top soil的用法和樣例：
例句
- If the topsoil is taken away by erosion, plants can no longer grow in the soil left behind.
如果因水土流失而衝掉了表土，植物不能再在留下的土壤中生長。 - The runoff sediment has higher clay content than the surface soil, andthe splash soil has higher fine sand content.
通過對侵蝕上壤的顆粒組成分析表明，侵蝕對土壤顆粒具有選擇性，徑流侵蝕泥沙中粘粒含量比侵蝕表土含量高，濺蝕泥沙中細沙粒含量變高。
