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Abstract. The San Joaquin Valley (SJV) experiences some of the worst ozone air quality in the US, frequently exceeding the California 8 h standard of 70.4 ppb. To improve our understanding of trends in the number of ozone violations in the SJV, we analyze observed relationships between organic reactivity, nitrogen oxides (NO x ), and daily maximum temperature in the southern SJV using measurements made as part of California at the Nexus of Air Quality and Climate Change in 2010 (CalNex-SJV). We find the daytime speciated organic reactivity with respect to OH during CalNex-SJV has a temperature-independent portion with molecules typically associated with motor vehicles being the major component.Published by Copernicus Publications on behalf of the European Geosciences Union. S. E. Pusede et al.: Temperature-dependent impacts of emission controlsAt high temperatures, characteristic of days with high ozone, the largest portion of the total organic reactivity increases exponentially with temperature and is dominated by small, oxygenated organics and molecules that are unidentified. We use this simple temperature classification to consider changes in organic emissions over the last and next decade. With the CalNex-SJV observations as constraints, we examine the sensitivity of ozone production (P O 3 ) to future NO x and organic reactivity controls. We find that P O 3 is NO x -limited at all temperatures on weekends and on weekdays when daily maximum temperatures are greater than 29 • C. As a consequence, NO x reductions are the most effective control option for reducing the frequency of future ozone violations in the southern SJV.

Abstract.A relaxed eddy accumulation (REA) system combined with a nitrous acid (HONO) analyzer was developed to measure atmospheric HONO vertical fluxes. The system consists of three major components: (1) a fast-response sonic anemometer measuring both vertical wind velocity and air temperature, (2) a fast-response controlling unit separating air motions into updraft and downdraft samplers by the sign of vertical wind velocity, and (3) a highly sensitive HONO analyzer based on aqueous long path absorption photometry that measures HONO concentrations in the updrafts and downdrafts. A dynamic velocity threshold (±0.5σ w , where σ w is a standard deviation of the vertical wind velocity) was used for valve switching determined by the running means and standard deviations of the vertical wind velocity. Using measured temperature as a tracer and the average values from two field deployments, the flux proportionality coefficient, β, was determined to be 0.42 ± 0.02, in good agreement with the theoretical estimation. The REA system was deployed in two ground-based field studies. In the California Research at the Nexus of Air Quality and Climate Change (CalNex) study in Bakersfield, California in summer 2010, measured HONO fluxes appeared to be upward during the day and were close to zero at night. The upward HONO flux was highly correlated to the product of NO 2 and solar radiation. During the Biosphere Effects on Aerosols and Photochemistry Ex-

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Tidal inlets, narrow, comparatively deep gaps between barrier islands, are channels through which tidal currents flow vigorously as the water enters and leaves the backbarrier lagoons, bays, and intertidal flats and marshes. Many geologists have compared tidal inlets to river channels and have speculated that if an inlet shifts laterally, it should deposit a distinctive sequence of sediments, analogous to the point‐bar sequence left by a meandering stream channel. Fire Island Inlet, located 56 km east of New York City, has migrated WSW at a mean rate of 64 m/year during the period 1825–1940. Waves approaching the coast, predominantly from the southeast, have shifted sediment along the shore toward the WSW. Deposition of sediment on the east side of the inlet has forced the tidal currents to erode the west side of the inlet, thus causing lateral migration. Because hydraulic conditions vary from the channel floor to the subaerial part of the spit which is present on the ENE side of the channel, sedimentary structures and textures vary systematically with depth. We have determined the various sedimentary environments associated with the modern Fire Island Inlet, sampled and described the sediments from these environments, and have collected samples from corings made on that part of Fire Island through which the inlet has migrated. On the basis of our studies, we propose an inlet sequence which is formed by the lateral migration of a tidal inlet. The sequence includes five major units, as follows on p. 492. The sediments belonging to various units in this sequence have been identified in four borings made on those parts of Fire Island through which the Fire Island Inlet has migrated since 1825. This sequence should be applicable to other inlets also. We think that the boundary between deep channel and shallow channel units remains relatively fixed at −4.5 m, whereas the thickness of the deep channel unit is determined by the depth range between −4.5 m and the total depth of the inlet. Hence, the main source of variation in the inlet sequence will be the thickness of the deep‐channel unit. Most of the sediments of the inlet sequence are incised below mean low water; hence they will almost certainly be preserved in the geologic record, even if all other associated sediments from barrier environments located above mean low water are not preserved. Because of the great variability possible in rates of lateral migration of inlets along the shore compared with the rates of barrier displacement perpendicular to the shore, inlet sediments may be preserved as elongate lenses, or as widespread blankets. The shape of inlet deposits reveals much about the behaviour of barriers during a submergence. Hence, inlet sediments should shed new light on sediments of the continental shelves and on basal transgressive sands in the geologic record.

Measurements of HONO (g) were validated to be free of known interferences for wet chemical instrumentation. The accumulation of nitrite into particulate matter was found to be enhanced when gaseous mixing ratios of HONO (g) were highest. Reactive uptake of HONO (g) on to lofted dust and the ground surface, forming a reservoir, is a potential mechanism to explain these observations. The AIM-IC HONO (g) measurements were parameterized in a chemical model to calculate the ground surface daytime HONO (g) source strength at 4.5 m above the surface, found to be on the order of 1.27 ppb h À1, to determine the relative importance of a surface reservoir. If all deposited nighttime HONO (g) is reemitted the following day, up to 30% of the daytime HONO (g) source at CalNex-SJV may be accounted for. The observations of HONO (g) and NO 2 À (p) in Bakersfield, during CalNex, suggest a surface sink and source of HONO (g) . Extension of currently accepted unknown daytime HONO (g) source reactions to include a potential surface HONO (g) reservoir should therefore be sound, but quantitation of the relative contributions of each surface source toward daytime HONO (g) production remains to be resolved.

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