Decades of air quality improvements have substantially reduced the motor vehicle emissions of volatile organic compounds (VOCs). Today, volatile chemical products (VCPs) are responsible for half of the petrochemical VOCs emitted in major urban areas. We show that VCP emissions are ubiquitous in US and European cities and scale with population density. We report significant VCP emissions for New York City (NYC), including a monoterpene flux of 14.7 to 24.4 kg ⋅ d−1 ⋅ km−2 from fragranced VCPs and other anthropogenic sources, which is comparable to that of a summertime forest. Photochemical modeling of an extreme heat event, with ozone well in excess of US standards, illustrates the significant impact of VCPs on air quality. In the most populated regions of NYC, ozone was sensitive to anthropogenic VOCs (AVOCs), even in the presence of biogenic sources. Within this VOC-sensitive regime, AVOCs contributed upwards of ∼20 ppb to maximum 8-h average ozone. VCPs accounted for more than 50% of this total AVOC contribution. Emissions from fragranced VCPs, including personal care and cleaning products, account for at least 50% of the ozone attributed to VCPs. We show that model simulations of ozone depend foremost on the magnitude of VCP emissions and that the addition of oxygenated VCP chemistry impacts simulations of key atmospheric oxidation products. NYC is a case study for developed megacities, and the impacts of VCPs on local ozone are likely similar for other major urban regions across North America or Europe.
Based on HYDROLIGHT simulations of more than 2000 reflectance spectra from datasets typical of coastal waters with highly variable optically active constituents as well as on intercomparisons with field measurements, the magnitude of chlorophyll fluorescence was analyzed and parameterized as a function of phytoplankton, CDOM, and suspended inorganic matter concentrations. Using the parameterizations developed, we show that variations in the fluorescence component of water leaving radiance in coastal waters are due more to the variability of attenuation in the water than to the variability of the fluorescence quantum yield, which we estimate to be relatively stable at around 1%. Finally, the ranges of water conditions where fluorescence plays a significant role in the reflectance NIR peak and where it is effectively undetectable are also determined.
Karenia brevis (K. brevis) blooms are of great interest and have been commonly reported throughout the Gulf of Mexico. In this study we propose a detection technique for blooms with low backscatter characteristics, which we name the Red Band Difference (RBD) technique, coupled with a selective K. brevis bloom classification technique, which we name the K. brevis Bloom Index (KBBI). These techniques take advantage of the relatively high solar induced chlorophyll fluorescence and low backscattering of K. brevis blooms. The techniques are applied to the detection and classification of K. brevis blooms from Moderate Resolution Imaging Spectroradiometer (MODIS) ocean color measurements off the Gulf of Mexico. To assess the efficacy of the techniques for detection and classification, simulations, including chlorophyll fluorescence (assuming 0.75% quantum yield) based on K. brevis blooms and non-K. brevis blooms conditions were performed. These show that effective bloom detection from satellite measurements requires a threshold of RBD>0.15W/m(2)/microm/sr, corresponding to about 5mg/m(3) of chlorophyll. Blooms can be detected at lower concentration by lowering the RBD threshold but false positives may increase. The classification technique is found most effective for thresholds of RBD>0.15W/m(2)/microm/sr and KBBI>0.3*RBD. The techniques were applied and shown to be effective for well documented blooms of K. brevis in the Gulf of Mexico and compared to other detection techniques, including FLH approaches. Impacts of different atmospheric corrections on results were also examined.
We have studied solid Ceo, measuring the shift of the optical absorption edge with pressure to 35 GPa. In the range of 0-17 GPa, extrapolation of the absorption edge indicates that metallization should occur by 33 GPa. However, from 17 to 25 GPa an irreversible transition to a "transparent phase" occurs. Raman scattering of the depressurized sample shows no trace of CM, diamond, or graphite, indicating that the transition involves the collapse of the C6o molecules into a new structure of carbon. PACS numbers: 64.70.Kb, 78.20.Dj, 78.30.HvRecently there have been a number of fascinating results on the properties of fullerite (solid C6o) at ambient conditions and at high pressure. These include observations of high-7V superconductivity [1] in doped fullerite and speculations that compressed fullerite might be harder than diamond [2]. In this work we intended to study the insulator-metal (IM) transition in pure fullerite and its ultrahigh pressure compressibility, as a material which hardens with increasing pressure might have important technological implications. We pressurized fullerite to 35 GPa in a diamond-anvil cell (DAC) and studied its optical absorption spectrum and Raman scattering cross section. Initially, with increasing pressure, the optical absorption threshold energy (ATE) shifts to lower energy, implying that fullerite should metallize in the 30-40 GPa pressure range. However, in the range 17-25 GPa the fullerite undergoes a sluggish irreversible transformation to a phase with reduced optical density; the transition is accelerated by raising the pressure to 35 GPa. Upon reducing the pressure to zero the sample does not revert to the low-pressure fullerite phase. Raman scattering measurements showed no trace of the C60 molecules so we conclude that the C6o molecules have collapsed. Furthermore, the Raman spectra of the collapsed fullerite (CF) phase cannot be identified with that of diamond or graphite, so we conclude that the CF phase is a new phase of carbon existing at zero pressure.High-purity C 6 o (less than 1% C70 content) was vacuum evaporated onto a diamond culet to form a rather uniform homogeneous film with a thickness of 2.5 //m, as measured by optical interference techniques. A few grains of ruby were scattered on the sample for pressure determination. A T301 stainless-steel gasket with a 100-//m-diam hole was placed over the sample and mounted in the DAC. We used xenon as a quasihydrostatic pressure medium; this was loaded cryogenically [3]. Measurements presented in this Letter were made at room temperature (295 K). Raman scattering was carried out using the 5145-A argon ion laser line and a Spex Triplemate monochromator with a Tracor Northern diode array. Laser power fluence was restricted to below 300 W/cm 2 to prevent overheating and burning or thermal deformation of the samples. Absorption spectroscopy was carried out in the visible; spectra were normalized to the transmission of a suitable pinhole. Pressure was measured using the ruby fluorescence scale [4] and was quasihydrostatic:...
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