Redistribution metals and nutrients by fire ants in a flue dust contaminated pasture
1993
Davis-Carter, J.G. | Sheppard, D.C.
Flue dust was disposed of by land application as a source of micronutrients for crops, resulting in unusually high heavy metal (Zn, Pb, Cr and Cd) concentrations in the soil. We determined whether fire ants accumulate or avoid heavy metals and nutrients in their mounds and evaluated whether this accumulation or avoidance is due to accumulation of specific soil textural classes in mounds by the fire ants. A bahiagrass pasture was chosen where flue dust had been applied in the early 1980s. Eighteen fire ant mounds were sampled to an approximate depth of 10-15 cm, and 10 fire ant mounds were sampled to 45 cm deep in 15 cm increments. In both surveys, an area 3 m north of each mound was sampled as a control. Statistical analysis was achieved using the paired t-test. Sand content was significantly lower in mounds, and clay content was significantly higher in mounds than in control areas. K and Mg concentrations were significantly higher in shallow mound samples than in control areas of corresponding depth; however, P and Zn were significantly lower in mounds than in control areas. K concentrations were significantly higher in mounds in the 0-15, 15-30 and 30-45 cm depths. The increases in K and Mg concentrations can be accounted for by the accumulation of clay in the mounds since cations bind to negatively-charged clay particles. Dilution with material transported by the ants from the subsoil, where metal and nutrient concentrations are lower, does not fully explain why P and Zn concentrations were lower in mounds than in control areas. Fire ants may have actively avoided Zn during mound construction.
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