夏季渤海湾水体反硝化作用初探

Preliminary results concerning summer-time denitrification in the Bohai Bay,China

于2012年7月在渤海湾开展35个站位的水质调查,利用N2∶Ar法和膜进样质谱仪（MIMS）测定了表层水体（40 cm）反硝化产物N2的溶存浓度,计算了水体溶存N2的净增量ΔN2及氮素的反硝化损失比例。结果表明,现场温度和盐度条件下渤海湾水体溶存N2的实测浓度介于（7.76~8.74）μg/L（均值8.06±0.21μg/L,SD）,N2的理论平衡浓度介于5.41~5.75μg/L（均值5.56±0.09μg/L,SD）。由此计算得到渤海湾水体N2饱和度介于138%~154%（均值145%）,ΔN2的变化范围介于2.17~2.94μg/L（均值2.51±0.17μg/L,SD）。因此,渤海湾水体存在明显的反硝化过程。对应观测站位NO3-N浓度范围为0.01~0.09 mg/L（均值0.03±0.02 mg/L,SD）,ΔN2与NO3-N的浓度比例介于3%~64%（均值16.7%）。相关分析表明,渤海湾水体ΔN2与NO3-N浓度、温度、盐度正相关,而与DO负相关。本研究中高DO浓度条件下渤海湾水体仍存在明显的反硝化过程,因此好氧反硝化细菌对水体反硝化速率的贡献值得进一步深入研究。

Concentrations of dissolved N2 in Bohai Bay were measured with MIMS by determining N2∶ Ar ratios in summer 2012,meanwhile the net increase of dissolved N2（ ΔN2） and the loss of N via denitrification was estimated. Results showed that the measured and expected concentrations of N2 in surface water（ 40cm） ranged（ 7. 76 ~ 8. 74） μg / L and（ 5. 41 ~ 5. 75） μg / L,with average value of 8. 06 ± 0. 21 μg / L and 5. 56 ± 0. 09（ SD） μg / L,respectively.Then we calculated that dissolved N2 was supersaturated by 138% ~ 154% and ΔN2ranged（ 2. 17 ~ 2. 94） μg / L（ average 2. 51 ± 0. 17 μg/L）,which indicates the existence of denitrification in water column in Bohai Bay. Concentrations of NO3-N ranged（ 0. 01 ~ 0. 09） mg / L（ average 0. 03 ± 0. 02 mg / L）,then it is estimated that about 16. 7%of NO3-N was lost via denitrification（ ΔN2： NO-3ranged 3% ~ 64%）. Correlation analysis showed that ΔN2was positively related with NO3-N,water temperature,and salinity,while negatively related with DO. In this study,denitrification was occurred in water column with high DO level,thus it is necessary to qualify the contribution of aerobic denitrifying bacteria to denitrification rate in the Bohai Bay in the future research.