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Rubber dams are widely used for landscaping in urban rivers and they retain large amounts of sediments. The sediments are rich in phosphorus (P) which can cause river eutrophication. Little is known about P release in rubber dams. We investigated the potential of sediment P release by isotherm experiment in an urban river with 30 rubber dams of northern China. We found that the potential of sediment P release (percentage saturation of zero equilibrium P concentration, EPCsat) was 76% at natural river part above dams, and then decreased to 67% at the 4th dam because of high deposition of fine sediments within the upper 4 dams. Between the 5th and the 30th dams, EPCsat increased to 90% because of the decrease of fine sediments and water soluble reactive P. EPCsat was also significantly higher (p

Discharge of phosphorus (e.g., PO4-P) and nitrogen (NO3-N) from the wastewater treatment facility (WWTF) effluent even at low occurrence (e.g., μg PO4-P L−1) could lead to eutrophication of receiving environments. Zhangjiakou city will host the international winter multi-sport event in 2022, which would probably yield a large amount of domestic WW and their associated contaminants in the water systems. To reveal the feasibility of an integrated surface flow constructed wetland (ISFCW) system for the purification of WWTF effluent, a field-scale ISFCW system was applied and operated in Zhangjiakou city. The ISFCW system consisted of a vegetated sedimentation pond (VSP) section followed by a biogeochemical barrier (BGB), and an SFCW. The purification performance of each purification component was monitored weekly over twelve months in terms of nutrient (N and P) removal. With the application of the ISFCW system, a total of 48.7, 59.4, 50.0, 54.9, and 60.2 % removal of TN, NH4-N, NO3-N, TP, and PO4-P was achieved in the summer period. Further analysis demonstrated that the contributions of VSP, BGB and FTW to all analyzed nutrient removal were 3–78 %. The key removal processes appeared to be biological and physicochemical pathways, and the integration of the VSP, BGB and SFCW enhanced the purification capacity of the system. Overall, the ISFCW system was effective at reducing nutrients from WWTF effluent and could consequently be used locally and in other similar mountain-river systems. Additional optimization of operating conditions could result in an enhanced reduction of nutrients.

Hybrid accidental urban wetlands (HAUWs) are expected to be a potential low-cost and highly efficient alternative means of minimizing pollutant loads from municipal areas as compared to the single-stage system being used. These unexpected HAUWs are created not through deliberate restoration, but as a result of water infrastructure decisions by local government. However, information on the long-term purification efficiency of large-scale HAUW improving eutrophic urban rivers is largely unexplored. An in-situ HAUW system consisting of a rubber dam, detention pond, accidental urban wetland, and overflow weir was evaluated at the field-scale for the purification of a eutrophic urban river in Zhangjiakou City, Hebei Province. The results for seven months of operation demonstrated that the effluent TP and NH4-N in the HAUW system could comply with the Grade III of Chinese National Surface Water Quality Standards. Average removal efficiencies for TN, NH4-N, NO3-N, TP, and PO4-P in the summer–autumn period of 52.6, 65,8, 56.6, 51.4, 58.2 and 88.3%, respectively, were recorded. These removal efficiencies were 59.4, 61.5, 65.6, 57.1, 59.4 and 65.7% higher than the respective values in the spring period. Furthermore, removal rates of nutrients were highly sensitive to temperature and showed seasonal trends. Further analysis showed that, with the application of the HAUW system, a total of 92.1, 69.5, 57.3, 37.8, 33.2, 12.4, 14.5, 7.3, 3.4% removal of Al, Mn, Cd, Pb, Zn, Ni, Fe, Ni, and As was achieved. Mean removal rates of TN, NH4-N, NO3-N, TP, TDP, PO4-P in the summer–autumn period were 2- 5 times higher than in those recorded in the early spring period. These results suggest that a variety of contaminant elimination mechanisms were offered by the HAUW, including enhanced hydraulic resistance, sedimentation, plant assimilation, microbial biofilm growth on roots’ surface and the HAUW design. Overall, this study demonstrated that the monitored HAUW could be another feature of the urban landscape that could help minimize pollutant loading to surface urban water bodies. This function is especially true in warm periods, in a similar way as natural wetlands or purposely built constructed wetlands. Nonetheless, managing these accidental treatment systems to maximize pollutant dissipation in the long-term would necessitate appropriate management strategies.

Quantifying non-point source (NPS) phosphorus (P) pollution loads is essential for watershed nutrients management. This study intended to develop a NPS P indicator which (1) was suitable in semi-humid and semi-arid watersheds of Northern China; (2) integrated the key NPS P loss factors and constructed them in a simple and physically understandable way and (3) kept P loss forms distinctively separate. An inverse distance-based delivery ratio was proposed to count for the P delivery efficiency from source to watercourses. We applied this P indicator in Luan River Watershed (LRW) of northern China under typical hydrological years and seasons. Results demonstrated that this NPS P indicator predicted reasonable NPS TP loads using simple methods and readily obtainable inputs. The sub-watersheds located in the south of LRW were recognized as the high risk areas of NPS P loss to Panjiakou reservoir. The upland and paddy fields near the river channels were particularly posing high risk and thus should be treated with prioritized management practices such as soil conservation and recommended fertilization. Rainfall-runoff related variables rather than P source variables explained more of the spatial variation in NPS P load and percentages. Using this tool could give policy makers insight into the component and location of NPS P pollution that needs to be the focus of policy at watershed scales before sophisticated studies were conducted in smaller scales.

Watershed models are cost-effective and powerful tools for evaluating and controlling non-point source (NPS) pollution. Generalized Watershed Loading Functions (GWLF) model, a relative parsimonious model, was applied to simulate watershed streamflow and nutrient loads in Liu River watershed, northern China. The model results were used to evaluate watershed NPS load, and the implications for NPS pollution mitigation measures were investigated. The temporal-spatial distribution, the critical source areas (CSAs) at sub-watershed level, and the best management practices (BMPs) efficiencies at CSAs were investigated by GWLF model. Due to the contrasting hydrological conditions, the NPS loads of wet year and flood season were much more than those of dry year and non-flood season. Four sub-watersheds were identified as CSAs, and the results showed that CSAs had high level of load intensities due to the high percentage of agricultural land and residential land. Through evaluating the efficiency and cost of seven BMPs, conservation tillage and vegetative buffers were selected as the measures to implement in the CSAs, and they can reduce 14.2% and 12.5% of total nitrogen and total phosphorus NPS loads in Liu river watershed. These findings can provide valuable information for implementing more effective and reasonable management measures to control NPS pollution in Liu River watershed and indicate the utility of GWLF with modest data requirements for such application.

The coupling of a geographic information system (GIS) and nonpoint source (NPS) models has significantly promoted NPS modeling and output visualization. This study reported an approach using R to fully integrate the GIS and a NPS Phosphorus indicator model, as well as to build an interactive web interface for the model". A case study in a semiarid northern China subwatershed showed that the proposed method was feasible, flexible and effective. Our experiences demonstrated that developing a fully-coupled GIS-NPS model system in R could simplify NPS modeling across computation platforms, promote modeling efficiency, implement dynamic simulations, enhance model inputs/outputs display and provide readily interactivity. We envision that the experiences could provide a promising option for NPS modeling.

Identification of the interactive responses of water quantity and quality to changes in nature and human stressors is important for the effective management of water resources. Many studies have been conducted to determine the influence of these stressors on river discharge and water quality. However, there is little information about whether sewage treatment plants can improve water quality in a region where river streamflow has decreased sharply. In this study, a seasonal trend decomposition method was used to analyze long-term (1996–2015) and seasonal trends in the streamflow and water quality of the Guanting Reservoir Basin, which is located in a semi-arid region of China. The results showed that the streamflow in the Guanting Reservoir Basin decreased sharply from 1996–2000 due to precipitation change and human activities (human use and reservoir regulation), while the streamflow decline over the longer period of time (1996–2015) could be attributed to human activities. During the same time, the river water quality improved significantly, having a positive relationship with the capacity of wastewater treatment facilities. The water quality in the Guanting Reservoir showed a deferred response to the reduced external loading, due to internal loading from sediments. These results implied that for rivers in which streamflow has declined sharply, the water quality could be improved significantly by actions to control water pollution control. This study not only provides useful information for water resource management in the Guanting Reservoir Basin, but also supports the implementation of water pollution control measures in other rivers with a sharp decline in streamflow.

Uncertainty analysis is an important prerequisite for model application. However, the existing phosphorus (P) loss indexes or indicators were rarely evaluated. This study applied generalized likelihood uncertainty estimation (GLUE) method to assess the uncertainty of parameters and modeling outputs of a non-point source (NPS) P indicator constructed in R language. And the influences of subjective choices of likelihood formulation and acceptability threshold of GLUE on model outputs were also detected. The results indicated the following. (1) Parameters RegR2, RegSDR2, PlossDPfer, PlossDPman, DPDR, and DPR were highly sensitive to overall TP simulation and their value ranges could be reduced by GLUE. (2) Nash efficiency likelihood (L1) seemed to present better ability in accentuating high likelihood value simulations than the exponential function (L2) did. (3) The combined likelihood integrating the criteria of multiple outputs acted better than single likelihood in model uncertainty assessment in terms of reducing the uncertainty band widths and assuring the fitting goodness of whole model outputs. (4) A value of 0.55 appeared to be a modest choice of threshold value to balance the interests between high modeling efficiency and high bracketing efficiency. Results of this study could provide (1) an option to conduct NPS modeling under one single computer platform, (2) important references to the parameter setting for NPS model development in similar regions, (3) useful suggestions for the application of GLUE method in studies with different emphases according to research interests, and (4) important insights into the watershed P management in similar regions.

Both suspended and streambed sediments from two pairs of streams (intervention outlet and control outlet, and Branch 14 and Branch 15) in livestock intensive catchments were analyzed for total phosphorus (TP), algal available P (AAP), P fractions and P saturation index (PSI). The variations in sediment P characteristics associated with sediment type and study sites were investigated; and the key variables controlling the variations were explored. Relative to streambed sediments, suspended sediments had significantly higher storage of TP and AAP and greater potential to continue adsorbing P from the water column. The differences between the two groups of sediments mainly resulted from differences in sediment particle size. For both suspended and streambed sediments, concentrations of TP, AAP, organic P (Po) and inorganic P (Pi) were not significantly different between the two catchment outlets, but were significantly higher in Branch 15 than in Branch 14; PSI values were considerably higher in the control outlet than at any of the study sites within the intervention micro-catchment. Sediment properties (e.g., calcium (Ca), aluminum (Al) and organic matter (OM)) and catchment characteristics (e.g., soil M3P status and drainage area) explained 62–87% of the variations in log-transformed TP, AAP, Po, Pi and PSI in suspended sediments, with sediment properties being the main contributor. For streambed sediments, variations in P concentrations and PSI were less well explained (13–56%), and sediment OM was the most importance predictor. Forest area percentage in landscape explained limited (3%) proportion of the variations in streambed sediment P concentrations and PSI.

Many rivers in China and other newly industrialized countries have suffered from severe degradation of water quality in the context of rapid economic growth. An accounting method was developed to investigate the source and mass fluxes of the main contaminants in the Ziya River, a severely polluted and heavily modified river in a semiarid area of the North China Plain, where chemical oxygen demand (COD) and ammonia nitrogen (NH4-N) were the most important indicators of pollution. The results showed that the urban sewage with high concentration of COD and NH4-N dominated the streams, contributing to 80.7 % of the streamflow, 92.2 % of COD, and 94.5 % of NH4-N. The concentrations of COD and NH4-N in streams varied from 24.0-195.0 to 5.8-43.8 mg/L, respectively. Mass fluxes of COD and NH4-N of all pathways were quantified. Much of the polluted water was diverted to irrigation, and some eventually flowed into the Bohai Sea. Installation of adequate wastewater treatment facilities and making strict discharge standards can help improve the water quality. Our findings imply that a simple accounting method provides an extremely well-documented example for load estimation and can be useful for intervention strategies in heavily polluted and modified rivers in newly industrialized countries.

Alloreactive memory T cells are major barriers to transplantation acceptance due to their capacity to accelerate rejection. Here, we investigated the effects of combined treatment with arsenic trioxide (As(2)O(3)) and blocking monoclonal antibodies (mAb) against CD154 and LFA-1 (anti-CD154/LFA-1) on graft survival as well as changes in pathology and immunological responses in mice with adoptively transferred allo-primed T cells. The mean survival time (MST) for the cardiac allografts in recipient mice receiving the combination of As(2)O(3) and anti-CD154/LFA-1 was significantly longer (>113.7days) compared to those receiving anti-CD154/LFA-1 (23.2days), As(2)O(3) (12.5days) alone or no treatment (5.5days). This combined strategy distinctly inhibited lymphocyte infiltration in grafts, proliferation of splenic T cells and the generation of memory T cells in spleens. Moreover, the combined treatment caused the significant down-regulation of IL-2 and IFN-γ accompanied by increased expression of TGF-β and regulatory T cells (Tregs) in spleens, which led to long-term cardiac allograft survival in recipient mice. These results highlight the potential application of As(2)O(3) and its contribution in combination therapy with antibody blockade to delay rejection by memory T cells.

A hydroponic experiment was conducted to investigate the effects of arsenic (As) stress on growth, nutrition and As uptake, and speciation in shoots and roots of winter wheat ( Triticum aestivum L.). Winter wheat has high tolerance to As. Most As is accumulated in the roots, and an As concentration of 4,421 mg/kg was observed at a solution concentration of 20 mg/L As. Arsenic concentrations in roots were approximately 40–100 times greater than those in shoots. Arsenic in winter wheat roots and shoots occurred as both As 3 + and As 5 + species, although As 3 + was the main species in winter wheat tissues. Arsenic significantly decreased the biomass of winter wheat shoots and roots and affected absorption and transport of micro- and macro-elements in winter wheat tissue. Arsenic treatment significantly increased the concentrations of total Magnesium (Mg) and calcium (Ca) in shoots and enhanced the transport of Mg and Ca from roots to shoots but decreased potassium (K), nitrogen (N), and phosphorus (P) concentrations in both shoots and roots, particularly the concentration of P. Concentrations of iron, copper, and zinc in winter wheat shoots were negatively related to As rates, with correlation coefficients ( R 2 ) of 0.93, 0.94, and 0.97, respectively.

Phosphorus (P) release and flux at sediment-water interface was hypothesized to vary with studied catchment branches due to differences in water chemistry of recharging groundwater. Stream water, seepage water, groundwater, and resurgence groundwater were collected, and their dissolved reactive P (DRP) concentrations and related water chemistry variables (pH, dissolved oxygen, cations, and anions) were measured to identify P sources in seepage water and resurgence groundwater and to look into their impacts on stream water DRP. Results showed that the groundwater-carried P concentrations were negligible, and, thus, not a direct source of DRP to stream water. However, the upwelling groundwater could contribute to stream water DRP by dissolving calcite-bound P in top sediments of branch 15. The seepage experiment indicated that in branch14, sediment release of reducible P was minimal. Furthermore, the presence of impermeable clay layer over the streambed of branch 14 prevented the transport of water and nutrients from beneath sediments to stream water, further reducing the P flux across the sediment-water interface. This study revealed that in branch 14, the recharge of anoxic groundwater did not significantly influence stream water P, due directly to its low P concentration, or indirectly to the lack of reducible P and the poor hydrological connectivity in bottom sediments. These results showed that differences between P soluble concentrations in small catchment streams can be explained by physicochemical processes at the sediment-water interface. More investigation is needed to assess whole catchment P dynamics.

Biosolids, i.e., treated sewage sludge, are commonly used as a fertilizer and amendment to improve soil productivity. Application of biosolids to meet the nitrogen (N) requirements of crops can lead to accumulation of phosphorus (P) in soils, which may result in P loss to water bodies. Since 1996, biosolids have been applied to a Pinus radiata D. Don plantation near Nelson City, New Zealand, in an N-deficient sandy soil. To investigate sustainability of the biosolids application programme, a long-term research trial was established in 1997, and biosolids were applied every three years, at three application rates, including control (no biosolids), standard and high treatments, based on total N loading. The objective of this study was to evaluate the effect of repeated application of biosolids on P mobility in the sandy soil. Soil samples were collected in August 2004 from the trial site at depths of 0–10, 10–25, 25–50, 50–75, and 75–100 cm. The soil samples were analysed for total P (TP), plant-available P (Olsen P and Mehlich 3 P), and various P fractions (water-soluble, bioavailable, Fe and Al-bound, Ca-bound, and residual) using a sequential P fractionation procedure. Soil TP and Olsen P in the high biosolids treatment (equivalent to 600 kg N ha−1 applied every three years) had increased significantly (P

The suitability for land application of biosolids can be limited by the presence of heavy metals. We investigated the distribution of heavy metals in the soil of a research trial within a Pinus radiata (D. Don) plantation following repeated applications of aerobically digested liquid biosolids. The trial is located on a sandy soil at Rabbit Island near Nelson, New Zealand. Biosolids were applied in 1997, 2000, and 2003, at 3 application rates: 0 (control), 300 (standard), and 600 kg N/ha (high). Litter layer and soil samples (down to 1 m) were taken from the trial site and analysed to assess the accumulation of heavy metals (Cu, Zn, Cd, Cr, Pb, and Ni) within the soil profile and the effect of repeated biosolids application on metal availability and mobility. Sequential fractionation methods were used to evaluate the distribution of exchangeable, specifically sorbed, oxide bound, organic bound, and residual fractions of the metals. Concentrations of Cr, Cu, Pb, and Zn in the litter layer were significantly (P