Nonpoint Source Pollution Reduction Research Articles

城市景观格局演变的水环境效应研究综述

PDF HTML阅读 XML下载 导出引用 引用提醒 城市景观格局演变的水环境效应研究综述 DOI: 10.5846/stxb201306071391 作者: 作者单位: 中国科学院城市环境研究所;中国科学院大学,中国科学院城市环境研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（30800148）；厦门市科技计划项目（3502Z20122001） Research review on effects of urban landscape pattern changes on water environment Author: Affiliation: Institute of Urban Environment, Chinese Academy of Sciences,Institute of Urban Environment, Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:人类活动导致的城市土地利用覆被变化在景观生态学上表现为城市景观类型的更替和城市景观格局的演变。我国城市景观格局中自然植被景观基质大幅被人工硬化地面所取代，自然景观斑块破碎化，城市道路和排水管网等人工廊道大量增加，造成“源”“汇”景观的比例失衡和格局失调，从而产生城市景观格局演变的水环境负效应，如非点源污染、水生生态系统失衡和城市内涝等，且水环境负效应存在时间尺度差异和空间尺度响应多样性。对城市景观类型及其格局演变产生的城市水环境效应相关研究进行总结，针对现有研究中存在的城市景观格局演变带来的生态过程变化研究较少、影响城市水环境的景观格局变化阈值不明确、研究结果推广难和重复性较差、人工廊道与城市水环境效应关系关注度较低和水环境负效应综合度研究欠缺等不足之处，提出未来研究的着力点，对实现可持续城市具有一定意义。 Abstract:Urban water environment is an important part of urban ecosystem including natural and man-made water, and the natural elements and urban landscape which are closely related to water at catchment scale. Healthy urban water environment could product positive ecological effects such as water retention and impoundment, environmental decontamination, material transportation, making energy flow smoothly and conserving biodiversity. However, the change of urban land cover induces the deterioration of urban water environment and leads to negative water environment effects, such as non-point pollution, imbalance of aquatic ecosystem and urban flooding. The replacement of urban landscape types and evolution of urban landscape pattern caused by human activities display at following aspects: widespread vegetation matrix is largely replaced by artificial hardened ground while natural landscape patches are fragmentized and manual corridors including urban roads and drainage network increase sharply, resulting in the disproportion of water pollution "source" and "sink" landscape types and landscape pattern. Through statistical analysis and model simulation, researchers at home and abroad find that: the cultivated land and urban construction land are the main sources of non-point pollution while natural vegetation landscape types contribute to the reduction of non-point source pollution. Urban surface hardening reduces the environmental capacity of urban water environment by influencing urban hydrological cycle, for instance, surface runoff, evaporation and infiltration and so on. Together with environmental capacity reduction, the eutrophication of urban water environment makes negative effects on the balance of aquatic ecosystem. Negative water environment effects responding to urban landscape pattern will change with spatial and temporal scales. This paper summarizes current researches about the effects of urban landscape types and pattern evolution on water environment and points out the deficiencies of recent researches, such as the lack of specific research coupling landscape pattern change and ecological process, the indeterminacy of the landscape pattern threshold influencing urban water environment, the difficulty in popularizing and repeating research results, neglecting the relationship between urban artificial corridor and water environment effects, and the lack of comprehensive research about negative water environment effects. At last, we put forward five key points of future researches: the lagging response of urban water environment to the change of urban landscape pattern; the differences of water environment effects with different types and distributions; the combined influences from the urban landscape pattern, including matrix, corridor and patch; development of new model which concentrates on urban water environmental effects; a set of related index for urban planning and urban water environmental effects. Our study will contribute to better understanding of urban sustainability. 参考文献 相似文献 引证文献

논의 양분유출 저감을 위한 저류지 효과

BACKGROUND: Water-born pollution loads by agricultural non-point source (NPS) pollution are expected to become intensified due to ongoing precipitation change. Therefore, it is essential to develop a best management practice (BMP) that is suitable to agricultural environments in Korea. This study aimed to develop an environmental-friendly BMP to reduce NPS pollution load by agricultural activities. An eco-friendly way, small drainage pond, was suggested in this study to avoid direct drainage of agricultural runoffs and eventually reduce the amount of pollutants discharged into the surrounding aqua-environment. METHODS AND RESULTS: A small pond (12 m 2 ) was constructed at the corner of a rice paddy field (1,715 m 2 ) located in Suwon, Korea. Water was allowed to drain only via a small drainage pond. Sampling was repeatedly made at two locations, one from an entrance and the other from an exit of a pond, during the rice cultivation period (May to

Evaluation of agricultural nonpoint source pollution potential risk over China with a Transformed-Agricultural Nonpoint Pollution Potential Index method

Agricultural nonpoint source (NPS) pollution has been the most important threat to water environment quality. Understanding the spatial distribution of NPS pollution potential risk is important for taking effective measures to control and reduce NPS pollution. A Transformed-Agricultural Nonpoint Pollution Potential Index (T-APPI) model was constructed for evaluating the national NPS pollution potential risk in this study; it was also combined with remote sensing and geographic information system techniques for evaluation on the large scale and at 1 km2 spatial resolution. This model considers many factors contributing to the NPS pollution as the original APPI model, summarized as four indicators of the runoff, sediment production, chemical use and the people and animal load. These four indicators were analysed in detail at 1 km2 spatial resolution throughout China. The T-APPI model distinguished the four indicators into pollution source factors and transport process factors; it also took their relationship into consideration. The studied results showed that T-APPI is a credible and convenient method for NPS pollution potential risk evaluation. The results also indicated that the highest NPS pollution potential risk is distributed in the middle-southern Jiangsu province. Several other regions, including the North China Plain, Chengdu Basin Plain, Jianghan Plain, cultivated lands in Guangdong and Guangxi provinces, also showed serious NPS pollution potential. This study can provide a scientific reference for predicting the future NPS pollution risk throughout China and may be helpful for taking reasonable and effective measures for preventing and controlling NPS pollution.

CATCHMENT WATER QUALITY MANAGEMENT PLANNING FOR SUSTAINABLE DEVELOPMENT OF TIDAL AREAS

ABSTRACTControlling the water quality of a freshwater reservoir that has been created by a tidal land reclamation project is never easy and presents great challenges to engineers and administrators. One of the major factors affecting the water quality of a freshwater reservoir created by tidal area development is pollution entering from catchment areas through rivers and streams. Pollution in a catchment is classified by two sources, point source and nonpoint source (NPS) pollution. Point source pollution must be eliminated by adopting cutting‐edge treatment technologies, while NPS pollution is controlled and managed effectively by adopting best management practices (BMPs) in both rural and urban areas for a sustainable development of tidal areas. About 70% of total pollution is NPS pollution and strategies and policies need to be adopted to counter this. NPS pollution is mostly generated and transported by rainfall runoff and groundwater. It is very important to make every effort to minimize runoff during rainfall to reduce NPS pollution. Both runoff and groundwater qualities can be controlled and managed successfully by applying BMPs, enforcing strict legal requirements and supporting participatory catchment management activities. Principles of natural attenuation mechanisms must be applied together with BMPs to ensure the fast and effective decomposition and transformation of the pollutants removed by BMPs. In addition to technological approaches, systematic support for ongoing education, incentives, and legal enforcement of antipollution laws can all help to encourage participatory catchment management activities. Copyright © 2013 John Wiley & Sons, Ltd.

Assessing the Effects of Land Use Changes on Non-Point Source Pollution Reduction for the Three Gorges Watershed Using the SWAT Model

This study presents a new attempt of applying the hydrological model SWAT to the Three Gorges watershed in China for addressing its non-point source (NPS) pollution control issues. The model was calibrated and validated using the monitoring data collected during 2002-2008, and satisfactory values of R^2 and ENS (Nash-Suttclife Efficiency) were obtained. The calibrated SWAT model was then used to simulate 6 different land use scenarios for investigating the effects of each scenario on the non-point source (NPS) pollution control in the watershed. Six scenarios were designed with distinct land use focuses and include five newly-designed scenarios (Q1-Q5) representing 5 different land use alternatives and a baseline scenario (Q6) representing the land use pattern the watershed had in 2005. It was identified that the farmland is the dominant contributor to the NPS pollution in the watershed in terms of yields of sediment, TN and TP. If the farmland is changed to the woodland, grassland or shrubland, a better control and reduction over the NPS pollution could be achieved. This study provides a good understanding of the interactions between different land use patterns and the NPS pollution control for decision-makers to make sound decisions. Changing the land use pattern and implementing alternative management practices could help reduce the non-point source pollution effectively and thus play a significant role in improving reservoir water quality of the watershed.

Effects of Typical Chemical Agents on Preventing Pollution and Controlling Drought in a Cherry Orchard

In the North China plain, serious Non-point-source (NPS) pollution and drought are two great concerns in agricultural production. In our studies, two typical chemical agents ( SAP and FA ) were selected to control drought and pollution in a cheery orchard. Soil water content, nutrient transport in soil profile have been researched. The results showed that the soil water content of treatments with chemical agents increased maximally by 19.4% relative to treatment without chemical agents, and increased by 35.2% for Ammonium-N in 20-60 cm soil layer ( main root zone ). However, in 60-120 cm deeper soil layer, the water leakage of treatments with chemical agents decreased averagely by 15.1% relative to treatment without chemical agents, and increased by 43.8% for Nitrate-N. The chemical agents hold water and nutrient in root zone and thus reducing the risk of pollutant leaching into the underground water. It can be found that treatment ( 150kg/h㎡ SAP + 300 times FA ) is the optimal combination group in all treatments. The chemical prevention technology provided a new guide for controlling drought and reducing NPS pollution in cherry planting in the North China plain.

Effects of Typical Chemical Agents on Prevention of Non-Point-Source (NPS) Pollution in a Sloping Orchard

In this paper, two typical chemical agents SAP and PAM were selected to reduce NPS pollution. Soil water content, nutrient transport and soil erosion have been researched. The results showed that the water deep percolation was reduced and the moisture of root zone increased by 3.6%-12.69% after chemical agents application; PAM can immobile soil grains, and significantly reduce soil erosion on sloping land by 25.5%-53.4%. The synergies of PAM and SAP can significantly influence transport of nutrients in the soil vertical profile, moreover, the content of nutrient was enriched in root zone that the content of Nitrate-N increased 14.7% and Ammonium-N increased 9.8%. It can been found that CL2 (SAP150 kg/k㎡+PAM4.5 kg/k㎡) treatment is superior to CL1 (SAP150 kg/k㎡+PAM2.25 kg/k㎡) in soil moisture conservation and reducing NPS pollution in two slopes orchards.

Experimental research on reduction of agricultural non-point source pollution using pond wetland

Experimental research on reduction of agricultural non-point source pollution using pond wetland

Modelling nitrate transport under row intercropping system: Vines and grass cover

Summary In the context of reduction of agricultural non-point source pollution, an associated crop system often presents several advantages. The difficulty resides in the characterisation of each species’ contribution (dominant and dominated). This paper deals with the particular case of voluntary grass cover management between rows in a vine plot. We evaluate the spatial and temporal changes in the development of both crops: vine/grass cover system, in their ecological functioning and in the influences on water and nitrogen balances. We modify the SWMS_3D model to incorporate separate distribution of water and nitrogen demands for the two coexisting plant species. The parameterized model is then assessed using the measured data (water content, matrix potential and nitrogen content of the soil solution at depths of 30, 60, 90 and 120 cm) acquired from two monitored vine plots (vine “Tockay-Pinot Gris” plot grass covered every second row compared to a control plot that was chemically weeded vine “Riesling” plot, France, Alsace, Rouffach) between October 1998 and September 2000. The main results are the following. The vine’s mean total transpiration over the two growing seasons of 1998/1999 and 1999/2000 is simulated of 355 ± 9 mm per season. The matrix potential is reproduced accurately especially improving with depth and under the interrow. Despite a high variability due to soil heterogeneity, the nitrogen mass variations between measurements and simulations with the adapted model are coherent. Nevertheless we note that the model slightly underestimates the nitrogen mass for both types of observed cropping patterns, however the ratio between the two itineraries remains similar, yielding a reduction in nitrogen loss by at least 4-fold in favour of grass cover every second row plot during the period observed from 10/01/1998 to 09/30/2000.

Feasibility of SRI methods for reduction of irrigation and NPS pollution in Korea

An experimental study on the System of Rice Intensification (SRI) methods was conducted to investigate the feasibility of using them to conserve irrigation water and reduce non-point source (NPS) pollution in Korea. Eight experimental runoff plots were prepared at an existing paddy field. Runoff and water quality were measured during the 2010 growing season in which a Japonica rice variety was cultivated. The irrigation water requirements of SRI methods and conventional (CT) plots were 243.2 and 547.3 mm, respectively, meaning that SRI methods could save 55.6% of irrigation water. Runoff from SRI methods plots decreased 5–15% compared with that from CT plots. Average NPS pollutant concentrations in runoff from SRI methods plots during rainfall-runoff events were SS 89.4 mg/L, CODCr 26.1 mg/L, CODMn 7.5 mg/L, BOD 2.0 mg/L, TN 4.2 mg/L, and TP 0.4 mg/L. Except for CODCr and TN, these concentrations were significantly lower than those from CT plots. Measured pollution loads from SRI methods plots were SS 874 kg/ha, CODCr 199.5 kg/ha, CODMn 47 kg/ha, BOD 13 kg/ha, TN 36.9 kg/ha, and TP 2.92 kg/ha. These were 15.8–44.1% lower than those from CT plots. Rice plants grew better and healthier in SRI methods plots than in CT plots. However, rice production from SRI methods plots ranged between 76 and 92% of that of CT plots because the planting density in SRI methods plots was too low. It was concluded that SRI methods could be successfully adopted in Korea and could help save a significant amount of irrigation requirement in paddies and reduce NPS pollution discharge.

Agricultural Non-Point Source Pollution in China: Causes and Mitigation Measures

Non-point source (NPS) pollution has been increasingly serious in China since the 1990s. The increases of agricultural NPS pollution in China is evaluated for the period 2000-2008 by surveying the literature on water and soil pollution from fertilizers and pesticides, and assessing the surplus nitrogen balance within provinces. The main causes for NPS pollution were excessive inputs of nitrogen fertilizer and pesticides, which were partly the result of the inadequate agricultural extension services and the rapid expansion of intensive livestock production with little of waste management. The annual application of synthetic nitrogen fertilizers and pesticides in China increased by 50.7 and 119.7%, respectively, during 1991-2008. The mitigation measures to reduce NPS pollution include: correct distortion in fertilizer prices; improve incentives for the recycling of organic manure; provide farmers with better information on the sound use of agro-chemicals; and tighten the regulations and national standards on organic waste disposal and pesticides use.

An assessment of landscape characteristics affecting estuarine nitrogen loading in an urban watershed

Exploring the quantitative association between landscape characteristics and the ecological conditions of receiving waters has recently become an emerging area for eco-environmental research. While the landscape-water relationship research has largely targeted on inland aquatic systems, there has been an increasing need to develop methods and techniques that can better work with coastal and estuarine ecosystems. In this paper, we present a geospatial approach to examine the quantitative relationship between landscape characteristics and estuarine nitrogen loading in an urban watershed. The case study site is in the Pensacola estuarine drainage area, home of the city of Pensacola, Florida, USA, where vigorous urban sprawling has prompted growing concerns on the estuarine ecological health. Central to this research is a remote sensor image that has been used to extract land use/cover information and derive landscape metrics. Several significant landscape metrics are selected and spatially linked with the nitrogen loading data for the Pensacola bay area. Landscape metrics and nitrogen loading are summarized by equal overland flow-length rings, and their association is examined by using multivariate statistical analysis. And a stepwise model-building protocol is used for regression designs to help identify significant variables that can explain much of the variance in the nitrogen loading dataset. It is found that using landscape composition or spatial configuration alone can explain most of the nitrogen loading variability. Of all the regression models using metrics derived from a single land use/cover class as the independent variables, the one from the low density urban gives the highest adjusted R-square score, suggesting the impact of the watershed-wide urban sprawl upon this sensitive estuarine ecosystem. Measures towards the reduction of non-point source pollution from urban development are necessary in the area to protect the Pensacola bay ecosystem and its ecosystem services.

Detecting the effect of land-use change on streamflow, sediment and nutrient losses by distributed hydrological simulation

► We develop a physically based non-point source pollution model. ► The model simulates long-term runoff, sediment, and pollutant variations. ► Land-use and climate changes affect catchment hydrology as evaluated quantitatively. ► Climate variability causes annual runoff decline in the study area from 1980–2005. ► Land-use changes had different effects on runoff, sediment, TN, and TP loads. Water shortage and water pollution are two major water issues in Northern China. In recent decades, the decrease in inflow and the deterioration of water quality in the Miyun Reservoir have affected the water supply in Beijing. This paper presents a geomorphology-based non-point source pollution (GBNP) model that links the processes of rainfall–runoff, soil erosion, sediment routing, and pollutant transport. On the basis of long-term simulation of the GBNP model, annual runoff presented a decreasing trend from 1980 to 2005. Total nitrogen (TN) and total phosphorus (TP) loads increased from the early 1980s to the mid-1990s, and then decreased after 1999. The decrease in precipitation and increase in air temperature were the dominant factors in runoff decrease. Afforestation, a water–soil conservation practice, positively affected the reduction of non-point source pollution; however, it also caused a reduction of streamflow. A comparison between 1980–1998 and 1999–2005 showed that land-use changes accounted for 39.1% and 23.7% of the decrease in TN and TP, respectively, as well as 6.6% and 9.2% of the decline in streamflow and sediment load, respectively. Although annual sediment, as well as TN and TP loads decreased after 1999, their long-term accumulation in the reservoir continues to diminish water quality.

지표피복재 적용을 통한 비점오염원 저감효과 분석

Effect of rice straw mat and wood shaves on the reduction of runoff and nonpoint source (NPS) pollution loads from field plots were experimentally studied. Three runoff plots of m in size and 3 % in slope were prepared on a loamy sand field. Each plot was equipped with a flume to measure runoff and collect water samples. Experimental treatments of surface cover were bare, wood shaves (1,000 kg/ha) and rice straw mat cover (3,000 kg/ha). Under radish was cultivation. During the growing season of the radish, three rainfall-runoff events were monitored. Effect of wood shaves and straw mat cover on runoff reduction was 4~30 % and 33~75 % respectively compared to control. The effect on NPS pollution reduction was 36.8 and 64.3 % in BOD, 41.1 and 80.8 % in SS, 34.0 and 56.1 % in TP and 28.0 and 56.6 % in TN respectively. It was analyzed that the reduction of runoff and NPS pollution were mainly contributed by the decrease of rainfall energy impact and flow velocity and the increase of infiltration due to the surface cover materials. Rice straw mat showed very stable soil cover while large portion of wood shaves were lost during heavy storm events. It was concluded that straw mat was an efficient cover material to reduce NPS pollution from upland fields.

Agroforestry Buffers for Nonpoint Source Pollution Reductions from Agricultural Watersheds

Despite increased attention and demand for the adoption of agroforestry practices throughout the world, rigorous long-term scientific studies confirming environmental benefits from the use of agroforestry practices are limited. The objective was to examine nonpoint-source pollution (NPSP) reduction as influenced by agroforestry buffers in watersheds under grazing and row crop management. The grazing study consists of six watersheds in the Central Mississippi Valley wooded slopes and the row crop study site consists of three watersheds in a paired watershed design in Central Claypan areas. Runoff water samples were analyzed for sediment, total nitrogen (TN), and total phosphorus (TP) for the 2004 to 2008 period. Results indicate that agroforestry and grass buffers on grazed and row crop management sites significantly reduce runoff, sediment, TN, and TP losses to streams. Buffers in association with grazing and row crop management reduced runoff by 49 and 19%, respectively, during the study period as compared with respective control treatments. Average sediment loss for grazing and row crop management systems was 13.8 and 17.9 kg ha yr, respectively. On average, grass and agroforestry buffers reduced sediment, TN, and TP losses by 32, 42, and 46% compared with the control treatments. Buffers were more effective in the grazing management practice than row crop management practice. These differences could in part be attributed to the differences in soils, management, and landscape features. Results from this study strongly indicate that agroforestry and grass buffers can be designed to improve water quality while minimizing the amount of land taken out of production.

Impact of crop rotations on optimal selection of conservation practices for water quality protection

This research integrates modern multiobjective optimization tools, water quality modeling capability, and data on costs of implementing conservation practices to develop a tradeoff frontier of cost-efficient nonpoint source pollution reduction solutions, which can be used to derive the watershed-level pollution abatement cost curve. Farmers9 decisions, both on the intensive and the extensive margin, are likely to affect the shape of the tradeoff frontier as well as the mix of conservation practices selected for achievement of given nutrient reduction goals. In this paper, we wish to explore the consequences of changes in the cropping practices on the intensive margin and changes in the amount of cropland on the extensive margin on the baseline water quality as well as the shape of the tradeoff frontier and the mix of conservation practices. An empirical application focuses on a typical Midwestern agricultural watershed, Squaw Creek watershed in central Iowa. Using detailed crop production budgets, we follow Secchi and Babcock (2007) to demonstrate an alternative land-use scenario, which could arise from recently observed changes in crop prices and production costs. We find that the change in cropping practices effects direct changes in the shape of the tradeoff frontier and the mix and location of conservation practices selected to achieve particular nutrient loading reductions. In particular, we find that a potential shift to more corn (<i>Zea mays</i> L.)-intensive crop rotations and an increase in the amount of cropland in the watershed may lead to increased loadings of both nitrate and phosphorus and that additional conservation investments are required to maintain water quality gains achieved under the baseline (historic) cropping practices. In terms of conservation practices selected, the optimal placement of terraces appears robust to the changes in crop rotations and amount of cropland in the alternative land-use scenario.

Effects of planting orientation and density of willows on biomass production and nutrient leaching

Willow buffer strips are a promising vegetated filter for the reduction of non-point source pollution from agricultural land to watercourses resulting from the rapid growth of shoots and from the large amount and distribution of roots. A greenhouse experiment tested the hypothesis that a new planting method, planting cuttings horizontally, exhibited more biomass production and more effective filter than did planting cuttings vertically. Due to the different times taken for shoots break through the soil surface, the summed height of all shoots of horizontally planted cuttings was significantly smaller than that of the vertical ones at the beginning of the growth period. The difference in the height of all of the shoots between planting orientations decreased with time. After 16 weeks growth, the biomass of the stem, leaves and fine roots was not affected by the planting orientation. The coarse root biomass was larger in the horizontal treatments and decreased with increased density. The total biomass, as well as the biomass of stem or leaves, of each treatment, increased with increased planting density. The individual plant biomass, as well as that of the stem or leaves, decreased with increased planting density. Compared with the unplanted control treatment, the planted treatments significantly reduced the total-N, NO3-N, PO4-P and SO4-S leaching. The planting orientation did not affect the nitrate leaching. The horizontally planted cuttings were slightly more effective for reducing the SO4-S leaching and the vertically planted cuttings were slightly more effective for reducing the PO4-P leaching. Lower PO4-P leaching was observed only with higher planting density. With regard to the horizontal planting method, further studies are needed to explore the influence of different willow clones, the size of cuttings, pre-planting treatments, planting geometry (configuration) and soil conditions on survival, the number of shoots produced, the biomass production and the amount and distribution of roots.

Evaluation of non-point source pollution reduction by applying Best Management Practices using a SWAT model and QuickBird high resolution satellite imagery

This study evaluated the reduction effect of non-point source pollution by applying best management practices (BMPs) to a 1.21 km 2 small agricultural watershed using a SWAT (Soil and Water Assessment Tool) model. Two meter QuickBird land use data were prepared for the watershed. The SWAT was calibrated and validated using daily streamflow and monthly water quality (total phosphorus (TP), total nitrogen (TN), and suspended solids (SS)) records from 1999 to 2000 and from 2001 to 2002. The average Nash and Sutcliffe model effciency was 0.63 for the streamflow and the coeffcients of determination were 0.88, 0.72, and 0.68 for SS, TN, and TP, respectively. Four BMP scenarios viz. the application of vegetation filter strip and riparian buffer system, the regulation of Universal Soil Loss Equation P factor, and the fertilizing control amount for crops were applied and analyzed.

A Review of Vegetated Buffers and a Meta‐analysis of Their Mitigation Efficacy in Reducing Nonpoint Source Pollution

Vegetated buffers are a well-studied and widely used agricultural management practice for reducing nonpoint-source pollution. A wealth of literature provides experimental data on their mitigation efficacy. This paper aggregated many of these results and performed a meta-analysis to quantify the relationships between pollutant removal efficacy and buffer width, buffer slope, soil type, and vegetation type. Theoretical models for removal efficacy (Y) vs. buffer width (w) were derived and tested against data from the surveyed literature using statistical analyses. A model of the form Y = K x (1-e(-bxw)), (0 < K < or = 100) successfully captured the relationship between buffer width and pollutant removal, where K reflects the maximum removal efficacy of the buffer and b reflects its probability to remove any single particle of pollutant in a unit distance. Buffer width alone explains 37, 60, 44, and 35% of the total variance in removal efficacy for sediment, pesticides, N, and P, respectively. Buffer slope was linearly associated with sediment removal efficacy either positively (when slope < or = 10%) or negatively (when slope > 10%). Buffers composed of trees have higher N and P removal efficacy than buffers composed of grasses or mixtures of grasses and trees. Soil drainage type did not show a significant effect on pollutant removal efficacy. Based on our analysis, a 30-m buffer under favorable slope conditions (approximately 10%) removes more than 85% of all the studied pollutants. These models predicting optimal buffer width/slope can be instrumental in the design, implementation, and modeling of vegetated buffers for treating agricultural runoff.

AVGWLF‐Based Estimation of Nonpoint Source Nitrogen Loads Generated Within Long Island Sound Subwatersheds1

Abstract: The Generalized Watershed Loading Functions (GWLF) model and its ArcView interface (AVGWLF) were used to estimate and examine the components of the total nitrogen (TN) nonpoint source (NPS) load generated within New York and Connecticut (CT) watersheds surrounding Long Island Sound (LIS, the Sound). The majority of data used as model inputs were generally available from online sources, and the work involved an overall calibration to streamflow and TN data in accordance with generic guidelines recommended in the GWLF manual. The GWLF model performance for three calibration and two validation watersheds in CT was compared with results of a detailed model, Hydrological Simulation Program in Fortran, developed in a previous study. The results of the application illustrate the usefulness of the relatively simpler, less parameter‐intensive GWLF model in performing exploratory loading analysis in preparation for adaptive nutrient management in the LIS watersheds. The presented methodology is valuable for identification of priority watersheds for NPS pollution reduction and also for planning‐level evaluation of best management practices to achieve the desired reductions. It is estimated that ground‐water base flow may be the largest pathway for NPS TN to the Sound, contributing about 54% of the total NPS TN load, a finding with significant implications for LIS total maximum daily load reduction scenarios. In addition to ground water, septic systems are estimated to contribute about 17% of the total load, with the remaining TN load being mostly runoff from urban (17%), agricultural (5%), and low impact (e.g., forest) areas (6%).