Humic acids are the most active components of soil organic matter and have been shown to have an hormone-like activity thus stimulating plant growth. The objective of this work was to verify the quantitative and qualitative yield responses of the table grape cv. Italia after the application of a humic acid at various phenological stages. The humic acid used in this study has been extracted from...

The goal of these studies was to determine how sorption by humic acids affected the bioavailability of polynuclear aromatic hydrocarbons (PAHs) to PAH-degrading microbes. Micellar solutions of humic acid were used as sorbents, and phenanthrene was used as a model PAH. Enrichments from PAH-contaminated soils established with nonsorbed phenanthrene yielded a total of 25 different isolates represe...

INTRODUCTION The origin of the humic acid fraction of soils is still unclear in spite of extensive investigations accomplished over the last years (ref. 1). Different origins have been proposed, based on the most recent theory or on the applica­ tion of the latest analytical method. Thus, it has been proposed that soil humic acids are derived from lignins, microbial activity and synthesis of me...

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...

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...

Two soil humic acids (HA), a marine sediment HA, and a soil fulvic acid (FA), were fractionated by polyacrylamide gel electrophoresis in the presence of denaturing agents before and after 6N HCl hydrolysis. After acid hydrolysis, the intensity of the high molecular size (MS) fraction decreased considerably in all HAs. On the other hand, a new high-MS fraction appeared in the FA after hydrolysis...

Plug-flow biofilm reactors colonized by microorganisms in streamwater were used to measure the concentration and composition of biodegradable dissolved organic C (BDOC) in White Clay Creek. During the 4-month study period, DOC ranged from 0.8 to 10.4 mg C liter-’ and was, on average, composed of 75% humic substances, 13% carbohydrates, 2% amino acids, and 18% > 100 kDa. The carbohydrates were p...

The interaction of sulfonamide antimicrobial agents with smectite clay minerals and humic acid (HA)-clay complexes was investigated in batch experiments to assess the influence of adsorbed humic acid on sulfonamide sorption. Soil HA-clay complexes were produced at HA:clay ratios of 1:5, 1:50, and 1:100 (w/w). Vibrational and electronic spectroscopy indicated the preferential adsorption of polar...

The sea-surface microlayer (SML) has different physical, chemical and biological properties compared to the subsurface water, with an enrichment of organic matter i.e., dissolved organic matter including UV absorbing humic substances, fatty acids and many others. Here we present experimental evidence that dissolved organic matter, such as humic acids, when exposed to sunlight, can photosensitiz...

Four types of soil (red, yellow, cinnamon, and paddy soil) from China were used to conduct experiments in pots to study the influence of humic acid (humic acid (HA) and fulvic acid (FA)) on the accumulation of lead (Pb) and cadmium (Cd) in tobacco leaves. In non-polluted soils, the tobacco leaf uptake of Cd was dramatically influenced by the total soil metal concentration and soil properties, w...