| Nitrogen is an important nutrition for halobios, ocean organic nitrogen is very important in the global nitrogen cycle. Currently, more and more attention paid to harmful algal blooms, and dissolved organic nitrogen(DON) as a nutrient can be ab-sorbed by phytoplankton, is one of the reasons of the harmful algal blooms. Under-stand the distribution and impact factor of DON, TDN and C/N ratio is of great im-portance in ocean nitrogen cycle and the study of harmful algal blooms.Now, all routine methods measure TDN and calculate DON by subtracting the DIN. At first, this study compared two common methods for the determination of DON: persulfate oxidation (PO) and high temperature combustion (HTC).?Then ana-lyses the samples from three cruise in April, May and October 2010 in the Frequent Harmful Algal Blooms Areas of the East China Sea, study the distribution of TDN, DON and C/N ratio, and analyses their relationship with different environmental fac-tors, the main results are as following:The results shows that both methods have good agreements at blank, Precision and accuracy. They also resulted in higher recovery for various nitrogen-containing compounds, close to 100%. In the recovery experiment, the two methods all have high oxidation rate. Standard linear fitting of experimental results have shown that both methods are suitable for measurement of TDN in seawater. The results of field sam-ples have good agreements too. For field samples, the two methods also have good agreements, PO method of oxidation rate is slightly lower. And the HTC method can measured both DOC and DON at the same time, DOC/DON ratio in seawater pos-sessed on methods for the determination of consistency, and HTC method is more ef- ficient. So both methods had their own merits, but the HTC method is more suitable for the measurement of TDN in seawater samples in this paper.Horizontal distribution of TDN and DON was high near the coast and low off-shore in investigation area, resembled salinity. Higher values occurred in the estuary, particularly near the Yangtze River estuary, indicated that TDN and DON was mainly controlled by terrestrial inputs. In the harmful algal blooms, the DON high value oc-curred in the chlorophyll low value area, it means that DON is absorbed by plankton. C/N ratio in the investigation that showed a trend of low near the coast and high off-shore, near-shore land effected by terrestrial inputs. C/N ratio in the high chlorophyll area close to the Redfield ratio, C/N ratio rises on the far bank.The article select three sections to analyses, in the three section, TDN and DON both showed a trend of high near the coast and low offshore, and was high in surface waters and low in bottom waters near the coast, distribution is the reverse on the far bank. Average distribution was high in surface waters and low in bottom. Trends of the C/N ratio in all three sections low near the coast high offshore, and the C/N ratio middle water layer near Redfield ratio.Results of day and night sequent pointing research of ZA3 shows?that TDN and DON changes greatest in 10m water layer, and there was high and low values near chlorophyll maximum and minimum value, they were effected by sunlight and tides. The distribution of C/N ratio was uniform, it was mainly controlled by tides.TDN and DON were inversely correlated with salinity, especially in October. It shows terrestrial inputs have a significant impact. TDN and DON were also inversely correlated with chlorophyll, but not obvious, especially in May. In April and October TDN and DON were more correlate with chlorophyll in middle water layer than in surface and bottom. C/N ratio was correlated with salinity, and has no significant cor-relation with chlorophyll in May. In the middle layer of April and October, C/N and chlorophyll were related. |
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