Distribution of biogenic and non-biogenic trace metals in roadside soils. : a study of Uppsala city, Sweden.

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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 hea...