Soils may be contaminated by human or veterinary pharmaceuticals. Their behaviour in soil environment is largely controlled by sorption of different compounds in a soil solution onto soil constituents. Here we studied the sorption affinities of 4 pharmaceuticals (atenolol, trimethoprim, carbamazepine and sulfamethoxazole) applied in solute mixtures to soils taken from different horizons of 3 soil types (Greyic Phaeozem on loess, Haplic Luvisol on loess and Haplic Cambisol on gneiss). In the case of the carbamazepine (neutral form) and sulfamethoxazole (partly negatively charged and neutral), sorption affinity of compounds decreased with soil depth, i.e. decreased with soil organic matter content. On the other hand, in the case of atenolol (positively charged) and trimethoprim (partly positively charged and neutral) compound sorption affinity was not depth dependent. Compound sorption affinities in the four-solute systems were compared with those experimentally assessed in topsoils, and were estimated using the pedotransfer rules proposed in our previous study for single-solute systems. While sorption affinities of trimethoprim and carbamazepine in topsoils decreased slightly, sorption affinity of sulfamethoxazole increased. Decreases in sorption of the two compounds could be attributed to their competition between each other and competition with atenolol. Differences between carbamazepine and atenolol behaviour in the one- and four-solute systems could also be explained by the slightly different soil properties in this and our previous study. A great increase of sulfamethoxazole sorption in the Greyic Phaeozem and Haplic Luvisol was observed, which was attributed to elimination of repulsion between negatively charged molecules and particle surfaces due to cation sorption (atenolol and trimethoprim) on soil particles. Thus, our results proved not only an antagonistic but also a synergic affect of differently charged organic molecules on their sorption to soil constituents.

The objectives of this study are to test the penetration depth and determine the soil content in hydrocarbons’ components BTEX, PAHs, and TPH, after vertical movement of crude oil through undisturbed soils of different textures, and to assess their risk. The experiment simulates the fate of oil spills in the cold season. Three soil types were investigated: a sandy-textured eutric Arenosol, AR-eu; a loamy-textured haplic chernozem, CH-ha; and a clayey-textured, swell-shrink, Luvic Chernic Phaeozem, PH-ch-lv. Undisturbed small-scale lysimeters, 0.3 m in diameter and 1 m in length, were used. Crude oil was first applied and then water. TPH, BTEX, and PAH retention in the soils depends on soil texture. PH-ch-lv soil stored most of them in the upper horizons. TPH, BTEX, and PAH were found in different amounts as percentage from the applied ones, TPH as 48% (PH-ch-lv), and > 76% in the other two soils. BTEX was stored as 1.6% from the applied in PH-ch-lv, 5.1–5.1% in CH-ha and AR-eu soils, while PAH ranged from 15.1% in AR-eu soil to 24.8% in PH-ch-lv and 31% in CH-ha. Though subject to volatilization, chemical transformation, and bioremediation, TPH, BTEX, and PAH stored in soils present a health risk if they reach the groundwater. PH-ch-lv appears to be the most resilient soil to oil pollution. The results concern different soil textures and might be used in various countries. Future experimentation should focus on soil behavior in relation to crops, water, and certain crude oil types.

Soil organic matter (SOM) is the main adsorbent for polycyclic aromatic hydrocarbons (PAHs) and the principal aggregating agent for soil aggregation that can affect PAH bioavailability and bioaccessibility in soils. The objective of this study was to analyze the relationship between PAH dissipation and variation in soil aggregate–size distribution in two field-contaminated soils with different soil organic C (SOC) content (Anthrosols, 1.41% SOC; Phaeozems, 8.51% SOC) in phytoremediation with alfalfa. The results showed that there were significant reductions of 10.2 and 15.4% of the total PAHs in unplanted and planted treatments, respectively, for Anthrosols. However, there was no significant reduction of total PAHs in either unplanted or planted treatment for Phaeozems. For Anthrosols, mass percentages of coarse sand and fine sand were significantly reduced while coarse silt and fine silt were significantly increased for the planted soil compared to the initial soil (p < 0.05). For Phaeozems, there was no significant variation in aggregate–size distribution among different treatments except that coarse silt in planted and unplanted soil was slightly reduced. The main reason for the dissipation of PAHs in Anthrosols could be that macroaggregates were broken into microaggregates, which made some trapped PAHs become bioaccessible to soil microorganisms.

Pot experiments were used to compare the dissipation and phytoremediation effect of alfalfa (Medicago sativa L.) for polycyclic aromatic hydrocarbons (PAHs) in a freshly spiked soil and two field-contaminated soils with different soil organic carbon (SOC) contents (Anthrosols, 1.41% SOC; Phaeozems, 8.51% SOC). In spiked soils, the dissipation rates of phenanthrene and pyrene were greater than 99.5 and 94.3%, respectively, in planted treatments and 95.0 and 84.5%, respectively, in unplanted treatments. In field-contaminated Anthrosols, there were limited but significant reductions of 10.2 and 15.4% of total PAHs in unplanted and planted treatments, respectively. In field-contaminated Phaeozems, there were no significant reductions of total PAHs in either unplanted or planted treatments. A phytoremediation effect was observed for the spiked soils and the Anthrosols, but not for the Phaeozems. The results indicated that laboratory tests with spiked soils cannot reflect the real state of field-contaminated soils. Phytoremediation efficiency of PAHs in field-contaminated soils was mainly determined by the content of SOC. Phytoremediation alone has no effect on the removal of PAHs in field-contaminated soils with high SOC content.

Behaviors of BDE-28 and BDE-47 in two distinct soils (Phaeozem and Acrisol) as affected by the separate addition of root exudate components (i.e., oxalic acid, glycine, and fructose) were investigated by a soil microcosm incubation experiment. The results showed that root exudate components promoted the desorption of BDE-28 (57.6–235.0 %) and BDE-47 (56.9–223.7 %) from the soils due to the enhancement of their water solubilities. The addition of root exudate components increased the n-butanol extractability of BDE-28 and BDE-47 by 20.3–72.5 and 48.6–169.2 %, respectively, which had a positive correlation with the concentrations of dissolved organic carbon (DOC) in the soils (p < 0.01), suggesting that the increase of DOC in the soils by root exudate components was the major factor to enhance the extractability. Fructose and oxalic acid promoted the desorption and increased the availability of BDE-28 and BDE-47 in the soils more efficiently than glycine. The addition of different root exudate components resulted in distinct shifts in soil microbial community structure (p < 0.05). Oxalic acid caused the greatest impacts on the soil bacterial communities and increased the degradation rates of BDE-28 and BDE-47 most obviously. The findings of this study clarified the roles of root exudate components in affecting the behaviors of polybrominated diphenyl ethers (PBDEs) in soils.