STUDIES ON THE FEASIBILITY OF DIRECT MEASUREMENT OF N LOSSES AS N_2 AND N_2O PRODUCED BY DENITRIFICATION WITH ~(15)N TRACER TECHNIQUE AND MASS SPECTROMETER

With 15 N tracer technique, mass spectrometer and a self\|designed installation including sample entrance, reduced Cu tube, high\|efficiency O\-2 trap, liquid N\-2 cold trap, a method for direct determination of N losses as N\-2 and N\-2O produced by denitrification is set up.The average of 15 N natural abundance of atmospheric samples determined is 0\^3659%(the theoretical value is 0\^3660%) with C.V.% of 0\^09% and an average of absolute error of 0\^0002%, which is up to the error standard of the mass spectrometer used. C.V.% of measurement of 15 N abundance in different gas samples and in the substrate NO\+\+-\-\-3 undergoing denitrification are 0\^03%～1 08% and 1\^22%～5\^21%,respectively,indicating that the pretreating installation is highly efficient for elimination of O\-2, CO\-2 and H\-2O in gas samples, and the method is feasible for direct measurement of 15 N losses as N\-2 and N\-2O. As the calculation of 15 N losses is based on atom excess % of 15 N( 15 N abundance of gas sample minus 15 N natural abundance of atmospheric N\-2), C.V.% of determination of 15 N losses is probably larger than 5% if atom excess % of 15 N in gas samples is smaller than 0\^014%. It is suggested that the 15 N abundance higher than 0\^380% in gas samples be suitable.