The magnitude and sources of chlorine atoms in marine air remain highly uncertain but have potentially important consequences for air quality in polluted coastal regions. We made continuous measurements of ambient ClNO2 and Cl-2 concentrations from May 15 to June 8 aboard the Research Vessel Atlantis during the CalNex 2010 field study. In the Los Angeles region, ClNO2 was more ubiquitous than Cl-2 during most nights of the study period. ClNO2 and Cl-2 ranged from detection limits at midday to campaign maximum values at night reaching 2100 and 200 pptv, respectively. The maxima were observed in Santa Monica Bay when sampling the Los Angeles urban plume. Cl-2 at times appeared well correlated with ClNO2, but at other times, there was little to no correlation implying distinct and varying sources. Well-confined Cl-2 plumes were observed, largely independent of ClNO2, providing support for localized industrial emissions of reactive chlorine. Observations of ClNO2, Cl-2, and HCl are used to constrain a simple box model that predicts their relative importance as chlorine atom sources in the polluted marine boundary layer. In contrast to the emphasis in previous studies, ClNO2 and HCl are dominant primary chlorine atom sources for the Los Angeles basin.
This note extends Matsuyama's 0–1 endogenous retirement choice model to the framework with continuous endogenous retirement choice to study the consumption‐saving decision and capital accumulation in an overlapping generation model. The conditions for the existence of multiple steady states have been derived. In contrast to the 0 or 1 labour choice, the partial retirement may be a stable steady state under the continuous endogenous retirement choice in the second period. And this implies that partial retirement may be a stable optimal choice. Also, we find that the retirement choice depends on the initial capital stock when there are multiple steady states.
The Whistler Aerosol and Cloud Study (WACS 2010), included intensive measurements of trace gases and particles at two sites on Whistler Mountain. Between 6-11 July 2010 there was a sustained high-pressure system over the region with cloud-free conditions and the highest temperatures of the study. During this period, the organic aerosol concentrations rose from < 1 mu g m(-3) to similar to 6 mu g m(-3). Precursor gas and aerosol composition measurements show that these organics were almost entirely of secondary biogenic nature. Throughout 6-11 July, the anthropogenic influence was minimal with sulfate concentrations < 0.2 mu g m(-3) and SO2 mixing ratios approximate to 0.05-0.1 ppbv. Thus, this case provides excellent conditions to probe the role of biogenic secondary organic aerosol in aerosol microphysics. Although SO2 mixing ratios were relatively low, box-model simulations show that nucleation and growth may be modeled accurately if J(nuc) = 3 x 10(-7)[H2SO4] and the organics are treated as effectively non-volatile. Due to the low condensation sink and the fast condensation rate of organics, the nucleated particles grew rapidly (2-5 nm h(-1)) with a 10-25% probability of growing to CCN sizes (100 nm) in the first two days as opposed to being scavenged by coagulation with larger particles. The nucleated particles were observed to grow to similar to 200 nm after three days. Comparisons of size-distribution with CCN data show that particle hygroscopicity (kappa) was similar to 0.1 for particles larger 150 nm, but for smaller particles near 100 nm the kappa value decreased near midway through the period from 0.17 to less than 0.06. In this environment of little anthropogenic influence and low SO2, the rapid growth rates of the regionally nucleated particles - due to condensation of biogenic SOA - results in an unusually high efficiency of conversion of the nucleated particles to CCN. Consequently, despite the low SO2, nucleation/growth appear to be the dominant source of particle number.
Ambient OH and HO2 concentrations were measured by laser induced fluorescence (LIF) during the PRIDE-PRD2006 (Program of Regional Integrated Experiments of Air Quality over the Pearl River Delta, 2006) campaign at a rural site downwind of the megacity of Guangzhou in Southern China. The observed OH concentrations reached daily peak values of (15-26) x 10(6) cm(-3) which are among the highest values so far reported for urban and suburban areas. The observed OH shows a consistent high correlation with j((OD)-D-1) over a broad range of NOx conditions. The correlation cannot be reproduced by model simulations, indicating that OH stabilizing processes are missing in current models. The observed OH exhibited a weak dependence on NOx in contrast to model predictions. While modelled and measured OH agree well at NO mixing ratios above 1 ppb, a continuously increasing underprediction of the observed OH is found towards lower NO concentrations, reaching a factor of 8 at 0.02 ppb NO. A dependence of the modelled-to-measured OH ratio on isoprene cannot be concluded from the PRD data. However, the magnitude of the ratio fits into the isoprene dependent trend that was reported from other campaigns in forested regions. Hofzumahaus et al. (2009) proposed an unknown OH recycling process without NO, in order to explain the high OH levels at PRD in the presence of high VOC reactivity and low NO. Taking a recently discovered interference in the LIF measurement of HO2 into account, the need for an additional HO2 -> OH recycling process persists, but the required source strength may be up to 20% larger than previously determined. Recently postulated isoprene mechanisms by Lelieveld et al. (2008) and Peeters and Muller (2010) lead to significant enhancements of OH expected for PRD, but an underprediction of the observed OH by a factor of two remains at low NO (0.1-0.2 ppb). If the photolysis of hydroperoxy aldehydes from isoprene is as efficient as proposed by Peeters and Muller (2010), the corresponding OH formation at PRD would be more important than the primary OH production from ozone and HONO. While the new isoprene mechanisms need to be confirmed by laboratory experiments, there is probably need for other, so far unidentified chemical processes to explain entirely the high OH levels observed in Southern China.
Ambient OH and HO2 concentrations were measured by laser induced fluorescence (LIF) during the PRIDE-PRD2006 (Program of Regional Integrated Experiments of Air Quality over the Pearl River Delta, 2006) campaign at a rural site downwind of the megacity of Guangzhou in Southern China. The observed OH concentrations reached daily peak values of (15-26) x 10(6) cm(-3) which are among the highest values so far reported for urban and suburban areas. The observed OH shows a consistent high correlation with j((OD)-D-1) over a broad range of NOx conditions. The correlation cannot be reproduced by model simulations, indicating that OH stabilizing processes are missing in current models. The observed OH exhibited a weak dependence on NOx in contrast to model predictions. While modelled and measured OH agree well at NO mixing ratios above 1 ppb, a continuously increasing underprediction of the observed OH is found towards lower NO concentrations, reaching a factor of 8 at 0.02 ppb NO. A dependence of the modelled-to-measured OH ratio on isoprene cannot be concluded from the PRD data. However, the magnitude of the ratio fits into the isoprene dependent trend that was reported from other campaigns in forested regions. Hofzumahaus et al. (2009) proposed an unknown OH recycling process without NO, in order to explain the high OH levels at PRD in the presence of high VOC reactivity and low NO. Taking a recently discovered interference in the LIF measurement of HO2 into account, the need for an additional HO2 -> OH recycling process persists, but the required source strength may be up to 20% larger than previously determined. Recently postulated isoprene mechanisms by Lelieveld et al. (2008) and Peeters and Muller (2010) lead to significant enhancements of OH expected for PRD, but an underprediction of the observed OH by a factor of two remains at low NO (0.1-0.2 ppb). If the photolysis of hydroperoxy aldehydes from isoprene is as efficient as proposed by Peeters and Muller (2010), the corresponding OH formation at PRD would be more important than the primary OH production from ozone and HONO. While the new isoprene mechanisms need to be confirmed by laboratory experiments, there is probably need for other, so far unidentified chemical processes to explain entirely the high OH levels observed in Southern China.