Hydrochemistry and dissolved nutrient flux of two small catchment rivers, south-western India

This paper deals with the water chemistry and dissolved nutrient flux of two small mountainous and heavily dammed rivers—Periyar and Chalakudy—of Kerala on the south-west coast of India. The lower reaches of these rivers are affected by sea-water ingression from the Arabian Sea during the non-monsoon season. Human interference through agriculture, urbanization, and industrialization in the lower and middle stretches of the river basins induces marked concentration variations in the hydro-chemical parameters. Except for N & P, all other chemical constituents exhibit high values during the non-monsoon season. Industrial contaminants in specific locations of the Periyar river reduce the pH to lower levels. Nutrients in the two rivers reveal marked seasonal and regional concentration variations. During the monsoon season, dissolved inorganic nitrogen (DIN) predominates over dissolved organic nitrogen (DON), but the reverse trend is observed during the non-monsoon season. The Periyar river shows higher average concentrations of DIN (monsoon 801 μg l^-1 and non-monsoon 292 μg l^-1) than Chalakudy river (monsoon 478 μg l^-1 and non-monsoon 130 μg l^-1). Dissolved inorganic phosphorus (DIP) has lower average values in the monsoon season (Periyar river, 38 μg l^-1; Chalakudy river, 42 μg l^-1) than dissolved organic phosphorus (DOP) values (Periyar river, 107 μg l^-1; Chalakudy, 62 μg l^-1). The rivers show a marked difference in nutrient flux due to its difference in water discharge/basin characteristics and point/non-point sources of contaminants. The flux rates of DIN, DIP, and DOP during the monsoon are higher than during the non-monsoon season, while those of dissolved silicon (DSi), dissolved Fe (DFe), and DON are lower. On average, the Periyar river discharges 4953 t y^-1 of DIN and 1626 t y^-1 of DON to the coastal waters, and the corres-ponding values of the Chalakudy river are 772 t y^-1 and 596 t y^-1. The Periyar and Chalakudy rivers discharge 245 t y^-1 and 70.8 t y^-1 of DIP, respectively. The total flux of DOP is considerably higher (Periyar river 703 t y^-1 and Chalakudy river 101 t y^-1). The discharge of DSi into the Periyar river (40 193 t y^-1) is nearly five times higher than that in the Chalakudy river (8275 t y^-1). The discharges of DFe through the Periyar and Chalakudy rivers are 257 t y^-1 and 36.7 t y^-1, respectively. To sum up, this study addresses the water quality and nutrient flux of two tropical rivers and discusses the impact of urbanization and industrialization on river-water quality.     

左右岸跨界水污染治理演化博弈与政策路径研究

基于流域跨界水污染问题多关注于上下游矛盾而忽视左右岸的"公地悲剧",本研究构建左、右岸地区和流域政府三方演化博弈模型,探索奖惩、补偿及复合机制下的主体决策和演化格局差异,结合仿真实验给出推动左右岸协同治理政策路径.结果显示,实现左右岸地区达标排放的关键在于显化达标排放收益与超标排放损失.流域政府倾向于选择奖惩或补偿的单一机制,奖惩机制在不同政策组合中显示出必要性,补偿机制具有加快达标决策、减缓超标决策的收敛速度的积极意义.政策路径是首先采取"阶梯惩罚政策"并增加严重超标惩罚额;继而依次增加奖励和惩罚额促成"奖惩机制",或依次增加奖励额和左右岸之间的补偿额促成"补偿机制",同时给出了上述额度的量化表达式.     

华北南部冬季大气亚微米颗粒物数浓度变化

2018年1月华北平原经历了一段持续时间久、影响范围广和颗粒物浓度高的重污染时期.本研究通过SMPS+E扫描电迁移率粒径谱仪,选取华北平原南部某郊区点位,对此次重污染期间颗粒物数浓度粒径分布演化进行连续观测研究.结果表明,观测期间环境空气质量尤其是PM_2.5平均浓度为141.32 μg/m³.大气亚微米颗粒物数浓度主要集中在核模态和爱根核模态的超细粒径段（78.9%）,呈递减型单峰分布,颗粒物平均数浓度为83174cm^-3.重污染天时,核模态颗粒物数浓度明显增高,对应低风速（1.5±0.4）m/s、高相对湿度（90.8±4.5）%和低O₃浓度（15.8±8.3）μg/m³.48h后向轨迹显示,观测点位气溶胶主要受湖北省、陕西省和山西省临近省份的传输影响.潜在源贡献因子法和浓度权重轨迹表明,气溶胶潜在源区主要为本地源和观测点位以北的区域.     

Reach‐Scale Comparison of Habitat and Mollusk Assemblages for Select Sites in the Clinch River with Regional Context

Several hypotheses, including habitat degradation and variation in fluvial geomorphology, have been posed to explain extreme spatial and temporal variation in Clinch River mollusk assemblages. We examined associations between mollusk assemblage metrics (richness, abundance, recruitment) and physical habitat (geomorphology, streambed composition, fish habitat, and riparian condition) at 10 sites selected to represent the range of current assemblage condition in the Clinch River. We compared similar geomorphological units among reaches, employing semi‐quantitative and quantitative protocols to characterize mollusk assemblages and a mix of visual assessments and empirical measurements to characterize physical habitat. We found little to no evidence that current assemblage condition was associated with 54 analyzed habitat metrics. When compared to other sites in the Upper Tennessee River Basin (UTRB) that once supported or currently support mollusk assemblages, Clinch River sites were more similar to each other, representing a narrower range of conditions than observed across the larger geographic extent of the UTRB. A post‐hoc analysis suggested stream size and average boundary shear stress at bankfull stage may have historically limited species richness in the UTRB (p < 0.001). Associations between mollusk assemblages and physical habitat in the UTRB and Clinch River currently appear obscured by other factors limiting richness, abundance, and recruitment.     

Channel Roughness in North Carolina Mountain Streams

Channel roughness, often described by Manning's n, is used to represent the amount of resistance that flow encounters, and has direct implications on velocity and discharge. Ideally, n is calculated from a long‐term record of channel discharge and hydraulic geometry. In the absence of these data, a combination of photo references and a validated qualitative method is preferable to simply choosing n arbitrarily or from a table. The purpose of this study was to use United States Geological Survey (USGS) streamflow data to calculate roughness coefficients for streams in the mountains of North Carolina. Five USGS gage stations were selected for this study, representing drainage areas between 71.5 and 337 km². Photo references of the study sites are presented. Measured discharges were combined with hydraulic geometry at a cross‐section to calculate roughness coefficients for flows of interest. At bankfull flow, n ranged between 0.039 and 0.064 for the five study sites. Roughness coefficients were not constant for all flows in a channel, and fluctuated over a large range. At all sites, roughness was highest during low‐flow conditions, then quickly decreased as flow increased, up to the bankfull elevation.     

沈阳市中心城区和市郊区能耗碳排放格局差异

以沈阳市和平区和沈北新区2个不同类型的城区创建国家可持续发展实验区为契机,对比分析了中心城区和市郊区能耗碳排放格局的差异,提出了针对不同区域的特点将碳减排纳入到实验区的可持续发展建设中. 结果表明:中心城区和平区的能耗碳排放格局以原煤、电力和汽油的消耗为主,其中2006─2008年该区燃煤比重逐年下降,汽油比重逐年上升,电力排放总量虽缓慢增加但排放比重却有所下降;而对于郊区沈北新区而言,能耗碳排放格局则以燃煤和电力为主,其中燃煤比重逐年下降,而电力排放逐年上升. 情景预测结果表明: 到2015年和2020年,和平区CO₂排放强度将分别达到1.16和1.11 t/(104元),比2006年分别下降23.2%和26.5%,不能实现2020年单位GDP CO₂排放量比2005年下降40%～45%的减排目标;沈北新区CO₂排放强度下降趋势明显,2015年和2020年将分别达到2.48和2.07 t/(104元),比2006年分别下降63.1%和69.3%,可实现40%～45%的CO₂减排目标. 讨论了中心城区和郊区碳排放格局的差异,并分别给出了适合的碳减排建议.      

南四湖及入出湖河流水环境质量变化趋势分析

南四湖作为南水北调东线工程重要的输水通道和调蓄湖泊,其水质状况一直受到人们的广泛关注. 根据南四湖流域主要入出湖河流14个监控断面及湖内5个监测站点的数据,从年际、年内、不同时间段和不同监测站点等进行了南四湖及河流水质变化趋势的综合分析. 结果表明,2007与2000年相比,南四湖入出湖河流监控断面的ρ（COD_Cr）总体下降率达到84.2%,ρ（NH₃-N）总体下降率达到79.7%. 南四湖及河流水质总体上出现了大幅度的改善,但距离稳定达到调水水质Ⅲ类标准的要求还有较大差距. 受水文情势、底泥释放和污染源以及各项污染控制措施等因素的影响,南四湖及入出湖河流监控断面水质改善存在一定的波动现象,水体富营养化形势严峻. 提出了科学合理地计算与分配南四湖养殖承载力和流域水环境承载力,重视非点源的控制与治理,大力推进“退耕还湿、退渔还湖”策略,是当务之急.      

Evaluation of aquatic rehabilitation technologies for polluted urban rivers and the case study of the Foshan Channel

An index system for evaluation of technologies for urban river rehabilitation was proposed and discussed. The index system includes indicators of cost, resources, environmental improvement, and social effects. The calculation method for an objective value of each index based on its attributes and weights was presented. The Foshan Channel, which is a seriously polluted, black and malodorous urban river in Foshan City, China, was selected as a case study. The values of the attributes and the weights of the indices for the Foshan Channel were determined. The technologies for the rehabilitation of the Foshan Channel were evaluated based on this index system. Finally, a rehabilitation scheme for the Foshan Channel was proposed.     

Recovery of Endemic Dragonflies after Removal of Invasive Alien Trees

Abstract:  Because dragonflies are very sensitive to alien trees , we assessed their response to large-scale restoration of riparian corridors. We compared three types of disturbance regime—alien invaded , cleared of alien vegetation , and natural vegetation (control)—and recorded data on 22 environmental variables. The most significant variables in determining dragonfly assemblages were percentage of bank cover and tree canopy cover , which indicates the importance of vegetation architecture for these dragonflies. This finding suggests that it is important to restore appropriate marginal vegetation and sunlight conditions. Recovery of dragonfly assemblages after the clearing of alien trees was substantial. Species richness and abundance at restored sites matched those at control sites. Dragonfly assemblage patterns reflected vegetation succession. Thus , initially eurytopic , widespread species were the main beneficiaries of the removal of alien trees , and stenotopic , endemic species appeared after indigenous vegetation recovered over time. Important indicator species were the two national endemics ( Allocnemis leucosticta and Pseudagrion furcigerum ) , which , along with vegetation type , can be used to monitor return of overall integrity of riparian ecology and to make management decisions. Endemic species as a whole responded positively to restoration , which suggests that indigenous vegetation recovery has major benefits for irreplaceable and widespread generalist species .     

国际河流管理合作模式的分类及演进规律探讨

论文对国际河流管理合作模式的概念、分类及演进规律进行了探讨。在从合作主体、目标、途径、制度等方面对合作模式进行单维度分类的基础上,借鉴霍尔三维结构图系统分析方法,构建了合作模式三维度分类模型,较全面、准确地概括了当前国际河流管理合作实践的模式类型。最后,综合世界各种典型国际河流管理合作模式的形成和发展过程,从模式要素的发展演变及模式演进的动力机制两个方面入手,详细阐述了国际河流管理合作模式的演进规律。