Sediment-associated metals levels along the sewer-natural treatment wetland continuum, Phnom Penh, Cambodia

Abstract

Sediment deposited within open sewers of Phnom Penh and the natural wetland that treats the waste was sampled and analyzed by X-ray fluorescence (XRF). Mean levels of Pb, Zn (P < 0.05), and Cu (P = 0.08) were greater in the sewer samples than the wetland, while As was not different (P>0.2), and Mn was greater (P < 0.06) in the wetland. Pb, Cu, and Zn levels generally were lower at the wetland outlet and in quiescent areas, suggesting deposition occurs along the sewer/wetland continuum. Background (natural) levels of Mn and As are higher in soils/sediments of this region and levels in the wetland likely reflect these background levels than enrichment from anthropogenic activity. Although 60% of all metals levels in the wetland samples exceeded USEPA threshold effect concentrations, results of recent studies that analyzed fish and vegetables from the wetland showed a small health risk associated with consumption. The XRF was a good tool for environmental analysis in a developing country.

Keywords::

• Phnom Penh
• wetlands treatment
• sewer sediment
• threshold effect concentration
• X-ray fluorescence

Acknowledgements

The handheld XRF XL3t 900 unit was loaned to the study by Mr. Stephen Williams of Thermo Fisher Scientific, Massachusetts, U.S.A. Thanks to students from Royal University of Phnom Penh, Environmental Science Department, in assisting with the sediment sampling. Dr. Elisa Bergslia, Department of Earth Science, Buffalo State, State University of New York, provided the XRF Xli unit and technical advice on XRF analysis.

Disclosure statement

No potential conflict of interest was reported by the authors.