Phytotoxicity and bioaccumulation of copper and chromium using barley (Hordeum vulgare L.) in spiked artificial and natural forest soils

The toxicities of two heavy metals, copper (Cu2+) and chromium (Cr6+), to barley (Hordeum vulgare L.) were evaluated using two types of substrates: artificial and natural forest soils. Phytotoxicity was assessed using a standardized toxicity test. Endpoints included plant emergence and shoot and root growth. Shoot and root concentrations of Cu and Cr were also measured. Data indicated that the root biomass was the most sensitive endpoint. The results showed that toxicity of Cr to root growth (IC50=6.6 μg/g in artificial soil; IC50=61.8 μg/g in forest soil) was higher than that of Cu (IC50=13.7 μg/g in artificial soil; IC50>322 μg/g in forest soil). Data also indicated that the toxicity of Cu and Cr was significantly decreased in the spiked forest soil, suggesting lower metal bioavailability to barley in the natural soil. Analysis of tissue concentrations in barley showed that Cu and Cr were mainly accumulated in the roots. Toxicity was correlated with Cr residues in shoots (less-than-or-equals, slant11.2 μg Cr/g and less-than-or-equals, slant5.3 μg Cr/g for artificial and natural soils, respectively) and roots (less-than-or-equals, slant161 μg Cr/g and less-than-or-equals, slant51.7 μg Cr/g for artificial and natural soils, respectively) and Cu residues in roots (less-than-or-equals, slant61.8 μg Cu/g and less-than-or-equals, slant91.3 μg Cu/g for artificial and natural soils, respectively). Cu concentration in shoot tissues was less-than-or-equals, slant61.8 μg Cu/g. Since it may overestimate toxicity, effect and risk assessment using spiked soils, particularly in artificial soil, must be used with diligence.