亚热带红壤丘陵区浅层地下水氮淋失特征研究

土壤养分累积引起的氮素(N)淋失是导致农区地下水污染的重要原因,也是农业面源污染的重要形式.本文以湖南省长沙县典型亚热带红壤丘陵流域为研究对象,通过连续定位观测,研究了林地、稻田、菜地和茶园4种代表性土地利用类型浅层(130~150 cm)地下水中N浓度的逐月动态变化特征.连续3年(2010—2013年)的观测结果表明:4种土地利用类型下浅层地下水总氮(TN)平均浓度差异显著(p0.05),其中,林地最低(0.85 mg·L-1),茶园最高(7.64 mg·L-1);从N的形态构成来看,林地、菜地和茶园浅层地下水中N形态以硝态氮(NO-3-N)为主,分别占TN的46.7%、70.2%和72.8%,而稻田浅层地下水N形态则以铵态氮(NH+4-N)为主,占TN 43.5%,表明土壤淹水条件是影响地下水N淋失形态的关键因子.地下水各形态N浓度的动态变化在不同土地利用下也迥然不同:林地地下水各形态N的含量低、变幅小,而稻田、菜地和茶园地下水N浓度变幅较大;采用单因子方法对不同土地利用下地下水的水质进行评价,结果表明:研究区浅层地下水中TN和NO-3-N无显著污染,NH+4-N污染较为严重,而综合指数法(F值法)进一步表明研究区浅层地下水污染主要出现在稻田和茶园,因此,控制稻田和茶园N肥的施用量是预防亚热带红壤丘陵区地下水N污染的关键.     

亚热带丘陵小流域土壤有效磷空间变异与淋失风险研究

肥料过施导致的土壤磷素累积和淋失是农业面源污染的重要方面.以湖南省长沙县金井镇脱甲河小流域(52 km2)为研究区,采用高密度布点采样、Arc GIS软件和属性相似反距离加权插值法研究了亚热带丘陵小流域表层(0~20 cm)土壤有效磷(Olsen-P)含量(以P计,下同)的空间分布特征与磷素的淋失风险.结果表明,菜地、果园、稻田和茶园土壤Olsen-P平均含量为62.0、16.1、14.4和13.7 mg·kg-1,是林地(平均含量为2.36 mg·kg-1)的5.8~26.3倍.5个土地利用类型土壤Olsen-P含量均具有高等变异水平和中等程度的空间自相关性(块基比C0/(C0+C)=50%),这与区内地形地貌、土壤母质、人工施肥等具有密切关系.根据土壤0.01 mol·L-1Ca Cl2浸提态P和Olsen-P的非线性关系可确定区内红壤和水稻土P的淋失风险临界值分别为69.97和98.40 mg·kg-1,并据此对脱甲河小流域土壤磷素淋失的风险进行了定量评价,结果表明旱地土壤具有明显较高的淋失风险,其中中等以上的比例占36.4%,而稻田土壤仅有0.2%,为中等以上淋失风险.因此,控制旱地(尤其是菜地)磷肥的投入是降低亚热带丘陵小流域土壤P淋失风险和减轻农业面源污染的关键.     

A Multi-Years Analysis of the Energy Balance,Green Gas Emissions,and Production Costs of First and Second Generation Bioethanol

Contemporary reports on the energy and environmental benefits of bioethanol have suggested that the cellulosic ethanol is significantly more efficient. To understand the development potential of energy crops in Taiwan, the present study has assessed the resources and cost inputs for the planning, harvesting, transporting, and storing procedures of the first generation energy crops during 2007–2010 with the perspective of LCA. In addition, a field investigation focusing on rice straw, the largest agricultural waste in Taiwan, has been conducted since 2010 to obtain fundamental data.This study further analyzes the first and second-generation feedstocks from the perspective of LCA based on field investigated data. Taiwan has not yet established an ethanol plant; therefore, this study established production data by simulating the production efficiency of an economical scale using parameters obtained through production trials, and proposed an evaluation model for the energy input, GHG, and production costs of bioethanol in Taiwan. The results of this study were cross-compared with foreign literature to explore the development potential of bioethanol in Taiwan. The results indicate that based on the current cellulosic ethanol technology in Taiwan, regarding the energy balance, GHG, and production costs, is less efficient than that of the first generation bioethanol.     

GIS-based analysis of population exposure to PM2.5 air pollution—A case study of Beijing

PM_(2.5), formally defined as particulate matter with diameter less than 2.5 μm, is one of most harmful air pollutants threatening human health. Numerous epidemiological studies have shown that both short-term and long-term exposures to PM_(2.5) are strongly linked with respiratory diseases. In this study, various types of spatio-temporal data were collected and used to estimate the spatio-temporal variation of PM_(2.5) exposure in Beijing in 2014. The seasonal and daily variation of the population-weighted exposure level(PWEL) in 2014 was estimated and compared. The results show that the population exposure to ambient air pollution differs significantly in the four seasons, and the exposure levels in winter and spring are notably higher than the other seasons; the exposure level changes greatly from North to South, and each sub-district maintains similarity to neighboring sub-districts.     

Preparing porous Cu/Pd electrode on nickel foam using hydrogen bubbles dynamic template for high-efficiency and high-stability removal of nitrate from water

Environmental Science and Pollution Research - Electrochemical reduction is a promising technology to remove nitrate from water. The metallic composition and geometry of electrodes usually dominate...