该地区的土壤中含有高浓度的矿物质。

The region has high ___concentrations of minerals in its soil.

严格的法律限制了工厂排放物中有害化学物质的浓度。

Strict laws limit the ___concentration of harmful chemicals in factory emissions.

春季，空气中花粉的浓度高企，导致许多人过敏。

During spring, the ___concentration of pollen in the air causes allergies for many people.