Effects of conservation buffer systems on adsorption of fluorescent-labeled Escherichia coli

The magnitude of bacterial transport through runoff into surface water or infiltration into groundwater is influenced by the adsorption processes in soil. The objective of this study was to evaluate fluorescent-labeled Escherichia coli (E. coli) adsorption by soil under agroforestry buffer (AB), grass buffer (GB), and row crop (RC) management. Adsorption experiments were conducted by inoculating three masses (0.5, 1, and 10 g) of each treatment (AB, GB, and RC) with E. coli O157:H7-GFP with concentration ranges of 10⁵ -10⁸ colony-forming units (cfu) ml^-1 . Adsorption data were evaluated using Langmuir, Freundlich, and Temkin adsorption isotherm models. The Freundlich isotherm model described the observed data well for all treatments using the 10-g soil mass, with the R² values closer to unity in all treatments. The Freundlich K_f parameter, an indicator of adsorption capacity, was higher for the AB treatment (9.93 cfu ml^-1 ) compared with the GB and RC treatments (2.32 and 1.27 cfu ml^-1 , respectively). The multiple pairwise comparisons test (Tukey test) of the Freundlich 1/n_f parameter demonstrated a significant difference (p < .05) between the AB treatment and the RC and GB treatments. Similarly, the K_f values were significantly (p = .05) higher for the 10-g mass under the same test conditions, but no significant differences were observed in the 0.5- and 1-g masses. This study demonstrated that AB has a higher E. coli adsorption capacity and the potential for mitigating the effects of E. coli O157:H7 transport to surface or groundwater through the soil ecosystem.