Determination of 17O Anomaly in Atmospheric Aerosol Nitrate

Abstract

通过改造稳定同位素比质谱仪外设设备、优化系统参数、优化细菌反硝化方法等方法，建立了一种高灵敏度高精度的大气气溶胶硝酸盐氧同位素异常值快速测定方法。本方法的检出限为0.4 μg N，在最佳进样量为0.8 μg N时，测定精度可达到0.19‰。 A novel method for rapid determination of oxygen isotope anomaly (Δ 17 O) in atmospheric aerosol samples was developed. With this method, the measurement was completed in 15 min with a relatively high analytical precision and a low determination limit. To achieve an analytical precision of 0.6‰, this method required a minimum nitrate content of 29 nmol (0.4 μg N). The analytical precision was optimum with a nitrate content of 57 nmol (0.8 μg N). The nitrate in atmospheric aerosol samples was converted to nitrous oxide by optimized bacterial denitrification process within 4 hs. After that, a thermal decomposition of nitrous oxide in sample gas was carried out in a gold tube at 800 °C after separation and purification, followed by gas chromatographic separation and isotope analysis of oxygen. The experiment results showed that the analytical precision of Δ 17 O in this method could reach 0.19‰ with a sample content of 57 nmol NO 3 − , and the analytical precision of δ 15 N could reach 0.15‰. This method was not only suitable for oxygen isotope anomaly determination in atmospheric aerosol samples, but also for the other atmospheric environmental samples such as rain and snow samples with low concentrations. This research establishes a rapid determination method which can determinate the 17 O anomaly in atmospheric aerosol samples by transforming the peripheral equipment of stable isotope ratio mass spectrometer, optimizing the system parameters and the bacterial anti-nitrification method. This method requires a minimum of 0.4 μg N, and analytical precision could reach 0.19 ‰ at a sample content of 0.8 μg N.