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Characterisation of atmospheric deposition as a source ofcontaminants in urban rainwater tanks

R. Hustona,b,d,f,*, Y.C. Chana,f, T. Gardnerc, G. Shawe,f, H. Chapmanb,g

aSchool of Environment, Griffith University, Nathan Campus, 170 Kessels Road, Brisbane, Queensland 4108, AustraliabCRC for Water Quality and Treatment, AustraliacQueensland Department of Natural Resources and Water, Queensland, AustraliadUniversity of Queensland, The National Research Centre for Environmental Toxicology, Queensland, AustraliaeSchool of Public Health, Griffith University, Queensland, AustraliafAustralian Rivers Institute, Griffith University, Queensland, AustraliagSmart Water Research Facility, Griffith University, Australia

a r t i c l e i n f o

Article history:

Received 13 October 2008

Received in revised form

19 December 2008

Accepted 22 December 2008

Published online 3 January 2009

Keywords:

Urban water

Atmospheric deposition

Bulk deposition

Heavy metals

Rainwater

Tank

Pb

Lead

Health risk

* Corresponding author. Tel.: þ61 4 2874 840E-mail address: r.huston@griffith.edu.au

0043-1354/$ – see front matter ª 2008 Elsevidoi:10.1016/j.watres.2008.12.045

a b s t r a c t

To characterise atmospheric input of chemical contaminants to urban rainwater tanks,

bulk deposition (wetþ dry deposition) was collected at sixteen sites in Brisbane, Queens-

land, Australia on a monthly basis during April 2007–March 2008 (N¼ 175). Water from

rainwater tanks (22 sites, 26 tanks) was also sampled concurrently. The deposition/tank

water was analysed for metals, soluble anions and selected samples were additionally

analysed for PAHs, pesticides, phenols, organic & inorganic carbon. Flux (mg/m2/d) of total

solids mass was found to correlate with average daily rainfall (R2¼ 0.49) indicating the

dominance of the wet deposition contribution to total solids mass. On average 97% of the

total mass of analysed components was accounted for by Cl� (25.0%), Na (22.6%), organic

carbon (20.5%), NO3� (10.5%), SO4

2� (9.8%), inorganic carbon (5.7%), PO43� (1.6%) and NO2

�

(1.5%). For other minor elements the average flux from highest to lowest was in the order of

Fe>Al> Zn>Mn> Sr> Pb> Ba>Cu> Se. There was a significant effect of location on flux

of K, Sb, Sn, Li, Mn, Fe, Cu, Zn, Ba, Pb and SO42� but not other metals or anions. Overall the

water quality resulting from the deposition (wetþ dry) was good but 10.3%, 1.7% and 17.7%

of samples had concentrations of Pb, Cd and Fe respectively greater than the Australian

Drinking Water Guidelines (ADWG). This generally occurred in the drier months. In

comparison 14.2% and 6.1% of tank samples had total Pb and Zn concentrations exceeding

the guidelines. The cumulative mean concentration of lead in deposition was on average

only 1/4 of that in tank water over the year at a site with high concentrations of Pb in tank

water. This is an indication that deposition from the atmosphere is not the major

contributor to high lead concentrations in urban rainwater tanks in a city with reasonable

air quality, though it is still a significant portion.

ª 2008 Elsevier Ltd. All rights reserved.

1. Introduction However, there is less published on the deposition of chemical

There has been extensive research into air quality in urban

settings (Chan et al., 2000; Jordan, 2005; Lim et al., 2005).

1.(R. Huston).er Ltd. All rights reserved

contaminants from the urban atmosphere, particularly in

Australia. In many cities worldwide drought and population

growth are putting pressure on water supplies. In Australia

.

w a t e r r e s e a r c h 4 3 ( 2 0 0 9 ) 1 6 3 0 – 1 6 4 0 1631

a change in government policy combined with rebates has seen

a large number of urban households installing rainwater tanks.

Tank owners often use the water for drinking even where

treated water is available though it is not advised by water

authorities. The percentage of owners drinking tank water has

been reported as 60% in the Sunshine Coast (Lukin et al., 2005)

and in a recent study in Brisbane it varied with the demo-

graphic being 1%, 15% and 92% for greenfield, retrofit and peri

urban tank owners respectively (Gardiner et al., 2008).

However, roof runoff has been shown to contain elevated

heavy metals such as Pb and Zn with differences noted

between urban, industrial and rural sites (Thomas and Greene,

1993), with the roof often acting as a source of metals (Chang

et al., 2004). Tank water Pb also exceeds Australian Drinking

Water Guidelines (2004) in some cases (Chapman et al., 2006).

Government and water authorities are concerned that urban

and industrial air pollution may adversely affect the water

quality in urban tanks through both wet and dry deposition of

contaminants (CRC for Water Quality and Treatment, 2005;

Gardner et al., 2004). However limited data exists on the rela-

tive contribution of atmospheric deposition. Before control

measures are considered it is necessary to characterise the

input of atmospheric deposition to the chemical water quality

of urban tanks. This paper examines the current atmospheric

deposition of chemicals in a sub-tropical urban environment in

Brisbane, Australia. The deposition of contaminants is

compared with tank water concentrations at 13 sites sampled

at the same time and location. Location effects on fluxes of

deposited contaminants are also examined.

2. Materials and methods

2.1. Local climate and meteorology

Greater Brisbane is a sprawling city of just under 2 million

people (ABS, 2006) in a sub-tropical climate. It is heavily reliant

on cars and trucks with transport estimated to generate 60%

or more of the air pollution (EPA, 2004). It has a domestic and

international airport, shipping port and oil refineries near the

mouth of the Brisbane River and some light industry in several

industrial precincts. The median annual rainfall of 1138 mm is

typically predominately in spring and summer, though the

sampling period had an unusual extended drought followed

by heavy rains toward the end of the sampling. The total

rainfall for the period was 86% of median rainfall for the last

75 years (Bureau of Meteorology, Archerfield station) with 5

out of the 12 months having less than 50% of median rainfall

for that month (see Supplementary information, appendix 1).

Average minimum and maximum temperatures are between

20–30 �C and 10–20 �C for summer and winter respectively and

average humidity ranges from 45 to 72% being lowest in

winter and highest in the summer. Winds are typically a land

breeze from the south–southwest in the mornings and change

in the afternoons to an east–northeast sea breeze (ABM, 2008).

2.2. Sampling

Sampling of wet plus dry atmospheric deposition with

continuously open containers, known as bulk deposition (BD),

was conducted at 12 households and 4 Environmental

Protection Agency (EPA) air pollution monitoring sites on

a monthly basis from April 2007 to March 2008. Sites were

spread across greater Brisbane, Queensland, Australia (Fig. 1).

The samplers were based on the Australian standard for dust

deposition (AS/NZS 3580.10.1, 2003). They consisted of 4 L

amber glass bottles and clear glass funnels (15–18 cm diam-

eter) pre-cleaned in a laboratory dishwasher then soaked in

8% nitric acid for several days and finally rinsed thoroughly

with MilliQ water and air dried. Teflon stoppers were used to

hold the funnels in place and treated the same for cleaning. As

the aim was to mimic the microbial and physical environment

in a tank no antimicrobial agent was used and each bottle was

completely wrapped with aluminium foil to exclude light and

prevent algal growth. Samplers were deployed with clear

surrounding airspace at a height of 2 m in yards behind

private houses or at 4 m for EPA sites. They were deployed for

33 days on average. Funnels were rinsed with 100 mL MilliQ

water prior to removal and sample transport to the laboratory.

Bottles were stored at 4 �C in the dark until processing which

was usually within two weeks.

The total sample volume was determined gravimetri-

cally. As the total solids concentrations averaged <0.04 mg/

mL and did not exceed 0.26 mg/mL there was no adjust-

ment for increased density associated with solids and 1 g

was assumed to equal 1 mL of rainfall. Average daily rain-

fall (mm/d) was calculated by the volume collected (cm3)/

surface area of the funnel (cm2)/number of days deployed

(d)� 10 (mm/cm). Evaporative losses were measured as

10 mL/8 d during March 2008 and estimated as <10% in 88%

of samples (median volume collected¼ 1700 mL). Previous

research has shown BD samplers to correlate well with rain

gauges (Rossini et al., 2005). Tank water was sampled

directly into 4� 5 mL polypropylene tubes (Sarstedt), one

container for each analysis, as close to the tank outlet as

possible and before any filter systems present and where

possible before any pump. Sites were spread across Bris-

bane with 13 locations having both tank water and BD

sampled concurrently.

2.3. Chemical analysis

2.3.1. Total solids analysisTotal solids were determined gravimetrically by difference in

mass after evaporating a well-mixed aliquot of 250–350 mL of

BD sample at 105 �C in a clean dry beaker (Method 2540 B)

(Eaton et al., 2005). Beakers were cooled and stored in a des-

sicator before weighing.

2.3.2. Organic analysisOrganic analysis was undertaken by Queensland Health

Scientific Services (an NATA registered laboratory) which use

a reporting limit (RL) approximately five times the detection

limit of the method. Approximately 1 L of sample was liquid–

liquid extracted with dichloromethane and then analysed by

GC/MS. Surrogates and internal standards were used for

quality control. This organic analysis included 122 herbicides

and pesticides, 17 PAHs and 16 phenolic compounds. Pesti-

cides and herbicides are not listed due to space but the PAHs

and phenolic compounds analysed are presented in Table 1.

Fig. 1 – Bulk Deposition Sampling sites.

w a t e r r e s e a r c h 4 3 ( 2 0 0 9 ) 1 6 3 0 – 1 6 4 01632

2.3.3. Metal analysisMetals analysis (29–30 metals, see Table 4 for list) was based

on US EPA method 200.8 for acid soluble trace elements in

water using Inductively Coupled Plasma-Mass Spectrometer

(ICP-MS). ICP-MS has detection limits 1–2 orders of magnitude

Table 1 – PAHs and phenolics analysed.

PAHs Phenolics

Benzo[g,h,i]perylene Phenol

Dibenz[a,h]anthracene 2-Chlorophenol

Indeno[1,2,3-cd]pyrene 2-Methylphenol

Benzo[e]pyrenea 4-Methylphenol

Benzo[a]pyrene 2-Nitrophenol

Perylenea 2,4-Dimethylphenol

Benzo[bþk]fluorantheneb 2,4-Dichlorophenol

Chrysene 2,6-Dichlorophenol

Benz[a]anthracene 4-Chloro-3-methylphenol

Pyrene 2,4,6-Trichlorophenol

Fluoranthene 2,4,5-Trichlorophenol

Anthracene 2,4-Dinitrophenol

Phenanthrene 4-Nitrophenol

Fluorene 2,3,4,6-Tetrachlorophenol

Acenaphthene 2-Methyl-4,6-dinitrophenol

Acenaphthylene Pentachlorophenol

Naphthalene

Benzo-b-naptho(1,2-d )thiophenea

Cyclopenta[c,d]pyrenea

a Only analysed in tank water samples.

b Analysed as combined as they were not chromatographically

resolved.

lower for most elements analysed compared with many

earlier studies using ICP-optical emission spectrometer or

atomic absorption spectrometer instruments. Water was of

low turbidity so tank water and BD samples were acidified

directly with nitric acid (4.9 ml sampleþ 0.1 ml HNO3) then

0.1 ml of internal standard solution was added to all samples

including calibration standards, blanks and Certified Refer-

ence Material (CRM – TM23.3, lot 305, National Water Research

Institute, Environment Canada). Internal standards used were

Sc, Ge, Y, Rh, Tb, Au at 10 mg/L for all apart from Au which was

2 mg/L. A mixed environmental calibration stock was

purchased (Choice Analytical, Thornleigh, Sydney, NSW, 2120)

to which were added individual standards for Li, Al, Bi and Sr.

The Standards were mixed and diluted in 2% nitric acid to

1000 mg/L then diluted further each month from this stock. An

Agilent 7500cs ICP-MS was used for analysis. Interference

corrections were used for In, Cd, Mo and V and Pb concen-

tration was based on the sum of the counts from all isotopes.

Arsenic is normally corrected for Cl interference, however it

was found to have more reliable values without interference

corrections because of the relatively low chloride concentra-

tions in rainwater. Analysis with and without interference

corrections was run for comparison.

2.3.4. Anion analysisA total of eight soluble anions (F�, Cl�, NO2

�, Br�, NO3�, SO4

�2,

PO4�3 and C2O4

�2) were analysed without prior filtration via Ion

chromatography on a Dionex LC20 instrument. The chroma-

tography consisted of a 2 mm internal diameter AS4A_SC

column with an AG4A-SC guard column and anion self-

regenerating suppressor run at 50 mA. Eluent flow was 0.5 mL/

w a t e r r e s e a r c h 4 3 ( 2 0 0 9 ) 1 6 3 0 – 1 6 4 0 1633

min of 1.8 mM sodium carbonate/1.7 mM sodium bicarbonate.

Electrical conductivity was used for detection and determined

via a Dionex CD-20.

2.3.5. Total organic and inorganic carbon analysisTotal, inorganic and organic carbon were analysed by

combustion-infrared detection with an Elementar liqui TOC

analyser. Organic carbon was obtained by subtraction of

inorganic from total fractions. External calibration of organic

carbon and inorganic carbon fractions used potassium

hydrogen phthalate and sodium carbonate/bicarbonate as

calibration standards.

2.4. Quality control

A BD field blank (capped bottle of milliQ water) was filled and

deployed at one site for the collection period for most months.

One BD sampling was duplicated at a randomly selected site

each month. Laboratory replicates of several tank water and

BD samples were analysed each month. Laboratory blanks

were analysed every 10–20 samples. The method detection

limit (MDL) was defined as meanþ 3� standard deviation

using all laboratory blanks (N¼ 75–91) for the year, after

exclusion of outliers (defined as >3 standard deviations). The

MDL for Na, Mg, Ca and K was 100, 40, 200, 40 mg/L respectively

and 100 mg/L for all anions. Fe and Al had MDLs of 30 mg/L and

5 mg/L respectively while all other elements averaged 0.37 mg/L

(range 0.1–2 mg/L). Median pooled relative standards devia-

tions (RSDs) of replicates were 17.5% (range 3.6–62.7%) and

5.9% (range 0–33.1%) for BD and tank water samples respec-

tively with higher RSDs where most samples were near

detection limits. A Certified Reference Material (CRM) of trace

elements in water was analysed with each analytical run on

the IPC-MS (TM23.3, lot 305, National Water Research Insti-

tute, Environment Canada). In general 95–100% of results over

the year were within two standard deviations of the certified

value for all elements except Fe and Sr. The certified Fe

concentration was below the MDL. The non-certified (indica-

tive) values for other elements also compared well to those

listed in the CRM.

Occasional contamination of the field blank with nitrate

was found and this may indicate insufficient rinsing with

milliQ water, therefore results for nitrate should be inter-

preted with caution. However, the average concentration and

variation of nitrate in BD (1.17� 1.24 mg/L) were comparable

to that in rainwater tanks (1.59� 1.44 mg/L). Rainwater tank

samples were collected directly into polypropylene tubes that

had not been soaked in nitric acid so did not have contami-

nation issues. As field blanks were not open to the atmosphere

there would have been no bacterial activity to consume any

residual nitrate (Dammgen et al., 2005), unlike BD samplers,

and hence values were not corrected using field blanks.

2.5. Data processing

All data values below the MDL were recoded at 1⁄2 the MDL for

calculation of descriptive statistics and flux. One sample

result each for Ni, Cd and Pb and five for V and Cr were

excluded from analysis due to likely contamination after

examination of box plots of log-transformed values and the

robust methods based on the median absolute deviation

detailed in Miller (1993). Some positive bias in average flux

values for F�, PO43�, Br�, C2O4

2� is expected where most

samples were below detection limits. Flux of elements was

calculated using the concentration, volume collected, area of

funnel and number of days deployed to give a value in mg/m2/

d. Mean annual flux was based on the mean of all monthly

fluxes. F�, SO42�, Cl�, Na and Mg fluxes showed a normal

distribution while all other fluxes displayed a log-normal

distribution. Statistical analysis of fluxes was based on the

unchanged data for F�, SO42�, Cl�, Na and Mg and the log value

for all other fluxes (Fowler et al., 1998; Gilbert, 1987). Levene’s

statistic was used for testing homogeneity of variance and

where significant differences existed post hoc analysis used

Tamhane’s T2. All other post hoc analysis used the Tukey test.

Mean and standard deviations of groups are calculated from

the transformed data when used then converted back to

normal (Fowler et al., 1998). Significance level was set at

P< 0.05. Where the majority of samples were below detection

limit the compound was excluded from statistical analysis.

Average results are reported as mean� 1 standard deviation

unless otherwise stated. Methods for reconstructing the total

mass were based on Chan et al. (2000) and references therein.

Briefly the total solids mass was reconstructed from the

analytical results by estimating the mass of crustal matter, sea

salt, ammonium sulfate, organic carbon, smoke, lead bromide

and nitrates. Crustal matter was based on the Al, Fe, Ca and Si

content with Si estimated from Al as it was not analysed

directly. Sea salt was based on Na, ammonium sulfate on

sulfate, soot and organic matter were pooled and assumed to

be all organic matter and based on total organic carbon, smoke

was based on non-soil K and lead bromide the sum of lead

plus bromide. Nitrates were based on direct measurement.

Volume weighed annual mean concentrations were calcu-

lated from the total mass of compound deposited over the

year divided by the total rainfall collected at the site over the

year.

3. Results

3.1. Organic compounds

Of the 155 organic compounds analysed in BD at 16 sites in

December 2006 there were few that were above the parts per

trillion detection limit. Typically only 1 or 2 sites had some

organic compounds detected with concentrations near the

detection limit. As such, the maximum concentration rather

than the mean is shown. With the mass adoption of rainwater

tanks in urban Australia and some people drinking tank water

(Gardiner et al., 2008) concentrations of measured compounds

in BD were compared with the 2004 Australian Drinking Water

Guidelines (ADWG) to assess if there was any potential health

risk (Table 2). For many compounds ADWG have two

concentrations, the first is the guideline level which is based

on instrumental detection limits and the view that the

compound should not be present in drinking water, and

where applicable, a health guideline value (usually much

higher) using the acceptable daily intake (ADI) based on

exposure, dose response and health effects (ADWG, 2004) is

Table 2 – Concentrations of organics above reporting levelin Bulk Deposition samples.

Compounds No.>RL

RL Max.Conc.

ADWG(health)

PAHs 0.01a (BaP)

Pyrene (mg/L) 1 0.01 0.01 10

Fluoranthene (mg/L) 1 0.01 0.01 10

Anthracene (mg/L) 1 0.01 0.039 1

Acenaphthylene (mg/L) 1 0.01 0.014 10

Phenolics (mg/L)

Phenol (mg/L) 2 0.25 0.8 na

4-Methylphenol (mg/L) 1 0.25 0.83 na

2-Nitrophenol (mg/L) 2 0.25 0.57 na

Pentachlorophenol

(mg/L)

1 0.25 0.44 0.01 (10)

Herbicides (mg/L)

Ametryn (mg/L) 1 0.01 0.01 5 (50)

Atrazine (mg/L) 11 0.01 0.03 0.1 (40)

Diuron (mg/L) 5 0.01 0.05 30

Simazine (mg/L) 3 0.01 0.02 0.5 (20)

(#) Levels in brackets refer to the guideline level based on health

criteria. RL¼ reporting limit. na¼ not applicable, i.e. no guideline

set. N¼ 16 sites sampled in Dec 2006.

a ADWG values for PAHs other than BaP are not given but are

calculated here based on toxic equivalency factors relative to BaP

(Nisbet and Lagoy, 1992).

Table 3 – Concentrations of organics above reporting levelin tank water samples.

Compounds No.>RL

RL Max.conc.

ADWG(health)

Phenols

4-Methylphenol (mg/L) 1 0.24 0.7 na

PAHs 0.01a (BaP)

Anthracene (mg/L) 1 0.01 0.013 1

Naphthalene (mg/L) 2 0.01 0.054 10

Herbicides

Diuron (mg/L) 2 0.01 0.79 30

Simazine (mg/L) 1 0.01 0.01 0.5 (20)

Terbutryn (mg/L) 1 0.01 0.01 1 (300)

(#) Levels in brackets refer to the guideline level based on health

criteria. RL¼ reporting limit. na¼ not applicable, i.e. no guideline

set. N¼ 15 tanks sampled in July 2007.

a ADWG values for PAHs other than BaP are not given but are

calculated here based on toxic equivalency factors relative to BaP

(Nisbet and Lagoy, 1992).

Tot

al s

olid

s fl

ux (

mg/

m² /d

)

300

200

100

R² = 0.49

w a t e r r e s e a r c h 4 3 ( 2 0 0 9 ) 1 6 3 0 – 1 6 4 01634

given. For organic compounds the only sample exceeding the

ADWG was for pentachlorophenol and this was still well

below the health guideline, which as stated, is based on actual

health risk. Pentachlorophenol is commonly used as a wood

preservative. There were no obvious local sources. A low level

of herbicides was the most common finding, particularly

atrazine, simazine and diuron in both BD and tanks. Atrazine

is commonly detected at background and urban sites with the

presence at background sites indicating long-range transport

(Majewski et al., 2000).

To compare with organics found in BD, a group of 15 tanks

were also sampled in July 2007 and the water analysed for the

same set of organic compounds with 2 additional PAHs

(cyclopenta[cd]pyrene and benzo[b]naptho[2,1-d]thiophene)

that are markers for petrol and diesel traffic respectively (IPCS,

1996). Even fewer compounds were above detection limits for

the tank water and none above the guideline levels (Table 3).

Based on these results and those of the earlier survey work it

was decided that further analysis of organics not be under-

taken for this project. However, detection of herbicides and

pesticides in deposition is generally greatest during the

application period (Grynkiewicz et al., 2003) so the sampling

period in this project is not sufficient to represent annual

deposition.

Total rainfall collected in BD samplerfor month - expressed as (mm/d)

1210864200

Fig. 2 – Bulk Deposition flux of total solids vs total rainfall

collected for month (expressed as mm/d).

3.2. Inorganics

3.2.1. Total solids flux, concentration, rainfall andreconstructed massThe flux of total solids (TS) increased significantly (P< 0.05,

R2¼ 0.49) with the average daily rainfall for the month in

a linear fashion (see Fig. 2). This is largely due to the increase

of the water-soluble components NaCl, carbon, nitrates and

sulphates adding to the mass of solids deposited with rain

(Table 4). The regression equation suggests a background

deposition flux of 32 mg/m2/d which equates to the average

dry deposition for all seasons and locations. The concentra-

tion of TS decreased exponentially with increasing rainfall

indicating a dilution effect. This is in agreement with other

studies which have found a decrease in concentrations of ions

or heavy metals with increasing rainfall (Alastuey et al., 2001;

Hou et al., 2005). This is because washout (below cloud scav-

enging) is a major mechanism by which contaminants are

incorporated in rainfall (Hou et al., 2005). Most of this washout

occurs with the first few mm of rainfall (Alastuey et al., 2001)

with further rain diluting contaminants already washed out.

Reconstructed mass concentration was significantly

correlated with experimental total solids concentration but

Table 4 – Average flux of measured mass in descending %of total.

Chemical N>

DLMin(mg/

m2/d)

Max(mg/

m2/d)

Mean(mg/

m2/d)

s.d(mg/

m2/d)

% of totalmass

Cl� 173 206.11 22915.47 6507.67 4423.28 21.9

Na 175 202.23 19890.79 5880.36 3588.16 19.8

Organic

carbon

117 212.13 45252.61 5342.65 6211.08 17.9

NO3� 172 22.48 22122.55 2740.85 2636.47 9.2

SO42� 173 146.12 9054.66 2547.51 1420.06 8.6

Inorganic

carbon

112 24.08 15962.85 1480.32 2147.80 5.0

Ca 165 126.91 6899.04 1397.73 1184.09 4.7

K 168 25.38 6101.41 910.95 943.26 3.1

Mg 175 75.39 2400.47 847.34 484.10 2.8

PO43� 74 7.77 15864.16 527.14 1444.36 1.8

NO2� 99 7.77 9603.97 423.43 820.01 1.4

Al 173 4.67 2107.90 310.59 383.89 1.04

Fe 142 16.78 1535.68 275.27 277.20 0.92

F� 39 7.77 570.17 159.85 105.72 0.54

Br� 1 7.77 570.17 156.69 109.13 0.53

C2O42� 0 7.77 570.17 156.06 109.25 0.52

Zn 171 2.97 191.60 45.53 36.32 0.15

Mn 175 2.59 124.30 16.06 18.83 0.054

Sr 170 0.83 47.89 8.55 8.35 0.029

Ba 167 0.41 33.77 7.27 5.35 0.024

Pb 122 0.11 47.13 5.92 7.46 0.020

Cu 120 0.33 25.47 5.52 4.80 0.019

Cr 117 0.11 70.68 1.81 6.08 0.006

Se 14 0.08 5.70 1.76 1.32 0.006

Ni 82 0.12 5.96 1.03 1.01 0.003

As 107 0.06 29.98 0.97 2.46 0.003

V 107 0.17 4.22 0.90 0.78 0.003

Co 79 0.05 7.79 0.72 1.47 0.002

Sb 55 0.02 2.65 0.50 0.47 0.002

Mo 5 0.02 1.71 0.48 0.33 0.002

Li 84 0.04 6.20 0.37 0.55 <0.001

Sn 64 0.01 3.40 0.35 0.44 <0.001

Cd 33 0.01 9.56 0.32 0.99 <0.001

Bi 1 0.03 0.57 0.18 0.11 <0.001

All units in mg/m2/d. N>DL¼ number of samples with concentra-

tions above method detection limit (MDL). Concentrations below

MDL were recoded at 1⁄2 MDL for calculation of flux.

w a t e r r e s e a r c h 4 3 ( 2 0 0 9 ) 1 6 3 0 – 1 6 4 0 1635

this on average only accounted for 32% of the total solids

measured (P< 0.05, R2¼ 0.44). In this study, the Si and soil

concentrations were estimated from the Al and Fe concen-

trations. The silicates in soil require hydrofluoric acid for

digestion (Eaton et al., 2005). Elements such as Fe and Al

incorporated in these minerals may be underestimated in our

analysis due to the incomplete digestion. Conko et al. (2004)

also reported only partial dissolution of crustal elements with

direct acidification of samples. They estimated a 2- to 7-fold

increase in wet deposition using total acid digestion compared

with direct acidification. In this study the low percentage of

total solids mass explained by the reconstructed mass is

probably from an underestimation of crustal matter due to

this. This deduction is supported by the relative mass of the

reconstructed soil fraction in this study being noticeably lower

than other urban aerosol mass closure studies (e.g. 8%

compared to 22% of total mass) (Sillanpaa et al., 2006). There

may also be a minor systematic overestimation in the total

solids determination due to inherent errors in the method

(Eaton et al., 2005).

Additionally comparison of mass reconstruction results

from aerosol samples collected on filters may not be directly

applicable to deposition because of their very different

particle size and composition (Lim et al., 2006). Metals of

crustal origin (Fe, Al, Si) are found mostly in the coarse particle

fraction (>2.5 mm) and can constitute a large part of urban

aerosol while anthropogenic metals are mostly in the fine

particle fraction (Chan et al., 2008; Sillanpaa et al., 2006; Yi

et al., 2006). Though the majority of Cr, Cu, Ni, Pb and Zn mass

in ambient air may be associated with particles<6 mm, the dry

deposition of these metals is dominated by particles >10 mm

(Lim et al., 2006; Sakata and Marumoto, 2004). It is likely that

larger particles also dominate the dry deposition of crustal

metals such as Al, Fe and Si as crustal sources are usually in

the courser aerosol. Particle size analysis of selected BD

samples supports the dominance of larger particles in depo-

sition as the mean modal particle size was 18.5 mm.

The relative importance of dry versus wet deposition to the

overall flux is dependant on the rainfall and analyte, with dry

deposition dominating annual flux in more arid environments

and for some elements such as Cr, As, Mn, V, Cu, Ni Cd and Pb

(Azimi et al., 2003; Sakata et al., 2008). While dry deposition

may be dominated by >10 mm particles, wet deposition has

been calculated to favour finer particle constituents (Kaupp

and McLachlan, 1999). Studies suggest rain scavenges the 2–

10 mm aerosol size range most efficiently followed by the

<0.1 mm while the 0.1–2 mm particles are the least efficiently

scavenged (Zhang and Vet, 2006).

3.2.2. Major and minor components of deposition fluxThe contribution to the flux of all analysed components is

listed in Table 4 in decreasing percentage of total mass ana-

lysed. Sea salt is the major component with organic carbon,

nitrates, sulphates and inorganic carbon cumulatively

explaining 82.4% of the total mass of analysed components.

This is in agreement with urban deposition and aerosol

characteristics of coastal cities which list sea salt, carbon

(elemental or particulate organic matter), sulfate, nitrates and

ammonium ions the dominant compounds (Deboudt et al.,

2004; Sillanpaa et al., 2006). The sea salt flux being significantly

correlated with rainfall (P< 0.01, R2¼ 0.4) is supported by

modelling where dry deposition only accounts for approxi-

mately 30% of the removal of sea salt from the atmosphere

(Henzing et al., 2006). The other major components of flux in

decreasing order are Ca>K>Mg> PO4�3>NO2

�. The presence

of PO43� may be an indication of bird faeces contamination in

the BD samplers (Dammgen et al., 2005). The terrestrial

elements Al and Fe are the greatest in the minor components

accounting for approximately 1% of the analysed mass though

as mentioned are probably underestimated here. The other

significant minor elements in decreasing order are

Zn>Mn> Sr> Ba> Pb>Cu>Cr> Se>Ni similar to a study in

Northern France (Deboudt et al., 2004). All other elements had

an average flux of less than 1 mg/m2/d. Ag, Be, Hg, Th, Tl, U and

C2O42� were also analysed but below the MDL in all samples

and are thus not presented in Table 4.

The fluxes of many of the heavy metals measured in Bris-

bane are comparable to those in other cities as shown in Table

Table 5 – Comparison of fluxes with other cities.

Reference Location As(mg/m2/d)

Cd(mg/m2/d)

Cr(mg/m2/d)

Cu(mg/m2/d)

Pb(mg/m2/d)

Zn(mg/m2/d)

THM(mg/m2/d)

This study Brisbane (BD) 0.97 0.32 1.8 5.5 5.9 45.5 94#

Rossini et al. (2005) Venice (BD) 0.9 0.4 2.7 11.8 9.9 79.5

Sakata et al. (2008) Tokyo Bay (wetþ dry) 7.9 1.1 17.4 44.8 26.9 –

Azimi et al. (2005) Paris (BD) – – – – – – 282.2

Sabin et al. (2005) Los Angeles

(wetþ dry)

– – 1.3 9.3 5.5 39.7

Lim et al. (2006) Los Angeles (dry) – – 4.6 21 19 120

Wu et al. (2006) Taiwan (dry) – – 11.2 21.9 56.0 109.0

BD¼ bulk deposition sample, wetþ dry¼ sum of separate wet and dry deposition samples, dry¼ dry deposition only, THM – Total Heavy

Metals¼ Sum Ba, Cd, Co, Cr, Cu, Ni, Mn, Pb, Sb, Sr, V, Ti and Zn fluxes, # – excluding Ti.

w a t e r r e s e a r c h 4 3 ( 2 0 0 9 ) 1 6 3 0 – 1 6 4 01636

5 and are generally at the lower end of the scale. The study by

Sakata et al. (2008) in Tokyo Bay uses separate wet and dry

deposition samplers, the later using recirculated water, so

may be biased to higher dry deposition rates compared with

other sampling methods (Chu et al., 2008).

3.2.3. Effect of location on flux of metalsThere was a statistically significant effect of location on the

annual mean daily flux of some elements and anions (see

Table 6). Specifically Li, Mn, Fe, Pb and SO42�were significantly

higher in city/heavy traffic/industrial sites compared to outer

suburban sites. Ba, Zn and Cu showed significant differences

in flux between sites in the order of city/heavy traffic/indus-

trial> inner suburban/traffic> outer suburban sites. Mean

daily flux of Sb and Sn was significantly higher in city/heavy

traffic/industrial sites but there was no significant difference

between inner or outer suburbs. Mean daily flux of K was

significantly lower in inner suburban sites compared to city/

Table 6 – Annual mean daily flux of elements at sitecategories.

Compound OuterSuburban

Innersuburban/

traffic

City/heavytraffic/lightindustrial

Mean S.D. Mean S.D. Mean S.D.

K (mg/m2/d) 0.57a,b 2.70 0.43b 2.31 0.71a 3.02

Li (mg/m2/d) 0.21a 2.01 0.23a,b 2.28 0.33b 2.14

Mn (mg/m2/d) 9.08a 2.10 9.60a,b 1.97 14.65b 2.57

Fe (mg/m2/d) 157.1a 2.34 197.2a,b 2.22 255.1b 2.18

Cu (mg/m2/d) 2.69a 2.33 3.86b 2.16 5.91c 2.03

Zn (mg/m2/d) 21.52a 2.06 31.18b 1.69 57.34c 1.95

Sb (mg/m2/d) 0.29a 2.39 0.33a 2.00 0.49b 2.34

Ba (mg/m2/d) 3.35a 2.06 5.48b 1.79 8.58c 2.27

Pb (mg/m2/d) 2.14a 4.08 2.54a,b 3.57 4.18b 3.19

Sn (mg/m2/d) 0.17a 2.49 0.17a 2.71 0.29b 3.10

PO42� (mg/m2/d) 0.19a,b 2.93 0.16a 2.51 0.30b 4.17

SO42� (mg/m2/d) 2.21a 1.30 2.41a,b 1.26 2.95b 1.56

All mean and S.D. values calculated from log normal transformed

data and reconverted to normal values except for SO42� which was

normally distributed and analysed untransformed. All units in mg/

m2/d excluding K, SO42� and PO4

3�which are in mg/m2/d. Significant

differences between groups indicated by superscripts (a, b, c).

high traffic/industrial or outer suburban sites as was the flux

of smoke after mass reconstruction (non-soil K). The mean

daily flux of crustal matter, sea salt and lead bromide using

the reconstructed mass was not significantly different

between site classes. Mean daily ammonium sulfate flux was

significantly higher in the inner city compared to outer sites,

with inner suburban/traffic sites midway between the two but

not significantly different from either. Elevated Zn and Cu in

deposition have been attributed to vehicles in urban envi-

ronments (Conko et al., 2004) and both Zn and Sb have been

proposed as marker elements for motor vehicle exhaust

emissions (Huang et al., 1994). Zn is also a component of tire

wear (Councell et al., 2004). Elevated atmospheric deposition

of heavy metals in the city centre compared to outer areas has

been found by other studies (Azimi et al., 2005). The elevated

zinc and antimony in higher traffic areas point toward the

importance of motor vehicles as a source of contaminants in

deposition.

3.2.4. Concentrations of metals in BD compared to ADWGADWG recommended levels were used as a maximum limit

to assess potential health risk of consuming collected

deposition. It was found that Pb, Cd and Fe concentrations

in BD exceeded the ADWG in 10.3%, 1.7% and 17.7% of

samples respectively. However, this was generally in drier

months when there was little wet deposition and hence no

dilution. This dilution effect is also reflected in the decline

of TS concentrations with increasing rainfall. In an empty

tank the concentrations in rainfall may be significant, but

the volume of water collected during low rainfall periods

would mean it is easily diluted with any water already in

a tank. It is worth mentioning that the Fe guideline is based

on the taste threshold rather than health issues. When the

mean volume weighed concentrations over the year are

examined, the risk from consumption of heavy metals in

water from urban atmospheric deposition is small, as all

sites were below the ADWG. The concentrations of heavy

metals in deposition found in this study are comparable to

others (Table 7). Annual volume weighed means reported

here are lower than the mean or median values used by

some authors due the dilution effect of higher rainfall

periods decreasing the impact of small volumes of concen-

trated deposition.

Table 7 – Mean (±S.D.) annual BD concentrations of heavy metals compared to other urban deposition studies.

Reference/metal Concentration of heavy metals in mg/L

As Cd Cr Cu Ni Pb Zn

Muezzinoglu and Cizmecioglu (2006) a,d – 3.1 (�1.6) 17.2 (�8.6) 19.7 (�25) 7.4 (�2.6) 7.0 (�4.1) 186.4(�225.5)

Conko et al. (2004) a,c,e 0.10 (�0.19) 0.06 (�0.01) 0.17 (�0.09) 0.76 (�1.2) 0.27 (�0.32) 0.47 (�0.55) 4.4 (�3.4)

(Deboudt et al. 2004) a,d – 12.4 (�10) – 89.0 (�120.7) – 580.2 (�600.9) 1425 (�2582.9

This study b,a,e,f 0.3 (�0.3) 0.1 (�0.1) 0.7 (�1.0) 2.0 (�0.9) 0.4 (�0.1) 2.1 (�0.7) 16.4 (�10.1)

a Wet deposition.

b Bulk deposition.

c Annual volume weighed mean.

d Mean concentration.

e Suburban.

f Urban.

w a t e r r e s e a r c h 4 3 ( 2 0 0 9 ) 1 6 3 0 – 1 6 4 0 1637

3.2.5. Concentrations of metal in urban rainwater tankscompared to ADWGThe tank water concentrations demonstrate that tanks will

not always have water meeting the ADWG (2004), particularly

where there are major local sources or other inputs such as

from roof materials. In fact, when tank water concentrations

are examined, Pb and Zn exceed the ADWG in 14.2% and 6.1%

of samples respectively. Of these metals, Pb has the most

potential for serious health effects, particularly where chil-

dren are drinking the water due to the permanent develop-

mental neurological effects (Goyer, 1993). Consumption of Pb

contaminated tank water has been shown to contribute to

elevated blood-Pb levels in children in Port Pirie, a town

affected by lead smelter emissions (Body, 1986). In this study

most samples of tank water had some detectable Pb but the

majority were �2 mg/L (Fig. 3). However the range of concen-

trations exceeding the ADWG was large, with 84.7 mg/L being

the highest concentration of Pb in tank water in this study.

3.2.6. Atmospheric deposition relative to tankwater concentrationsThe relative importance of atmospheric deposition as a source

of heavy metals, particularly Pb, to urban tanks needs to be

Num

ber

of s

ampl

es

250

200

150

100

50

0

Pb concentration (µg/L)

> 2018 - 20

16 - 18

14 - 16

12 - 14

10 - 12

8 - 106 - 8

4 - 62 - 4

<= 2

Aus

tral

ian

Dri

nkin

g W

ater

Gui

delin

e co

ncen

trat

ion

Fig. 3 – Distribution of lead concentration in rainwater tank

samples.

described in order to focus control measures. This was

attempted with a case study of a newly installed tank with

a known history of no overflow during the first 11 months of the

study period. Hence the majority of rainfall during the study

was mixed into the tank with minimal loss, approximating the

volume-weighed concentration in BD at the site. The volume-

weighed concentration was calculated cumulatively for each

month and plotted against the tank water concentration

measured at the same time and location. This cumulative

event mean concentration of Pb in BD compared to the

concentration in tank water at site 1# (Fig. 4). This is a volume

weighed average lead concentration (total deposited lead/total

volume water deposited) in BD at the site at the given time

point. The important point in this diagram is that the BD

concentrations are always less than the tank water concen-

trations. Additionally, analysis of sludge from selected tanks

shows further Pb is contained in the sludge. For example the Pb

concentration in sludge was 184 mg/g compared to a mean

water concentration of 0.5� 0.8 mg/L from the same tank. This

is in agreement with Magyar et al. (2007) who found high

concentrations of heavy metals in sludge of urban tanks. Hence

Pb concentrations in the water represent a fraction of the total

Pb in a tank. The implication for the case study is that there are

major sources of Pb to the tank other than atmospheric depo-

sition. This site had a tile roof with 0.25 m2 of unpainted lead

0

10

20

30

40

50

May

-07

Jun-

07

Jul-

07

Aug

-07

Sep-

07

Oct

-07

Nov

-07

Dec

-07

Jan-

08

Feb-

08

Mar

-08

Dat

esa

mpl

edL

ead

conc

entr

atio

n (µ

g/L

)

BD volume weighed average

Tank water concentration

Fig. 4 – Comparative lead concentrations in tank water

and bulk deposition (cumulative volume weighed mean)

at site 1#.

w a t e r r e s e a r c h 4 3 ( 2 0 0 9 ) 1 6 3 0 – 1 6 4 01638

flashing on the roof catchment supplying the tank and is the

likely source of additional lead in the tank water (Magyar et al.,

2008). This is similar to Rocher et al. (2004) who found increased

Pb flux in runoff from a slate roof with lead flashing compared

to atmospheric deposition at the same site. When the 13 sites

where both tank water and BD were monitored 9 tanks had

a median Pb concentration near the annual volume weighed Pb

concentration in BD. Four tanks had concentrations far

exceeding the BD with three of the four tanks having Pb

flashing on the roof. However, one tank with a high median Pb

concentration did not have Pb flashing on the roof. This tank

was sampled at an unused tap positioned very close to the

bottom and probably had more sludge in the water sample

contributing to the elevated Pb. Apart from lead flashing, old

paint and Pb stabilised PVC drain pipes are other potential

sources of Pb (Al-Malack, 2001; Lasheen et al., 2008; Weiss et al.,

2006).

4. Conclusion

This study demonstrates atmospheric deposition does

contribute to contaminants in rainwater in an urban envi-

ronment. It shows that there is an increase in the

contaminant flux in traffic/industrial areas compared to

outer suburbs with marker elements implicating traffic as

a major contributor. Rainwater collected in urban areas

where air pollution is significant must consider the impact

of pollution on the water quality. Despite the measurable

effect of urban activity on contaminant flux, for a sub-

tropical city of nearly 2 million people the chemical water

quality of urban rainwater over annual time periods could

still be considered as potable. However, the quality of water

collected in a tank may not reflect that of the rainwater,

with Pb exceeding drinking water guidelines most

commonly. This is due to input of contaminants from other

sources such as roof materials. A probabilistic health risk

using the distribution of Pb concentrations in tank water

coupled with tank owner’s consumption patterns is needed

to assess if there is a likely impact on the health of the

general population. In this study atmospheric deposition is

not the major source of Pb in tanks with high concentra-

tions as indicated by comparison with the annual volume

weighed concentrations in rainfall collected at the same

sites. The exact source of this lead in tank water is not

proven in this study. Lead flashing is potentially the source

in the case study shown. The application of multivariate

receptor modelling tools and Pb isotope ratios to identify

and quantify the sources of Pb in tank water is currently

underway. Identification of the source(s) of Pb in tank water

is necessary for targeting control measures for an otherwise

good quality water source. Lastly, the impact of Pb in sludge

and the partitioning between sludge and the water column

needs further study to assess the usefulness of removing

sludge for decontamination. A device that discards the

initial runoff from the roof (first flush device) may reduce

sludge build up and improve water quality somewhat for

particulate Pb but is unlikely to result in sufficient reduction

of soluble Pb (Gardner et al., 2004).

Acknowledgments

This study was supported by the CRC for Water Quality and

Treatment, a Smart State grant from the Queensland

Government and The National Research Centre for Envi-

ronmental Toxicology. We would like to thank the

Queensland EPA for use of their air monitoring stations for

sampling.

Supplementary data

Supplementary data associated with this article can be found,

in the online version, at doi:10.1016/j.watres.2008.12.045.

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