To investigate the potential health risk of trace elements in the Tonle Sap Great Lake system, lake (n = 37) and river (n = 14) water samples were collected and analyzed for 19 trace elements (Ag, Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Ga, Mn, Mo, Ni, Pb, Se, Tl, U and Zn) using inductively coupled plasma mass spectrometry. As a result, Cd was not detected in any river and lake water samples. Al, Fe and Mn in lake water exceeded the regulation limits of Cambodia, USEPA and WHO. Health risk assessment using the USEPA model indicated that male and female Cambodian residents are at minimal risk of non-carcinogenic effects from single and mixed trace elements through lake and river water consumption. Nevertheless, As, Tl, Co, Ba, Mn and Cr might pose high potential health risks to consumers which requires more attention. Therefore, regular monitoring and further studies are required to investigate the pollution trends and toxic behavior of these trace elements in the Tonle Sap Great Lake system.

  • We investigated the distribution of 19 trace elements in the Tonle Sap Great Lake system.

  • As, B, Cu, Mo, Ni, Se and U in the Great Lake were higher than those in the river.

  • Ag, As, B, Ba, Cu, Ga, Mn and Se were significantly different among the five provinces.

  • Residents did not have the non-carcinogenic effect of trace elements through lake and river water consumption.

Contamination by trace elements has created substantial concern among environmental scientists. Although some trace elements are essential for the normal growth of humans and animals, high intake and low intake of essential trace elements can lead to toxicity and nutritional deficiency, respectively (Goldhaber 2003). For instance, trace elements in drinking water (Kavcar et al. 2009) and food grains grown in contaminated soils (Huang et al. 2008) can pose significant non-carcinogenic effects on their consumers. Ecological communities and living organisms in receiving water are also affected by the direct discharge of effluents from various industries into aquatic systems (Krishna et al. 2009). The Tonle Sap Great Lake is the largest freshwater lake in SE Asia, and hosts one of the most productive inland fisheries in the world, accounting for more than 75% of Cambodia's inland fish catch and 60% of the country's protein needs (Burnett et al. 2013). The temperature in Cambodia is likely to rise by between 0.13 and 0.36 °C per decade while rainfall patterns are not clear with some increase in average rainfall in hilly areas in the wet season and a decrease in the dry season (NCCC 2013). The rainfall distribution in Cambodia is strongly influenced by her topography and seasonal monsoons resulted in the highest rainfall (2,000–3,400 mm) occurring in the southwest in coastal areas followed by the northeast plateau area (1,800 to >2,200 mm) and the stretches from the northwest to the southeast which receives annual rainfall of <1,400 mm (Sok & Chuop 2017). Recently, many food industries and factories have been located on the bank of the Tonle Sap River. Industrialization and population growth along the river are believed to be major distributors of trace elements in the Tonle Sap River (Chanpiwat & Sthiannopkao 2014). In general, Cambodian residents living along the Tonle Sap River downstream of Phnom Penh rely on the river water, whereas those living around the Tonle Sap Great Lake rely on the lake water as a main source of their water supply. Although conventional water quality parameters had been continuously monitored (Irvine et al. 2011), a few assessments of trace element contaminations in the Tonle Sap River (Chanpiwat & Sthiannopkao 2014) and Tonle Sap Great Lake (Ki et al. 2009) of Cambodia have been conducted to date. On the other hand, health risk assessment of trace elements of residents who drink the river and lake water has not yet been conducted. The overall objective of the present project was to investigate the distribution of trace elements in the Tonle Sap Great Lake and the Tonle Sap River in Cambodia and assess the health risks of residents who drink these waters. Specifically, it was to (1) determine the distribution of trace elements in the five surrounding provinces of the Tonle Sap Great Lake of Cambodia, (2) compare the concentration of trace elements among the five surrounding provinces, (3) compare the concentrations of trace elements in the Great Lake and its tributary and (4) assess the human health risk of trace elements through drinking water from the Tonle Sap River and the Tonle Sap Great Lake.

Field work

The present project was designed as a cross-sectional study. Sampling was carried out in the middle of August 2013 around the Tonle Sap Great Lake (Figure 1). The water level of the lake varies from an average depth of less than 2 m during the dry season to a maximum depth of 8–10 m at the end of the rainy season (Masumoto et al. 2008). Water from the lake flows south every dry season (surface area of 2,200 km2) through a tributary (Tonle Sap River) connecting the lake to the Mekong River near Phnom Penh (Burnett et al. 2013). When the wet monsoon rains begin around June, the flow of the Mekong River increases dramatically and water flows in the connecting tributary reverse, adding large volumes of water back into the lake, which results in an approximately six-fold increase in surface area (Burnett et al. 2013). Lake water was collected from the surrounding provinces, namely, Siem Reap (n = 10), Battambang (n = 10), Pursat (n = 10), Kampong Chhnang (n = 4), and Kampong Thom (n = 3). In addition, river water samples (n = 14) were also collected from the Tonle Sap River which connects the Mekong River to the Great Lake. Lake and river water samples were collected from each point of sampling at a depth of 30 cm below the water surface. At each sampling location, a composite sample was obtained from a grab sample of lake water. The water samples were then filled into an acid-cleaned polypropylene bottle. Immediately after collection, all samples were acidified with concentrated HNO3 to pH < 2, kept in an ice-box, and transferred to a fridge where they were stored at 4 °C, and then delivered to the laboratory for chemical analyses.
Figure 1

Map of the sampling area.

Figure 1

Map of the sampling area.

Close modal

Sample analyses

All chemical measurements were employed by inductively coupled plasma mass spectroscopy (ICP-MS, Agilent 7500 ce) using an external calibration method. Working standard solutions were prepared in a proper range of ICP-MS (0, 0.1, 1, 5, 10, 20, 50, 100 μg L−1). For the solvent to use in solution preparation, and analytical procedures, 2% HNO3 (percent by volume) was prepared from 18.2 MΩ cm−1 deionized water obtained from a Millipore Milli-Q water purification system. The possibility of trace metal contamination in the 2% HNO3 was also checked and reported as an analytical blank. A standard reference material (Trace Element in Water, SRM 1643e) was analyzed to check the ICP-MS accuracy. If the recovery rate was out of the recommended range (90–110%), samples were reanalyzed with a new calibration curve.

Health risk assessment

Health risk assessment procedures from the USEPA (1989) were applied to calculate the non-carcinogenic effects of single and mixed trace elements. The average daily dose of a single element is calculated from the following equation.
(1)
where ADD is the average daily dose from ingestion (μg kg−1 d−1); Cw is the trace element concentration in groundwater (μg L−1); IR is the ingestion rate of groundwater (L d−1); EF is the exposure frequency (d y−1); ED is the exposure duration (y); BW is the body weight (kg) and AT is the averaging time (d). Non-carcinogenic effects of single elements, expressed as hazard quotient (HQ), are computed from Equation (2), whereas non-carcinogenic effects of mixed trace elements (hazard index) are calculated from Equation (3). Cw of the trace elements is measured in this study. Our field observation and communication with local people indicated that the residents in this study area use river and lake water the whole year around (365 d y−1). The average body weight of Cambodian female adults (49 kg) and male adults (54 kg) and average age of Cambodian females (65 years) and males (59 years) are adapted from Phan et al. (2010, 2013):
(2)
HQ is a hazard quotient. Non-carcinogenic effects were considered if HQ > 1; RfD is a reference dose of a single element. The oral reference dose (μg kg−1 d−1) of Ag (5), Al (1,000), As (0.3), B (200), Ba (200), Co (0.3), Cr (3), Cu (40), Fe (700), Mn (140), Mo (5), Ni (20), Se (5), Tl (0.01) U (3) and Zn (300) was obtained from a database of the Integrated Risk Information System (USEPA 2014a) and risk-based concentration tables (USEPA 2014b):
(3)

HI is a hazard index which indicated the aggregate risk/risk of mixed trace elements. Non-carcinogenic effects of mixed trace elements are considered to occur in a circumstance where HI is greater than one.

Statistical data analyses

All statistical data analyses were performed by SPSS for Windows (Version 16.0). One-Way ANOVA tests and post hoc tests were conducted to certify the difference in trace element concentrations among the five surrounding provinces of the Tonle Sap Great Lake. An independent samples t-test was applied to access the difference in trace element concentrations in the Great Lake and its tributary.

Distribution of trace elements in the Great Lake and its tributary

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 
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 
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 – – – – 
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 
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 
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 – – – – 
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.

Comparisons of trace elements in the Great Lake and its tributary

The t-tests revealed that there were no significant differences in Ag, Al, Ba, Co, Cr, Fe, Ga, Mn, Pb, Tl and Zn in the Tonle Sap Great Lake and its tributary river (p > 0.05; Table 2). However, As, B, Cu, Mo, Ni, Se and U concentrations in the Great Lake were significantly higher than those in the river (t-test, p < 0.05; Table 2). Ki et al. (2009) revealed that concentrations of trace elements in the Tonle Sap Great Lake were generally higher than those in other water systems because it is the final depository. There were also significant differences in Ag, As, B, Ba, Cu, Ga, Mn and Se among the five surrounding provinces of the Great Lake (one-way ANOVA, p < 0.05; Table 3). Nevertheless, Al, Co, Cr, Fe, Mo, Ni, Pb, Tl, U and Zn were not significantly different among the five provinces (one-way ANOVA, p > 0.05; Table 3). Games–Howell post hoc test indicated there were no significant differences in Ag among Siem Reap, Battambang, Pursat, Kampong Chhnang and Kampong Thom (p > 0.05). There were significant differences in B, Cu and Se between Siem Reap and Pursat, Kampong Chhnang and Kampong Thom, between Battambang and Pursat, and between Kampong Chhnang and Kampong Thom (p < 0.05). Likewise, there were significant differences in Ga among Siem Reap and Pursat and Kampong Chhnang and between Pursat and Kampong Chhnang (p < 0.05). There was a significant difference in Mn between Siem Reap and Pursat (p < 0.05). The Tukey HSD (honestly significant difference) test indicated that As was significantly different among Kampong Chhnang and Battambang and Kampong Thom (p < 0.05). There were significant differences in Ba between Siem Reap and Pursat, Kampong Chhnang and Kampong Thom and between Battambang and Pursat, Kampong Chhnang and Kampong Thom as well as between Pursat and Kampong Thom (p < 0.05). The differences in metal concentrations between sampling locations of the same lake have been found in the literature. For instance, Oyoo-Okoth et al. (2013) reported that the mean concentrations of Cd, Co, Cr, Cu, Ti and Zn in lake water were significantly different in locations of Lake Victoria, Kenya. Concurrently, the mean concentrations of Cu, Zn, Cd, Pb, Co, and Fe in lake water were found significantly different between locations of Lake Titicaca, South America (Monroy et al. 2014). When compared to lakes in other countries (Table 4), it indicated that the mean concentrations of Co, Cr, Cu, Pb and Zn in water of the Tonle Sap Great Lake were lower than those in the Rawal Lake, Pakistan in summer, reported by Iqbal et al. (2013). It was also apparent that mean concentrations of Cu, Pb and Zn in water of the Tonle Sap Great Lake were much lower than those in the Lake Dalinouer, China (Hou et al. 2013) and mean concentrations of As, Cr, Cu, Ni, Pb and Zn were lower than those in the Taihu Lake, China (Jiang et al. 2012). Although Fe and Co concentrations in lake water were similar between the Tonle Sap Great Lake and the Lake Titicaca (Monroy et al. 2014), the concentrations of Cu, Pb and Zn in water of the Tonle Sap Great Lake were relatively lower. The mean concentrations of Pb, Cr and Cu in water of the Tonle Sap Great Lake were much lower than those in Lake Victoria, Kenya, reported by Oyoo-Okoth et al. (2010).

Table 2

Comparison of trace elements in the Tonle Sap Great lake and Tonle Sap River

VariableMeanSDtdfp
Aga   0.055 31.214 0.956 
River 0.806 0.290    
Great lake 0.790 1.392    
Al   −0.696 49 0.489 
River 11.26 13.07    
Great lake 86.23 400.23    
Asa   −7.084 35.265 <0.01 
River 0.686 0.182    
Great lake 1.155 0.273    
Ba   −7.793 39.507 <0.01 
River 5.499 0.489    
Great lake 10.107 3.508    
Baa   −0.983 43.896 0.331 
River 19.469 1.181    
Great lake 20.384 5.331    
Co   −0.759 49 0.451 
River 0.060 0.013    
Great lake 0.109 0.243    
Cr   −0.941 41 0.352 
River 0.085 0.078    
Great lake 0.191 0.416    
Cua   −4.222 46.39 <0.01 
River 0.811 0.169    
Great lake 1.286 0.627    
Fe   −1.008 49 0.319 
River 21.30 45.02    
Great lake 111.37 331.29    
Gaa   0.318 46.93 0.752 
River 4.025 0.279    
Great lake 3.968 0.995    
Mn   −0.429 49 0.67 
River 9.21 3.50    
Great lake 13.49 37.01    
Mo   −5.333 49 <0.01 
River 0.142 0.037    
Great lake 0.205 0.038    
Ni   −2.416 49 0.019 
River 0.185 0.070    
Great lake 0.384 0.303    
Pb   −0.446 49 0.657 
River 0.105 0.094    
Great lake 0.131 0.207    
Sea   −4.003 48.864 <0.01 
River 0.056 0.011    
Great lake 0.079 0.029    
Tl   −0.564 49 0.575 
River 0.008 0.001    
Great lake 0.008 0.004    
  −2.159 49 0.036 
River 0.022 0.006    
Great lake 0.029 0.012    
Zna   1.013 13.331 0.329 
River 3.867 6.939    
Great lake 1.978 1.271    
VariableMeanSDtdfp
Aga   0.055 31.214 0.956 
River 0.806 0.290    
Great lake 0.790 1.392    
Al   −0.696 49 0.489 
River 11.26 13.07    
Great lake 86.23 400.23    
Asa   −7.084 35.265 <0.01 
River 0.686 0.182    
Great lake 1.155 0.273    
Ba   −7.793 39.507 <0.01 
River 5.499 0.489    
Great lake 10.107 3.508    
Baa   −0.983 43.896 0.331 
River 19.469 1.181    
Great lake 20.384 5.331    
Co   −0.759 49 0.451 
River 0.060 0.013    
Great lake 0.109 0.243    
Cr   −0.941 41 0.352 
River 0.085 0.078    
Great lake 0.191 0.416    
Cua   −4.222 46.39 <0.01 
River 0.811 0.169    
Great lake 1.286 0.627    
Fe   −1.008 49 0.319 
River 21.30 45.02    
Great lake 111.37 331.29    
Gaa   0.318 46.93 0.752 
River 4.025 0.279    
Great lake 3.968 0.995    
Mn   −0.429 49 0.67 
River 9.21 3.50    
Great lake 13.49 37.01    
Mo   −5.333 49 <0.01 
River 0.142 0.037    
Great lake 0.205 0.038    
Ni   −2.416 49 0.019 
River 0.185 0.070    
Great lake 0.384 0.303    
Pb   −0.446 49 0.657 
River 0.105 0.094    
Great lake 0.131 0.207    
Sea   −4.003 48.864 <0.01 
River 0.056 0.011    
Great lake 0.079 0.029    
Tl   −0.564 49 0.575 
River 0.008 0.001    
Great lake 0.008 0.004    
  −2.159 49 0.036 
River 0.022 0.006    
Great lake 0.029 0.012    
Zna   1.013 13.331 0.329 
River 3.867 6.939    
Great lake 1.978 1.271    

SD, standard deviation.

aThe t and df were adjusted because variances were not equal.

Table 3

One-way analysis of variance comparing regional groups on trace elements in the Tonle Sap Great Lake

SourcedfSSMSFp
Ag Between groups 18.19 4.55 3.11 0.036 
Within groups 22 32.20 1.46   
Total 26 50.39    
Al Between groups 420,148.80 105,037.20 0.63 0.646 
Within groups 32 5,346,395.66 167,074.86   
Total 36 5,766,544.46    
As Between groups 0.85 0.21 3.73 0.013 
Within groups 32 1.83 0.06   
Total 36 2.68    
Between groups 432.41 108.10 325.66 <0.01 
Within groups 32 10.62 0.33   
Total 36 443.03    
Ba Between groups 630.15 157.54 12.83 <0.01 
Within groups 32 392.85 12.28   
Total 36 1,023.00    
Co Between groups 0.52 0.13 2.59 0.055 
Within groups 32 1.60 0.05   
Total 36 2.12    
Cr Between groups 0.59 0.15 0.83 0.517 
Within groups 24 4.25 0.18   
Total 28 4.84    
Cu Between groups 11.44 2.86 33.80 <0.01 
Within groups 32 2.71 0.08   
Total 36 14.14    
Fe Between groups 222,215.21 55,553.80 0.48 0.752 
Within groups 32 3,728,824.68 116,525.77   
Total 36 3,951,039.89    
Ga Between groups 17.56 4.39 7.78 <0.01 
Within groups 32 18.06 0.56   
Total 36 35.62    
Mn Between groups 25,364.03 6,341.01 8.47 <0.01 
Within groups 32 23,950.16 748.44   
Total 36 49,314.20    
Mo Between groups 0.01 0.00 1.20 0.329 
Within groups 32 0.05 0.00   
Total 36 0.05    
Ni Between groups 0.62 0.16 1.84 0.145 
Within groups 32 2.70 0.08   
Total 36 3.32    
Pb Between groups 0.11 0.03 0.64 0.638 
Within groups 32 1.43 0.04   
Total 36 1.54    
Se Between groups 0.02 0.01 20.73 <0.01 
Within groups 32 0.01 0.00   
Total 36 0.03    
Tl Between groups 0.00 0.00 0.49 0.744 
Within groups 32 0.00 0.00   
Total 36 0.00    
Between groups 0.00 0.00 0.86 0.496 
Within groups 32 0.00 0.00   
Total 36 0.01    
Zn Between groups 8.61 2.15 1.39 0.259 
Within groups 32 49.52 1.55   
Total 36 58.13    
SourcedfSSMSFp
Ag Between groups 18.19 4.55 3.11 0.036 
Within groups 22 32.20 1.46   
Total 26 50.39    
Al Between groups 420,148.80 105,037.20 0.63 0.646 
Within groups 32 5,346,395.66 167,074.86   
Total 36 5,766,544.46    
As Between groups 0.85 0.21 3.73 0.013 
Within groups 32 1.83 0.06   
Total 36 2.68    
Between groups 432.41 108.10 325.66 <0.01 
Within groups 32 10.62 0.33   
Total 36 443.03    
Ba Between groups 630.15 157.54 12.83 <0.01 
Within groups 32 392.85 12.28   
Total 36 1,023.00    
Co Between groups 0.52 0.13 2.59 0.055 
Within groups 32 1.60 0.05   
Total 36 2.12    
Cr Between groups 0.59 0.15 0.83 0.517 
Within groups 24 4.25 0.18   
Total 28 4.84    
Cu Between groups 11.44 2.86 33.80 <0.01 
Within groups 32 2.71 0.08   
Total 36 14.14    
Fe Between groups 222,215.21 55,553.80 0.48 0.752 
Within groups 32 3,728,824.68 116,525.77   
Total 36 3,951,039.89    
Ga Between groups 17.56 4.39 7.78 <0.01 
Within groups 32 18.06 0.56   
Total 36 35.62    
Mn Between groups 25,364.03 6,341.01 8.47 <0.01 
Within groups 32 23,950.16 748.44   
Total 36 49,314.20    
Mo Between groups 0.01 0.00 1.20 0.329 
Within groups 32 0.05 0.00   
Total 36 0.05    
Ni Between groups 0.62 0.16 1.84 0.145 
Within groups 32 2.70 0.08   
Total 36 3.32    
Pb Between groups 0.11 0.03 0.64 0.638 
Within groups 32 1.43 0.04   
Total 36 1.54    
Se Between groups 0.02 0.01 20.73 <0.01 
Within groups 32 0.01 0.00   
Total 36 0.03    
Tl Between groups 0.00 0.00 0.49 0.744 
Within groups 32 0.00 0.00   
Total 36 0.00    
Between groups 0.00 0.00 0.86 0.496 
Within groups 32 0.00 0.00   
Total 36 0.01    
Zn Between groups 8.61 2.15 1.39 0.259 
Within groups 32 49.52 1.55   
Total 36 58.13    

df, degree of freedom; SS, sum of squares; MS, mean square.

Table 4

Comparisons of trace elements (μg L−1) in the Tonle Sap Great Lake and lakes in other countries

Cambodia Tonle Sap Great Lake (present study)
ChinaaKenyabPakistancNew ZealanddSouth AmericaeUSAf
ElementsTSBTSSTSPTSCTSTTaihu LakeVictoriaRawal LakeLake HaurokoTiticacaHough Park Lake
Ag 0.21 1.95 0.23 0.15 0.30 – – – – – – 
Al 27.72 261.16 19.90 12.04 18.16 – – – – – 436.00 
As 1.14 1.28 1.15 0.77 1.33 1.86 – – – – – 
13.32 13.18 6.18 6.33 7.31 – – – – – – 
Ba 16.44 17.53 22.58 24.82 29.80 – – – – – 43.00 
Cd N/A N/A N/A N/A N/A 0.06 0.12 6.00 0.0013 0.06 – 
Co 0.048 0.143 0.050 0.045 0.483 – 0.05 11.00 0.005 0.25 – 
Cr 0.109 0.383 0.032 0.130 0.057 0.99 0.13 9.00 – – 1.00 
Cu 1.57 1.98 0.76 0.80 0.45 5.81 2.20 10.00 0.235 2.45 – 
Fe 39.00 224.51 87.42 28.73 165.50 – – 93.00 0.005 111.6 298.00 
Ga 3.26 3.57 4.28 4.78 5.53 – – – – – – 
Mn 0.71 4.92 10.12 9.85 100.72 – – 4.00 0.080 – 93.00 
Mo 0.210 0.210 0.206 0.212 0.160 – – – – – – 
Ni 0.33 0.57 0.33 0.16 0.46 5.34 – – 0.106 – 1.00 
Pb 0.109 0.220 0.095 0.075 0.095 2.74 – 162.00 0.002 3.07 0.40 
Se 0.100 0.101 0.059 0.046 0.043 – – – – – – 
Tl 0.008 0.009 0.009 0.007 0.006 – – – – – – 
0.033 0.027 0.029 0.033 0.019 – – – – – – 
Zn 1.26 2.46 2.12 1.83 2.48 15.86 8.3 14.00 0.054 23.67 3.00 
Cambodia Tonle Sap Great Lake (present study)
ChinaaKenyabPakistancNew ZealanddSouth AmericaeUSAf
ElementsTSBTSSTSPTSCTSTTaihu LakeVictoriaRawal LakeLake HaurokoTiticacaHough Park Lake
Ag 0.21 1.95 0.23 0.15 0.30 – – – – – – 
Al 27.72 261.16 19.90 12.04 18.16 – – – – – 436.00 
As 1.14 1.28 1.15 0.77 1.33 1.86 – – – – – 
13.32 13.18 6.18 6.33 7.31 – – – – – – 
Ba 16.44 17.53 22.58 24.82 29.80 – – – – – 43.00 
Cd N/A N/A N/A N/A N/A 0.06 0.12 6.00 0.0013 0.06 – 
Co 0.048 0.143 0.050 0.045 0.483 – 0.05 11.00 0.005 0.25 – 
Cr 0.109 0.383 0.032 0.130 0.057 0.99 0.13 9.00 – – 1.00 
Cu 1.57 1.98 0.76 0.80 0.45 5.81 2.20 10.00 0.235 2.45 – 
Fe 39.00 224.51 87.42 28.73 165.50 – – 93.00 0.005 111.6 298.00 
Ga 3.26 3.57 4.28 4.78 5.53 – – – – – – 
Mn 0.71 4.92 10.12 9.85 100.72 – – 4.00 0.080 – 93.00 
Mo 0.210 0.210 0.206 0.212 0.160 – – – – – – 
Ni 0.33 0.57 0.33 0.16 0.46 5.34 – – 0.106 – 1.00 
Pb 0.109 0.220 0.095 0.075 0.095 2.74 – 162.00 0.002 3.07 0.40 
Se 0.100 0.101 0.059 0.046 0.043 – – – – – – 
Tl 0.008 0.009 0.009 0.007 0.006 – – – – – – 
0.033 0.027 0.029 0.033 0.019 – – – – – – 
Zn 1.26 2.46 2.12 1.83 2.48 15.86 8.3 14.00 0.054 23.67 3.00 

TSB, Tonle Sap Battambang; TST, Tonle Sap Siem Reap; TSP, Tonle Sap Pursat; TSC, Tonle Sap Kampong Chhnang; TST, Tonle Sap Kampong Thom.

Assessment of health risks from drinking lake and river water

The average daily doses (ADDs) of single trace elements are provided in Table 5. The HQ of a single trace element and the hazard index (HI) of multiple trace elements are presented in Table 6. In total, 16 trace elements were included in the health risk assessment. Cadmium was excluded because it was not detected in any river and lake water samples. Gallium and lead were excluded because their oral reference doses (RfDs) were not available at the USEPA. Calculations indicated that male and female Cambodian residents ingested less amount of trace elements in water from the Tonle Sap River and the Tonle Sap Great Lake than those in Pakistan (Iqbal et al. 2013) and China (Wu et al. 2009; Li & Zhang 2010). Moreover, risk calculation indicated that all HQs of each single trace element and the HI of the multiple trace elements were less than one, indicating male and female Cambodian residents were at minimal risk of single and multiple trace elements through consumption of the Tonle Sap Great Lake and River water. Health risk assessment of trace metals in freshwater Rawal Lake, Pakistan revealed that Co and Pb were the major pollutants during summer and Cd, Co, Cr and Pb were the major pollutants during winter, which could pose adverse health effects to the local consumers through the water drinking pathway (Iqbal et al. 2013). Recently, a health risk assessment of trace elements in the upper Han River, China indicated that As, Pb, Sb, Se and V were the largest contributor to chronic risk in the dry season while As, Co, Pb, Sb and V in the rainy season (Li & Zhang 2010). Concurrently, a health risk assessment of trace metal in surface water from the Yangtze River in Nanjing section, China suggested trace metals could pose a minimal hazard to local residents (Wu et al. 2009). It is apparent that the Tonle Sap River and the Tonle Sap Great Lake water were substantially safe in trace elements and could be used as drinking water sources, considering the treatments of microbial contaminants and organic pollutants as well as emerging environmental pharmaceuticals. However, Cambodian local residents were at relatively high potential health risks of As, Tl, Ba, Co, Mn and Cr when compared to other trace elements (Table 6). The management and control of the contamination sources should be taken into account. In fact, if industrial and municipal sewages are well managed and controlled prior to discharges to the Tonle Sap River, it might reduce the potential health risks to the consumers who rely on the Tonle Sap Great Lake resources such as water and fishery products. It might also reduce the ecological risks to the aquatic plants and animals in the Great Lake system. Nevertheless, we have not investigated seasonal changes which are believed to influence the concentrations of these trace elements and the water quality of the Great Lake and its tributary due to budget and time constraints. These limitations allowed us to assess the health risks of consumers only in the rainy season (May to November). However, the authors feel that it is substantially informative because a few people would consume lake and river water in the dry season (December to April) due to a long-distance carrier. Our previous study showed that groundwater in the Mekong River basin is the main source of drinking although many people live alongside surface water (Phan et al. 2010). Many people switched from the consumption of surface water to groundwater owing to their concerns about microbial contaminations (Phan et al. 2010). Of course, surface water is consumed during the raising stage of the Mekong River water which results in an overflow and flooding.

Table 5

Summary of average daily intake (×10−2 μg kg−1 d−1) of trace elements of Cambodian residents through drinking water from the Tonle Sap River and the Tonle Sap Great Lake

Tonle Sap River
Tonle Sap Great Lake
Female
Male
Female
Male
ElementsMeanMedianSDMeanMedianSDMeanMedianSDMeanMedianSD
Ag 1.29 1.39 0.46  1.52 1.64 0.55 1.26 0.36 2.23  1.49 0.42 2.62 
Al 18.03 9.48 20.93  21.20 11.15 24.62 138.08 26.56 640.87  162.39 31.24 753.72 
As 1.10 1.02 0.29  1.29 1.20 0.34 1.85 1.88 0.44  2.18 2.21 0.51 
8.80 8.60 0.78  10.35 10.11 0.92 16.18 20.05 5.62  19.03 23.58 6.61 
Ba 31.17 30.76 1.89  36.66 36.18 2.22 32.64 30.01 8.54  38.39 35.29 10.04 
Co 0.10 0.09 0.02  0.11 0.10 0.02 0.18 0.08 0.39  0.21 0.09 0.46 
Cr 0.14 0.09 0.12  0.16 0.10 0.15 0.31 0.18 0.67  0.36 0.21 0.78 
Cu 1.30 1.22 0.27  1.53 1.44 0.32 2.06 2.23 1.00  2.42 2.62 1.18 
Fe 34.11 8.39 72.09  40.11 9.87 84.79 178.33 49.35 530.48  209.74 58.04 623.89 
Mn 14.76 12.99 5.61  17.35 15.27 6.60 21.60 3.31 59.26  25.40 3.90 69.70 
Mo 0.23 0.21 0.06  0.27 0.25 0.07 0.33 0.33 0.06  0.39 0.39 0.07 
Ni 0.30 0.25 0.11  0.35 0.29 0.13 0.62 0.53 0.49  0.72 0.62 0.57 
Se 0.09 0.09 0.02  0.11 0.11 0.02 0.13 0.12 0.05  0.15 0.15 0.05 
Tl 0.01 0.01 0.00  0.01 0.01 0.00 0.01 0.01 0.01  0.02 0.01 0.01 
0.03 0.03 0.01  0.04 0.04 0.01 0.05 0.05 0.02  0.05 0.06 0.02 
Zn 6.19 2.41 11.11  7.28 2.83 13.07 3.17 2.59 2.03  3.72 3.05 2.39 
Tonle Sap River
Tonle Sap Great Lake
Female
Male
Female
Male
ElementsMeanMedianSDMeanMedianSDMeanMedianSDMeanMedianSD
Ag 1.29 1.39 0.46  1.52 1.64 0.55 1.26 0.36 2.23  1.49 0.42 2.62 
Al 18.03 9.48 20.93  21.20 11.15 24.62 138.08 26.56 640.87  162.39 31.24 753.72 
As 1.10 1.02 0.29  1.29 1.20 0.34 1.85 1.88 0.44  2.18 2.21 0.51 
8.80 8.60 0.78  10.35 10.11 0.92 16.18 20.05 5.62  19.03 23.58 6.61 
Ba 31.17 30.76 1.89  36.66 36.18 2.22 32.64 30.01 8.54  38.39 35.29 10.04 
Co 0.10 0.09 0.02  0.11 0.10 0.02 0.18 0.08 0.39  0.21 0.09 0.46 
Cr 0.14 0.09 0.12  0.16 0.10 0.15 0.31 0.18 0.67  0.36 0.21 0.78 
Cu 1.30 1.22 0.27  1.53 1.44 0.32 2.06 2.23 1.00  2.42 2.62 1.18 
Fe 34.11 8.39 72.09  40.11 9.87 84.79 178.33 49.35 530.48  209.74 58.04 623.89 
Mn 14.76 12.99 5.61  17.35 15.27 6.60 21.60 3.31 59.26  25.40 3.90 69.70 
Mo 0.23 0.21 0.06  0.27 0.25 0.07 0.33 0.33 0.06  0.39 0.39 0.07 
Ni 0.30 0.25 0.11  0.35 0.29 0.13 0.62 0.53 0.49  0.72 0.62 0.57 
Se 0.09 0.09 0.02  0.11 0.11 0.02 0.13 0.12 0.05  0.15 0.15 0.05 
Tl 0.01 0.01 0.00  0.01 0.01 0.00 0.01 0.01 0.01  0.02 0.01 0.01 
0.03 0.03 0.01  0.04 0.04 0.01 0.05 0.05 0.02  0.05 0.06 0.02 
Zn 6.19 2.41 11.11  7.28 2.83 13.07 3.17 2.59 2.03  3.72 3.05 2.39 

SD, standard deviation.

Table 6

Summary of RfD (μg kg−1 d−1) and non-carcinogenic risks of single (HQ ×10−2) and mixed (HI ×10−2) elements of Cambodian residents through drinking water from the Tonle Sap River and the Tonle Sap Great Lake

Tonle Sap River
Tonle Sap Great Lake
Female
Male
Female
Male
ElementsRfDMeanMedianSDMeanMedianSDMeanMedianSDMeanMedianSD
Ag 0.26 0.28 0.09  0.30 0.33 0.11  0.25 0.07 0.45  0.30 0.08 0.52 
Al 1000 0.02 0.01 0.02  0.02 0.01 0.02  0.14 0.03 0.64  0.16 0.03 0.75 
As 0.3 3.66 3.40 0.97  4.31 4.00 1.14  6.17 6.25 1.46  7.25 7.35 1.71 
200 0.04 0.04 0.00  0.05 0.05 0.00  0.08 0.10 0.03  0.10 0.12 0.03 
Ba 200 0.16 0.15 0.01  0.18 0.18 0.01  0.16 0.15 0.04  0.19 0.18 0.05 
Co 0.3 0.32 0.30 0.07  0.38 0.35 0.08  0.58 0.27 1.29  0.69 0.31 1.52 
Cr 0.05 0.03 0.04  0.05 0.03 0.05  0.10 0.06 0.22  0.12 0.07 0.26 
Cu 40 0.03 0.03 0.01  0.04 0.04 0.01  0.05 0.06 0.03  0.06 0.07 0.03 
Fe 700 0.05 0.01 0.10  0.06 0.01 0.12  0.25 0.07 0.76  0.30 0.08 0.89 
Mn 140 0.11 0.09 0.04  0.12 0.11 0.05  0.15 0.02 0.42  0.18 0.03 0.50 
Mo 0.05 0.04 0.01  0.05 0.05 0.01  0.07 0.07 0.01  0.08 0.08 0.01 
Ni 20 0.01 0.01 0.01  0.02 0.01 0.01  0.03 0.03 0.02  0.04 0.03 0.03 
Se 0.02 0.02 0.00  0.02 0.02 0.00  0.03 0.02 0.01  0.03 0.03 0.01 
Tl 0.01 1.23 1.22 0.19  1.45 1.43 0.22  1.32 1.22 0.60  1.56 1.43 0.70 
0.01 0.01 0.00  0.01 0.01 0.00  0.02 0.02 0.01  0.02 0.02 0.01 
Zn 300 0.02 0.01 0.04  0.02 0.01 0.04  0.01 0.01 0.01  0.01 0.01 0.01 
HI  6.03 5.65 1.61  7.09 6.65 1.89  9.42 8.44 5.99  11.08 9.92 7.05 
Tonle Sap River
Tonle Sap Great Lake
Female
Male
Female
Male
ElementsRfDMeanMedianSDMeanMedianSDMeanMedianSDMeanMedianSD
Ag 0.26 0.28 0.09  0.30 0.33 0.11  0.25 0.07 0.45  0.30 0.08 0.52 
Al 1000 0.02 0.01 0.02  0.02 0.01 0.02  0.14 0.03 0.64  0.16 0.03 0.75 
As 0.3 3.66 3.40 0.97  4.31 4.00 1.14  6.17 6.25 1.46  7.25 7.35 1.71 
200 0.04 0.04 0.00  0.05 0.05 0.00  0.08 0.10 0.03  0.10 0.12 0.03 
Ba 200 0.16 0.15 0.01  0.18 0.18 0.01  0.16 0.15 0.04  0.19 0.18 0.05 
Co 0.3 0.32 0.30 0.07  0.38 0.35 0.08  0.58 0.27 1.29  0.69 0.31 1.52 
Cr 0.05 0.03 0.04  0.05 0.03 0.05  0.10 0.06 0.22  0.12 0.07 0.26 
Cu 40 0.03 0.03 0.01  0.04 0.04 0.01  0.05 0.06 0.03  0.06 0.07 0.03 
Fe 700 0.05 0.01 0.10  0.06 0.01 0.12  0.25 0.07 0.76  0.30 0.08 0.89 
Mn 140 0.11 0.09 0.04  0.12 0.11 0.05  0.15 0.02 0.42  0.18 0.03 0.50 
Mo 0.05 0.04 0.01  0.05 0.05 0.01  0.07 0.07 0.01  0.08 0.08 0.01 
Ni 20 0.01 0.01 0.01  0.02 0.01 0.01  0.03 0.03 0.02  0.04 0.03 0.03 
Se 0.02 0.02 0.00  0.02 0.02 0.00  0.03 0.02 0.01  0.03 0.03 0.01 
Tl 0.01 1.23 1.22 0.19  1.45 1.43 0.22  1.32 1.22 0.60  1.56 1.43 0.70 
0.01 0.01 0.00  0.01 0.01 0.00  0.02 0.02 0.01  0.02 0.02 0.01 
Zn 300 0.02 0.01 0.04  0.02 0.01 0.04  0.01 0.01 0.01  0.01 0.01 0.01 
HI  6.03 5.65 1.61  7.09 6.65 1.89  9.42 8.44 5.99  11.08 9.92 7.05 

RfD, Reference Dose; SD, standard deviation

The total number of 19 trace elements (Ag, Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Ga, Mn, Mo, Ni, Pb, Se, Tl, U and Zn) in the Tonle Sap Great Lake and its tributary were determined. Cadmium was not detected in any river and lake waters. Comparisons did not show significant differences in Ag, Al, Ba, Co, Cr, Fe, Ga, Mn, Pb, Tl and Zn concentrations in the Great Lake and its tributary. However, As, B, Cu, Mo, Ni, Se and U concentrations in the Great Lake were significantly higher than those in the river. Concurrently, there were significant differences in Ag, As, B, Ba, Cu, Ga, Mn and Se among the five surrounding provinces of the Great Lake. Nevertheless, Al, Co, Cr, Fe, Mo, Ni, Pb, Tl, U and Zn were not significantly different among the five provinces. Although a number of river and lake water samples had certain trace elements greater than the average levels in the world natural rivers, only Al, Fe and Mn in lake water exceeded the regulation limits. When compared to lakes in other countries, the Tonle Sap Great Lake was less polluted than the others. Moreover, health risk assessment indicated that male and female Cambodian residents are at minimal risk of non-carcinogenic effects of single and mixed trace elements through lake and river water consumption. However, more attention should be paid to As, Tl, Co, Ba, Mn and Cr because they might pose high potential health risks to local residents. Therefore, regular monitoring and further investigations of temporal and spatial distribution are warranted to advance understanding of the pollution trends and toxic behavior of these trace elements in the Tonle Sap Great Lake system.

The authors would like to thank Mr Sundeth Say and Mr Rithy Aem for their invaluable field assistance.

This work was supported by GIST Research Institute (GRI) grant funded by the Gwangju Institute of Science and Technology (GIST) in 2023.

All authors read and approved the content of the final manuscript.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.

Burnett
W. C.
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