As lead and arsenic pollution element are skew distribution, statistics of a natural background value and a content of lead and arsenic are worked out using median method of skew distribution.
由手铅、砷污染元素呈偏态分布，故采用偏态分布中的中位数法作了铅、砷自然背景值及含量的统计。
2
BACKGROUND: Environment pollution due to lead is severe day by day, and the lead-induced developmental toxicity of central nervous system is prominent.
背景：环境铅污染日趋严重，铅致中枢神经系统发育的毒性较为突出。
3
Based on the analysis of the malodorous black water bodies' background, the serious organic pollution of rivers and obvious tendency to eutrophication were demonstrated.