2000~2010年大鹏湾溶解有机氮的时空分布

依据2000~2010年每月一次的调查资料,简要描述和讨论了大鹏湾中溶解有机氮(DON)质量浓度的时空分布,并结合现场盐度、5d生化需氧量(BOD5)、总溶解氮(TDN)和叶绿素a (Chl a)实测数据探讨DON的组成、来源和滞留时间(TDON).结果表明,大鹏湾的水动力条件对DON的分布变化影响不大.DON质量浓度为(0.15±0.08)mg/L,与大亚湾的相近,但比珠江口的低,而比南海北部沿岸的高.由二元混合质量平衡模式结合周边小河溪(向海排放淡水)中TDN的DON质量分数估算的大鹏湾中陆源DON质量分数约为19%,远小于海源的,暗示大鹏湾中的DON以自生来源为主.由平均不稳定DON(LDON):BOD5比率估算的LDON质量分数约为41%.由表层平均浮游植物DON (PDON):Chl a比率估算的PDON质量分数约为17%,而由此结合累计DON估算的大鹏湾中的TDON约为15d.11a研究期间,LDON的年际变化呈下降趋势,而DON和难降解DON (RDON)的年际变化略呈上升趋势,表明RDON在大鹏湾中逐渐缓慢积累.

Temporal and spatial distributions of dissolved organic nitrogen in the Mirs Bay from 2000 to 2010

Based on the data obtained from monthly cruises from 2000to 2010, temporal and spatial distributions of the dissolved organic nitrogen (DON) concentration in the Mirs Bay were briefly presented and discussed.The DON composition,sources and residence time (TDON) were approached by combining with the salinity, 5-day biochemical oxygen demand (BOD5), total dissolved nitrogen (TDN) and chlorophyll a (Chl a) measurements. The hydrodynamics in the Mirs Bay only posed a weak impact on the distributions of DON. The DON concentration was (0.15±0.08)mg/L, which was nearly equal to that in the Daya Bay, but lower than that in the Pearl River Estuary and higher than that in the coastal waters of the northern South China Sea. A two-component mixing mass balance model in combination with the DON fraction of TDN in the peripheral small rivers was used for estimating the terrestrial DON fraction,which was found to be about 19% and much less than the marine DON fraction in the Mirs Bay, implying that the DON was mainly from the autochthonous source. The labile DON (LDON) fraction calculated by the average ratio of the LDON: BOD5 was about 41%. The average ratio of the surface phytoplankton DON (PDON): Chl a was used for estimating the PDON fraction at about 17%, based on which in combination with the integrated DON the TDON was calculated to be about 15 days. During the 11-year study period, the LDON inter-annual variability showed a decrease trend,but both the DON and refractory DON (RDON) underwent a trend of increase,which suggested that the RDON had been gradually accumulated in the Mirs Bay.