我国典型潮间带沉积物-水界面无机氮源汇效应

Simulation of Inorganic Nitrogen Fluxes at the Sediment-water Interface in a Typical Intertidal Zone,Eastern China

以中国东部沿海12个典型潮间带为研究对象,通过室内模拟测定了潮间带沉积物-水界面硝酸盐(NO_3^-)和氨氮(NH_4^+)的源汇通量,分析了沉积物对上覆水体无机氮源汇效应的空间分布特征,以及环境因子的影响.结果发现:(1)NO_3^--N的总通量范围是-2.91~3.34 mmol·(m^2·h)^(-1),NH_4^+-N的总通量范围是-4.36~2.34 mmol·(m^2·h)^(-1).12℃和35℃温度下,无机氮的平均值是-0.04 mmol·(m^2·h)^(-1),我国东部典型潮间带沉积物表现为氨氮和硝氮的有效汇库.(2)潮间带的硝氮和氨氮通量存在纬度分异.12℃时,纬度越高,氨氮硝氮通量值越大;25℃和35℃时,潮间带硝氮通量值大小随纬度的变化为,25°~35°N<15°~25°N<35°~45°N.而氨氮通量值,25°~35°N>15°~25°N>35°~45°N.(3)温度通过影响硝化反硝化的耦合作用影响无机氮通量.潮间带的NO_3^--N通量随温度的增加而减小,15°~25°N和35°~45°N地区NO_3^--N通量随温度先升高再降低,25°~35°N地区NO_3^--N通量随温度一直减小.每个纬度区,温度越高,NH_4^+-N通量值越低.(4)上覆水体的盐度、沉积物总有机碳(TOC)、总氮(TN)含量,孔隙水氨氮、硝氮浓度,容重等环境因子对通量没有单一的显著影响,协同影响NO_3^--N、NH_4^+-N在潮滩沉积物水界面的空间分异.

Taking 12 typical intertidal zones along the eastern coast of China as the research object,indoor tide simulation experiments were conducted to measure exchange fluxes of nitrate nitrogen（NO3^--N） and ammonia nitrogen（NH4^＋-N） between overlying water and sediments,to investigate their spatial distribution,and to clarify controlling factors such as salinity,temperature,and organic matter.Results showed that the total NO3^--N flux was-2. 91-3. 34 mmol·（m^2·h）^-1,while the total flux of NH4^＋-N was-4. 36-2. 34 mmol·（m^2·h）^-1. The average flux,at 12℃ and 35℃,was-0. 04 mmol·（m^2·h）^-1,indicating that typical intertidal zone sediment is an effective sink for ammonia nitrogen and nitrate nitrogen. There was a significant difference in the spatial distribution of nitrate and ammonia nitrogen fluxes. At 12℃,the higher the latitude,the greater the ammonia nitrogen flux; results for the 25°-35° N intertidal nitrate flux were as follows： 15°-25°N 35°-45°N at 25℃ and 35℃,while the flux of ammonia nitrogen was 25°N-35°N 15°-25°N 35°-45°N. The fluxes of the three intertidal zones decreased with increase in temperature,which controls the coupled nitrificationdenitrification taking place in the upper layer of sediment and at the bottom of overlying water. NO3^--N fluxes first increased and then decreased with temperature at 15°-25°N and 35°-45°N,while NO3^--N fluxes at 25°-35°N always decreased with temperature. At each latitude,the higher the temperature,the lower the NH4^＋-N flux. There was no single significant effect of environmental factors on fluxes. Salinity,sediment organic carbon（OC）,sediment total nitrogen（TN）,concentrations of ammonia nitrogen and nitrate nitrogen in pore water,and bulk density synergistically affected the spatial differentiation of exchanged NO3^--N and NH4^＋-N fluxes.