Huesemann Michael H, Skillman Ann D, Crecelius Eric A
Marine Sciences Laboratory, Pacific Northwest National Laboratory, Sequim, WA 98382, USA.
Mar Pollut Bull. 2002 Feb;44(2):142-8. doi: 10.1016/s0025-326x(01)00194-1.
In an attempt to reduce the threat of global warming, it has been proposed that the rise of atmospheric carbon dioxide concentrations be reduced by the ocean disposal of CO2 from the flue gases of fossil fuel-fired power plants. The release of large amounts of CO2 into mid or deep ocean waters will result in large plumes of acidified seawater with pH values ranging from 6 to 8. In an effort to determine whether these CO2-induced pH changes have any effect on marine nitrification processes, surficial (euphotic zone) and deep (aphotic zone) seawater samples were sparged with CO2 for varying time durations to achieve a specified pH reduction, and the rate of microbial ammonia oxidation was measured spectrophotometrically as a function of pH using an inhibitor technique. For both seawater samples taken from either the euphotic or aphotic zone, the nitrification rates dropped drastically with decreasing pH. Relative to nitrification rates in the original seawater at pH 8, nitrification rates were reduced by ca. 50% at pH 7 and more than 90% at pH 6.5. Nitrification was essentially completely inhibited at pH 6. These findings suggest that the disposal of CO2 into mid or deep oceans will most likely result in a drastic reduction of ammonia oxidation rates within the pH plume and the concomitant accumulation of ammonia instead of nitrate. It is unlikely that ammonia will reach the high concentration levels at which marine aquatic organisms are known to be negatively affected. However, if the ammonia-rich seawater from inside the pH plume is upwelled into the euphotic zone, it is likely that changes in phytoplankton abundance and community structure will occur. Finally, the large-scale inhibition of nitrification and the subsequent reduction of nitrite and nitrate concentrations could also result in a decrease of denitrification rates which, in turn, could lead to the buildup of nitrogen and unpredictable eutrophication phenomena. Clearly, more research on the environmental effects of ocean disposal of CO2 is needed to determine whether the potential costs related to marine ecosystem disturbance and disruption can be justified in terms of the perceived benefits that may be achieved by temporarily delaying global warming.
为了降低全球变暖的威胁，有人提议通过将化石燃料发电厂烟道气中的二氧化碳排放到海洋中来降低大气中二氧化碳浓度的上升。向中深层海水中释放大量二氧化碳将导致大量酸化海水羽流，其pH值范围为6至8。为了确定这些由二氧化碳引起的pH值变化是否对海洋硝化过程有任何影响，对表层（光合层）和深层（无光层）海水样本用二氧化碳进行了不同时长的鼓泡处理，以实现特定的pH值降低，并且使用抑制剂技术通过分光光度法测量了微生物氨氧化速率与pH值的函数关系。对于从光合层或无光层采集的海水样本，硝化速率都随着pH值的降低而急剧下降。相对于pH值为8的原始海水中的硝化速率，在pH值为7时硝化速率降低了约50%，在pH值为6.5时降低了90%以上。在pH值为6时硝化作用基本完全被抑制。这些发现表明，将二氧化碳排放到中深层海洋中很可能会导致pH值羽流内氨氧化速率急剧降低，并伴随氨而非硝酸盐的积累。氨不太可能达到已知会对海洋水生生物产生负面影响的高浓度水平。然而，如果来自pH值羽流内部富含氨的海水上升到光合层，浮游植物的丰度和群落结构很可能会发生变化。最后，硝化作用的大规模抑制以及随后亚硝酸盐和硝酸盐浓度的降低也可能导致反硝化速率下降，进而可能导致氮的积累和不可预测的富营养化现象。显然，需要对海洋处置二氧化碳的环境影响进行更多研究，以确定与海洋生态系统干扰和破坏相关的潜在成本是否能根据暂时延缓全球变暖可能带来的预期益处而得到合理证明。
