Influence of humic acid on nile tilapia exposed to cadmium pollution

The effect of humic acid on cadmium [Cd] toxicity to Nile tilapia and the impact on fish immunological, hematological changes in Nile tilapia [Oreochromius niloticus] were studied. The fish [120 +/- 10g] were exposed to 10 ppm Cd alone or with 0.2, 0.3 and 0.4 g humic acid /I ppm for 15 and 45 days. Cd exposure reduced significantly [P<0.04] such as erythrocyte count [RBCs], haemoglobin content [Hb], haematocrit value [Hct], mean cell haemoglobin [MCH] and mean cell haemoglobin concentration. These parameters were improved when humic acid was applied with Cd. The values of RBCs, Hb, Hct, MCH and MCHC were increased significantly to be as in the control fish group. Addition of humic acid to Cd contaminated medium considerably reduced metal absorption and accumulation in fish tissues, while it was increased metals in water and feces. Fish exposed to Cd alone accumulates 2.15 and 5.970 mg Cd/g dry weight in liver tissue for 15 and 45 days respectively. Cd reduced significantly to 1.292 and 4.16.; 0.92 and 3.791; and 0.41 and 2.43 mg Cd/g dry weight tissue in fishes exposed to 0.2, 0.3 and 0.4g humic acid /I for 15 ; and 45 days, respectively. Similar trends were observed in gills and musculature

Adsorption of adenine on soil humic acids

Adsorption of adenine on an Eutric fluvisol humic acid and a Cambisol clay-humic acid complex was studied at four temperatures between 35 and 41C. Adenine showed high affinity towards the two adsorbents giving H-type isotherms at all temperatures. Though, the degree and intensity of adsorption decreased at increasing temperature. The adsorption on the humic acid proceeded probably through an electron- donor-acceptor mechanism. The adsorption mechanism[s] on the clay- humic acid complex was more complicated, since the surface of the complex is composed of the two heterogenous substances, humic acid and two- and three-layer clay minerals. It could be concluded that, if humic acid[s] enter living cell, it would harmfully affect cell growth