Reassessing atmospheric deposition rates of polycyclic aromatic compounds to the Athabasca River (Alberta, Canada) watershed from oil sands related activities

نویسنده

  • Sierra Rayne
چکیده

In an earlier study (Kelly et al., PNAS, 2009, 106, 22346-22351), spatial patterns for the concentrations of particulate matter, particulate polycyclic aromatic compounds (PAC), and dissolved PAC in the snowpack around the Syncrude and Suncor upgrader facilities near the oil sands development at Fort McMurray, Alberta, Canada were determined. A reassessment of the datasets employed in this work yields significantly different deposition rates (by up to an order of magnitude) than reported, as well as reveals substantial sensitivity in deposition rate estimates depending on a range of equally valid regression types chosen. A high degree of uncertainty remains with regard to the quantities of particulate matter and PAC being deposited in the Athabasca River watershed from oil sands related activities. In their article, Kelly et al. [1] report on the spatial patterns for concentrations of particulate matter, particulate polycyclic aromatic compounds (PAC), and dissolved PAC in the snowpack around the Syncrude and Suncor upgrader facilities near the oil sands development at Fort McMurray, Alberta, Canada. From their sampling data and subsequent analysis, estimates of total loadings of these contaminants to snowpack over a 4 month period in 2008 were developed for a radius of 50 km around the oil sands upgrading facilities. Based on their data, the authors conduct negative exponential regression analysis and obtain the following equation describing the relationship between distance from the upgrading facilities and concentration of particulate matter: particulates=10.6×e−0.0714x g/m where x is the distance in km from site AR6. In ref. [1], the number of samples is given as 23. A data request from the authors of ref. [1] for their data behind Figure S2 in this work obtained a spreadsheet with 31 datapoints for each of the three variables. It is clear from Figure S2(a) in ref. [1] that this published figure also has 31 datapoints, of which 23 datapoints are within a 50 km radius of the upgraders. However, Fig. S2(a) in ref. [1] does not show an exponential regression with the equation y=10.6×e−0.0714x, as such an equation would have a y-intercept of 10.6. Instead, Fig. S2(a) in ref. [1] shows a regression equation with a yintercept of between 13 and 14. In the figure below is shown a negative exponential regression with the use of either 23 or 31 datapoints (as obtained from Kelly et al. [1]) from Fig. S2(a) as a black line (y=13.5×e−0.0707x; r=0.844; both n=23 and n=31 yield the same regression equation, as the datapoints at >50 km distance play negligible role in the regression constant fitting), and the authors’ claimed regression fit with an equation y=10.6×e−0.0714x as a red line. ∗Corresponding author: Tel/Fax: 1.250.487.0166 Email: [email protected]. a Chemologica Research, PO Box 74, 318 Rose Street, Mortlach, Saskatchewan, Canada, S0H 3E0. Using the regression equation given by the authors (y=10.6×e−0.0714x) and integrating the particulate concentration versus distance relationship to 50 km radius yields a total estimated deposition of 11,400 tons, equivalent to the value of 11,400 tons stated in ref. [1]. On the other hand, using the regression equation obtained from an analysis of the authors’ own data (black line in the figure above; y=13.5×e−0.0707x), which appears to match the regression equation shown in Fig. S2(a) of ref. [1], yields an integrated total deposition of 14,800 tons (i.e., 30% higher than the estimate in ref. [1]). An equally plausible fit (r=0.839) of the data is shown in the figure below, using the equation y=31.15×x−1.048. When integrated, this fit yields a total particulate deposition of 8,400 tons (i.e., 26% lower than the estimate in ref. [1]). Based on the significant sensitivity of loadings estimates to the type of regression equation chosen, quoting deposition estimates to 3 significant figures (as was done in ref. [1]) is not valid. A reasonable particulate loadings estimate range is probably best assigned as between 8,000 and 15,000 tons. Issues also exist with the analysis of particulate PAC (Fig. S2(b)) and dissolved PAC (Fig. S2(c)) loadings estimates. Kelly et al. [1] report the following particulate PAC concentration versus distance relationship, yet their own graph (Fig. S2(b) in ref. [1]) shows a regression line with a y-intercept of about 8: y=1.06×e−0.130x. When either all 31 datapoints are regressed using a negative single exponential fit, or just the n=23 at <50 km

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Has Alberta Oil Sands Development Altered Delivery of Polycyclic Aromatic Compounds to the Peace-Athabasca Delta?

BACKGROUND The extent to which Alberta oil sands mining and upgrading operations have enhanced delivery of bitumen-derived contaminants via the Athabasca River and atmosphere to the Peace-Athabasca Delta (200 km to the north) is a pivotal question that has generated national and international concern. Accounts of rare health disorders in residents of Fort Chipewyan and deformed fish in downstre...

متن کامل

Oil sands development contributes polycyclic aromatic compounds to the Athabasca River and its tributaries.

For over a decade, the contribution of oil sands mining and processing to the pollution of the Athabasca River has been controversial. We show that the oil sands development is a greater source of contamination than previously realized. In 2008, within 50 km of oil sands upgrading facilities, the loading to the snowpack of airborne particulates was 11,400 T over 4 months and included 391 kg of ...

متن کامل

Characterizing baseline concentrations, proportions, and processes controlling deposition of river-transported bitumen-associated polycyclic aromatic compounds at a floodplain lake (Slave River Delta, Northwest Territories, Canada)

Inadequate knowledge of baseline conditions challenges ability for monitoring programs to detect pollution in rivers, especially where there are natural sources of contaminants. Here, we use paleolimnological data from a flood-prone lake ("SD2", informal name) in the Slave River Delta (SRD, Canada), ∼ 500 km downstream of the Alberta oil sands development and the bitumen-rich McMurray Formation...

متن کامل

Unravelling the complexity of pollution by the oil sands industry.

Parajulee and Wania (1) make an important contribution to understanding the origin and magnitude of pollution caused by the massive oil sands industry in northeastern Alberta. Until recently, the oil sands industry and government officials have claimed that all pollutants carried by the lower Athabasca River system were the result of soil erosion, forest fires, and other natural phenomena. This...

متن کامل

Alberta oil sands development.

P olycyclic aromatic hydrocarbons (PAHs) are a ubiquitous class of hundreds of organic compounds composed of two or more aromatic rings that are released naturally and from human activities. Natural sources of PAHs include forest fires, oil seeps, and volcanic eruptions; anthropogenic sources include burning of fossil fuels and wood, production of coke and charcoal, petroleum refining, and petr...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2012