We analyzed >400 particulate samples collected from throughout the Chesapeake Bay region between 1991 and 1998 for polycyclic aromatic hydrocarbons (PAHs). Isomer ratios of PAHs associated with aerosol and surface water particles demonstrate that motor vehicles are a major source of carcinogenic combustion-derived PAHs to Chesapeake Bay. Most of the benz[a]anthracene, benzo[a]pyrene, benzo[b]fluoranthene and their isomers in air, rain, and surface waters of Chesapeake Bay appear to be derived from automotive sources. Lesser, but still significant amounts (53(±5)%) of these PAHs in the sea surface microlayer near urban areas are motor vehicle-derived, with 47(±5)% being coal-derived. In contrast, PAHs in surface sediments of Chesapeake Bay are predominantly coal-derived (86(±8)%) and at most 14(±8)% motor vehicle-derived. Thus, carcinogenic PAHs input to the bay from motor vehicles are either degraded prior to deposition to the sediments or are diluted by previously deposited coal-derived PAHs in the seabed. Like anthropogenic nitrogen (NO x ), which leads to coastal eutrophication, managing the impact of carcinogenic PAHs on coastal regions will need to focus on motor vehicle use, which continues to outpace population growth in areas such as Chesapeake Bay.

Aragonite saturation state (Ω arag ) in surface and subsurface waters of the global oceans was calculated from up-to-date (through the year of 2012) ocean station dissolved inorganic carbon (DIC) and total alkalinity (TA) data. Surface Ω arag in the open ocean was always supersaturated (Ω > 1), ranging between 1.1 and 4.2. It was above 2.0 (2.0-4.2) between 40°N and 40°S but decreased toward higher latitude to below 1.5 in polar areas. The influences of water temperature on the TA/DIC ratio, combined with the temperature effects on inorganic carbon equilibrium and apparent solubility product (K′ sp ), explain the latitudinal differences in surface Ω arag . Vertically, Ω arag was highest in the surface mixed layer. Higher hydrostatic pressure, lower water temperature, and more CO 2 buildup from biological activity in the absence of air-sea gas exchange helped maintain lower Ω arag in the deep ocean. Below the thermocline, aerobic decomposition of organic matter along the pathway of global thermohaline circulation played an important role in controlling Ω arag distributions. Seasonally, surface Ω arag above 30°latitudes was about 0.06 to 0.55 higher during warmer months than during colder months in the open-ocean waters of both hemispheres. Decadal changes of Ω arag in the Atlantic and Pacific Oceans showed that Ω arag in waters shallower than 100 m depth decreased by 0.10 ± 0.09 (À0.40 ± 0.37% yr À1 ) on average from the decade spanning 1989-1998 to the decade spanning 1998-2010.

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