Index		Formula	Classification	Source
Enrichment Factor	EF	EFi = (Ci/CFe)/(Bi/BFe) where: Ci—the concentration of HM in the sediments (mg·kg−1) CFe—the concentration of iron (Fe) Bi—the reference geochemical background value of each HM BFe—the reference geochemical background value of iron (Fe)	EF ≤ 1 no enrichment 1 < EF ≤ 3 minor enrichment 3 < EF ≤ 5 moderate enrichment 5 < EF ≤ 10 moderately severe enrichment 10 < EF ≤ 25 severe enrichment 25 < EF ≤ 50 very severe enrichment EF > 50 extremely severe enrichment	Ergin et al. (1991) [90]
Pollution Load Index	PLI	PLI = (CFi1 × CFi2 × … × CFin)1/n where: n—the number of HMs CF—contamination factor defined for each studied HM	PLI < 1 no pollution PLI ≥ 1 pollution	Tommilson et al. (1980) [91]
Metal Pollution Index	MPI	MPI = (Ci1× Ci2 × … × Cin)1/n where: Ci—the concentration of HM in the sediments (mg·kg−1) n—the number of considered HMs	MPI < 1 no pollution MPI ≥ 1 pollution	Usero et al. (1997) [92]
Mean PEC quotient	Qm-PEC	Qm-PEC = ∑ni=1 (Ci/PECi) where: Ci—the concentration of HM in the sediments (mg·kg−1) PECi—the probable effect concentration of each HM	Qm-PEC < 0.5 not toxic Qm-PEC ≥ 0.5 toxic	MacDonald et al. (2000) [94]
Toxic Risk Index	TRI	TRI = ∑ni=1TRIi = {[(Ci/TECi)2 + (Ci/PECi)2]/2}1/2 where: n—the number of HMs Ci—the concentration of HM in the sediments (mg·kg−1) TECi—the threshold effect concentration of each HM PECi—the probable effect concentration of each HM TRIi—the toxic risk index of each HM	TRI ≤ 5 no toxic risk 5 < TRI ≤ 10 low 10 < TRI ≤ 15 moderate 15 < TRI ≤ 20 considerable 20 < TRI very high	Zhang et al. (2016) [96]