Fatty acids and polycyclic aromatic hydrocarbons (PAH) have been investigated as potential tracer species for the products of biomass burning. Fatty acids extracted from unburned sugar cane plants ...and from particulate aerosols collected during laboratory burns of sugar cane under smoldering and flaming conditions have been chemically and isotopically characterized by gas chromatography-mass spectrometry (GCMS) and gas chromatography-isotope ratio mass spectrometry (GCIRMS), respectively. Fatty acids and PAH produced during the burning of a sugar cane field in South Africa were similarly characterized. The fatty acids identified in the aerosols collected above the fire were saturated even-chain species ranging from C12 to C22. The carbon isotopic signatures of the fatty acids ranged between −19.9‰ and −23.6‰, and were more depleted in
13C than the bulk sugar cane plant (−12.9‰) and the total lipid extract (−17.9‰). The isotopic signatures of the individual fatty acids were conserved during the smoldering laboratory burn. However, the fatty acids collected during the flaming burn showed a depletion of 1‰ to 6‰ relative to the fatty acids extracted from the unburned plant. This observed depletion was even greater for the fatty acids obtained from the sugar cane field burn. Low levels of various PAH were identified in aerosols from the laboratory burns. Phenanthrene, fluoranthene and pyrene obtained from the field burn aerosols were isotopically depleted relative to the bulk lipid material, with carbon isotopic signatures ranging from −22.9‰ to −25.4‰. The alterations in the isotopic compositions of fatty acids that occur during combustion provide variables by which burn-derived compounds can be distinguished from those produced from aeolian transport of detrital vegetative matter. The combination of fatty acid isotopic data and PAH data may allow a better understanding of the relative contributions of biogenic and anthropogenic source materials to aerosols.
ABSTRACT
The solar ultraviolet radiation (UVR) exposure of 30 children and adolescents in three age groups (4–6 years, 7–9 years and 13–14 years) was measured for 1 week in late summer ...(February–March) in Durban, South Africa, using UVR‐sensitive polysulfone film badges (PSFB) attached to the lapel region of the body. The mean and median values for all ages over the study period were 2.0 and 1.2 standard erythemal dose (SED) units, respectively, where 1 SED = 100 J·m−2. Individual PSFB doses were analyzed as a function of age, gender and behavior. No significant statistical differences were found between different age groups; however, there was a statistical difference between males and females, with males generally receiving higher PSFB doses. Subjects completed UVR exposure journals documenting their time outdoors, shade versus sun conditions, nature of their activities, clothing worn and their use of sunscreen for each day of the study. Activity patterns were noted as the most important factor influencing individual UVR dose. Ambient erythemal UVR was measured by a Yankee Environmental Systems UVB pyranometer, and a relationship between ambient UVR and individual UVR dose was derived. On average, subjects received a dose of 4.6% of the total daily erythemal UVR. Based on this factor, the potential dose of an individual over a full annual cycle was estimated. Accordingly, there were 139 days during the year when an individual with skin type I (light skin) would be likely to experience minimal erythema and 97 and 32 days for individuals with skin types II and III, respectively.
Exposure to high levels of erythemal ultraviolet radiation (EUVR) is known to have adverse effects on human health. Certain parts of the human body are more susceptible to high EUVR exposure than ...others. The EUVR exposure of 26 anatomical sites on a mannequin was quantified on clear-sky and overcast days using polysulphone film. On clear-sky days, horizontal anatomical sites received the highest EUVR exposure. Facial exposure ranged between 19% and 56% of the vertex of the head. The hand and arm also received relatively high EUVR exposure (>50% of the vertex). Vertical surfaces averaged 38% of the vertex. These percentages compared closely with those of similar studies conducted elsewhere. EUVR exposure received across all anatomical sites on an overcast day was approximately 30% of that received on a clear-sky day.
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