ACIDIFICATION CAPACITY MODEL - FORMULATION AND APPLICATION

A theoretical computation approach and a classification method of two- reference-states for the acidification capacity of natural waters are developed after its definition, determination procedure and classifica tion methods are demonstrated. In the theoretical computation of acidi fication capacity, the alkalinity, pH, chemical oxygen demand and Al(I II) components of waters are chosen as the original parameters. The co ntribution of carbonate, dissolved organic matter, and soluble aluminu m to the acidification capacity is, respectively, emphasized. On the b asis of theory of aquatic chemistry and the aquatic status of Southwes t Area of China, the calibration value of methyl orange alkalinity to TIP alkalinity is calculated as 49 mu M. The CaCO3 water system which balances with CO2 in the atmosphere, and the water system which holds the critical pH and balances with CO2 in the atmosphere are considered as the reference state of the waters difficult to acidification and t he critical state of acidified water. The annual amount of acid deposi tion including precipitation and dry deposition is used as the referen ce criterion to classify the waters easy and difficult to acidificatio n. As a case study, this model is applied to the southwest area of Chi na, and some compatible results have been obtained. This model makes i t possible to estimate the acidification trend of natural waters in a large scale of area. (C) 1998 Elsevier Science Ltd. All rights reserve d.