Trace Element Composition of Selected Fertilizers Used in Chile: Phosphorus Fertilizers as a Source of Long-Term Soil Contamination

Abstract

Anthropogenic activities like agriculture have resulted in increased concentrations of some trace elements of toxicological and environmental concern in soils. Application of fertilizers has been one of the major inputs of these contaminants to agricultural soils in developing countries. Twenty-two fertilizers, including straight nitrogen (N), phosphorus (P), potassium (K), and NK fertilizers and micronutrient sources, were analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES) for arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), lead (Pb), vanadium (V), and zinc (Zn). As expected, the trace element content of fertilizers was highly variable and related to the origin of the material. Phosphorus fertilizers, especially triple superphosphate, presented the highest As, Cd, Cu, Cr, Ni, V, and Zn concentrations. In some of these fertilizers, the Cr, V, and Zn contents reached values greater than 3475 mg kg⁻¹ of P, and the Cd content (up to 288 mg kg⁻¹ of P) was several times higher than the regulatory limits of different countries. Some micronutrient sources presented the highest concentrations of Mn and Pb. In the cases of N, K, and NK fertilizers, the trace element concentration was very low, sometimes below the detection limits. In some agricultural systems the input of trace elements such as As and Cd to the soil through P fertilizers application may be higher than the outputs through plant uptake and leaching; therefore the long-term use of these fertilizers may cause the trace element concentration to increase in the plow layer of agricultural soils.

Keywords:

• Arsenic
• heavy metal
• mineral fertilizer
• phosphate rock

Acknowledgments

This work was supported by FONDECYT (Chilean Fund for Science and Technology) under project number 1070116 and by project DICYT-USACH 010741CS. Mauricio Molina acknowledges PUC-MECESUP (0210) doctoral scholarship.

Notes

*Data from fertilizer providers’ information. Percentage on a mass basis.

*Data from fertilizer providers’ information. Percentage on a mass basis.

*Assuming P fertilizers with 50% of P₂O₅.

*Detection limit.

*Detection limit; ^†only Zn sources; ^‡only Fe sources.

*Calculated using micronutrient sources composition of Table 2 and regulatory limits in Table 9a.