**3.2 Data collection and processing**

Nineteen superficial sediment samples were collected along the Liaohe River protected area. At each site, three surface sediments were collected and placed into polyethylene bags and sealed. An Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) was applied for the determination of heavy metals (As, Cd, Cr, Cu, Ni, Pb, and Zn). The details are found in [11].


#### **Table 5.**

*Contamination factors (C <sup>i</sup> <sup>f</sup> ) of different elements detected in sediments.*
