However , except nitrate , the nitrogen concentration including nitrite , ammonia , don , pn and tn in spring 1998 were higher than those in autumn 1997 , with the average concentration of 4 . 9714 . 65 , 0 . 67 ? . 20 , 0 . 7210 . 30 , 9 . 2516 . 88 , 7 . 3014 . 42 and 22 . 9 ? 0 . 2 mol / dm3 in autumn , and 4 . 5812 . 39 , 0 . 70 + 0 . 14 , 2 . 2611 . 05 , 9 . 8814 . 92 , 7 . 8816 . 21 and 25 . 318 . 94 mol / dm3 in spring , respectively . the n / p ratio in autumn 1997 was 13 . 217 . 54 in average which a little lower than redfield ratio , nevertheless in spring 1998 the value was as high as 25 . 6113 . 0 , much hi gher than redfield ratio . there shows a clear seasonal variation of phosphorus structure in two seasons , but the nitrogen structure almost unchanged 两个季节海水中磷的结构变化明显，秋季磷主要以pp ( 54 )为主，而春季长江口营养盐、石油烃对海洋生态系统影响及动力学研究主要以po4一p ( 51 % )为主;两季节氮的结构基本一致，溶解氮都以don为主，分别为40 %和39 % :秋季no3一n比例较春季略高( 22 % ) ，而春季nh4一n比例较秋季略高( 9 % ) 。
