我国建立防旱抗旱减灾长效机制的思考

近年,我国干旱灾害呈现多发频发趋势,对我国的城乡居民用水安全、粮食安全、生态安全构成了严重威胁,制约了我国经济社会的可持续发展。通过分析我国抗旱减灾面临的形势和抗旱减灾工作存在的主要问题,结合我国抗旱减灾工作的需求,提出了我国建立防旱抗旱减灾长效机制的建议。     

Environmentally stable isotopes and groundwater recharge in the eastern Nile delta

In the study oxygen‐18 and deuterium levels in groundwater and surface water samples are used in studying the source of recharge. The results show that the area bounded by the Nile and the Ismailia Canal is recharged directly from surface water. In some localities the recharge occurs indirectly (after evaporation). There is a mixing between different sources of water, recent water (surface water), old water (paleowater), flood water (rain) and sea water (connate) in some wells. Interpretation of the isotopic composition data indicates that the Nile branch (Damietta) and Ismailia Canal (surface water) are the main sources of recharge to groundwater.     

Assessing trophic position quantification methods for three piscivorous freshwater fish using stable isotopes and stomach contents

Accurate trophic position (TP) estimates are important for the development of ecosystem-based management plans. TPs can be quantified by carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotopes in tissues, but these can disagree with observed and perceived feeding ecology. A recent method that has used a scaled diet-tissue discrimination factor (DTDF), reflecting the inverse relationship between DTDF and δ¹⁵N, was found to better describe TPs of predatory fish species in marine ecosystems, but this has not been tested in freshwater ecosystems. Here, we compare methods of TP estimations in the Lake Huron-Erie corridor (HEC), a system where high diversity of prey items has contributed to the concern that foraging ecology of piscivorous fish species is poorly understood. Using δ¹⁵N and δ¹³C, we quantified TP of longnose gar (Lepisosteus osseus), largemouth bass (Micropterus salmoides), and northern pike (Esox lucius) to assess the efficacy of a scaled DTDF compared to traditional DTDF isotope methods and stomach content analysis (SCA). The scaled DTDF method produced TP estimates that were at times consistent with SCA and were generally higher and with a greater range among individuals than non-scaled DTDFs. The scaled method was not sensitive to baseline choice nor influenced by incorporating carbon source in the model. Greater variability of TP estimates using a scaled DTDF suggests more complex trophic structuring in the upper trophic level guild of the HEC. These results, particularly the lack of baseline sensitivity, provide support for using the scaled DTDF in freshwater food web characterization.     

基于稳定同位素的策勒河流域山区河流蒸发损失估算

为探究昆仑山北坡山区流域水体蒸发损失垂直变化情况,基于2016年5-12月昆仑山北坡中段策勒河流域不同水体同位素数据,运用蒸发富集模型和稳定同位素（¹⁸O和²H）方法,研究了流域内不同水体的同位素时空变化特征,分析了策勒河流域的补给来源,并根据蒸发富集模型估算了流域内不同海拔地区同位素的蒸发损失。结果表明：流域内不同水体同位素的特征呈高山区贫化、荒漠区富集的趋势;策勒河河水与地下水存在密切的水力联系;策勒河流域在不同海拔的平均蒸发损失：高山区为24.99%、中山区为29.04%、荒漠区为35.00%。研究结果对理解区域水平衡及其对山区生态系统气候变化的响应具有重要意义。     

松花江和沱江等重大水污染事件的反思

针对我国处理突发性水污染事件的现状,简要分析了突发性水污染事件导致的危害及其可控性,提出亟待解决的三方面问题,认为最有效的途径就是尽快建立并完善以国家确定的重要流域为单元的突发性水污染事件应急处理机制,并对这个机制的建设进行了初步探讨。     

考虑残留氮对非稳定流场硝态氮淋失贡献的传递函数模型Ⅰ.地中渗透计验证

本文通过引入溶质迁移距离的概率密度函数的修正系数，将Jury等提出的模拟非稳定流条件下土壤保守溶质运移的传递函数模型理论扩展到考虑土壤剖面存在残留氮分布的土壤中，构造了一个能估算表施和残留氮对土壤硝态氮淋失动态贡献的传递函数模型。通过与野外地中渗透计实验资料的对比，表明该模型具有一定的仿真精度，模拟的土壤硝态氮累积淋失量的相对误差小于15％。     

Nucleic acids: indicators for dynamic processes of clogging in soil filter systems.

A high-performance liquid chromatography (HPLC)-method was established to quantify the development and degradation of DNA, rRNA and tRNA in the Langenalb soil filter fed with combined sewer overflow. The DNA served as a parameter for the microbial biomass and the RNA/DNA ratio for the growth rate. For nucleic acids, quantification samples were taken at different depths and sections of the clogged and the unclogged soil filter. Highest DNA concentrations were found at a depth of 0-2 cm in the clogged soil filter. During a starvation period of three months the DNA- and RNA-concentrations decreased twofold at depths between 0-8 cm. The higher nucleic acid concentrations at depths of 10-40 cm in the unclogged soil filter were attributed to a shift of the starved microorganisms. Similar RNA/DNA ratios in the clogged and the unclogged soil filter indicate similar growth rates and metabolic activities. It could be proven that the clogging of the soil filter was due to the microbial biomass and the DNA concentration, respectively.     

Diet and trophic niche space and overlap of Lake Ontario salmonid species using stable isotopes and stomach contents

Lake Ontario supports a diversity of native and non-native salmonids which are managed largely through stocking practices. Ecological changes (e.g., invasive species) altering the food web structure accompanied with shifts in prey abundance, necessitate understanding the trophic niches of Lake Ontario salmonids to aid in management. The objectives of this study were to quantify salmonid (5 species) trophic niches and dietary proportions using stable isotope ratios (δ¹³C and δ¹⁵N) of a large sample set (adult fish (>300?mm; n?=?672) and key offshore prey (5 species, n?=?2037)) collected across Lake Ontario in 2013. Estimates of prey based on stable isotope ratios were similar to stomach contents. Based on stable isotope ratios, non-native prey dominated salmonid diet; in particular alewife (Alosa pseudoharengus) constituted the majority (0.31 to 0.93) of all salmonid diets, and round goby (Neogobius melanostomus) contributed 0.26 and 0.19 of brown trout (Salmo trutta) and lake trout (Salvelinus namaycush) diets, respectively. Trophic niche overlap was high between all salmonids, except lake trout. The largest trophic niche overlap occurred between Chinook (Oncorhynchus tshawytscha), coho (Oncorhynchus kisutch), and Atlantic salmon (Salmo salar), and their reliance on alewife infers a strong pelagic foraging strategy. Lake, brown and rainbow (Oncorhynchus mykiss) trout had larger and/or more distinct trophic niches indicative of a more variable diet across individuals and utilizing different foraging strategies and/or habitats. Overall, Lake Ontario salmonids maintained a high reliance on alewife, and their potential for plasticity in diet provides important information to management regarding population sustainability.     

非公有制经济进入公共水利服务领域的对策与思考

在现阶段公共水利服务已难以满足经济社会全面发展需要的形势下,非公有制经济进入公共水利服务领域既有有利条件,又有来自主客观方面的障碍.对非公有制经济进入公共水利服务领域,要采取实行科学规划、规范准入程序,转变政府职能、优化发展环境,拓宽投入渠道、实行重点扶持,组建行业协会、聚集民间合力等措施,大力发展和积极引导.     

滴灌系统运行方式对砂壤土水氮分布影响的试验研究

以一种砂粒含量高达95%的砂土为对象,开展了滴灌施肥灌溉条件下,灌水器流量、灌水量和系统运行方式对水分、硝态氮和铵态氮分布影响的室内试验。灌水器流量的变化范围为0.5～2.0L/h,灌水量为6～7.7L;系统运行方式包括不同灌水和施肥次序组成的4种方案。研究结果表明,径向和垂直湿润距离随灌水量的增加呈幂函数关系增加;灌水量相同时,随灌水器流量的增大,灌水器周围的土壤含水率增加,垂直湿润距离减小,而径向湿润距离变化不大;灌水器流量一定时,垂直湿润距离随灌水量的增大而明显增加。对氮素分布的测试结果表明,硝态氮在湿润体边界存在累积现象;铵态氮在灌水器附近出现浓度高峰,且铵态氮集中在灌水器周围15cm范围内。滴灌施肥灌溉系统运行方式对硝态氮在土壤中的分布影响明显,建议采用最初用灌水施肥总时间的1/4灌水,再用1/2时间施肥,最后用1/4时间冲洗管道的运行方式,以便将施入土壤的氮素最大限度地保留在作物根区内,防止硝态氮淋失。     

Removal of nitrogen in different wetland filter materials: use of stable nitrogen isotopes to determine factors controlling denitrification and DNRA.

Laboratory incubations with varying O2 and NO3 concentrations were performed with a range of filter materials used in constructed wetlands (CWs). The study included material sampled from functioning CWs as well as raw materials subjected to laboratory pre-incubation. 15N-tracer techniques were used to assess the rates of denitrification versus dissimilatory nitrate reduction to ammonium (DNRA), and the relative role of nitrification versus denitrification in producing N2O. The N2O/(N2 + N2O) product ratio was assessed for the different materials. Sand, shell sand, and peat sustained high rates of denitrification. Raw light-weight aggregates (LWA) had a very low rate, while in LWA sampled from a functioning CW, the rate was similar to the one found in the other materials. The N2O/(N2 + N2O) ratio was very low for sand, shell sand and LWA from functioning CWs, but very high for raw LWA. The ratio was intermediate but variable for peat. The N2O produced by nitrification accounted for a significant percentage of the N2O accumulated during the incubation, but was dependent on the initial oxygen concentration. DNRA was significant only for shell sand taken from a functioning CW, suggesting that the establishment of active DNRA is a slower process than the establishment of a denitrifying flora.     

计算层状土稳定入渗率的饱和层最小通量法

根据土壤水动力学原理,提出了计算多层土壤稳定入渗率的饱和层最小通量法。采用HYDRUS-1D数值模拟软件,模拟了不同土壤表面水头、多层土壤特性下的稳渗过程,根据模拟结果对饱和层最小通量法进行了检验。结果表明,这种计算多层土壤稳渗率的方法物理意义明确、误差较小。与改进的Green-Ampt公式相比,该方法不需要考虑下层土壤的进水吸力,同时考虑了多层土壤对入渗的影响,更适用于实际情况下分层土壤稳定入渗率的估算,可以为水资源量评价、环境污染评价和相关工程设计等领域提供理论依据。     

畦灌施肥模式对土壤水氮时空分布的影响

对冬小麦生长期施用尿素条件下不同畦灌施肥模式的土壤水和氮时空分布状况及变化趋势开展研究,评价作物有效根系层土壤水氮沿畦长空间分布均匀性,探讨适宜的畦灌施肥模式。结果表明,畦灌施肥模式差异对作物有效根系层土壤水分沿畦长空间分布状况及其分布均匀性的影响较小,而对土壤氮素的影响较为明显。基于入畦单宽流量4L.s-1.m-1和在灌溉全程内均匀施肥的畦灌施肥模式,可在返青水和扬花水灌后2d作物有效根系层内形成较佳的土壤水氮空间分布状态及其分布均匀性,该效果对返青水可延续到灌后10d。采用较大流量和全程施肥的畦灌施肥模式,可为作物高效吸收利用水肥提供相对均布的土壤水氮状态。     

Fluoride contamination in the Bongo District of Ghana,West Africa: geogenic contamination and cultural complexities

This research investigated the extent of fluoride contamination in the Bongo District of northeast Ghana and the relationships of this fluoride contamination to the underlying geology and precipitation patterns, social and cultural attitudes towards water, and age divisions inherent in water usage patterns and the consequent demands placed on a borehole. The fluoride concentrations measured in the area are higher than reported in earlier literature. High fluoride levels are geographically confined to one geologic formation and appear to be inversely correlated to regional precipitation. Fluoride variation studies, tracking concentrations over 8 months, also reflect this link to local precipitation patterns. This localized analysis of water contamination issues addresses broader gender and policy issues inherent in supplying potable water.     

An extension of the Anaerobic Digestion Model No. 1 to include the effect of nitrate reduction processes.

Nitrate reduction processes were incorporated into the IWA Anaerobic Digestion Model No. 1 (ADM1) in order to account for the effect of such processes on fermentation and methanogenesis. The general structure of the ADM1 was not changed except for modifications related to disintegration and hydrolysis of complex organic matter and decayed biomass. A fraction of butyrate/valerate and propionate degraders was assumed to be the fermentative denitrifiers carrying out fermentation in the absence of N-oxides. Nitrate reduction proceeded in a stepwise manner to nitrite, nitric oxide, nitrous oxide and nitrogen gas using four substrates as electron and/or carbon source. The utilization of the four substrates and N-oxides was based on stoichiometry and kinetics. The inhibitory effect of N-oxides on the methanogens was accounted for by the use of non-competitive inhibition functions. Model simulations were compared with experimental data obtained with a batch, mixed fermenting and methanogenic culture amended with various initial nitrate concentrations.     

土壤空间变异对滴灌水氮淋失风险影响的模拟评估

滴灌水氮淋失是系统设计和运行管理需要考虑的重要因素。本研究利用HYDRUS-2D软件构建了滴灌条件下的水氮运移模型,通过局部敏感性分析和全局敏感性分析方法研究了砂壤土土壤水力参数、初始含水率和土壤溶液中初始NO3--N 浓度的空间变异对水分渗漏率和NO3--N 淋失率的影响。结果表明,水分渗漏率和NO3--N 淋失率随饱和含水率的增大而明显降低,随土壤初始含水率的增大而明显升高。弱变异条件下,水分渗漏率和NO3--N 淋失率的变异性主要由土壤初始含水率、饱和含水率和饱和导水率的空间变异引起;中等变异条件下     

开发建设项目水土保持方案编制及设计的若干思考

水土保持方案是开发建设项目可行性研究阶段立项必备的技术文件。方案的编制应将重点放在开发建设项目的可行性研究阶段,水土保持方案要对主体工程设计提出约束条件。水土保持设计的重点是初步设计, 主管部门应加强对初步设计阶段水土保持章节的审查。     

浅谈公路建设必须与水土保持并重

公路建设的同时,引发了一系列水土流失问题。就张家口市公路建设中水土保持治理工程的准备、技术要点和存在的问题及建议等进行探讨,使公路水土保持工作的实施更具有可操作性。     

松原市旱灾分析及抗旱减灾对策

近年来,松原市的干旱灾害造成的经济损失呈连年上升趋势,给工农业生产、人民生活和生态环境造成了巨大损失,成为制约经济可持续发展的瓶颈问题,本文通过对旱灾状况、典型干旱年及干旱成因进行综合分析,提出相应的抗旱减灾对策.     

塑性混凝土配合比设计及试验方法探讨

塑性混凝土已成功应用于三峡二期围堰防渗墙。结合工程实际探讨了塑性混凝土原材料的选择和配合比设计的基本方法,并总结了塑性混凝土的物理力学性能和参数试验方法。试验表明,优化配合比设计后的塑性混凝土能满足防渗墙良好的变形和防渗性能的工程设计要求。