Abstract
In this study, chromium (Cr) retention by the mangroves in the Thi Vai catchment located in the south of Vietnam was simulated using a coupled model of the hydrodynamic model Delft3D with Cr transport and a model for the uptake of Cr by mangroves. This coupled model was calibrated and validated using data from four hydrodynamic stations and data from phytoremediation studies. To analyze the effect of mangroves on reducing Cr pollution, three scenarios were run by the model. Scenario 1 (SC1) is based on the actual situation concerning discharges and the distribution of mangroves. Scenario 2 (SC2) simulates the deterioration of the actual situation by deforestation on the west bank and the establishment of more industrial zones on the east bank. Scenario 3 (SC3) simulates an eco-friendly development comprising the channeling of wastewater through constructed wetlands with mangroves prior to the discharge into the river. Simulation results showed that the total Cr uptake by mangroves in SC3 was higher than in the other two scenarios. In total, 33 kg Cr in water were absorbed by the constructed wetlands in SC3 within one month. The simulation results helped in overcoming the difficulties and challenges in assessing the capacity of mangrove forests on the retention of chromium at catchment scale.
Highlights
Pollution in mangrove estuaries, especially heavy metal pollution, has been extensively addressed worldwide because of its manifest adverse effects on ecosystems and human health [1]
The results showed that simulated water levels were in acceptable agreement with the measured water level for the two validated stations, two and three, and at two seasons with Nash–Sutcliffe efficiency (NSE) > 0.6, d > 0.89 and Root mean square error (RMSE)
Temporal variations of simulated Cr concentrations at the 11 stations along the Thi Vai River are shown in Figures 8 and 9
Summary
Especially heavy metal pollution, has been extensively addressed worldwide because of its manifest adverse effects on ecosystems and human health [1]. Our interest in this study was to develop a mathematical model and apply this model to predict the phytoremediation of mangroves from an uneven distribution of contaminants in the field using the available scattered data This model can help to: (i) calculate the amount of heavy metal taken up by mangrove forests at landscape level; (ii) evaluate the different alternatives of management regimes in mangrove areas; (iii) support the design of a phytoremediation system in the field. The objective of the approach presented in our paper is to close the gap between theoretical concepts and application to a real environmental problem in a catchment This was achieved by model calibration and validation using available field and experimental data in the Thi Vai River (data obtained from the previous work of Nguyen [28], Richter et al [20] and Costa-Boddeker et al [29]). The pollution of coastal waters with Cr(III) and Cr(VI) has been associated with tannery operations worldwide (e.g., Gardner and Ravenscroft [32], Suprapti et al [33], Abdulla et al [34])
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