All chemical measurements of trace elements in the Tonle Sap River and the Tonle Sap Great Lake are presented in Table 1. Cadmium was not detected in any lake (n = 37) and river (n = 14) water samples. Trace elements in the Tonle Sap River ranged from 0.006 μg L−1 (Tl) to 169.80 μg L−1 (Fe), whereas trace elements in the Tonle Sap Great Lake ranged from 0.002 μg L−1 (Ag) to 2,453.00 μg L−1 (Al). As and Zn concentrations in the Tonle Sap River were up to 2.2 and 6.45 times, respectively, higher than the average levels in the world natural rivers. The present findings were consistent with the previous ones reported by Chanpiwat & Sthiannopkao (2014). Likewise, As and Pb concentrations in the Tonle Sap Great Lake were up to 3 and 12.8 times, respectively, greater than the average levels in the world natural rivers. The mean concentrations of other trace elements in both Tonle Sap River and Great Lake were below the average levels of world natural rivers. Another comparison indicated that none of the trace elements in river water exceeded the regulation limits of Cambodia, WHO and USEPA. Likewise, most of the trace elements in lake water were lower than the regulation limits, except Al, Fe and Mn. The concentrations of Al, Fe and Mn in the Tonle Sap Great Lake in the present study were comparable to those reported by Ki et al. (2009). The sources of trace elements in the Tonle Sap River were more likely from the discharge of municipal sewage wastewater into the river (Chanpiwat & Sthiannopkao 2014). Since water flows from the connecting tributary to the Great Lake during the wet monsoon season, trace elements in the Tonle Sap River water can be transported and deposited in the Great Lake. Further investigations on temporal and spatial variations of trace elements in the Great Lake and its tributaries are required to better understand their pollution trends and toxic behaviors which may impact the ecological system of the Tonle Sap Great Lake.

Table 1

Summary of trace elements (μg L−1) in the Tonle Sap River, Tonle Sap Lake, and world natural river, and their regulation limit by the World Health Organization (WHO), US Environmental Protection Agency (USEPA), and Cambodia

Tonle Sap River (n = 14)
Tonle Sap Lake (n = 37)
World natural rivera
Regulation limit
ElementsLODMeanMedianSDMinMaxMeanMedianSDMinMaxAverageSDWHObUSEPAcCambodiad
Ag 0.001 0.81 0.87 0.29 0.41 1.21 0.79 0.22 1.39 0.002 5.48 – – – 100 – 
Al 0.261 11.26 5.92 13.07 3.59 45.55 86.23 16.59 400.23 3.91 2,453.00 32.00 179.00 200 200 200 
As 0.005 0.69 0.64 0.18 0.59 1.31 1.16 1.17 0.27 0.70 1.78 0.60 0.60 10 10 50 
B 0.101 5.50 5.37 0.49 5.19 7.15 10.11 12.52 3.51 5.70 14.48 – – 500 – – 
Ba 0.008 19.47 19.21 1.18 18.27 22.89 20.38 18.74 5.33 14.14 37.22 23.00 13.50 700 200 700 
Cd 0.011 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A 0.10 0.10 3 5 3 
Co 0.001 0.06 0.06 0.01 0.05 0.09 0.11 0.05 0.24 0.03 1.30 0.20 0.10 40 – – 
Cr 0.013 0.08 0.05 0.08 0.01 0.27 0.19 0.11 0.42 0.01 2.32 0.90 2.80 50 100 50 
Cu 0.010 0.81 0.76 0.17 0.61 1.20 1.29 1.39 0.63 0.26 3.14 1.50 0.70 2,000 1,300 1,000 
Fe 0.292 21.30 5.24 45.02 2.37 169.80 111.37 30.82 331.29 11.40 2,041.00 66.00 185.90 300 300 300 
Ga 0.003 4.02 3.91 0.28 3.83 4.80 3.97 3.84 0.99 2.76 7.13 – – – – – 
Mn 0.001 9.21 8.11 3.50 5.43 17.11 13.49 2.07 37.01 0.27 220.10 34.00 12.50 – 50 100 
Mo 0.010 0.14 0.13 0.04 0.10 0.26 0.21 0.21 0.04 0.12 0.33 0.40 0.50 70 – – 
Ni 0.021 0.19 0.15 0.07 0.13 0.36 0.38 0.33 0.30 0.14 2.02 0.80 2.20 70 – 20 
Pb 0.004 0.10 0.07 0.09 0.01 0.30 0.13 0.08 0.21 0.02 1.28 0.10 0.90 10 15 10 
Se 0.017 0.06 0.06 0.01 0.04 0.08 0.08 0.08 0.03 0.03 0.14 – – 10 50 10 
Tl 0.004 0.008 0.008 0.001 0.006 0.011 0.008 0.008 0.004 0.004 0.029 – – – 2 – 
U 0.001 0.02 0.02 0.01 0.02 0.04 0.03 0.03 0.01 0.01 0.09 – – 15 30 – 
Zn 0.052 3.87 1.50 6.94 0.49 26.67 1.98 1.62 1.27 0.45 5.08 0.60 4.60 3,000 5,000 3,000 
Tonle Sap River (n = 14)
Tonle Sap Lake (n = 37)
World natural rivera
Regulation limit
ElementsLODMeanMedianSDMinMaxMeanMedianSDMinMaxAverageSDWHObUSEPAcCambodiad
Ag 0.001 0.81 0.87 0.29 0.41 1.21 0.79 0.22 1.39 0.002 5.48 – – – 100 – 
Al 0.261 11.26 5.92 13.07 3.59 45.55 86.23 16.59 400.23 3.91 2,453.00 32.00 179.00 200 200 200 
As 0.005 0.69 0.64 0.18 0.59 1.31 1.16 1.17 0.27 0.70 1.78 0.60 0.60 10 10 50 
B 0.101 5.50 5.37 0.49 5.19 7.15 10.11 12.52 3.51 5.70 14.48 – – 500 – – 
Ba 0.008 19.47 19.21 1.18 18.27 22.89 20.38 18.74 5.33 14.14 37.22 23.00 13.50 700 200 700 
Cd 0.011 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A 0.10 0.10 3 5 3 
Co 0.001 0.06 0.06 0.01 0.05 0.09 0.11 0.05 0.24 0.03 1.30 0.20 0.10 40 – – 
Cr 0.013 0.08 0.05 0.08 0.01 0.27 0.19 0.11 0.42 0.01 2.32 0.90 2.80 50 100 50 
Cu 0.010 0.81 0.76 0.17 0.61 1.20 1.29 1.39 0.63 0.26 3.14 1.50 0.70 2,000 1,300 1,000 
Fe 0.292 21.30 5.24 45.02 2.37 169.80 111.37 30.82 331.29 11.40 2,041.00 66.00 185.90 300 300 300 
Ga 0.003 4.02 3.91 0.28 3.83 4.80 3.97 3.84 0.99 2.76 7.13 – – – – – 
Mn 0.001 9.21 8.11 3.50 5.43 17.11 13.49 2.07 37.01 0.27 220.10 34.00 12.50 – 50 100 
Mo 0.010 0.14 0.13 0.04 0.10 0.26 0.21 0.21 0.04 0.12 0.33 0.40 0.50 70 – – 
Ni 0.021 0.19 0.15 0.07 0.13 0.36 0.38 0.33 0.30 0.14 2.02 0.80 2.20 70 – 20 
Pb 0.004 0.10 0.07 0.09 0.01 0.30 0.13 0.08 0.21 0.02 1.28 0.10 0.90 10 15 10 
Se 0.017 0.06 0.06 0.01 0.04 0.08 0.08 0.08 0.03 0.03 0.14 – – 10 50 10 
Tl 0.004 0.008 0.008 0.001 0.006 0.011 0.008 0.008 0.004 0.004 0.029 – – – 2 – 
U 0.001 0.02 0.02 0.01 0.02 0.04 0.03 0.03 0.01 0.01 0.09 – – 15 30 – 
Zn 0.052 3.87 1.50 6.94 0.49 26.67 1.98 1.62 1.27 0.45 5.08 0.60 4.60 3,000 5,000 3,000 

LOD, limit of detection; N/A, not applicable because it is below LOD; SD, standard deviation; Min, minimum; Max, maximum.

aAdapted from Chanpiwat & Sthiannopkao 2014.

bWHO 2011.

cUSEPA 2014c.

dMIME 2004.

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