No abstract

Ozone (O3) is a key air pollutant that is produced from precursor emissions and has adverse impacts on human health and ecosystems. In the U.S., the Clean Air Act (CAA) regulates O3levels to protect public health and welfare, but unraveling the origins of surface O3is complicated by the presence of contributions from multiple sources including background sources like stratospheric transport, wildfires, biogenic precursors, and international anthropogenic pollution, in addition to U.S. anthropogenic sources. In this report, we consider more than 100 published studies and assess current knowledge on the spatial and temporal distribution, trends, and sources of background O3over the continental U.S., and evaluate how it influences attainment of the air quality standards. We conclude that spring and summer seasonal mean U.S. background O3(USB O3), or O3formed from natural sources plus anthropogenic sources in countries outside the U.S., is greatest at high elevation locations in the western U.S., with monthly mean maximum daily 8-hour average (MDA8) mole fractions approaching 50 parts per billion (ppb) and annual 4thhighest MDA8s exceeding 60 ppb, at some locations. At lower elevation sites, e.g., along the West and East Coasts, seasonal mean MDA8 USB O3is in the range of 20–40 ppb, with generally smaller contributions on the highest O3days. The uncertainty in U.S. background O3is around ±10 ppb for seasonal mean values and higher for individual days. Noncontrollable O3sources, such as stratospheric intrusions or precursors from wildfires, can make significant contributions to O3on some days, but it is challenging to quantify accurately these contributions. We recommend enhanced routine observations, focused field studies, process-oriented modeling studies, and greater emphasis on the complex photochemistry in smoke plumes as key steps to reduce the uncertainty associated with background O3in the U.S.

This paper reports daily and seasonal patterns of lighting use in offices where occupants were able to vary the level of illuminance falling on their working areas. The results show that occupants set a wide range of illuminances, many of which are significantly below CIBSE Code recommendations leading to significant energy savings throughout the year. Although users report use of controls for a variety of reasons, the results of the long-term monitoring of switching behaviour reveals that very few in fact use them for anything other than to switch on upon arrival at work, with further use of systems during the day being rare. Evidence suggests that the way in which systems are configured exerts influence over the level of electric light occupants work under. There is some evidence of an effect of daylight availability on levels set but little evidence to suggest pervasive and consistent user preferences for levels of electric light.

The use of locally addressable dimmable lighting systems has been examined in 14 open-plan office buildings. This paper discusses user attitudes toward control systems and the luminous conditions they produce. The majority of users are satisfied with both the quantity and quality of light on their workstations and are generally positive towards systems. This is despite large numbers of them working in illuminances significantly below current CIBSE recommendations. This indicates a significant potential for energy saving, since increased personal control leads to the use of lower lighting levels without detriment to occupants’ perceived lighting quality and visual comfort.

Laser-induced optoacoustic spectroscopy (LIOAS) measurements with carotene-porphyrin-acceptor "supermolecular" triads (C-P-A, with A = C60, a naphthoquinone NQ, and a naphthoquinone derivative, Q) were carried out with the purpose of analyzing the thermodynamic parameters for the formation and decay of the respective long-lived charge separated state C*+-P-A*-. The novel procedure of inclusion of the benzonitrile solutions of the triads in Triton X-100 micelle nanoreactors suspended in water permitted the separation of the enthalpic and structural volume change contributions to the LIOAS signals, by performing the measurements in the range 4-20 degrees C. Contractions of 4.2, 5.7, and 4.2 mL mol-1 are concomitant with the formation of C*+-P-A*- for A = C60, Q and NQ, respectively. These contractions are mostly attributed to solvent movements and possible conformational changes upon photoinduced electron transfer, due to the attraction of the oppositely charged ends, as a consequence of the giant dipole moment developed in these compounds upon charge separation ( approximately 110 D). The estimations combining the calculated free energies and the LIOAS-derived enthalpy changes indicate that entropy changes, attributed to solvent movements, control the process of electron transfer for the three triads, especially for C-P-C60 and C-P-Q. The heat released during the decay of 1 mol of charge separated state (CS) is much smaller than the respective enthalpy content obtained from the LIOAS measurements for the CS formation. This is attributed to the production of long-lived energy storing species upon CS decay.