農業域の小水路における脱窒速度の測定と窒素浄化機能の評価

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Denitrification was studied at five points of small channels in Tsukuba, Japan for 1 y. Denitrification rates (DR) were measured by the acetylene inhibition technique and quantified by the increments of N_2O-N during 2 h incubation in undisturbed sediment cores (5 cm in diameter and 21 cm long) containing scdiment 5 cm in thickness. The denitrification substrate removal rate (DSRR) was simultaneously determined by the decrements of the sum of NO_3-N and NO_2-N in overlying water. The primary environmental factor to affect DR was the reduction state of the sediment surface evaluated by nitrate amounts in the 1st sediment layer (0-1.3 cm depth) and the swcondary factor was denitrification substrate concentration in the overlying water. Nitrogen purification functions were very high throughout the year at a small channel of flowing rural sewage (point A) since the sediment surfaces were in steady state. The DSRR and DR, on average, were 0.97 and 0.55 g N m<-2> d<-1>, respectively, and the nitrogen purification ratio per 100 m channel length was 2.6% against the denitrification substrate load. But the ratios at other points fluctuated widely because the sodiment surface was carried away during paddy field irrigation eriod ; moreover, the volume of flowing water was very little during the winter.
社団法人日本土壌肥料学会の論文
1998-04-05