Over the past decade it has become apparent that the atmosphere is a significant pathway for the transport of many natural and pollutant materials from the continents to the ocean. The atmospheric input of many of these species can have an impact (either positive or negative) on biological processes in the sea and on marine chemical cycling. For example, there is now evidence that the atmosphere may be an important transport path for such essential nutrients as iron and nitrogen in some regions. In this report we assess current data in this area, develop global scale estimates of the atmospheric fluxes of trace elements, mineral aerosol, nitrogen species, and synthetic organic compounds to the ocean; and compare the atmospheric input rates of these substances to their input via rivers. Trace elements considered were Pb, Cd, Zn, Cu, Ni, As, Hg, Sn, Al, Fe, Si, and P. Oxidized and reduced forms of nitrogen were considered, including nitrate and ammonium ions and the gaseous species NO, NO2, HNO3, and NH3. Synthetic organic compounds considered included polychlorinated biphenyls (PCBs), hexachlorocyclohexanes (HCHs), DDTs, chlordane, dieldrin, and hexachlorobenzenes (HCBs). Making this assessment was difficult because there are very few actual measurements of deposition rates of these substances to the ocean. However, there are considerably more data on the atmospheric concentrations of these species in aerosol and gaseous form. Mean concentration data for 10° × 10° ocean areas were determined from the available concentration data or from extrapolation of these data into other regions. These concentration distributions were then combined with appropriate exchange coefficients and precipitation fields to obtain the global wet and dry deposition fluxes. Careful consideration was given to atmospheric transport processes as well as to removal mechanisms and the physical and physicochemical properties of aerosols and gases. Only annual values were calculated. On a global scale atmospheric inputs are generally equal to or greater than riverine inputs, and for most species atmospheric input to the ocean is significantly greater in the northern hemisphere than in the southern hemisphere. For dissolved trace metals in seawater, global atmospheric input dominates riverine input for Pb, Cd, and Zn, and the two transport paths are roughly equal for Cu, Ni, As, and Fe. Fluxes and basin-wide deposition of trace metals are generally a factor of 5-10 higher in the North Atlantic and North Pacific regions than in the South Atlantic and South Pacific. Global input of oxidized and reduced nitrogen species are roughly equal to each other, although the major fraction of oxidized nitrogen enters the ocean in the northern hemisphere, primarily as a result of pollution sources. Reduced nitrogen species are much more uniformly distributed, suggesting that the ocean itself may be a significant source. The global atmospheric input of such synthetic organic species as HCH,PCBs, DDT, and HCB completely dominates their input via rivers.

The atmospheric input of trace species to the world ocean

Using a three-dimensional global model of the troposphere, we show that the heterogeneous reactions of NO 3 and N205 on aerosol particles have a substantial influence on the concentrations of NOx; 03, and OH. Due to these reactions, the modeled yearly average global NOx burden decreases by 50% (80% in winter and 20% in summer). The heterogeneous removal of NOx in the northern hemisphere (NH) is dominated by reactions on aerosols; in the tropics and southern hemisphere (SH), with substantial smaller aerosol concentrations, liquid water clouds can provide an additional sink for N205 and NO 3. During spring in the NH subtropics and at mid-latitudes, O3-concentrations are lowered by 25%. In winter and spring in the subtropics of the NH calculated OH concentrations decreased by up to 30%. Global tropospheric average 03 and OH burden (the latter weighted with the amount of methane reacting with OH) can drop by about 9% each. By including reactions on aerosols, we are better able to simulate observed nitrate wet deposition patterns in North America and Europe. 03 concentrations in springtime smog situations are shown to be affected by heterogeneous reactions, indicating the great importance of chemical interactions resulting from NOx and SO2 emissions. However, a preliminary analysis shows that under present conditions a change in aerosol concentrations due to limited SO2 emission control strategies (e.g., reductions by a factor of 2 in industrial areas) will have only a relatively minor influence on 03 concentrations. Much larger reductions in SO2 emissions may cause larger increases in surface 03 concentrations, up to a maximum of 15%, if they are not accompanied by a reductio!a in NOx or hydrocarbon emission.

Reaction of N2O5 on tropospheric aerosols: Impact on the global distributions of NO x , O3, and OH

I present an analysis of ozonesonde data, synthesizing what is known about the distribution of tropospheric ozone Major features of the distribution are highlighted, and recommendations are given for testing three-dimensional models of tropospheric chemistry and transport with these data The data are analyzed on pressure surfaces and relative to the height of the thermal tropopause A minimum of 20 soundings are required for 95% confidence intervals of the ozone monthly means to be less than ±30% near the extratropical tropopause Twenty soundings also ensures means reliable to better than ±15% for 800–500 hPa for the extratropics and for 800–100 hPa in the tropics Ozone variability is higher in the upper troposphere for subtropical locations than for tropical locations, and 35 soundings are required for 400–100 hPa for the means to be defined to better than ±15% For northern middle and high latitudes, the broad summer maximum in ozone in the middle troposphere extends all the way up to the tropopause Median concentrations at the tropopause are highest in June and July, typically 125–200 ppb, and are a factor of 2 smaller in winter Highest values of ozone are in spring 2 km above the tropopause The change in the phase of the annual cycle of ozone between the tropopause and the region immediately above it, and the steep concentration gradients across the tropopause, suggest that high vertical resolution (∼1 km) will be required in models to simulate this behavior Mean ozone values in the middle troposphere are approximately constant from 30° to 75° in the winter in both hemispheres, while there is a maximum from 35° to 50°N in summer In the northern subtropics, there is a summer minimum in middle tropospheric ozone over the Pacific and a summer maximum over the Atlantic which appear to be related to differences in circulation Mean ozone values over Samoa are similar to those measured 20–30 years ago over Panama Ozone is higher over the tropical South Atlantic (Natal) than over the western Pacific (Samoa) all year from about 800 hPa to the tropopause; ozone is most similar in May and June over the Atlantic and Pacific, the months with minimum burning in the tropics The ozone maximum at Samoa in the middle and upper troposphere in October is caused by long-range transport of ozone and its precursors from biomass burning, with the peak lagging that at Natal by about a month The secondary peak in ozone in January and December at South Atlantic sites reflects transport of biomass burning effluents from the Northern Hemisphere The sonde data were used in combination with surface and satellite data to derive a gridded climatology for tropospheric ozone

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/1998JD100096

An analysis of ozonesonde data for the troposphere : recommendations for testing 3-D models and development of a gridded climatology for tropospheric ozone

The impact of temperature on formation of O3 and odd nitrogen photochemistry is investigated using urban-, regional- and global-scale simulations. Urban and polluted rural environments are explored with a regional simulation derived from a specific episode in the midwestern United States. The simulations predict that O3 increases with temperature in both urban and polluted rural environments. The O3-temperature relation is driven largely by chemistry of peroxyacetylnitrate (PAN) which represents an increased sink for both NOx and odd hydrogen at low temperatures. Isoprene emissions, H2O, and solar radiation also contribute to the O3-temperature relation. Possible correlations between temperature and anthropogenic emissions or stagnant meteorology were not included. Observations at urban and rural sites in the United States suggests that O3 increases with temperature at a faster rate than the models predict. Calculations with a one-dimensional global model suggest that increased temperature in the polluted boundary layer does not lead to increased O3 in the free troposphere, because increased export of O3 is balanced by decreased export of odd nitrogen species.

Impact of temperature on oxidant photochemistry in urban, polluted rural and remote environments

High resolution in situ measurements of reactive nitrogen (NO(y)) and O3 were made in the upper troposphere and lower stratosphere at a variety of latitudes and seasons. In the lower stratosphere, NO(y) and O3 are very highly positively correlated at all times and spatial scales sampled. The ratio NO(y)/NO3 is much less variable than either species measured separately. The ratio has a much weaker gradient with altitude than the mixing ratios of O3 or NO(y). The ratio is smaller and decreases more rapidly with altitude in the tropics than at midlatitudes. In the upper troposphere NO(y) and O3 are only weakly correlated. Their ratio in the tropical upper troposphere is about 0.005-0.025 and the ratio in the midlatitude upper troposphere is about 0.004-0.010. The NO(y) in the upper troposhere is probably partly due to lightning.

Reactive nitrogen and its correlation with ozone in the lower stratosphere and upper troposphere

Results are reported from airborne measurements of NO, NO2, O3, and CO obtained in the free troposphere (FT) and boundary layer (BL) over the western U.S. and eastern Pacific during the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation 2 (CITE 2) in summer 1986. The aircraft instrumentation and the CITE 2 flight protocols are described, and the results are presented in extensive tables and graphs. Over the ocean the median mixing ratios for NO and NO2 were found to be 4.0 and 10.4 parts per trillion by volume (pptv), respectively, in the BL and 12.4 and 18.0 pptv in the FT; the corresponding values over land were 34.5 and 75.0 pptv in the BL and 13.0 and 36.0 pptv in the FT. in continental air masses. NO(x) is shown to be positively correlated with O3 and CO and negatively correlated with dewpoint over the ocean, whereas over land NO(x) was positively correlated with O3, CO, and dewpoint.

/pdf/aircraft-measurements-of-no-x-over-the-eastern-pacific-and-1376500m9u.pdf

D. D. Davis

Papers

Aircraft measurements of NO x over the eastern Pacific and continental United States and implications for ozone production

Ratios of Peroxyacetyl Nitrate to Active Nitrogen Observed During Aircraft Flights Over the Eastern Pacific Oceans and