Real-Time, Online Automated System for Measurement of Water

Jun 15, 2016 - We present a novel automated system for real-time measurements of ..... We also acknowledge support from a Georgia Power Scholar Chair ...
1 downloads 4 Views 1MB Size
Subscriber access provided by UNIV OF CAMBRIDGE

Article

A real-time, online automated system for measurement of water soluble reactive Phosphate (SRP) ions in atmospheric particles Kalliopi Violaki, Ting Fang, Nikolaos Mihalopoulos, Rodney J. Weber, and Athanasios Nenes Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.analchem.6b01264 • Publication Date (Web): 15 Jun 2016 Downloaded from http://pubs.acs.org on June 16, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Analytical Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 19

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Analytical Chemistry

1 2

A real-time, online automated system for measurement of water soluble

3

reactive Phosphate (SRP) ions in atmospheric particles

4

Kalliopi Violaki*1,2, Ting Fang2, Nikos Mihalopoulos1,5, Rodney. Weber2, Athanasios Nenes*2,3,4,5

5 6 7 8

1

Department of Chemistry, University of Crete, Greece

9

2

School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta;GA, 30332

10

3

School of Chemical and Biomolecular Engineering, Georgia Institute of Technology,

11

Atlanta;GA, 30332

12

4

13

Patras, Greece

14

5

15

Athens, Pendeli, Greece

Institute of Chemical Engineering Sciences, Foundation for Research and Technology, Hellas,

Institute for Environmental Research and Sustainable Development, National Observatory of

16 17 18

ABSTRACT: We present a novel automated system for real-time measurements of

19

water Soluble Reactive Phosphate (SRP) ions in atmospheric particles. Detection of SRP is

20

based on molybdenum blue chemistry with Sn(II) chloride dihydrate reduction. The

21

instrumentation consists of one particle-into-liquid sampler (PILS) coupled with a 250 cm

22

path length Liquid Waveguide Capillary Cell (LWCC) and miniature fiber optic

23

spectrometer, with detection wavelength set at 690 nm. The method detection limit was 0.4

24

nM P, equivalent to 0.03 nmol P m-3 in atmospheric particles. Comparison of SRP in

25

collocate PM2.5 aerosol filter sampling with the PILS-LWCC on line system were in good

26

agreement (n=49, slope=0.84, R2 =0.78). This novel technique offers at least an order of

27

magnitude enhancement in sensitivity over existing approaches allowing for SRP

28

measurements of unprecedented frequency (8 min), which will lead to greater understanding

29

of the sources and impacts of SRP in atmospheric chemistry.

30 31

Keywords: Phosphate, SRP, dust, Liquid Waveguide Capillary Cell, PILS, atmosphere,

32

biogeochemical P cycle. 1 ACS Paragon Plus Environment

Analytical Chemistry

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 19

33 34 35 36

INTRODUCTION

37

phosphorus (1,2). Of particular interest is the role of phosphorus in marine primary

38

productivity, owing to its potential for affecting the concentration of atmospheric carbon

39

dioxide (3) The atmosphere is considered as the principal source of externally-supplied

40

nutrients for large areas of the surface ocean, and oligotrophic open oceans in particular (4).

41

Therefore, atmospheric particles e.g. deposited desert dust could affect the trophic status of

42

P-limited marine ecosystems. Atmospheric transport model simulations combined with the

43

worldwide compilation of atmospheric Total Phosphorus (TP) and phosphate ions (PO43-)

44

estimated the globally averaged TP at 1.39 Tg P y-1 and 0.24 Tg P y-1, respectively. Globally,

45

terrigenous dust was found to be the dominant P source (82%), while biogenic particles

46

(12%) and combustion inputs (5%) are comparable in non dusty regions (5).

47

P in soil-derived dust is primarily in the form of apatite Ca5(PO4)3(F,Cl,OH), and to a lesser

48

extent, P bound to iron minerals (6,7).Both of these forms exhibit limited solubility in sea

49

water (8), yet P needs to solubilize to become bioavailable – in part because the insoluble

50

fraction sinks quickly out of the euphotic zone. Estimates of soluble (bioavailable) P in

51

atmospheric aerosol range widely, between 7 and 100% (5), with very little known on the

52

mechanisms responsible for this variability. In a recent study (9) presented compelling

53

evidence that acidification of desert dust particles from fossil fuel combustion (sulfur dioxide

54

and sulfate aerosol) or other natural sources (volcanoes and DMS oxidation), can

55

dramatically increase the fraction of bioavailable P in dust. Recent study show that

56

atmospheric particles are highly acidic and insensitive to changes in anthropogenic sulfur

57

emissions (10)Despite the observed decrease by 70%, over the past 15 years, of atmospheric

58

sulfate concentrations in the southeastern United States and in many other regions globally,

59

the estimated atmospheric particle pH was relatively stable (0–2) (10), suggesting that

60

atmospheric acidification may be an important process.

61

The most common analytical methods for offline determination of phosphate ion

62

concentration in atmospheric aerosol samples are ion chromatography (IC) and

63

spectrophotometry. The latter is based on the reaction of PO43- with molybdate complex in

64

acidic solution forming a 12-molybdophosphoric acid and its subsequent reduction by

Primary productivity of continental and marine ecosystems is often limited or co-limited by

2 ACS Paragon Plus Environment

Page 3 of 19

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Analytical Chemistry

65

ascorbic acid or stannous chloride to the phosphomolybdenum blue complex, which its

66

absorbance is measured by spectrophotometry (11). However, with this method the possible

67

hydrolysis

68

phosphomolybdate complexes due to the reaction in acidic conditions (pH