Abstract. Monoterpenes, emitted in large quantities by trees to attract pollinators and repel herbivores, can exist in mirror image forms called enantiomers. In this study such enantiomeric pairs have been measured in ambient air over extensive forest ecosystems in South America and northern Europe. For the dominant monoterpene, α-pinene, the (−)-form was measured in large excess over the (+)-form over the Tropical rainforest, whereas the reverse was observed over the Boreal forest. Interestingly, over the Tropical forest (−)-α-pinene did not correlate with its own enantiomer, but correlated well with isoprene. The results indicate a remarkable ecosystem scale enantiomeric fingerprint and a nexus between the biosphere and atmosphere.

Abstract. During a field campaign at the Meteorological Observatory Hohenpeissenberg (MOHp) in July 2004, volatile organic compounds (VOCs) were measured using comprehensive two-dimensional gas chromatography (GC×GC). Comparison to routinely made gas chromatography mass spectrometry (GC-MS) measurements showed good agreement for a variety of anthropogenic and biogenic ambient VOCs ranging in concentration from below the detection limit (0.1 pmol mol −1 ) to 180 pmol mol −1 . Pronounced diurnal cycles were found for both the biogenic and anthropogenic compounds, driven for the most part by the daily rise and fall of the boundary layer over the station. For the reactive compounds (lifetimes <2 days), a significant, non-zero dependency of the variability on lifetime was found, indicating that chemistry (as opposed to transport alone) was playing a role in determining the ambient VOC concentrations. The relationship was exploited using a single-variate analysis to derive a daytime mean value of HO (5.3±1.4×10 6 molecules cm −3 ), which compares well to that measured at the site, 3.2±2.3×10 6 molecules cm −3 . The analysis was extended to the night time data to estimate concentrations for NO 3 (1.47±0.2×10 8 molecules cm −3 ), which is not measured at the site. The feasibility of this approach for environments dominated by emissions of shortlived VOCs to estimate ambient levels of radical species is discussed.

[1] In July-August 2002 the field measurement campaign Mineral Dust and Tropospheric Chemistry (MINATROC) was carried out at the Global Atmosphere Watch station at Izaña, Tenerife, to study the interaction of mineral dust aerosol and tropospheric chemistry. Organic trace gas mixing ratios were determined for the following: alkanes (e.g., propane); alkenes (isoprene); aromatic compounds (toluene); and oxygenated species (CO, methanol, formaldehyde, acetaldehyde, and acetone) simultaneously with aerosol measurements of dust. Local emissions of biogenic (isoprene and methanol) and anthropogenic compounds (CO and toluene) were observed at Izaña by day. Nighttime mixing ratios of organic species were interpreted as representative of the Atlantic free troposphere. A local production and loss budget for formaldehyde suggested that isoprene dominates production by day, and a significant dry deposition velocity is estimated at night of 0.74 cm/s. The total reactivity of the organic trace gases measured to OH is estimated as 1.7 s À1 by day and 0.7 s À1 by night. During the campaign a dense Saharan dust plume, with aerosol masses exceeding 500 mg m À3 , persisted for 3 days. Air masses containing dust appeared to be generally more polluted (in acetone and CO) than the prevailing westerly flow, but local biogenic emissions were little affected (e.g., methanol and isoprene). Although during the dust period the daily cycles and the absolute concentrations of some oxygenated species are different (e.g., acetaldehyde), these changes could not be attributed unequivocally to heterogeneous reactions on dust.

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Abstract. During a field campaign at the Meteorological Observatory Hohenpeissenberg (MOHp) in July 2004, VOCs were measured using GCxGC-FID. Comparison to routinely made GC-MS measurements showed good agreement for a variety of anthropogenic and biogenic ambient VOCs ranging in concentration from below the detection limit (0.1 pmol mol−1) to 180 pmol mol−1. Pronounced diurnal cycles were found for both the biogenic and anthropogenic compounds, driven for the most part by the daily rise and fall of the boundary layer over the station. For the reactive compounds (lifetimes <2 days), a significant, non-zero dependency of the variability on lifetime was found, indicating that chemistry (as opposed to transport alone) was playing a role in determining the ambient VOC concentrations. The relationship was exploited using a single-variate analysis to derive a daytime mean value of HO (5.3±1.4×106 molecules cm−3), which compares well to that measured at the site, 3.2±2.3×106 molecules cm−3. The analysis was extended to the night time data to estimate concentrations for NO3 (1.47±0.2×108 molecules cm−3), which is not measured at the site. The feasibility of this approach for environments dominated by emissions of short-lived VOCs to estimate ambient levels of radical species is discussed.