林县食物与饮水中的硝酸盐和亚硝酸盐

NITRATES AND NITRITES IN FOODS AND PORTABLE WATER FROM LINXIAN

本研究对林县220份食物样品和109份饮用水进行了硝酸盐(NO_3^-)的测定,同时对204份食物样品和113份饮用水也作了亚硝酸盐(NO_2^-)的测定,结果表明NO_3^-和NO_2^-普遍存在于食物样品和饮用水中。主要食物中NO_3^-和NO_2^-含量的平均值分别为1.516±0.885到20334.924±4250.862mg/kg和0.13±0.099到52.084±35.003mg/kg(表1)。发现食物发霉和存放较长时间后,NO_2^-含量有增高的趋势,这可能是微生物还原NO_3^-为NO_2^-的结果。各种饮用水中NO_3^-和NO_2^-含量的平均值(mg/L)分别为:池水15.43±10.64和0.245±0.175;旱井水14.07±9.19和0.246±0.172;井水36.37±26.24和0.349±0.239(表2)。结果表明井水中NO_3^-和NO_2^-含量高于池水和旱井水,统计学处理有显著差别(P<0.01和P<0.05)。

As a source of precursors in the formation of carcinogenicN-nitroso compounds, we determined the nitrate(NO3-)and nitrite(NO2)contents on foods and in portable water from Linxian county, a high incidence area of esophageal cancer. The average levels of NO-3 in 220 samples of staple foods (dry wt.) ranged from 1.516±0.885 (cornmeal) to 20, 334.924 ± 4,250.862 mg/kg ( turnipchips), and the average amounts of NO-2 in 204 food samples were from 0.131 ±0.099 (cornmeal) to 52.084± 35.003 mg/kg (turnipchips) (Table 1). NO-2 levels tended to be increased in stored foods and in those contaminated with fungi, because the microbes may reduce NO-3 to NO-2 in the moldy foods. The average contents of NO-3 109 samples and NO-2 (113 samplse) of portable water derived from ponds were 15.43±10.64 and 0.245±0.175mg/L. respectively; those from water kept in dry-wells were 14.07±9.19 and 0.246±0.172mg/L respectively; and from well water 36.37±26.24 and 0.349±0.237mg/L respectively (Table 2). Thus the well water contained higher levels of NOi and NO-2 than that from the ponds and dry-wells, and the difference was statistically significant.