Testing of different plants to determine influence of physico–chemical properties and contaminants content on municipal sewage sludges phytotoxicity

This study attempts to evaluate the Phytotoxkit? as a tool for measuring the toxicity of municipal sewage sludges using 10 common plants: mustard, turnip, cress, red clover, cucumber, tomato, radish, sorrel, and spinach. The results were used to determine a germination index (GI) and a median effective concentration (EC) value for each plant. The trace metal and polycyclic aromatic hydrocarbon (PAH) contaminant content and the physical–chemical properties were examined. Most sewage sludges were characterized by an unfavorable electrical conductivity value of about 5.2 mS/cm^?1. The most abundant trace metals were zinc (Zn) at 871–1680 mg kg^?1, manganese (Mn) at 245–661 mg kg^?1, and copper (Cu) at 88.2–161.0 mg kg^?1. The lowest values were determined for cobalt (Co) at 2.9–3.8 mg kg^?1 and cadmium (Cd) at 0.7–3.7 mg kg^?1. The PAH sum was based on 10 individual compounds (USE EPA), and the PAH content ranged from 4.76 to 27.95 mg kg^?1, most of the sewage sludges showing a predomination by carcinogenic PAHs. The GI values, based on seed germination and root growth inhibition bioassays, showed increasing plant sensitivity to the tested sewage sludges in the following order: cress > turnip > mustard > sorrel > tomato > sorgo > red clover > radish > cucumber > spinach. The EC50 sewage sludge values lay in the range 31–404 g/kg of soil, and significant relationships were found for most of the plants between EC50 and the magnesium content (Mg²⁺: α = 0.888–0.924, P = 0.05), calcium content (Ca²⁺: α = 0.813–0.911, P ≤ 0.05), and pH (α = ?0.913–0.948, P = 0.05). In the case of sewage sludge pollutants, significant relationships were found for trace metals such as: strontium (Sr: α = 0.851–0.948, P ≤ 0.05), chromium (Cr: α = 0.858, P ≤ 0.05), and nickel (Ni: α = 0.955, P = 0.05), as well as pyrene (PAHs). © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2010.