| Natural water surface coatings can be defined as biofilm existing widely on the aquatic environment mediums consisting of metal oxides (e.g. manganese oxides, iron oxides and aluminum oxides etc.), organism and a small quantity of mineral from the viewpoint of environmental chemistry. The formation of surface coatings is correlative with the chemical composition of aquatic environment. Surfaces coatings are open dynamics systems in aquatic environments, and the components of surface coatings are at dynamic movement, in which various components could synthesize, accumulate, transform and degradation. Factors affecting the formation and growing of surface coatings include velocity of flow, types of mediums, the species and amount of micro-organism, components of organic and inorganic materials, geochemistry of freshwater, ambient light illumination and water temperature etc.The characteristic of surface coatings rests with high activity and abundant surface area for the adsorption to contaminants especially to the trace quantity metal and organic pollutions. Study of adsorption has important guidance to the heavy metal removing using biologic technology. Besides acting as the medium for studying the configuration, the removal and transfer regulation of heavy metals and organic pollutants, the surface coatings can also exhibit the accumulation, indication of pollutants and its adverse effect, such as the erosion of the underwater equipment of ship body and clean water system caused by microorganisms. Surface coatings have apparent anti-effect to antibiotics, pesticide and bactericide. The organic materials on surface coatings are one of the most important factors that can affect its adsorption characteristic. So it is a fundamental and essential step of the studying natural surface coatings to develop a rational method to quantify the organic materials of surface coatings.Natural surface coatings are developed in five waters-Nanhu Lake,Xinlicheng Reservoir, Yitonghe River, Yitonghe Pond and Jingyue Lake, and measured both the chemical oxygen demand (COD) and total organic carbon (TOC) to quantify the organic materials of surface coatings. Detailed contents include: (1) correlation analyses of COD and TOC on natural surface coatings in the same waters with different developing period (every 5 days); (2) correlation analyses of COD and TOC on natural surface coatings in the same waters with different depths (every 0.5 meters); (3) correlation analyses of COD and TOC on natural surface coatings in the same waters with different seasons (from May to October); (4) correlation analyses of COD and TOC on natural surface coatings in the same season(August 25th to 30th)with different waters. The experiment follows the USA standard method #5220 to survey the value of COD on surface coatings; while the TOC is surveyed by total organic carbon measurement(TOC-VCPH made in Shimazu corporation) containing SSM—5000 solid combustion equipment .From the derivation of theoretical value of [COD]/[TOC]=32/12≈2.67, it is known that COD and TOC have certain linear relationship. The relationship of COD and TOC on natural surface coatings has been studied using correlation analyses based on the data of COD and TOC gained from experiments. The conclusion is that COD and TOC have remarkable relativity with the change of time, depth, season in the same waters and the change of waters(r≥0.99,p=0.01). The regression equation of COD and TOC on unit area of carrying glass with the change of time, depth, season and waters is also gained. In addition, regression equation of COD and TOC on unit area of carrying glass has no remarkable difference in the same waters which is checked by comparison of two regression equations. Consequently, the research gets a uniform regression equation. COD =2.7462TOC+222.70; However in different waters, as the conditions which affect the formation and growing of surface coatings are different from each other, including the species and amount of micro-organism, temperature, sunlight, v...
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