Natural sinkholes generally form when heavy, water-saturated soil causes the roof of an underground limestone cavity to collapse, or when water widens a natural fracture in limestone bedrock.

一般自然灰岩坑形成机理是由于有份量的水饱和土导致地下石灰岩洞顶层坍塌，或者由于水加宽了石灰岩床的天然裂缝而导致。

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Soil conductivity represents the conductive capability of soil solution in digital form, reflecting the state of water and salt in the soil.

而土壤电导率是以数字形式表示土壤溶液的导电能力，反映了土壤的水盐状况。

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N in the main form of nitrate through the subsurface runoff was put into the stream, the vegetation-covered riparian had high on the nutrient in the soil water.

溪流相邻高地通过地下径流向溪流中N素的输入，主要是以硝态氮的形态通过土壤水的输入；

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Until the 20th Century, the nutrient element only came to Earth in a reactive form that is usable by plants and animals, thanks to certain microbes in soil and water (and to a smaller extent in lightning strikes).

BBC: Leaving our mark: Fossils of the future