English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Elemental carbon (EC) has been widely used as a tracer to track the portionof co-emitted primary organic carbon (OC) and, by extension, to estimatesecondary OC (SOC) from ambient observations of EC and OC. Key to this ECtracer method is to determine an appropriate OC / EC ratio thatrepresents primary combustion emission sources (i.e.,(OC / EC)pri) at the observation site. The conventionalapproaches include regressing OC against EC within a fixed percentile of thelowest (OC / EC) ratio data (usually 5–20 %) or relying on a subsetof sampling days with low photochemical activity and dominated by localemissions. The drawback of these approaches is rooted in its empiricalnature, i.e., a lack of clear quantitative criteria in the selection of datasubsets for the (OC / EC)pri determination. We examine here amethod that derives (OC / EC)pri through calculating ahypothetical set of (OC / EC)pri and SOC followed by seekingthe minimum of the coefficient of correlation (R2) between SOC and EC.The hypothetical (OC / EC)pri that generates the minimumR2(SOC,EC) then represents the actual (OC / EC)pri ratioif variations of EC and SOC are independent and (OC / EC)pri isrelatively constant in the study period. This Minimum R Squared (MRS) methodhas a clear quantitative criterion for the (OC / EC)pricalculation. This work uses numerically simulated data to evaluate theaccuracy of SOC estimation by the MRS method and to compare with two commonlyused methods: minimum OC / EC (OC / ECmin) and OC / ECpercentile (OC / EC10 %). Log-normally distributed EC and OCconcentrations with known proportion of SOC are numerically produced througha pseudorandom number generator. Three scenarios are considered, including asingle primary source, two independent primary sources, and two correlatedprimary sources. The MRS method consistently yields the most accurate SOCestimation. Unbiased SOC estimation by OC / EC<mo>min</mo> andOC / EC10 % only occurs when the left tail of OC / ECdistribution is aligned with the peak of the (OC / EC)pridistribution, which is fortuitous rather than norm. In contrast, MRS providesan unbiased SOC estimation when measurement uncertainty is small. MRS resultsare sensitive to the magnitude of measurement uncertainty but the bias wouldnot exceed 23 % if the uncertainty is within 20 %

atmospheric chemistry and physics

Determination of primary combustion source organic carbon-to-elemental carbon (OC / EC) ratio using ambient OC and EC measurements: secondary OC-EC correlation minimization method