Influences of soil pH on cadmium toxicity to eight plant species

Abstract

Soil pollution by heavy metals affects soil quality worldwide. Cadmium (Cd) is of special concern because it might transfer from soil to plants, especially under acidic conditions, causing toxicity. This work aimed to evaluate the LC50 (lethal concentration to 50% of studied population), NOEC (no observed effects concentration) and LOEC (lowest observed effects concentration), by measuring the germination and growth of eight plant species (Beta vulgaris, Daucus carota, Lactuca sativa, Phaseolus vulgaris; Avena strigosa, Oryza sativa, Triticum aestivum and Zea mays) in soil under increasing Cd concentrations (0, 10, 40, 80, 160, and 320 mg kg-1) and two levels of acidity. Increasing the soil pH (from 4.1 to 6.4) by liming alleviated Cd toxicity and had a positive impact on seedling growth of all plant species studied. Germination was a less responsive endpoint and only the most sensitive species (L. sativa, B. and D. carota) were affected under the most acidic condition. These results were confirmed by the lower values found for LOEC and LC50 in these species regardless of the soil pH. Sensitive species are thus recommended as indicators of soil contamination in ecotoxicological studies, in which dicotyledonous species (e. g. L. sativa and B. vulgaris) are more suitable for risk assessments in Cd-contaminated soils at low concentrations, whilst monocotyledons (e. g. Z. mays) are more adequate for higher Cd concentrations (≥ 80 mg kg-1). Increasing soil pH by liming was demonstrated to be an efficient method in alleviating Cd toxicity in seedling growth.