中国江河氧化亚氮的排放及其影响因素

氧化亚氮（N₂O）是一种在大气中存留时间很长的强效温室气体,并被认为是21世纪破坏臭氧层的重要物质之一,气候预测需要对自然与人为排放的包括N₂O在内的温室气体进行全面准确地估算.内陆水体是N₂O的重要排放源,由于人为氮输入的增加,江河N₂O的排放量可能逐年升高.本研究总结了江河N₂O排放速率的研究方法,重点汇总了中国各气候带十大流域江河N₂O的溶存浓度和水气界面交换通量,并与世界其他河流进行比较.结果表明我国江河溶存N₂O浓度为0.3~1591 nmol·L^-1,N₂O释放通量为-12.2~2262.1 μmol·m^-2·d^-1,总体与世界其他江河的范围值具有可比性.在此基础上,进一步分析了江河N₂O的产生和释放机理,探讨了水中溶解性无机氮、溶解氧、有机碳以及水文、地形地貌与气象条件等对江河N₂O产生和释放的影响,并讨论了变化环境下江河N₂O的排放特征.     

川西高海拔河流中溶解性有机质(DOM)紫外-可见光吸收光谱特征

溶解性有机质(DOM)对全球碳循环及气候变化具有重要意义.本文选取川西北4条高海拔河流,即杂谷脑河、抚边河及岷江(高山峡谷河流)与白河(高原河流),对其天然水体中有色溶解性有机质(CDOM)的紫外-可见光吸收光谱特征进行了研究与比较.结果表明,川西高海拔河流DOC变化范围为1.55~5.66 mg·L~(-1),CDOM(以a(355)表征)变化范围为0.96~6.31 m-1,荧光溶解性有机质(FDOM)(以lg Fn(355)表征)变化保持在2.08~2.83之间.与高山峡谷区河流比较,高原河流芳香性、疏水性特征常数SUVA254、SUVA260较高,吸光度之比E2/E3、光谱斜率S275~295及光谱斜率之比SR较低,揭示了高原河流CDOM芳香性较强、疏水性组分丰富、分子结构较为复杂;SUVA254、SUVA260分别与SR、S275~295呈显著负相关,表明白河由于高通量陆源腐殖质输入影响了CDOM特征.川西高原4条高海拔河流中SUVA254、SUVA260存在显著相关关系,表明芳香性结构普遍存在于河流CDOM疏水组分中.川西高原天然河流水体中CDOM与DOM的浓度之间总体上无直接关联,因为不同天然水体在DOM形成过程中,陆源DOC输入组分和强度及转化机制存在差异.研究结果对于揭示高海拔区域在全球变化背景下有机碳循环的区域效应等方面具有重要意义.     

安徽中北部河流沉积物的特征与多环芳烃分布

通过对安徽省中北部6条河流沉积物样品的粒径、矿物组分和有机质含量的测试,并应用气相色谱质谱联用仪测定了样品中萘、二氢苊、苊、芴、菲、蒽、荧蒽、芘、苯并[a]蒽、、苯并[a]芘和二苯并[a,h]蒽等12种多环芳烃的含量,分析了研究区河流沉积物的特征和多环芳烃分布。研究结果表明:位于安徽省中北部的淮河南北岸支流沉积物粒径和矿物组分具有不同特征;就PAHs总量来看,北岸支流平均值为313.3ng/g,南岸支流平均为112.8ng/g,差异比较明显,南岸支流沉积物中大多数多环芳烃的平均含量都低于北岸支流(蒽和菲除外,二苯并[a,h]蒽未检出);而有机质的含量,南北岸支流总体无明显差异(含量在0.55%至1.83%之间),但单条河流的分布呈沿水流方向自中上游至下游逐渐降低。     

Changes in Hydrology of the Ganges Delta of Bangladesh and Corresponding Impacts on Water Resources

The Ganges Delta in Bangladesh is an example of water‐related catastrophes in a major rural river basin where limitations in quantity, quality, and timing of available water are producing disastrous conditions. Water availability limitations are modifying the hydrologic characteristics especially when water allocation is controlled from the upstream Farakka Barrage. This study presents the changes and consequences in the hydrologic regime due to climate‐ and human‐induced stresses. Flow duration curves (FDCs), rainfall elasticity, and temperature sensitivity were used to assess the pre‐ and post‐barrage water flow patterns. Hydrologic and climate indices were computed to provide insight on hydro‐climatic variability and trend. Significant increases in temperature, evapotranspiration, hot days, heating, and cooling degree days indicate the region is heading toward a warmer climate. Moreover, increase in high‐intensity rainfall of short duration is making the region prone to extreme floods. FDCs depict a large reduction in river flows between pre‐ and post‐barrage periods, resulting in lower water storage capacity. The reduction in freshwater flow increased the extent and intensity of salinity intrusion. This freshwater scarcity is reducing livelihood options considerably and indirectly forcing population migration from the delta region. Understanding the causes and directions of hydrologic changes is essential to formulate improve water resources management in the region.     

Biological Connectivity of Seasonally Ponded Wetlands across Spatial and Temporal Scales

Many species that inhabit seasonally ponded wetlands also rely on surrounding upland habitats and nearby aquatic ecosystems for resources to support life stages and to maintain viable populations. Understanding biological connectivity among these habitats is critical to ensure that landscapes are protected at appropriate scales to conserve species and ecosystem function. Biological connectivity occurs across a range of spatial and temporal scales. For example, at annual time scales many organisms move between seasonal wetlands and adjacent terrestrial habitats as they undergo life‐stage transitions; at generational time scales, individuals may disperse among nearby wetlands; and at multigenerational scales, there can be gene flow across large portions of a species’ range. The scale of biological connectivity may also vary among species. Larger bodied or more vagile species can connect a matrix of seasonally ponded wetlands, streams, lakes, and surrounding terrestrial habitats on a seasonal or annual basis. Measuring biological connectivity at different spatial and temporal scales remains a challenge. Here we review environmental and biological factors that drive biological connectivity, discuss implications of biological connectivity for animal populations and ecosystem processes, and provide examples illustrating the range of spatial and temporal scales across which biological connectivity occurs in seasonal wetlands.     

聚类分析和标识指数法在苏州城区河道的应用

选取2013—2014年苏州市古城区河道8个监测断面的水质监测数据,应用层次聚类分析法和改进的综合水质标识指数法对苏州市古城区河道水质进行综合评价,并对各监测断面综合水质达标率进行计算。结果表明:苏州市古城区主河道水质在2013年5月份后明显好转,但小河道水质改善较小;在空间上呈现出城北河道水质较城南好,纵向河道水质比横向好的特点。根据评价结果与实际工程情况对比发现,层次聚类分析和水质标识指数法可以有效、准确地对城区河道水质进行总体评价。     

Southwestern Intermittent and Ephemeral Stream Connectivity

Ephemeral and intermittent streams are abundant in the arid and semiarid landscapes of the Western and Southwestern United States (U.S.). Connectivity of ephemeral and intermittent streams to the relatively few perennial reaches through runoff is a major driver of the ecohydrology of the region. These streams supply water, sediment, nutrients, and biota to downstream reaches and rivers. In addition, they provide runoff to recharge alluvial and regional groundwater aquifers that support baseflow in perennial mainstem stream reaches over extended periods when little or no precipitation occurs. Episodic runoff, as well as groundwater inflow to surface water in streams support limited naturally occurring riparian communities. This paper provides an overview and comprehensive examination of factors affecting the hydrologic, chemical, and ecological connectivity of ephemeral and intermittent streams on perennial or intermittent rivers in the arid and semiarid Southwestern U.S. Connectivity as influenced and moderated through the physical landscape, climate, and human impacts to downstream waters or rivers is presented first at the broader Southwestern scale, and secondly drawing on a specific and more detailed example of the San Pedro Basin due to its history of extensive observations and research in the basin. A wide array of evidence clearly illustrates hydrologic, chemical, and ecological connectivity of ephemeral and intermittent streams throughout stream networks.     

Integrating channel design and assessment methods based on sediment transport capacity in gravel bed streams

Natural channel design (NCD) and analytical channel design (ACD) are two competing approaches to stable channel design that share fundamental similarities in accounting for sediment transport processes with designs based on hybrid fluvial geomorphology and hydraulic engineering methods. In this paper, we highlight the linkage between ACD's capacity/supply ratio (CSR) and NCD's sediment capacity models (FLOWSED/POWERSED), illustrating how ACD and NCD have reached a point of convergent evolution within the stream restoration toolbox. We modified an existing CSR analytical spreadsheet tool which enabled us to predict relative channel stability using both conventional bed load transport equations and regional sediment regression curves. The stable channel design solutions based on measured data most closely matched the Parker (ACD) and/or Pagosa good/fair (NCD) relationships, which also showed the greatest CSR sensitivity in response to channel alterations. We found that CSR differences among the transport relationships became more extreme the further the design width deviated from the supply reach, suggesting that a stable upstream supply reach may serve as the best design analog. With this paper, we take a step toward resolving lingering controversy in the field of stream restoration, advancing the science and practice by reconciling key differences between ACD and NCD in the context of reach scale morphodynamics.     

苏州古城区域河道碳氮磷类污染物的分布特征

苏州是水质型缺水城市,节水、减排、控源和截污等工程实施后,水质问题依然严峻.为了解苏州古城区域河道中碳氮磷类污染物的总量及分布特征,提出河道疏浚决策依据,于2019年春季在苏州古城区域采集了20个代表性断面的河道底泥和水体样品,测定了河道底泥的深度,分析了河道底泥和水体样品中碳氮磷类污染指标的含量,评价了河道底泥和水体的污染程度,并预测了换水、引水、降雨和疏浚情境下水质的变化.结果表明,苏州古城区域河道底泥深度在22~1025 mm之间（均值为266 mm）,底泥总质量约为5.2×10⁵ t.底泥中总有机碳、总氮、氨氮、总磷和有效磷平均含量分别为3.4%、2074 mg·kg^-1、140.2 mg·kg^-1、1765 mg·kg^-1和57.2 mg·kg^-1,属中度污染,总磷含量超标点超过90%,环城河污染程度最高,建议优先疏浚.水体中总有机碳、生化需氧量、化学需氧量、总氮、氨氮、凯氏氮、总磷和磷酸盐平均浓度分别为7.8、0.6、13.1、2.5、0.643、1.3、0.18和0.09 mg·L^-1,属重度污染,为劣V类地表水,总氮浓度严重超标.基于沿程碳氮磷类污染物总量的分布情况,苏州古城区域河道疏浚推荐顺序为环城河、古城北部河道、干将河和古城南部河道.降雨情景下,初期径流污染物浓度高,将导致河道水质急剧下降;换水和引水情境下水中总氮总量均减少0.2 t,完全疏浚后水中总氮总量分别进一步减少4.58 t和2.19 t.底泥磷以外源输入为主,可受纳部分水体中的磷,故疏浚后,水体中总磷总量可能增加.     

环渤海河流COD入海通量及其对渤海海域COD总量的贡献

于2013年8月~2014年10月,分季节对环渤海36条入海河流进行了4次调查采样,核算其COD入海通量,并评估其对渤海水质的影响.结果表明,大部分河流都受到了严重污染(COD为地表IV类),但污染最重的河流并不是COD入海通量最大的河流,COD的最大值和COD入海通量的最大值不具有一致性;环渤海河流排入渤海的COD_Cr的年入海通量最大(606万t),其次是酸性COD_Mn的入海通量(62万t),碱性COD_Mn最小,为53万t;环渤海河流在丰水期COD的入海通量约占全年的68%,其次是平水期(28%),枯水期最小(4%);整个渤海海域的碱性COD_Mn总量为239万t,其中环渤海河流输入约占25%.