Influence of Humic Acid on 1-Aminopyrene Ecotoxicity During Solar Photolysis Process

Ana Balarezo,Veleka Jones,Huey-Min Hwang,Hongtao Yu

doi:10.3390/i3111133

Abstract

1-Aminopyrene (1-AP), a polycyclic aromatic hydrocarbons (PAH) compound, is a major metabolite during biotransformation of 1-nitropyrene by microflora in natural environment and in the guts of animals and humans. Under UV-A irradiation, 1-AP has been shown to cause light-induced DNA single strand cleavage. Humic acids (HA) in aquatic ecosystems can influence the bioavailability, toxicity, and fate of organic xenobiotics. Therefore, photochemical fate and effect of PAH in natural aquatic environment may differ significantly across sites. The objectives of this study are to assess the time course (TC; 18 and 90 minutes) influence of HA (0, 20, and 60 ppm) on microbial ecotoxicity of 1-AP (0 and 10 μM) during solar photolysis process (PP). Microbial ecotoxicity of 1-AP during different time courses in the presence and absence of HA was measured with spread plate counting and microbial mineralization of 14C-D-glucose. The experimental results were analyzed as factorial arrangements of treatment in a complete randomized design using General Linear Model by SAS. LSMEANS was used to separate means or combination of means. Significant effect on glucose mineralization was found by the following treatment interactions 1-AP*TC, 1-AP*PP, TC*PP, HA*1-AP*TC, HA*1-AP*PP, and HA*1-AP*TC*PP. The treatment interaction HA*1-AP was the only one affecting spread plate counting. In the groups exposed to 1-AP (10 μM), microbial heterotrophic mineralization of 14C-D-glucose was significantly inhibited in the presence of HA in light and in darkness. Exposure to HA in light and darkness, however, did not necessarily inhibit bacterial viability at the HA concentration range assayed. Therefore, inhibition on microbial activity could have been caused by multiple factors, instead of toxicity of HA alone.

Highlights

Polycyclic aromatic hydrocarbons (PAH) are organic compounds consisting of two or more fused 5and 6-membered rings
The toxic response may be caused by irreversible covalent binding between PAH and the biological substrates or receptors, which results in the production of activated intermediates that can bind covalently to DNA or proteins to form adducts [3]
Some PAH may be bioavailable but nontoxic to aquatic organisms; they may be absorbed by the organisms and photo-transformed in vivo with lethal results [6,7]

Summary

Introduction

Polycyclic aromatic hydrocarbons (PAH) are organic compounds consisting of two or more fused 5and 6-membered rings. They are introduced into natural environment mainly from natural and anthropogenic combustion processes. At the concentrations below their aqueous solubility limits some PAH become more toxic to aquatic organisms in the presence of solar or artificial irradiations [4,5]. Some PAH may be bioavailable but nontoxic to aquatic organisms; they may be absorbed by the organisms and photo-transformed in vivo with lethal results [6,7]. Photolysis constitutes a force which alters the chemical structure, physical properties, concentration, or toxicity of a PAH compound, and may affect its bioavailability. Under UV-A irradiation, 1-AP has been shown to cause light-induced DNA single strand cleavage [12]

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Results