分类： 环境科学技术及资源科学技术 >> 环境科学技术基础学科 提交时间： 2023-12-20 合作期刊: 《干旱区科学》
摘要： Globally, groundwater contamination by nitrate is one of the most widespread environmental problems, particularly in arid and semiarid areas, which are characterized by low amounts of rainfall and groundwater recharge. The stable isotope composition of groundwater (2H-H2O and 18O-H2O) and dissolved nitrate (15N-NO3 and 18O-NO3) and factor analysis (FA) were applied to explore groundwater provenance, pollution, and chemistry evolution in the northwestern part of the Amman-Al Zarqa Basin, Jordan. In this study, we collected 23 samples from the Lower Ajloun aquifer in 2021, including 1 sample from a groundwater well and 22 samples from springs. These samples were tested for electrical conductivity, total dissolved solids, pH, temperature, dissolved oxygen, the concentration of major ions (Ca2+, Mg2+, Na+, K+, HCO3, Cl, SO42, and NO3), and the stable isotope composition of groundwater and dissolved nitrate. The results revealed that groundwater in the study area is mainly CaMgHCO3 type and can be classified as fresh water, hard water, and very hard water. The range and average concentration of NO3 were 3.5230.8 and 50.9 mg/L, respectively. Approximately 33% of the sampling points showed NO3 levels above the maximum allowable concentration of 50.0 mg/L set by the World Health Organization (WHO) guidelines for drinking water quality. The values of 18O-H2O and 2H-H2O showed that groundwater in the study area is part of the current water cycle, originating in the Mediterranean Sea, with significant evaporation, orographic, and amount effects. The values of the stable isotope composition of NO3 corresponded to 15N-NO3 and 18O-NO3 values produced by the nitrification process of manure or septic waste and soil NH4+. The FA performed on the hydrochemical parameters and isotope data resulted in three main factors, with Factor 1, Factor 2, and Factor 3, accounting for 50%, 21%, and 11% of the total variance, respectively. Factor 1 was considered human-induced factor, named pollution factor, whereas Factor 2, named conservative fingerprint factor, and Factor 3, named hardness factor, were considered natural factors. This study will help local researchers manage groundwater sustainably in the study area and other similar arid and semiarid areas in the world.
分类： 生物学 >> 植物学 >> 植物生态学和植物地理学 提交时间： 2016-05-04
摘要： In this article, the belowground and aboveground biomass production in bioenergy buffers and biogeochemical N removal processes along the soil–groundwater continuum was assessed. In a sandy loam soil with shallow groundwater, bioenergy buffers of miscanthus and willow (5 and 10 m wide) were planted along a ditch of an agricultural field (AF) located in the Po valley (Italy). Mineral N forms and dissolved organic C (DOC) were monitored monthly over an 18-month period in groundwater before and after the bioenergy buffers. Soil samples were measured for inorganic N, DOC, microbial biomass C (MBC) and N (MBN), and potential nitrate reductase activity (NRA). The results indicated that bioenergy buffers are able to efficiently remove from groundwater the incoming NO3-N (62% – 5 m and 80% – 10 m). NO3-N removal rate was higher when nitrate input from AF increased due to N fertilization. Willow performed better than miscanthus in terms of biomass production (17 Mg DM ha−1 yr−1), fine root biomass (5.3 Mg ha−1) and N removal via harvesting (73 kg N ha−1). The negative nonlinear relationship found between NO3-N and DOC along the soil–groundwater continuum from AF to bioenergy buffers indicates that DOC:NO3-N ratio is an important controlling factor for promoting denitrification in bioenergy buffers. Bioenergy buffers promoted soil microbial functioning as they stimulated plant–microbial linkages by increasing the easily available C sources for microorganisms (as DOC). First, willow and miscanthus promoted high rates of biological removal of nitrate (NRA) along the soil profile. Second, rhizosphere processes activated the soil microbial community leading to significant increases in MBC and microbial N immobilization. Herbaceous and woody bioenergy crops have been confirmed as providing good environmental performances when cultivated as bioenergy buffers by mitigating the disservices of agricultural activities such as groundwater N pollution.
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