地理信息学与地统计学：概述

Prediction of Reaeration and Deoxygenation Rate Constant in Selbe River, Mongolia: Dissolved Oxygen and BOD Assimilative Capacity of the River

Ariuntuya Tserendorj*, Bodigerel Lkhagvasuren , Usukhbayar Puntsagsuren , Gerelt-Od Dashdondog

In rivers, the processes of deoxygenation and reaeration play major roles in self-purification, particularly influenced by temperature changes. This study is the first to consider Mongolia's river's Dissolved Oxygen (DO) and Biochemical Oxygen Demand (BOD) assimilative capacity. The objective of the study was to determine the deoxygenation rate (k1) and the reaeration rate (k2) constants of the Selbe River, in Ulaanbaatar, Mongolia. The mean k1 was calculated using two models, namely the Thomas slope and firstorder function methods. The results showed that the first-order function model was more suitable for describing k1, which is 0.116 ± 0.012 and 0.266 ± 0.0281 respectively in 10 and e of logarithm base because the sampling standard deviation of the model we used is more reliable than the Thomas method. The mean k2 was estimated by 8 models out of 22 different available models. Jha’s model was more reasonable because it had the lowest sampling standard deviation compared with other models. Accordingly, the mean k2 in the Selbe River was found to be 3.41 ± 0.67 at 4.97 mean temperature of Celsius. As a result of using k1 and k2, there is 0.7 mg/L of mean critical oxygen deficit, 0.3 d of critical time and4.7 km of the longest distance using the purification model for steady-state at 20ºC because non-point pollution sources occurred in most sampling points. Additionally, considerations should include the trend towards stronger rainfall events, changes in land use density with an increasing number of pit latrines, variations in soil types and the presence of private wells, all of which are potential drivers of changes in water hygiene.