长江口潮滩表层沉积物对NH_4^+-N的吸附特征

The characteristics of NH-4^+-N adsorption on intertidal sediments of the Changjiang Estuary in China

沉积物对NH4+-N的吸附是氮素生物地球化学循环的关键过程之一,它在河口潮滩生态系统内氮素循环过程中起着非常重要的作用.以长江口滨岸潮滩为研究区域,运用实验模拟的方法,研究了沉积物对NH4+-N的吸附特征,结果表明,在长江口潮滩上覆水和孔隙水中NH4+-N含量的变化范围内,沉积物对NH4+-N的吸附呈线性变化;研究区域内沉积物对NH4+-N的吸附系数为3.81~9.00,且与沉积物中有机碳(TOC)含量有良好的相关关系,它揭示了有机质控制着长江口潮滩沉积物中NH4+-N的吸附行为.实验模拟与实测结果对比发现,在潮滩自然环境条件下,研究区域内沉积物对NH4+-N的吸附处在非热力学平衡状态过程中.盐度是影响NH4+-N吸附过程的重要环境因子,且导数方程关系式在低盐度范围内,盐度的微小变化对NH4+-N的吸附有显著的影响.

Adsorption of sediments on NH4^＋-N is one of the key biogeochemical processes, which plays an important role in the cycle of nitrogen in an estuary and tidal flats. NH4^＋-N adsorbed by intertidal surface sediments was studied with simulation experiment from the Changjiang Estuary. It is indicated that the adsorption of sediments on NH4^＋-N shows linear Changes in the possible range of NH4^＋-N in overlying waters and porewaters from the intertidal flat of the Changjiang Estuary. The adsorption coefficients of NH4^＋-N vary from 3. 81 to 9.00, and are closely related to sedimentary organic carbon, showing that organic matter may control NH4^＋-N adsorption behavior. Compared with the in situ measured data, it is concluded that NH4^＋-N adsorption is under the non-thermodynamic balance status under natural conditions in the Changjiang Estuary. In addition, it is also showed that salinity has an important effect on NH4^＋-N adsorption, and that the little change of salinity has a pronounced influence on NH4^＋-N adsorption in sediments within the range of lower salinity.