Abstract:
Triple Super Phosphate (TSP) is one of the fertilizers applied to overcome the phosphorus
deficiencies in agricultural soils. Application of TSP fertilizer may be one of the major inputs of
metal impurities contaminants to agricultural soils in Sri Lanka. This might result in imbalance
structure of trace metals in soils leading to toxicity problem, where these toxic trace metals can
enter to the human body easily through the food chain. The present study was focused on
determining the metal impurities in commonly used TSP fertilizers in Sri Lanka. Two TSP samples
obtained from two Fertilizer Companies (A and B) were selected for the study. Six replicates of each
company fertilizers were digested using the method of the Association of Official Agricultural
Chemists. The concentration of eleven trace metals (Cr, Mn, Cu, Cd, Pb, Zn, Fe, Ni, Co, Mo and As) in
each TSP fertilizers were determined by ICP-OES as an analytical technique. ICP-OES analysis
revealed a group of non-lethal metal species, present as impurities. The highest average
concentrations were, 4229.30 mg of Fe, 469.16 mg of Mn , 195.34 mg of Zn, 8.73 mg of Ni , 7.78 mg
of Cu, 2.36 mg of Co and 1.39 mg of Mo per kg-1 of fertilizer. Considerable amount of toxic heavy
metals such as Pb, Cr, As and Cd were detected with average concentrations of 53.93 mg of Pb,
25.56 mg of Cr, 3.19 mg of As, 1.05 mg of Cd per kg -1 of fertilizer, respectively. Trace metal
concentrations of two fertilizer companies were compared using two sample t –test (α = 0.05).
Metal concentrations of Mn, Cu and Zn were significantly higher in company A fertilizer samples
than those of the company B. Concentrations of Cr, Cd, Pb, Fe, Co and Mo were significantly lower in
company A fertilizer samples than those of the company B. However, there was no significant
differences in concentrations of Ni and As content in fertilizer samples of company A and company
B. Present study explores that concentration of trace metals in TSP fertilizers were highly varied
related to the TSP fertilizer companies. At present, no regulatory limits are available for the
maximum amount of trace metals present in TSP fertilizer in Sri Lankan conditions. Protocol or an
act to regulate the standard limits of metal impurities present in TSP fertilizers is highly
recommended.