Mass concentration of NP15EOdecreased 98% again after 7 days, and those of NP18EO and NP_(20)EO decreased 90% after 14days.

• NP_(15)EO、NP_(18)EO、NP_(20)EO的表观质量浓度出现先增加再降低的现象,7天后NP_(15)EO的质量浓度与初始相比又降到98%25,14天后NP_(18)EO和NP_(20)EO的质量浓度又降到90%25;