Ana Emília Carvalho de Gusmão da Cunha Rabelo a, Severino Martins dos Santos Neto a, Artur Paiva Coutinho b, Antonio Celso Dantas Antonino a
aDepartment of Nuclear Energy, Federal University of Pernambuco, Recife, Brazil.
bAgreste Academic Center – Technology Center, Federal University of Pernambuco, Caruaru, Brazil.
Highlights
- This study determined the kinetics and isotherms sorption of Sulfadiazine (SDZ) in sediments from an alluvial deposit.
- Sulfadiazine showed a higher affinity with the sediment with the most significant organic matter amount and clay content.
- The results showed that SDZ offers a real risk of groundwater contamination due to its low sorption.
- According to the simulations, the advance of the wetting front is disturbed by the presence of heterogeneities.
- The structural heterogeneity impacts the solute transport processes in an alluvial deposit.
Abstract
The Brazilian semiarid region is subjected to irregular rainfall, prolonged droughts, and high temperatures, hampering the surface water accumulation. The water access is restricted to the alluvium in the valleys, which are used for cattle and poultry livestock development. These activities trigger the excessive use of veterinary antibiotics. As a consequence, antibiotics reach sediment surfaces and promote deterioration of groundwater quality. This work aims to evaluate the sorption potential of Sulfadiazine (SDZ) and to understand the dynamics of water transfer and solute transport processes in a typical alluvial deposit of the Capibaribe River, in the Agreste of Pernambuco. The sedimentological characterization was performed by Miall’s Code, defining four lithofacies (Scm, Scm,b, Gcm,o, Scm,o). Kinetics and isotherms experiments allowed the analyses of SDZ sorption. Kinetics sorption showed an equilibrium tendency after 40 h and was better described by a second-order model, while isotherm sorption data were better fitted by the Freundlich model. According to the particle size distribution curve, Scm had the highest number of fine particles and organic matter, affecting interaction of SDZ in sediments. Consequently, SDZ sorption was slightly higher in this lithofacies. However, overall, SDZ sorption was low, thereby offering a real risk of groundwater contamination. For further investigation the dynamics of water transfer and solute transport in a heterogeneous alluvial deposit were simulated with the HYDRUS-2D. The structural heterogeneity influenced the spatial distribution of water storage under unsaturated conditions and provided the emergence of preferential flows. The solute dynamic follow a similar behavior of the water flow, due to the low retention of SDZ in the soil. Considering a condition near to saturation, the contrast of hydraulic and transport properties influences simultaneously in the processes of water transfer and solute transport.
