CR(VI) phytoremediation by hairy roots of Brassica napus: assessing efficiency, mechanisms involved, and post-removal toxicity.

Industrial activities such as leather tanning involve the use of highly toxic inorganic pollutants, like Chromium (Cr). This work evaluated Cr(VI) remediation by hairy roots (HR) of Brassica napus, paying close attention to the mechanisms involved and the toxicity of post-removal solutions. Results showed that these roots were capable of tolerating concentrations of up to 10 mg L-1 Cr(VI), while higher concentrations were toxic for HR development. Removal efficiency was assessed through the use of synthetic solutions containing different initial Cr(VI) concentrations (2, 5, or 10 mg L-1). Regardless of these initial concentrations, the highest removal efficiency values were between 80 and 90% after 24 and 48 h of treatment, using a 2.0 g inoculum. The mechanisms involved were Cr accumulation (60%) and to a lesser extent, adsorption to the root biomass (30%). A fraction of Cr(VI) was intracellularly reduced to Cr(III), which suggests reductases may have played a role. Additionally, post-removal toxicity was evaluated through two bioassays (Lactuca sativa L. and AMPHITOX test) after the removal of 10 mg L-1 Cr(VI). The treated solutions showed moderate phytotoxicity for L. sativa L. and no toxicity for R arenarum. The ability of HR to remove 10 mg L-1 Cr(VI) from real tannery effluents collected from a regional industry (Córdoba province, Argentina) was also determined. The high removal efficiency observed (98%) demonstrates this system can be successful in treating complex wastewaters.

Lethal and teratogenic effects of phenol on Bufo arenarum embryos.

Phenol and their derivatives are used in several industries and they have a high potential toxicity for animal and plant species. They were found in variable concentrations, as high as 1000 mg/L, in industrial wastewater and, they are often discharged into the environment. Amphibian embryos are useful indicators of environmental pollution. However, to our knowledge, there are not studies focussed on the toxic effects of phenol on Bufo arenarum, which is an anuran widely distributed in South America. Therefore, the effect of phenol on the survival and morphogenesis of these amphibian embryos was evaluated by means of AMPHITOX test. Embryos at 25 stage of development (acute test) and embryos at 2-4 blastomers stage (early life stage test), were exposed to phenol solutions in concentrations ranging from 25 to 250 mg/L, which were frequently found in the environment. Mortality and malformations were registered each 24h. LC(50), LC(99), NOEC, TC(50) and TI(50) values were 183.70, 250, 60, 113 mg/L and 1.62, respectively, at 96 h of treatment. Mortality and the percentage of malformations increased with increasing phenol concentrations. Teratogenic effects more frequently produced by phenol were: axial flexure, persistent yolk plug and different abnormalities which caused death of blastulae. Moreover, other malformations were registered, such as irregular form, acephalism, edema, axial shortening and underdevelopment of gills, among others. Larvae of B. arenarum, at early embryonic stages (blastulae), showed higher sensitivity to phenol than tadpoles at stage 25. Results confirm high susceptibility of amphibians to phenol and that environmental concentrations of this pollutant might be harmful to these populations.