地下渗滤系统微生物菌剂的研制及对污水的处理效能

地下渗滤污水处理系统具有投资少、设备简单、费用低、管理简便等特点。主要是通过添加自行研制的微生物菌剂改善土壤性状和增强地下渗滤系统中微生物活性,并进行菌剂的生理生化试验和污水处理试验;试验表明菌剂具有较高的微生物活性,添加在地下渗滤系统中,缩短了系统启动运行时间,提高了有机物降解和硝化效率。     

有限供水条件下农田灌溉时量优化——以河北省运东地区为例

本文探讨了灌溉水源限定条件下,农田灌溉时量优化计算方法,并以河北省运东地区3种主要作物为例进行了系统演算。从计算结果及其分析看,时量优化的经济效益明显,时量优化模型作为一种计算方法亦具有一定的实用意义。     

北京地区渗灌条件下冬小麦田间土壤水分动态及节水机理的研究

根据对渗灌条件下冬小麦田间土壤水分、冬小麦生长发育状况及产量的观测 ,研究了渗灌条件下冬小麦田间土壤水分动态及节水机理。试验结果表明 ,渗灌条件下田间土壤水分动态变化与灌溉、冬小麦生长发育状况及气象条件密切相关 ;渗灌用于冬小麦灌溉可以明显起到节约灌溉用水的作用 ,并有利于冬小麦的生长发育及产量形成。在冬小麦的整个生育期 ,采用渗灌比喷灌田间耗水量减少了44 4mm ,灌溉用水节约了1200m3/hm₂ ,而最终产量提高了714kg/hm₂ ,渗灌条件下作物水分利用效率为21 11kg/(hm₂·mm) ,比喷灌条件下高4 49kg/(hm₂·mm)。渗灌用于冬小麦灌溉的节水机理主要表现为两个方面 :①每次灌溉后 ,地表湿度较喷灌条件下要小得多 ,减小了土壤水分的无效物理蒸发 ;②渗灌利于冬小麦根系向地中供水层 (20～120cm )延伸 ,提高了冬小麦根系对灌溉供水层的水分利用     

3种不同基质潜流湿地对磷的去除效果

基质是潜流式人工湿地污水处理系统的重要组成部分,直接影响到系统的处理效果.本文研究了由沸石、页岩陶粒和碎石3种不同基质构建的潜流式人工湿地对磷的去除效果.结果表明,在设计水力停留时间3 d,连续进出水情况下,碎石单元对磷的去除效果最好,页岩陶粒单元次之,沸石单元效果最差,平均去除率分别为95%、60%和35%.在潜流式人工湿地污水处理系统运行初期观察到磷释放现象,沸石单元最为明显.进水磷浓度较低时,磷的去除率随浓度升高而升高,当正磷、总磷浓度分别升高到2.4～2.5和3.1～3.3 mg/L时,正磷、总磷的去除率开始迅速下降.     

沸石床处理农田暴雨径流氮磷中试研究

对沸石床去除农田暴雨径流中氮磷进行了人工模拟中试研究。结果表明 ,沸石床对暴雨径流有较好的净化作用 ,系统水力负荷介于 0 2 4m3 /m2 ·d和 2 4m3 /m2 ·d之间时 ,暴雨径流中主要氮磷污染物的总去除率可达 :TN 4 5 % ,NH4 N 6 0 % ,NO3 N 2 0 % ,TP 38%。平均去除能力为TN 8 14g/m2 ·d ,NH4 N 3 6 4g/m2 ·d ,NO3 N 1 17g/m2 ·d ,TP 0 5 9g/m2 ·d。茭草床的效果明显好于芦苇床 ,植物床的效果明显好于空白对照床。系统在最大进水能力 31L/min下 ,对氨氮仍然能保持4 0 %以上的去除率     

Elevated Levels of Cadmium and Zinc in Paddy Soils and Elevated Levels of Cadmium in Rice Grain Downstream of a Zinc Mineralized Area in Thailand: Implications for Public Health

Prolonged consumption of rice containing elevated cadmium (Cd) levels is a significant health issue particularly in subsistence communities that are dependent on rice produced on-farm. This situation is further exacerbated in areas of known non-ferrous mineralization adjacent to rice-based agricultural systems where the opportunity for contamination of rice and its eventual entry into the food chain is high. In the current study, an assessment of the degree of soil Cd and Zn contamination and associated rice grain Cd contamination downstream of an actively mined zone of Zn mineralization in western Thailand was undertaken. Total soil Cd and Zn concentrations in the rice-based agricultural system investigated ranged from 0.5 to 284 mg kg⁻¹ and 100 to 8036 mg kg⁻¹, respectively. Further, the results indicate that the contamination is associated with suspended sediment transported to fields via the irrigation supply. Consequently, the spatial distribution of Cd and Zn is directly related to a field’s proximity to primary outlets from in-field irrigation channels and inter-field irrigation flows with 60–100% of the Cd and Zn loading associated with the first three fields in irrigation sequence. Rice grain Cd concentrations in the 524 fields sampled, ranged from 0.05 to 7.7 mg kg⁻¹. Over 90% of the rice grain samples collected contained Cd at concentrations exceeding the Codex Committee on Food Additives and Contaminants (CCFAC) draft Maximum Permissible Level for rice grain of 0.2 mg Cd kg⁻¹. In addition, as a function of demographic group, estimated Weekly Intake (WI) values ranged from 20 to 82 μg Cd per kg Body. This poses a significant public health risk to local communities. The results of this study suggest that an irrigation sequence-based field classification technique in combination with strategic soil and rice grain sampling and the estimation of WI values via rice intake alone may be a useful decision support tool to rapidly evaluate potential public health risks in irrigated rice-based agricultural systems receiving Cd contaminated irrigation water. In addition, the proposed technique will facilitate the cost effective strategic targeting of detailed epidemiological studies thus focusing resources to specific ‘high risk’ areas.     

COMPETING WATER USES IN THE SOUTHWESTERN UNITED STATES: VALUING DROUGHT DAMAGES1

ABSTRACT: Economic benefit functions of water resource use are estimated for all major offstream and instream uses of Colorado River water. Specific benefit estimates are developed for numerous agricultural regions, for municipal uses, and for cooling water in thermal energy generation. Economic benefits of hydropower generation are given, as are those for recreation on Colorado River reservoirs and on one free-flowing reach. Marginal and total benefit estimates for Colorado River water use are provided. The estimates presented here represent a synthesis of previous work, providing in total a comprehensive set of economic demand functions for competing uses of Colorado River water. Non-use values (e.g., benefits of preserving endangered species) are not estimated.     

REGIONAL ASSESSMENT OF NLEAP NO3-N LEACHING INDICES1

ABSTRACT: Nonpoint source ground water contamination by nitrate nitrogen (NO₃-N) leached from agricultural lands can be substantial and increase health risks to humans and animals. Accurate and rapid methods are needed to identify and map localities that have a high potential for contamination of shallow aquifers with NO₃-N leached from agriculture. Evaluation of Nitrate Leaching and Economic Analysis Package (NLEAP) indices and input variables across an irrigated agricultural area on an alluvial aquifer in Colorado indicated that all leaching indices tested were more strongly correlated with aquifer NO₃-N concentration than with aquifer N mass. Of the indices and variables tested, the NO₃-N Leached (NL) index was the NLEAP index most strongly associated with groundwater NO₃-N concentration (r² values from 0.37 to 0.39). NO₃-N concentration of the leachate was less well correlated with ground water NO₃-N concentration (r² values from 0.21 to 0.22). Stepwise regression analysis indicated that, although inorganic and organic/inorganic fertilizer scenarios had similar r² values, the Feedlot Indicator (proximity) variable was significant over and above the NO₃-N Leached index for the inorganic scenario. The analysis also showed that combination of either Movement Risk Index (MIRI) or NO₃-N concentration of the leachate with the NO₃-N Leached index leads to an improved regression, which provides insight into area-wide associations between agricultural activities and ground water NO₃-N concentration.     

A TRADE-OFF ANALYSIS OF ALTERNATIVE WATER USES1

ABSTRACT: In the western United States, hydropower and agriculture often cempete for surface waters. Since water markets are imperfect, allocations are often made through institutional arrangements and policy The purpose of this paper is to compare the gross water returns from agriculture with hydropower in terms of water use in Idaho. For the year 1986, returns from agriculture averaged $200 per acre-foot, and returns from hydropower averaged $8.00 per acre-foot.     

EFFECT OF SYSTEM LAYOUT ON SUBSURFACE DRAINAGE COST IN FLAT IRRIGATED LAND1

ABSTRACT: The economic feasibility of large-scale subsurface drainage projects in irrigated land is affected by construction costs. This study was conducted to evaluate the effect of two different types of subsurface drainage system layout on construction costs for a 1000 ha pilot area located in the Nile Delta of Egypt. The two types of layout studied were the conventional layout currently used in Egypt and the modified layout that was developed for reducing water losses from rice fields. When compared to the conventional layout, the modified layout resulted in a reduction of 6.74 percent in construction costs (714,464 US$ versus 766,142 US$). This cost reduction is explained by the need for lesser lengths of large diameter collector pipes with the modified layout, which results from the smaller drainage area of subsurface drainage systems (average 23.7 versus 30.8 ha). We have found that the cost of subsurface drainage can be minimized by reducing the area drained by each subsurface drainage system.