The use of N HNO3 to determine copper and zinc levels in heavy-metal polluted tropical soils

This study compared N HNO₃ to other methods to determine plant available heavy metals in heavy-metal polluted soils. Soil samples were obtained from an experimental field treated with industrial waste after 22 years of the amendment and employed to conduct the comparative and correlation study. Soil samples were analyzed for Cu using various methods, planted in a glass house with several plants, and analyzed for soil and plant Cu and Zn. The relative strength of the chemical extractants followed the order of N HNO₃ ≈ N HCl > Buffered DTPA ≈ Unbuffered DTPA > M CaCl₂ ≈ N NH₄OAc pH 7. A high correlation was observed for soil extracted Cu by M CaCl₂ or N NH₄OAc pH 7 or N HCl vs. Buffered DTPA and N HNO₃ or N NH₄OAc pH 7 vs. N HCl. High correlations of plant and soil Cu extracted by N HNO₃ were shown by caisim, water spinach, land spinach, and corn, while plant and soil Zn were shown by caisim, water spinach, land spinach, and lettuce.