方法：采用四苯硼钠法检测并增加阴性对照管及试剂对照管，取消炭化灰化的步骤。

Methods:To test it with sodium tetraphenylborate method increasing negative control and the control of reagent and cancel carboration ash steps.

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不可渗透的粘土限制了水和黄腐酸的向下渗透，从而减少了化学风化和土壤灰化作用。

Impermeable clay limits downward percolation of water and fulvic acids, reducing chemical weathering and podzolization.

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事实上，灰化石遗址（Gray Fossil Site）里犬齿猫科动物、骆驼、大象和犀牛的骨头表明这些动物生活于400多万年前的志愿者州（Volunteer State，即田纳西州）。

In fact, at the Gray Fossil Site, bones from a saber-toothed cat, camel, elephant and rhinoceros indicate these animals lived in the Volunteer State more than 4 million years ago.

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