Transport of Contamination under the Influence of Sea Level Rise in Coastal Heterogeneous Aquifer

• Main Authors: Qiaona Guo, Yahui Zhang, Zhifang Zhou, Zili Hu
• Format: Article
• Language: English
• Published: MDPI AG 2020-11-01
• Series: Sustainability
• Subjects: seawater level rising; contaminant transport; inland heterogeneous unconfined aquifer; coastal zone
• Online Access: https://www.mdpi.com/2071-1050/12/23/9838

This paper provided for the first time an experimental study on the influence of sea level rise on transport of contamination in the heterogeneous unconfined aquifer of the coastal zone. The experiments were conducted using the tank, considering the difference between sea level and inland head 1 cm for Case 1 and 2 cm for Case 2. Observed data were validated using the numerical model, which matched well with the toe length of seawater wedge and the shape of the contaminant plume. The results showed that the observed and simulated values of <inline-formula><math display="inline"><semantics><mrow><msup><mrow><mi>Cl</mi></mrow><mo>−</mo></msup></mrow></semantics></math></inline-formula> concentration at the sampling points increased sharply at the initial time, and then they increased slowly and tended to be stable. The seawater wedge migrated inland with time under the effects of the hydraulic gradient toward the inland and the density difference between saltwater and freshwater. The steady state length of the 50% isoline of the seawater wedge was 167 cm in Case 2, which was larger than that of Case 1. The maximum area of plume in Case 2 was 0.13 m², larger than that in Case 1, which indicated that the velocity of diffusion of the contaminant plume increased as the sea level increased. As the velocity of diffusion increased, the time for pollutant migration to the intersection between seawater and freshwater became shorter. The maximum area and vertical depth of pollutant plume were sensitive to the hydraulic conductivity, dispersivity, and contamination concentration. The infiltration depth and range of the contaminant plume in the heterogeneous aquifer were greater than those in the homogeneous aquifer of the actual beach.