Laboratory Simulation Experiment On Sediment Effect And Influence Factors In Cabon Cycling

This study is a further research of the analysis of reclaimed water in the Chaobai River. Previous studies have proven that the main factors of the Chaobai River’s water quality change are the photosynthesis and denitrification, and studies have proved that sediment is an important part in the carbon cycling. in order to realize effects of the sediment in the carbon cycling.This research adopts to use the way of laboratory simulation to discuss the sediment effect and influence factors in the process of water quality change, according to the the conventional index detection, the measurement of gas flux and measurement of sediment reactions. The main results are as follows:1. Laboratory simulation experiment data shows that both of the organic matter in sediment and TOC in the water works as carbon source in the carbon cycling in a closed system, the quantity of them about 8:1. Sediment degradation including two ways, the aerobic degradation and the anaerobic degradation, the proportion of them is about 5:3, sediment degradation rate is about 26.72 mmol m-2d-1 in the closed system. The main product of carbon cycling is the carbon dioxide flux change which has nearly 71% of the total product. And the methane flux change has bout 22% of the total product, alkalinity increased has about 7% of the total product. Carbon dioxide released into the air, makes the CO2 flux in the closed systm increased.2. In the open system of the carbon cycling, the sediment organic matter is the only carbon source, sediment organic matter degradation rate tendency for 68.06 mmol m-2d-1.Sediment degradation is aerobic degradation, the degradation products is mainly carbon dioxide, accounting for 97.5% of the total product, secondary products include methane gas, TOC in water and bicarbonate increasing in water. methane gas flux has 1% of the total amount of product in the open system, the TOC increased in water is about 1% of the total product, water bicarbonate has about 0.5% of total product. Carbon dioxide released into the air, increased the CO2 flux of the environment.3. Closed experiment data analysis shows that the dominant factors of the pH change is the nutrient in the sediment. Nutrient consumption [H +] in the process ofdenitrification, which makes pH raising. The consumed [H +] mainly comes from the process of the carbon cycling, accounted for more than 99% of the total consumed is from the carbonic acid hydrolysis, which makes the concentration of [HCO3-] rises in water. And less than 1% of the consumed [H+] is from hydrolysis of the water molecules, which makes the pH increase.In a closed system, nutrients denitrifying consumes about 2 * 10-3 mol/L protons, water pH changed from 8.05 to 8.3. In open system, nutrients denitrifying consumes about 1 * 10-3 mol/L protons.