The evaluation of Hudson River sediment as a growth substrate - Microbial activity, PCB-degradation potential and risk assessment.

The potential use of growth substrates prepared with an admixture of 10% to 75% Hudson River sediments was evaluated by analysis of changes in microbial activity (measured using Biolog Ecoplates) and molecular markers (presence of degradative tceA1 and bphA genes) as well as potential risks (health and environmental risk quotients). The highest microbial activity was found in growth substrate with 25% Hudson River sediments compared to unamended control soil, with significant differences from samples amended at lower (0-10%) and higher (25-75%) proportion of sediment. Microbial activity increased with the proportion of sediment amendment (≥25% sediment); however, this increase in microbial activity was not affected by increasing pollutant concentrations (PCBs, Pb, Cr Ni and Zn) nor decreasing TOC content. The growth substrate amended with Hudson River sediments increased PCB degradation genes, as evidenced by the presence of tceA1 and bphA genes responsible, respectively, for reductive dehalogenation and oxidation of a range of aromatic organic compounds including PCBs. An assessment of risk quotients showed that the growth substrates containing lower doses of Hudson River sediments (10-50%) meet the international requirements for use in agriculture/horticulture for the production of non-food crops. Nevertheless, due to the elevated content of some toxic metals and PCBs, the growth substrate prepared with the highest proportion of sediments (75%) was not suitable for agricultural/horticultural use.