The aim of this study was to assess the pollution status of metals in sediments of Hara Biosphere Reserve using pollution indicators. For this purpose, sediment samples from nine locations were collected and characterized for metal content (Pb, Cr, Zn, Cu, and Fe) using the total digestion technique. Comparison of metal concentrations with that of sediment quality guidelines (SQGs) demonstrated no association with negative biological effects for Cu and Zn, while the values of Pb and Cr mainly illustrated to have association with negative biological effects. The results of the geo-accumulation index (Igeo) indicated no contamination for Cr, Cu, Zn, and Fe, while the values of Pb demonstrated to have moderate contamination based on I geo values. The analysis of the enrichment factor (EF) showed no enrichment for Cu and Zn and minor enrichment for Pb and Cr. Similar results were also found for quantification of contamination (QoC) analysis, where the values of Cu and Zn demonstrated to have a geogenic source of contamination, while the values of Pb and Cr mainly illustrated to have an anthropogenic source of contamination. According to EF and QoC calculations, the values of Cu and Zn were derived mainly from natural processes and exposure of material from the earth's crust, while the values for Pb and Cr were enriched by anthropogenic activities. The results of the contamination factor (Cf(i)) demonstrated low contamination levels for Fe, Cr, Zn, and Cu and moderate contamination levels for Pb. The pollution load index (PLI), showing the overall contamination of metals, demonstrated moderate pollution status in the study area.
Vehicle
emissions are an important source of urban particular matter.
To investigate the secondary organic aerosol (SOA) formation potential
of real-world vehicle emissions, we exposed on-road air in Beijing
to hydroxyl radicals generated in an oxidation flow reactor (OFR)
under high-NO
x
conditions on-board a mobile
laboratory and characterized SOA and their precursors with a suite
of state-of-the-art instrumentation. The OFR produced 10–170
μg m–3 of SOA with a maximum SOA formation
potential of 39–50 μg m–3 ppmv–1 CO that occurred following an integrated OH exposure
of (1.3–2.0) × 1011 molecules cm–3 s. The results indicate relatively shorter photochemical ages for
maximum SOA production than previous OFR results obtained under low-NO
x
conditions. Such timescales represent the
balance of functionalization and fragmentation, possibly resulting
in different spatial distributions of SOA in different seasons as
the oxidant level changes. The detected precursors may explain as
much as 13% of the observed SOA with the remaining plausibly contributed
by the oxidation of undetected intermediate-volatility organic compounds.
Extrapolation of the results suggests an annual SOA production rate
of 0.78 Tg yr–1 from mobile gasoline sources in
China, highlighting the importance of effective regulation of gaseous
vehicular precursors to improve air quality in the future.
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