Trace Metals and Polycyclic Aromatic Hydrocarbons in an Urbanized Area of Florida

Contamination of soils by a variety of pollutants in urbanized and rapidly urbanizing regions is an ongoing problem in the world. Our objective in this study was to determine the contamination levels of trace metals and polycyclic aromatic hydrocarbons (PAHs) in urban residential soils. Surface (0-15 cm) samples of soils were collected and analyzed from an urbanized region of Florida (Pinellas County: 725 km2, population: 921,482), for basic soil properties, trace metals, and PAHs. The pH of urban residential soils was between 5.4 and 8.0, the electrical conductivity ranged from 18 to 1170 S cm-1 with an average value of 233 S cm-1, and total organic carbon of soils varied widely from 1 to 88 g kg-1. Among the major elements determined in soils, contents of Mehlich 1 (M1) Ca were highest at 2330 mg kg-1 followed by M1-Mg (136 mg kg-1) and M1-Al (135 mg kg-1). Among the trace metals in soils, mean M1-Zn values were highest (18.6 mg kg-1) followed by M1-Fe (10 mg kg-1) and M1-Mn (8.6 mg kg-1). The contents of total PAHs (sum of the individual 14 PAHs) in urban residential soils varied from 83 to 2371 g kg-1, with a mean value of 731 g kg-1. Source analysis of PAHs in soils using molecular diagnostic indices suggested that PAHs in soils originated from both petrogenic and pyrolytic sources. Our results can be used to set baseline values of PAHs in urban residential soils of Florida and monitor changes in soil metals and PAHs values over a period of time due to anthropogenic inputs.