TRENDS IN THE ELEMENTAL COMPOSITION OF PM2.5IN SANTIAGO, CHILE FROM 1998 TO 2006

Pablo A. Ruiz Rudolph*,†, Pedro Oyola†, Ernesto Gramsch‡, Francisco Moreno‡ and Petros Koutrakis* * Harvard School of Public Health, Department of Environmental Health, Boston, MA; † Centro Mario Molina Chile, Santiago, Chile

‡University of Santiago, Department of Physics, Santiago, Chile

AIR POLLUTION IN SANTIAGO

SAMPLING

STATISTICAL METHODS•PM2.5 and elements were regressed against meteorological and temporal variables using linear regression models

•Meteorological data were dichotomized or trichotomized as follows:

•Wind speed (ws), ws < 0.8 m/s, 0.8 ≥ ws < 1.6 m/s, ws ≥ 1.6 m

•Relative humidity, rh < 70% and rh ≥ 70%

•Temperature t < 20oC and t ≥ 20oC

•Years were counted from April of one year to March of the following year

•Model

•Where, α is the regression intercept and βyj, βmj, βwj, βwsj, βtmpj, and βrhj are the regression coefficients of the independent variables year (1 to 8), month (1 to 12), weekday (1 to 7), wind speed (1 to 3), temperature (1 to 2) and relative humidity (1 to 2)

•As exponential terms:

[PM] = I * fyearj * fmonthj * fweekdayj * fwsj * ftmpj * frhj

•Fij are the Concentration Impact Factor (CIF). CIFs are multiplicative rather than additive. I.e. a CIF of 2 for June means concentrations in January are twice the concentrations in December

•The CIF for the intercept, I = eα, corresponds to the average concentration at the reference level (e.g. Year 2006, December, Saturday, ws ≥ 1.6 m/s, rh ≥ 70% and tmp ≥ 20 oC)

Acknowledgement

This work was funded by CONAMA RMThe authors want to thank SESMA for sample collection

YEAR EFFECT

MONTH EFFECT

DAY OF WEEK EFFECT

TEMPERATURE EFFECT

HUMIDITY EFFECT

WIND SPEED EFFECT

•Chile does not have PM2.5 standards

•EPA National YEAR Standard is 15 μgr m-3

•EPA National DAILY standard is 35 μgr m-3

•Average concentration was 37.4 μgr m-3

•2.5 times EPA YEAR standard

•EPA daily standard exceeded 40% of the days

PM2.5 Averages•Santiago, Chile has a population of about 6 million people, concentrating 40% of the population of Chile.

•The city is located in a valley (520 above sea level), surrounded by the Andes range to the East and the Coastal range to the West

• Summers are hot and dry, while winters tend to be colder and more humid, with frequent thermal inversions.

•Major sources include large number of industries and a large vehicle and bus fleet (800,000)

•Recent air quality interventions include:

•Street cleaning and tree planting campaign in 1998

•Reduction of lead in gasoline and sulfur in diesel fuels in 2001

•The objective of this work is:

•To asses the effectiveness of these and other measures

•To assess the effect of meteorological and time factors on air pollution levels

•PM2.5 sampling was conducted at the Parque O’Higgins air quality monitoring station

•Twenty-four hour particle samples (midnight to midnight) were collected from April 1998 through March 2006

• Fine particle (PM2.5, aerodynamic diameter <2.5 μm) filter samples were collected on Teflon filters using dichotomous samplers

•Mass was determined by gravimetry and elements by X-ray fluorescence (Desert Research Institute, Reno, NV, USA)

•For each month, only 6 to 8 filters were selected, or about 1 sample every fourth day, for a total of 717 filters analyzed across the eight years of the study

•Only elements that had at least 80% of all reported values above LOD were included in the statistical analysis

• Additionally, meteorological variables were measured at the sampling site and the La Paz air quality monitoring station, located a few kilometers north/northwest.

rhjrhjtmpjtmpjwsjwsjwjwjmjmjyjyjaPM ******]ln[

]var*exp[ ijijfij

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

MP2.5 Na Al Si S K Ca

Element by year (1998/1999 - 2005/2006)

CIF

1998/1999

1999/2000

2000/2001

2001/2002

2002/2003

2003/2004

2004/2005

2005/2006

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

Cr Mn Fe Cu Zn Se

Element by year (1998/1999 - 2005/2006)

CIF

1998/1999

1999/2000

2000/2001

2001/2002

2002/2003

2003/2004

2004/2005

2005/2006

0

2

4

6

8

10

12

14

Cl Ni Br Pb

Elements by year (1998/1999 - 2005/2006)

CIF

1998/1999

1999/2000

2000/2001

2001/2002

2002/2003

2003/2004

2004/2005

2005/2006

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Sunday

Monday

Tuesday

Wednesday

Thurs

day

Fri

day

Satu

rday

Day of week

CIF

Mass

Na

Al

Si

S

Cl

K

Ca

Fe

Se

Br

Pb

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Su

nd

ay

Mo

nd

ay

Tu

esd

ay

We

dn

esd

ay

Th

urs

da

y

Fri

da

y

Sa

turd

ay

Day of week

CIF

Cr

Mn

Ni

Cu

ZnSUMMARY

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Janu

ary

Feb

ruar

y

Mar

ch

Apr

il

May

June

July

Aug

ust

Sep

tem

ber

Oct

ober

Nov

embe

r

Dec

embe

r

Month

CIF

Mass

Cl

Cr

Mn

Ni

Cu

Zn

Br

Pb

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Janu

ary

Feb

ruar

y

Mar

ch

Apr

il

May

June

July

Aug

ust

Sep

tem

ber

Oct

ober

Nov

embe

r

Dec

embe

r

Month

CIF

Na

Al

Si

S

K

Ca

Fe

Se

0.0

0.5

1.0

1.5

Mass Na Al Si S Cl K Ca

Element

CIF

To<20 C To>= 20 C

0.0

0.5

1.0

1.5

Cr Mn Fe Ni Cu Zn Se Br Pb

Element

CIF

0.00.51.01.52.02.53.0

Cr Mn Fe Ni Cu Zn Se Br Pb

Element

Ye

arl

y C

IF

About the authorPablo Ruiz is a Research Fellow at HSPH

and a Research Associate at Centro Mario Molina ChileContact at email pruiz@hsph.harvard.edu

0.00.51.01.52.02.53.0

Mass Na Al Si S Cl K Ca

Element

Yea

rly

CIF ws<0.8 ws>= 0.8 and ws<1.6 ws>=1.6

0.0

0.5

1.0

1.5

Mass Na Al Si S Cl K Ca

Element

CIF

RH<70 % RH>= 70%

0.0

0.5

1.0

1.5

Cr Mn Fe Ni Cu Zn Se Br Pb

Element

CIF

      Effect    

Elements Weekday Month WS To RH

MP2.5, Pb, Br, Cl N Y Y Y N

S, Se, Na N N N N Y

Al, Si, K, Ca,Fe N N Y Y Y

Cr,Mn, Zn Y Y Y Y Y

Ni, Cu Y Y Y N N