Table 5.

Risk values (THQ, HI and TR) of each metal contaminant in bivalve species, Black Sea (Bulgaria).

	Target Hazard Quotient (THQ)								Hazard Index (HI)	Target Risk (TR)
	Cd	Cr	Cu	Fe	Mn	Ni	Pb	Zn		Cr	Pb
Chamelea gallina
Spring	0.0027	0.0002	0.0004	0.0005	0.0001	0.00002	0.0001	0.0003	0.004	1.2 × 10−7	1.2 × 10−9
Summer	0.0049	0.0007	0.0005	0.0009	0.0001	0.00009	0.00003	0.0005	0.008	4.2 × 10−7	4.4 × 10−9
Autumn	0.0025	0.0003	0.0005	0.0003	0.0001	0.00007	0.0001	0.0003	0.004	1.8 × 10−7	7.7 × 10−10
Winter	0.0129	0.0058	0.0026	0.0008	0.0001	0.00029	0.00018	0.0008	0.025	3.7 × 10−6	2.3 × 10−8
Mytilus galloprovincialis
Spring	0.0032	0.0001	0.0001	0.0002	0.0001	0.00002	0.0002	0.0006	0.004	3.5 × 10−8	2.9 × 10−9
Summer	0.0050	0.0007	0.0005	0.0009	0.0001	0.00009	0.00004	0.0005	0.008	4.3 × 10−7	4.7 × 10−9
Autumn	0.0035	0.0011	0.0003	0.0018	0.0003	0.00012	0.0001	0.0010	0.008	6.8 × 10−7	7.8 × 10−10
Winter	0.0084	0.0014	0.0008	0.0010	0.0001	0.00007	0.0013	0.0008	0.014	8.9 × 10−7	1.7 × 10−8
Donax trunculus
Spring	0.0004	-	0.0032	0.0002	0.00006	-	-	0.0004	0.004	-	-
Summer	0.0005	0.0004	0.0017	0.0006	0.00016	-	0.0002	0.0005	0.004	2.7 × 10−7	2.2 × 10−9
Autumn	0.0003	0.0014	0.0012	0.0014	0.00020	0.000003	0.0002	0.0003	0.005	8.7 × 10−7	2.0 × 10−9
Winter	0.0010	0.0017	0.0076	0.0020	0.00003	0.000003	0.0006	0.0010	0.014	1.1 × 10−6	7.4 × 10−9