平原感潮河网地区农业非点源污染产污规律

平原感潮河网地区非点源污染严重,同时由于本身具有的交叉污染等特性,造成了整个平原河网存在严重的环境污染和环境安全问题。文章在南通平原河网地区选择圩区作为典型区,以野外观测和室内分析相结合的方法开展野外原位试验,研究平原河网典型圩区各形态污染物随降雨径流的迁移特征,建立了稻季农田营养盐的迁移通量与径流通量、施肥量及降雨距施肥时间间隔三者之间的定量化关系。     

平原感潮河网地区非点源污染监测方法

平原感潮河网地区非点源污染严重以及交叉污染等特性，造成了严重的环境污染和环境安全问题。由于非点源污染监测资料不完善，相关研究的深度、广度以及监测管理存在不足，确定非点源污染大小、少资料区域污染定量化预测等问题都是亟待解决的难点。以南通平原感潮河网地区为例，对非点源污染中的不确定性及监测方法进行探讨，提出分别针对平原河网圩区和平原河网非圩区的非点源污染监测方法。     

长江口南槽水域营养盐分布特征

通过对长江口南槽水域营养盐时空变化的研究表明,南槽水域营养盐主要以硝酸盐为主,分布比较稳定;垂向分布特征明显,其中NH3N和NO-3N由表层到底层呈下降趋势;无机氮盐在小潮时含量较高,并且受涨落潮影响较小,总磷大潮时含量较高,受涨落潮影响较大;一个潮周期内营养盐的波动范围较小;营养盐的含量与水样中含沙量以及盐度的相关系数较低。     

鄱阳湖浮游藻类群落特征及与环境因子典范对应分析

通过2018—2019年夏冬季在鄱阳湖布设17个采样点,采样检测浮游藻类和水质参数,并采用典范对应分析法研究该湖浮游藻类群落结构特征及其与环境因子的相互关系。结果表明,两次调查共检测出浮游藻类7门31科58属,浮游藻类丰度范围为3.5×105 L-1～1.15×107 L-1,主要由绿藻门、硅藻门和蓝藻门组成,绿藻门为夏、冬季主要优势种群。典范对应分析结果显示,鄱阳湖冬季湖区水环境空间差异较大,而夏季差异较小;夏季氮磷营养盐和DO是影响浮游藻类群落时空分布的主要环境因子,冬季氮磷营养盐、BOD5和IMn是影响浮游藻类群落时空分布的主要环境因子。     

鄱阳湖平原区农村门塘形态特征及底泥营养状况分析

通过在鄱阳湖平原选取典型农村门塘,对其形状、进出口布置、水下地形、水深、淤塞、水质和底泥营养盐含量等指标进行调查测定分析.结果表明,鄱阳湖平原农村门塘多呈长条形;进水口设置随意,多且分散;淤塞较为严重,淤积物主要以外源输入为主;水体总氮和总磷一定程度超标,污染程度总氮总体表现为冬季＞秋季＞夏季＞春季,总磷总体表现为夏季＞春季＞秋季＞冬季;底泥营养盐和有机质含量相对较高,呈现一定的污染状态;底泥中有机质、有机碳和总氮的同源性较高,主要以内源污染物为主;底泥中磷以陆源输入为主.     

红枫湖水体中碳的时空分布特征分析

基于2013年8月、10月、11月及2014年3月在红枫湖5个表层水样采集点、3个分层水样采集点测定的总碳、无机碳、总有机碳及二氧化碳数据,结合当时的气象数据对碳的时空分布特征讨论分析。结果表明,虽然调查期间同时间相同水层各个水样采集点的上述4个指标差异并不明显,但同一时间不同分层水体及各水样采集点不同季节在碳分布上存在一定差异。温度越高,光照越长,生物活性越强,湖体碳被生物利用的比例越大,总碳、无机碳、总有机碳含量就越低,较强的生物活性也伴随更多的二氧化碳产生。上、下层水体因光与温度差异所导致的碳分布差异会因季节性翻湖而消失。     

太湖流域景观生态风险评估

在GIS和RS技术支持下,以遥感数据和土地利用数据为基础,以行政区划为评价单元,构建景观生态风险评价模型,定量评价了研究区内景观生态风险的时空动态变化特征。结果表明,较低风险区主要分布于以苕溪为主的山地丘陵区,中等风险区主要分布于农业发达的平原区,较高风险区及高风险区主要集中于沿湖经济发达区。     

特殊风场条件对太湖蓝藻水华迁移的影响研究

在高温、微风气象条件下,适宜蓝藻水华形成。在特殊非均一风场的驱动下,太湖蓝藻水华迁移过程与被均匀风场驱动有所不同。选取太湖典型风向进行分析,并采用三维水动力水质模型对表面非均一风场条件下的风生流流场及水质进行模拟,结果表明,在特殊非均一风场的驱动下,当太湖蓝藻浓度较高时,容易在西部湖区特别在竺山湖、梅梁湾湾内、岸边及湾口聚集,形成水华暴发,这有助于研究太湖污染物及蓝藻水华的输移及空间分布和机理。     

高架复合道路交通噪声时空分布规律研究

通过对杭州市典型高架复合道路交通噪声监测，研究高架复合道路交通噪声的时空分布规律。结果表明，噪声与车流量、车辆类型及车速密切相关；噪声随着与高架路距离的增大，地面各测点的噪声值呈递减趋势；高架复合道路平直段与下坡路段的噪声在临街建筑竖直立面的分布规律基本一致，但在不同高度的影响程度上存在一定差异。     

基于MODIS的西藏典型湖泊叶绿素a浓度反演

叶绿素a浓度是反映湖泊富营养化状态的一个重要参数。以MODIS L1B数据为基础，结合叶绿素a浓度实测数据，基于经验分析法实现了西藏典型湖泊叶绿素a浓度反演研究，并探索了西藏典型湖泊2019年春、夏、秋季叶绿素a浓度的时空变化特征。首先，利用叶绿素a浓度实测数据和MODIS L1B影像不同波段的反射率值进行组合试验，选择最佳波段组合建立模型；其次，分别选用2015年、2017年叶绿素a浓度实测值和反演值对模型进行对比验证；最后，利用叶绿素a浓度反演模型对西藏典型湖泊2019年春、夏、秋季叶绿素a浓度的时空变化特征进行分析。结果表明：在空间尺度上，西藏典型湖泊叶绿素a浓度整体上呈现出周围高、中部低的分布特征，且湖岸水体叶绿素a浓度变化较大；在季节尺度上，不同湖泊叶绿素a浓度的季节变化存在较大差异，格仁错和色林错的季节变化幅度较大，纳木错、塔若错和羊卓雍错的季节变化幅度较小。     

Estimation of Land Use Specific Runoff and Pollutant Concentration for Tapi River Basin in India

Non-point source (NPS) pollution is the result of various land use practices such as agriculture, sites of construction and waste disposal, urban development and so on. The control of NPS pollution is possible by regular monitoring and assessment on watershed basis to educate people for implementing well-known structural and non-structural measures. Recent trend is to use GIS based modelling tool for assessment of rainfall-runoff and non-point loading. The approach requires generation and analysis of basin wide data on various features of land and estimates of Event Mean Concentrations (EMCs) of pollutants in the runoff. In the present paper, basin wide data in different districts of Tapi basin has been analysed for land use distribution; fertilizer application; low, medium and high-density habitation; and annual rainfall. Coefficients of runoff have been estimated considering pervious and impervious area for different land use types, and compared with the reported values for Indian conditions. The estimated mean annual runoff flow indicated that two districts Jalgaon and Dhule contribute maximum runoff to the Tapi River. Estimates of EMCs for BOD and nutrients (N and P) in the runoff from various districts are useful in GIS-based modelling study for NPS pollution assessment.     

Modeling Runoff Response to Land Cover and Rainfall Spatial Variability in Semi-Arid Watersheds

Hydrologic response is an integrated indicator of watershed condition, and significant changes in land cover may affect the overall health and function of a watershed. This paper describes a procedure for evaluating the effects of land cover change and rainfall spatial variability on watershed response. Two hydrologic models were applied on a small semi-arid watershed; one model is event-based with a one-minute time step (KINEROS), and the second is a continuous model with a daily time step (SWAT). The inputs to the models were derived from Geographic Information System (GIS) theme layers of USGS digital elevation models, the State Soil Geographic Database (STATSGO) and the Landsat-based North American Landscape Characterization classification (NALC) in conjunction with available literature and look up tables. Rainfall data from a network of 10 raingauges and historical stream flow data were used to calibrate runoff depth using the continuous hydrologic model from 1966 to 1974. No calibration was carried out for the event-based model, in which six storms from the same period were used in the calculation of runoff depth and peak runoff. The assumption on which much of this study is based is that land cover change and rainfall spatial variability affect the rainfall-runoff relationships on the watershed. To validate this assumption, simulations were carried out wherein the entire watershed was transformed from the 1972 NALC land cover, which consisted of a mixture of desertscrub and grassland, to a single uniform land cover type such as riparian, forest, oak woodland, mesquite woodland, desertscrub, grassland, urban, agriculture, and barren. This study demonstrates the feasibility of using widely available data sets for parameterizing hydrologic simulation models. The simulation results show that both models were able to characterize the runoff response of the watershed due to changes of land cover.     

Linking phosphorus export and hydrologic modeling: a case study in Central Italy

Soil erosion is an open topic, not only because soil fertility is lost, but also because nutrients are spilled into water bodies, thereby causing pollution. Research carried out in this field has amply described this process, but the interaction between these factors is complex and experimental research is needed to understand the production of loads of nutrients for different land uses. This paper describes a long-term monitoring case study using high-resolution rainfall data and runoff samples, carried out in the Lake Vico basin (Central Italy) to determine the phosphorus (P) export during erosive rainfall events. State of the art GIS-based basin characterization and advanced rainfall-runoff models are employed in order to describe the relationship between nutrient export and rainfall or runoff time distribution. Results show that the phosphorus export is strongly related to such time distributions, and less to the cumulative amount of rainfall or runoff.     

Denitrification potential of riparian soils in relation to multiscale spatial environmental factors: a case study of a typical watershed,China

The objective of this study was to test the hypothesis that environmental regulators of riparian zone soil denitrification potential differ according to spatial scale within a watershed; consequently, a second objective was to provide spatial strategies for conserving and restoring the purification function of runoff in riparian ecosystems. The results show that soil denitrification in riparian zones was more heterogeneous at the profile scale than at the cross-section and landscape scales. At the profile scale, biogeochemical factors (including soil total organic carbon, total nitrogen, and nitrate–nitrogen) were the major direct regulators of the spatial distribution of soil denitrification enzyme activity (DEA). At the cross-section scale, factors included distance from river bank and vegetation density, while landscape-scale factors, including topographic index, elevation, and land use types, indirectly regulated the spatial distribution of DEA. At the profile scale, soil DEA was greatest in the upper soil layers. At the cross-section scale, maximum soil DEA occurred in the mid-part of the riparian zone. At the landscape scale, soil DEA showed an increasing trend towards downstream sites, except for those in urbanized areas.     

Derivation of unit and flood hydrographs using a gis

A geographic information system (GIS) supporting a flood hydrograph prediction software package is described. The hydrograph prediction method is based on the convolution of excess rainfall with a synthetic unit hydrograph, derived by the Soil Conservation Service runoff curve number and a regional dimensionless unit hydrograph method, respectively. The GIS uses a raster method to store the following data: land use and land cover, soil type, rainfall intensity-frequency-duration statistics, runoff curve numbers (CN), regional dimensionless unit hydrograph, and regional lag-time relationship. The GIS has also the capability of computing a number of watershed and hydrologic parameters required for predictions, such as a watershed average rainfall and CN value, area, centroid, stream length etc. Most of the data for such computations are input from a digitizer. Substantial time and cost savings are possible once the data base has been created. Application of the system is illustrated by an example predicting flood frequency curves for selected watersheds in Alberta's Rocky Mountain foothills, Canada.     

Nonpoint Source Pollution Assessment of Wujiang RiverWatershed in Guizhou Province,SW China

The amount of pollution from nonpoint sources flowing in the streams of the Wujiang River watershed in Guizhou Province, SW China, is estimated by a geographic information system (GIS)-based method using rainfall, surface runoff and land use data. A grid of cells of 100 m in size is laid over the landscape. For each cell, mean annual surface runoff is estimated from rainfall and percent land use, and expected pollutant concentration is estimated from land use. The product of surface runoff and concentration gives expected pollutant loading from that cell. These loadings are accumulated going downstream to give the expected annual pollutant loadings in streams and rivers. By dividing these accumulated loadings by the similarly accumulated mean annual surface runoff, the expected pollutant concentration from nonpoint sources is determined for each location in a stream or river. Observed pollutant concentrations in the watershed are averaged at each sample point and compared to the expected concentrations at the same locations determined from the grid cell model. In general, annual nonpoint source nutrient loadings in the Wujiang River watershed are seen to be predominantly from the agricultural and meadow areas. The total annual loadings through the outlet of the watershed are 40,309 and 2,607 tons for total nitrogen (TN) and total phosphorus (TP), respectively.     

Effects of land cover changes induced by large physical disturbances on hydrological responses in Central Taiwan

This study analyzes the significant impacts of typhoons and earthquakes on land cover change and hydrological response. The occurrence of landslides following typhoons and earthquakes is a major indicator of natural disturbance. The hydrological response of the Chenyulan watershed to land use change was assessed from 1996 to 2005. Land use changes revealed by seven remote images corresponded to typhoons and a catastrophic earthquake in central Taiwan. Hydrological response is discussed as the change in quantities and statistical distributions of hydrological components. The land cover change results indicate that the proportion of landslide relative to total area increased to 6.1% after the Chi-Chi earthquake, representing the largest increase during the study period. The study watershed is dominated by forest land cover. Comparisons of hydrological components reveal that the disturbance significantly affects base flow and direct runoff. The hydrological modeling results demonstrate that the change in forest area correlates with the variation of base flow and direct runoff. Base flow and direct runoff are sensitive to land use in discussions of distinction. The proposed approach quantifies the effect of typhoons and earthquakes on land cover changes.     

A Spatially Explicit Model for Estimating Annual Average Loads of Nonpoint Source Nutrient at the Watershed Scale

The overloaded nonpoint source (NPS) nutrients in upper streams always result in the nutrient enrichment at lakes and estuaries downstream. As NPS pollution has become a serious environmental concern in watershed management, the information about nutrient output distribution across a watershed has been critical in the designing of regional development policies. But existing watershed evaluation models often encounter difficulties in application because of their complicated structures and strict requirements for the input data. In this paper, a spatially explicit and process-based model, Integrated Grid’s Exporting and Delivery model, was introduced to estimate annual in-stream nutrient levels. Each grid cell in this model was regarded as having potentials of both exporting new nutrients and trapping nutrients passing by. The combined nutrient dynamics of a grid is mainly determined by the grid’s features in land use/land cover, soil drainage, and geomorphology. This simple-concept model was tested at some basins in north Georgia in the USA. Stations in one basin were used to calibrate the model. Then an external validation was employed by applying the calibrated model to stations in the other neighbor basins. Model evaluation statistics implied the model’s validity and good performance in estimating the annual NPS nutrients’ fluxes at the watershed scale. This study also provides a promising prospect that in-stream annual nutrient loads can be accurately estimated from a few public available datasets.