(2)
where Pnc is the NCPI of soil HMs;Pi, max is the maximum SFPI of certain HM in the
soil; n is the number of soil HMs determined; evaluation: the standard
classification of Pnc is the same as the SFPI.
3) Impact index of comprehensive quality (IICQ )
The IICQ takes into account multiple evaluation indicators such
as ”soil geological background value”, ”pollutant limit value”, ”HM ion
impulse-valence effect” and other evaluation indicators, eliminating the
defects of the traditional ”soil standard management method” (Wilson et
al., 2010; Wang et al., 2016). It is more objective to evaluate the
cumulative risk of HMs in farmland soil, which can be calculated as
follows: