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Issue 1, 2010
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A comparison of total maximum daily load (TMDL) calculations in urban streams using near real-time and periodic sampling data

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Abstract

A network of in situ sensors and nutrient analyzers was deployed to measure nitrate, specific conductance (surrogate for chloride), and turbidity (surrogate for total suspended solids (TSS)) for 28 days in two urban streams near Minneapolis, MN. The primary objectives of the study were: (1) to determine the accuracy associated with quantifying pollutant loading using periodic discrete (i.e., grab) samples in comparison to in situ near real-time monitoring and (2) to identify pollutant sources. Within a highly impervious drainage area (>35%) the majority of pollutant load (>90% for nitrate, chloride, and TSS) was observed to be discharged in a small percentage of time (<20%). Consequently, periodic sampling is prone to underestimate pollutant loads. Additionally, when compared to loads based on near real-time sampling, average errors of 19–200% were associated with sampling 1–2 times a month. There are also limitations of periodic sampling with respect to pollutant source determination. Resulting implications with regard to total maximum daily load (TMDL) assessments are discussed.

Graphical abstract: A comparison of total maximum daily load (TMDL) calculations in urban streams using near real-time and periodic sampling data

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Publication details

The article was received on 01 Jul 2009, accepted on 14 Sep 2009 and first published on 12 Nov 2009


Article type: Paper
DOI: 10.1039/B912990A
Citation: J. Environ. Monit., 2010,12, 234-241
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    A comparison of total maximum daily load (TMDL) calculations in urban streams using near real-time and periodic sampling data

    M. B. Henjum, R. M. Hozalski, C. R. Wennen, P. J. Novak and W. A. Arnold, J. Environ. Monit., 2010, 12, 234
    DOI: 10.1039/B912990A

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