Geochemical Characteristics Of Nitrogen And Phosphorus In Sediments From Typical Mariculture Areas Of Guangdong And Fujian Province

To understand the spatial distribution of nitrogen and phosphorus, and the mechanism of nutriment cycle from sediments, concentrations of different nitrogen and phosphorus forms in sediments of Nanao coastal waters on April,2009, April,2010 and September,2010 were analyzed. Also, we conduct an investigation of another marineculture area of Luoyuan Bay on October,2010. The temporal and spatial variation characteristics of nitrogen and phosphorus were discussed. The influential factors and source of nitrogen and phosphorus have been studied. Single standard index method was used to assess the pollution of nitrogen and phosphorus in sediment. The main results are as follows.Compared with April,2009, average concentrations of nitrogen and phosphorus are high in Nanao coastal waters on April,2010, total nitrogen(TN), organic nitrogen(ON), organic phosphorus(OP) and NaOH-P had an evident increasing trend(p <0.05). For example, concentration of TN was up to1203.53 mg·kg-1 in fish culture zone on April,2010, added to 30%, and concentration of OP was 432.61 mg·kg-1 added more than 40%. Concentrations of nitrogen and phosphorus are increasing year by year in Nanao coastal waters. Compare the samples of April,2010 and September, 2010 from Nanao coastal waters, nutrients of different forms of nitrogen and phosphorus showed high values in September than April, indicated a seasonal variation of nutrients in Nanao coastal waters.In horizontal distribution, nutrients of different forms showed a decreasing trend from cultured area to control area, and concentrations of nitrogen and phosphorus of fish culture zone were higher than that of shellfish and seaweed culture zone. Statistical analysis indicated that concentrations of TN in fish, shellfish and seaweed culture zone were evidently higher than that in control area(p<0.05). Concentrations of ON in seaweed culture zone was lower than that in fish culture area(p<0.01), similar to the result of OP, which suggested that large-scale fish culture play an important role in the eutrophication of Nanao coastal waters. However, large-scale seaweed cultivation can remover nutrients loading, such as OP, ON. Seaweeds are very important to maintain the safe water quality conditions in mariculture areas.Single standard index method indicated that the content of TP was overall low in the sediments of Nanao coast and Luoyuan Bay, except for fish culture zone. However, the content of TN was high, all the single standard indexes were above 1, which suggested that the nitrogen pollution was relatively serious.Through controlled experiment on impact of environmental factors on nutrients release from sediment, we found that dissolved oxygen, pH value, temperature and disturbance can affect nutrients release from the sediment, and both temperature and disturbance are the more important environmental factors, the impact process of pH value is complicated. The particular mechanism needs in-depth study.