2018年莱州湾无机氮、磷平面分布及其结构特征

本文利用2018年5月和8月现场调查数据，对莱州湾DIN和PO₄-P的浓度频率分布、平面分布及结构特征进行了分析。结果显示，2018年莱州湾海水中DIN浓度变化范围为0.0203～1.49 mg/L，平均值为0.339 mg/L，5月浓度明显高于8月，DIN浓度为0.1～0.4 mg/L的站位比例为64.5%，超过四类海水水质标准的站位比例为17.8%。海水中PO₄-P浓度变化范围为未检出～62.3×10?3 mg/L，平均值为5.63×10?3 mg/L，8月浓度明显高于5月，PO₄-P浓度低于一类海水水质标准的站位比例为95.3%；N/P大于16的站位比例为96.3%，海水呈富营养化状态的站位比例为13.1%。DIN浓度、PO₄-P浓度、N/P及富营养化指数高值区主要位于小清河口和黄河口附近海域。DIN形态结构中，NO₃-N、NO₂-N、NH₄-N占比分别为66.6%、9.1%、24.3%，夏季NH₄-N占比较高；PO₄-P浓度过低是导致该海域N/P增高的主要因素。

Distribution and structure of dissolved inorganic nitrogen and phosphorus in Laizhou Bay, 2018

Based on field data of nutrients observed in Laizhou Bay during May and August, 2018, the distribution characteristics of nitrogen and phosphorus in Laizhou Bay were analyzed and discussed. The results showed that the concentrations of dissolved inorganic nitrogen ranged from 0.0203 mg/L to 1.49 mg/L with an average content of 0.339 mg/L and which was significantly higher in May. The dissolved inorganic nitrogen concentrations were between 0.1 mg/L and 0.4 mg/L in 64.5% of survey stations. Approximate 17.8% of investigating stations with dissolved inorganic nitrogen levels exceeded the fourth class of seawater quality standard. The proportions of NO₃-N, NO₂-N and NH₄-N in dissolved inorganic nitrogen were 66.6%, 9.1 % and 24.3%, respectively, and NO₃-N was the main form of dissolved inorganic nitrogen. The concentrations of PO₄-P ranged from not detected to 62.3×10?3 mg/L with an average content of 0.00563 mg/L and which was significantly higher in August. Approximate 95.6% of investigating stations with PO₄-P levels were lower than the first class of seawater quality standard. Approximate 96.3% of investigating stations with N/P ratio were larger than 16, while 13.1% of investigating stations with E value were larger than 1. The high value areas of dissolved inorganic nitrogen, PO₄-P, N/P ratio and E were mainly located in the sea area near Xiaoqing estuary and Yellow River estuary in the west of Laizhou Bay. The proportion of NH₄-N in dissolved inorganic nitrogen was the highest in summer. The main factor leading to the increase of N/P ratio was low PO₄-P content.