水分利用效率--未来农业研究的关键问题

随着生物节水研究的深入发展，让每一滴生产出更多的食物，水分利用效率是未来农业研究的关键问题。抗旱、节水和水分利用效率的概念是不同的，在不同学科中有不同的研究尺度和层次。不同降水量和水资源地区的抗旱、节水和水分利用效率有不同的研究重点和不同的节水农业发展方向。从被动的耐旱性研究到主动的抗旱性研究再到节水研究，在未来必将转向水分高效利用研究。小麦高产育种进化中其水分利用效率有递增的趋势，作物抗旱耐旱育种要转向高水分利用效率育种是势在必行的，因为高水分利用效率育种，可以将抗旱性和丰产性统一于一体。增施肥料是提高大面积中低产田作物水分利用效率和产量的关键措施之一，今后应该继续受到全面重视。     

土壤疏水性研究进展

土壤疏水性是指水分不能或很难湿润土壤颗粒表面的物理现象。土壤疏水性研究不仅有助于合理评价疏水性对生态环境的影响，而且能为当前水土流失问题的解决提供新思路。本文对国内外土壤疏水性研究现状进行总结，着重阐述了土壤疏水性及产生机理、影响因素、测定方法及水文效应，并结合存在问题展望未来的研究，以期为我国开展相关研究提供参考。     

森林水文生态效应及在川西亚高山针叶林群落中的研究

水资源亏缺是世界各国政府和科学家们普遍关注的热点问题，而森林在涵养水源、调节水量、减少径流泥沙、降低洪峰、改善水质等方面具有重要的功能，因此森林水文生态效应研究成为生态学家和水文学家们共同关注的焦点。迄今为止，有关森林水文生态效应的研究主要包括集水区森林水文生态效应、水土保持林水文生态效应和森林水文生态效益研究。川西亚高山针叶林位于长江上游青藏高原东缘，在水土保持和调节流域水量平衡等方面具有重要的生态功能。但迄今为止，有关川西亚高山针叶林水文生态效应的研究较少，主要为短期的、定性的、简单观测，这与其在长江流域水量平衡调节中的作用和地位极不相称。因此，建议在未来的研究中，从生态系统过程的角度加强以下研究：森林流域对径流影响的内在机理、不同树种水文生态效应及对比研究和养分循环及水质方面的研究，另外，因为气候、植被和水文密切相关，而且川西亚高山森林是对全球气候变化最敏感的地区之一，所以有必要探讨大气中CO2浓度升高等对森林水文生态效应的影响。     

我国城市水价改革研究

文章分析了目前我国城市水价存在的主要问题为：总体水价偏低，水价计价和构成不合理，合理的水价应包括资源水价，工程水价和环境水价三个部分，本文讨论了水价三个构成部分的内涵和机制成因。最后，文章讨论了我国城市水价改革应遵循的原则和应采取的对策。     

水肥高效利用灌排系统调控面临的问题研究

通过调查我国水肥利用的现状,指出我国农业水利中干旱缺水、非点源污染、水资源利用率低下和灌排系统不配套等问题,提出灌区水肥高效利用需深入研究的热点问题,对探讨水肥高效利用和灌排系统管理理论,指导我国灌排系统精量调控,以最少的水肥投入量获取最佳的灌区产量和经济及生态环境效益,具有重要意义.     

城市化背景下成都市水资源安全及可持续发展

成都市作为西部大开发重镇和长江中上游的重要中心城市，面临着总供水量不足、水质污染严重、用水格局改变、水旱灾害和水量年际波动大等水资源问题，涉及到21世纪成都市城市化进程中的水资源安全和城市的可持续发展。本文从水资源安全的角度，以可持续发展的观点为指导思想探讨了成都市现阶段在城市发展过程中对水资源开发利用和管理中存在的主要问题，提出了保障成都市城市用水安全，实现水资源可持续利用的途径。     

Peptide YY enhances NaCl and water absorption in the rat colon in vivo

Peptide YY (PYY) is thought to possess paracrine and endocrine functions. The highest concentrations of this peptide are in the colonic mucosa. The effect of PYY on electrolyte and water transport in the rat colon was studied in vivo. Under urethane anesthesia, rat colonic loops were perfused at a constant rate with physiological buffer solution containing phenol red as a nonabsorbable volume marker, and net movements of water, sodium, chloride and potassium in the perfused colon were determined every 10 min. Intravenous administration of PYY produced a dose-dependent increase in the net absorption of sodium chloride and water, as well as a decrease in the net secretion of potassium. PYY inhibited the reduction in net absorption of sodium chloride and water evoked by vasoactive intestinal peptide (VIP), but did not affect the VIP-evoked increase in net potassium secretion.These findings suggest that PYY acts as an enhancer of sodium chloride and water absorption and as an antagonist to VIP-induced secretion in the colon.     

Water and electrolyte movements across the duodenal mucosa in laying hens during in vivo perfusion]

The net water movements through the duodenum in laying hens are directly dependent on the applied osmotic gradient. The passive water permeability (Lp) of the mucosa is 6 times higher during absorption (mucosa to serosa: 70 microliter/h/mOsm) than in the opposite direction (secretion: 11.5 microliter/h/mOsm) and its semi permeability is 0.49 (reflexion coefficient sigma). Net sodium and potassium movements seem to be linked to net water flux. Duodenal water absorption should not be explained by a process of passive permeability.     

黄腊溪饮用水源地非点源污染及水环境容量初探

以四川省大英县隆盛镇黄腊溪饮用水源地为研究对象,根据当地丰水期的实际情况和实测数据建立了一维水质模型。测试结果表明,8月CODcr、TN和9月TN已超过地表水Ⅲ类水质目标。结合水环境容量计算公式得知：8月上中旬污染物中CODcr和TN各需要削减408．25t·a^-1和2．52t·a^-1的入河量,而9月则应削减110．92t·a^-1的TN入河量才能满足当地饮用水水源地标准。最后针对污染源的排放情况提出相应的水环境防治对策和建议。     

Peptide YY enhances NaCl and water absorption in the rat colon in vivo.

Peptide YY (PYY) is thought to possess paracrine and endocrine functions. The highest concentrations of this peptide are in the colonic mucosa. The effect of PYY on electrolyte and water transport in the rat colon was studied in vivo. Under urethane anesthesia, rat colonic loops were perfused at a constant rate with physiological buffer solution containing phenol red as a nonabsorbable volume marker, and net movements of water, sodium, chloride and potassium in the perfused colon were determined every 10 min. Intravenous administration of PYY produced a dose-dependent increase in the net absorption of sodium chloride and water, as well as a decrease in the net secretion of potassium. PYY inhibited the reduction in net absorption of sodium chloride and water evoked by vasoactive intestinal peptide (VIP), but did not affect the VIP-evoked increase in net potassium secretion. These findings suggest that PYY acts as an enhancer of sodium chloride and water absorption and as an antagonist to VIP-induced secretion in the colon.     

Changes in water permeability of an insect egg in response to level of water in the environment

Summary The water permeability of eggs of the southern corn rootworm, Diabrotica undecimpunctata howardi Barber, varied depending on the previous experience of the eggs. Eggs acclimated in a water vapor system were seen to be less permeable than eggs acclimated in contact with moist paper, as measured by the rate of loss of water from the eggs and the susceptibility of the eggs to death from desiccation. This is the first known report of the ability of an insect egg to adapt to the level of water available in the environment.     

水质遥感监测研究进展

本文对近年来应用遥感技术对地表水水质进行监测的研究进展做了总结.在描述地表水体的光谱特征基础上,简述了水质遥感监测的基本原理,其次总结了水质反演的方法和可用的卫星遥感数据源;最后,对此领域存在的问题和今后的重点研究方向作了探讨。     

农村水资源自动化量测系统

针对我国目前农村水资源量测和管理水平较低，农村用水系统效率低下的问题，介绍农村水资源自动化量测系统的研制和应用。该系统应用先进的电子量测技术、计算技术及多项专利技术，采用最新研制的新型流速旋浆传感器、多功能智能流速仪和流速流向仪同步测量大型农业灌区的渠道流速与流量。该系统在祁东县曹口堰示范区水库灌区的应用表明，渠系水利用率可提高10％，实现了水资源量测与管理的数字化、动态化、智能化与一体化。     

Chronic cadmium intake results in dose-related excretion of metallothionein in urine

Urinary excretion of metallothionein was measured by radioimmunoassay in rats given drinking water containing 5 or 50 mg cadmium/l for up to 2 years. The metallothionein levels corresponded to the concentration of cadmium in the drinking water and increased linearly over the course of the study. These results demonstrate that urinary metallothionein is a sensitive biological indicator of oral cadmium exposure.     

元谋干热河谷区民营水土保持效益评价

民营水土保持是当今水土保持生态建设中出现的一种新模式,是水土保持走向市场的重要标志。本文以农户调查数据为基础,运用层次分析法,对元谋干热河谷区民营水土保持效益进行评价。研究显示,目前民营水土保持是以经济效益为主导,兼顾生态效益和社会效益;农户的思想开放程度、经营模式和理念、技术水平、市场等因素是影响效益的主要因素,提出政府应建立完善的制度体系,支持鼓励民营水土保持的发展。     

饮用水源水质评价的模糊聚类模型的研究

考虑到饮用水源样本并没有严格的属性,以及它们在形态和类属方面存在看中介性,确定了对人类生理健康影响较大的高锰酸盐指数、生化需氧量、总氮、氨氮、氟化物、总磷、溶解氧等9项评价因子;将特征空间中一组没有类别标记的矢量按某种相似性准则划分到若干个子集中,实现每个子集代表整个样本集的某个或者某些特征和性质;建立起基于模糊聚类法的饮用水源水质评价模型。最后,将所建模型应用到阜新市目前饮用水源地水质评价中,应用效果表明：所建模型既能有效地判断饮用水源水质类别,又能确定水体中主要污染物和主要污染源,通过不同评价方法结果的比较分析,体现了所建模型的良好有效性和适用性。     

Mechanoelectrical transduction,ion movement and water stasis in uromodulin

Mechanical movement of a column of the urinary glycoprotein uromodulin modulates an applied voltage. This change is a property of the glycoprotein and its interaction with the walls of the container and is related to its capacitance. The voltage modulation is not accompanied by changes in rotationally restricted water as has been reported for hyaluronic acid. Diffusion experiments with tritiated water also support the hypothesis that uromodulin acts as a water barrier, but allows ion movement.     

Mechanoelectrical transduction, ion movement and water stasis in uromodulin.

Mechanical movement of a column of the urinary glycoprotein uromodulin modulates an applied voltage. This change is a property of the glycoprotein and its interaction with the walls of the container and is related to its capacitance. The voltage modulation is not accompanied by changes in rotationally restricted water as has been reported for hyaluronic acid. Diffusion experiments with tritiated water also support the hypothesis that uromodulin acts as a water barrier, but allows ion movement.     

西北地区建立区域节水型社会经济体系的突破点

西北地区是我国水资源最为缺乏的地区，水资源短缺和利用不合理巳构成了我国西北地区区域经济可持续发展的主要障碍。本文通过对西北地区水资源总量及利用现状的分析与评价，指出西北地区经济可持续发展的关键是建立区域节水型社会经济体系，而其突破点在于严格控制垦荒，适度压缩灌溉农田面积，改变不合理的水资源利用结构，并对该突破点的意义进行了探讨。     

基于主成分分析法的面源污染对李子口小流域水环境影响评价

以四川省南部县李子口小流域为研究对象,采用主成分分析方法,通过SPSS15．0软件对水质进行了定量评价,并结合综合污染损害指数对水质作出定性评价。结果表明：该流域水质污染高峰主要集中在6～10月份,11月份开始出现下降趋势,次年4月份开始出现升高状态,结合第一、二、三主分所反映的信息量,7月份主要为磷污染,5、7、8月份主要是有机物污染,而氮污染则集中在10月份。最后根据评价结果分析农业面源污染的影响。