海水无机碳对过量无机氮输入引起的富营养化响应的模拟研究

Effects of Excessive Inorganic Nitrogen on Inorganic Carbon System in Seawater Simulated Experiments

模拟研究了在添加过量无机氮造成海水的富营养化条件下,水体pH、无机碳体系、海-气CO2通量的变化过程,探讨了海水无机碳对过量无机氮输入引起的富营养化响应机制.结果表明,NO3-添加组中,当浓度≤37.60μmol.L-1时,HCO3-、p(CO2)增加,pH、CO32-下降;当浓度≥188μmol.L-1时,则正好相反.NH4+添加组中,当浓度≤25.20μmol.L-1时能够明显促进水体HCO3-、p(CO2)减少,pH、CO23-增加,水体表现为吸收大气CO2;当浓度≥126μmol.L-1时,水体表现为向大气释放CO2,且强度随浓度的增加而增强.NO2-添加组中,当NO2-浓度在7.90μmol.L-1时,HCO3-、p(CO2)呈明显的下降趋势,pH、CO32-则随时间明显增加,水体表现为吸收大气CO2且强度随时间的增加而增强,而当NO2-高于和低于此浓度时,无机碳变化不明显.水体Chl-a较对照组的增加量(ΔChl-a)与Δp(CO2)具有很好的负相关关系(r=-0.87,p<0.000 1,n=16),表明造成以上差异的原因与水体中浮游植物在不同形式不同浓度无机氮作用下对水体无机碳利用性不同有关.

The influence of excessive inorganic nitrogen（NO3^-,NH4^＋,NO2^-） on the pH,inorganic carbon system and air-sea CO2 flux was studied in laboratory seawater simulation experiments.The result indicates that the excessive inorganic nitrogen significantly has an important influence on the inorganic carbon system in all conditions.At the NO3^- addition groups,HCO3^- and p（CO2） increase while pH and CO3^2- decrease when the concentration of NO3^-≤37.60μmol·L^-1.But high concentration≥188μmol·L^-1 is just the reverse.The seawater changes from carbon source to carbon sink of atmospheric CO2 with NO3^-addition increased.At the NH4^＋addition groups,HCO3^- and p（CO2） decrease while pH and CO3^2- increase when the concentration of NH4^＋≤25.20μmol·L^-1.However,when the concentration of NH4^＋≥126μmol·L^-1,the concentrations of HCO3^- and p（CO2） increase with NH4^＋ addition and the seawater changes from carbon sink to carbon source of atmospheric CO2 and the int ensity of carbon source has a positive relationship with the concentration of NH4^＋.At the NO2^- addition groups,the concentrations of HCO3^- and p（CO2） decrease while pH and CO3^2- increase with time scale and the seawater acts as a strong carbon sink with NO2^- addition of 7.90μmol·L^-1 while at the other NO2^- concentration levels,the carbon sink is weak in seawater.The Chl-a concentration of nutrient addition groups compared with control（ΔChl-a） shows a significant negative correlation with Δp（CO2）（r=-0.87,p〈0.0001, n=16）.The main controlling factor to the variation of inorganic carbon system is the adaptation of phytoplankton to different form and concentration of nitrogen.