conclusion

Our data suggest HO-1 induction as an underlying mechanism for FD preconditioning and support the idea of testing FD preconditioning in the clinical setting. Studies are required to determine the optimum FD-preconditioning protocol.

It is crucial to quantitatively track riverine nitrate (NO3-) sources and transformations in drinking water source watersheds for preventing current and future NO3- pollution, and ensuring a safe drinking water supply. This study identified the significant contributors to riverine NO3- in Zhaoshandu reservoir watershed of Zhejiang province, southeast China. To achieve this goal, we used hydrochemistry parameters and stable isotopes of NO3- (δ15N-NO3- and δ18O-NO3-) accompanied with a Markov Chain Monte Carlo mixing model to estimate the proportional contributions of riverine NO3- inputs from atmospheric deposition (AD), chemical nitrogen fertilizer (NF), soil nitrogen (SN), and manure and sewage (M&S). Results indicated that the main form of riverine nitrogen in this region was NO3-, constituting ~60% of the total nitrogen mass on average (total organic nitrogen ~37% & ammonium ~3%). Variations in the isotopic signatures of NO3- demonstrated that microbial nitrification of NF, SN and M&S was the primary nitrogen transformation process within the Zhaoshandu reservoir watershed, whereas denitrification was minimal. A classical dual isotope bi-plot incorporating chloride concentrations suggested NF, SN and M&S were the major contributors of NO3- to the river. Riverine NO3- source apportionment results were further refined using the Markov Chain Monte Carlo mixing model, which revealed that AD, NF, SN and M&S contributed 7.6 ± 4.1%, 22.5 ± 12.8%, 27.4 ± 14.5% and 42.5 ± 11.3% of riverine NO3- at the watershed outlet, respectively. Finally, uncertainties associated with NO3- source apportionment were quantitatively characterized as: SN > NF > M&S > AD. This work provides a comprehensive approach to distinguish riverine NO3- sources in drinking water source watersheds, which helps guide implementation of management strategies to effectively control NO3- contamination and protect drinking water quality. SUMMARY OF THE MAIN FINDING FROM THIS WORKS (CAPSULE): We utilized NO3- stable isotope analysis and a Markov Chain Monte Carlo mixing model to quantify riverine nitrate pollution sources in a drinking water source watershed in Zhejiang province, southeast China. Markov Chain Monte Carlo mixing model output showed that NF, SN and M&S were the dominant sources of riverine NO3- during the sampling period in Zhaoshandu watershed. Uncertainty analysis characterized the variation strength associated with contributions of individual nitrate sources and indicated the greatest uncertainty for SN, followed by NF, M&S and AD.