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Soro, Denmark

Gao H.,Environment Canada | Gao H.,Lanzhou University | Ma J.,Environment Canada | Cao Z.,Meteorological Service of Canada | And 2 more authors.
Journal of Geophysical Research: Atmospheres

Following worldwide bans or restrictions, the atmospheric level of many organochlorine pesticides (OCPs) over the Great Lakes exhibited a decreasing trend since the 1980s in various environmental compartments. Atmospheric conditions also influence variation and trend of OCPs. In the present study a nonparametric Mann-Kendall test with an additional process to remove the effect of temporal (serial) correlation was used to detect the temporal trend of OCPs in the atmosphere over the Great Lakes region and to examine the statistical significance of the trends. Using extended time series of measured air concentrations over the Great Lakes region from the Integrated Atmospheric Deposition Network, this study also revisits relationships between seasonal mean air concentration of OCPs and major climate variabilities in the Northern Hemisphere. To effectively extract climate signals from the temporal trend of air concentrations, we detrended air concentrations through removing their linear trend, which is driven largely by their respective half-lives in the atmosphere. The interannual variations of the extended time series show a good association with interannual climate variability, notably, the North Atlantic Oscillation (NAO) and the El Nio-Southern Oscillation. This study demonstrates that the stronger climate signals can be extracted from the detrended time series of air concentrations of some legacy OCPs. The detrended concentration time series also help to interpret, in addition to the connection with interannual variation of the NAO, the links between atmospheric concentrations of OCPs and decadal or interdecadal climate change. Copyright 2010 by the American Geophysical Union. Source

Chapra S.C.,Tufts University | Dove A.,Water Surveillance | Warren G.J.,U.S. EPA Great Lakes National Program Office
Journal of Great Lakes Research

Data from U.S. and Canadian federal monitoring programs are compiled to assess long-term trends of major ions in each of the Laurentian Great Lakes. Time series are developed for the primary cations and anions as well as for specific conductance and alkalinity. When combined with historical estimates, these modern datasets provide a 150-year overview of each lake's chemical makeup. Because of their long residence times, lakes Superior, Michigan and Huron exhibit persistent increases in most ions. For lakes Erie and Ontario, several ions (chloride, sodium, calcium and sulfate), as well as specific conductance, reached peak levels between 1965 and 1975, but then began to decline. The decreases are attributable to different mechanisms: industrial point discharge reductions (sodium, chloride), atmospheric loading declines (sulfate), and the introduction of exotic dreissenid mussels (calcium). Recent data indicate that these ions are now increasing again (chloride, sodium) or have leveled off (calcium, sulfate). The results establish how much the chemical makeup of the Great Lakes has changed due to anthropogenic influences, and underscore the importance of long-term, systematic, water-quality monitoring. © 2012 Elsevier B.V.. Source

Crowe A.S.,National Water Research Institute | Leclerc N.,Wasaga Beach Provincial Park | Struger J.,Water Surveillance | Brown S.,National Water Research Institute
Journal of Great Lakes Research

During the past decade, the invasive Phragmites australis (common reed) has established itself along beaches of the Great Lakes, causing detrimental impacts to both the natural ecological integrity of the shoreline and the recreational value of beaches. The herbicide Roundup®, containing the active ingredient glyphosate, was applied to Phragmites along a beach on the southern shore of Georgian Bay, Canada, to eradicate the Phragmites which was destroying the natural beach ecosystem. Groundwater and lake water were tested to determine if glyphosate enters the groundwater and lake at the beach and how long glyphosate will persist. Two days after application, the geometric mean concentration of glyphosate in the groundwater below the Phragmites was 0.060. μg/L with a maximum of 12.50. μg/L. Concentrations rapidly declined over the next two to three weeks to below minimum detection limits (<. 0.020. μg/L). Glyphosate was also detected in the nearshore lake water with concentrations peaking at a geometric mean of 0.14. μg/L one week after application, and declining to 0.039. μg/L four weeks after application. Concentrations of glyphosate never exceeded the Canadian water quality guideline for the protection of aquatic life (65. μg/L) in either the groundwater or lake water. An approximate half-life for the dissipation of glyphosate by degradation and dilution/flushing as groundwater flows toward the lake, assuming a first order kinetic reaction, yielded a half-life of 3.5 during the 4. weeks after the herbicide was applied. The application of Roundup® resulted in an 90% reduction in the size of the stand of Phragmites. © 2011. Source

Binding C.E.,Environment Canada | Greenberg T.A.,Environment Canada | Jerome J.H.,Environment Canada | Bukata R.P.,Environment Canada | Letourneau G.,Water Surveillance
Journal of Plankton Research

Lake of the Woods (LoW) is an international (USA/Canada) inland water body under significant water quality pressures from recurring cyanobacteria blooms. Its remote location combined with the hydrologically complex nature of its waters makes adequate in situ monitoring of the lake difficult. This work aimed to test the potential of Envisat's Medium Resolution Imaging Spectrometer (MERIS) full-resolution imagery for monitoring algal blooms in the lake. A full assessment of MERIS L1 and L2 chlorophyll and chlorophyll-related products was carried out over LoW during an intense surface algal bloom in September 2009. The Case 2 regional model and fluorescence line height/maximum chlorophyll index (MCI) plug-ins for BEAM were assessed for their ability to accurately distinguish the bloom. Results suggest that none of the Case-2-specific algorithms effectively extract chlorophyll concentrations over LoW, whereas the greatest potential is seen within the MCI product. Adjacency effects in near-shore waters are shown to be significant, although the improved contrast between ocean and land processor (ICOL) does not appear to notably improve water constituent retrievals in these waters. Images of L2 MCI are shown to adequately identify the bloom and are used to track the evolution of the bloom across the lake. Evidence is presented for the effects of variable depth distributions of cyanobacteria on the surface signal seen by the sensor; imagery suggests that day-to-day variations in wind-induced mixing have a profound impact on surface algal biomass as detected by remote sensing. Source

Malkin S.Y.,University of Waterloo | Dove A.,Water Surveillance | Depew D.,University of Waterloo | Smith R.E.,University of Waterloo | And 2 more authors.
Journal of Great Lakes Research

This study, motivated by a resurgence in Cladophora, investigates changes in the nutrient environment in the littoral zone of Lake Ontario. We measured nutrient concentrations from 2004 to 2008 at two littoral zone (2-12. m) sites on the north shore of Lake Ontario where Cladophora has experienced a resurgence and compared concentrations with data collected in the late 1970s. Spring total phosphorus (TP) and soluble reactive P (SRP) concentrations have significantly declined at these two sites. Furthermore, P loading from the major tributaries to our study sites declined between 1964 and 2008. Upwelling events were not detectably associated with increases in P concentrations at our sites. We conclude that a recent upsurge in nuisance Cladophora, at least at these sites, cannot be explained by deteriorating littoral zone water quality in terms of P concentrations or by changes in catchment loading. For additional context, we also examined trends in coastal (14-20. m) and offshore (>50. m) nutrients using Environment Canada epilimnetic surveillance data, 1975-2008. Significant declines in TP and SRP concentrations have occurred in north coast waters, concurrent with declines in the offshore. However, nutrient concentrations, notably spring SRP, have not decreased among south coast stations, potentially reflecting greater coastal entrapment of catchment-derived waters. We infer that EC-monitored north coast stations reflect integrated interannual water quality, while south coast stations are more strongly influenced by catchment loading. The effects of higher nutrient concentrations along the south coast, which co-occur with lower water transparency, on benthic algal growth have yet to be determined. © 2010. Source

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