第二十

In 1942 he joined the staff of the Philadelphia Navy Yard as a junior chemist and worked there for three years.

1942年，他以一名初级药剂师身份成为费城海军造船厂的一员并在那儿工作了三年

The results showed as follows: the structural properties of damaged soils were spoiled with lack of waterstable aggregates and big pores, and clayish texture; the function of nutrient and water holding were also weakened. The primary countermeasures for rehabilitating damaged soils were brought forwar

结果表明：道路毁损土地的土壤团聚体的水稳性差、大孔隙较少、土壤结构破坏，土体紧实，质地粘重，土壤的通透性、保肥保水功能弱等问题，并初步提出了一些毁损土地退化修复利用的措施。