Over at least twelve years of actual field experience with an ample variety of humic acid formulations (some of them developed many years before) have given us a singular degree of expertise in Latin America and a few other markets. Among other things, we have learned to distinguish between humic acids of high biological value, and humic substances of little biological activity. We have found c...

Mobile and potentially mobile forms of heavy metals are probably one of the most important toxic hazards in the environment. Besides pH, which is a factor influencing the mobility/availability of heavy metals to the greatest extent, the content and mainly the quality of soil organic matter play a very important role in the evaluation of heavy metal behaviour in the environment. The fraction of ...

Two aquatic fulvic acids and one soil humic acid were irradiated to examine the resulting changes in the redox and photochemical properties of the humic substances (HS), the relationship between these changes, and their relationship to changes in the optical properties. For all HS, irradiation caused photooxidation, as shown by decreasing electron donating capacities. Photooxidation was accompa...

The Paenibacillus sp. strain PAMC 26794 was isolated from the tundra grasslands in Alaska for its high ability to degrade humic acids. We sequenced the PAMC 26794 genome to discover the degradative genes for natural humic substances and we propose the degradation pathway(s) of an abundant bacterial group (genus Paenibacillus) that inhabits cold environments.

Decomposition of humic substances (HSs) is a slow and cryptic but non-negligible component of carbon cycling in sediments. Aerobic decomposition of HSs by microorganisms in the surface environment has been well documented; however, the mechanism of anaerobic microbial decomposition of HSs is not completely understood. Moreover, no microorganisms capable of anaerobic decomposition of HSs have be...

The present study examines the role of humic acid, as a representative of dissolved organic matter, in Cd(II), Cu(II), and Pb(II) speciation and biouptake by green microalgae. Cellular and intracellular metal fractions were compared in the presence of citric and humic acids. The results demonstrated that Cd and Cu uptake in the presence of 10 mg L(-1) humic acid was consistent with that predict...

Experiments in batch equilibrium system were carried out to evaluate the importance of physical and chemical factors determining the sorption efficiency of humic substances (HS) on aquifer material, which has been used for artificial recharge of groundwater (ARG) in drinking water production. Results showed that an increase of the amount of clay in the aquifer material and a decrease of pH in w...

The mechanisms underlying the use of insoluble electron acceptors by metal-reducing bacteria, such as Shewanella oneidensis MR-1, are currently under intensive study. Current models for shuttling electrons across the outer membrane (OM) of MR-1 include roles for OM cytochromes and the possible excretion of a redox shuttle. While MR-1 is able to release a substance that restores the ability of a...