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。

youdao

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。

youdao

Based on the analysis of the malodorous black water bodies' background, the serious organic pollution of rivers and obvious tendency to eutrophication were demonstrated.

根据对其黑臭的背景分析，发现水体有机污染较严重，河道富营养化趋势较为明显。

youdao

These were chosen to minimise the confusing effects of background pollution that might be found in more densely populated and highly industrialised areas.

ECONOMIST: Weather and pollution