Phytoextraction of zinc from soils
Phytoremediation is a tool that uses plants that can absorb and accumulate metals in harvestable portions of the plant to cleanse contaminated soils. Most metals are more soluble in soils with an acidic pH. Nitrogen fertilizers acidify pH by different reactions in the soil. Goals of this research were: (1) develop a zinc-contaminated soil; (2) determine effects of nitrogen fertilizers on soil-zinc availability; (3) determine Zn-phytoextraction potential of Brassica juncea Czern. and Festuca arundinacea Schreb.; and (4) determine concentrations of nitrogen fertilizers needed to maximize Zn solubility in soils.
After a 14-day incubation period, very little Zn in the soil was water-extractable, which suggested that Zn was reacting with the soil; therefore, an incubation time of 14 days was utilized. Morgan's solution, extracted higher concentrations of Zn than water. If soils were sequentially extracted with water, Morgan's solution, and Mechlich-3 solution, water extracted the least amount of Zn, Morgan's solution extracted higher concentrations than water or Mehlich 3, but Mehlich 3 extracted higher concentrations than water.
Lowest pH values occurred with additions of urea (pH 5.18), sludge (pH 4.89), or calcium nitrate (5.26) than with compost (pH 5.33), manure (pH 5.50), or no fertilizer (pH 5.40) or if N was supplied at 400 mg/kg (pH 4.91).
Brassica did not germinate well or survive in soil-Zn concentrations greater than 125 mg/kg. Soil-Zn concentrations utilized with brassica were 0 to 100 mg/kg. Highest accumulation of Zn was 0.29% of the dry mass, which occurred at 100 mg Zn/kg or in soils with urea added. Water-extractable Zn at this level averaged 1.1 mg/kg and Morgan's extractable Zn averaged 18 mg/kg.
Fescue germinated well in soil-Zn concentrations ranging from 0 to 2000 mg/kg. The soil-Zn concentrations utilized with fescue were 0 to 1000 mg/kg. Highest accumulation of Zn by fescue was 0.33%, which occurred at 1000 mg Zn/kg or in soils with urea or sludge added. Water-extractable concentrations of Zn at this level averaged 11 mg/kg and Morgan's extractable Zn concentrations averaged 290 mg/kg. This research showed that fescue has phytoremediation potential that is as good or better than that of brassica.
0481: Soil sciences
0768: Environmental science