The saline-alkali soil is a widespread of soil types in the land distribution, and its serious influence the plant growth and development on physical and chemical characteristic.

盐碱土是陆地上分布广泛的一种土壤类型，其不良的理化性状严重影响着植物的生长发育。

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They would collect environmental samples such as soil, rubble or vegetation that may have been in contact with the chemical warfare agent and may still contain characteristic degradation products or even traces of it.

BBC: How to investigate chemical weapons allegations

Soil samples can be taken in which you can look for either residue of a chemical agent or the product's characteristic of when an agent degrades.

BBC: Syria chemical weapons claims: UK and US tread cautiously