Industrial discharge

Choose Your Own Adventure With Zinc Legend Where you can go Where you have been Where you are Immediate interactions Industrial discharge Animal accumulation Air Human uptake Rainfall Fertilizers Pesticides Surface water Plant and animal residue, microbial pool Plant uptake Minerals: Spharelite, Zincite, etc. Soil Organic Matter Highly soluble compounds: Hydroxides Carbonates Silicates Chlorides Sulfates Phosphates Adsorption Complexation Precipitation SOIL CLAYS: Muscovite Illite Chlorite Montmorillonite Kaolinite Adsorption Zn2+ and chelates Available at pH < 7.7 + H2PO4 or nNO3 Complexation + nCl Complexation + nH2O Phosphate and Nitrate Complexes Hydrolysis Species Chloride Complexes Main Cycle More Info Click on an object and follow the arrows to choose your own adventure within the Zinc cycle

More Info on Zinc Back to Main Cycle Back to More Info Concentration in soils Form taken up by plant Mobility in soil Origin in soils Mobility in plants Effect of pH on availability Deficiency found in Interaction of Zn with other nutrients Toxicity symptoms Fertilizer sources Role of Zn in the plant Soil test Role of Zn in microbial growth References Concentration in plants

More Info on Zinc Back to Main Cycle Back to More Info Form taken up by plant: Zn2+ at pH < 7.7; Zn(OH)+ at pH > 7.7 (less available to plants). Mobility in soil: No (Low solubility): Soluble by chelation by mobile ligands. Highly soluble at pH < 6. Mobility in Plants: Low: Mobility in plants does not coincide with water flow. Zn is absorbed by plants as Zn2+ and transported as citrate, malate and malonate complexes.

More Info on Zinc Back to Main Cycle Back to More Info • Deficiency found in: • Acidic, sandy soils with high leaching, calcareous • soils pH>8.0, exposed subsoil horizons (erosion), • Deficiency symptoms are purple margins similar to • phosphorus deficiency, but also inward toward the • center of leaves (purple blotching), and brown spots • on rice leaves. Deficiency is rarely observed in • wheat. Zn deficiency can be corrected by application • of 2.5-25 kg/ha of ZnSO4 (depending on soil pH and • texture) or 0.3-6 kg/ha as chelates in broadcast or • band application. Foliar application of 0.5-2.0% • ZnSO4*7H2O effective for fruit trees for the growing • season; 2% solution is used for seed soaking. Soil • application corrects Zn deficiency for 2-5 years.

More Info on Zinc Back to Main Cycle Back to More Info • Toxicity symptoms: • Most plant species have high tolerance to excessive • amounts of Zn. However, on acid and heavily sludged • soils Zn toxicity can take place. Zn toxicity symptoms • as follow: Inhibited root elongation, photosynthesis in • leaves, depresses RuBP carboxylase activity, chlorosis • in young leaves due to induced deficiency of Fe2+ and/or • Mg2+. Zn2+ has ion radius similar to Fe2+ and Mg2+, • which creates unequal competition for these elements • when zinc supply is high. The critical toxicity level in • leaves is 100-300 mg per kg of dry weight.

More Info on Zinc Back to Main Cycle Back to More Info • Role of Zn in the plant: • 1. Component of ribosomes. • 2. Carbohydrate metabolism • a) a cofactor of carbonic anhydrase, which • converts CO2 into HCO3- • b) activity of photosynthetic enzymes: ribulose • 1,5 bisphosphate carboxylase (RuPPC) • c) Chlorophyll content decreases and abnormal • chloroplast structure occurs when Zn is deficient • d) Sucrose and starch formation by activating • aldolase and starch synthetase • 3. Protein metabolism: Stabilizes DNA and RNA structures • 4. Membrane integrity: Stabilizes biomembranes and • neutralizes free oxigen radicals, as a part of • superoxide dismutase • 5. Auxin metabolism: Controls tryptophane synthetase, • which produces tryptophane, a source for IAA • 6. Reproduction: Flowering and seed production are • depressed by Zn deficiency.

More Info on Zinc Back to Main Cycle Back to More Info • Role of Zn in microbial growth: • Indispensability of Zn in metabolism of living organisms, • microflora also is highly dependent on concentrations • of zinc present. Some heterotrophs can tolerate high • concentration of Zn and behave as bioaccumulators of • Zn, among them Zoogloea-producing bacteria, • Ephiphytic bacteria, Nonsporing bacteria. Different • genera of Green Algae respond differently to Zn • contamination. Microspora, Ulothrix, Hormidium, and • Stigeoclonium are resistant to high Zn concentrations, • whereas genera such as Oedogonium and Cladophora • are rather sensitive to the presence of Zn.

More Info on Zinc Back to Main Cycle Back to More Info • Concentration in plants: • Depending on genotype, Zn concentration varies in the • range 25-150 ppm (0.0025-0.015% of dry weight) of Zn • sufficient plant. • Concentration in soils: • 10-300 ppm (0.001-0.03%). Concentration of total Zn • increases with depth, whereas extractable Zn content • decreases. Concentration of Zn in the upper horizon • also depends on organic matter content, which can • hold up to 13% Zn. In soils, 30-60% Zn can be found • in iron oxides, 20-45% in the lattice of clay minerals, • and 1-7% on clay exchange complex. Highest Zn • concentration is in solonchaks – saline soils in Asia, • lowest in light textured soils with low organic matter.

More Info on Zinc Back to Main Cycle Back to More Info • Origin in soils: • Zinc composition of soils defined by parent material. • Magmatic rocks have 40 and 100 mg/kg Zn in granites • and basalt, respectively. Sedimentary rock composition • varies in the range 10 to 30 mg/kg in sandstones and • dolomites, and 80-120 mg/kg in clays, • Effect of pH on availability: • pH is the most important parameter of Zn solubility. • General equation for soil Zn is pZn = 2pH – 5.8 • The form of Zn predominant at • · pH<7.7 – Zn2+ • · pH>7.7 – ZnOH+ • · pH<7.7 – Zn(OH)2

More Info on Zinc Back to Main Cycle Back to More Info • Interaction of Zn with other nutrients: • Increase in available P content can considerably • decrease availability of Zn in the soil due to the • high antagonism between these two elements. • However, some authors suggest that symptoms • considered as a Zn deficiency are actually P toxicity. • Presence of other nutrients such as iron, copper, • manganese and calcium may also inhibit Zn uptake • by plants, probably due to the competition for the • carrier sites on roots. Application of high rates of • NPK fertilizers can aggravate Zn deficiency.

More Info on Zinc Back to Main Cycle Back to More Info • Fertilizer sources: • Zinc sulfate with 25-36%Zn, Zinc oxide – 50-80% Zn, • Zinc Chloride - 48% Zn, Zinc Chelate – 9-14.5% Zn, • and manure are used in agriculture. • Soil Test: • For available Zn determination four extractants are • generally used: • 0.1M HCL, EDTA-(NH4)2CO3, • Dithizone - NH4OAC, and DTPA-TEA. • Soil content of Zn of 2ppm (0.0002%) and higher are • sufficient for most of the crops, <2 ppm is deficient • for pecans, <0.8 ppm is deficient for corn. When Zn • concentration is less than 0.3 ppm, deficiency • symptoms are observed in less sensitive crops such • as cotton, wheat, soybean, etc.

More Info on Zinc Back to Main Cycle Back to More Info References: Allowey, B.J. (ed.). 1990. Heavy Metals in Soils. John Wiley and Sons. New York. Johnson, G.V., W. R. Raun, H.Zang, and J.A. Hattey. 1997 Oklahoma Soil Fertility Handbook. 4th ed. Department of Agronomy Oklahoma State University. Kabata-Pendias, A., H. Pendias. 1991. Trace elements in soils and plants. 2nd ed. CRC Press Boca Raton Ann Arbor London. Nriagu, J.O. (ed.). 1980. Zinc in the Environment. John Wiley and Sons. New York. Prasad, R., and J.F. Power. 1997. Soil Fertility Management for Sustainable Agriculture. CRC Press LLC. New York. Raun, W.R., G.V. Johnson, R.L. Westerman. 1997. Soil - Plant Nutrient Cycling and Environmental Quality. Oklahoma State University. Robson, A.D. (ed.). 1993. Zinc in Soils and Plants. Kluwer Academic Publishers. Australia. Marschner, H. 1995. Mineral Nutrition of Higher Plants. 2nd ed. Academic Press. London. Tisdale, S.L., W.L. Nelson, J. D. Beaton, and J.L. Havlin. 1993. Soil Fertility and Fertilizers. 5th ed. MacMillian. USA. Authors: Francisco Gavi, Chad Dow, John Ringer, Erna Lukina, and Jon-Karl Fuhrman

Industrial discharge