Exploring the potential of horse amendment for the remediation of HCHs-polluted soils

This study assessed for the first time the bioremediation potential of an organic horse amendment in soils contaminated with solid wastes of the obsolete pesticide lindane (α−hexachlorocyclohexane (α−HCH) = 80 mg kg−1, β−HCH = 40 mg kg−1, γ,δ,ε−HCH≈10 mg kg−1) searching for a self-sufficient bio-based economy. Four treatments were implemented: polluted (PS, ΣHCHs = 130 mg kg−1) and control (CS, ΣHCHs = 1.24 mg kg−1) soils and the respective amended soils (APS and ACS). A commercial amendment, coming from organic wastes, was used for soil biostimulation (5% dry weight), and the temporal evolution of the enzymatic activity (dehydrogenase, β-glucosidase activity, phenoloxidase, arylamidase, phosphatase, and urease) and HCHs concentration of the soils was evaluated over 55 days under controlled humidity and temperature conditions. The horse amendment positively influenced the physicochemical properties of the soil by reducing pH (from 8.3 to 8) and increasing the organic matter (TOC from 0.5 to 3.3%) and nutrient content (P and NH4+ from 24.1 to 13.7 to 142.1 and 41.2 mg kg−1, respectively). Consequently, there was a notable enhancement in the soil biological activity, specifically in the enzymatic activity of dehydrogenase, phenol-oxidase, phosphatase, and urease and, therefore, in HCH degradation, which increased from