Abstract
The structure of soil particles, which serves as the fundamental unit of soil, is crucial for plant growth. Human activities on land use have significantly impacted soil structure and led to the contamination of heavy metals in the soil. This research aimed to investigate the heavy metal contamination in soil across six different land use categories: agricultural zone, rural zone, commercial zone, and three classifications of urban areas based on their density—high-density residential zone, medium-density residential zone, and low-density residential zone. Soil samples were collected from 50 districts in Bangkok, resulting in a total of 150 samples obtained at a depth of 0-5 cm between October-November, 2020. These samples were analysed for six heavy metals—Cadmium (Cd), Chromium (Cr), Copper (Cu), Nickel (Ni), Lead (Pb), and Zinc (Zn)—using an Atomic Absorption Spectrometer (AAs). The findings revealed that the average levels of heavy metal contamination were as follows: Pb > Cr > Zn > Cu > Ni > Cd with concentrations of 47.10±23.20, 20.66±7.53, 11.58±6.06, 8.63±6.92, 6.50±7.91, and 0.56±0.36 mg/kg. Pb and Cr exhibited the highest levels of contamination in commercial zone, urban zone, and rural zone, while Cr and Cu were most prominent in agricultural zone. The concentrations of heavy metals in Bangkok soil did not exceed the standard limits for heavy metal contamination in residential and agricultural soils, as outlined by the National Environment Board Notification.
