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排序方式： 共有1634条查询结果，搜索用时 0 毫秒
1.
Mrklas Ole Chu Angus Lunn Stuart Bentley Laurence R. 《Water, air, and soil pollution》2004,159(1):249-263
The release of alkanolamines and glycols into the subsurface soils poses a potential hazard to the environment through impacted soil and groundwater. This study investigated aerobic and anaerobic biodegradability of monoethanolamine (MEA), ethylene glycol (MEG) and triethylene glycol (TEG). Significant levels of MEA (31 000 mg/kg), MEG (500 mg/kg) and TEG (2100 mg/kg) were successfully aerobically biodegraded in bioreactors. The aerobic slurry experiments suggested initial phosphate (P) limitation, as biodegradation rates increased by one order of magnitude after phosphate addition. Anaerobic decay of MEA, MEG and TEG was unaffected by P-addition. MEA, MEG and TEG degradation products such as acetate, ethanol and ammonium at about 75 000 mg/kg, 8100 mg/kg and 8800 mg/kg degraded completely and did not prevent aerobic biodegradation. This study confirms proposed biodegradation pathways of MEA, MEG, TEG and their breakdown products in natural soil and groundwater using indigenous microbes. Levels of contamination studied here are significantly higher than previously reported. 相似文献
2.
针对山西省运城地区因地下水超采而产生的地面下沉、地裂、农用机井报废等一系列环境问题，通过计算分析，提出了一个既能满足农业发展对水的需求，又能维持地下水资源环境平衡的地下水可开采量，并就实施限量开采地下水的途径、技术措施、管理机制、水价体系及政策保障等进行了综合分析与阐述。 相似文献
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河川基流分割法在山丘区地下水资源量评价中的运用 总被引：1，自引：0，他引：1
山丘区河川基流分割方法很多，采用不同方法的分割成果不尽相同。在地下水资源评价中，根据云南省自然地理独特，气候复杂多样，降水量丰沛，洪水频繁，河川径流过程线普遍呈连续多峰型的特性，寻求一种既能满足水资源综合规划要求，又符合云南实际分割河川基流量的方法，是地下水资源评价中的重要内容。采用适宜水均衡法和直线斜割法的径流资料分割河川基流量，求出两种方法之间的换算系数，修正水均衡法的分割成果，一是达到了以直线斜割法统一分割河川基流量的目的；二是提高了山丘区地下水资源量评价的精度，为探索山丘区地下水资源量及时空分布规律提供技术支撑。 相似文献
5.
Poor on‐farm irrigation practices and rising groundwater table depths are the major reasons for low cotton yields in the Sardarya province of Uzbekistan. To ensure sustainability of cotton production in the area, precise calculations of irrigation requirements are needed to optimize crop yields and to keep groundwater table depth below the root zone to avoid soil salinization. To determine optimal groundwater table depth and irrigation amounts for the Sardarya province of Uzbekistan, the Soil–Water–Atmosphere–Plant (SWAP) model was used. SWAP was calibrated and validated using measured data from an experimental cotton field during the agricultural year of 2006 and 2007. The calibrated SWAP model was then used to simulate optimal groundwater table depth and irrigation amounts. The simulation results show that for the existing conditions in the study area, a groundwater table depth of approximately 200 cm together with an irrigation application of 2500 m3 ha−1 will be the most appropriate combination for optimal cotton yields (≈ 3.0 t ha−1). However, to achieve maximum potential yields of cotton (5–6 t ha−1), leaching of excessive salts from the root zone through freshwater application would be imperative. This would require rehabilitation of the existing drainage network in the area. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
6.
The relationship between physical hydrodynamic processes and nutrients dynamics was investigated in Mida creek, a groundwater influenced mangrovefringed creek in Kenya between March 1996 and May 1997. The research involved spot and timeseries measurement of nitrate–nitrite, ammonia, silicates, phosphates, salinity, temperature, sealevel as well as tidal currents at seven stations located in the front, middle and backwater zones of the creek. Groundwater level as well as total dissolved solids' concentration, salinity, temperature and nutrients' concentration were also measured once every month in shallow wells (watertable<5m) located in the upper region of the creek. Results of the study show that nutrient concentrations vary with the tide and that, though there is no river drainage, they are of the same magnitude as in mangrove creeks with substantial river runoff. The peak concentrations of NH
4
+
–N (5.45M), NO
2
–NO
3
(5.63M), PO
4
3–
–P (0.58M) and SiO
3
2–
–Si (81.36M) in the creek occurred during flood tide, 2–3h before high waters. The (NO
2
–
+ NO
3
–
)–N concentrations declined rapidly during ebb tide, reaching the minimum levels during low water. Contribution of groundwater seepage to the net nutrients flux (particularly on nitrite–nitrates) is largest in dry seasons. The study shows that groundwater outflow sustains the mangroves during periods of severe salinity stress and nutrients deficiency in dry seasons. This is essentially by limiting salinity increase and by boosting nutrient supply in dry seasons. 相似文献
7.
A. B. Dixon 《Land Degradation u0026amp; Development》2002,13(1):17-31
Wetlands are critical resources in the highlands of southwest Ethiopia, where they perform numerous environmental functions and provide a range of benefits for local communities. In recent years, however, an increase in the drainage and cultivation of these areas and reports of wetland degradation have raised concerns over the sustainability of wetland agriculture. This paper presents the results of a study in which groundwater levels were monitored in a series of wetlands undergoing different stages of drainage and cultivation, to establish the hydrological changes taking place as a consequence. The results suggest that drainage and cultivation induce extreme spatial and temporal variations in the wetland watertable. This is linked in part to structural and chemical changes in the wetland soil which affect hydraulic conductivity. Statistical analysis of this variability revealed the existence of wetland subunits, exhibiting specific hydrological behaviour, which may reflect the influence of current and past land use. Although degradation of these wetlands does occur, many wetland users are aware of their impacts and have developed practices which, in most cases, prevent overdrainage to the extent that the wetlands cannot support agriculture. In this respect, it is argued that wetland use remains hydrologically sustainable, although this ultimately rests upon the ability of communities to continue to develop and apply their indigenous wetland management practices under rapidly changing environmental, socio‐economic and political conditions. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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Alice Tyson Biju George Lu Aye Bandara Nawarathna Hector Malano 《Irrigation and Drainage》2012,61(4):542-554
Changes in energy subsidies for Indian agriculture and the introduction of a carbon tax in Australia have the potential to impact on energy use practices in groundwater‐irrigated agriculture in both countries. A general framework for the accounting of life cycle greenhouse gas emissions and life cycle energy consumption from groundwater‐irrigated agriculture was developed using life cycle and supply chain analyses to examine the contributing aspects of groundwater irrigation to total associated greenhouse gas emissions and energy use. The framework then formed the basis of a greenhouse gas emission and energy accounting model that was simulated for the groundwater‐ dependent agricultural areas of the Musi catchment in India and the south‐east region of South Australia. The region in South Australia was found to be emitting around twice the greenhouse gas of the Indian region per unit volume of water delivered, while emissions associated with operating electricity powered water pumps contributed more than 99.8% of modelled emissions in the south‐east of South Australia and over 99.1% of emissions in the Musi catchment. Diesel powered water pump irrigation systems emitted the least total amount of greenhouse gas emissions per unit volume of water supplied, compared to grid electricity and diesel generator powered submersible water pump options. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献