Leachability of arsenic and heavy metals from blasted copper slag and contamination of marine sediment and soil in Ninh Hoa district, south central of Vietnam

• We investigated the characteristics of blasted copper slag (BCS), sediment/soil.
• Local background values of heavy metal (HM) were derived from deeper sediment/soil.
• Using local background can correct the degree of As or HM contamination.
• Leached concentration of As and HMs from BCS were low, except Cu.
• Significant release of Cu from BCS was observed in cascade and pHstat leaching.

In recent years, shipping activities developed in Ninh Hoa district (south-central Vietnam), have raised an urgent environmental concern related to the use of copper slag as abrasive material for removing rust from the surface of the ships. This study was conducted to investigate the characteristics of the blasted copper slag (BCS). Enrichment Factors (EF) were used to assess the contamination status of sediments and soils in the surroundings of the BCS dump site. The potential release of As and heavy metals (HMs) from BCS was examined through pHstat and cascade leaching tests in combination with XRD analysis. From the results, As, Cr, Ni, Pb and Zn were characterized as moderate severely enriched to severely enriched while Cu showed extremely severe enrichment in the sediments. Regarding the soil collected at the dump site, it was strongly contaminated with As, Cu and Zn (extremely severe enrichment) whereas Cr, Ni and Pb were ranked as severely enriched. This study also demonstrates that it is important to use local background values of As and HMs in soils and sediments for a correct estimation of the degree of As or HM contamination. The cascade leaching test results from the BCS showed that the concentrations of the regulated HMs leached were lower than the EU limit for non-hazardous waste; except for Cu. Results from pHstat leaching tests at pH 4 with BCS indicated that upon acidification, HM release from the <1 mm fraction is higher compared to the bulk sample. A significant release of Cu from BCS was also observed for both fractions (<1 mm fraction and bulk sample) in pHstat leaching tests. In view of the elevated Cu concentrations found in the slag, the potential recovery of Cu from BCS should be investigated.