Seasonal variation of the double diffusion processes at the Strait of Hormuz

Profiles of salinity and temperature were measured in the strait of Hormuz (SH) during the winter of 2012, spring and summer of 2013. To investigate the double diffusion (DD) processes, Turner (TU) angle values are calculated in all the stations in the SH. Different TU angle values correspond to salt fingering (SF), diffusive convection (DC) and stable stratification. The distributions of the two forms of DD were plotted vertically along transects in the eastern, central and western part of the SH, and corresponding DD processes were described. The results show that both SF and DC occurred in most part of the study area. Two different water masses (the Indian Ocean surface water and the Persian Gulf water) were evident at the SH, and SF and DC were evident at the interface of two water masses. Due to evaporation, SF occurred in the surface layer of most Stations throughout the year. In the eastern part of the SH, occurrences of DC were more feasible in wintertime. SF was the main phenomenon at the end of hot season. For central part, SF occurred throughout the year in water column. In the western part, water column was stable in summer and DC happened in most part of water column in winter.     

应用梯度扩散薄膜技术评价天然富硒土壤中硒的生物有效性

有效硒是评价土壤中硒对植物供给能力的重要指标,中国目前尚无测定土壤有效硒的统一方法.化学提取法、土壤溶液法常用于测定土壤有效硒含量,但存在缺乏普遍适用提取剂类型、目标态提取不完全和对非目标态溶解等问题.梯度扩散薄膜(DGT)技术是一种基于解离、扩散动力学的有效态测定方法,已有学者将其应用于土壤有效硒的测定并取得良好效果...     

白洋淀沉积物氮磷赋存特征及其内源负荷

白洋淀环境整治对区域生态文明建设具有重要意义,然而,目前对加剧白洋淀富营养化的内源氮、磷污染负荷依然缺乏系统的研究.本研究以野外调研和室内培养实验相结合形式,在白洋淀主要水域内采集原位柱状沉积物样品,详细地研究了白洋淀沉积物中氮、磷赋存形态、间隙水中氮、磷剖面特征以及沉积物-水界面氮、磷交换特征.结果表明,白洋淀沉积物总氮、总磷含量分别为1230.8~9559.0 mg/kg（均值2379.5 mg/kg）和344.4~915.4 mg/kg（均值608.4 mg/kg）,氮、磷累积污染量大.沉积物中铵态氮赋存量大（3.2~175.8 mg/kg）,由此导致间隙水中铵态氮浓度较高,最高达到28.8 mg/L.沉积物磷形态以Ca-P和Fe-P为主,分别占总量的38.3%~76.1%和3.98%~18.0%,间隙水中磷酸盐浓度已接近甚至高于国内外典型富营养湖区.间隙水中高浓度的铵态氮和磷酸盐导致沉积物-水界面氮、磷交换通量较高,铵态氮平均释放和扩散通量分别为106.37和12.42 mg/（m²·d）;磷酸盐平均释放和扩散通量分别为15.06和2.33 mg/（m²·d）,沉积物内源氮、磷污染负荷较高,已严重威胁到白洋淀水环境质量,迫切需要整治.其中,北部河口区域以及中部府河入湖区和人口密集活动区沉积物氮、磷内源负荷尤为突出,应成为白洋淀沉积物内源污染整治的关键区域.     

金塔绿洲土壤中蒸发/凝结过程的初步分析

利用2005年6月27日～7月4日金塔绿洲地表及0.40m土壤温度观测资料作为边界条件,结合一维土壤热传导方程计算了该时段0.05,0.10和0.20m深处的土壤温度。通过比较同时段观测值与计算值的观测,发现0.05m深处的土壤温度计算值与观测值的差异最大。结果表明,在方程中只需简单考虑浅层土壤蒸发/凝结过程,便可以使...     

Nitrogen cycling across the sediment-water interface in an eutrophic,artificially oxygenated lake

Processes controlling the nitrogen (N) exchange between water and sediment in eutrophic Lake Sempach were studied using three different independent methods: benthic flux chambers, interstitial water data and hypolimnetic mass balances. The sediments released NH ₄ ⁺ (1.1–16.1 mmoles m^–2 d^–1), NO ₂ ^- (0.1–0.4 mmoles m^–2 d^–1) and dissolved organic N (<0.25 mmoles m^–2 d^–1). A net NO ₃ ^- consumption (2.4–11.1 mmoles m^–2 d^–1) related to the NO ₃ ^- concentrations in the overlying water was observed in all benthic chamber experiments. The flux of the reactive species NO ₃ ^- and NH ₄ ⁺ was found to depend on hydrodynamic conditions in the water overlying the sediment. For this reason, benthic chambers overestimated the fluxes of inorganic N compared to the other methods. Thus, in short-term flux chamber experiments the sediment may either become a sink or a source for inorganic N depending on the O₂ concentration in the water overlying the sediment and the stirring rate. As demonstrated with a¹⁵NO ₃ ^- experiment, nitrate-ammonification accounted for less than 12% of the total NO ₃ ^- consumption. After six years of artificial oxygenation in Lake Sempach, a decrease in hypolimnetic total inorganic nitrogen (TIN) was observed in the last two years. The occurrence of dense mats of H₂S-oxidizingBeggiatoa sp. indicated micro-aerobic conditions at the sediment surface. Under these conditions, a shorter distance between the ecological niches of nitrifying and denitrifying bacteria, and therefore a faster NO ₃ ^- -transport, can possibly explain the lowering of TIN by enhanced net denitrification.     

南口-古崖居中生代双峰式岩墙群形成机制的地球化学制约

京北南口至延庆古崖居出露了一套延伸40km、由钾玄质岩石和花岗石组成的双峰式岩墙群。报道了岩墙群的同位素年龄，其K－Ar年龄为114－120Ma，Rb-Sr年龄为128Ma。对南口双峰式岩墙群的17个代表性样品进行了系统的元素地球化学分析，研究结果表明，酸性岩墙和基岩墙是同时来自两个独立的岩浆房，岩浆来自EMI型富集地幔。在此基础上，用岩浆不混熔的双扩散对流模式解释了两个层状岩浆房的形成，正是它们同时为双峰式岩墙群提供了物质来源。     

南方水库季节性热分层消亡对沉积物铁和磷迁移的影响——以南宁市天雹水库为例

为了探究我国南方地区水库季节性热分层消亡前后沉积物铁和磷的迁移规律,于2019年11月-2020年1月对天雹水库多点位(浅水区和深水区)水体理化指标进行原位监测,并利用薄膜扩散梯度技术(DGT)高分辨率获取沉积物有效态铁和磷的浓度分布.结果 表明:(1)天雹水库沉积物有效态Fe和P浓度分别为4.67～18.72和0.0...