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Simulation of the fate and seasonal variations of ╬▒-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 ╬▒-hexachlorocyclohexane (╬▒-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 ╬▒-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 ╬▒-HCH were approximately 0.294 t and 0.412 t, respectively. Sediment was an important sink for ╬▒-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

Uncertainties of the predicted seasonal variations of ╬▒-HCH concentrations in various environmental media. The results are presented as median values (lines with dots) and semi-interquartile ranges (solid lines).
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fig8: Uncertainties of the predicted seasonal variations of ╬▒-HCH concentrations in various environmental media. The results are presented as median values (lines with dots) and semi-interquartile ranges (solid lines).

Mentions: The results of the uncertainty analysis for each phase are shown in Figure 8. It was found that the uncertainty of the model was relatively small from May to September, as represented by the small semi-interquartile ranges of the Monte Carlo simulation results. The uncertainty of the model output began to increase in October and peaked in December or January. This increase was attributed to our finding that from October to December, the coefficients of variation in the gas-water diffusion rate (K12 and K21) significantly increased, leading to an increase of variation in the air-water diffusion flux. This also contributed to a significant increase in the uncertainty of the other phases. Lang et al. [22] similarly found that the coefficient of variability of diffusion is associated with wide variability in the gaseous PAHs concentrations. The rates of diffusion across the gas-water interface (K12 and K21) were related to wind speed and water depth, and the coefficient of variation of water depth (h2) did not increase during OctoberÔÇôDecember. It can be speculated that elevated variation in the wind speed in this period causes the increasing uncertainty.


Simulation of the fate and seasonal variations of ╬▒-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)

Uncertainties of the predicted seasonal variations of ╬▒-HCH concentrations in various environmental media. The results are presented as median values (lines with dots) and semi-interquartile ranges (solid lines).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig8: Uncertainties of the predicted seasonal variations of ╬▒-HCH concentrations in various environmental media. The results are presented as median values (lines with dots) and semi-interquartile ranges (solid lines).
Mentions: The results of the uncertainty analysis for each phase are shown in Figure 8. It was found that the uncertainty of the model was relatively small from May to September, as represented by the small semi-interquartile ranges of the Monte Carlo simulation results. The uncertainty of the model output began to increase in October and peaked in December or January. This increase was attributed to our finding that from October to December, the coefficients of variation in the gas-water diffusion rate (K12 and K21) significantly increased, leading to an increase of variation in the air-water diffusion flux. This also contributed to a significant increase in the uncertainty of the other phases. Lang et al. [22] similarly found that the coefficient of variability of diffusion is associated with wide variability in the gaseous PAHs concentrations. The rates of diffusion across the gas-water interface (K12 and K21) were related to wind speed and water depth, and the coefficient of variation of water depth (h2) did not increase during OctoberÔÇôDecember. It can be speculated that elevated variation in the wind speed in this period causes the increasing uncertainty.

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 ╬▒-hexachlorocyclohexane (╬▒-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 ╬▒-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 ╬▒-HCH were approximately 0.294 t and 0.412 t, respectively. Sediment was an important sink for ╬▒-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