Terrigenous Input, Distribution And Bioavailability Of Dissolved Organic Nitrogen In Jiaozhou Bay From2012to2013

Since the late1970s, with the high-speed development of social economy ofQingdao and the ever increasing emissions of pollutants, eutrophication has becomeone of the most serious environment problems in Jiaozhou Bay (JZB). Nitrogenpollution is the key factor of eutrophication in seawater of JZB. Currently, manyresearches on the source, composition and distribution of the nitrogen pollution ofJiaozhou Bay focus on the dissolved inorganic nitrogen (DIN), while ignoring thedissolved organic nitrogen (DON) contribution to the nitrogen pollution in theJiaozhou Bay. In the aquatic ecosystem of coast, dissolved organic nitrogen (DON) isa key part of the recirculation of nutrients. DON not only can be mutually transformedwith dissolved inorganic nitrogen, but also can be a kind of important nutrition thatcan be utilized by biological potential. Therefore, based on the full knowledge of theseasonal input and distribution of DON in JZB, it is very significant for studying thebiogeochemical cycle of DON.According to Synchronous survey conducted on DON, urea (Urea), dissolvedtotal amino acids (DTAA) of rivers and wastewater treatment factories (WTFs) andmaine surveying in July, August, November2012and during March and May in2013in the Jiaozhou Bay, fluxes of DON, urea and amino acids of terrestrial input indifferent seasons in the Jiaozhou Bay are calculated. The comparative analysis of thespatial-temporal distribution of the DON, urea and amino acids in different seasons inthe Jiaozhou Bay is diverse. The ratio urea-DON, the ratio DTAA-DON anddegradation index (DIAA) can be regard as indicators, combined hydrological,chemical and biological parameters of synchronous survey, which can discussesources, bio-degradability and bioavailability characteristics and influencing factorsof DON in the different seasons in the Jiaozhou Bay, preliminarily. The following papers are the main results:Based on the analysis of DON and the content and composition of Urea andDTAA of river anf WTPs in different season around JZB, the input fluxes of DON,Urea and DTAA in the different season are estimatied.(1) The content and composition of DON, Urea and DTAA in river estuaries andWTPs are quite different in different seasons around the Jiaozhou Bay. Among them,DON, urea and amino acids of rivers into the sea distributed in16.72~1385.80μmol/L,1.93~19.50μmol/L and0.05~8.39μmol/L, and the average proportion inthe DTN is45.60%,1.33%and0.43%, respectively. The range of DON, Urea andDTAA into the JZB of WTPs exports were8.95~3177.68μmol/L,1.37~15.91μmol/L and0.30~22.39μmol/L, the average proportion of DTN reached22.94%,0.58%and0.54%, respectively. In DON, the highest input flux ha(2) The total inputs of DON, Urea and DTAA by the terrigenous inputsurrounding the JZB, are2.03×108mol,7.28×106mol,2.65×106mol, accounting for28.15%,1.01%and0.37%of the DTN, respectively. From input source perspective,the river is the main way. The highest input flux of DON occuars March, and thelowest one occuars May. The highest input flux of Urea occuars July, and the lowestone occuars March. The highest input flux of DTAA occuars May, and the lowest oneoccuars March.2、Based on the data of five cruises during July2012to May2013that carriedout in the JZB，the distribution of urea, DTAA and DON are studied.(1) The spatial distributions of DON, Urea and DTAA in surface water hadobvious seasonal difference. Among them, it has a higher level in the northeast of JZBin wole, however, some areas of JZB, it has patch shape of high value distribution inthe few season.(2) The average of Urea and DTAA in surface waters in JZB, showes asignificant seasonal difference. The high average of DON appeares in the May andNovember, but the low value is in the July and March. Urea present highconcentration in the May and March, then July and November have low value,relatively. The high DTAA concentration appeares in the May and July, but the low value is in the November and March. The higher composition of DTAA in differentseason includes Thr, Gly, Asp and Glu.(3) The sources and the influence factors of DON, Urea and DTAA of differentseason in JZB are different. Terrigenous input has influence on the DON in Augustand November, while comprehensive influence of terrigenous input andbio-geochemical process in July, March and May. Besides, terrigenous input hasinfluence on the Urea in July and November, while DTAA is affected by terrigenousinput and bio-geochemical process together.3、The application of statistical methods of correlation analysis, the preliminarydiscussion on sources and the factors influencing the space-time distribution of DONin the JZB in different seasons;At the same time, with Urea and DTAA in DONaccounted for as an index, analyzed the biological availability of DON in differentseasons;And amino acid degradation index (DIAA) as an index, evaluats bio-degradability of DON in different season.(1) The value of DIAAis quite difference in JZB, and the chang range of DIAAis-2.18~1.88. Meanwhile, differernt seasons are uneven distribution of patch shape. Itdemonstrated that spatial variation of biodegradability of DON is obvious in JZB.(2) The analysis result of (Urea+DTAA)/DON show that the biologicalavailability of DON in different seasons has significant difference in the JZB. Themean value of (Urea+DTAA)/DON is higher in March, while the mean value is lowerin July. That indicating that DON in the JZB has high biological availability, thepromoting effect on the growth of phytoplankton should not be ignored.