Combined with the traditional and geostatistical methods

the distribution pattern of three forms of total

organic

and ammonium nitrogen in the sediment of Dianchi Lake was studied. Results showed that the spatial variation of various nitrogen forms in the sediment was great . The structural factor exerted a great impact on the total N dist ribution in the layer of 0 —50 cm

while the stochastic factor and structural factor showed a similar impact on the other N forms. Generally

the content of all N forms in the sediment decreased from the north to the south. Dark spot color was present in the center of the lake

indicating various N deposited preferentially in the lake center . Meantime

the spot color became light with the increasing depth

which suggested that the lake was polluted severely with the time.