Thanks for your advice, for the first question, this part of the ambiguous expression has been modified to “schools should keep desks and teaching AIDs clean and tidy, and urge children to clean up after outdoor activities”
In addition, dried soil samples from living spaces (0.5 g) were digested with the same pre-treated and analyzed by ICP‒MS for Pb, As, Cr, Cu, Ni, Cd, and Zn.