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The leakage of pharmaceuticals present in soils towards groundwater is largely controlled by sorption of those compounds in soils. In some soils, soil aggregates are covered by coatings, which may have considerably different composition in comparison to that in an inner part of the aggregates. The aim of this study was to evaluate the sorption of three pharmaceuticals, which were applied in single or all compounds solutions, onto soil samples taken from the Bt horizon of a Haplic Luvisol. Analyses were performed on three types of disturbed soil samples: (1) entire aggregates, (2) aggregates from which coatings were removed, and (3) clay-organic coatings. Sorption of atenolol onto material from coatings was slightly higher than that onto material from the inner parts of the aggregates. On the other hand, sorption of sulfamethoxazole onto material from the coatings was lower than that from the aggregate interior. Both associates with a dominant fraction of clay particles (that are mostly negatively charged) in the coatings in comparison to soil composition in interiors and thus larger cation exchange capacity, which increased sorption of the positively charged atenolol and decreased sorption of the negatively charged sulfamethoxazole. Sorption of carbamazepine, which was in neutral form, did not substantially differ. The sorption of all three compounds did not decrease due to the competition between these compounds for the same sorption sites when applied simultaneously. Atenolol sorption was similar for both applications. Sorption of sulfamethoxazole increased when applied in solution with the other two compounds in comparison to its negligible sorption measured for the single compound solution likely due to sorption of the positively charged molecules of atenolol onto the negatively charged surface of soil components and reduction of repulsion between the soil components and the negatively charged molecules of sulfamethoxazole. Carbamazepine sorption also increased probably due to ionization of molecules due to dipole - induced dipole interaction between non-polar and polar molecules in solution. [ABSTRACT FROM AUTHOR]

The organo-mineral coatings of soil aggregates, cracks, and biopores control sorption and macropore-matrix exchange during preferential flow, in particular in the clay-illuvial Bt-horizon of Luvisols. The soil organic matter (SOM) composition has been hypothesized to explain temporal changes in the hydraulic properties of aggregate surfaces. The objective of this research was to find relations between the temporal change in wettability, in terms of droplet infiltration dynamics, and the SOM composition of coated and uncoated aggregate surfaces. We used 20 to 40 mm sized soil aggregates from the Bt2 horizon of a Haplic Luvisol from loess that were (i) coated, (ii) not coated (both intact), and (iii) aggregates from which coatings were removed (cut). The SOM composition of the aggregate surfaces was characterized by infrared spectroscopy in the diffuse reflection mode (DRIFT). A potential wettability index (PWI) was calculated from the ratio of hydrophobic and hydrophilic functional groups in SOM. The water drop penetration times (WDPT) and contact angles (CA) during droplet infiltration experiments were determined on dry and moist aggregate samples of the three types. The decrease in the CA with time was described using the power function (CA( t) = at−b). For dry aggregates, the WDPT values were larger for coated as compared to uncoated regions on the aggregate surfaces, and increased with increasing PWI value ( R2 = 0.75). The a parameter was significantly related to the WDPT ( R2 = 0.84) and to the PWI ( R2 = 0.64). The relations between the b parameter and the WDPT ( R2 = 0.61) and the PWI ( R2 = 0.53) were also significant. The WDPT values of wet soil aggregates were higher than those of dry aggregates due to high water contents, which limited the droplet infiltration potential. At the wet aggregate surfaces, the WDPT values increased with the PWI of the SOM ( R2 = 0.64). In contrast to dry samples, no significant relationships were found between parameters a or b of CA( t) and WDPT or PWI for wet aggregate surfaces. The results suggest that the effect of the SOM composition of coatings on surface wettability decreases with increasing soil moisture. In addition to the dominant impact of SOM, the wettability of aggregate surfaces could be affected by different mineralogical compositions of clay in coatings and interiors of aggregates. Particularly, wettability of coatings could be decreased by illite which was the dominant clay type in coatings. However, the influence of different clay mineral fractions on surface wettability was not due to small number of measurements (2 and 1 samples from coatings and interiors, respectively) quantified. [ABSTRACT FROM AUTHOR]

Summary: Soil aggregates are in some soils and their horizons covered by organomineral coatings, which may significantly influence water and solute transfer into the aggregates. Knowledge of a coating occurrence, their structure and hydraulic properties is required for a more precise description of water flow and contaminant transport in soils. The aim of this study was to describe hydraulic properties of clay and organic matter coatings in the iluvial (Bt2) horizon of Haplic Luvisol. Sets of 30 unsorted aggregates, 24 aggregates with mostly clay coatings and 24 aggregates with clay-organic coatings, respectively, were studied to evaluate an impact of various coating composition. The coatings were removed from a half of the aggregates of each set. First, the wetting soil–water retention curve was measured on all soil aggregates. Then the capillary rise from the saturation pan into the multiple aggregates (set of 14 or 15 aggregates) without and with coatings was measured. Numerical inversion of the measured cumulative capillary rise data using the HYDRUS-1D program were applied to estimate the saturated hydraulic conductivities of the aggregates, Ks,aggr , and their coatings, Ks,coat . Results were compared with saturated hydraulic conductivities evaluated analytically using the sorptivity method, which was proposed previously. Data of the soil–water retention curves, measured on aggregates with and without coatings, did not allow distinguishing between retention curve parameters of the soil aggregates and their coatings. Therefore the same parameters were evaluated for both. Capillary rise into the soil aggregates without coatings was always faster than into the aggregates with coatings. As result the optimized saturated hydraulic conductivities, Ks,coat , of the clay and the organic matter coatings (the average values for unsorted, mostly clay and clay-organic coatings were 3.69×10−7, 2.76×10−7 and 1.81×10−7 cmmin−1, respectively) were one to two order of magnitude lower than the saturated hydraulic conductivities, Ks,aggr , of the aggregates (the average values for corresponding aggregates were 3.87×10−6, 6.52×10−6 and 1.11×10−5 cmmin−1, respectively). Slightly variable Ks,aggr (or Ks,coat ) values were obtained for different bottom pressure heads, and the lower Ks,aggr (or Ks,coat ) values were estimated from the second run of the tests compare to the first run of tests for each set of aggregates. No statistically significant differences between Ks,coat values obtained for coatings of various compositions were found. Resulting Ks,aggr values were in the range of the values obtained analytically. [Copyright &y& Elsevier]

The stability of soil structure is crucial for providing most of the essential functions of soil. In our previous research in a region of Chernozem soil, multiple linear regression analysis showed that soil aggregate stability within this morphologically diverse study area could be predicted using the soil organic matter content and one of the terrain attributes. Therefore, this present study aims to determine if a similar procedure can be applied to areas of different soil types, namely a Haplic Luvisol, two Haplic Cambisols, and a Calcaric Leptosol. Basic soil properties such as the organic carbon (C ox) content, Fe content, Mn content, CaCO 3 content, pH, magnetic susceptibility, bulk density (ρ z), electrical conductivity, and water-stable aggregate (WSA) index were measured, and terrain attributes were derived using a system for automated geoscientific analyses and a digital elevation model. It was found that it was not possible to propose similar predictive models for all locations. The models included different combinations of the C ox content, CaCO 3 content, Fe content, ρ z , and various terrain attributes. The C ox content was the main parameter that positively affected the WSA index values in the areas of Luvisol and Leptosol soils. Magnetic susceptibility was the main parameter that positively correlated with the WSA index in the two areas of Cambisols, and in one Cambisol area, the WSA index was also positively correlated with the ratio between amorphous and crystalline Fe forms. Negative impacts were observed for ρ z (Luvisol and one Cambisol) and the CaCO 3 content (Leptosol). From the terrain attributes, slope was mostly included in the predictive models. The other attributes were the catchment slope and profile curvature. The best model prediction assessed based on the coefficient of determination was found for the Leptosol area (R2 =0.69), followed by the Luvisol are (R2 =0.60) and both Cambisol areas (R2 =0.52, respectively 0.33). [Display omitted] • Aggregate stability was affected by C and Fe distributions and terrain. • Organic matter mainly controlled aggregate stability in Luvisol and Leptosol soils. • Magnetic susceptibility was an indicator of aggregate stability in Cambisols. • Slope was the main terrain attribute correlated with WSA (aggregate stability). • It was not possible to find similar WSA predictive models for all soil types. [ABSTRACT FROM AUTHOR]