nuclear analytical techniques in particle air pollution monitoring septiembre 14, 2011 grizel...

Nuclear Analytical Techniquesin

Particle Air Pollution Monitoring

Septiembre 14, 2011

Grizel Pérez, Ibrahin PiñeraCentro de Aplicaciones Tecnológicas

y Desarrollo NuclearCEADEN

Content

Introduction

Nuclear Analytical Techniques in PM monitoring

• Physical Principles

• Main characteristics

• PM sampling

Application example

Conclusions

G. PérezSept. 142011

IntroductionG. PérezSept. 142011

Air pollution has become a matter of global concern, particularly in some of the world's largest cities. It is made up of many different components that affect the environment - and directly or indirectly the health of people. The main components include sulphur dioxide, particulate matter, carbon monoxide, reactive hydrocarbon compounds, nitrogen oxides, ozone, and lead.

Nuclear techniques have important applications in the study of nearly all of them. However, it is in the study of airborne particulate matter (APM) that nuclear analytical techniques find many of their most important applications.

NATs in PM monitoringPM nuclear analysis methods

Airborne particulate matter retained on the filter may be examined or analyzed chemically by a variety of methods. In this presentation, only nuclear analytical techniques (NATs) are considered because of their advantages in analyzing many elements in air particulate matter non-destructively and simultaneously.The key three NATs for analysis of particulate matter in air are:


NATs in PM monitoring

Airborne particulate matter retained on the filter may be examined or analyzed chemically by a variety of methods. In this presentation, only nuclear analytical techniques (NATs) are considered because of their advantages in analyzing many elements in air particulate matter non-destructively and simultaneously.The key three NATs for analysis of particulate matter in air are:

PM nuclear analysis methods


Physical Principles of NATsNeutron Activation Analysis (NAA)

In typical NAA, a sample is exposed to a high flux of thermal neutrons in a nuclear reactor or accelerator. NAA is based on the interaction of a neutron (n) with a target nucleus (AZ) where the neutron is captured and gamma rays are emitted.


Physical Principles of NATs

The spectrum of gamma rays energy determines the specific isotopes present in the sample.

The intensity of the gamma rays is proportional to the amounts of elements present.

Typically 5 counting regimes are required to detect these elements (300 s, 1 hr, 10 hr, 4 days and 15 days).

It is highly sensitive (ppb), it does not quantify elements such as Si, Ni, Co, and Pb. Typical elemental detection limits range from 0.01 to 10 ng m-3.

NAA is a simultaneous, multi-element method that can be used to measure 40-45 elements.

Neutron Activation Analysis (NAA)

In typical NAA, a sample is exposed to a high flux of thermal neutrons in a nuclear reactor or accelerator. NAA is based on the interaction of a neutron (n) with a target nucleus (AZ) where the neutron is captured and gamma rays are emitted.


X-Ray Fluorescence (XRF)

XRF is based on the measurements of the energies and intensities of the characteristic X-rays excited in different materials by using an external source of electromagnetic radiation (usually X-ray tubes or radioisotope sources).

Physical Principles of NATsG. PérezSept. 142011

X-Ray Fluorescence (XRF)

XRF is based on the measurements of the energies and intensities of the characteristic X-rays excited in different materials by using an external source of electromagnetic radiation (usually X-ray tubes or radioisotope sources).

XRF can be used for all elements with Z from 11 (Na) to 92 (U). Typical elemental detection limits for this method range between 2 and

2000 ng m-3. XRF depends on the availability of excellent PM standards. Shorter analysis time than NAA. XRF can be used for simultaneous determination of 20-25 elements.


Ion Beam Analysis (IBA)

IBA is based on the interaction, at both the atomic and the nuclear level, between accelerated charged particles and the bombarded material.


Ion Beam Analysis (IBA)

IBA is based on the interaction, at both the atomic and the nuclear level, between accelerated charged particles and the bombarded material.

These techniques are used simultaneously as key analytical tools to assess PM pollution on a regular basis.

The choice of analytical method depends on the inorganic compounds of interest and the detection limits desired.

Using the four different analysis techniques (PIXE, PIGE, PESA, RBS), IBA can measure more than 40 elements (H – U).


Particle Induced X-ray Emission Analysis (PIXE)

PIXE is a powerful and relatively simple analytical technique that can be used to identify and quantify trace elements typically ranging from Na to U.

Sample irradiation is usually performed by means of 2-3 MeV protons produced by an accelerator.

Xray detection is usually done by energy dispersive semiconductor detectors such as Si(Li) or HP Ge detectors.

This multi-elemental analysis technique can measure more than 30 elements in short times due to higher cross-sections as compared to XRF.

With the addition of PIGE and PESA, allows for the detection of light elements that is useful for source identification and apportionment and estimation of organic carbon.

Typical detection limits range from 1 to 50 ng m-3.


Particle Induced X-ray Emission Analysis (PIXE)

The remaining three methods are used simultaneously to achieve additional information on elements that can not or hardly be measured with PIXE.


Advantages Disadvantages

• multielemental (H – U)

• non-destructive

• minimal sample preparation

• short irradiation time (less than 15 min)

• quick analysis for IBA (typically 15 min)

• high sensitivity

• good accuracy and precision

• can handle small samples (< 1 mg)

• IBA are cost effective for large sample numbers, more than 10

• NAA is slow, requires multiple counting regimes to detect many elements

• NAA requires access to research nuclear reactor

• IBA requires access to particle accelerator

• impurities may be a problem

• matrix offsets and background

• standard/sample must match closely (matrix)

• XRF has particle size effects for low Z elements

Main characteristics of NATsG. PérezSept. 142011

NATs in PM monitoring

Typical load: 50 – 700 mg/cm2

Composition: Soil, soot, salts, industrial released Particle size: ~ 0.1 to 50 mm Filter media:

o Teflon o Celluloseo Membrane (non-coated, coated)

Dichotomous sampler (used under IAEA coordinated research projects and TC projects)

(i) two fractions: 10 to 2.5 m and < 2.5 m (ii) 8 m and 0.4 m pore 47 mm Nuclepore Filters; Flow rate 16 lpm (iii) sampling time: 24 h for particle mass concentrations smaller than 50 g/m3;

Two days – 10-15 g/m3

APM: usually collected by air filtering

NAA is compatible with sampling by high-volume (TSP; PM10) and dichotomous samplers. Quartz filters used in high-volume samplers cause high background XRF and PIXE analysis,

filters used in the dichotomous samplers are preferable. PM2.5 collection by dichotomous samplers is typically involved by PIXE analysis.


Application exampleIAEA ARCAL Project RLA/7/ 011, ARCAL LXXX :ASSESSMENT OF ATMOSPHERIC POLLUTANTS

BY PARTICLES (2005-2008)

General Objectives:• To impel the research in the field of

monitoring air pollution with emphasis on particles.

• Sample collection of airborne particulate matter (including course and fine) simultaneously.

• The use of nuclear technology to characterize airborne particulate matter.

Argentina, Chile, Costa Rica, Cuba, Dominican Republic, Mexico, Uruguay, Venezuela.


CEADEN

Infanta Ave. & Manglar,Centro Habana, Havana City, Cuba.

Urban site with high traffic and densely populated

23.12 N 82.4 W

Environmental Monitoring Station

Sampling site at INHEMG. PérezSept. 142011

Possible pollution sites

sampling site


Samples and data collection

Sampling period:November 14, 2006 to April, 2007.Total 5 months.

Sampling frequency:Every second day with 24 h duration.

Air Sampler type GENT with stacked filter unit for collecting the aerosol in two size fraction (PM2,5 and PM10) simultaneously.


Samples preparation

Microbalance: Cahn C-35Resolution: 0.1 µg


Gravimetric analysis

0

5

10

15

20

25

30

35

40

45

50

55

60

AprilMarchFebruaryJ anuaryDecemberNovember

Concentr

ation (

mg/m

3)

coarse fraction fine fraction

8 16 24 32 40 48 56 64

3

6

9

12

15

18

21

24

27

30

PM

2.5 (g

/m3)

PM10

(g/m3)

Linear Regression (R = 0.676):PM

2.5 = (0.308 +/- 0.008) * PM

10

Higher and lower extrem values

Descriptive statistics of the data (µg/m3).


PIXE analysis

sample

Protons

2.5 MeV

x

I = 15 nAQ = 6 mC

Ortec Si(Li) detectoractive area = 80 mm2

resolution = 200 eV at 5.9 keV (Mn-Kα, 55Fe)

Tandetron Accelerator, PIXE Analysis Lab. ININ, Mexico.


100 200 300 400 500 600

1

10

100

1000

10000

36

ZnK Br

Pb

ZnK

CuNi

FeK

FeK

Mn

CrV

Ti

CaK

CaK

Cl

KS

cont

eos

canal

Espectro CUB03G07 PM10

14 elements were consistently detected in the samples

100 200 300 400 500 6001

10

100

1000

36

ZnK Br

Pb

ZnK

CuNi

FeK

FeK

Mn

CrV

Ti

CaK

CaK

ClKS

cont

eos Espectro CUB01F07

PM2.5

PIXE analysisG. PérezSept. 142011

Elemental analysis

Softwares for spectra processing AXIL & WINAXIL_4.5.3


Partícula FinaElemento

(MDL)

Partícula GruesaMedia Max Min n Media Max Min n

(ng/m3) (ng/m3) (ng/m3) (ng/m3) (ng/m3) (ng/m3) (ng/m3) (ng/m3)

658.83 1711.14 121.68 43.33 68 S (28.50) 429.03 1178.91 91.46 28.92 7165.77 315.37 11.78 4.05 63 Cl (11.60) 1835.54 4108.18 38.51 123.73 7142.98 209.80 5.82 2.89 68 K (4.40) 117.36 252.72 31.40 7.91 71

110.62 515.40 37.42 7.65 68 Ca (2.80) 2029.86 4763.29 312.31 136.83 715.02 26.32 2.08 0.20 32 Ti (2.03) 22.08 115.08 3.03 1.49 71

21.71 115.35 0.17 1.35 63 V (1.88) 13.55 56.99 1.91 0.85 663.05 12.15 1.47 0.18 55 Cr (1.38) 2.89 7.08 1.39 0.18 62

10.48 131.54 0.87 0.43 41 Mn (0.87) 10.54 146.74 1.08 0.70 7060.75 655.98 15.52 3.96 67 Fe (0.88) 235.49 852.97 27.39 15.65 70

4.72 21.65 0.99 0.26 55 Ni (0.95) 3.72 11.85 0.96 0.24 662.43 10.49 1.01 0.14 53 Cu (1.00) 3.78 11.64 1.02 0.25 70

18.99 293.11 1.20 1.26 68 Zn (1.20) 18.35 86.26 1.78 1.24 719.09 13.67 5.43 0.56 60 Br (5.30) 7.14 11.74 5.41 0.32 24

10.59 55.63 4.77 0.43 35 Pb (4.70) 10.45 39.79 4.82 0.53 48Todos los datos están referidos a los elementos que fueron encontrados por encima del LMD.

Elemental analysisG. PérezSept. 142011

0

1000

2000

3000

4000

5000

6000

7000 Cr Mn Fe Ni

K Ca Ti V

Cu Zn Br Pb

S Cl

AprilMarchFebruaryJanuaryDecemberNovember

PM

2.5

avera

ge

ele

me

nta

l co

nce

ntr

atio

n (

ng

/m3 )

0

2

4

6

8

10

12

14

16

18

20

22 PM2.5

Collection date

PM

2.5

co

nce

ntr

ation

(u

g/m

3 )

0

3000

6000

9000

12000

15000

18000 Cu Zn Br Pb

K Ca Ti V

Cr Mn Fe Ni

S Cl

AprilMarchFebruaryJanuaryDecemberNovember

PM

10

ave

rag

e e

lem

en

tal co

nce

ntr

atio

n (

ng

/m3 )

0

5

10

15

20

25

30

35

40

45 PM10

Collection date

PM

10

co

nce

ntr

atio

n (

ug

/m3 )

Elemental analysisG. PérezSept. 142011

Statistical analysis

• Descriptive statistic.• Correlation Matrix.• Principal Component Matrix.• Rotated Principal Component Matrix by the maximum variability criteria.

• Component profiles and identification of the main sources (Factors).

• Scores of the found Factors.• Contributions from sources to element concentrations.


Rotated Principal Component Matrix

fine mode


Source identification & apportionment

Pb

Br

Zn

Cu

Ni

Fe

Mn

Cr

V

Ti

Ca

K

Cl

S

0 20 40 60 80 100

Source contribution (%)

Source 1 Source 2 Source 3 Source 4 Source 5

fine mode


Sources apportionmentfine mode


coarse mode

Rotated Principal Component MatrixG. PérezSept. 142011

coarse mode

Pb

Br

Zn

Cu

Ni

Fe

Mn

Cr

V

Ti

Ca

K

Cl

S

0 20 40 60 80 100

Source contribution (%)

Source 1 Source 2 Source 3 Source 4

Source identification & apportionmentG. PérezSept. 142011

coarse mode

Sources apportionmentG. PérezSept. 142011

Conclusions

Nuclear Analytical Techniques can be used for determination of the elemental composition of coarse and fine particulate matter: neutron activation analysis, X-ray fluorescence, and ion beam analysis (PIXE, PIGE, PESA, RBS).

Since the various types of sources of particulate air pollutants are characterized by the elemental composition of the particles, knowledge of the elements in particles allows the identification of the origin of the particles and, thereby, leads to a quantitative apportionment of the existing types of sources.

In consequence, most important source types can be identified and decisions can be made on which source types it is most appropriate to reduce emissions.

This would constitute a valuable step forward in air quality management, particularly in cases where emissions inventories are not established.

In our case, the results provided by PIXE in combination with appropriated statistical analysis allow us to identify the source profiles and contribution, providing important information about atmospheric pollution in selected site, necessary to develop strategies and to establish appropriate policies on pollution control.


Nuclear Analytical Techniques can be used for determination of the elemental composition of coarse and fine particulate matter: neutron activation analysis, X-ray fluorescence, and ion beam analysis (PIXE, PIGE, PESA, RBS).

Since the various types of sources of particulate air pollutants are characterized by the elemental composition of the particles, knowledge of the elements in particles allows the identification of the origin of the particles and, thereby, leads to a quantitative apportionment of the existing types of sources.

In consequence, most important source types can be identified and decisions can be made on which source types it is most appropriate to reduce emissions.

This would constitute a valuable step forward in air quality management, particularly in cases where emissions inventories are not established.

In our case, the results provided by PIXE in combination with appropriated statistical analysis allow us to identify the source profiles and contribution, providing important information about atmospheric pollution in selected site, necessary to develop strategies and to establish appropriate policies on pollution control.

ConclusionsG. PérezSept. 142011

Thank you for your attention…

nuclear analytical techniques in particle air pollution monitoring septiembre 14, 2011 grizel...

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