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Simulation of the fate and seasonal variations of α-hexachlorocyclohexane in Lake Chaohu using a dynamic fugacity model.

Kong XZ, He W, Qin N, He QS, Yang B, Ouyang H, Wang Q, Yang C, Jiang Y, Xu F - ScientificWorldJournal (2012)

Bottom Line: Seasonal patterns in various media were successfully modeled and factors leading to this seasonality were discussed.Sensitivity analysis found that parameters of source and degradation were more important than the other parameters.Uncertainty analysis showed that the model uncertainty was relatively low but significantly increased in the second half of the simulation period due to the increase in the gas-water diffusion flux variability.

View Article: PubMed Central - PubMed

Affiliation: MOE Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China.

ABSTRACT
Fate and seasonal variations of α-hexachlorocyclohexane (α-HCH) were simulated using a dynamic fugacity model in Lake Chaohu, China. Sensitivity analyses were performed to identify influential parameters and Monte Carlo simulation was conducted to assess model uncertainty. The calculated and measured values of the model were in good agreement except for suspended solids, which might be due to disregarding the plankton in water. The major source of α-HCH was an input from atmospheric advection, while the major environmental outputs were atmospheric advection and sediment degradation. The net annual input and output of α-HCH were approximately 0.294 t and 0.412 t, respectively. Sediment was an important sink for α-HCH. Seasonal patterns in various media were successfully modeled and factors leading to this seasonality were discussed. Sensitivity analysis found that parameters of source and degradation were more important than the other parameters. The sediment was influenced more by various parameters than air and water were. Temperature variation had a greater impact on the dynamics of the model output than other dynamic parameters. Uncertainty analysis showed that the model uncertainty was relatively low but significantly increased in the second half of the simulation period due to the increase in the gas-water diffusion flux variability.

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Related in: MedlinePlus

Comparison between the simulated and measured α-HCH concentrations in the air, water, and sediment of Lake Chaohu. The error bars included in this figure represent the standard deviations.
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fig2: Comparison between the simulated and measured α-HCH concentrations in the air, water, and sediment of Lake Chaohu. The error bars included in this figure represent the standard deviations.

Mentions: The simulated annually average concentrations of α-HCH in the air, water, and sediment are shown in Figure 2 and were found to be in agreement with the measured data. The differences in the main phases were 0.21, 0.06, and 0.07 logarithmic units for the air, water, and sediment, respectively, which were all within 0.5 log units during the simulation. The air concentrations were underestimated, which might be due to various factors. On the other hand, in addition to the uncertainty of the model, the underestimation in the sediment may be due to the fact that the samples were collected in 2008, while the model simulation period was 2010-2011. The overestimation of the concentration in the water may have been due to the absence of a biological phase. Aquatic organisms, especially plankton, can substantially affect the fate of persistent organic pollutants (POPs) in the water environment [23]. It can be observed that the α-HCH concentration in the sediment particles was much higher than that in the atmosphere or in the water bodies. It was concluded that sediment is an important sink of α-HCH [24].


Simulation of the fate and seasonal variations of α-hexachlorocyclohexane in Lake Chaohu using a dynamic fugacity model.

Kong XZ, He W, Qin N, He QS, Yang B, Ouyang H, Wang Q, Yang C, Jiang Y, Xu F - ScientificWorldJournal (2012)

Comparison between the simulated and measured α-HCH concentrations in the air, water, and sediment of Lake Chaohu. The error bars included in this figure represent the standard deviations.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3539339&req=5

fig2: Comparison between the simulated and measured α-HCH concentrations in the air, water, and sediment of Lake Chaohu. The error bars included in this figure represent the standard deviations.
Mentions: The simulated annually average concentrations of α-HCH in the air, water, and sediment are shown in Figure 2 and were found to be in agreement with the measured data. The differences in the main phases were 0.21, 0.06, and 0.07 logarithmic units for the air, water, and sediment, respectively, which were all within 0.5 log units during the simulation. The air concentrations were underestimated, which might be due to various factors. On the other hand, in addition to the uncertainty of the model, the underestimation in the sediment may be due to the fact that the samples were collected in 2008, while the model simulation period was 2010-2011. The overestimation of the concentration in the water may have been due to the absence of a biological phase. Aquatic organisms, especially plankton, can substantially affect the fate of persistent organic pollutants (POPs) in the water environment [23]. It can be observed that the α-HCH concentration in the sediment particles was much higher than that in the atmosphere or in the water bodies. It was concluded that sediment is an important sink of α-HCH [24].

Bottom Line: Seasonal patterns in various media were successfully modeled and factors leading to this seasonality were discussed.Sensitivity analysis found that parameters of source and degradation were more important than the other parameters.Uncertainty analysis showed that the model uncertainty was relatively low but significantly increased in the second half of the simulation period due to the increase in the gas-water diffusion flux variability.

View Article: PubMed Central - PubMed

Affiliation: MOE Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China.

ABSTRACT
Fate and seasonal variations of α-hexachlorocyclohexane (α-HCH) were simulated using a dynamic fugacity model in Lake Chaohu, China. Sensitivity analyses were performed to identify influential parameters and Monte Carlo simulation was conducted to assess model uncertainty. The calculated and measured values of the model were in good agreement except for suspended solids, which might be due to disregarding the plankton in water. The major source of α-HCH was an input from atmospheric advection, while the major environmental outputs were atmospheric advection and sediment degradation. The net annual input and output of α-HCH were approximately 0.294 t and 0.412 t, respectively. Sediment was an important sink for α-HCH. Seasonal patterns in various media were successfully modeled and factors leading to this seasonality were discussed. Sensitivity analysis found that parameters of source and degradation were more important than the other parameters. The sediment was influenced more by various parameters than air and water were. Temperature variation had a greater impact on the dynamics of the model output than other dynamic parameters. Uncertainty analysis showed that the model uncertainty was relatively low but significantly increased in the second half of the simulation period due to the increase in the gas-water diffusion flux variability.

Show MeSH
Related in: MedlinePlus