Research On The Concentration Distribution Characteristics, Sources Of Heavy Metals And Water Quality In Maoming City Groundwater

Underground water is one of the important resources for the development of cities. Maoming City, a newly developing medium industrial city started developing from 1959 and it’s mainly dependent on its petroleum and chemistry industry. Maoming City is one of the cities that mainly dependent on its underground water as water supply source, which means that the quality of the underground water directly affects the health of local citizens. This research has 19 monitoring sites counted by monitoring places from 2005 to 2012. We analyzed the water level, water temperature and twelfth kinds of main ions, nine kinds of content of the pollution elements simultaneously. We also utilized geochemical method to analyze the reason for forming the types of water quality and the relationship between geology and the concentration of heavy metals. Lastly, we relied on the PCA method to explore the inter relationship between heavy metals and the temporal and spatial distribution of heavy metals, thus finding out the source of heavy metals.The outcome indicated that the type of underground water in Maoming City can be divided into four basic types by how it’s established, which are the natural type like HCO3-Ca, the mine pollution type like SO4-Ca, the agriculture pollution type like NO3·HCO3-Ca and other mixed pollution type. The SO4-Ca type among these four basic types has the highest ratio of pollutant, and the high content of Pb, Mn are the outstanding representatives. Meanwhile, the affecting factors of pollutant can at least be listed six different reasons. But if classifying the factors by how the pollutant was established, there are four factors can be listed. The natural ones are the local geographical conditions and its Geological environment like the dissolution of mines and sedimentary rocks. The man-made ones include the industrial pollution, agriculture pollution and the daily lives of human beings like the open pit mining field, south dump wastewater, oil refineries, fertilizer and etc.. The remains are some mixed pollution factors. As time and season changes, the water type and the pollutant will change, too. Additionally, it is the SO4-Ca type that predominates most in the monitoring sites in dry season while the type varied in rainy season. On one hand, J9 and J12 remain SO4-Ca type and always have a high ratio of pollutant. On the other hand, the Maoming City petroleum industry was stopped during 2005 to 2012, thus alleviating the pollutant concentration in Maoming City in dry season but increasing tendency of the underground water pollutant concentration because of the industrial pollution in 2012. In fact, the local petroleum industry was transferred into the construction of some chemical industry like oil refinery and ethylene plant. Moreover, the pollutant will permeate into underground water by raining, thus causing the pollutant concentration gradually increase in dry and rainy season. Compared 2005 with 2012, groundwater quality and concentration of heavy metal spatial and seasonal variations confirmed that the groundwater pollution in the region by underground oil exploitation industry type gradually transformed into surface industrialization type pollution.