珠江广州河段沉积物无机氮的分布特征和界面交换通量

Distribution Characteristics of Inorganic Nitrogen in Core Sediments and Diffusion Fluxes in Interface from Guangzhou Reach of the Pearl River

基于现场调查与实验测试方法,研究了珠江广州河段0～50cm沉积物中无机氮(包括氨氮、硝态氮及亚硝态氮)的垂向分布特征,并由相应的间隙水与上覆水中无机氮的含量,估算该河段的交换通量。结果表明,氨氮是该河段沉积物无机氮的主要形态,变化范围在0.0535g·kg-1至1.4554g·kg-1之间,各层平均含量随深度的增加总体上呈上升趋势;硝态氮与亚硝态氮含量很低,分布上无明显规律;在该河段的沉积物-水界面中,氨氮呈自沉积物向上覆水扩散的趋势,各点平均交换通量为2.54mg·m-2·d-1,硝态氮与亚硝态氮的扩散方向与氨氮相反,平均交换通量分别为-0.06、-0.03mg·m-2·d-1。珠江广州河段沉积物-水界面无机氮的通量与其他区域相比处于中等偏上水平。

The vertical distribution characteristics of inorganic nitrogen （including ammonia, nitrate and nitrite） in the sediments ranged from 0 to 50 cm depth in Guangzhou Reach of the Pearl River were investigated. And the diffusion fluxes of inorganic nitrogen across sediment- water interface were estimated according to the nitrogenous concentration gradients at the interface. The results showed that, ammonia was the main form of inorganic nitrogen in the sediments and increased with depth, ranging from 0.053 5 g· kg^-1 to 1.455 4 g·kg^-1. The concentration of nitrate and nitrite were quite low, which suggested random rules. The average diffusion flux that the amount of ammonia diffused from sediment to pore-water across the sediment-water interface was 2.54 mg·m^-2·d^-1. In addition, the diffusion directions of nitrate and nitrite were contrary to ammonia＇s, and their average diffusion fluxes were -0.06 and -0.03 mg·m^-2·d^-1, respectively. Compared with other zones, the dif- fusion flux of inorganic nitrogen of Guangzhou Reach of the Pearl River was over medium grade slightly.