Abstract: We examined the oil washing capability of sodium lignosulfonate (SL) and the elution efficiency of the combination ability of SL with surfactants such as triton X₁₀₀ (TX₁₀₀) in soil contaminated with high-concentration petroleum. We assessed toxicity of residual pollutants to seed germination and root elongation of six species planted in the eluted soil with water washing twice after surfactant washing. The results showed that SL could desorb petroleum from the oil-contaminated soil. The optimized cleansing conditions of SL were as follows: SL concentration of 2.5 g·L^-1, temperature of 30 ℃, time of 60 min, rotation speed of 200 r·min^-1, and pH of 11. Under such conditions, the maximum oil removal rate was 25.4% and 42.3% for the artificial oil contaminated soil (FP) and in site petroleum contaminated soil (XJ), respectively. Based on the above results, six groups of optimal compound formulation were confirmed through repeated experiments as follows: TX₁₀₀ (0.06%-0.10%), SL (0.20%-0.25%), sodium carbonate (0.37%-0.41%), and sodium silicate (0.36%-0.42%). When solid liquid ratio was 1:15 and total reagent concentration was 10.8 g·L^-1, the efficiency of oil washing was 69.6%-77.9% and 80.3%-89.7% for FP and XJ soils, respectively. Results from the toxicity tests of residual pollutants in the eluted soils for germination and root growth of common crop, vegetable and forage seeds showed no toxic effect in FP-soil, and an inhibitory effect in XJ-soil to some extent, which was 1.0%-2.5% for germination percentage and 3.9%-10.9% of root elongation. Therefore, the compound eluant containing SL is of great significance for the establishment of green, low-cost, and high-efficient cleansing technique for soil contaminated with high-concentration petroleum.

Key words: sodium lignosulfonate, oil contaminated soil, triton X₁₀₀, seed germination, toxicity measurement.