Effect of Ambient Temperature on PUF Passive Samplers and PAHs Distribution in Puerto Rico

doi:10.4236/cweee.2013.22B007

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Computational Water, Energy, and Environmental Engineering, 2013, 2, 41-45

doi:10.4236/cweee.2013.22B007 Published Online April 2013 (http://www.scirp.org/journal/cweee)

Effect of Ambient Temperat ure on PUF Passive Sam p lers

and PAHs Distribution in Puerto Rico

Nedim Vardar 1, Ziad Chemseddine1, Juan Santos2

1School of Engineering, Inter American University, Bayamon, PR, 00957

2Department of Natural Sci ence, Inter A merican Univer si ty, Bay am on, PR , 00 95 7

Email: [email protected]

Received 2013

ABSTRACT

Pas sive sa mplin g for the moni tor ing of orga nic p ollu tants ( PAHs, PCBs , PB DEs) in a mbie nt air ha s rec eived i ncrea sed

attention in the last two decades. Ho wever, the accuracy of the concentration of organics obtained with passive samplers

under var ying e n viro nme ntal co nditi ons i s a s ubj ect of co ntr over sy. I n thi s st ud y, ef fect o f a mbie nt t empe rat ure o n pa s-

sive samplers was evaluated by using three different sampler configurations. Additionally, passive samplers with poly-

urethane disks (PUF) were applied throughout the Island for the determination of the airborne concentration of poly-

cyclic aromatic hydrocarbons (PAHs). The passive samplers were deployed in seven municipalities for three-month

periods in two different sampling campaigns, representing hurricane and non-hurricane seasons. Here we present pre-

liminary results obtained from those sampling campaigns. The total concentrations of 15 PAHs varied from 3.1 to 19.6

and from 5.5 to 38.5 ng/m3 for hur ricane and no n-hurricane seasons, respectively. Hurricane and non-hurricane season

concentrations of PAH were significantly different for the samples taken in the northern municipalities of the Island.

However, there was no significant difference in PAH concentrations between the hurricane and non-hurricane seasons

for the southern sites. Increased rainfall and high-relat ive hu midit y durin g the hur rica ne se ason had an in fluence on the

concentrations of PAHs derived by the passive PUF sampler.

Keywords: Passive Sampler ; PAH; Puerto Rico; Hurricane; P UF; A mbie nt Temperature

1. Introduction

Passive samplers with polyurethane disks (PUF) have

been widely used for the last decade in the measurement

of semi volatile organics (SOCs), in part because they are

easy to handle, operate independently for several months,

and are inexpensive. Knowledge of the sampling rate of

the device is necessary for an accurate conversion of the

sampled mass to an ambient concentration. However,

environmental conditions around the sampler influence

the sampling rate and the performance with which the

PUF sampler can be used. The reliability of passive sam-

pling techniques under varying environmental conditions

is therefore a subject of controversy. Envir onme ntal co n-

ditions that may affect the PUF sampler are wind speed,

temperature (T), atmospheric pressure, sunlight/UV-light

and humidity. T affects the compound specific molecular

diffusion coefficients (D) of the pollutants by increasing

D with T.

Polycyclic aromatic hydrocarbons (PAHs) are a natu-

ral component of most fossil fuels, and formed during the

incomplete combustion of these fuels, or other organic

substances. Some PAHs are manufactured as individual

compounds for research purposes. The che mical struc ture

of PAHs is comprised of two or more fused aromatic

rings made entirely from carbon and hydrogen. PAHs are

ubiquitous environmental pollutants and are formed from

bot h nat ur a l and a nt hr op o ge ni c so ur ce s. Altho u gh na t ur al

sources such as forest fires and volcanic eruptions con-

tribute to PAH formation, most PAHs in ambient air are

the result of man-made processes. PAHs pose severe

risks to human health and the environment due to their

toxicity, persistence, ability to travel long distances on

air and water currents [1-3]. Human exposure to these

compounds may result in a variety of adverse health ef-

fects including damage to the central nervous and repro-

ducti ve s ystems, d evel op ment of l ung ca ncer a nd ge netic

alterations. There are hundreds of PAH compounds in the

environment, but only 16 of them are included in the

priority polluta nts list of the U.S. environme nt protection

agency (USEPA) [4].

A number of studies have been conducted on the fate

of PAHs in atmosphere during the past three decades

[1-3, 5-9]. In most of these studies, a high-volume sam-

pling technique using filter and adsorbent has been ap-

plied. However, the use of passive sampling methods to

moni- tor airborne contaminants has greatly increased

N. VARDAR ET AL.

over the past few years. Passive samplers can be dep-

loyed at loca- tions where it is difficult or impractical to

install and maintain Hi-Vol samplers. These devices are

simple and inexpensive and do not need field calibration,

electricity nor technica l personnel at t he sampli ng site. In

addition, they can be deployed in many locations con-

currently due to their low cost.

Puerto Rico is located in the Caribbean with mainly

north-easterl y trade winds. Due to its location, the Is land

enjoys a tropical climate and a lso experiences the Atlantic

hurricane season. In this study, effect of ambient tem-

perature on passive samplers and seasonal distribution of

PAHs were evaluated Characterization of the PAHs in

the ambient air has been studied for a long time in other

parts of the world. A vast number of publications are

available in the literature for both urban and rural areas

from developed and developing countries [1-3,5-7].

How-ever, only limited data on atmospheric PAHs had

been acquired for Puerto Rico, and to our knowledge,

this is the first study to compare PAH concentrations

spatially distr ibuted across the island.

2. Materials and Method

2.1. Sampling Locations

Puerto Rico is a tropical island located in the Caribbean

Sea with a population of around 4 million. It has 9100

km2 total area and is one of the most densely populated

islands in the world. PUF pa ssive air samplers consisting

of polyurethane foam disks of 14 cm diameter and 1.2

cm thickness housed in two stainless steel bowls were

dep lo yed i n Ba yamo n, C aye y, Caroli na, Gua ya ma, Manati,

San Sebastian, and Naguabo (Figure 1).

Two sampling campaigns were achieved in 2010 for

three-month periods except in Naguabo where sampling

took place for six motnhs. Sampling parameters for the

samples are summarized in Table 1. Sampling sites of

Cayey and Manati are considered as urban, medium den-

sity, and residential. Bayamon and Carolina is described

as urban, high-density residential/industrial area. Naguabo

site is characterized as low-density coastal/resident ial.

San Sebastian is located in west part of the Island and

Figure 1. Map of Puerto Rico showing sampling locations.

Table 1. Passive Sampling Campaign Parameters.

Sampling

Campaign Start

Date End

Date Temp .

(

C) Rain

(cm)

Non-Hurricane

Seas on March 2010 June 2010 27.7 17.9

Hurric ane S eason June 2010 October 2010 28 .6 21.8

considered as urban, medium density, and residential.

Last, Guaya ma sampling site is situated in a coasta l/rural

region.

The temperature in the south of the Island is usually a

few degrees higher than the north. Between winter and

summe r, t here is onl y a te mpe ra ture s wing o f aro und 3˚C

Rainfall tends to be evenly distributed throughout the

year, but doubles during the months from May to Octo-

ber, as falls fro m November to April, with a driest period

from January to April. The wind patterns across the is-

land are basically zonal, from east to west.

2.2. Analy tical Proc edu re s

Information for sample preparation, extraction and analysis

is given in detail elsewhere [8]. Briefly, each PUF was

Soxhlet extracted with a 20:80 dichloromethane (DCM):

petroleu m ether (PE) solution for 24 h. All samples were

spiked with PAHs surrogate standards prior to extraction.

Four deuterated PAHs were used as surrogate standard

and P yre ne -d10 for volumetric corrections. The recoveries

of the following surrogate standards were used to correct

the amounts of specific PAHs found in the samples:

Ace na p h t hen e -d10 for acenaphthene (ACE), acenaphthylene

(ACT) and fluorine (FLN), phenanthrene-d10 for phe-

nanthrene (PHE), anthracene (ANT), and fluoranthene

(FL), chrysene-d12 for pyrene (PY), benz(a) anthracene

(BaA) and chrysene (CHR), and perylene-d12 for benzo

(b) fluoranthe (B bF), benzo(k)fluoranthe (BkF), benzo (a)

pyrene (BaP), indeno (1,2cd) pyrene (IcdP), dibenz (a,h)

anthracene ( DahA), and benzo(ghi)perylene (BghiP). T he

average recoveries for surrogates in field samples were

79% ± 31% for acenaphthene-d10, 86% ± 13% for phe-

nanthrene-d10, 84% ± 28% for chrysene-d12, 80% ± 15%

for perylene-d12.

The analysis of the samples was performed using a

Varian 450-GC coupled to an ion trap mass spectrometer

Varian 240 MS. A Varian factor 4 capillary column (30

m, 0.25 mm, 0.25 µm) was used. The GC oven tempera-

ture was programmed from 60℃(held one minute) to

130℃ at 7℃ min-1, then raised to 200℃ at 5℃ min-1,

and finally increased from 260 ℃ to 320℃ at 6℃ min-1.

The injector temperature was maintained at 295℃. The

linearity in the response of the GC/MS system was eva-

luated with calibration standards, at five different levels

of concentration (0.012, 0.06, 0.3, 0.6 and 1.2 ng/mL).

The instrument was Auto tuned at the start of runs with

N. VARDAR ET AL.

perfluorotributylamine (PFTBA). Individual PAHs were

identified b ased o n the rete ntio n times of target io n p eaks.

Internal standard calibration procedure was used for

quantif ying the identified compounds.

Field blanks, which accompanied samples to the sam-

pling site, were used to determine any contamination

during sample handling and preparation. Newly cleaned

PUFs were used as laboratory blanks. There was no sta-

tistically recognizable difference between field and la-

boratory blanks.

3. Results and Discussions

Passive sampling devices have been widely used for

more than a decade for the measurement of semi volatile

organics (SOCs) in air. PUF passive air sampler consists

of two stainless steel bowls and all parts of the sampler

are made from the stainless steel. In this study, twenty

four hour temperature changes inside the passive sampler

were characterized using HOBO pendant temperature

sensor. In addition to stainless steel sampler, two more

samplers, one consists of plastic bowls and another with

cupper bowls, were used to characterize the effect ma-

terial on the diurnal temperature changes inside the sam-

plers. Figure 2 shows the diurnal temperature changes

inside a stainless steel sampler. Temperature variation

inside and outside the sampler is shown with blue and

green lines, respectively. Temperatures inside the samp-

ler were significantly higher than outside temperatures

during the midday due to intense solar radiation. During

the early mornings and late afternoon hours no signifi-

cant temperature differences were observed between in-

side and outside of the sampler.

Figure 2. Temperature variation inside (blue line) and out-

side (green line) of a stainless steel sampler.

In order to minimize midday temperature differences

between inside and outside of the sampler, choices of other

feasible materials were investigated. Cupper and plastic

sampling bowls were used in constructing the passive

sampler. Figure 3 compares the diurnal temperature

changes among different samplers. It was expected that

the lowest temperature would be observed inside the

plastic passive sampler due to the lower conductivity of

plastic. Ho wever, as it can be seen from the Figure 3, the

highest temperature inside the samplers belongs to the

one made of plastic bowls. A further study is needed to

expla in this findi ng. Out o f these three samplers, stainless

steel sampler gave the lowes t internal te mpe ratures.

A network of passive sampling spatially distributed

throughout Puerto Rico including both urban and rural

areas were conducted. The present study presents the fir st

ambient air data for PAHs in Puerto Rico. Due to its lo-

cation, Puerto Rico enjoys a tropical climate and also

experiences the Atlantic hurricane season. Hurricane

sea son e xt end s fr om J une 1st to November 30th. T herefo re ,

sampl es ta ken in the fir st a nd seco nd sa mpling c ampa ign

were classified as non-hurricane and hurricane samples,

respectively. Higher PAH concentrations were obtained

in all sampling site s for the non-hurricane samples except

Cayey site. The total concentrations of 15 PAHs varied

from 3.1 to 19.6 and from 5.5 to 38.5 ng/m3 for hurricane

and non-hur ricane s easons, r espectively (Figure 4).

Increased rainfall and high water vapor content during

the hurricane season makes wet depo sition very efficient,

leading to a decreased atmospheric lifetime of PAHs for

the Island. Carolina site had the highest PAH concentra-

tions for both hurricane and non-hurricane season. Sea-

sonal concentration differences of PAH were more sig-

nific ant for the sa mples ta ken i n the no rthern municip ali-

ties (Bayamon, Manati, Carolina) than the southern mu-

nici pali ties (Caye y and Gua yama) of t he Isl and. T he nort h

Figure 3. Diurnal temperature changes among different

samplers.

N. VARDAR ET AL.

Figure 4 . Total P AH c once ntr a tions f or e ac h sa mpli ng l oca-

tions .

Table 2. At mospheric PAH Co ncentratio ns Derived by Pas-

sive Samplers in Different Stu dies.

Location Ran g e of Total

PAHs (ng/m3) Reference

Vario us M un icipal it ies, PR

Non-Hu r ricane S eason

Hurr ic ane Season

5.5 - 38.5

3.1 - 19.6 This study

Toronto, Canad a

Summer

Winter

Spring

16.5 - 61 .4

10.1 - 18 .5

3.53 - 18.8

[1]

Harbin, China

Spring

Summer

Autumn

Winter

25 - 120

13 - 50

22 - 74

81 - 240

[3]

Taichung, Taiwan 387.70 [5]

Mexico City, Mexico 32 - 92 [6]

Athens, Philippines 28.44 [7]

coast of the Island gets twice as much rain as the south

coast. Thus, increased precipitation as well as high- rela-

tive humidity during might have an influence on the

concentrations of PAHs derived by the passive PUF

sampler.

Table 2 provides a comparison of the ambient PAH

concentrations measured by passive samplers in different

part of the world. The PAH concentrations in the Island

are almost similar to those reported by [4] for winter and

spring seasons, but compared to summer season the Isl-

and concentrations are lower.

The PAH levels reported for Taichung, Taiwan are an

order of magnitude higher than those measured in this

study [14,15]. In Mexico, and Harpin, China, PAH con-

centrations significa ntly higher than the one measured in

this study [16]. In a study conducted in Athens, Philip-

pines, PAH concentrations were approximately twice

higher t han those measured in this st udy [17].

4. Conclusions

This study has provided some baseline data on the atmos-

pheric PAH levels in Puerto Rico which could be useful

for establishing long-ter m atmo spheric monitoring pr ogram

in the Island. In this study, the spatial characteristics of

PAHs derived from PUF passive sampler were studied

for two different sampling campaigns at the seven dif-

ferent sampling sites of the Island. It was found that

hurricane and non-hurricane season concentrations of

PAH were significantly different for the samples ta ken in

the northern municipalities of the Island. Ho wever, there

was no significant difference in PAH concentrations

between the hurricane and non-hurricane seasons for the

southern sites. Increased precipitation and high-relative

humidity during the hurricane season might have an

influence on the concentrations of PAHs derived by the

passive PUF sampler.

Diurnal temperature variations inside the passive sam-

plers constructed from stainless steel, cupper and plastic

sampling bowls were investigated. Sampler made of

stainless steel gave the lowest internal temperature s.

5. Acknowledgements

The authors would like to tank to the NSF -MRI program

for funding the purchase of the GC/MS/MS and to Puerto

Rico Louis Stokes Alliance for Minority Participation

(PR-LSAMP) for supporting this study.

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