Evaluating the effect of dam construction on the phosphorus fractions in sediments in a reservoir of drinking water source, China.

It is widely acknowledged that dams affect sediment transport and water quality. To support water management of reservoirs, it is useful to explore how the fractions of phosphorus (P) in sediments were changed after the dam was built. The aim of this study was to assess the spatial and temporal trends of the P fractions in sediments from the Miyun Reservoir, a pivotal drinking water supply for Beijing City, the capital of China. Nine surface sediment samples, together with a sediment core, were collected. The concentrations of total P (TP) and their fractions were then determined by using a sequential extraction method. The results showed that the reservoir was classified into three areas spatially based on the TP concentrations, i.e., high (Baihe area), medium (transitional area), and low (Chaohe area) concentrations. The concentrations of iron-bound P (BD-P) and metal oxide-bound P (NaOH-P) were higher in the Baihe and Chaohe regions than those in the transitional area and tended to increase with water depth. Dam construction can lead to the concentrations of P increased in sediments and further increase the potential of internal P loadings. This study revealed the effect of dam construction on sedimentary P accumulation. The results will be helpful in better understanding the mobility and bioavailability of P in the aquatic ecosystem, which aim to achieve a more highly targeted environmental management for this important region.

Assessment of nitrate leakage and N2O emission from five environmental-friendly agricultural practices using fuzzy logic method and empirical formula.

Agricultural nonpoint source pollution in China has been the major environmental problem, so environmental-friendly agricultural practices (EAPs) must be promoted to improve environmental quality. However, the most suitable practices for each agricultural region must first be identified. Thus, in the presented study a fuzzy-logic method and a revised empirical formula were used to assess nitrate leakage and N2O emissions, respectively, and to compare five EAPs in Xinxiang, a major grain-producing county in Henan Province, China. The required information was collected in face-to-face interviews with 10 extension service experts from the county, using a questionnaire to explore their opinions of the EAPs currently adopted by smallholder farmers, as well as the amounts, frequencies, varieties and proportions of nitrogen fertilizers applied annually. The results indicate that reduced tillage, soil testing and fertilizer recommendations would be the most appropriate practices to initially promote on a large scale in Xinxiang.

CN-China: Revised runoff curve number by using rainfall-runoff events data in China.

The curve number (CN) method developed by the United States Department of Agriculture (USDA) in 1954 is the most common adopted method to estimate surface runoff. For years, applicability of the CN method is a conundrum when implementing to other countries. Specifically, countries with more complex natural environment may require more dedicated adjustments. Therefore, the current CN look-up table provided by USDA might not be appropriate and could be questionable to be applied directly to regions elsewhere. Some studies have been conducted to modify CN values according to specified natural characteristics in scattered regions of mainland China. However, an integral and representative work is still not available to address potential concerns in general matters. In this study, a large set of rainfall-runoff monitoring data were collected to adjust CN values in 55 study sites across China. The results showed that the revised CN values are largely different from CN look-up table provided by USDA, which would lead to huge errors in runoff estimation. In this study, the revised CN (dubbed CN-China) provides better reference guidelines that are suitable for most natural conditions in China. In addition, scientists and engineers from other parts of the world can take advantage of the proposed work to enhance the quality of future programs related to surface runoff estimation.

Impact of human activities on phosphorus flows on an early eutrophic plateau: A case study in Southwest China.

The net anthropogenic phosphorus inputs (NAPI) model has been used extensively to assess changes in phosphorus (P) inputs and cycling in the environment. However, temporary populations have generally been unconsidered in these assessments. In this study, the NAPI model was used to estimate P loads from the 16 towns and villages in the Erhai Lake Basin (ELB), Southwest China and to evaluate the potential impact from temporary residents (tourism). The results showed that the average value P inputs in the basin (estimated at 2384 kg P km-2 year-1) were 5 times the national average level, and that temporary residents contributed 1%. Agriculture accounted for most of the net P, with chemical fertilizers (55% of the inputs) as the main source, followed by food and animal feed. Only 9.54% of the P inputs to the basin were exported. River water quality and NAPI were significantly correlated (P < 0.01). Tourism industry contributes significantly to regional economic growth and prosperity, but its beneficial effects on the economy does not equate with the adverse impact on environment. This study illustrates what is happening in Southwest China and provides scientific evidence that shows we need to find novel ways to reduce nutrients.

Environmentally-friendly agricultural practices and their acceptance by smallholder farmers in China-A case study in Xinxiang County, Henan Province.

Intensive agriculture with high inputs has resulted in rapid development of crop production in China, accompanied by negative environmental effects such as serious non-point source agricultural pollution. Implementation of environmentally-friendly agricultural practices can effectively prevent such pollution. However, the acceptance and adoption of such practices are related not only to associated risks and potential benefits, but also to farmers' attitudes to and knowledge of scientifically validated practices. In the presented study we surveyed views of a stratified sample of 150 smallholder farmers and 10 extension service experts from Xinxiang, a high grain-producing county in Henan Province, China. Their opinions were explored in personal interviews using a questionnaire with three sections. The first section mainly sought information on surveyed farmers' demographic characteristics like gender, age and education. The second section concerned their awareness of the environmental problems and losses of yields associated with customary over-fertilization practices, and their main concerns about new practices. The third section addressed farmers' attitudes to, and the extension service experts' professional evaluations of, five selected practices in terms of the importance of seven factors (time demands, costs, risks, compatibility, complexity, trialability and observability). Acceptance indices were calculated from the responses to rank farmers' willingness to accept the five environmentally-friendly agricultural practices, and thus identify the most appropriate to promote in the study area. The results show that costs, followed by risks and observability, are the more important factors affecting farmers' decisions to adopt a practice. The results also indicate that no or minimum tillage and returning straw to the field are the most appropriate practices to promote initially at large scale in Xinxiang. The others could be popularized gradually after providing effective incentives and training. The finding that cost is the main factor influencing Chinese farmer contrasts with reports that EU farmers rank risk and observability as most important, possibly due to differences in income.

Critical nutrient thresholds needed to control eutrophication and synergistic interactions between phosphorus and different nitrogen sources.

Eutrophication is one of the greatest threats to global freshwater ecosystems. The phytoplankton responses to nutrient inputs vary in different water bodies, so it is particularly important to determine the nutrient thresholds and synergistic interactions between nutrients in different freshwater ecosystems. Field sampling and bioassay experiments were conducted to determine the thresholds of soluble reactive phosphorus (SRP), nitrate-nitrogen (NO3-N), and ammonium-nitrogen (NH4-N) in Miyun Reservoir. A separate nutrient addition bioassay was designed to assess the synergistic interactions between these nutrients. Chlorophyll a (Chl a) concentrations were used to estimate phytoplankton biomass. The results showed the following: (1) nutrient threshold bioassay indicated that eutrophication thresholds of SRP, NO3-N, and NH4-N should be targeted at below 0.04 mg P L-1, 0.5 mg N L-1, and 0.3 mg N L-1, respectively, to limit the growth of phytoplankton. (2) The stimulatory effect of "NH4-N plus P" on phytoplankton biomass was greater than "NO3-N plus P" at the same N concentration, and "NH4-N plus NO3-N" did not show such associated stimulatory effect as "NH4-N plus P" or "NO3-N plus P". (3) The average concentrations of total phosphorus (TP), NO3-N, and NH4-N in Miyun Reservior were 0.017 mg P L-1, 0.620 mg N L-1, and 0.143 mg N L-1, respectively. The reservoir-wide average Chl a is below 20 µg L-1 on an annual basis. (4) Ammonium was an important factor for the growth of phytoplankton and inputs of both NH4-N and NO3-N should be reduced to control bloom formation. Our findings imply that although P load reduction is important, appropriate reductions of all forms of N in watershed is recommended in the nutrient management strategy for Miyun Reservoir.

Estimating internal P loading in a deep water reservoir of northern China using three different methods.

Much attention had been paid to reducing external loading of nutrients to improve water quality, while internal loading from sediment, which has been largely neglected, is also an important source for water eutrophication. The internal load in deep lakes or reservoirs is not easy to be detected and be quantified. In this study, three different methods (mass balance method, Fick's law, and regression equation) were combined to calculate the gross or/and net P release from sediment using limited data. Our results indicated that (1) the methods of mass balance and regression equation give similar results of sediment P release rate, with values of 0.889 and 0.902 mg m(2) d(-1), respectively, while the result of Fick's law was much lower (0.400 mg m(2) d(-1)); (2) Hot periods of sediment releasing were suggested to occur from March to April and from August to September, which correspond to periods of high risks of algae blooms. The remaining months of the year were shown as net nutrient retention; (3) for the whole region, Baihedam and Chaohekuqu were identified as zones with a higher possibility to release P from sediment. (4) P loading to the Miyun Reservoir was greater in the inflow than in the outflow, suggesting a portion of the inflow P load was retained in the water or sediment; hence, release of sediment P may continue to be a major source of phosphorus in the future.

The potential impact of an inter-basin water transfer project on nutrients (nitrogen and phosphorous) and chlorophyll a of the receiving water system.

Any inter-basin water transfer project would cause complex physical, chemical, hydrological and biological changes to the receiving system. The primary channel of the middle route of the South-to-North Water Transfer Project has a total length of 1267 km. There is a significant difference between the physical, chemical and biological characteristics of the originating and receiving drinking water conservation districts. To predict the impacts of this long-distance inter-basin water transfer project on the N&P (nitrogen and phosphorus) concentrations and eutrophication risk of the receiving system, an environmental fluid dynamics code (EFDC) model was applied. The calibrated model accurately reproduced the hydrodynamic, water quality and the entire algal bloom process. Thirteen scenarios were defined to fully understand the N&P and chlorophyll a (Chl a) variation among different hydrological years, different quantity and timing of water transfer, and different inflows of N&P concentrations. The results showed the following: (a) The water transfer project would not result in a substantial difference to the trophic state of the Miyun reservoir in any of the hydrological years. (b) The area affected by the water transfer did not involve the entire reservoir. To minimize the impact of water transfer on N&P nutrients and Chl a, water should be transferred as uniform as possible with small discharge. (c) The variation in Chl a was more sensitive to an increase in P than an increase in N for the transferred water. The increased percentages of the average Chl a concentration when water was transferred in the spring, summer and autumn were 7.76%, 16.67% and 16.45%. Our findings imply that special attention should be given to prevent P increment of the transferred water from May to October to prevent algal blooms. The results provide useful information for decision makers about the quantity and timing of water transfers.