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

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

Tellus B: Chemical and Physical Meteorology
Volume 64 (2012): Issue 1
By:  and    
Open Access
|Jan 2012
Figures & tables

Figures & Tables

Fig. 1. 

Cruise tracks undertaken on board ORV Sagar Kanya: (a) Bay of Bengal (BoB; SK-223A: March–April 2006) and Arabian Sea (ARS: SK-223B: April–May 2006); (b) BoB (SK-254: January 2009); 7-d air mass back trajectories (AMBTs) are computed at an arrival height of 1000 m.

Table 1. Chemical composition (mean±1σ) of aerosols (PM10) from the Bay of Bengal (BoB) and the Arabian Sea (ARS)

BoB ARS Parameter January 2009a March–April 2006b April–May 2006b PInorga 1.3±0.5 1.1±0.3 0.3±0.1 Na+ 75±35 37±27 83±106 NH4+ 171±182 50±35 BDL K+ 17±7 6±3 3±2 Mg2 + 9±6 7±3 8±11 Ca2+ 6±3 17±9 21±14 Cl− 9±10 0.4±0.3 62±110 14±10 1.2±1.4 8±7 123±79 62±26 35±12 Al 41±35 34±20 32±17 Ca 8±4 18±9 22±15 Fe 8±8 11±6 8±5 Mg 13±5 12±6 20±11 OC 542±434 157±132 18±13 EC 159±119 33±13 7±3

[i] All concentrations are expressed in nmol m−3.

[ii] aThis study.

[iii] bKumar et al. (2008).

Table 2. Phosphorous concentration and diagnostic ratios in aerosols (PM10) from the Bay of Bengal (BoB) and the Arabian Sea (ARS)

BoB ARS Parameter January 2009 March–April 2006a April–May 2006a PInorg 1.3±0.5 1.1±0.3 0.3±0.1 PDustb 0.3±0.3 0.3±0.2 0.2±0.1 PAnthc 1.0±0.5 0.8±0.2 0.1±0.1 PDust/PInorg 0.2±0.2 0.2±0.1 0.7±0.3 PAnth/PInorgd 0.8±0.2 0.8±0.1 0.3±0.3 dPInorg/nss-Ca2+ 0.54±0.54 0.09±0.05 0.03±0.02 dnss-K+/nss-Ca2+ 5.0±3.9 0.4±0.1 0.07±0.08 dnss-/nss-Ca2+ 35.1±19.0 4.3±1.7 2.1±1.1 dnss-Ca2+/Ca2+ 0.66±0.26 0.95±0.04 0.89±0.12 dCa2+/Ca 0.76±0.16 0.92±0.05 0.95±0.14 0.55±0.34 0.40±0.20 – 0.60±0.33 0.67±0.20 0.59± 0.23 1.07±0.17 0.97±0.06 1.8±1.2

[i] PInorg, PDust and PAnth are in nmol m−3 (this study).

[ii] aKumar et al. (2008).

[iii] bPDust is estimated by multiplying the P/Al ratio in the Upper Continental Crust (~0.008; McLennan, 2001) and measured Al concentration in the ambient aerosols (i.e., Pdust=0.008×Almeas).

[iv] cAnthropogenic fraction of water-soluble inorganic phosphorous (PAnth=PInorg−PDust).

[v] dMolar ratio.

[vi] eEquivalent ratio.

Fig. 2. 

The scatter plots between (a) nss-Ca2+ and nss- and (b) aerosol Ca and nss-Ca2+ suggest a reactive uptake of acidic species (H2SO4) by the mineral dust during long-range atmospheric transport. The dominant contribution of nss- in the MABL of Bay of Bengal (BoB) is clearly evident from the steep slope of the linear regression line compared to that in the Arabian Sea (ARS). Data for BoB (March–April 2006) and ARS (April–May 2006) are adopted from Kumar et al. (2008).

Table 3. Statistical significance of linear regressions among nss-, nss-K+, nss-Ca2+ and Ca

January 2009 March–April 2006 April–May 2006 Scatter Plot (Y vs. X) Regression (Y=mX+b) nss- vs. nss-Ca2+m=22.5; b=24.1 m=2.3; b=22.4 m=0.70; b=15.2 R2=0.75; P<0.05 R2=0.64; P<0.05 R2=0.60; P<0.05 nss-K+ vs. nss-Ca2+m=2.24; b=5.90 m=0.26; b=1.28 m=0.014; b=1.07 R2=0.83; P<0.05 R2=0.76; P<0.05 R2=0.11; P>0.05 PInorg vs. nss-Ca2+m=0.07; b=1.00 m=0.03; b=0.59 m=0.0044; b=0.257 R2=0.20; P>0.05 R2=0.64; P<0.05 R2=0.38; P>0.05 nss-Ca2+ vs. Ca m=0.75; b= m=0.92; b=−0.92 m=1.04; b=0.21 R2=0.86; P<0.05 R2=0.97; P<0.05 R2=0.96; P<0.05

[i] m=Slope; b=intercept.

Fig. 3. 

Scatter plots: (a) data plotted with symbol () provide evidence for the acid processing of mineral dust and, hence, enhanced supply of water-soluble PInorg during long-range transport to the Bay of Bengal (BoB). Evidence for supply of PInorg from anthropogenic sources is shown with the dotted line plotted through symbol (), with steep slope and high PInorg/nss-Ca2+ ratio. For comparison, data from the Arabian Sea (ARS) (), with high abundance of dust, represent exceptionally lower PInorg/nss-Ca2+ ratios. The scatter plot shown in (b) also exhibits steep slope, with higher abundance of anthropogenic nss-K+ (relative to nss-Ca2+) during January 2009 compared to March–April 2006 (BoB) and April–May 2006 (ARS).

Fig. 4. 

Spatio-temporal variability in the concentration of anthropogenic water-soluble inorganic phosphorous (Panth) to PInorg over the Bay of Bengal and the Arabian Sea.

Table 4. PInorg fluxes (Tg yr−1) from the northern Indian Ocean, Atlantic and Pacific

References N Indian Ocean N Atlantic N Pacific This study 0.036 – – Duce et al. ( 1991)a 0.070 0.154 0.336 Prospero, ( 1996)a 0.014 0.154 0.067 Ginoux et al. ( 2001)a 0.097 0.123 0.064 Zender et al. ( 2003) 0.040 0.190 0.030 Luo et al. ( 2003)a 0.079 0.161 0.025 Tegen et al. ( 2004)a 0.043 0.181 0.039 Jickells et al. ( 2005)a 0.083 0.141 0.050 Mahowald et al. ( 2008) 0.014 0.028 0.022 Okin et al. (2011) 0.043 0.020 0.026

[i] aPInorg is estimated from the abundance of mineral dust and P concentration in UCC.

DOI: https://doi.org/10.3402/tellusb.v64i0.17174 | Journal eISSN: 1600-0889
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Language: English
Page range: 17174 - 17174
Submitted on: Jan 6, 2012
Accepted on: Jun 20, 2012
Published on: Jan 1, 2012
Published by: Stockholm University Press
In partnership with: Paradigm Publishing Services
Keywords:
aerosol phosphorus,
size-distribution,
chemical processing,
mineral dust,
anthropogenic sources,
Bay of Bengal,
Arabian Sea

© 2012 Bikkina Srinivas, M. M. Sarin, published by Stockholm University Press
This work is licensed under the Creative Commons Attribution 4.0 License.

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