PAH and PCB in soils of Switzerland—status and critical review

Abstract

The surface soil concentrations (0–20 cm) of the Swiss soil monitoring network (NABO) with 105 observation sites representing all major land use types ranged for the sum of 16 EPA PAH (PAH₁₆) from 32 to 8465 µg kg⁻¹ (median 163 µg kg⁻¹), for benzo[a]pyrene (BaP) from 0.5 to 1129 µg kg⁻¹ (median 13 µg kg⁻¹) and for the sum of seven IRMM PCB (PCB₇) from 0.5 to 12 µg kg⁻¹ (median 1.6 µg kg⁻¹). The legal guide values of Switzerland were exceeded for PAH₁₆ at only three and for BaP at two sites. The PCB₇ concentrations were clearly below any assessment value. The concentration ranges were overlapping between all land use types. Tendencies for higher concentrations were observed at urban and viticulture sites. The overall measurement precision at repeatability conditions ranged from 1 to 37% RSD for PAH₁₆, BaP and PCB₇. The median bias for the chemical analysis was around zero for PAH₁₆, +5% for BaP and −5% for PCB₇ with spreads ranging from less than −20% up to more than +30%. The PAH profiles were clearly dominated by phenanthrene. Stratification by land use revealed a prevalence of benzo[a]pyrene at urban and naphthalene at conservation sites. For PCB, the general congener rank order was PCB no. 153 > 138 > 101 > 180. From a broad correlation screening only PAH₁₆/BaP (r = 0.88**) were relevant for practical soil protection. The extensive comparison with other studies was severely biased by the lack of harmonisation, especially concerning sampling depth, sampling support, analytical method and the sum calculation procedure.