Characteristics Of Accumulation And Biodegradation Of Paes By Potamogeton Crispus L. In Natural Waters

As important primary producers in aquatic ecosystem, submerged plants play a central role in the biogeochemical cycling of organic contaminants in water environment. Because of extensive use, phthalate esters (PAEs) have become the most general environmental pollutants in the world, and the water environment in our country has been severely polluted. Submerged plants can effectively control eutrophication, reduce inorganic and organic pollutant, the technology of PAEs ecological restoration by submerged plants has prospective application.Potamogeton crispus L. (P. crispus) is a typical submerged plant and plays an important role in the water ecological reconstruction. Five natural water samples (from Haihe River and two small landscape lakes) were selected to study the effect of water quality on physiological indicators (chlorophyll, soluble protein and nitrate reductase activity) of P. crispus; And the characteristics of biodegradation and accumulation of phthalate esters (PAEs) by P. crispus under sterile and non-sterilized conditions. Then the effect of water quality on accumulation and biodegradation of PAEs by P. crispu was to be analyzed.The results showed that dissolved oxygen and temperature between the water samples were the same under the experimental conditions, and pH was alkaline; There were small differences in phosphorus (P) characteristics, and particulate P and organic P were the main forms of P. While quite different existed in N forms; NO₃^--N was the dominant form in water from Haihe River, while NH4+-N was the most dominant N form in the water from the lakes. Under sterile condition P. crispus absorbed N obiviously, leading to TN decreasing by 53.9%, and the capacity of uptake NO₃^--N by P. crispus was greater than that of NH4+-N. P. crispus absorbed little P, but it could promote the conversion between different P forms. The physiological indicators of P. crispus were mainly affected by NO₃^--N. With increasing NO₃^--N content, the physiological activity increased. Higher NO₃^--N content in Haihe River facilitated the growth of P. crispus and its physiological activity.P. crispus removed PAEs from water by accumulation and degradation, and the removal process could be described by a first-order kinetic equation. Under sterile condition, P. crispus removed DBP and DEHP by 68.52% and 84.74% on average in Haihe water, and degradation rate constant (k) were 0.36×10-2 h-1 and 0.5×10-2 h-1. The removal percentage of DBP and DEHP from lakes water were 29.08% and 36.93% on average, and k were 0.086×10-2 h-1 and 0.09×10-2 h-1. Accumulation of DBP and DEHP by P. crispus accounted for 1.22% -7.41% and 4.31% -18.34% of the total removal from water samples. Therefore, biodegradation was the main way to remove PAEs in the presence of P. crispus.The average removal percentages of DBP and DEHP using P. crispus combined with microorganisms were 82.32% and 90.12% in Haihe water, 36.9% and 44.92% in lakes water; Comparison with the control experiments with microorganisms, the removal percentage of DBP and DEHP increased by 1.53% 16.71% and 3.22% 17.55% respectively, and the k of PAEs increased by 5.92% 45.91%, -53.16% 119.31% respectively. P. crispus played an important role in removing PAEs from natural water.The correlation analysis showed that k of PAEs by P. crispus with or without microorganisms was all significantly related to NO₃^--N content, especially for DEHP, indicating that NO₃^--N was a key factor to affect the accumulation and degradation of PAEs by P. crispus. Because of the nutrient competition between microorganisms and P. crispus, NO₃^--N content was the limiting factor to both the metabolism and degradation of PAEs.