Practical Project - Carolyn Sonter

Assessment of lead and zinc levels of sediments inCockle Creek - New South Wales, Australia

IntroductionCockle Creek in New South Wales (NSW), Australia, flows into Lake Macquarie (Fig 1) and

is of significance in the investigation of lead and zinc levels in sediments due to its close

proximity to a now discontinued lead and zinc smelter. Constructed in 1897 the Pasminco

Cockle Creek Smelter (PCCS) was a major lead processing plant until its closure in late

2003. During the smelter’s operation, stack and fugitive emissions and dust from ore and

slag covered an area extending to Glendale in the north, Macquarie Hills in the east,

Speers Point in the south with the adjoining suburbs of Boolaroo and Argenton to the west

receiving the greatest contamination (NSW Health Department 1991). Cockle Creek flows

through the suburbs of Argenton and Boolaroo before entering Lake Macquarie (Fig 1).

Creeks act as contamination ‘sinks’ due to the fine silt and clay component which is washed

into creeks during rain events from run off thus making the creek sediments an accurate

indicator of the persistence of contaminants in an area (Encyclopedia of Water Science

2005).

Fig 1. Map of Pasminco Cockle Creek Smelter and Cockle Creek (NSW), showing the

geographical relationship to the surrounding suburbs and Lake Macquarie (Willmore

et al. 2006).

Cockle Creek

Lead (Pb) is a metal, bluish grey in colour and found in the earth’s crust in small amounts

usually in ore which also contains zinc, silver and copper (Geoscience Australia 2014).

Lead may take several forms depending on the pH, salinity and humic content of the

medium (Agency for Toxic Substances and Disease Registry 2014). Exposure to Pb can

occur from the inhalation or ingestion of lead dust, particles or exhaust emissions from lead

being burnt (Australian Government Department of the Environment 2014). Lead is found in

air, water and soil in a range of compounds with the bioavailability and persistence largely

determined by the compound formed, with organic lead the most toxic (Alloway and Ayres

1997). The health effects of exposure to Pb can be both acute and chronic (Australian

Government Department of the Environment 2014). In children, exposure to Pb can result

in reduced intelligence, slowed growth and hearing problems while in adults, increased

blood pressure, brain and kidney damage and damage to the reproductive organs is

common (Agency for Toxic Substances and Disease Registry 2014).

Zinc (Zn) is a relatively abundant bluish-white, lustrous, diamagnetic metal, often found in

association with other base metals such as lead, silver and copper (Geoscience Australia

2014). Zinc may take several forms depending on the pH of the medium and temperature

with acidic conditions increasing availability. Due to an electrochemical reaction known as

galvanic action, Zn is commonly used as an anti-corrosion coating in the construction,

transport and appliance manufacturing industries (Geoscience Australia 2014). Zinc is also

used to create alloys such as bronze, pigments, salts, oxide additives to rubber and in

fertilizers (Geoscience Australia 2014). While Zn is a mineral essential for human, animal

and plant health, the absorption of excessive Zn in humans results in Iron (Fe) and Copper

(Cu) deficiencies which cease with a reduction in exposure (Harmaza & Slobozhanina

2014; Department of Human Services 1997). Excess Zn in soil water results in plants

exhibiting Phosphorous (P) and Fe deficiencies and eventual death if exposure is not

reduced (Reichman 2002).

A 1973 survey of ceiling dust, room dust and soil in Boolaroo and Argenton revealed that

Pb levels ranged from 2759-30,764 parts per million (ppm), 23-35,870 ppm and 8-26,794

ppm respectively (NSW Health Department 1991). As Zn was not a focus of the 1973

survey, no information is provided by the 1973 survey. The Australian guidelines for the

assessment of contaminated sites recommend further investigation if soil levels are above

300 ppm (former Standing Council on Environment and Water 2014). Information regarding

if the sediments of Cockle Creek were tested at this time is not available. Since 1973

regular testing has occurred in the suburbs surrounding the PCCS largely related to a Lead

Abatement Strategy (LAS) which was developed in conjunction with Department of

Environment, Climate Change and Water New South Wales and Lake Macquarie City

Council Health in response to the high levels found in humans and soil (Pasminco 2014).

The LAS concluded in February 2013. Kim, Owens and Naidu (2009) conducted an

independent heavy metal distribution, bioaccessibility and phytoavailability study of the

suburbs considered contaminated and others further afield. Lead levels of between 79

mg/Kg and 58,000 mg/Kg were found in the suburbs previously tested in 1973 and levels

between 8 mg/Kg and 235 mg/Kg were found in those areas outside of the 1973 test area

(Kim et al. 2009). Zinc levels of between 310 mg/Kg and 90,000 mg/Kg were found in the

suburbs tested for Pb in 1973 and levels of between 5 mg/Kg and 660 mg/Kg were found

outside of the 1973 Pb test area (Kim et al. 2009).

The NSW Department of Public Works and Services conducted a study in 2002 which

involved the testing of Pb and Zn levels from sediment cores taken from 21 sites

surrounding PCCS, including Cockle Creek, Cockle Bay and Lake Macquarie. That study

provided Pb levels of 326 to 1360 mg/kg and Zn levels of 1003 to 2700 mg/kg (NSW

Department of Public Works and Services 2002) which are in excess of the Australian

guidelines (former Standing Council on Environment and Water 2014). Chariton, Maher

and Roach (2011) tested sediment pore water from Cockle Bay in Lake Macquarie. Their

results indicated Pb of 260 mg/kg and Zn of 550 mg/Kg, however, these levels do not

indicate the Pb and Zn level of the sediment particles but rather the Pb and Zn available for

extraction by water from the sediment (Chariton et al. 2011).

The proposed study will test the Pb and Zn levels in sediment cores from five sites in

Cockle Creek. Testing will be performed upstream from PCCS and the remainder at evenly

distributed points between PCCS and Cockle Bay. It is expected that the Pb and Zn results

will be consistent with results of the studies performed by the NSW Department of Public

Works and Services (2002), Kim, Owens and Naidu in 2009 and Chariton, Maher and

Roach in 2011.

Methods

Sampling site and procedureSamples were collected from five sites, upstream from (Site 1 (control site)), level with (Site

2) and downstream from (Sites 3, 4 and 5) the smelter site (Figure 2). Sampling was

performed by the author and an assistant during clear weather on Sunday 27 July 2014,

between 1.00 pm to 3.00 pm. Each sample was collected at least 100 cm from the bank

and from submerged sediments. When collecting the sampler would walk into the creek,

find a location free of rocks and thrust the sediment core sampler into the creek bed until

the sampler reached an impenetrable surface. After excess water was allowed to drain from

the sediment core sampler, the sampler was opened and the sediment core was halved

using a stainless steel trowel with the upper and lower halves placed in a labelled plastic

collection containers. On collection samples were immediately placed in an esky with

icebricks for transportation to refridgeration where they were stored until analysis.

Fig 2. Map showing the location of sample collection for the testing of Pb and Zn levels from sediments of Cockle Creek, NSW (Google Maps 2014).

GPS coordinates and general site details were recorded for each site (Appendix A, Table

1). All equipment was decontaminated prior to collection at the first site and after collection

at each site by rinsing any visible debris from the equipment with creek water, then rinsing

with Decon 90 followed by rinsing with distilled water. One field and two rinsate blanks were

taken during collection.

1

2

3

4

5

Sample preparation for analysisSamples were kept refridgerated for a period of one week prior to processing for analysis.

To ensure analysis of a representative sample the contents of each of the ten samples

collected were mixed prior to sample removal and weighing.

To prepare samples for analysis by x-ray fluorescence spectroscopy, approximately 10

grams of each sediment sample was measured into labelled beakers and oven dried at

110oC (Figure 3) for a period of one week.

Fig 3. Oven drying of sediment samples.

Following dessication large debris was removed and each sample ground to a fine powder

by mortar and pestle (Figure 4).

Fig 4. Grinding of oven dried soil.

Labelled x-ray cannisters (Figure 5) were filled with sufficient sample to cover the bottom of

the cannister for analysis.

Fig 5. Sediment samples in x-ray canisters

ready for analysis.

For analysis by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES),

approximately 10 grams of each sediment sample was measured into labelled beakers for

digestion (Figure 6).

Fig 6. Weighed sediment samples ready for

digestion.

Additions of 5 mL each of concentrated nitric acid and concentrated hydrochloric acid were

made to each sample. Beakers were covered with watchglasses and placed on a hotplate

and boiled approximately 18 hours (Figure 7). During the digestion process further additions

were made of nitric and hydrochloric acid and of concentrated hydrogen peroxide. Each

hour the condensation on the watchglasses were rinsed into the beakers using distilled

water. Sulfuric acid (18 M) was added to samples from Site 4 to digest the remaining

organic matter.

Fig 7. Digestion of samples on a hotplate.

Following digestion the samples were cooled and then filtered through 45 filter paper to

remove sediment (Figure 8).

Fig 8. Filtering of sediment from samples.

To ensure all sediment was removed from the samples they were vacuum filtered through

Millepore (Figure 9).

Fig 9. Vacuum filtering samples through

Millepore.

Following filtering, samples were placed into volumetric flasks and made up to 100ml with

distilled water (Figure 10). Standards of 1 mg/L, 10 mg/L and 100 mg/L of Pb and Zn were

prepared from 1000 mg/L Pb and 1000 mg/L Zn (Figure 10) and analysed to obtain the

standard curve of absorbancy.

Fig 10. Standards of 1 mg/L, 10 mg/L and

100 mg/L of Pb and Zn in the

foreground with filtered samples

ready for ICP analysis.

Sample analysis

X-ray fluorescence analysis of oven dried sediment was performed on an X-ray MiniPal4

PANalytical (Figure 11).

Fig 11. Sediment prepared for x-ray

analysis.

ICP analysis of the digested sediment samples and Pb and Zn standards was performed on

a Varian Liberty AX Sequential ICP-AES (Figure 12).

Fig 12. ICP analysis of sediment samples

and Pb and Zn standards.

Data AnalysisData obtained from the analysis of the samples by x-ray fluorescence was initially reviewed

to determine the presence and identity of metals. As x-ray fluorescence is a quantitative

rather than qualitative analysis tool the presence of each element identified can only be

reported as present and it’s quantity in relation to the other elements present.

Data obtained from analysis of the standards by ICP was entered into an excel spreadsheet

and graphed to find the standard curve. The absorbancy equation obtained for Pb: y =

1350.1x - 580.85 (R2 = 1) and for Zn: y = 9562x - 53963 (R2 = 0.9924). Following analysis of

the sediment samples, this equation was used to determine the concentration of Pb and Zn

and the results calculated (Appendix B, Table 1) and graphed in Excel (Figures 13 and 14).

ResultsAnalysis by x-ray fluorescence indicates that the number of elements present in the

sediments increased in both number and readable amount with the progression of the creek

from Site 1 to Site 5 (Appendix B, Figures 1 to 10). The elements identified are displayed in

Table 1.

Table 1. Elements identified in Cockle Creek sediments.

Element Site 1 Site 2 Site 3 Site 4 Site 5B T B T B T B T B T

Al

Br

Ca

Cr

Cu

Fe

K

Mn

Mo

S

Sc

Si

Sr

Ti

V

Zn

B: Bottom of sediment coreT: Top of sediment core: Element not present: Element present

No Pb was detected by x-ray fluorescence spectroscopy in any of the samples.

Analysis by ICP of Pb concentration indicates that on average higher levels were retained

in the deeper sediments of Cockle Creek (Figure 13). The mean concentrations of Pb found

cores were 284.68 mg/kg in the bottom half of the sediment cores and 226.12 mg/kg in the

top half of the sediment cores.

1 2 3 4 50

100

200

300

400

500

600

700

800

900

BottomTop

Site

Pb m

g/kg

Fig 13. Concentration of Pb found in sediment of Cockle Creek, NSW, as determined by

ICP analysis.

Analysis by ICP of Zn concentration indicates that on average higher levels were retained in

the deeper sediments of Cockle Creek (Figure 14). The mean concentrations of Zn found

cores were 683.86 mg/kg in the bottom half of the sediment cores and 587.96 mg/kg in the

top half of the sediment cores.

1 2 3 4 50

100200300400500600700800900

1000

BottomTop

Site

Zn m

g/kg

Fig 14. Concentration of Zn found in sediment of Cockle Creek, NSW, as determined by

ICP analysis.

Differences were also found in the concentration of Pb and Zn between sites. From the

samples taken, Sites 1, 2, 3 and 4 contained Pb concentrations below the 600 mg/kg

Health Investigation Level (HIL) maximum recommended by National Environment

Protection Measures (NEPM) 2013 for open space areas (Appendix C, Table 1). Lead

concentration of the sediment in the top half of the core sample taken from Site 5 was

below the NEPM HILs, however sediment in the bottom half of the core exceeded the

NEPM HILs at 848.31 mg/kg. Zinc levels across all sites were within the maximum NEPM

HILs with Site 3 providing the lowest concentration and Site 4 the highest.

DiscussionThe aim of this study was to determine if Pb and Zn concentrations in Cockle Creek are

consistent with the results of the studies performed by the NSW Department of Public

Works and Services (2002), Kim, Owens and Naidu in 2009 and Chariton, Maher and

Roach in 2011. As expected our study found that sediments analysed by ICP-AES

displayed the lowest Pb levels at Site 1 (control site) and highest at Site 5. The variation

found at Sites 2, 3 and 4 could be due to the thickness of the riparian vegetation trapping

sediments prior to entry to the creek, the side of the creek sampled in relation to creek flow

and the taking of one sediment core only from each site. However, while zinc levels did not

exceed the NEPM HILs at any of the sites, Site 3 provided the lowest concentrations and

Site 4 the highest. The reasons for this variation could be similar to the findings for Pb such

as riparian vegetation, the side of the creek sampled and the taking of one sediment core

from each site.

Analysis by x-ray fluorescence spectroscopy did not provide results consistent with

previous studies or the results of this study from ICP-AES analysis with regards to Pb

levels. This inconsistency may be due to the amount of energy employed during x-ray

analysis or the broadness of the spectrum used. A different result may have been obtained

if the x-ray analysis was repeated with a spectrum specific to Pb at a higher energy level.

Of note is the variation in sampling that occurred between this study and previous studies.

The NSW Department of Public Works and Services did not conduct sampling but drew

from previous studies which had utilised a range of sampling techniques at a range of

locations. Kim, Owens and Naidu (2009) collected surface soil samples while Chariton,

Maher and Roach (2011) collected the top 10 cm of creek sediment from Cockle Creek

which they considered representative of sediment deposition over the past 15-20 years.

This study collected sediment samples to a depth of 25 cm at Sites 1, 2 and 3 and to a

depth of 50 cm at Sites 4 and 5. At each site the corer was sunk to the deepest depth

permitted by the underlying bedrock. This method was considered appropriate due to the

underlying bedrock restricting the depth of the sediment profile.

However, overall the study results are consistent with previous studies when considered in

context with the sampling locations and methods. The NSW Department of Public Works

and Services refers to the Pb and Zn concentrations in sediments taken from Cockle Creek.

While it is not known the exact location or the depth of sampling and the levels reported,

are greater than our study obtained, the studies referred to were conducted between 1982

and 2001.

Of the locations sampled by Kim, Owens and Naidu (2009), two were closely located to the

creek sediments collected in this study. Surface soil collected upstream from Site 4 and 5 of

this study, provided Pb concentration levels that were much higher than the NEPM HILs.

Creek sediments collected from Site 4 were close to the maximum NEPM HILs permitted

for residential use with soil access but below the levels permitted for open area use. The

top of the sediment core for Site 5 was within the maximum NEPM HILs permitted for open

area use but would have exceeded the levels for residential use with soil access if it had

still been surface soil. Of note is the high level of Pb found in the bottom of the sediment

core for Site 5 which exceeded both the maximum NEPM HILs permitted for open area use

and residential use with soil access.

Chariton, Maher and Roach (2011) sampled sediment from Cockle Bay which is the inlet

area where Cockle Creek flows into Lake Macquarie, close to Site 5 of our study. The high

results obtained in our study may have two explanations. Sampling in the 2011 study may

have occurred further into the lake where the sediment from the creek may have been

deposited over a greater area and so was thinner at any one point, thus providing a lower

concentration per kg of sediment. Secondly, the sediment core collected was to a depth of

50 cm and does not appear to have been mixed prior to analysis which could potentially

result in only the top of the core being tested. With the expected rate of deposition into lake

Macquarie being between 1 to 7 mm per year (Hollins et al. 2011), the sediments tested

may have been deposited after the smelter closed.

Sediment deposition rate explains the higher concentration of Pb and Zn in the bottom half

of almost all of the sediment cores across Sites 2, 3, 4 and 5. Riparian vegetation reduced

at each site which would explain the reduction in sediment with the progression of the creek

towards Lake Macquarie. It is likely that the bottom half of the sediment cores represent

deposition from over 25 years ago (Hollins et al. 2011), prior to a reduction in contaminants

released by the smelter. As the top half of the sediment cores contained lower levels of Pb

and Zn it would appear that less contaminated sediments have entered Cockle Creek in the

past 25 years.

ConclusionOur results are consistent with previous studies and with what would be expected eleven

years after the smelter ceased operation. While Pb levels are in excess of the NEPL HILs

for open space in the bottom half of the sediment core from Site 5, it is unlikely that the Pb

is bioaccessible unless the deep creek sediments are dredged or the creek develops an

acidic environment. However, without any further addition of contaminants and or

disturbance of the creekbed, Cockle Creek can be considered environmentally safe and

stable after 106 years of contamination.

Appendix A

Table 1. Site specific information for sampling of sediments from Cockle Creek, NSW.

Site 1(control site)The Weir Rd

Bridge, Barnsley

Site 2Northern end of Racecourse Rd,

Teralba

Site 3Raceourse Rd,

Teralba

Site 4Creek Reserve Road, Boolaroo

Site 5Speers Point Park

at junction of Cockle Creek and Lake Macquarie

GPS Coordinates 32o56’7” 151o35’44” 32o58’38” 151o32’27” 32o57’11” 151o37’1” 32o57’11” 151o37’1” 32o58’1” 151o36’48”

Distance from bank 200 cm 100 cm 150 cm 200 cm 250 cm

Water flow rate Slow Medium Medium Medium Medium

Depth of sample 25 cm 25 cm 25 cm 50 cm 50 cm

Sample colour Black Black Black Black Black

Sample texture Clayey fine gravel Fine clay Fine clay Fine silty clay with some pebbles

Sandy with large pebbles

Sample odour Strong sulfur Sulfurous and oily Slightly sulfurous Slightly sulfurous None

Riparian vegetation Thick vegetation of river ash, she oaks and sedges

Mangroves, grasses and reeds approx 2 metres thick along creek bank

Mangroves, she oaks, reeds and grasses approx 2 metres thick along creek bank

Mangroves, reeds and grasses approx 2 metres thick along creek bank

Grass

Features of site Inside curve of eastern bank

Near railway line Close to Lucky’s Scrap Metals

Across from the Five Islands

Inner edge of peninsula

Appendix B

Fig 1. X-ray fluorescence analysis of the bottom of the sediment core from Site 1.

Fig 2. X-ray fluorescence analysis of the top of the sediment core from Site 1.

Fig 3. X-ray fluorescence analysis of the bottom of the sediment core from Site 2.

Fig 4. X-ray fluorescence analysis of the top of the sediment core from Site 2.

Fig 5. X-ray fluorescence analysis of the bottom of the sediment core from Site 3.

.

Fig 6. X-ray fluorescence analysis of the top of the sediment core from Site 3.

Fig 7. X-ray fluorescence analysis of the bottom of the sediment core from Site 4.

Fig 8. X-ray fluorescence analysis of the top of the sediment core from Site 4.

Fig 9. X-ray fluorescence analysis of the bottom of the sediment core from Site 5.

Fig 10. X-ray fluorescence analysis of the top of the sediment core from Site 5.

Appendix C

Table 1. Absorbancies obtained by ICP analysis with conversion to mg/Kg

Sample Zn absorb Pb absorbZn conc

mg/100 mLPb conc

mg/100 mL Soil wght (gm) Zn mg/Kg Pb mg/Kg

1B 671027 6626.24 64.53294 5.33819 11.204 575.9813 47.64539

1T 871699 11304.4 85.51935 8.803237 11.5106 742.9617 76.47939

2B 887375 34780.5 87.15875 26.19165 11.0551 788.4031 236.9192

2T 692406 15637.9 66.76877 12.013 10.8507 615.3407 110.7117

3B 505610 11987.6 47.23353 9.309273 11.864 398.1248 78.46657

3T 150163 2535.2 10.06066 2.308014 10.0911 99.69832 22.87178

4B 906097 28974.4 89.11671 21.89116 10.3231 863.2747 212.0599

4T 968724 52697 95.66628 39.46215 11.271 848.7826 350.1211

5B 940183 133190 92.68145 99.08218 11.68 793.5055 848.3063

5T 765444 89942 74.40713 67.049 11.7544 633.0151 570.4162

Appendix D

Table 1. Health Investigation values in mg kg-1 for soil from NEPM 2013

Substance

Health Investigation Levels

values in mg kg-1

A B C D

Arsenic2 100 500 300 3 000

Beryllium 60 90 90 500

Boron 4500 40 000 20 000 300 000

Cadmium 20 150 90 900

Chromium (VI) 100 500 300 3600

Cobalt 100 600 300 4000

Copper 6000 30 000 17 000 240 000

Lead3 300 1200 600 1 500

Manganese 3800 14 000 19 000 60 000

Mercury (inorganic)5 40 120 80 730

Methyl mercury4 10 30 13 180

Nickel 400 1200 1200 6 000

Selenium 200 1400 700 10 000

Zinc 7400 60 000 30 000 400 000

Cyanide (free) 250 300 240 1 500

A Residential use with garden/accessible soil

B Residential with minimal opportunities for soil access

C Parks, recreational open space and playing fields

D Commercial/industrial use

(Australian Government ComLaw 2013)

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