Epsilon Archive for Student Projects

Abstract

This study determined and evaluated soil properties and distribution of biogenic
(copper, iron, manganese and zinc) and non-biogenic (arsenic, cadmium, chromium,
nickel, lead and wolfram) trace metals in the road side topsoil (0-10 cm) and subsoil
(10-20 cm) at six sites in Uppsala City. The hypothesis of the study was that
depending on the, location traffic intensity, history and industrial activities soil
contents of the metals vary regardless of similar bedrock.

Four composite samples 20 m apart were taken 10 m from the roadside. Soil texure
was detemined by the pipette method, total C on Leco CNS-200 equipment, chemicals properties (cation exchange capacity (CEC) in BaCl2 solution at pH 8.1, pH in deionised H2O and in calcium chloride solution and metals by digestion in aqua regia and measuring on ICP-MS equipment.

The soils were characterized mainly as sandy clay loams and the pH was nearly
neutral. The CEC ranged between 10.6 and 37.9 c mol kg-1, with a mean of 20.0 c
mol kg-1 . Percentage base saturation was below 100.

The biogenic trace metals were evenly distributed in both the topsoil and subsoil,
whereas the pattern for non-biogenic metals was not consistent. The results of
biogenic metals were lower than the limits set by the Swedish Environmental Code,
whereas some of the non-biogenic metals were close to the limits. The distribution of
non-biogenic metals may suggest anthropogenic source of metals.

Metal accumulation, especially Pb, Cd, and Ni did not conform to trends of traffic
intensity; rather it tended to follow the age of the road. Thus, although the E4
highway (relatively young road) with traffic density of 25000-40000 per d, Pb
accumulation was not as high as Pb determined on the roadsides of Kungsgatan, the
oldest street in central Uppsala with traffic intensity of 15000-20000 per day.
Surprisingly the soil were enriched with W. Some of the metal contents could in the
long term enhance health and environmental concerns, especially at school and
children's day centres located close to the roadsides, where the risk of repeated
exposure is apparent. More investigations are justified to verify these risks.