辽东湾营养盐基准值的研究与确定

辽东湾作为我国重要沿海经济区,多年来承载着沿海地区排放的大量营养物质,近岸海域富营养化严重。依据2014—2017年辽东湾海水环境质量监测数据,采用频数分析法推导出辽东湾近岸海域营养盐溶解无机氮、活性磷酸盐及其响应指标溶解氧(DO)的基准值,并应用1974年辽东湾尚未被污染时,国家海洋局渤海专项调查数据绘制频数分布曲线,以中值作为参照状态进行校验,对比2种方法的结果,综合分析推导出溶解无机氮、活性磷酸盐及DO的推荐基准值。结果表明,应用频数分析法得到辽东湾溶解无机氮、活性磷酸盐和DO的基准值分别为0.050、0.002和9.61 mg/L,应用参照状态法得到溶解无机氮、DO浓度分别为0.053、6.29 mg/L。对比频数分析法和参照状态法的结果可知,2种方法得到的溶解无机氮基准值基本一致,但DO基准值相差比较大。考虑GB 3097—1997《海水水质标准》中DO浓度的第一类水质标准限值(6.0 mg/L),最终确定辽东湾溶解无机氮、活性磷酸盐和DO的推荐基准值分别为0.05、0.002和6.29 mg/L。

Study and determination of nutrient criteria in Liaodong Bay

As an important coastal economic zone in China, Liaodong Bay carries a large number of nutrients discharged from coastal areas for many years, and the coastal area is seriously eutrophicated. Based on the monitoring data of seawater environmental quality in Liaodong Bay from 2014 to 2017, the reference values of dissolved inorganic nitrogen, active phosphate and their response index dissolved oxygen (DO) in the inshore waters of Liaodong Bay were derived by frequency analysis. Also, the frequency distribution curve was drawn using the special survey data of Bohai Sea of State Oceanic Administration when Liaodong Bay was not been polluted in 1974, and the median value was used as the reference state for verification. Finally, the results of the two methods were compared, and the recommended baseline values of dissolved inorganic nitrogen, active phosphate and DO were comprehensively analyzed and deduced. The results showed that the baseline values of dissolved inorganic nitrogen, active phosphate and DO obtained by frequency analysis was 0.050, 0.002 and 9.61 mg/L, respectively, and the reference states of dissolved inorganic nitrogen and DO in Liaodong Bay was 0.053 and 6.29 mg/L by reference state method, respectively. Compared with the results of frequency analysis and reference state method, the reference values of dissolved inorganic nitrogen obtained by the two methods were basically the same, but DO baseline values were quite different. Considering that the class Ⅰ water quality standard limit of DO concentration in Seawater Quality Standard (GB 3097-1997) was 6.0 mg/L, the recommended baseline values of dissolved inorganic nitrogen, active phosphate and DO in Liaodong Bay was finally determined as 0.05, 0.002 and 6.29 mg/L, respectively.