Comparison of CTO-375 EC with A) IMPROVE-550 ECR, B) IMPROVE-550 ECT, C) STN60 ECR, and D) STN60 ECT.

<p>The relationship between CTO-375 EC and IMPROVE soot (EC2+EC3 by IMPROVE-550) for E) all dust and soil samples as well as F) those excluding two samples (red circles in E) with high EC1 are also presented. All concentrations are in mg g^-1. Robust linear regression was used for all the analyses.</p

Laser signal changes, i.e., ∆R_min and ∆T_min (the minimum R and T minus the corresponding initial R and T) among the four different protocols (IMPROVE-550 vs. IMPROVE-675 in (A)-(B) and STN60 vs. STN120 in (C)-(D)), which serve as indicators for the degree of pyrolysis.

<p>UD stands for urban dust and S stands for soil. See supplement <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0083462#pone.0083462.s001" target="_blank">Figure S1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0083462#pone.0083462.s005" target="_blank">Table S1</a> for sample IDs.</p

Thermograms of A) the conventional IMPROVE (Interagency Monitoring of Protected Visual Environments) and B) the STN (Speciation Trends Network) protocols (for sample UD-2).

<p>Thermograms of A) the conventional IMPROVE (Interagency Monitoring of Protected Visual Environments) and B) the STN (Speciation Trends Network) protocols (for sample UD-2).</p

Comparison of ECT (EC with transmittance correction) between IMPROVE-550 and other three protocols using robust linear regression.

<p>(A)-(C): in urban dust samples with relatively high percentage of soot contents and (D)-(F) in soil samples with relatively low soot contents.</p