Abstract

ARMADO-MATUTE, Arnaldo José et al. EFFECTS ON BIOCHEMICAL AND BIOLOGICAL BACTERIAL PARAMETERS IN SOILS CONTAINING PERMISSIBLE METAL CONCENTRATIONS. Rev. Int. Contam. Ambient [online]. 2018, vol.34, n.3, pp.441-451. ISSN 0188-4999.  https://doi.org/10.20937/rica.2018.34.03.07.

Contamination of natural environments by metals is basically due to anthropogenic activities such as iron and steel industries, mining, electroplating and tannery. As a consequence, proliferating microbes in such environments are subjected to stress conditions which induce decreases of the microbial diversity and biomass, particularly the bacterial one. This study reports statistical significant reductions of the total organic carbon content (70 %), urease activity (54 %), microbial biomass (47 %), and bacterial load (3080%) in soil samples containing permissible levels of metals according to the Venezuelan legislation. Besides, the basal respiration/microbial biomass ratio increased 58% respect to the witness soil. The bacterial diversity was severally reduced and only 12 bacterial morphotypes were isolated from agar LB plates supplemented with Cr3+, Cr6+, Ni2+, Pb2+, Zn2+, Fe2+, and Co2+ salts. Five of these strains were assigned to Rothia, Vibrio, Klebsiella, Acinetobacter and Raoultella bacterial genera. The pH (9) and metal concentrations (Cr3+, Cr6+ and Ni2+) were the most important parameters involved in reducing the bacterial diversity and load. The reported data should constitute an alarm call to the Venezuelan environmental authority to revise and set the metal permissible levels in natural environments, in such a way the soil biochemical and physiological parameters are not negatively affected; besides, microbial load and diversity should be included as health bioindicators to soils.

Keywords : bacterial diversity; bacterial load; contamination by metals; environmental normative.