海岸带水体氮、磷的测定方法与准确测定

Determination Method and Accurate Determination of Nitrogen and Phosphorus in Coastal Water

海岸带盐度过渡区域水体中氮、磷的准确测定对陆海统筹及海岸带管理起着至关重要的作用。为探究盐度对氮、磷测定准确度的影响,进而明确河口海岸带淡水-咸水盐度过渡区不同形式氮、磷测定方法的选择依据,分别采用淡水和海水的相关国家标准方法,测定不同盐度下不同质量浓度氮、磷的人工海水和天然海水水样中氨氮、亚硝氮、总氮、活性磷酸盐和总磷的质量浓度。结果表明,盐度对某些氮、磷的淡水法和海水法测定结果有一定程度的影响。对氨氮的测定,当S≤4.0时淡水法或海水法均可准确测定水体中的氨氮,S>4.0时应对水样进行pH调整预处理后用海水法进行测定;对亚硝氮的测定,淡水法和海水法的测定结果无明显差异;对总氮的测定,当S≤5.0时应采用操作简单、测定准确的淡水法测定,S>5.0时应采用海水法。对水体中的活性磷酸盐的测定,在低盐低磷(S≤35.0且ρ_(PO_(4)^(3-))≤0.2 mg·L^(-1))的情况下盐度对淡水法和海水法测定结果的影响微乎其微,而对于高盐高磷(S>35.0且ρ_(PO_(4)^(3-))>0.2 mg·L^(-1))的水样选择灵敏度更高的海水法测定更准确;对总磷的测定,选取海水法测定准确度更高。研究结果为海岸带水体不同形式氮、磷质量浓度的准确测定与方法选择提供了科学依据。

Accurate determination of nitrogen and phosphorus in coastal zone plays a vital role in land-sea coordination and coastal zone management.The purpose of this study is to explore the influence of salinity(S)on test accuracy for different forms of nitrogen and phosphorus and to clarify the basis for the selection of nitrogen and phosphorus test methods in salinity transition zone of estuarine and coastal waters.The mass concentration of different forms of nitrogen and phosphorus in both simulated seawater samples and real seawater samples were analyzed by the national standard fresh water and seawater methods.The results indicated that the salinity had a certain influence on the test results using fresh water and seawater methods.To determine the ammonia nitrogen,when the sample salinity was less than 4.0,using both fresh water and seawater methods can accurately determine the concentration of ammonia nitrogen in the coastal water.However,when the salinity was more than 4.0,to adjust water samples pH was an indispensable step for using the seawater method.And for determining the nitrite,there was no obvious difference between using fresh water method or seawater method.To determine the total nitrogen,a salinity of 5.0 was the threshold for selecting either fresh water method or seawater method.To determine the active phosphate in coastal waters,the influence of salinity was negligible under the low salinity and low phosphorus(S≤35.0 and ρ_(PO_(4)^(3-))≤0.2 mg·L^(-1))conditions,but for water samples with high salinity and high phosphorus(S>35.0 and ρ_(PO_(4)^(3-))>0.2 mg·L^(-1)),it was more accurate to choose more sensitive seawater method.To determine the total phosphorus,the seawater method was of higher accuracy.This study provided a scientific basis for the accurate determination and method selection for different forms of nitrogen and phosphorus in coastal waters.