Investigation of Heavy Metals using Various Extraction Methods in Livestock Manures

Abstract

The use of animal waste for a soil amendment is a viable option for waste management. For safe and sustainable management of waste, it is important to assess the concentrations of heavy metals (HM). An experiment was conducted to compare metals [copper (Cu), zinc (Zn), and manganese (Mn)] in cow manure (CM), duck litter (DL), poultry litter (PL), and poultry litter ash (PLA) using eight extraction solutions. Extractability of HM was highly dependent upon the type of waste as well as extracting agent. Manures differed for the release of HM in the order of PL > DL > CM. Marked decreases in extractable trace elements were observed after ashing of PL irrespective of extraction method. Except for water, extractions released HM in the order of Mn > Cu > Zn. For Zn and Mn, the amount extracted varied in the order 1 M nitric acid (HNO₃) > 0.1 M HNO₃ > 0.01 M HNO₃ ≈ ethylenediaminetetraacetic acid (EDTA) > ammonium nitrate (NH₄NO₃) > calcium chloride (CaCl₂) > ammonium acetate (NH₄OAc) > H₂O in PL and PLA. Peak concentration of Cu was achieved in 1 M HNO₃ solution and the lowest Cu was found in NH₄OAc solution. On the basis of these results, the low extractability of HM in ash could suggest that the use of burned PL would be less of a water-pollution problem in the fields.

Keywords:

• Animal waste
• extraction methods
• trace elements

Acknowledgment

We acknowledge the financial support of Japanese Ministry of Education, Science, Sports and Culture (Monbusho) for this research via Tottori University Japan.