Depth distribution of aluminum and heavy metals in soils of Costa Rican coffee cultivation areas

Depth distributions of metals in soil profiles are indicative of weathering and soil genesis and anthropogenic pollution. We studied the depth distribution of total Al, Cd, Cu, Fe, Mn, Pb, and Zn concentrations in 8 Oxisols, 5 Andisols, 2 Mollisols, and 2 Alfisols of coffee plantation areas in Costa Rica. The concentrations of the mainly geo‐/pedogenic Al (means of 76 g kg^—1 in the A horizons and of 106 g kg^—1 in the lowermost sampled B horizons) and Fe (A: 56 g kg^—1, B: 66 g kg^—1) generally increased with profile depth. In spite of the regular application of Cu‐containing fungicides, Cu (A: 135 mg kg^—1, B: 158 mg kg^—1) showed accumulations in the A horizons of only three profiles. Higher Cd (A: 0.14 mg kg^—1, B: 0.09 mg kg^—1) and Pb concentrations (A: 7.3 mg kg^—1, B: 5.5 mg kg^—1) in most topsoils compared to the subsoils indicated anthropogenic inputs. The mean Mn (A: 1190 mg kg^—1, B: 1150 mg kg^—1) and Zn (A: 59 mg kg^—1, B: 66 mg kg^—1) concentrations varied little with depth. In general, the metal depth distribution in the studied tropical soils was similar to that of temperate soils although the weathering regime is quite different.