EFFECTS OF HALOMETHYL-1,3,5-TRIAZINES ON NITRIFICATION

To evaluate the effect of the halogenated methyl groups of 1,3,5-triaz ines on nitrification by nitrifying bacteria, twenty-six halomethyl-1, 3,5-triazines were examined. ity by the 1,3,5-triazines was determined through two experiments; Le. measured for ammonia-oxidation to nitrat e (NO3--N) in an upland soil and in the second one, for ammonia-oxidat ion to nitrite (NO2--N) by Nitrosomonas europaea ATCC 25978. The 1,3,5 -triazines bearing trichloromethyl group(s) inhibited nitrification mo re strongly both in soil and in cell suspension of ATCC 25978 than oth er partially chlorinated methyl-1,3,5-triazines. The 1,3,5-triazines h aving tribromomethyl group(s) exhibited rather weaker nitrification in hibition in soil, although they indicated the strong inhibition in cel l suspension. The halomethyl-1,3,5-triazines in this study inhibited a mmonia-oxidation step, but did not inhibit hydroxylamine-oxidation ste p in the culture of ATCC 25978. This fact was found that the inhibitor y target site of them may be on the ammonia-oxidation step from ammoni um (NH4+-N) to hydroxylamine (NH2OH), as we found for trichloromethyl- 1,3,5-triazines in our previous study.