VARIABLE DISCHARGE TYPE CURVE SOLUTIONS FOR CONFINED AQUIFERS1

ABSTRACT: Almost all of the existing solutions of aquifer test analysis assume constant discharge rate boundary conditions. In many actual pumping tests, constant discharge cannot be maintained. This paper presents a general solution for an aquifer test with variable discharge. The exact solution of drawdown distribution around an infinitesimally small diameter well in a uniform, horizontal, extensive, homogeneous, and isotropic confined aquifer is presented when the discharge changes with time during the aquifer test period. A general equation for the type curves resulting from any discharge variability is given, and its application for the exponential changes is presented in detail. A simple straight line procedure is proposed for field applications by considering late time drawdown data. The consideration of constant discharge leads to overestimation of transmissivity but storativity is underestimated. Practical application of the discharge variability is illustrated by a field example.     

贵州喀斯特生态旅游可持续发展研究

介绍了贵州喀斯特生态旅游发展的现状，从自然条件和社会条件的角度分析了生态旅游的潜力。论述了可持续发展中存在的主要问题，提出了发展贵州喀斯特生态旅游的构想。     

中国土地利用和土地覆被变化研究进展

受国际社会影响，中国加强了土地利用／覆盖变化研究的进程，在众多领域取得了瞩目的成就，主要包括动态监测、遥感分类和制图、LUCC驱动力和区域LUCC模型、环境效应等方面，但中国LUCC研究也存在很多突出的问题，包括跨学科、时空尺度、理论体系完善、研究方法、与全球和区域环境变化及可持续发展之间的关系等。为促进中国土地利用／覆盖变化研究的持续、健康发展，提出对中国LUCC研究的建议和展望包括建立LUCC理论体系，深入掌握LUCC动态研究的手段和方法，形成与中国国情密切结合的土地利用和覆被变化综合模型，转变研究重点，更加清晰地认识和把握LUCC有关的可持续发展问题，加强土地利用变化与生态安全机制的研究等。     

Comparison of drinking water,raw rice and cooking of rice as arsenic exposure routes in three contrasting areas of West Bengal,India

Remediation aimed at reducing human exposure to groundwater arsenic in West Bengal, one of the regions most impacted by this environmental hazard, are currently largely focussed on reducing arsenic in drinking water. Rice and cooking of rice, however, have also been identified as important or potentially important exposure routes. Quantifying the relative importance of these exposure routes is critically required to inform the prioritisation and selection of remediation strategies. The aim of our study, therefore, was to determine the relative contributions of drinking water, rice and cooking of rice to human exposure in three contrasting areas of West Bengal with different overall levels of exposure to arsenic, viz. high (Bhawangola-I Block, Murshidibad District), moderate (Chakdha Block, Nadia District) and low (Khejuri-I Block, Midnapur District). Arsenic exposure from water was highly variable, median exposures being 0.02 μg/kg/d (Midnapur), 0.77 μg/kg/d (Nadia) and 2.03 μg/kg/d (Murshidabad). In contrast arsenic exposure from cooked rice was relatively uniform, with median exposures being 0.30 μg/kg/d (Midnapur), 0.50 μg/kg/d (Nadia) and 0.84 μg/kg/d (Murshidabad). Cooking rice typically resulted in arsenic exposures of lower magnitude, indeed in Midnapur, median exposure from cooking was slightly negative. Water was the dominant route of exposure in Murshidabad, both water and rice were major exposure routes in Nadia, whereas rice was the dominant exposure route in Midnapur. Notwithstanding the differences in balance of exposure routes, median excess lifetime cancer risk for all the blocks were found to exceed the USEPA regulatory threshold target cancer risk level of 10⁻⁴–10⁻⁶. The difference in balance of exposure routes indicate a difference in balance of remediation approaches in the three districts.     

Effects of 2,4-dichlorophenoxy acetic acid dimethyl amine salt on dental hard tissue formation in rats

2,4-Dichlorophenoxy acetic acid dimethyl amine salt (2,4-D DMA), as one of the phenoxy acids, is used as a herbicide mainly against broad-leaf weeds in cereal crops, sugar cane, and on turf, pasture, and non-crop land. Some formulations of 2,4-D may be contaminated with dioxins. Recently, it has been shown that chlorinated organic compounds, dioxins, and furans are present in mother's milk and may cause developmental defects in children's teeth. Therefore, we aimed to evaluate the effects of 2,4-D DMA on odontogenesis in rats. 2,4-D DMA was given orally combined with rat food to pregnant albino rats. Each group consisted of two pregnant rats and, 0 (control, group A), 25 ppm (group B), 50 ppm (group C), and 100 ppm (group D) 2,4-D DMA was given to each pregnant rat as daily intake. 2,4-D DMA affected young rat's dental development and dose-related findings were found in experimental groups. The odontoblast layer was irregular and globular dentin formation was present in Groups B, C, and D but not in the control group. Thickness of enamel decreased in Groups C and D. The results of the study have shown that 2,4-D DMA could disturb dental development in rats even in relatively low doses. It is concluded that environmental contaminants such as chlorinated organic pesticides may play an important role in infant's dental development when taken via mother's milk.     

The effects of compost prepared from waste material of banana on the growth, yield and quality properties of banana plants

Three doses (15-30-45 kg plant(-1)) of the compost prepared from the clone of Dwarf cavendish banana were compared with farmyard manure (50 kg plant(-1)), mineral fertilizers (180 g N+ 150 g P +335 g K plant(-1)) and farmyard manure+ mineral fertilizers (25 kg FM+ 180 g N+ 150 g P +335 g K plant(-1)) which determined positive effects on the growth, yield and fruit quality characteristics of banana plants. The banana plants were grown under a heated glasshouse and in a soil with physical and chemical properties are suitable for banana growing. The contents of N, P, K and Mg in compost and in farmyard manure were found to be similar. Farmyard manure, farmyard manure + mineral fertilizers and 45 kg plant(-1) of compost increased growth, yield and fruit quality characteristics. According to obtained results, 45 kg plant(-1) of compost was determined more suitable in terms of economical production and organic farming than the other fertilizer types.     

Thin-layer fine-sand capping of polluted sediments decreases nutrients in overlying water of Wuhan Donghu Lake in China

Environmental Science and Pollution Research - Capping water body sediments with a thin layer of sand is an effective technique to decrease nutrient concentrations in the water column and...     

昆明市清水海水源保护区生态补偿机制探讨

就昆明市清水海水源区生态补偿机制进行探讨,以期为生态补偿机制的建立提供借鉴。生态补偿理论结合清水海水源区实际分析。补偿主体是国家、受水区的企业和居民,客体是水资源和生态环境的保护者,以及牺牲发展机会的企业和居民;补偿标准以费用分析法计算,包括水资源保护、水源林建设和管理等方面的投入;补偿方式近期以输血型和造血型补偿结合,远期逐步向生态造血型补偿转变;优先补偿效率高的污染防治措施、退耕还林和测土配方,其次为产业结构调整和水资源管理;补偿时限结合补偿取得的成效、水源区生态产业发展和生态质量状况来确定;补偿资金以政府财政为主、市场为辅。结果表明:应结合清水海的实际,确定生态补偿的主客体、方式、标准和时限,建立生态补偿的保障机制,加强对补偿资金的监管。进一步开展定量化研究,完善清水海水源区生态补偿基础研究,促进生态补偿机制的建立。     

不同氮源对2种微藻生长及总脂含量的影响

采用一次培养的方式研究硝态氮（NaNO3）、氨态氮（NH4Cl）、有机氮（尿素）及硝铵混合氮（NH4NO3）（氮浓度17.6 mmol.L-1）对新分离的两株热带淡水微藻——网状空星藻Coelastrum reticulatum及栅藻Scenedesums sp.生长情况及总脂含量的影响。结果表明,2株微藻在不同氮源影响下生长状况不同,并且造成最终的干质量、总脂含量也有较为明显的差异。2种藻添加NaNO3和NH4Cl情况下分别获得了最高的生物量（（0.72±0.08）g.L-1和（0.80±0.03）g.L-1）和最高总脂含量（（38.35±1.32）%和（30.24±3.13）%）。最终二者在添加NaNO3的情况下单位体积总脂产量最高,分别为199.26 mg.L-1和190.76 mg.L-1,均可作为生物柴油的良好来源。