LAUSR

Abstract To assess the tolerance, the rye-grass L. grown on soil amended with petroleum wastewater (PWW) containing four metals lead, zinc, nickel and mercury. The PWW (25 to 50%) showed remarkable increase in length and biomass. Chlorophyll ‘a and b’ increased with an increase of PWW from 25–50% while such contents decreased on increasing the 75–100% compared to control. The mass balance performed on the system showed the removal of 90–97.6% lead, 85.5–92.9% zinc, 78.9–85.5% nickle and 47.6–27.5% mercury. The model for the maximum metal reduction rate (Rmax) was much better for Pb (89.5) and Zn (72.1) with respect to Ni (57.3) and Hg (32.4). Survival of rye-grass (30-days, statics, and renewal exposures) was increased by 50% as compared to control. The toxicity index Y of PWW showed 0–25% deficiency level, 25–50% tolerance level, 50–90% toxic level and 90–100% lethal level. The experimental data showing high correlation coefficient (R2 = 0.98).