WATER PROBLEMS IN THE INDUS FOOD MACHINE1

ABSTRACT: Examples are drawn from the Indus Basin to explain why on-farm water management problems restrict the output of agricultural products in many LDC's. Data is presented to illustrate the low level of water management knowledge of both the farmers and the current extension agents. Examples of the level of corruption and its effect on the operating system are illustrated. Several requirements that must be met before a large-scale irrigation scheme will actually increase the welfare of LDC's farmers are presented.     

POTENTIAL IMPACT OF IRRIGATION ON WATER RESOURCES IN THE LITTLE WABASH BASIN OF ILLINOIS1

The level of water demand for supplemental irrigation and the impact of such demand on water supplies were estimated, as a function of the price of corn (Zea Mays L.). The method of estimation was based on an economic analysis of irrigation practice which assumed constant irrigation costs, profit maximizing behavior on the part of irrigators, and which was deliberately structured to underestimate the level of irrigation water use. The analysis was applied to and used data from the Little Wabash basin in Illinois. No irrigation was predicted at a corn price below $3.50 per bushel. Between $3.50 and about $6.50 per bushel, irrigation was estimated to be profitable for a small region of the basin where acceptable groundwater was available. Above about $6.50 to $7.50, irrigation was found to be profitable in the remainder of the basin, where impoundment storage was required. The potential impact on the water resources of the basin is significant. For a corn price between $3.50 and about $6.50, the probability of a shortfall, defined as the event where the potential demand exceeds the supply, was estimated to be between 2 percent and 20 percent during the growing season. Above about $7.50, this probability was found to be about one-third. The development of policies to control withdrawals for irrigation and other uses is endorsed.     

再生水利用健康风险暴露评价

结合北京市再生水利用工程,建立了再生水用于公园绿化、道路降尘和冲洗作业时,职业人群和公众的暴露评价方法和评价模型,通过现场调研和监测分析,首次提出了再生水利用暴露人群的再生水日摄入量和终生日均暴露剂量,为健康危险度分析提供定量依据.其中公园绿化职业人群通过皮肤和吸入的日均总摄入量为0.07L/d,公众为0.04～0.05L/d,消毒副产物的日均暴露剂量为:职业人群经呼吸途径终生日均暴露剂量为2.8×10^-7～1.2×10^-5mg·(kg·d)^{-1相似文献}   

污水灌溉对土壤重金属含量、酶活性和微生物类群分布的影响

以沈阳张士灌区长期污灌的农田土壤为对象,研究了土壤重金属、土壤酶活性、微生物生物量和种群分布特征,分析了土壤微生物参数与土壤重金属和土壤性质的相关关系.结果表明,虽然已停止污灌十余年,张士灌区农田土壤仍存在Cd、Zn、Cu等多种重金属污染.土壤Cd污染最严重,含量达1.75～3.89 mg·kg-1.土壤耕作层(0～30cm)Zn、Cu、Pb总含量随土层深度增加逐渐减少,而Cd元素的垂直分布呈向下迁移的趋势.Cd、Zn、Cu、Pb等4种重金属含量水平分布特征相似,均为1号样地＞2号样地＞3号样地＞4号样地.相关性分析表明,张士灌区土壤酶活性、微生物生物量和种群分布受重金属污染和土壤养分的影响,土壤养分含量(有机碳、N、P、K)对微生物的正面效应大于重金属对微生物的负面效应.土壤全量Cd和速效K对微生物参数的影响最为明显,Cd含量与多酚氧化酶活性和微生物生物量(Cmic)呈极显著负相关,与纤维素酶活性呈极显著正相关(P＜0 01),速效K含量与多酚氧化酶活性、微生物生物量以及可培养微生物种群数量均呈极显著正相关(P＜0.01).     

Water Appropriation Systems for Adapting to Water Shortages in Iraq

Climate variability and population growth have intensified the search internationally for measures to adapt to fluctuations in water supplies. An example can be found in the lower part of the transboundary Tigris‐Euphrates Basin where water shortages in 2008‐2009 resulted in high economic costs to irrigation farmers. Losses to irrigators in the lower basin have made a compelling case to identify flexible methods to adapt to water shortage. Few published studies have systematically examined ways to enhance the flexibility of water appropriation systems to adapt to water shortage. This article addresses an ongoing challenge in water governance by examining how profitability at both the farm and basin levels is affected by various water appropriation systems. Four water appropriation systems are compared for impacts on farm income under each of three water supply scenarios. Results show that a (1) proportional sharing of water shortages among provinces and (2) unrestricted water trading rank as the top two appropriation systems. The shadow price of water for irrigation rises from zero at a full water supply level to US$93/1,000 m³ when supply falls to 20% of full levels. Similar methods could be used to analyze challenges facing the design or implementation of water appropriation systems in the world's irrigated regions.     

都江堰市生态市建设

将都江堰市建设成我国西部第一个国家级生态市,该市地处我国大地形中第一阶梯向第二阶梯过渡地带,具有物种、生态系统和景观多样性优势;是古代著名水利工程都江堰的所在地,对于成都市和成都平原起着水资源调控和生态屏障作用。该市是著名风光名胜区和旅游城市,具有城市、农村、高中山、丘陵、平原、水域等广泛的功能示范意义。都江堰市具有建成生态市的良好自然条件和社会经济基础,但也面临着严峻的挑战。生态市建设的重点是要保护和发挥该市亚热带的自然生态系统的服务功能,开发与生态良性循环相协调、与环境友好的产业,构建起循环经济的体系和经营机制,建成风光秀美、经济发达、社会文明、人居环境舒适的城市。     

碱性矿化水灌溉对土壤溶质运移的影响

经过连续几年的灌溉试验可知,应用2.5 g稬-1以下的低矿化水灌溉是安全的,超过此值土壤积盐和碱化明显。灌溉后,土壤中溶质运移受多因素影响。在阳离子分布中,水平方向Na+随灌溉水矿化度增大而增多,Ca2+、Mg2+变化不大;土壤剖面上,从表层至60 cm土层,先以Ca2+、Mg2+为主,过渡到Na+、Ca2+、Mg2+共同占优,再发展为以Na+占优。阴离子的分布中,水平方向,随灌溉水矿化度增大HCO3-增多;土壤剖面上,从表向里,先以Cl-或SO42-为主,过渡到C1-、SO42-、HCO3-均分局面,再发展以HCO3-占优。灌溉后土壤pH值在0~20 cm变化不明显,大于20 cm土层有一定增加。土壤中的SAR和ESP均以大于1.5 g稬-1的碱性低矿化水灌溉后增加明显,碱化层由下向上抬升,小麦田碱化速度快于玉米田。     

The Impact of the Hyperacid Ijen Crater Lake. Part I: Concentrations of Elements in Crops and Soil

In Asembagus (East Java, Indonesia) irrigation water is contaminated with effluent from the hyperacid Ijen Crater Lake resulting in a low pH and high levels of various elements. As a first step towards a risk assessment, locally produced food items (rice, maize, cassava leaf, cassava root, peanuts) were collected and concentrations of As, B, Ca, Cd, Co, Cu, Fe, Mg, Mn, Mo, Ni, Pb, V, Zn were compared to samples from a reference area and with literature values. Further, concentrations in rice were compared to total soil concentrations in paddy fields. Compared to the reference area, food items produced in the contaminated area had increased levels of Cd, Co, Ni and Mn in particular, while levels of Mo were lower. In contrast, total soil concentrations of Cd and Mn in particular have decreased whereas especially Mo was increased. In combination with the observed soil acidification, it is likely that the bioavailable concentration of most elements in the contaminated soil is higher (except for Mo) due to an increased weathering rate and/or input via the contaminated irrigation water. In terms of human health, concentrations in foods were generally within normal literature values. However, it was observed that essential elements (in particular Fe) known for their inhibitory effects on e.g. Cd and Mn toxicity did not accumulate in crops whereas Cd and Mn did.     

施用缓/控释氮肥对玉米苗期土壤生物学活性的影响

采用盆栽试验并模拟田间生态环境,研究了施用不同种类缓/控释氮肥对玉米苗期土壤脲酶活性、硝酸还原酶活性、微生物生物量碳和氮含量的影响。结果表明,在玉米苗期,施用脲酶抑制剂nBPT涂层尿素及醋酸酯淀粉包膜脲酶抑制剂nBPT涂层尿素对土壤脲酶活性有显著抑制作用,脲酶活性分别为49.25和48.13μg.g-1.d-1(以NH3-N计);施用不同种类缓/控释氮肥时土壤硝酸还原酶活性普遍增强,其活性在0.76~1.03μg.g-1.d-1(以N计)之间,但相互间无显著差异,脲酶抑制剂nBPT对土壤硝酸还原酶活性无显著作用;施用不同种类缓/控释氮肥时土壤微生物生物量碳、氮含量变化趋势一致,施用脲酶抑制剂nBPT涂层尿素时微生物量最多,微生物量碳、氮含量分别为248.19和56.53 mg.kg-1,施用丙烯酸树脂包膜脲酶抑制剂nBPT涂层尿素时微生物量最少,微生物碳、氮含量分别为104.80和23.94 mg.kg-1。施用不同种类缓/控释氮肥时土壤生物学活性的变化特点表明,丙烯酸树脂包膜与脲酶抑制剂nBPT涂层相结合的缓/控释肥料控释效果最好。     

天津污灌区苯并（a）芘、荧蒽和菲生态毒性的风险表征

运用概率风险评价方法表征和比较了天津污灌区3种多环芳烃对生物影响的风险性。根据各物质的环境暴露浓度和相应急性毒性值的累计概率分布曲线估计了各物质相对风险性的大小。采用联合概率曲线方式比较了不同暴露概率水平条件下3种多环芳烃的相对风险。结果表明，该地区目前菲的总体风险性高于另两种化合物，苯并（a)芘的总体风险性最低。而低暴露风险条件下（受威胁生物不超过20％），苯并（a)芘的风险较大，菲次之，荧蒽风险相对较低。