concentration variation的用法和样例：
例句
- Although all plants normally contain fluorine, the concentration varies greatly.
虽然在正常情况下，所有的植物都含氟，其浓度变化很大。 - Three parameters are designed to study the function of photocatalyst, which are spray layers of photocatalyst, spray area ratios and concentration of formaldehyde.
每小时纪录甲醛浓度变化，以该浓度变化评估二氧化钛光触媒去除甲醛之效能。
