Characteristics And Influencing Factors Of Bioavailability Of Dissolved Organic Carbon And Nitrogen In Lakes In Wuhan

As the dissolved organic fraction in natural lake, dissolved organic matter (DOM) effects the morphology, toxicity, geochemical behavior of inorganic and organic pollutants, material and energy circulation in lake ecosystem. Since the lake eutrophication, discussion about the coupling between N and C is becoming an important significance.In this paper, six lakes in Wuhan-Lake Nan, Lake Dong, Lake MoShui, Lake Sha, Lake Yue, Lake YeZhi were sampled every month from April to October in2012. The influence on bioavailability of DOC and DON were studied. The seasonal variation and correlation of DOC and DON, and influencing factors were discussed. Looking forward to deepening understanding the transition and transformation of DOM in lake, and provide theoretical foundation for lake eutrophication management. The followings summarize the results from this study:(1) During studying period, Lake Dong, Lake MoShui, Lake Sha, Lake YeZhi have the same seasonal characteristics of chlorophyll a which higher in spring than in summer and autumn. The season characteristics of COD variation were same which higher in spring than in summer and autumn in Lake Nan, Lake Dong, Lake MoShui. The concentration of TN is high in summer in all lakes while the variation of TP had no significant difference in lakes except Lake Yue. It can see that N pollution is serious in Lake Dong, Lake Yue, N and P pollution is serious in other four lakes.(2) Both DOC and DON have the same seasonal characteristics of higher concentration in summer. There’s tight coupling between DOC and DON in Lake Dong, Lake MoShui, Lake Sha, Lake Yue. The content of chlorophyll a and COD don’t have correlation with DOC and DON, indicates that chlorophyll a and COD are not the main influence factors causing the variation of DOC and DON. While the variation of TN and TP has the same seasonal characteristics with DOC and DON.There is tight coupling between the seasonal characteristics of bioavailability of DOC and DON. And the correlation of bioavailability of DON and DIN is intense, indicates that the coupling between C and N is tight in city lakes.(3) During long time intubation, bacteria can uptake DOC and DON simultaneously, and different nutrients addition can part promote the bioavailability of DOC and DON. Lake Nan:BDOC> BDON, Lake Dong:BDOC<BDON. It is comparable between the bioavailability of DOC and DON:BDOC (Lake Nan)> BDOC (Lake Dong), BDON (Lake Nan)<BDON (Lake Dong). DOC and DON showed a significant positive correlation, DON and DIN showed a significant negative correlation by adding C source in Lake Nan. It’s obvious that the coupling between C and N is tight in Lake Nan. While after adding other nutrient there is no correlation between DON and DIN when bacteria degrading DOC in Lake Dong, and the coupling between C and N is not tight.