The concentration of heavy metals in surface water (n=54) Concentration (mg / L) HMs Min Max Mean No sample over MLs (n,%) MLs QCVN 08: 2015 As 0.02 0.42 0.19 54 (100) ≤ 0.01 Pb 0.03 0.39 0.17 54 (100) ≤ 0.02 Cd 0.00 0.03 0.02 53 (98.15) ≤ 0.005 Cr 0.32 4.32 2.56 53 (98.15) ≤ 0.050 Hg KPH - - 0 (0.00) ≤ 0.001 Table 3.2.