Nitrogen and sulphur over the Western Atlantic Ocean

Abstract

AlIItnlct-This paper reports new surface and aircraft measurements of sulphur and nitrogen species made during WATOX-85 at Lewes, Delaware and Bermuda. Concentrations of most species measured in this portion of the western Atlantic Ocean atmosphere were higher than those found in remote marine environments, showing clearly the influence of anthropogenic emissions from North America. The experiment was designed such that measurements were made following cold frontal passages in conditions of strong, dry westerly flow, to ensure that measurements at Bermuda were in air masses that had earlier crossed the east coast in the region of Lewes. Boundary-layer 80 2 concentrations decreased by a factor of20 between the cast coast and Bermuda, while sulphate was the same at both locations. First-order decay distances for 80 2 and total S were 340 and 620 km, respectively, under these conditions. The decay distance for total S is substantially shorter than previously determined, indicating that 50 2 in particular is removed in ncar-coastal environments more quickly than previously supposed. Boundary·layer NO x and HNO) concentrations decreased by close to an order of magnitude between the east coast and Bermuda, whereas for NO) the decrease was a factor of two. Corresponding first·order decay distances of NO~and total N were 500 and 550km, respectively.

Atmospheric decay distances and times for sulphur and nitrogen oxides estimated from air and precipitation monitoring in eastern Canada

“…In contrast, the results here give slightly larger decay distances than those recently obtained from the western Atlantic Ocean experiment (WATOX) where Hastie et al (1988), using a similar Lagrangian approach, found first-order decay distances of 340 and 620 km respectively for SO, and T-S, as pollutants moved off the east coast of North America towards Bermuda. Using a mean wind speed of 8 ms-' the residence times where estimated to be 12 h and 22 h respectively, very close to those shown here in Table 2.…”

“…For nitrogen, Hastie et al (1988) obtained more of the separate species than routinely measured in eastern Canada and obtained decay distances (times) for NO, and total N of 500 km (17.5 h) and 550 km (19 h) respectively. The value for T-NO; (comprising a large fraction of the T-N) shown in Table 2 is not inconsistent with these values.…”

Atmospheric Research Over the Western North Atlantic Ocean Region and North American East Coast: A Review of Past Work and Challenges Ahead

“…WATOX had multiple intensive periods with airborne measurements conducted to further characterize the sources and vertical structure of gases and aerosols over the WNAO, including WATOX‐85 (February–May 1985) (e.g., Galloway et al, ) and WATOX‐86 (January–June 1986) (e.g., Galloway & Whelpdale, ). A selected result from these airborne efforts was that SO 2 concentrations decreased in the boundary layer by a factor of 20 from the East Coast to Bermuda, while SO 4 2‐ levels remained the same (Hastie et al, ). Additionally, boundary layer NO x and nitric acid (HNO 3 ) levels decreased by an order of magnitude out toward Bermuda, while nitrate (NO 3 ‐ ) dropped by a factor of 2.…”

Tropospheric chemistry over the lower Great Plains of the United States 2. Trace gas profiles and distributions

“…(The reader is referred to Nunnermacker [1990], FehsenfeM et al [1987], and references therein for further details.) NO,`* data are included here for comparison with earlier measurements made with FeSO 4 [Dickerson, 1984[Dickerson, , 1985Kondo et al, 1987;Misanchuk et al, 1987;Luke and Dickerson, 1987;Hastie et al, 1988]. The efficiency of NO 2 conversion on the FeSO 4 catalyst was determined by gas phase titration [Sted•nan, 1976] to be 99% before and 98 % after the field project.…”