深圳湾及邻近沿岸水域总溶解氮的分布、组成和来源及氮形态的转化

依据2000—2011年每月1次的调查资料,简要描述和讨论了深圳湾及邻近沿岸水域中总溶解氮(TDN)质量浓度的时空分布,并结合现场盐度、总凯氏氮、氨氮、亚硝酸盐氮和硝酸盐氮实测数据探讨TDN的组成和来源,以及溶解无机氮(DIN)和溶解有机氮(DON)之间的转化.结果表明,深圳湾和伶仃洋东部沿岸的TDN质量浓度分别为(2.870±2.150)mg·L-1和(0.679±0.405)mg·L-1.在深圳湾,由于受到周边陆源排放的影响,TDN质量浓度在丰水期较低,枯水期较高.在伶仃洋东部沿岸,由于受到珠江径流量的制约,TDN质量浓度呈明显的年周期循环特征,6月达到最高,为1.103 mg·L-1左右,而12月最低,为0.420 mg·L-1左右.12年研究期间,伶仃洋东部沿岸TDN质量浓度的年际变化略呈上升趋势,从0.560 mg·L-1上升至0.702 mg·L-1;深圳湾TDN质量浓度在2000—2004年呈上升趋势,从2.140 mg·L-1上升至3.577 mg·L-1,2005—2011年则呈下降趋势,从3.266 mg·L-1下降至2.280 mg·L-1.研究海区中的TDN具有"保守性",主要来自陆源排放.依二元混合质量平衡模式估算的伶仃洋东部沿岸TDN的陆源质量分数约为68.5%,而深圳湾的均大于87.0%.DIN是TDN的主要赋存形态.在氮从河口向海迁移期间,复杂的生物地球化学过程使DIN转化为DON的速率大于DON转化为DIN的速率.

Transformation of nitrogenous forms,and composition,sources and distributions of total dissolved nitrogen in the Shenzhen Bay and adjacent coastal waters

Based on the data obtained from monthly cruises from 2000 to 2011, temporal and spatial distributions of the total dissolved nitrogen (TDN) concentration in the Shenzhen Bay and the coastal eastern Lingdingyang Estuary were presented and discussed. Composition and sources of the TDN and transformations between the dissolved inorganic nitrogen (DIN) and dissolved organic nitrogen (DON) were also investigated by combining with measurements of the salinity, total Kjeldahl nitrogen, ammonia nitrogen, nitrite nitrogen and nitrate nitrogen. The results showed that the TDN concentration was 2.870±2.150 mg·L^-1 in the Shenzhen Bay and 0.679±0.405 mg·L^-1 in the coastal eastern Lingdingyang Estuary. The TDN concentration was higher in the low water periods than the high water periods in the Shenzhen Bay under influence of the seaward discharges from the peripheral areas. The TDN concentration changed with an evident annual cycle in the coastal eastern Lingdingyang Estuary, highest at about 1.103 mg·L^-1 in June and lowest at about 0.420 mg·L^-1 in December due to restriction of the Pearl River's runoffs. The inter-annual variability of the TDN concentration increased slightly from 0.560 to 0.702 mg·L^-1 in the coastal eastern Lingdingyang Estuary during the 12-year study period, while increased from 2.140 to 3.577 mg·L^-1 in the period 2000~2004 and decreased from 3.266 to 2.280 mg·L^-1 in the period 2005~2011 in the Shenzhen Bay. The TDN in the studied area was nearly conservative and mainly originated from the terrestrial sources. A two-component mixing mass balance model was used for estimating the TDN terrestrial fraction at about 68.5% in the coastal eastern Lingdingyang Estuary and more than 87.0% in the Shenzhen Bay. DIN was the major existing form of TDN. During the transport of nitrogen from the river's outlets to the open sea, the transformation rate from the DIN to the DON was greater than that from the DON to the DIN through the complex biogeochemical processes.