| The environmental behavior of antibiotics has attracted lots of research attention for the environmental risk. However, antibiotic sorption mechanisms in soils/sediments are still unclear. Comparison of the sorption properties between the widely-studied hydrophobic organic contaminants (HOCs) and antibiotics may provide valuable insight to antibiotic sorption mechanisms. It is critical that the antibiotics adsorption on sediments may be controlled by different sorbent properties. Therefore, the organic contaminants with different polarities were selected as model adsorbates in this study. The chemicals include sulfamethoxazole (SMX), pyrene (PYR) and bisphenol A (BPA). Sediment sample near Dianchi Lake and its separated fractions are the studied adsorbents. Batch adsorption experiments were conducted to examine the sorption behavior of the three adsorbates on different types of adsorbents. In addition, the original adsorbents as well as the adsorbate-loaded adsorbents were characterized to investigate the sorption chanisms.Our results dicated that:1. No obvious relationship between adsorbent properties and sorption characteristics was observed for PYR on sequentially extracted HAs. The geological aging time of the sediment may be the reason for the difference between our results and the literature results. The H/C and O/C results reflect that the sendiment in our study is younger for the eutrophication occurred in Dianchi Lake about 30 years ago. Therefore, we stated that the aging time could be an important factor controlling sorption characteristics.2. Sorption of the nonpolar PYR on HAs was three orders of magnitudes higher than BPA and SMX. Compare the solubility of three adsorbates and their adsorption coefficient. This result indicated that the polarity of organic contaminant is a key factor influencing sorption capacity.3. SMX showed different sorption characteristics on sediment fractions. High sorption of SMX was observed for both separated organic fractions and inorganic mineral particles, while the original sediment particles showed relatively low sorption for SMX. The foc and Kd could not be the increasing relation for SMX in soils/sediments.4. Consult a large number of literature results and competitive sorption experiment between SMX and dissolved humic acid on mineral particles. An obvious competitive phenomenon was observed. These reflect that when the organic carbon fraction (foc) is low, hydrophobic organic contaminants could show great difference with polar organic contaminants regarding their adsorption characteristics. The organic carbonnormalized sorption coefficient (Koc) cannot be applied in describing antibiotic sorption properties. |
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