Application of natural and enhanced natural attenuation of heavy metals in soils and sediments

Various techniques can be considered for the remediation of contaminated sediments. The options can include capping, dredging, or physical, biological, and/or chemical treatments and natural recovery. Natural recovery could be beneficial over dredging due to a reduction in costs and lack of solid disposal requirements. Source control, however, is a major issue for sustainable remediation. In a case study, surface and core sediment samples were collected from a harbor on the north bank of the St. Lawrence River in the province of Quebec to assess heavy metal pollution and determine if natural recovery was occurring. Comparing the results of all analysis done for sediment for three different years (2015, 2017 and 2019) in the sampling area, it can be seen that some metals increased, some decreased and some of them showed nearly the same level of contamination. The results also indicated that during the sampling periods, copper, zinc and chromium were the main elements that exceeded the occasional effect level based on the Environment Canada sediment quality guidelines. Therefore, metal pollution has become a noticeable problem in this area and natural recovery was not achieved for several metals due to ongoing contamination and thus source control is critical.