The main objective of the present study was to assess the roles of various soil components in sorption of organic compounds differing in polarity. Removal of the whole soil organic matter decreased sorption by approximately 86% for nonpolar 1,3,5-trichlorobenzene (TCB), but only 34–54% for highly polar 1,3,5-trinitrobenzene (TNB); however, removal of the extractable humic/fulvic acids did not much affect sorption of the two sorbates. With normalization of solute hydrophobicity, TNB exhibits several orders of magnitude stronger sorption compared with TCB to maize burn residue (black carbon), extracted humic acid and Na+-saturated montmorillonite clay, suggesting specific sorptive interactions for TNB with the individual model soil components. It was proposed that sorption of TCB to the bulk soil was dominated by hydrophobic partition to the condensed, non-extractable fraction of organic matters (humin/kerogen and black carbon), while interactions with soil clay minerals were an important additional factor for sorption of TNB. Soil humin and black carbon play a predominant role in sorption of 1,3,5-trichlorobenzene, while polar interactions with soil clay minerals are an important additional factor for sorption of 1,3,5-trinitrobenzene.

Ground-level dynamics of O₃, NO x and benzene, toluene, ethylbenzene and xylenes were characterised at rural sites in the medium Ebro River Basin (Northern Spain) from April to September (2003-2007) and by means of automated and passive monitoring. The study registered high O₃ levels within the area, which were influenced by traffic emissions, and a monthly evolution of these levels consistent with the occurrence of a broad summer maximum, typical of polluted areas. The mean ozone concentration registered in the studied area by means of passive sampling was 87 ± 12 μg m⁻³. The 2008/50/EC objective value for the protection of vegetation was widely exceeded during this study (AOT40 = 57,147 ± 14,114 μg m⁻³ h), suggesting that current ambient levels may pose a risk for crops and vegetation in this important agroindustrial region.