【作者】 贺秋芳；

【导师】 袁道先；

【作者基本信息】 西南大学 ， 自然地理学， 2009， 博士

【摘要】 约占中国国土面积1/3的岩溶区蕴藏着大约1/4的地下水资源,岩溶地下水是中国西南岩溶区的重要水源。但是,由于岩溶系统的脆弱性,现阶段工业、农业、矿业以及人类生活污水对岩溶地下水造成的污染,使得中国岩溶区的地下水资源已经全面告急。尤其农业生产中使用无机化肥和有机肥等造成的地下水氮污染更加广泛,影响更加深远。了解岩溶系统中氮素的迁移转化途径,有利于减少和控制地下水污染,保护地下水环境提供,有利于解决岩溶地区人畜饮水问题,维持岩溶区人民生活安定和社会稳定。关于土壤和地下水中的“三氮”污染以及氮循环过程的机理研究已有较多报道。对北方旱地、潮棕壤以及水稻田系统中“三氮”的迁移转化过程已经有很详细的研究,并且已经建立了数值模拟模型对土壤和地下水中氮素的输入输出过程进行控制,但是对岩溶系统中的氮循环研究报道有限。本文以岩溶较为发育的青木关地下河流域为例,研究其土壤和地下水的氮循环过程,为石漠化治理过程中的氮素管理,石漠化地区地下水水质和水源的保护提供理论基础。本文通过对青木关岩溶槽谷区10种不同土地利用方式的土壤采集土壤60个,分析土壤样品中的14种元素和微生物指标,应用因子分析法对土壤中氮素转化的主要影响因子进行归纳。然后,选择具有代表意义的两种典型土地利用方式,每15cm采集土壤样品至60cm以下,检测土壤的营养元素、“三氮”以及微生物含量,利用拟合曲线分析土壤中氮素的垂直迁移转化过程,并分析相关微生物在其中的作用。在线监测地下水出口和入口的流量以及研究区的降雨量,至少每月一次采集地下河入口和出口的水样,监测地下水中氮素以及其它无机离子的年度变化动态,结合地下河示踪试验结果,分析地下水中的氮素迁移过程。分析地下水水样中的微生物含量,结合样品中的“三氮”含量,使用相关分析了解微生物与“三氮”之间的关系,分析示踪地下河岩溶系统中土壤—地下水氮的补给途径,研究地下水微生物示踪研下河的地表径流补给,出口处微生物与硝态氮之间没有相关关系,类似落水洞处;旱季时地下水主要是经过岩溶裂隙进入土壤渗透水补给的,出口处硝态氮与微生物之间存在较好的相关关系。地下水中氮素的补给途径与水的补给途径相同:旱季土壤渗透水中硝态氮高达16mg/L,与地下水中的含量相近;雨季主要从落水洞补给。以上研究结果表明,由于岩溶系统中硝态氮与地下水一并漏失,而非如非岩溶区中硝态氮在土壤中积累,需要与非岩溶区区别对待;微生物对地下水及氮素的示踪实验表明雨季和旱季它们的补给途径不同;也证明微生物示踪在岩溶地下水研究中具有可行性。但是对于岩溶系统氮循环和微生物示踪的研究都不深入,在将来的研究中,可在不同岩溶系统中研究氮循环过程,了解不同水文地质背景下土壤氮循环的过程和机理,并建立相关的数值模拟模型,以控制系统中氮素的输入和输出;对于微生物示踪研究,需要应用更多先进的技术如基因组学方法,全面了解地下水中微生物的特异性,用于更细致示踪实验的进行。更多还原

【Abstract】 Karst groundwater pollution in China has been so serious that the usable quantities of groundwater resources are very little. Thus, protection of karst groundwater resources couldn’t be delayed any more. In the karst area, groundwater is an important water resource of local people life and agriculture, but nitrogen pollution caused by fertilization is very common. Therefore, reducing nitrogen pollution in karst groundwater is very important to ensure the people’s livelihood, and social harmony and stability. The situation of "3-N" pollution and nitrogen cycling process in soil and groundwater were reported a lot, but most of them were focus on non-karst area and few studies with regard to karst area have been documented.The contaminations transferring has its unique characters for the special hydrogeology background in karst area. In the transferring processes, contaminations couldn’t be absorbed or degraded, which will transfer to a place far away in short time after they leaching into ground river and discharging to non-karst area. Thus the accumulation of nitrogen pollution isn’t of great notability in soil and groundwater in karst area, but the occurrence of nitrogen pollution may be even worse. In this paper, a case of a typical karst valley in Qingmu Guan, Chongqing, has been employed to investigate the nitrogen transferring and transforming processes in soil and groundwater, and give some suggestion for nitrogen management in management of rocky desertification and protection of groundwater and drinking water sources.Soil elements and microorganisms have been measured in ten kinds of soil samples within different land use, and also principal factor analysis was used to conclude the main affecting factor of soil nitrogen cycling. Two of the ten soil samples, representation of typical land uses, were specially sampled to analyze the characteristics of nitrogen transferring and transforming in vertical been concluded. First, in the rainy season, protection zones and adaptations in land use practices around the swallow holes and sinking streams, and within their hydrologic catchments, need special attention and must help to reduce microbiological contaminations of spring. Second, in the dry season, protection zones and adaptations in land use practices should be better attention in the whole watershed, which including control the use of pesticides and fertilizers and sewage irrigation. Third. if possible, using soil situ ecological repairing to degrade contaminations and reduce contaminations transferring to underground flows.Generally, the nitrogen cycling in karst area is different from that in non-karst area, and need to pay more attention. In the future, some researches should be done in different karst system to find out the nitrogen cycling mechanisms in different hydrogeology background. Numerical simulation model about nitrogen cycling in karst area should be established to help reduce the ground water nitrogen pollution in rocky desertification management projects. Otherwise, the preliminary study of soil microorganism tracer test shows the character of soil microorganism community is useful in groundwater tracer test, but it needs more research in detail, such as the detail of microorganism community composition and characteristic in different soil, which more advanced technology should participates.更多还原