Comparison of Mercury and Lead Sediment Concentrations in Lake Ontario (1968-1998) and Lake Erie (1971–1997/98) using a GIS-Based Kriging Approach

Forsythe, K. Wayne; Michael, Dennis; Märvin, Chris H.

doi:10.2166/wqrj.2004.028

Cited by 28 publications

(31 citation statements)

References 25 publications

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“…In all cases, empirical semi-variograms generated on an hourly basis were fit with a spherical model. Table 2 presents a summary of cross-validation statistics generated using output from each hour of apparent temperature in accordance with the selected model and level of global trend removal performed prior to undertaking surface interpolation with OK. Cross-validation results were judged to be robust, falling within the parameters generally established in the literature (Diodato 2005;Forsythe et al 2004). In general, our models show a slight tendency towards overestimation of apparent temperature (RMSSE<1).…”

Section: Resultssupporting

confidence: 74%

A spatio-temporal index for heat vulnerability assessment

Kershaw

Millward

2012

Environ Monit Assess

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The public health consequences of extreme heat events are felt most intensely in metropolitan areas where population density is high and the presence of the urban heat island phenomenon exacerbates the potential for prolonged exposure. This research develops an approach to map potential heat stress on humans by combining temperature and relative humidity into an index of apparent temperature. We use ordinary kriging to generate hourly prediction maps describing apparent temperature across the Greater Toronto Area, Canada. Meteorological data were obtained from 65 locations for 6 days in 2008 when extreme heat alerts were issued for the City of Toronto. Apparent temperature and exposure duration were integrated in a single metric, humidex degree hours (HDH), and mapped. The results show a significant difference in apparent temperature between built and natural locations from 3 PM to 7 AM; this discrepancy was greatest at 12 AM where built locations had a mean of 2.8 index values larger, t(71) = 5.379, p < 0.001. Spatial trends in exposure to heat stress (apparent temperature, ≥ 30°C) show the downtown core of the City of Toronto and much of Mississauga (west of Toronto) as likely to experience hazardous levels of prolonged heat and humidity (HDH ≥ 72) during a heat alert. We recommend that public health officials use apparent temperature and exposure duration to develop spatially explicit heat vulnerability assessment tools; HDH is one approach that unites these risk factors into a single metric.

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Section: Resultssupporting

confidence: 74%

A spatio-temporal index for heat vulnerability assessment

Kershaw

Millward

2012

Environ Monit Assess

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“…In contrast with many point interpolation methods, ordinary kriging offers the important advantage of optimizing interpolation weights assigned to data such that the variance of the estimation error is minimized (Bailey and Gatrell 1995;Forsythe et al 2004). Furthermore, because it is based upon a probabilistic model (the semivariogram), it enables the creation of a prediction standard error surface (Johnston et al 2001).…”

Section: Data Analysesmentioning

confidence: 99%

Naturalization as a strategy for improving soil physical characteristics in a forested urban park

2011

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Ensuring good soil quality is essential to promoting plant growth in urban parks and building ecological resilience into a cityscape. Periodically used to restore a degraded urban ecosystem, parkland naturalization is a management approach designed to facilitate the return of an area to a natural state by largely discontinuing maintenance activities and restricting public access. This study investigates the potential for parkland naturalization to improve soil quality in a forested portion of Kew Gardens Park, Toronto, Canada by comparing soil physical properties in three six-year-old naturalization enclosures with those found in adjacent managed parkland. Soil texture, compaction, bulk density, and surface water infiltration rate were measured at 104 sample sites, while ordinary kriging was used to interpolate two-dimensional prediction surfaces representative of soil properties. Sand and loamy sand were the dominant soil texture classes found across the study site. Highly compacted soil (>2,000 kPa) and soil with a bulk density >1.8 Mg/m 3 (values sufficiently elevated to restrict tree root growth and respiration and impair soil water infiltration) were spatially correlated with high pedestrian traffic areas and corridors used by festival and park maintenance vehicles. In contrast, compaction and bulk density measurements in the naturalized areas were at or below thresholds known to impair root function (X at 10 and 30 cm depth: 849 and 1,311 kPa, 1.15 and 1.51 Mg/m 3 , respectively). Similarly, water infiltration rates were rapid X ¼ 470 mm=hr À Á within the naturalization enclosures but retarded to the point of surface pooling in parkland subjected to regular public use. In the absence of quantitative baseline data, our use of spatial analysis demonstrates that parkland naturalization is a good management practice for restoration of soil physical characteristics. While our results show improvements to soil properties in a relatively short period of time, variability in the soil response rate to parkland naturalization will be dependent upon disturbance history as well as on soil and climate type.

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“…A significant amount of Hg data in surficial sediments is available for Lake Michigan (Rossmann, 2002), Lake Superior (Kerfoot et al, 2004;Rossmann, 1999), Lake Ontario (Forsythe et al, 2004;Marvin et al, 2004), Lake Huron (Gewurtz et al, 2008) and Lake Erie (Forsythe et al, 2004). Lacking in many of the sediment studies is the associated sediment accumulation rates critical to determining burial rates for mercury and other contaminants.…”

Section: Introductionmentioning

confidence: 99%