humus

Particles of different kinds - including microscopic algae, other plankton and humus from surrounding land areas - are continuously deposited on lake bottoms.

不同类型的颗粒 - 包括显微藻类，其他浮游生物和周边陆地地区的腐殖质 - 不断沉积在湖底。

Wind and spring floods erode soils, exposing underlying layers and premiering new compositions of humus and minerals on the surface.

风沙和水灾侵蚀着土壤，暴露出地下土层，腐殖质新成分及其表面的矿物。