Spatio-temporal variations of nitrogen in an agricultural watershed in eastern China: catchment export, stream attenuation and discharge

Using the monthly hydrogeochemical data of ChangLe River system from 2004 to 2008, total nitrogen (TN) export load (S(n)) from nonpoint sources (NPS) to stream and in-stream attenuation load (A(L)) was estimated by the inverse and forward format of an existing in-stream nutrient transport equation, respectively. Estimated S(n) contributed 96 ± 2% of TN entering the river system, while A(L) reduced the input TN by 23 ± 14% in average. In-stream TN attenuation efficiency in high flow periods (10 ± 5% in average for the entire river system) was much lower than that in low flow periods (39 ± 17%). TN attenuation efficiency in tributaries (28 ± 16% in average) was much higher than that in mainstream (11 ± 8%). Hydrological conditions are important in determining the spatio-temporal distributions of NPS TN export, stream attenuation and discharge. Increasing the water residence time might be a practical method for mitigating stream TN.     

Hierarchical eco-restoration: A systematical approach to removal of COD and dissolved nutrients from an intensive agricultural area

A systematical approach based on hierarchical eco-restoration system for the simultaneous removal of COD and dissolved nutrients was proposed and applied in a complex residential-cropland area in Kunming, China from August 2006 to August 2008, where the self-purifying capacity of the agricultural ecosystem had been lost. The system includes four main parts: (1) fertilizer management and agricultural structure optimization, (2) nutrients reuse, (3) wastewater treatment, and (4) catchment restoration. The results showed that the average removal efficiencies were 90% for COD, 93% for ammonia, 94% for nitrate and 71% for total dissolved phosphorus (TDP) when the hierarchical eco-restoration agricultural system was in a relatively steady-state condition. The emergence of 14 species of macrophytes and 4 species of zoobenthos indicated that the growth conditions for the plankton were improved. The results demonstrated that this promising and environmentally benign hierarchical eco-restoration system could decrease the output of nutrients and reduce downstream eutrophication risk.     

Quantifying groundwater phosphorus flux to rivers in a typical agricultural watershed in eastern China

Environmental Science and Pollution Research - Increasing evidence indicates that groundwater can contain high dissolved phosphorus (P) concentrations, thereby contributing as a potential pollution...     

Combined inverse modeling approach and load duration curve method for variable nitrogen total maximum daily load development in an agricultural watershed

Purpose  

Nonpoint sources (NPS) pollution has been an important cause for water quality impairment worldwide. To take the temporal variations of both NPS pollution and in-stream attenuation into consideration, an inverse modeling approach and the load duration curve (LDC) method were combined for variable nutrient total maximum daily load (TMDL) development.     

上海市青浦区农业非点源污染的流域分配研究

根据遥感技术得到的土地利用类型、河网、道路、圩区等信息,结合地理信息系统(GIS)的空间分析功能,建立了在多种空间因素影响下确定农业非点源污染负荷的流域分配方法。在此基础上,以上海市青浦区为例,得到了该区各河段中的污染负荷量．从而为寻求流域内合理的土地利用模式和农业非点源污染排放总量的控制方法提供决策依据。     

不同生态分区参照湖泊筛选技术方法探讨

中国不同生态分区的湖泊在成因、类型、演变过程、营养物效应以及物理、化学、生物学特性等方面均存在着显著的地域性差异,同时湖泊流域人口密集、社会经济发达,湖泊普遍受人类扰动大,科学地筛选出不同生态分区的参照湖泊是建立生态分区湖泊营养物基准的重要基础。详细介绍了参照湖泊筛选的主要程序、筛选的指标体系和筛选方法,论述了筛选出参照湖泊后的量化评价和检验的方法,以去除不满足要求的参照湖泊。针对中国湖泊特点,分析了中国不同生态分区参照湖泊确定存在的问题和解决方法,以指导不同生态分区参照湖泊的确定。     

Seasonal variations of nitrogen and phosphorus retention in an agricultural drainage river in East China

Background, aim, and scope  

Riverine retention decreases loads of nitrogen (N) and phosphorus (P) in running water. It is an important process in nutrient cycling in watersheds. However, temporal riverine nutrient retention capacity varies due to changes in hydrological, ecological, and nutrient inputs into the watershed. Quantitative information of seasonal riverine N and P retention is critical for developing strategies to combat diffuse source pollution and eutrophication in riverine and coastal systems. This study examined seasonal variation of riverine total N (TN) and total P (TP) retention in the ChangLe River, an agricultural drainage river in east China.     

Spatiotemporal distributions of nutrients in the downstream from Gezhouba Dam in Yangtze River, China

Introduction

From December 2008 to November 2009, an investigation of water quality was performed in the 70-km long downstream from Gezhouba Dam in Yangtze River.

Methods

Twelve sites in all were chosen. Nine parameters of water quality including the total phosphorus, the total nitrogen, chlorophyll a (Chl.a), nitrite, nitrate, ammonia, water temperature, DO, and pH were monitored almost monthly. The multivariate statistical technique (cluster analysis) and the nonparametric method (Kruskal?CWallis Test and Spearman??s rank correlation) were applied to evaluate the spatiotemporal variations of water quality data sets.

Results and discussion

According to the Chinese environmental quality standards for surface water (GB3838-2002), the water quality in the river section investigated can attain to the III water standards except total nitrogen. Further analysis indicated that there were no significant spatial differences in these parameters of water quality, but the sampling date had a significant effect. The temporal variation of water quality can be related to the discharge of Gezhouba Dam and moreover be affected by the reservoir regulation. During the discharge, the discharge increased the concentration of total phosphorus and then decreased the N:P ratio, which helps to the occurrence of algae blooms. The high consternation of phosphorus and the low N:P ratio show that the water body can be in the process of eutrophication during the discharge of Gezhouba Dam. In fact, Chl.a had begun to rise in the same period.     

A method for developing ozone exposures that mimic ambient conditions in agricultural areas

Ozone fumigations that mimic ambient ozone distributions facilitate the development of links between

• 1.(1) vegetative effects results that are generated in the laboratory and the field and
• 2.(2) predictive effects models that depend upon ambient air quality data.

Experimental exposure profiles were constructed from a readily available ambient air quality data base (i.e. EPA SAROAD). Air quality data from selected monitoring sites were characterized over the 5-month growing season by identifying

• 1.(a) the number of occurrences of hourly ozone concentrations equal to or above 0.07 ppm,
• 2.(b) the number of days of each episode,
• 3.(c) the number of days between episodes and
• 4.(d) the rate of rise and decline of the daily ozone concentrations.

An episodic profile was constructed incorporating the information into a representative 30-day ozone exposure pattern in which the concentration was changed on an hourly basis. In order to compare treatments having equivalent exposures (sum of hourly ozone concentrations equal to or above a minimum value) but dissimilar temporal distributions of hourly concentrations, a second profile was created. This profile was characterized by a repeated daily incremental rise and decline in ozone concentration that had the same hourly maximum concentration each day. The use of experimental exposure profiles mimicking ambient air quality characteristics and applied under controlled experimental conditions permits the examination of important exposure parameters on plant response.     

Perspectives and challenges in the future use of plant nutrients in tilled and mixed agricultural systems

Producing an adequate quantity of healthy food without polluting the environment is a serious challenge for future agriculture around the world. The Food 21 research program in Sweden has researched all aspects--economic, environmental, and social--of sustainable farming systems. This paper presents some of the research from that and other relevant international research programs that have focused on better nutrient-use efficiency, especially for nitrogen and phosphorus. It shows that a range of sustainable solutions to nutrient-use efficiency exists, some of which are complex but some very simple. Government policies, including subsidies; research and technology; and public acceptance of farming practices all combine to create these solutions. Participatory approaches to knowledge transfer are needed, in which scientists, policy makers, farmers, advisers, and consumers exchange information and together build sustainable farming systems.     

Selecting low-carbon technologies and measures for high agricultural carbon productivity in Taihu Lake Basin,China

Environmental Science and Pollution Research - In this paper, Delphi method was used to evaluate the low-carbon technologies and measures for high agricultural carbon productivity in Taihu Lake...     

Occurrence and source characterization of perfluorochemicals in an urban watershed

Perfluorochemicals (PFCs) are used in numerous applications, mainly as surfactants, and occur ubiquitously in the environment as complex mixtures. This study was undertaken to characterize the occurrence and sources of commonly detected PFC compounds in surface waters of the Marina catchment, a watershed that drains an urbanized section of Singapore. Of the 19 target PFCs, 13 were detected with perfluorooctanoic acid (PFOA) (5-31 ng L⁻¹) and perfluorooctane sulfonate (PFOS) (1-156 ng L⁻¹) being the dominant components. Other compounds detected included perfluoroalkyl carboxylates (C7-C12) and perfluoroalkyl sulfonates (C6 and C8). Sulfonamide compounds detected 2-(N-ethylperfluorooctanesulfonamido) acetic acid (N-EtFOSAA), 2-(N-methylperfluorooctanesulfonamido) acetic acid (N-MeFOSAA), perfluorooctanesulfonamido acetic acid (FOSAA) and perfluorooctanesulfonamide (FOSA) were putative transformation products of N-EtFOSE and N-MeFOSE, the N-ethylated and N-methylated ethyl alcohol derivatives, respectively. Surface water concentrations were generally higher during dry weather than during storm water flow: the median concentrations of total PFCs in dry and wet weather were 57 and 138 ng L⁻¹ compared to 42 and 79 ng L⁻¹, respectively, at Stamford and Alexandra canal, suggesting the presence of a continuous source(s) which is subject to dilution during storm events. In rain water, median concentrations were 6.4 ng L⁻¹, suggesting rain contributed from 12-25% to the total PFC load for non-point source sites. The longitudinal concentration profile along one of the canals revealed a point source of sulfonated PFCs (PFOS), believed to originate from aqueous film-forming foam (AFFF). Sources were characterized using principal component analysis (PCA) and by plotting PFHxS/PFOA against PFOS/PFOA. Typical surface waters exhibit PFOS/PFOA and PFHxS/PFOA ratios below 0.9 and 0.5, respectively. PCA plots reveal waters impacted by “non-typical” PFC sources in Alexandra canal.     

Heavy metals in agricultural soils of the Pearl River Delta,South China

There is a growing public concern over the potential accumulation of heavy metals in agricultural soils in China owing to rapid urban and industrial development and increasing reliance on agrochemicals in the last several decades. Excessive accumulation of heavy metals in agricultural soils may not only result in environmental contamination, but elevated heavy metal uptake by crops may also affect food quality and safety. The present study is aimed at studying heavy metal concentrations of crop, paddy and natural soils in the Pearl River Delta, one of the most developed regions in China. In addition, some selected soil samples were analyzed for chemical partitioning of Co, Cu, Pb and Zn. The Pb isotopic composition of the extracted solutions was also determined. The analytical results indicated that the crop, paddy and natural soils in many sampling sites were enriched with Cd and Pb. Furthermore, heavy metal enrichment was most significant in the crop soils, which might be attributed to the use of agrochemicals. Flooding of the paddy soils and subsequent dissolution of Mn oxides may cause the loss of Cd and Co through leaching and percolation, resulting in low Cd and Co concentrations of the paddy soils. The chemical partitioning patterns of Pb, Zn and Cu indicated that Pb was largely associated with the Fe-Mn oxide and residual fractions, while Zn was predominantly found in the residual phase. A significant percent fraction of Cu was bound in the organic/sulphide and residual phases. Based on the 206Pb/207Pb ratios of the five fractions, it was evident that some of the soils were enriched with anthropogenic Pb, such as industrial and automobile Pb. The strong associations between anthropogenic Pb and the Fe-Mn oxide and organic/sulphide phases suggested that anthropogenic Pb was relatively stable after deposition in soils.     

Body burdens of polybrominated diphenyl ethers in childbearing-aged women at an intensive electronic-waste recycling site in China

Background, aim and scope  

This study is the first to investigate PBDE body burden with regard to the concurrent analyses of multiple human matrices, namely milk, placenta, and hair, collected from a group of childbearing-aged women at an electronic waste (e-waste) recycling site to determine the partitioning of PBDEs in these different human matrices and the possible health risks imposed to infants at the e-waste recycling site.     

Annual input fluxes of heavy metals in agricultural soil of Hainan Island,China

The accumulation of heavy metals in farmland has become an important issue related to food security and environmental risk. The annual inputs of heavy metals (As, Cd, Hg, Pb, Cr, Cu, and Zn) to agricultural soil for a full year in Hainan Island have been studied. Three fluxes through the cultivated horizon were considered: (1) atmospheric depositions, (2) fertilization, and (3) irrigation water. The corresponding samples were collected and analyzed on a large regional scale. The total input fluxes show obvious spatial variability among different regions. The inventory of heavy metal inputs to agricultural land demonstrates that agricultural soil is potentially at risk of heavy metal accumulation from irrigation water. The potential at risk of heavy metal accumulation from atmospheric deposition and fertilizer is relatively low compared to irrigation. The results indicate that Hg is the element of prior concern for agricultural soil, followed by Cd and As, and other heavy metal elements represent little threat to the environment in the study area. This work provides baseline information to develop policies to control and reduce toxic elements accumulated in agricultural soil.     

Distribution of polycyclic aromatic hydrocarbons in water, suspended particulate matter and sediment from Daliao River watershed, China

This study investigated the spatial distribution of polycyclic aromatic hydrocarbons (PAHs) in surface water, suspended particulate matter (SPM) and sediment of Daliao River watershed composed of the Hun River, Taizi River, and Daliao River. The sources of PAHs were evaluated employing ratios of specific PAHs compounds and principal component analysis (PCA). The total concentrations of PAHs ranged from 946.1 to 13448.5 ng l(-1) in surface water, from 317.5 to 238518.7 ng g(-1) dry weight in SPM, and from 61.9 to 840.5 ng g(-1) dry weight in sediments. The levels of PAHs are relatively higher in water and SPM, and lower in sediments, in comparison with those reported for other rivers and marine systems around the world. The composition of PAHs in these mediums was mainly 4-6 rings PAHs. The higher contents of low molecular weight PAHs in the water and SPM suggest a relatively recent local source of PAHs, entered into the river via wastewater discharge and atmospheric way. On the other hand, the heavy pollution of PAHs in sediment and water near heavy industrial area suggests that PAHs have been released from industrial wastewater.     

Nitrogen fertilization, soil nitrate accumulation, and policy recommendations in several agricultural regions of China

Excessive nitrogen (N) fertilization and decreasing N recovery rates by crops have caused dramatic increases in non-point source pollution from agriculture in China. The rate of N fertilization across the country varies widely among regions and crops, depending on the stage of economic development. For example, N application rates in the eastern regions and on cash crops are far higher than in western regions of the country and on cereal crops. Moreover, N application rates in wealthier regions are higher than recommended by the Chinese Academy of Sciences. To successfully achieve environmental protection as well as high crop yields, China must formulate relevant agricultural policies to encourage farmers in economically developed areas to reduce their N fertilization rate while also issuing conventional fertilization recommendations for small-scale farming systems and the expanding cultivation of cash crops.     

NOX fluxes from three kinds of agricultural lands in the Yangtze Delta,China

Static chamber method was adopted to measure the surface exchanges of NO and NO₂ between three kinds of agricultural lands and the atmosphere during spring–summer period in the Yangtze Delta, China. The average NO fluxes were 20.9, 27.4 and 21.4 ng N m⁻² s⁻¹, respectively, for cabbage (CA, cultivation of celery occurred along with cabbage), potato (PO) and soybean (SY) fields. The average NO₂ fluxes were −1.12, 0.93 and −0.68 ng N m⁻² s⁻¹, respectively, for the cabbage, potato and soybean fields. Apparently, negative linear correlation was found between the NO₂ fluxes from the CK plot (tilled conventionally but did not cultivate any seeds) and its ambient concentrations, and the compensation point was calculated to be 0.92 ppbv. The total NO emission from the vegetable lands and SY land in this region during spring–summer period was roughly estimated to be 15.9 Gg N, which accounted for about 11.2% of the estimated value of total NO emissions in the July of 1999 from Chinese agricultural fields.     

Behavior of bensulfuron-methyl in an agricultural alkaline soil

A field experiment to determine the available bensulfuron-methyl (BSM) in the upper soil layer was conducted in an agricultural area in the South of Spain. To facilitate herbicide analysis, two application rates were employed, 200 g ha(-1) and 5 kg ha(-1). Samples of upper soil and soil solution were collected. Soil solution was sampled by means of metallic samplers, placed at a depth of 35 cm. In the plots receiving the lower dose ceramic suction, porous cups were also installed. Results from soil solution samples showed that the maximum BSM concentration was found after 8-10 days for the high irrigation supply (945 mm) and after 18-25 days for the lower irrigation regime (405 mm). The mathematical model FOCUSPELMO 1.1.1 was applied to interpret the data obtained in the field experiments. In general, there was a reasonable agreement between experimental and simulated data for soil samples, although the model did not acceptably predict herbicide concentrations in water soil samples. Ceramic cups sampled a higher soil water volume and more frequently than did the metallic samplers. However some variable results were attributed to preferential flow.     

Genotoxicity of surface water samples from Meiliang Bay, Taihu Lake, Eastern China

Taihu Lake is the third largest freshwater lake in China. Taihu Basin is one of the most densely populated and urbanized areas in this country. This area provides 15% of the GDP. Meiliang Bay is located in the north part of the Lake. It provides the municipal water source for Wuxi City. Some parts of the lake have been found to be highly polluted due to eutrophication for over a decade. Surface water (0-0.5 m) samples were collected from the Meiliang Bay by the aid of Global Position System (GPS) for positioning. Water samples were concentrated 5000 times with XAD-2 resin columns. A reverse mutation test using histidine-dependent Salmonella typhimurium strains was employed to assay the genotoxicity of the samples. The results showed that the sample from position 6 had the highest genotoxicity either in the case of activating with eucaryotic S9 system or without S9. The genotoxic effect included, at least, two different molecular mechanisms: nucleotide point substitution on DNA molecules and reading frame shifting caused by nucleotide insertion or deletion. The genotoxicity of the water body in Meiliang Bay, Taihu Lake should be kept in close monitoring.