Subscriber access provided by TRENT UNIV
Article
Indoor/Outdoor Relationships and Anthropogenic Elemental Signatures in Airborne PM2.5 at a High School: Impacts of Petroleum Refining Emissions on Lanthanoid Enrichment Ayse Bozlaker, Jordan Peccia, and Shankararaman Chellam Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b06252 • Publication Date (Web): 04 Apr 2017 Downloaded from http://pubs.acs.org on April 7, 2017
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.
Environmental Science & Technology 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 21
Environmental Science & Technology
1
Indoor/Outdoor Relationships and Anthropogenic Elemental Signatures in Airborne PM2.5 at a High School:
2
Impacts of Petroleum Refining Emissions on Lanthanoid Enrichment
3
Ayse Bozlaker1, Jordan Peccia2, and Shankararaman Chellam1, 3, *
4
1
Department of Civil Engineering, Texas A&M University, College Station, TX 77843-3136
5
2
Department of Chemical and Environmental Engineering, Yale University, New Haven, CT 06520
6
3
Department of Chemical Engineering, Texas A&M University, College Station, TX 77843-3122
7
*
8
Department of Civil Engineering, Texas A&M University, College Station, TX 77843-3136. Phone: (979) 458 5914;
9
email:
[email protected] J. Walter “Deak” Porter ‘22 & James W. “Bud” Porter ’51 Professor and corresponding author, Zachry
10
ABSTRACT: Outdoor emissions of primary fine particles and their contributions to indoor air quality
11
deterioration were examined by collecting PM2.5 inside and outside a mechanically ventilated high school in the
12
ultra-industrialized ship channel region of Houston, TX over a 2-month period. By characterizing 47 elements
13
including lanthanoids (rare earth elements), using inductively coupled plasma-mass spectrometry, we captured
14
indoor signatures of outdoor episodic emissions arising from non-routine operations of petroleum refinery
15
fluidized-bed catalytic cracking units. Average indoor-to-outdoor (I/O) abundance ratios for the majority of
16
elements were close to unity providing evidence that indoor metal-bearing PM2.5 had predominantly outdoor
17
origins. Only Co had an I/O abundance ratio > 1 but its indoor sources could not be explicitly identified. La and
18
17 other elements (Na, K, V, Ni, Co, Cu, Zn, Ga, As, Se, Mo, Cd, Sn, Sb, Ba, W, and Pb), including air toxics were
19
enriched relative to the local soil both in indoor and outdoor PM2.5 demonstrating their anthropogenic origins.
20
Several lines of evidence including receptor modeling, lanthanoid ratios, and La-Ce-Sm ternary diagrams pointed
21
to petroleum refineries as being largely responsible for enhanced La and total lanthanoid concentrations in the
22
majority of paired indoor and outdoor PM2.5.
23
ACS Paragon Page Plus1Environment
Environmental Science & Technology
Page 2 of 21
TOC/Abstract Art
24 25 26
outdoor PM from petroleum refining causing indoor La enrichment
crustal and road dust PM
outdoor PM from motor vehicles
school indoor air quality
ACS Paragon Page Plus2Environment
outdoor PM from biomass burning
Page 3 of 21
Environmental Science & Technology
27
INTRODUCTION
28
Airborne fine particulate matter (PM2.5) is an important concern in schools since children can potentially
29
develop respiratory diseases following exposure in the indoor environment.1-3 Metal-enrichment in PM2.5 can
30
further increase the risk of adverse cardiovascular, brain, and respiratory health effects.4-6 This is of particular
31
importance for schools located in industrialized regions since anthropogenic metal emissions to the ambient
32
outdoor atmosphere can transport indoors and negatively impact children’s health.7-9
33
One interesting urban test-bed to evaluate transport of metal-enriched outdoor aerosols into schools is
34
Houston, Texas, which is the 5th largest metropolitan region of the United States with a population of over 6
35
million. This area is home to a ship channel that serves United States’ largest petrochemical complex, the second
36
busiest port by cargo volume, and myriad other concatenating industries. Epidemiological research and risk
37
analysis has implicated Houstonians’ increased cardiopulmonary risk and mortality to exposure to PM2.5 and some
38
of its elemental components including Cu, As, Ni, and V10-12 that have been traced to anthropogenic sources near
39
the ship channel.13-16 The city of Galena Park is located in the proximity of the ship channel and is predominantly
40
populated by Hispanics (81.4%) with lesser numbers of African Americans and Native Americans (7.6%) according
41
to the 2010 census. The 2010 median per capita income of its residents was only $13,650 with 20.4% of them
42
living below the poverty line.17 High concentrations of outdoor PM2.5 and metals have been reported historically in
43
this region13-16 suggesting a disproportionate exposure of particulate contaminants to the low-income minority
44
population raising environmental justice concerns. Although concentrations, sources, and composition of ambient
45
outdoor aerosols near the Houston Ship Channel have been investigated,13-15, 18-21 no measurements of indoor
46
aerosols in this region have been reported.
47
To date, very few measurements of the trace elemental composition of indoor and outdoor PM2.5 have been
48
performed for United States’ schools,22-26 although more data are available for homes and residential buildings.27-
49
29
50
indoor enrichment of several elements including hazardous air pollutants such as Sb and Pb.25 In contrast, a
51
unique aspect of Houston area aerosols is their lanthanoid (i.e. rare earths) enrichment emanating from fluid
52
catalytic cracking (FCC) units.13, 14, 18, 20 Airborne rare earth elements are readily absorbed by humans30, 31 leading
These studies have largely focused on representative and transition elements, with one study showing the
ACS Paragon Plus Environment Page 3
Environmental Science & Technology
Page 4 of 21
53
to a variety of toxicological symptoms.32 Additionally, children exposed to refinery emissions exhibit increased
54
wheezing, bronchial inflammation, reduced lung function and other symptoms33, 34 necessitating this research.
55
The principal objective of this manuscript is to evaluate the extent of infiltration and/or ventilation of outdoor
56
PM2.5 into a school located in a highly industrialized region. We are particularly interested to determine whether
57
petroleum refining emission events14, 18, 35 that release substantial amounts of aerosols enriched in rare earths and
58
other metals14, 18, 20 influence indoor PM2.5 concentrations. To accomplish this, paired indoor and outdoor PM2.5
59
was collected from a high school in the Houston Ship Channel region over a two-month span and comprehensively
60
analyzed for lanthanoids, transition metals and representative elements. To our knowledge, this is the first work
61
to comprehensively measure the concentrations of all 14 lanthanoids in PM2.5 inside a United States school and
62
relate it to outdoor anthropogenic contamination. Impacts of outdoor emissions on indoor PM2.5 composition
63
were qualitatively investigated using indoor/outdoor (I/O) ratios, elemental abundance patterns, enrichment
64
factors, tracer element ratios, and ternary diagrams. Contributions of primary outdoor sources to indoor and
65
outdoor PM2.5 mass were quantified by chemical mass balance (CMB) modeling,36, 37 which further allowed us to
66
isolate sources that enriched lanthanum and total lanthanoids in indoor and outdoor PM2.5.
67
MATERIALS AND METHODS
68
Sampling. Samples were collected at a high school (latitude: 29.7875, longitude: -95.1828) in Galena Park, TX
69
that is attended by approximately 4,500 students and surrounded by Interstate and State Highways (Supporting
70
Information, SI-Figure S1 and SI-Figure S2). The windows of the two-storied, 55-year old brick building were
71
always kept closed because of local weather conditions and its close proximity to the densely industrialized ship
72
channel region (including FCC refineries, ships, and barges) and heavily trafficked roads. During the sampling
73
period, winds were predominantly blowing from the South with an average speed of 6.8±3.0 miles per hour (SI-
74
Figure S3). The HVAC system was operated continuously and consisted of chilled water system with two 600-ton
75
York Chillers (Model AP-215), air handling units, rooftop units and variable air volume units in each room and
76
hallways operated with 85% return air (15% fresh air). The minimum efficiency reporting value (MERV) rating of
77
air filters was 9, which is expected to remove only 30-35% of PM2.5 mass.38 Hence, potential routes of entrance of
78
outdoor PM2.5 includes infiltration through the building envelope and through active outdoor air ventilation ACS Paragon Plus Environment Page 4
Page 5 of 21
Environmental Science & Technology
79
coupled with passage through filters. The air exchange rate was not explicitly measured, since it would only
80
provide limited insight into the I/O ratio due to the other complex processes (filtration, deposition, and
81
resuspension) that also must be characterized to understand the building-based contributions to the I/O ratio.39
82
Indoor and outdoor PM2.5 were collected using Partisol-Plus 2025 sequential air samplers (Rupprecht &
83
Patashnick) operated at a flow rate of 1m3/h. The indoor sampler was located on a 1m high countertop in an
84
unoccupied stockroom adjacent to a teacher’s office on the second floor, which had two air conditioning vents.
85
Since its doors were typically kept shut, our measurements possibly represent a lower bound on the students’ PM
86
exposure. Outdoor PM2.5 was collected from the second floor roof on the West side of the building overlooking
87
the baseball field from a height of ~8m aboveground (SI-Figure S2). Thirteen paired indoor and outdoor PM2.5
88
samples (26 total) were collected on Whatman 46.2mm diameter PTFE membrane filters over 2-6 consecutive
89
days between March 11 and May 11, 2011 (SI-Table S1).
90
Sample Preparation and Analysis. Blank filters and indoor and outdoor PM2.5 samples were acid-digested
91
(HNO3, HF, H3BO3) in two-stages using Teflon vessels and a microwave oven (HP-500, MARS 5, CEM Corp.).20, 40
92
Sixteen representative elements (Na, Mg, Al, Si, K, Ca, Ga, As, Se, Rb, Sr, Sn, Sb, Cs, Ba, Pb), 15 transition metals
93
(Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Mo, Cd, Hf, W), 14 lanthanoids (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er,
94
Tm, Yb, Lu) and 2 actinides (Th, U) were analyzed by a quadrupole inductively coupled plasma-mass spectrometer
95
equipped with a reaction cell (DRC-q-ICP-MS; ELAN DRC II, PerkinElmer SCIEX). Ammonia was used as the cell gas
96
to reduce mass interferences for Al, Ca, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, As, Se, and Cd. Multi-element calibration
97
standards (n=6) and mixed internal standard of 115In and 209Bi (20µg/L) were freshly prepared by dilution of single-
98
element stock solutions (10µg/mL, High-Purity Standards) with 0.4M HNO3. The high accuracy and precision of our
99
microwave digestion and ICP-MS protocols were demonstrated by (i) quantitatively recovering all certified and
100
uncertified elements (86-119%) from Standard Reference Materials (SRMs) SRM1648a (urban PM) and SRM1633b
101
(coal fly ash) as shown in SI-Figure S4, (ii) analyzing four laboratory and field blanks, (iii) completely recovering
102
pre-digestion Ru spikes (102-109%), and (iv) accurately analyzing the mid-point calibration standard during sample
103
measurements (91-119%). More quality control/assurance details are provided in the Supporting Information
104
section and SI-Table S2. ACS Paragon Plus Environment Page 5
Environmental Science & Technology
Page 6 of 21
RESULTS AND DISCUSSION
106
Indoor and Outdoor PM2.5 Mass Concentrations. Figure 1 depicts a time series of indoor and outdoor PM2.5
107
mass concentrations (see also SI-Table S1). As observed, indoor and outdoor levels were consistently in-phase,
108
exhibiting collocated peaks and valleys, and consequently significantly positively correlated (R2 = 0.73, p < 0.01)
109
expected of rooms with no indoor sources of particles. Indoor mass concentrations varied from 2.3 to 4.1µg/m3,
110
which is in the lower range of reported values in United States schools (2.4-37.0µg/m3).22, 26, 41, 42 Importantly,
111
indoor levels (3.0±0.52µg/m3) were 3.8-5.5 times lower than corresponding outdoor values (13.4±1.4µg/m3)
112
leading to very low average I/O mass concentration ratio of 0.22±0.02. The low I/O ratio and reduced coefficient
113
of variation (only 11%) suggests limited penetration of outdoor PM2.5 though the building envelope, the
114
perpetually closed windows, and filters employed in the mechanical ventilation system.43 The strong correlation
115
between indoor and outdoor PM2.5 mass values as well as indoor PM2.5 mass and corresponding I/O ratios (R2 =
116
0.68, p < 0.01) suggest dominance of outdoor sources for indoor PM2.5.44 18
-3
Mass concentration (µg m )
105
16 Outdoor PM2.5
14 12 10 4
Indoor PM2.5
May 8
May 2
Apr 27
Apr 21
Apr 15
Apr 9
Apr 3
Mar 28
Mar 22
Mar 20
Mar 18
Mar 14
117 118
Mar 12
2
3
Figure 1. Time series of indoor and outdoor mass concentrations. Note the break in the y-axis between 4-10µ µg/m .
119
Airborne Elemental Concentrations and Their Indoor and Outdoor Relationships. Associated with PM mass,
120
indoor elemental concentrations were also substantially lower than the corresponding outdoor values (SI-Figure
121
S5 and SI-Figure S6). The sum of the airborne concentrations of 47 target elements in PM2.5 was 0.31±0.16µg/m3
122
for indoor and 1.4±0.50µg/m3 for outdoor, contributing 6-23% (11% on average) to both indoor and outdoor PM2.5
123
mass. Crustal and sea salt components including Na, Mg, Al, Si, Ca, Ti, Mn, and Fe dominated total elemental
ACS Paragon Plus Environment Page 6
Page 7 of 21
124
Environmental Science & Technology
concentrations in I/O PM2.5 accounting for 97% on average suggesting outdoor origins of indoor PM.
126
numbered heaviest lanthanoids, i.e. Tm and Lu (and the actinide Th) were detected in < 20% of indoor samples
127
and therefore excluded from further analysis. This is attributed to the lower abundances of heavy lanthanoids
128
compared with their lighter counterparts in the Earth’s crust45 and in other lanthanoid sources,13, 46-48 and very low
129
indoor PM2.5 mass concentrations. Importantly, individual lanthanoids (excluding Tm and Lu) were well-correlated
130
with PM2.5 mass (r=0.70±0.05) and with each other (r=0.82±0.20) in both indoor and outdoor PM2.5. These results
131
coupled with I/O concentration ratios < 1 for individual lanthanoids (0.11±0.09 for La to 0.47±0.32 for Ho) and
132
Σ12Ln (sum of the concentrations of 12 lanthanoids; 0.14±0.10) reflect their tendency to be primarily released in
133
unison. Hence, these elements were grouped separately from other representative elements and transition
134
metals in further discussions. Data were also expressed as µg element per g PM2.5 in Figure 2 (i.e. elemental
135
abundance) to account for significantly different indoor and outdoor PM2.5 mass concentrations. As seen, average
136
I/O abundance ratios were close to unity for the majority of elements providing additional evidence for infiltration
137
and/or ventilation of outdoor aerosols. 40
-1
-1
Average indoor abundances (µg g )
Further, although all targeted elements were consistently detected in outdoor samples, the two odd-
Average indoor abundances (µg g )
125
Ce
10
La
Nd
1
Pr Gd
Sm
Dy
Er
Eu
Yb 0.1 Tb
(a)
Ho
0.1
1
10
40 -1
Average outdoor abundances (µg g )
10
5
Si
10
4
10
3
10
2
10
1
10
0
Al
Ca
K Fe Zn SnV Ti Ni Sb Cu Ba Cr Mn Pb As Zr Sr Se Mo Ga Rb
Co
Cd
Mg Na
W Y Cs Hf
(b)
U
10
-1
10
-1
10
0
10
1
10
2
10
3
10
4
-1
10
5
Average outdoor abundances (µg g )
138 139 140
Figure 2. Comparison of average elemental abundances in indoor and outdoor PM2.5. The solid diagonal line represents a 1:1 relationship. Lanthanoid elements are shown on the left panel (a) and all the other elements are on the right panel (b).
141
Exceptions to this general rule included Na, Mg, Ga, Ba, and La (depicted in red color in Figure 2), which
142
exhibited low average I/O abundance ratios of 0.08±0.04, 0.20±0.08, 0.32±0.19, 0.17±0.06, and 0.40±0.22
143
respectively. As expected, Na, Mg, Ga, Ba, and La had 6-30, 3-9, 2-10, 3-12, and 2-8 fold elevated abundances in
ACS Paragon Plus Environment Page 7
Environmental Science & Technology
Page 8 of 21
144
outdoor PM2.5, respectively. Only Co (depicted in blue color in Figure 2b) had an average I/O abundance ratio > 1,
145
arising from episodic indoor releases of Co-bearing PM2.5, causing 10-330 fold elevated abundances in 5 samples
146
inside the school. The average cobalt I/O abundance ratio for the remaining 8 samples approached unity
147
(1.1±0.36) indicating that infiltration and/or ventilation of outdoor PM2.5 was the major indoor source even for
148
this element.
149
Anomalies in Indoor and Outdoor PM2.5 Elemental Compositions with Respect to the Local Soil. PM2.5
150
elemental abundances were normalized to corresponding local soil values49 to identify emission signatures of
151
metal-bearing PM2.5 sources. Figure 3 depicts results for two representative paired indoor and outdoor samples,
152
where again lanthanoids and non-lanthanoids are shown separately for clarity’s sake. In all cases, patterns in
153
Figure 3a through Figure 3d were irregular (i.e. not horizontal), representing anomalies of numerous elements
154
compared to the local soil. Additionally, normalized indoor and outdoor profiles for all elements with the
155
exception of Na, Mg, Co, Ga, and Ba (the same elements identified in Figure 2) were in-phase in Figure 3c and
156
Figure 3d, providing further evidence that indoor levels were predominantly controlled by infiltration and/or
157
ventilation of metal-bearing outdoor PM2.5. Again, only Co was more abundant inside the school as a consequence
158
of its indoor generation.
ACS Paragon Plus Environment Page 8
Page 9 of 21
Environmental Science & Technology
Indoor PM2.5 Outdoor PM2.5
0.1
La
Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
3
10
(c)
April 6 - 12 Indoor PM2.5
2
10
Outdoor PM2.5
1
10
0
10
-1
10
Indoor PM2.5 Outdoor PM2.5
0.1
La
Yb
Na Mg Al Si K Ca Ti V Cr Mn Fe Ni Co Cu Zn Ga As Se Rb Sr Y Zr Mo Cd Sn Sb Cs Ba Hf W Pb U
Sample abundance / Local soil abundance
160
April 12-18
(b) 1
10
2
Ce
Pr
(d)
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Yb
April 12 - 18 Indoor PM2.5 Outdoor PM2.5
10
1
10
0
-1
10
Na Mg Al Si K Ca Ti V Cr Mn Fe Ni Co Cu Zn Ga As Se Rb Sr Y Zr Mo Cd Sn Sb Cs Ba Hf W Pb U
April 6 - 12
Sample abundance / Local soil abundance
(a)
1
Sample abundance / Local soil abundance
Sample abundance / Local soil abundance
159
161 162 163 164 165
Figure 3. Comparison of elemental distribution patterns for two representative paired indoor and outdoor PM2.5 samples after 49 normalization to corresponding local soil values. Note that the time period April 6-12 corresponds to “background” and April 12-18 corresponds to refinery emission events as will be discussed later. Lanthanoids for the two time periods are shown in the top panels (a) and (b) and non-lanthanoids are shown in the bottom panels (c) and (d).
166
Lanthanum exhibited dichotomous behavior after normalization50 with distinct positive anomalies (La >> Ce)
167
in 10 paired samples (shown in Figure 3b for one representative sample) whereas La ≈ Ce for the remaining 3
168
paired samples (shown in Figure 3a for one representative sample). Local soil-normalized lanthanoid patterns in
169
indoor and outdoor PM2.5 were compared with various lanthanoid-bearing sources including FCC catalysts,13 #6
170
grade fuel oils,47 steel plant dust,46 coal-fired power plant emissions,48 vehicular emissions,51 and local road dust49
171
(SI-Figure S7). Distinct La enrichment over Ce in the event samples corresponds to the lanthanoid-pattern in FCC
172
catalysts, fuel oils, and steel plant emissions (Figure 3b and SI-Figure S7) whereas similar normalized La and Ce
173
values signifies largely crustal origins for non-event samples (Figure 3a). An identical pattern of La enrichment
174
over Ce and other heavier lanthanoid members in PM2.5 in Houston, TX and other locations has been primarily
ACS Paragon Plus Environment Page 9
Environmental Science & Technology
Page 10 of 21
175
attributed to emissions from FCC units in petroleum refineries with lesser contributions from oil combustion and
176
shipping activities.13, 14, 18, 20, 47, 52-54
177
These observations of the degree of anthropogenic modifications to elemental abundances in PM2.5 compared
178
to the local soil in Figure 3 were confirmed by examining enrichment factors using Ti in local soil as the crustal
179
reference (SI-Figure S8). Elevated La enrichment factors were calculated for nearly all indoor and outdoor samples
180
that exhibited positive La anomalies (corresponding to Figure 3b). Additionally, La was slightly more enriched in
181
outdoor PM2.5 (3.4-24.3) than indoor (3.7-8.2) consistent with the decrease in La abundance in indoor PM2.5
182
(Figure 2a). This is attributed to preferential La-enrichment in the coarser fraction of FCC stack emissions (0.7-14
183
µm)55, which infiltrates and/or ventilates to a lesser extent than the fine fraction.56 Further, enrichment factors for
184
light lanthanoids (La, Ce, Pr, Sm, and Gd) in indoor and outdoor PM2.5 with respect to Nd in FCC catalysts were ≈ 1
185
(1.3±0.9) verifying that their origin can be predominantly traced to petroleum refining FCC units.13 The only
186
exception was Eu that exhibited high enrichment factors (19.4±8.5) in both indoor and outdoor PM2.5 with respect
187
to the FCC catalysts and showed positive anomaly in their local soil-normalized lanthanoid patterns (Figure 3a and
188
Figure 3b) as in other environmental samples50 also reflecting possible contributions from vehicular emissions and
189
road dust (SI-Figure S7).
190
Distinct positive anomalies for non-lanthanoids including Na, K, V, Ni, Co, Cu, Zn, Ga, As, Se, Mo, Cd, Sn, Sb,
191
Ba, W, and Pb were also observed for two representative indoor and outdoor samples (Figure 3c and Figure 3d).
192
These elements have been commonly reported to be emitted by anthropogenic sources in the Houston Ship
193
Channel area.14-16, 18, 20 Average enrichment factors of these elements in indoor PM2.5 were between 3 (Zn, Ga,
194
and Ba) and 307 (Sb) with respect to Ti in the local soil demonstrating their non-crustal origins. Importantly, all
195
these elements enriched inside the school were also enriched in outdoor PM2.5 (SI-Figure S8). Greater abundances
196
and correspondingly higher enrichment factors of Ga and Ba in outdoor PM2.5 (Figure 2b, Figure 3c, Figure 3d, and
197
SI-Figure S8) are traced to road dust.49,
198
attributed to sea salt.57, 58 Another sea salt component, Na displayed weak excursions in local soil-normalized
199
indoor PM2.5 whereas it showed distinct positive anomalies and correspondingly higher enrichment factors in
200
outdoor PM2.5 (Figure 2b, Figure 3c, Figure 3d, and SI-Figure S8). Similar results have been also been reported for
51
Mg exhibited positive anomalies in outdoor PM only57 and was
ACS Paragon Plus Environment Page 10
Page 11 of 21
Environmental Science & Technology
201
Houston homes where mechanically generated aerosol particles including road dust, soil, and sea salt had very
202
low infiltration factors resulting in their low abundances in the indoor environment.56
203
Cobalt was highly enriched in five indoor PM2.5 samples (average enrichment factor = 245 with respect to the
204
local soil) suggesting its episodic indoor emissions59 even though it was only slightly enriched in outdoor PM2.5
205
(average outdoor enrichment factor = 6). Although its indoor source could not be definitively identified, cobalt has
206
also been previously reported to be enriched in indoor dust and aerosols,60, 61 and probably arose from paints,
207
lacquers, and/or building materials. All other elements showed crustal origins since average enrichment factors
208
were close to unity. Indoor and outdoor enrichment factors for all other non-crustal elements were comparable
209
(SI-Figure S8) due to their prevailing origins in infiltration and/or ventilation.
210
Source Contributions to Indoor and Outdoor PM2.5 Mass with Emphasis on Lanthanoids. Details of the CMB
211
procedure, source profiles, and input data statistics are given in the SI (SI-Table S2). Since the dominant source of
212
indoor PM2.5 was infiltration and/or ventilation, outdoor sources of primary particles and their individual
213
contributions to indoor and outdoor PM2.5 mass were computed by CMB. Robust model runs were achieved as
214
evidenced by high R2 (0.81-0.97; average 0.91) and low χ2 (0.2-2.4; average 0.69).37 CMB apportioned 46-95%
215
(average 62%) of indoor and 54-95% (average 76%) of outdoor PM2.5 mass to 10 outdoor sources. SI-Figure S9 and
216
SI-Figure S10 summarize average and daily contributions of individual sources to indoor and outdoor PM2.5 mass
217
over the entire sampling period, respectively. As seen, vehicular emissions contributed most to PM2.5 mass
218
consistent with the school’s proximity to several heavily trafficked highways as shown in the site map (SI-Figure
219
S1) and the importance of gasoline-driven vehicles to ambient PM in Houston, TX.49, 51, 62 Similar results were also
220
reported for indoor and outdoor PM2.5 in a California school that was located near busy roadways.24 This was
221
followed by vegetative burning, soil and road dust, petroleum refineries, Ca-rich material, oil combustion, and
222
coal combustion. Sea salt contributed about 5% to outdoor PM2.5 but negligibly to indoor PM2.5 consistent with
223
Figure 3 leading to its resolution only for outdoor PM2.5 similar to an earlier investigation of Houston-area
224
residences.56 Incineration and steel plants played negligible roles for both indoor and outdoor PM2.5. Importantly,
225
contributions of individual outdoor sources to indoor and outdoor PM2.5 were very similar, with slightly higher
226
values estimated for outdoor PM2.5, consistent with infiltration and/or ventilation being the dominant source of ACS Paragon Plus Environment Page 11
Environmental Science & Technology
227
Page 12 of 21
indoor PM2.5. The only exception was for soil/road dust (10% for indoor versus 5.5% for outdoor on average).
228
CMB modeling also allowed us to isolate outdoor sources of lanthanoid-rich particles infiltrating and/or
229
ventilating indoors and resulting enrichment in La and total lanthanoid content of indoor PM2.5. Since only FCC
230
units and oil combustion were calculated to be significant sources of La-rich particles, a time series of their
231
estimated contributions to each indoor and outdoor sample are illustrated in Figure 4 together with the
232
corresponding La fraction of total lanthanoids, ∑12Ln. As seen, over the entire study duration, refinery FCC units’
233
contributions to total PM2.5 mass were low, averaging only 0.14±0.09 and 0.85±0.62µg/m3 for indoor and outdoor
234
PM2.5 respectively. Lowest FCC catalyst contributions were calculated for samples collected on March 17-19,
235
March 21-23, and April 6-12, averaging < 1.5% of both indoor and outdoor PM2.5 mass. Corresponding La fraction
236
in total lanthanoids (Σ12Ln) were 19%-24% (21±3%) for indoor PM2.5 and 24-34% (29±5%) for outdoor PM2.5, which
237
are in the range (21-31%) associated with crustal and light-duty vehicular emissions45, 49, 51 as discussed in Figure
238
3a. Hence, indoor and outdoor PM2.5 during these days correspond to routine operation of FCC units.13, 14, 18, 19 FCC unit
Oil combustion/shipping
-3
Source contribution estimates (µg m )
Outdoor
(a)
80
2.8
60
2.1 1.4
40
0.7
20
0.0
0
0.4
100
(b)
Indoor
80
0.3 60 0.2 40 0.1
20
May 5-11
Apr 30-May 5
Apr 24-30
Apr 18-24
Apr 12-18
Apr 06-12
Mar 31-Apr 6
Mar 25-31
Mar 21-23
Mar 19-21
Mar 17-19
Mar 13-15
0 Mar 11-13
0.0
La contribution to total lanthanoids (%)
100 3.5
239 240 241 242 243
Figure 4. Contributions of the two major La-rich PM emission sources (refinery fluid-cracking catalysts and oil combustion/shipping activities) estimated by CMB modeling and shown in the left y-axis as a stacked-bar graph. Percent contributions of La to ∑12Ln content of indoor and outdoor PM2.5 are shown in the right y-axis in brown color as a time-series line plot. Results for outdoor air are shown in the top panel (a) and for indoor air are shown in the bottom panel (b).
244
In contrast to these three paired samples, the remaining 10 paired indoor and outdoor PM2.5 displayed ACS Paragon Plus Environment Page 12
Page 13 of 21
Environmental Science & Technology
245
significant La enrichment. Their La fractions in Σ12Ln were between 40-59% (49±7%) for indoor and between 40-
246
83% (61±14%) for outdoor PM2.5, closely mirroring the range reported for FCC catalysts (40-79%)13 and #6 grade
247
fuel oil (30-54%).47 Average contributions of FCC catalyst emissions to these 10 samples increased to 5.0±2.3%
248
(2.0-8.1%) for indoor PM2.5 mass and 7.9±4.6% (3.0-18.2%) for outdoor PM2.5 mass (SI-Figure S9 and SI-Figure S10)
249
in accordance with earlier reports of oil-cracking catalysts emission events in Houston, TX.14, 18, 19 Strong direct
250
correlations between the La fraction in Σ12Ln and estimated FCC source contributions in indoor and outdoor PM2.5
251
(also evidenced by co-located peaks and valleys in Figure 4 and Pearson r values of 0.61 for indoor PM2.5 and 0.89
252
for outdoor PM2.5) demonstrated that La enrichment was largely determined by episodic emissions from proximal
253
petroleum refineries.14,
254
encompassed a short-lived episodic release along with a longer period of routine FCC operations. Measured La
255
enrichment was further verified using lanthanoids as elemental tracers as explained in the next section.
256 257
18, 20, 52, 53, 63
Since PM was collected over 2-6 days, the 10 La-enriched samples likely
The only other significant source of La-rich PM2.5, i.e. oil combustion/shipping activities, contributed far less; averaging only 0.05±0.01µg/m3 to indoor PM2.5 mass and 0.35±0.24µg/m3 to outdoor PM2.5 mass (Figure 4).
258
Tracking Episodic Catalyst Emissions from Petroleum Refineries Using Lanthanoids. Shifts from crustal to
259
anthropogenic signatures of lanthanoids were used to identify PM influenced by non-routine FCC unit
260
operations.14, 18, 20, 52 To this end, Table 1 summarizes concentration ratios of La to other light lanthanoids (Ce, Pr,
261
Nd, and Sm) and V calculated for indoor and outdoor PM2.5 along with those previously reported for ambient
262
PM2.5 in Houston14, 19 and for local soil.49 The same ratios reported for average UCC45 and other potential outdoor
263
sources of lanthanoid-bearing PM13, 46, 48, 49, 51 are provided in SI-Table S3. As seen, all ratios for the 3 paired indoor
264
and outdoor samples identified in the previous section as corresponding to routine FCC operation were coincident
265
with complementary local soil/road dust and earlier reports of ambient PM2.5 collected during routine FCC
266
operation. This confirms that lanthanoids in indoor and outdoor PM2.5 collected on March 17-19, March 21-23,
267
and April 6-12 predominantly originated from resuspension of crustal material.
ACS Paragon Plus Environment Page 13
Environmental Science & Technology
268 269 270
Page 14 of 21
Table 1. Tracer element ratios (as a range of min – max (mean) values) for paired indoor and outdoor PM2.5 samples that were collected at the school during routine and non-routine operations of FCC units in petroleum refineries along with those previously reported values 14, 19 49 for ambient PM2.5 from the Houston Ship Channel area and for local soil. Indoor PM2.5 (This study)
Ambient PM2.5 from the Houston Ship Channel area
Outdoor PM2.5 (This study)
Ratios Event (n=10)
Non-Event (n=3)
Event (n=10)
Non-event (n=3)
La/Ce
1.0 - 3.9 (1.7)
La/Pr
10.8 - 25.9 (17.3)
0.33 - 0.48 (0.42)
1.1 - 7.6 (3.3)
4.1 - 4.8 (4.5)
13.7 - 103. 6 (41.1)
La/Nd
2.8 - 11.9 (6.4)
1.3 - 1.6 (1.4)
La/Sm
14.6 - 58.5 (38.5)
La/V
0.01 - 0.04 (0.02)
Local soil
Event
Non-event
0.55 -0.87 (0.72)
1.0 - 6.8 (2.6)
0.51 - 0.89 (0.70)
0.63
5.9 - 10.3 (8.2)
6.9 - 40.2 (18.2)
4.5 - 8.0 (6.4)
5.8
3.8 - 29.6 (11.9)
1.7 - 2.8 (2.3)
2.4 - 22.7 (7.2)
1.2 - 2.2 (1.8)
1.5
4.8 - 14.6 (9.2)
20.9 - 120.5 (46.0)
5.0 - 11.8 (8.0)
12.1 - 76.8 (36.6)
6.5 - 10.1 (8.7)
7.1
0.003 - 0.02 (0.01)
0.02 - 0.07 (0.05)
0.01 - 0.02 (0.01)
0.01 - 1.8 (0.17)
0.02 - 0.23 (0.09)
1
271
Consistent with modeling results, lanthanoid patterns in the other 10 paired indoor and outdoor PM2.5 were
272
distorted from crustal material, exhibiting elevated La concentrations over other lanthanoids (e.g. La/Ce = 1.0-7.6;
273
Table 1). La to Ce, Pr, Nd, and Sm ratios in all 10 paired indoor and outdoor PM2.5 samples influenced by FCC
274
events overlapped with those previously reported for oil-cracking catalysts13, 48 and oil-fired plants47, 48 as well as
275
those for Houston aerosols exposed to episodic catalysts releases from refinery FCC units14, 19 (Table 1 and SI-
276
Table S3). Outdoor Σ12Ln concentrations doubled under the influence of episodic FCC emissions
277
(551.1±241.7pg/m3) from the background (273.1±89.9pg/m3) similar to earlier reports.14, 20 Corresponding average
278
Σ12Ln concentrations in paired indoor samples also increased from their background (44.5±26.7pg/m3) to
279
60.3±34.5pg/m3 during FCC events.
ACS Paragon Plus Environment Page 14
35
-3
-3
Lanthanoid concentrations in PM2.5 (pg m )
Environmental Science & Technology Lanthanoid concentrations in PM2.5 (pg m )
Page 15 of 21
Indoor PM2.5 30 25 20
FCC events (n = 10)
La
La/Ce = 1.7 La/Pr = 17.3 La/Nd = 6.4 La/Sm = 38.5
Ce
15 2
R = 0.94, p < 0.01
10 5
Nd Eu Er Sm Pr 0 Yb DyGd TbHo 0
(a)
2000
4000
6000
400 350 300 250
2
50
Eu Nd Yb Gd Pr Er Sm 0 Ho TbDy
(b)
2000
4000
6000
8000 -1
Lanthanoid concentrations in FCC catalysts (µg g ) Lanthanoid concentrations in PM2.5 (pg m )
-3
-3
Lanthanoid concentrations in PM2.5 (pg m )
Ce
Routine days (n = 3) La/Ce = 0.42 La/Pr = 4.5 La/Nd = 1.4 La/Sm = 9.2 La
10 2
R = 0.97, p < 0.01 Nd 5
0
Ce
0
Indoor PM2.5
15
R = 0.97, p < 0.01
100
-1
20
La/Ce = 3.3 La/Pr = 41.1 La/Nd = 11.9 La/Sm = 46.0
150
8000
25
La
FCC events (n = 10)
200
Lanthanoid concentrations in FCC catalysts (µg g )
280
Outdoor PM2.5
Pr Gd Dy Eu Sm Ho YbEr 0
5
(c) 10
15
20
25
30
35
40 -1
Lanthanoid concentrations in the local soil (µg g )
120
Outdoor PM2.5
Ce
Routine days (n = 3) 100 80
La/Ce = 0.72 La/Pr = 8.2 La/Nd = 2.3 La/Sm = 8.0
La
60 2
R = 0.99, p < 0.01 40 20 0
Nd Pr Dy Sm Eu Gd Er Ho Tb Yb 0
5
(d) 10
15
20
25
30
35
40 -1
Lanthanoid concentrations in the local soil (µg g )
281 282 283 284 285 286
Figure 5. Positive and significant correlations between average lanthanoid concentrations in FCC catalysts and those in indoor and outdoor PM2.5 monitored during non-routine refinery FCC unit operations (top panels (a) and (b)). Episodic indoor and outdoor samples and cracking catalysts showed similar rare earth distribution patterns demonstrating that FCC units were the source of lanthanoidbearing PM2.5 for both indoor and outdoor environments. Indoor and outdoor PM2.5 samples collected during routine refinery 49 operations were strongly correlated with the local soil showing their crustal origins (bottom panels (c) and (d)).
287
It is emphasized that La-enrichment in samples need not overlap with episodic events because impacts at
288
receptor sites are also influenced by meteorology and atmospheric dispersion.63 The prevailing wind direction
289
during sampling was predominantly from the South (S, SSE, and SE; SI-Figure S1 and SI-Figure S3) transporting
290
emissions from the ship channel and possibly Galveston area to the receptor location. In any case, variations in
291
dispersion conditions during sampling could also influence the extent of La-enrichment in individual samples.
13
292
Excellent correlations were obtained between average lanthanoid concentrations in FCC catalysts and those in
293
indoor and outdoor PM2.5 under the influence of non-routine FCC operations (Figure 5a and Figure 5b).
294
Correlations between average lanthanoid concentrations in indoor and outdoor PM2.5 during routine refinery
295
operations and those in the local soil were also extremely strong (Figure 5c and Figure 5d). This confirms CMB ACS Paragon Plus Environment Page 15
Environmental Science & Technology
Page 16 of 21
296
modeling results that lanthanoid enrichment was largely attributable to FCC catalysts during episodic events
297
whereas during routine FCC operation lanthanoid patterns were consistent with crustal resuspension.
298
Relative Compositions of Source and Receptor Particles. Additional clues to the relative influence of sources
299
rich in light lanthanoids on indoor and outdoor PM2.5 were obtained using La-Ce-Sm (Figure 6a) and La-Ce-V
300
(Figure 6b) ternary diagrams adjusted so that the local soil abundances appear at the centroid. As expected from
301
similar La to Ce, Pr, Nd, and Sm ratios (Table 1 and SI-Table S3), local soil and UCC were located near each other
302
(Figure 6a). Vehicular emissions were slightly enriched in Ce and depleted in La and Sm with respect to local soil.
303
Major local La-rich sources such as FCC catalysts and oil combustion/shipping migrate towards the La-apex
304
overlapping with the 10 paired indoor and outdoor PM2.5 collected during FCC episodes. In contrast, the 3 paired
305
indoor and outdoor samples collected during routine FCC operations (identified in earlier sections) clustered
306
around the local soil and vehicular emissions. 0.0
(a)
1.0
0.2
Sa
m na diu
Routine (This study)
0.4
0.8
Va
ma ri
m
Indoor and outdoor PM2.5
0.0 0.2
0.4
0.6
0.8
1.0
0.6
0.6
0.4
0.8
0.2
1.0
0.4
.62 x0
riu
um
FCC event (This study)
0.8
m riu
0.6
1.0
0.2
Indoor and outdoor PM2.5
0.4
Ce
x1
(b)
Ce
1. 2
4
0.8
0.6
0.0
0.0
Local soil UCC Local road dust Car emissions FCC catalysts Oil combustion / Shipping
0.2
1.0 0.0
0.0 0.2
0.4
0.6
0.8
1.0
Lanthanum x 0.99
Lanthanum x 1.58
307 308 309 310
Figure 6. Three component La-Ce-Sm (left panel, (a)) and La-Ce-V (right panel, (b)) plots showing PM2.5 influenced by FCC units and other 13, 47-49, 51, 64, 65 49 possible outdoor sources of lanthanoid-bearing particles. All values were adjusted so that the local soil appears at the center.
311
Simultaneous variations in La-Ce-V and the La/V ratio were used to differentiate FCC emissions from oil
312
combustion/shipping activities. Shipping, oil and pet-coke combustion cause enormous V enrichment relative to
313
La47, 52, 54, 64, 65 leading to characteristically low La/V ratios between 0.0001–0.11 depending on the type of fuel,
314
pushing these sources towards the V-apex in Figure 6b. In contrast, FCC catalysts13 and stack emissions from FCC
315
units have markedly higher La/V ratios of 131±70 and 13 respectively (SI-Table S3) aligning near the La apex in
316
Figure 6b. The La-Ce-V ternary diagram illustrates that all indoor and outdoor PM2.5 collected over the duration of
ACS Paragon Plus Environment Page 16
Page 17 of 21
Environmental Science & Technology
317
this investigation were substantially enriched in V; also reflected in their very low indoor and outdoor La/V ratios
318
(0.003-0.07) corresponding to oil combustion/shipping activities (SI-Table S3).
319
Results reported herein demonstrate that most of the indoor PM2.5 mass and its metallic components in a
320
mechanically ventilated school located in a highly industrialized area arose via transport from the outside. Co was
321
the sole exception exhibiting enrichment only in indoor PM2.5. Quantifying lanthanoids that serve as unique
322
tracers for primary emissions from catalytic cracking units along with a wide suite of elements in paired indoor
323
and outdoor PM2.5 facilitated robust estimation of outdoor source contributions to indoor PM2.5 mass. Since
324
samples were collected from a largely unoccupied room inside the school, our measurements potentially reflect a
325
lower-bound in indoor air concentrations. Of the sources identified via CMB modeling, automotive emissions
326
contributed most to indoor and outdoor PM2.5 mass. Importantly, airborne fine particles originating during non-
327
routine operations of refinery FCC units were shown to penetrate the building envelope leading to La-enrichment
328
(with respect to local soil) in indoor PM2.5. Hazardous air pollutants such as Ni, As, Se, Cd, Sb, and Pb, enriched in
329
outdoor air with respect to local soil were detected inside the school environment, albeit at substantially lower
330
concentrations than outdoor values (e.g. 0.13ng/m3 in indoor and 0.61ng/m3 in outdoor for Ni). Finally, since
331
proximity to emission sources, source strength, and meteorological conditions govern outdoor air quality at
332
receptor locations,66 additional work is needed to investigate potential spatial and temporal differences in
333
children’s exposure to PM2.5 via infiltration and/or ventilation in schools.
334
Supporting Information. Additional details on sampling, laboratory work (including QA/QC), CMB modeling
335
procedures and estimated source contributions, signature elemental ratios, sampling site maps, wind roses,
336
elemental concentrations and I/O ratios, source profiles normalized to local soil levels, and enrichment factors are
337
provided. This material is available free of charge via the internet at http://pubs.acs.org.
338
Acknowledgments. The present study has been supported by NPRP award number NPRP 7-649-2-241 from the
339
Qatar National Research Fund (a member of The Qatar Foundation). Sima Mathew-Tanner, Will Payne, Steve
340
Paciotti, Nick Spada, and Suresh Danadurai assisted with sampling.
341 342 ACS Paragon Plus Environment Page 17
Environmental Science & Technology
343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393
Page 18 of 21
REFERENCES 1. Bateson, T. F.; Schwartz, J., Children's response to air pollutants. J. Toxicol. Env. Health Part A 2008, 71, (3), 238-243. 2. Koenig, J. Q.; Mar, T. F.; Allen, R. W.; Jansen, K.; Lumley, T.; Sullivan, J. H.; Trenga, C. A.; Larson, T. V.; Liu, L.-J. S., Pulmonary effects of indoor- and outdoor-generated particles in children with asthma. Environ. Health Perspect. 2005, 113, 499-503. 3. Gauderman, W. J.; Avol, E.; Gilliland, F.; Vora, H.; Thomas, D.; Berhane, K.; McConnell, R.; Kuenzli, N.; Lurmann, F.; Rappaport, E.; Margolis, H.; Bates, D.; Peters, J., The effect of air pollution on lung development from 10 to 18 years of age. N. Engl. J. Med. 2004, 351, (11), 1057-1067. 4. Bell, M. L.; Ebisu, K.; Peng, R. D.; Samet, J. M.; Dominici, F., Hospital admissions and chemical composition of fine particle air pollution. Am. J. Respir. Crit. Care Med. 2009, 179, 1115-1120. 5. Chen, L. C.; Lippmann, M., Effects of metals within ambient air particulate matter (PM) on human health. Inhal. Toxicol. 2009, 21, 1-31. 6. Calderon-Garciduenas, L.; Serrano-Sierra, A.; Torres-Jardon, R.; Zhu, H. T.; Yuan, Y.; Smith, D.; Delgado-Chavez, R.; Cross, J. V.; Medina-Cortina, H.; Kavanaugh, M.; Guilarte, T. R., The impact of environmental metals in young urbanites' brains. Exp. Toxicol. Pathol. 2013, 65, (5), 503-511. 7. de Gennaro, G.; Dambruoso, P. R.; Loiotile, A. D.; Gilio, A. D.; Giungato, P.; Tutino, M.; Marzocca, A.; Mazzone, A.; Palmisani, J.; Porcelli, F., Indoor air quality in schools. Environ. Chem. Lett. 2014, 12, 467-482. 8. Gray, D. L.; Wallace, L. A.; Brinkman, M. C.; Buehler, S. S.; La Londe, C., Respiratory and Cardiovascular Effects of Metals in Ambient Particulate Matter: A Critical Review. In Reviews of Environmental Contamination and Toxicology, Vol 234, Whitacre, D. M., Ed. 2015; Vol. 234, pp 135-203. 9. Mejia, J. F.; Choy, S. L.; Mengersen, K.; Morawska, L., Methodology for assessing exposure and impacts of air pollutants in school children: Data collection, analysis and health effects - A literature review. Atmos. Environ. 2011, 45, 813-823. 10. Liu, S.; Ganduglia, C. M.; Li, X.; Delclos, G. L.; Franzini, L.; Zhang, K., Short-term associations of fine particulate matter components and emergency hospital admissions among a privately insured population in Greater Houston. Atmos. Environ. 2016, 147, 369-375. 11. Sexton, K.; Linder, S. H.; Marko, D.; Bethel, H.; Lupo, P. J., Comparative assessment of air pollution-related health risks in Houston. Environ. Health Perspect. 2007, 115, (10), 1388-1393. 12. Liu, S. Y.; Zhang, K., Fine particulate matter components and mortality in Greater Houston: Did the risk reduce from 2000 to 2011? Sci. Total Environ. 2015, 538, 162-168. 13. Kulkarni, P.; Chellam, S.; Fraser, M., Lanthanum and lanthanides in atmospheric fine particles and their apportionment to refinery and petrochemical operations in Houston, TX. Atmos. Environ. 2006, 40, (3), 508520. 14. Kulkarni, P.; Chellam, S.; Fraser, M., Tracking petroleum refinery emission events using lanthanum and lanthanides as elemental markers for PM2.5. Environ. Sci. Technol. 2007, 41, (19), 6748-6754. 15. Dillner, A. M.; Schauer, J. J.; Christensen, W. F.; Cass, G. R., A quantitative method for clustering size distributions of elements. Atmos. Environ. 2005, 39, 1525-1537. 16. Sullivan, D. W.; Price, J. H.; Lambeth, B.; Sheedy, K. A.; Savanich, K.; Tropp, R. J., Field study and source attribution for PM2.5 and PM10 with resulting reduction in concentrations in the neighborhood north of the Houston Ship Channel based on voluntary efforts. J. Air Waste Manage. Assoc. 2013, 63, (9), 1070-1082. 17. http://www.census.gov/quickfacts/table/INC110214/4827996 (Accessed on February 20, 2017). 18. Bozlaker, A.; Buzcu-Guven, B.; Fraser, M.; Chellam, S., Insights into PM10 sources in Houston, Texas: Role of petroleum refineries in enriching lanthanoid metals during episodic emission events. Atmos. Environ. 2013, 69, 109-117. 19. Bozlaker, A.; Prospero, J. M.; Fraser, M.; Chellam, S., Quantifying the contribution of long-range Saharan dust transport on particulate matter concentrations in Houston, Texas, using detailed elemental analysis. Environ. Sci. Technol. 2013, 47, 10179-10187. 20. Danadurai, K. S. K.; Chellam, S.; Lee, C. T.; Fraser, M., Trace elemental analysis of airborne particulate matter using dynamic reaction cell inductively coupled plasma - mass spectrometry: Application to monitoring episodic industrial emission events. Anal. Chim. Acta 2011, 686, (1-2), 40-49. ACS Paragon Plus Environment Page 18
Page 19 of 21
394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444
Environmental Science & Technology
21. Mayor’s Task Force on the Health Effects of Air Pollution A Closer Look at Air Pollution in Houston: Identifying Priority Health Risks; University of Texas School of Public Health, Institute for Health Policy: Houston, TX, 2006. 22. John, K.; Karnae, S.; Crist, K.; Kim, M.; Kulkarni, A., Analysis of trace eements and ions in ambient fine particulate matter at three elementary schools in Ohio. J. Air Waste Manage. Assoc. 2007, 57, 394-406. 23. Na, K.; Sawanta, A. A.; Cocker III, D. R., Trace elements in fine particulate matter within a community in western Riverside County, CA: focus on residential sites and a local high school. Atmos. Environ. 2004, 38, 2867-2877. 24. Zhao, W.; Hopke, P. K.; Gelfand, E. W.; Rabinovitch, N., Use of an expanded receptor model for personal exposure analysis in schoolchildren with asthma. Atmos. Environ. 2007, 41, 4084-4096. 25. Majestic, B. J.; Turner, J. A.; Marcotte, A. R., Respirable antimony and other trace-elements inside and outside an elementary school in Flagstaff, AZ, USA. Sci. Total Environ. 2012, 435-436, 253-261. 26. Hochstetler, H. A.; Yermakov, M.; Reponen, T.; Ryan, P. H.; Grinshpun, S. A., Aerosol particles generated by diesel-powered school buses at urban schools as a source of children's exposure. Atmos. Environ. 2011, 45, (7), 1444-1453. 27. Tunno, B. J.; Dalton, R.; Cambal, L.; Holguin, F.; Lioy, P.; Clougherty, J. E., Indoor source apportionment in urban communities near industrial sites. Atmos. Environ. 2016, 139, 30-36. 28. Adgate, J. L.; Mongin, S. J.; Pratt, G. C.; Zhang, J.; Field, M. P.; Ramachandran, G.; Sexton, K., Relationships between personal, indoor, and outdoor exposures to trace elements in PM2.5. Sci. Total Environ. 2007, 386, (13), 21-32. 29. Hasheminassab, S.; Daher, N.; Shafer, M. M.; Schauer, J. J.; Delfino, R. J.; Sioutas, C., Chemical characterization and source apportionment of indoor and outdoor fine particulatematter (PM2.5) in retirement communities of the Los Angeles Basin. Sci. Total Environ. 2014, 490, 528-537. 30. Li, Y.; Yu, H.; Li, P.; Bian, Y., Assessment the exposure level of rare earth elements in workers producing cerium, lanthanum oxide ultrafine and nanoparticles. Biol. Trace Elem. Res. 2017, 175, (2), 298-305. 31. Li, X.; Chen, Z.; Chen, Z.; Zhang, Y., A human health risk assessment of rare earth elements in soil and vegetables from a mining area in Fujian Province, Southeast China. Chemosphere 2013, 93, (6), 1240-1246. 32. Rim, K. T.; Koo, K. H.; Park, J. S., Toxicological evaluations of rare earths and their health impacts to workers: A literature review. Saf. Health Work. 2013, 4, (1), 12-26. 33. Rusconi, F.; Catelan, D.; Accetta, G.; Peluso, M.; Pistelli, R.; Barbone, F.; Di Felice, E.; Munnia, A.; Murgia, P.; Paladini, L.; Serci, A.; Biggeri, A., Asthma symptoms, lung function, and markers of oxidative stress and Inflammation in children exposed to oil refinery pollution. J. Asthma 2011, 48, 84-90. 34. Wichmann, F. A.; Muller, A.; Busi, L. E.; Cianni, N.; Massolo, L.; Schlink, U.; Porta, A.; Sly, P. D., Increased asthma and respiratory symptoms in children exposed to petrochemical pollution. J. Allergy Clin. Immunol. 2009, 123, (3), 632-638. 35. McCoy, B. J.; Fischbeck, P. S.; Gerard, D., How big is big? How often is often? Characterizing Texas petroleum refining upset air emissions. Atmos. Environ. 2010, 44, (34), 4230-4239. 36. Watson, J. G.; Robinson, N. F.; Chow, J. C.; Henry, R. C.; Kim, B. M.; Pace, T. G.; Meyer, E. L.; Nguyen, Q., The USEPA/DRI chemical mass balance receptor model, CMB 7.0. Environ. Softw. 1990, 5, (1), 38-49. 37. Coulter, C. T., EPA-CMB8.2 Users Manual. In US Environmental protection Agency: 2004. 38. Azimi, P.; Zhao, D.; Stephens, B., Estimates of HVAC filtration efficiency for fine and ultrafine particles of outdoor origin. Atmos. Environ. 2014, 98, 337-346. 39. Nazaroff, W. W., Indoor particle dynamics. Indoor Air 2004, 14, (7), 175-183. 40. Kulkarni, P.; Chellam, S.; Flanagan, J. B.; Jayanty, R. K. M., Microwave digestion-ICP-MS for elemental analysis in ambient airborne particulate matter: Rare earth elements and validation using a filter borne particle certified reference material. Anal. Chim. Acta 2007, 599, 170-176. 41. Raysoni, A. U.; Stock, T. H.; Sarnat, J. A.; Sosa, T. M.; Sarnat, S. E.; Holguin, F.; Greenwald, R.; Johnson, B.; Li, W. W., Characterization of traffic-related air pollutant metrics at four schools in El Paso, Texas, USA: Implications for exposure assessment and siting schools in urban areas. Atmos. Environ. 2013, 80, 140-151. 42. Zhang, Q.; Zhu, Y., Characterizing ultrafine particles and other air pollutants at five schools in South Texas. Indoor Air 2012, 22, 33-42. ACS Paragon Plus Environment Page 19
Environmental Science & Technology
445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496
Page 20 of 21
43. Chen, C.; Zhao, B., Review of relationship between indoor and outdoor particles: I/O ratio, infiltration factor and penetration factor. Atmos. Environ. 2011, 45, 275-288. 44. Abt, E.; Suh, H. H.; Catalano, C.; Koutrakis, P., Relative contribution of outdoor and indoor particle sources to indoor concentrations. Environ. Sci. Technol. 2000, 34, 3579-3587. 45. Wedepohl, K. H., The composition of the continental crust. Geochim. Cosmochim. Acta 1995, 59, (7), 12171232. 46. Geagea, M. L.; Stille, P.; Millet, M.; Perrone, T., REE characteristics and Pb, Sr, and Nd isotopic compositions of steel plant emissions. Sci. Total Environ. 2007, 373, 404-419. 47. Kitto, M. E., Trace-element patterns in fuel oils and gasolines for use in source apportionment. J. Air Waste Manage. Assoc. 1993, 43, (10), 1381-1388. 48. Olmez, I.; Sheffield, A. E.; Gordon, G. E.; Houck, J. E.; Pritchett, L. C.; Cooper, J. A.; Dzubay, T. G.; Bennett, R. L., Compositions of particles from selected sources in Philadelphia for receptor modeling applications. J. Air Waste Manage. Assoc. 1988, 38, (11), 1392-1402. 49. Spada, N. J.; Bozlaker, A.; Chellam, S., Multi-elemental characterization of tunnel and road dusts in Houston, texas using dynamic reaction cell-quadrupole-inductively coupled plasma-mass spectrometry: Evidence for the release of platinum group and anthropogenic metals from motor vehicles. Anal. Chim. Acta 2012, 735, 18. 50. Migaszewski, Z. M.; Galuszka, A., The characteristics, occurrence, and geochemical behavior of rare earth elements in the environment: A review. Crit. Rev. Environ. Sci. Technol. 2015, 45, (5), 429-471. 51. Bozlaker, A.; Spada, N. J.; Fraser, M.; Chellam, S., Elemental characterization of PM2.5 and PM10 emitted from light duty vehicles in the Washburn tunnel of Houston, TX: Release of rhodium, palladium, and platinum. Environ. Sci. Technol. 2014, 48, (1), 54-62. 52. Moreno, T.; Querol, X.; Alastuey, A.; Gibbons, W., Identification of FCC refinery atmospheric pollution events using lanthanoid- and vanadium-bearing aerosols. Atmos. Environ. 2008, 42, 7851-7861. 53. Moreno, T.; Querol, X.; Alastuey, A.; Pey, J.; Minguillon, M. C.; Perez, N.; Bernabe, R. M.; Blanco, S.; Cardenas, B.; Gibbons, W., Lanthanoid geochemistry of urban atmospheric particulate matter. Environ. Sci. Technol. 2008, 42, 6502-6507. 54. Olmez, I.; Gordon, G. E., Rare earths: Atmospheric signatures for oil-fired power plants and refineries. Science 1985, 229, (4717), 966-968. 55. de la Campa, A. M. S.; Moreno, T.; de la Rosa, J.; Alastuey, A.; Querol, X., Size distribution and chemical composition of metalliferous stack emissions in the San Roque petroleum refinery complex, southern Spain. J. Hazard. Mater. 2011, 190, (1-3), 713-722. 56. Meng, Q. Y.; Turpin, B. J.; Lee, J. H.; Polidori, A.; Weisel, C. P.; Morandi, M.; Colome, S.; Zhang, J. F.; Stock, T.; Winer, A., How does infiltration behavior modify the composition of ambient PM2.5 in indoor spaces? An analysis of RIOPA data. Environmental Science & Technology 2007, 41, (21), 7315-7321. 57. Almeida, S. M.; Canha, N.; Silva, A.; Freitas, M. D.; Pegas, P.; Alves, C.; Evtyugina, M.; Pio, C. A., Children exposure to atmospheric particles in indoor of Lisbon primary schools. Atmos. Environ. 2011, 45, (40), 75947599. 58. Keene, W. C.; Pszenny, A. A. P.; Galloway, J. N.; Hawley, M. E., Sea-salt corrections and interpretation of constituent ratios in marine precipitation. J. Geophys. Res. - Atmos. 1986, 91, (D6), 6647-6658. 59. Nazaroff, W. W., Indoor particle dynamics. Indoor Air 2004, 14, 175-183. 60. Viana, M.; Rivas, I.; Querol, X.; Alastuey, A.; Sunyer, J.; Alvarez-Pedrerol, M.; Bouso, L.; Sioutas, C., Indoor/outdoor relationships and mass closure of quasi-ultrafine, accumulation and coarse particles in Barcelona schools. Atmos. Chem. Phys. 2014, 14, 4459-4472. 61. Clayton, C. A.; Perritt, R. L.; Pellizzari, E. D.; Thomas, K. W.; Whitmore, R. W.; Wallace, L. A.; Ozkaynak, H.; Spengler, J. D., Particle total exposure assessment methodology (PTEAM) study - distributions of aerosol and elemental concentrations in personal, indoor, and outdoor air samples in a southern California community. J. Exposure Anal. Environ. Epidemiol. 1993, 3, (2), 227-250. 62. Russell, M.; Allen, D. T.; Collins, D. R.; Fraser, M. P., Daily, seasonal, and spatial trends in PM2.5 mass and composition in Southeast Texas. Aerosol Sci. Technol. 2004, 38, (S1), 14-26. 63. Du, L.; Turner, J., Using PM2.5 lanthanoid elements and nonparametric wind regression to track petroleum refinery FCC emissions. Sci. Total Environ. 2015, 529, 65-71. ACS Paragon Plus Environment Page 20
Page 21 of 21
497 498 499 500 501 502 503 504 505
Environmental Science & Technology
64. Moreno, T.; Perez, N.; Querol, X.; Amato, F.; Alastuey, A.; Bhatia, R.; Spiro, B.; Hanvey, M.; Gibbons, W., Physicochemical variations in atmospheric aerosols recorded at sea onboard the Atlantic–Mediterranean 2008 Scholar Ship cruise (Part II): Natural versus anthropogenic influences revealed by PM10 trace element geochemistry. Atmos. Environ. 2010, 44, 2563-2576. 65. Celo, V.; Dabek-Zlotorzynska, E.; McCurdy, M., Chemical characterization of exhaust emissions from selected Canadian marine vessels: The case of trace metals and lanthanoids. Environ. Sci. Technol. 2015, 49, 5220−5226. 66. Vardoulakis, S., Human Exposure: Indoor and Outdoor. In Air Quality in Urban Environments, Hester, R. E.; Harrison, R. M., Eds. Royal Society of Chemistry: 2009; Vol. 28, pp 85-107.
ACS Paragon Plus Environment Page 21