Atmospheric pathways of phosphorous to the Bay of Bengal: contribution from anthropogenic sources and mineral dust

Abstract

The continental outflow from the Indo-Gangetic Plain and Southeast Asia, during the late NE monsoon (January–March), dominates the transport of chemical constituents to the marine atmospheric boundary layer (MABL) of the Bay of Bengal (BoB). During the rest of the year, prevailing wind regimes and meteorological conditions do not favour the atmospheric transport of continental products. Here we report on the spatio-temporal variability of inorganic phosphorous (PInorg=PO3−4) in the MABL and its dry-deposition flux to the surface BoB. On the basis of the abundance of PInorg in PM2.5 (0.1–0.8 nmol m−3) and PM10 (0.3–2.8 nmol m−3), we document its dominant occurrence in the coarse mode (Da≥2.5 µm). The analytical data also provide evidence for the chemical processing of mineral dust by acidic species and mobilisation of PInorg during the long-range atmospheric transport. However, significantly high PInorg/non-sea-salt Ca2+ ratios over the BoB suggest dominant contribution from anthropogenic sources (fertilisers and biomass burning emissions). PInorg concentration over the Arabian Sea is about 4 to 5 times lower and is primarily associated with the mineral dust from desert regions. The dry-deposition flux of PInorg to the BoB varies by one order of magnitude (0.5–5.0 µmol P m−2 d−1; Av: 0.02 Tg P yr−1). These results have implications to the air-sea deposition of phosphorous over oceanic regions downwind of the pollution sources and impact on the biogeochemistry of surface waters

Atmospheric P deposition to the subtropical North Atlantic: sources, properties, and relationship to N deposition

“…Although some rain samples had basic pH values up to 8.8, indicating some neutralization of acids, possibly from dust-based CaCO 3 [Nenes et al, 2011], no relationship was observed between pH and SRP or dust. These findings are in contrast to several studies that found good correlations (in aerosols) between SRP and nss-SO 4 2À and -Ca 2+ in east China [Chen and Chen, 2008] and between SRP and nss-Ca 2+ in the Bay of Bengal [Srinivas and Sarin, 2012]. A lack of strong correlations with different source indicators in rain indicates that there was no predominant source of SRP in Miami or that rain P sources are relatively complex compared with those in eastern China, where anthropogenic aerosol concentrations are in general very high and intense pollution events very frequent.…”

“…The higher SRP concentrations observed by Herut et al [1999] may be caused by the different dust sources that impact the Mediterranean, but admixing of pollution from Europe is also likely to be a major factor either by the addition of pollutant P or by the enhanced solubility of P through the effects of acid pollution species [Nenes et al, 2011;Srinivas and Sarin, 2012].…”

Understanding the nature of atmospheric acid processing of mineral dusts in supplying bioavailable phosphorus to the oceans

“…They suggest that this increased LIP is from polluted air masses from southern Europe bringing acid gases from the north to mix with the Saharan air mass. The increased fraction of LIP in atmospheric aerosols over the Bay of Bengal compared with atmospheric aerosols over the Arabian Sea has also been interpreted as due to the effect of acid processing of aerosols caused by anthropogenic activities (41). The action of the processes identified here may explain why aerosol samples across the North Central Atlantic can have greater fractions of soluble P than dust soil precursors or aerosols collected closer to the dust source (42).…”

Trends and Future Projections for Marine Biogeochemistry Research in Indonesia (Tren dan Proyeksi Penelitian Biogeokimia Laut di Indonesia)

“…The first mentioned is about atmospheric pathways of phosphorous that dominantly contributed by anthropogenic sources such as fertilisers and biomass burning emissions (Srinivas and Sarin, 2012). Then, the second is about deposition of N. Fe and P which implicate to the C-and N-fixation (Srinivas and Sarin, 2013).…”