estimating annual cadmium load

International Conference on Environmental and Hazardous Substance Management: Towards a Green Economy, Bangkok, Thailand. May 21-23, 2013

Estimating Annual Cadmium Load via Surface Runoff

into Songkhla Lake, Thailand

Kitipan Kitbamroong, Ph. D

G.Padmanabhan, Ph. D

Penjai Sompongchaiyakul, Ph. D

Problem

Increasing agricultural activities in the catchments of Songkhla Lake have the potential to increase cadmium accumulation in the lake.

Cadmium was found in the lake sediments Cadmium is common in phosphate rocks Surface runoff and associated sediment flow

are the major mechanisms of transport of non-point source pollutants

Research Objectives

To develop a database for non-point source cadmium transport modeling of the Lake Basin from the surrounding drainage area.

To carry out a scenarios analysis of the cadmium transport to the lake from the surrounding drainage areas to assist environmental decision makers.

Methodology

A spatially distributed cell-based model is proposed.

Data to be assembled from local sources on landuse, soils, fertilizers, and practices.

Meaningful scenarios will be constructed For each scenario, the model runs will be

analyzed. Results will be presented to the decision

makers.

Non-Point Source Models

Available models: MIKE SHE SWAT BASINS TREX AnnAGNPS

Criteria Predominant land use: agricultural Data input requirements: local Integration with GIS: Arcview Metals transport

Model and Scenarios Used

Non point source pollution modeling of cadmium TREX (Two-dimenstional Runoff, Erosion,

and eXport model) Scenarios

Three scenarios were tested: Significant increase and decrease of

fertilizer usage. Change in types of fertilizer applied. Change in the application rate of fertilizer

for certain crops.

TREX Two-dimensional Runoff, Erosion, and Export

model is a generalized rainfall-runoff watershed model with a framework for modeling sediment and contaminant transport.

Based on the CASC2D watershed model with chemical transport and fate processes from the USEPA WASP and IPX series of stream water quality models

Three main components: 1) hydrology 2)sediment transport, and 3) chemical transport and fate.

Research Activities Flow Diagram

Source

Mgt Tools

Pre-Processing

Post-ProcessingGIS

The acquired information was compiled in a Geographical Information System (GIS) – ArcView.

The TREX model was run and the result presented within ArcView.

Pre-processing of data and post processing of the model results were done in the GIS platform.

Watershed Delineation

Figure 3-7 Steps performed during watershed delineation

8 Watersheds

Model calibration

The model parameters subject to the calibration were hydraulic conductivity soil erodibility flow resistance crop management factor chemical distribution coefficients.

Model calibration

Chemical distribution coefficients – depending on metal of interest

Model calibration

Parameters of the model are perturbed until an acceptable difference between measured and model-generated output is obtained.

Model validation

The model is run here with the calibrated parameters to compare the performance of the model with measured data (Suviboon, 2006; Leekpai, 2006).

Calibration 20 Stations Precipitation runoff Sedimentation Loss Cd content in sediment Relative error between 5-20%

Verification

220 sampling points

Precipitation runoff Sedimentation Loss Cd content in

sediment Relative error

between 10-30%

hydraulic conductivity

soil erodibility

flow resistance

crop management factor

Cadmium Model Performance Calibration pts Validation pts

Scenario Analysis (1.1) Increase Fertilizer

usage by 10%

Scenario Analysis (1.2) Increase Fertilizer

usage by 50%

Scenario Analysis (1.3)

Decrease usage by 10%

Scenario Analysis (1.4) Decrease usage by

Scenario Analysis (2)

changing types of fertilizer

7.19 mg/kg cadmium 7.27 mg/kg cadmium

Scenario Analysis (2)

changing types of fertilizer

Scenario Analysis (3) change of crops grown

in the area

Conclusion

Substance Flux Analysis 41,745 tons/year of phosphorus, and 273

kg/year of cadmium from phosphate fertilizer were induced into SLB.

The stock calculation for phosphorus and cadmium were found to be 248.7 tons/year and 62.8 tons/year respectively.

Conclusion TREX Modeling

U-Tapao watershed had the highest potential of phosphorous and cadmium transportation in the sediment runoff.

Factors promoting includes; run off – high runoff elevation – steep slope soil erodibility – high erosion organic matter – high pH –acidity crop management – horticultural crops clay – high percentage total metal – high

Conclusion

Scenario Analysis A total of three scenarios were demonstrated

and tested in U-Tapao sub watershed. Alone by changing the fertilizer formula, from high

to low contaminated cadmium lead towards a significant decrease of cadmium contribution to the watershed.

Acknowledgements Asst. Prof. Dr. Chatchai Ratanachai (PSU) Dr. Manaskorn Rachakornkij (CU) Lecturers and staffs of NRC-EHWM

estimating annual cadmium load

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