摘要
氨氧化过程决定海洋氮素形态,产生并释放温室气体氧化亚氮,是海洋氮循环的核心路径之一.准确测量海洋氨氧化速率,是深入理解海洋氮循环动力过程的关键环节.然而,受限于海洋中总体低氨氮、低速率的特点,极大限制海洋尤其是寡营养盐海域氨氧化速率的量化,亟需采用高灵敏度和高精度的方法提高对于痕量氨氧化速率的探测能力.本研究利用海水中低亚硝酸盐浓度的特点,通过适量添加亚硝酸盐,结合^(15)N-NH_(4)^(+)标记培养,采用叠氮还原法测定培养前后NO_(2)^(−)的同位素比值(δ^(15)N-NO_(2)^(−))增量来计算氨氧化速率,大幅降低了氨氧化速率的检出限,获得了夏季南海北部海水氨氧化速率垂直分布剖面.水柱氨氧化速率为低于检出限至133.524 nmol·L^(−1)·d^(−1).通过反硝化细菌法测定NO_(2)^(−)+NO_(3)^(−)(NO_(x)^(−))的δ^(15)N-NO_(x)^(−)值来计算氨氧化速率对比实验发现两方法结果一致,证实了本方法的可靠性.相较于反硝化细菌法,叠氮还原法测试氨氧化速率平均检出限0.002 nmol·L^(−1)·d^(−1)显著低于反硝化细菌法平均检出限0.018 nmol·L^(−1)·d^(−1),从而大幅提升了对于寡营养盐海域氨氧化速率的探测能力.利用该方法更低检测限、且相较于细菌还原法更易于操作的特点,有望提升对于寡营养盐海域氨氧化和氮循环的探测和认知.
Ammonia oxidation determines the speciation of bioavailable nitrogen and contributes to nitrous oxide production,representing an essential pathway of the marine nitrogen cycle.Quantitative information on marine ammonia oxidation rate,thus,is of critical importance in understanding the marine nitrogen cycle.Unfortunately,our ability to quantify the ammonia oxidation rate is largely hindered by the low substrate concentration and low conversion rate,calling for the urgent need to develop new methods with higher sensitivity and precision to measure the low ammonia oxidation rate.Using a refined ^(14)N-NO_(2)^(−)carrier amendment and^(15)N-NH_(4)^(+)labeling method,we successfully obtained the ammonia oxidation rate in the whole water column of the South China Sea,with the rates varied from below the detection limit to 133.524 nmol·L^(−1)·d^(−1).The measured rates were comparable using azide reduction and denitrifier methods for the samples with high conversion rates.However,our optimized methods had higher sensitivity(i.e.,0.002 nmol·L^(−1)·d^(−1)in our refined method compared to 0.018 nmol·L^(−1)·d^(−1)for the canonical denitrifier method),thus enabling the detection of the low ammonia oxidation rate in the mesopelagic depths of the oligotrophic ocean.In addition,the method used here is more convenient and cost-efficient than the denitrifier method,providing a step forward to measuring ammonia oxidation rate to better understand the global ocean's nitrogen cycle.
作者
张伟杰
万显会
徐敏
马玉
刘丽
祝依凡
高树基
ZHANG Weijie;WAN Xianhui;XU Min;MA Yu;LIU Li;ZHU Yifan;GAO Shuji(South China Sea Marine Survey Center,Ministry of Natural Resources,Guangzhou,510300,China;Key Laboratory of Marine Environmental Survey Technology and Application,Ministry of Natural Resources,Guangzhou,510300,China;State Key Laboratory of Marine Environmental Sciences,Xiamen University,Xiamen,361102,China;College of Ocean and Earth Science,Xiamen University,Xiamen,361102,China)
出处
《环境化学》
北大核心
2025年第5期1768-1778,共11页
Environmental Chemistry
基金
国家自然科学基金(NSFC 91328207,U1305233,2015CB954003)资助.
关键词
南海
氨氧化速率
叠氮还原法
反硝化细菌法
South China Sea
ammonia oxidation rate
azide reduction method
denitrifier method
作者简介
通信联系人:高树基,E-mail:sjkao@xmu.edu.cn。
