| Every year, a great amount of organic compounds is released into urface water body via wastewater discharge, rainfall runoff and waste leaching,which is biodegraded into CO2 by microorganisms. Also, the increasing CO2 in the atmosphere caused more CO2 solve in water. The increasing of the CO2 concentraion in surface water moving the balance towards carbonate led to increased alkalinity in surface water. Previous research concluded that HCO3- is the main inorganic salt in slightly alkaline condition(Ph 8~9). Recent research shows that, besides CO2,HCO3- can also act as inorganic carbon source for some algae, and Microcystis aeruginosa is one of the algae that use HCO3- as inorganic carbon source. Currently in China,the Microcystis aeruginosa have absolute predominance in occurrence and quantity in most of the eutrophic lakes.This research used index of basicity to indicate the concentration variation of inorganic carbon, by using method of experiment and simulated water column to study the effect of concentraion of inorganic carbon on the growth and distruibution of Microcystis aeruginosa in natural lake water of Beijing, to provide the theoretical basis for the study about the effects of inorganic carbon in water on growth of Microcystis aeruginosa. The results of this research can provide theoretical support for controlling the eutrophication of beijing lake cased by increased CO2 in atmosphere. The main research results:(1) The effects of inorganic carbon on the growth of Microcystis aeruginosa: Microcystis aeruginosa could use the bicarbonate as inorganic carbon source for photosynthesis directly or indirectly in the different medium containing.The different of inorganic carbon can impact the growth of algae,and the most suitable inorganic carbon concentration is about 2.4~2.83mmol/L in this study. Higher or lower than the concentration, the growth of algae will tend to decrease. But in general, lower is more suitable for the growth of algae than increasing the concentration of inorganic carbon. With the growth of algae, the p H of water will increas gradually, and the components of alkalinity will also begin to convert. The algal biomass and the concentration of inorganic carbon can affect the mass transfer of CO2 from the atmosphere into the water. The change of inorganic carbon will affect the utilization of Microcystis aeruginosa to P, N in the water.(2) The comparison the effects of inorganic carbon on algae growth under different nutrient levels: the growth curve of Microcystis aeruginosa had the similar tendency in two kinds of nutrition level. But if the concentration of water nutrient is increased, each of the algae growth rate and maximum cell density will be higher.In the hyper eutrophic leve, the utilization of inorganic carbon for single Microcystis aeruginosa is reduced, and the utilization of nitrogen and phosphorus is increased. The results show that the utilization of nutrient by algae can influence each other.(3) The effects of inorganic carbon on the distribution of Microcystis aeruginosa: Each group of experimental system are obvious stratification.The upper strata of experimental column presents the best growth,and the lower strata appears the weakest growth. When the inorganic carbon changes from 1.64mmol/L to 6.38mmol/L, the superstratum’s algal density accounted for the entire experiment column decrease from 39.11% to36.75%, and the proportion of mesosphere’s algae density is similar. But the substratum’s algal density accounted for the entire experiment column increase from 28.71% to 31.33%.Compared with the blank group, the superstratum’s average p H is higher than the other two layers in the experimental group, and the gap between each layer is more obvious in the experimental group with 2.94mmol/L inorganic carbon. With the increase of inorganic carbon’s concentration, the utilization rate of inorganic carbon is reduced in each layer of each group. At the same time, the utilization rate of inorganic carbon for algae is decreased from the top to the bottom of each group. The change of total nitrogen and total phosphorus are similar. Compared with the control group, the utilization gap of total nitrogen between each layer has a narrowing trend in the experimental group,and the total phosphorus is same. |
PDF Full Text Request