The contents of nitrate in the vegetables growing in Chongqing area varied significantly with different categories of crop species, i.e., root vegetables>leaf Vegetables>scallions>gourds>legumes>egg plants.And they were higher than the hygienical criterion stipulated by FAO in the first three categories of vegetables.The lower concentrations of nitrite inthe vegetables,on the contrary,were observed than the hygienical criterion.The samples of an identical vegetable cultivar also varied greatly in nitrate an...