Great Lakes total phosphorus revisited: 2. Mass balance modeling

被引:83
作者
Chapra, Steven C. [1 ]
Dolan, David M. [2 ]
机构
[1] Tufts Univ, Civil & Environm Engn Dept, Medford, MA 02155 USA
[2] Univ Wisconsin Green Bay, Green Bay, WI 54311 USA
关键词
Phosphorus; Chloride; Model; Eutrophication; Mussels; Dreissenid; LONG-TERM TRENDS; WATER-QUALITY; ROUND GOBIES; ZEBRA; IMPACTS; ONTARIO; ERIE; PHYTOPLANKTON; PREDATION; DREISSENA;
D O I
10.1016/j.jglr.2012.10.002
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
Mass balance models are used to simulate chloride and total phosphorus (TP) trends from 1800 to the present for the North American Great Lakes. The chloride mass balance is employed to estimate turbulent eddy diffusion between model segments. Total phosphorus (TP) concentrations are then simulated based on estimated historical and measured TP loading time series. Up until about 1990, simulation results for all parts of the system generally conform to measured TP concentrations and exhibit significant improvement due primarily to load reductions from the Great Lakes Water Quality Agreement. After 1990, the model simulations diverge from observed data for the offshore waters of all the lakes except Lake Superior with the observations suggesting a greater improvement than predicted by the model. The largest divergence occurs in Lake Ontario where the model predicts that load reductions should bring the lake to oligo-mesotrophic levels, whereas the data indicate that it is solidly oligotrophic and seems to be approaching an ultra-oligotrophic state. Less dramatic divergences also occur in the offshore waters of lakes Michigan, Huron and Erie. In order to simulate these outcomes, the model's apparent settling velocity, which parameterizes the rate that total phosphorus is permanently lost to the lake's deep sediments, must be increased significantly after 1990. This result provides circumstantial support for the hypothesis that Dreissenid mussels have enhanced the Great Lakes phosphorus assimilation capacity. Finally, all interlake mass transfers of TP via connecting channels have dropped since phosphorus control measures were implemented beginning in the mid-1970s. (C) 2012 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved.
引用
收藏
页码:741 / 754
页数:14
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