Question

The shallow sandy aquifer (4 feet thickness) is contaminated with 1,2-XYZ (K oc = 20 L/kg) at an average soil concentration of 800 mg/kg. A batch soil washing device is designed to treat 1,100 kg of contaminated soil (f oc = 0.004) with 900 gallons of clean water. Find the concentration of 1,2-XYZ in water and in soil and water after (a) one wash, and, (b) two wash.

Answer 1

This study demonstrates the benefits of combining hydroxyapatite application and phytoextraction for the improvement of soil quality when remediating heavy metals.

Four plant species were successfully established in the hydroxyapatite-amended soil and produced different amounts of aboveground biomass in the order of Pennisetum sp. > Elsholtzia splendens > Setaria lutescens > Sedum plumbizincicola.

Results indicated that Pennisetum sp. was the best species for Cu and Cd removal from the contaminated soils. The application of hydroxyapatite and four plant treatments could improve the content of >0.25 mm mechanically stable (DR_0.25) and water-stable (WR_0.25) aggregates and the stability of soil aggregates, the largest increase being with the treatment of Pennisetum sinese.

In addition, hydroxyapatite and phytoremediation could improve soil enzyme activity, and Elsholtzia splendens had the best effect in this respect. In conclusion, Elsholtzia splendens and Pennisetum sp. may be the best choices for the remediation of this type of heavy metal contaminated soil.