闽江感潮河段夏秋季涨落潮河水稳定同位素（N/D/O-18）组成特征解析

流域氮污染的稳定同位素表征和溯源对于保障流域污染防控和用水安全具有重要意义,本文通过对感潮河段夏、秋季涨落潮主要断面硝态氮（NO₃^-）及稳定同位素(δ¹⁵N-NO₃^-、δ¹⁸O-NO₃^-、δD-H₂O和δ¹⁸O-H₂O)组成特征测定及沿线小流域的氮污染入河量测算,探讨了陆域氮排放和水体交换对感潮河段稳定同位素的影响.研究表明：（1）落潮、涨潮期NO₃^-均为“秋季>夏季”,δ¹⁵N-NO₃^-夏、秋两季组成特征基本相近.落潮期δ¹⁸O-NO₃^-为“夏季>秋季”,涨潮期则相反.同季节的NO₃^-及其同位素总体呈“涨潮期>落...     

Seasonal and Flood‐Induced Variations in Groundwater–Surface Water Exchange in a Northern Coldwater Fishery

Groundwater upwelling is important to coldwater fisheries survival. This study used stable isotopes to identify upwelling zones within a watershed, then combined isotope analyses with reach‐scale monitoring to measure surface water–groundwater exchange over time. Research focused on Amity Creek, Minnesota, a basin that exemplifies conditions limiting coldwater species survival along Lake Superior's North Shore where shallow bedrock limits groundwater capacity, lowering baseflows and increasing temperatures. Groundwater‐fed reaches were identified through synoptic isotope sampling, with results highlighting the importance of isolated shallow surficial aquifers (glacially derived sands and gravels) for providing cold baseflow waters. In an alluvial reach, monitoring well results show groundwater was stored in two reservoirs: one that reacts quickly to changes in stream levels, and one that remained isotopically isolated under most flow conditions, but which helps sustain summer baseflows for weeks to months. A 500‐year flood demonstrated the capacity of high‐flow events to alter surface water–groundwater connectivity. The previously isolated reservoir was exchanged or mixed during the flood pulse, while incision lowered the water table for years. The results here provide insight for streams that lack substantial groundwater inputs yet maintain coldwater species at risk in a warming climate and an approach for managers seeking to protect cold baseflow sources.     

喀斯特小流域黄壤硫同位素组成特征——对环境过程和效应的指示

用连续提取方法分析了黄壤中总硫、SO₄^2-、总还原态硫（TRS）和有机硫的硫同位素组成,探讨黄壤中硫的迁移转化过程及其环境效应.有机硫是主要的硫形态,SO₄^2-是主要的无机硫形态.TRS具有最低的δ³⁴S值,同时SO₄^2-和TRS的δ³⁴S值随剖面加深而平行地增大指示黄壤中存在SO₄^2-异化还原过程.黄壤剖面中总硫和有机硫的δ³⁴S值先增大后降低与有机硫矿化及有机硫组分的迁移和底层吸附有关.生物滞留后剩余SO₄^2-的吸附、解吸、淋溶迁移及深层吸附与累积导致剖面中SO₄^2-的δ³⁴S值先增大后明显降低.酸沉降下剖面中SO₄^2-的吸附、解吸和淋溶迁移可引起黄壤酸化.值得关注的是,酸沉降输入的SO₄^2-主要以有机硫和吸附态SO₄^2-滞留在黄壤中,则在硫的年沉降速率大幅降低后,在较长时期内,黄壤中有机硫矿化和吸附态SO₄^2-解吸可能释放大量SO₄^2-进入地表和地下水体,与之相关的土壤理化性质变化和水体化学组成改变等方面的环境效应值得关注.     

碳氮氧同位素解析典型岩溶流域地下水中硝酸盐来源与归趋

利用多同位素（C、N和O）和水化学方法解析贵州八步地下河流域水体中硝酸盐（NO₃^-）来源与转化过程,利用SIAR模型定量计算NO₃^-不同输入端的贡献比例.结果表明,研究区地下水NO₃^-污染严重,近38%的地下水样品NO₃^-超过饮用水限值.地下水的δ¹⁵N-NO₃值介于2.3‰~30.33‰,均值9.68‰,δ¹⁸O-NO₃值介于2.65‰~13.73‰,均值6.64‰,δ¹⁸O-H₂O值介于-8.83‰~-7.37‰,均值-8.18‰.同位素组成（δ¹⁵N-NO₃、δ¹⁸O-NO₃和δ¹⁸O-H₂O）指示硝化作用主导着流域内氮素循环.硝化作用产生的硝酸加速了碳酸盐岩溶解,导致地下水中δ¹³C_DIC与δ¹⁵N-NO₃存在显著负相关性（P<0.001）,说明δ¹³C_DIC与δ¹⁵N-NO₃相结合是判断岩溶水中NO₃^-转化的有效手段.地下水和地表水中NO₃^-主要来源于土壤氮、粪肥污水和铵态氮肥料,其对地下水中NO₃^-贡献率分别为36.19%、33.71%和30.1%,对地表水贡献率分别为39.15%、36.08%和24.77%.岩溶流域内污水处理应同时去除污水中的NO₃^-和NH₄⁺,农业区应科学施肥,以有效降低地下水中NO₃^-的补给通量.     

Testing the Established Hydrogeologic Model of Source Water to the Amargosa River Basin,Inyo and San Bernardino Counties,California

The current conceptual hydrogeologic model established for source water to the Amargosa River was tested in order to help inform management decisions regarding the Amargosa River's Federal designation as Wild and Scenic through an Act of Congress. The limited availability of water in this region results in the critical need for effective management in the basin to maintain its Wild and Scenic attributes inclusive of habitat for several endangered and threatened species. The use of forensic tools and integration of multiple lines of geologic, hydrogeologic, geochemical, and stable isotopic evidence suggest that the simple historical model for primary groundwater transport through this region is incorrect and that a large supply of regional baseflow does not provide the hydrogeological foundation of the Amargosa River basin. Data collected is consistent with an alternative model requiring complex source mixing and shallow alluvial groundwater that supports river flow. This conclusion also suggests Wild and Scenic conditions in this basin are more precarious than previously understood.     

Historical nitrogen content of bryophyte tissue as an indicator of increased nitrogen deposition in the Cape Metropolitan Area, South Africa

Information on changes in precipitation chemistry in the rapidly expanding Cape Metropolitan Area (CMA) of South Africa is scarce. To obtain a long-term record of N deposition we investigated changes in moss foliar N, C:N ratios and nitrogen isotope values that might reflect precipitation chemistry. Tissue from 9 species was obtained from herbarium specimens collected between 1875 and 2000 while field samples were collected in 2001/2002. There is a strong trend of increasing foliar N content in all mosses collected over the past century (1.32-1.69 %N). Differences exist between ectohydric mosses which have higher foliar N than the mixohydric group. C:N ratios declined while foliar δ¹⁵N values showed no distinct pattern. From relationships between moss tissue N and N deposition rates we estimated an increase of 6-13 kg N ha⁻¹ a⁻¹ since 1950. Enhanced N deposition rates of this magnitude could lead to biodiversity losses in native ecosystems.     

Concentrations of U,U, U,Th, Th,Th, Ra,Ra, Ra,Po, Pb and Pb in drinking water in Italy: reconciling safety standards based on measurements of gross α and β

Some important naturally occurring α- and β-radionuclides in drinking water samples collected in Italy were determined and the radiological quality evaluated. The mean activity concentrations (mBq L⁻¹) of the radionuclides in the water samples were almost in the order: 26 ± 36 (²³⁴U) > 21 ± 30 (²³⁸U) > 8.9 ± 15 (²²⁶Ra) > 4.8 ± 6.3 (²²⁸Ra) > 4.0 ± 4.1 (²¹⁰Pb) > 3.2 ± 3.7 (²¹⁰Po) > 2.7 ± 1.2 (²¹²Pb) > 1.4 ± 1.8 (²²⁴Ra) > 1.1 ± 1.3 (²³⁵U) > 0.26 ± 0.39 (²²⁸Th) > 0.0023 ± 0.0009 (²³⁰Th) > 0.0013 ± 0.0006 (²³²Th). The mean estimated dose (μSv yr⁻¹) to an adult from the water intake was in this order: 2.8 ± 3.3 (²¹⁰Po) > 2.4 ± 3.2 (²²⁸Ra) > 2.1 ± 2.1 (²¹⁰Pb) > 1.8 ± 3.1 (²²⁶Ra) > 0.94 ± 1.30 (²³⁴U) > 0.70 ± 0.98 (²³⁸U) > 0.069 ± 0.087 (²²⁴Ra) > 0.036 ± 0.044 (²³⁵U) > 0.014 ± 0.021 (²²⁸Th) > 0.012 ± 0.005 (²¹²Pb) > 0.00035 ± 0.00029 (²³⁰Th) > 0.00022 ± 0.00009 (²³²Th). It is obvious that ²¹⁰Po, ²²⁸Ra, ²¹⁰Pb and ²²⁶Ra are the most important dose contributors in the drinking water intake. As far as the seventeen brands of analysed drinking water were concerned, the committed effective doses were in the range of 2.81–38.5 μSv yr⁻¹, all well below the reference level of the committed effective dose (100 μSv yr⁻¹) recommended by the WHO. These data throw some light on the scale of the radiological impact on the public from some naturally occurring radionuclides in drinking water, and can also serve as a comparison for the dose contribution from artificial radionuclides released to the environment as a result of human practices. Based on the radionuclide composition in the analysed waters, comment was made on the new screening level for gross α activity in guidelines for drinking-water quality recommended by the WHO, 2004.     

西藏盐井地区盐泉同位素特征示踪研究

对西藏盐井地区盐泉、曲孜卡泉、地表水及重要地层进行了同位素测定和分析,结合区域地质构造条件、辅以水化学证据确定泉水的补径排模式。δD~δ18O规律指示出盐泉和温泉的补给类型的差异;用δ18O对泉水的补给区海拔高程进行恢复;泉水、岩样的δ13C~δ18O规律指示出盐泉流经的主要相关层位为上三叠统地层T3b~T3d;其排泄主要受到芒康-盐井复式向斜次级背斜核部的张性裂隙所控制。     

我国东北地区大气降水稳定同位素特征及其水汽来源

依据全球大气降水同位素观测网络(GNIP)中我国东北地区的月大气降水氢氧稳定同位素资料,并结合相关气象资料,分析了该地区大气降水稳定同位素时空分布特征及其影响因子,并建立了局地大气水线方程.结果表明,东北地区大气降水中δ18O值总体上较低,在时间变化上,表现为冬低夏高;从空间分布来看,由南至北加权平均δ18O值呈减小趋势;降水δ18O与温度线性关系显著,而与降水量则不存在线性关系,利用降水δ18O与温度、降水量、高程、经度和纬度等气候因子建立的多元线性回归关系可以对降水δ18O进行定量估算;采用HYSPLIT 4.9模型对GNIP观测点水汽来源进行追踪,气团聚类轨迹表明,该区全年有两条水汽路径,分别为西风带输送的大西洋、极地北冰洋冷湿水汽和太平洋暖湿水汽.     

基于氮氧同位素解析不同降雨条件下硝酸盐污染源

随着城市化的进程和人类活动强度的增加,过高的硝酸盐污染负荷对地表水水质安全构成极大威胁.当前针对地表水体的硝酸盐源解析仅强调了来源的季节性变化特征,而鲜见考虑降雨事件对区域污染源组成的影响.本文以扬州市江都区通扬运河为研究对象,利用氮氧同位素技术和基于R语言的稳定同位素模型(stable isotope analysis in R)定量评价了各类型污染源在不同降雨条件下对水体硝酸盐污染的贡献.结果表明:①通扬运河各区段污染物浓度具有很强的空间变异性.ρ(NO3-)和ρ(NH4+)具有相似的空间分布特征,表现为:中游区＞下游区＞上游区,中游区较高的城市化水平带来的人类活动加剧了氮污染的输入.②降雨增加了各河段污染物浓度的不确定性,降雨带来的冲刷和稀释效应总体上增加了水体中的ρ(NO3-)、ρ(NH4+)、ρ(Cl-)和ρ(SO42-).③在无雨和低降雨的条件下,通扬运河水体NO3-主要来源于大气沉降(贡献率为27％～47％)和土壤有机氮(贡献率为21％～29％);在降雨事件影响下,化肥(贡献率为16％～34％)成为了最主要的污染源.降雨造成的污染源变化具有空间差异性,下游区(农业区)化肥和土壤有机氮贡献率的增加较中上游区更加明显.④下游区存在较强的反硝化作用,且低降雨条件下更容易发生硝化和反硝化.