A tentative discussion on nitrite, nitrate and ammonia (NNA) pollution of groundwater in typical urbanized areas of Guangzhou City

Abstract： In the urbanization process of Guangzhou, which is characterized by highly centered economy and fast utilization of resources, groundwater environment has been influenced severely. High content of NO-2 and NH+4 in groundwater is concentrated in the city center, and samples with quota-exceeding NO-3 is distributed around the city and hilly areas, besides in the downtown area. Groundwater contaminations caused by human activities are complex. There have been various causes for nitrite, nitrate and ammonia (NNA) pollutions of the groundwater, and the human activities such as domestic, industrial and agricultural activities have played the dominant role. In addition, the NNA contamination is also related to such factors as stratigraphic sedimentary features in the plain area and the formation and modes of occurrence of groundwater. The nitrogen distribution in Guangzhou groundwater environment is affected significantly by hydrogeological conditions and hydrogeochemical factors, such as redox environment, lithology of the vadose zone, recharge, runoff and discharge conditions, content of Fe and Mn in water and soil, and the degree of acidification.