Contamination and Spatiotemporal Trends of Trace Elements in Surface Waters of the Calcasieu River Estuary

Songjie He, School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA, USA, 70808, she5@lsu.edu; Kaci Fisher, School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA, USA, 70808, kaci.fisher@gmail.com,; and Y.Jun Xu, School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA, USA, 70808, yjxu@lsu.edu

Industrial activities have been ongoing in the Lake Charles area since the early 20th century. The Calcasieu River Estuary drains much of this area and is also an important industrial shipping channel, raising concerns over possible metal pollutions in the river. Despite intensive studies of the Calcasieu River in the past, there have been no long term monitoring programs to study the metal contamination of the surface water in the main stem of the Calcasieu River. The objectives of this study were to document the current level of metals and metalloids in the Calcasieu River, and to determine spatial and temporal trends of these metals along the last 88-km reach of the river that has a large salinity gradient ranging from 0.01 to 29.50 ppt. From May 2013 to November 2015, monthly surface water samples were collected and in-situ measurements were performed at six sites along the Calcasieu River. Water samples were analyzed for total recoverable Al, As, Li, B, Cd, Co, Cr, Cu, Fe, Li, Mn, Ni, Ti, V, Zn concentrations and total suspended sediments (TSS) concentrations. In-situ measurements of salinity, pH, and DO% were made. The results show that Cd, Co, Cr, Cu, Ni, and V had less than 30% of detection rate in the surface water samples. Therefore, these elements were excluded in the temporal and spatial trends analysis. The total recoverable concentrations of B and Li both increased significantly with increasing salinity, while the concentrations of other elements showed no clear trends with salinity. All elemental concentrations and ratios showed considerable seasonal variations, with significant differences among sampling months for Al, Mn, and Ti (p<0.01).