Oil & Chemical Pollution 6 (1990) 81-90
Petroleum Hydrocarbon Pollution of Lake Burley Griffin
W. M a h e r , C. T o m l i n s & J. F u r l o n g e r Water Research Center, Canberra College of Advanced Education, PO Box 1, Belconnen0 ACT 2616, Australia (Received 22 August 1988; accepted 25 October 1988)
ABSTRACT Aromatic hydrocarbons were measured in Lake Burley Griffin by fluorescence spectroscopy to gain an estimate of the pollution of the lake by petroleum hydrocarbons. Aromatic hydrocarbons are reported as equivalents of m-terphenyl (T) and chrysene (C). Observed concentrations are 0.3-2.2 pg/litre (T) and 0.1-0.5 pg/litre (C). Widespread distribution of fuel distillates is evident with only a small contribution from lubricating and heavier oils.
1 INTRODUCTION Pollution of aquatic environments by petroleum hydrocarbons is of concern as it is recognized that low level hydrocarbon inputs may have long-term ecological effects (Steele, 1977; H a n n a h et al., 1982; Cowles & Remillard, 1983) even in the absence of acute immediate detrimental effects (Connell & Miller, 1980). The presence of aromatic hydrocarbons in water samples provides a marker of petroleum hydrocarbon pollution as all oils contain aromatic hydrocarbons while few, if any, biogenic aromatic hydrocarbons are produced in aquatic environments (Hase &Hites, 1976; Neff, 1979). This study uses fluorescence spectroscopy to obtain an estimate of the aromatic hydrocarbon concentrations (and hence an estimate of the petroleum contamination) in Lake Burley Griffin, a lake that serves as a recreational focus for Canberra, the Australian National Capital. 81 Oil & Chemical Pollution 0269-8579/90/$03.50 © 1990 Elsevier Science Publishers Ltd, England. Printed in Ireland.
82
w. Maher, C Tomlins, J. Furlonger
2 STUDY AREA AND SAMPLE LOCATIONS Lake Burley Griffin was created in 1964 by the construction of the Scrivener Dam across the Molonglo River. The lake has a surface area of 704.2 ha, an average depth of 4.71 m (maximum depth 14.7 m) and a mean retention time of 0-13 years. The catchment area of the lake is 186 500 ha and the land use is about 3% urban, 76% agricultural and 31% native forests. Urban development is centred on the lake with approximately 250 000 people living in the catchment area. Upstream, secondary treated sewage effluent from another city, Queanbeyan (population 20 000), enters the river draining into the lake. The locations of sampling stations are shown in Fig. 1. Sample sites on the perimeter of the lake correspond to inflows from storm water drains. A water sample was also collected from Lee's Creek, an upland stream draining an undisturbed forest catchment near Canberra. This water sample was used to give an indication of natural background levels.
3 MATERIALS AND METHODS
3.1 Equipment All fluorescence measurements were made with a Hitachi F-4000 spectrofluorimeter with 1 cm quartz cells.
3.2 Reagents All solvents were HPLC grade. Stock solution of m-terphenyl and chrysene (200 ~g/ml) were prepared by dissolving these compounds in n-hexane. Aliquots of these solutions were diluted when required with n-hexane. Microparticulate separatory columns (Sep-pak C 18 and silica) were obtained from Waters Associates. Water used was deionized, distilled and hydrocarbon filtered using a Barnstead/Nanopure water purification system.
3.3 Preparation of equipment Glassware and utensils were soaked in 6% V/V Decon 90 for 24 h, rinsed in distilled water and soaked for a further 24 h in dilute chromic acid. After rinsing five times with distilled water and drying in an oven (110°C) all items were rinsed with n-hexane and allowed to air dry. Used items were soaked in ethanol before washing with detergent.
Petroleum hydrocarbon pollution of Lake Burley Griffin
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W. Maher, C. Tomlins, J. Furlonger
3.4 Sample collection Water samples were taken at a depth of 0.5 m, and 2. 5 litres were collected in 4 min. The sampler, specially constructed to collect water at the depth required and to exclude contact with any other water, consists of a Teflon inlet valve mounted on a 2.5-1itre glass Winchester held in a stainless steel cradle. Water samples that were not analysed within 24 h were acidified to pH 2-3 with sulphuric acid and stored at 4°C. Samples were neutralized with 30% W/V sodium hydroxide before filtering (German Chemists Association, 1981).
3.5 Analysis One-litre subsamples of water were filtered through hexane-rinsed Millipore glass fibre filters (0.3/2m) in an all-glass Millipore filtration apparatus. The hydrocarbons in the filtrate are described as 'dissolved' and the hydrocarbons retained on the filter as 'particulate'. Dissolved aromatic hydrocarbons were concentrated from water samples by passing 1 litre of water through a silica and a C18 Sep-pak (pre-washed with methanol (3 ml) and water (5 ml) in tandem using suction (Fisher et al., 1987). The silica cartridges were discarded and the C18 cartridges washed with water (3 ml) and the aromatic hydrocarbons eluted with dichloromethane (5 ml). About 0.1 ml of hexane was added to the extracts and the dichloromethane removed by evaporation to near dryness using a stream of nitrogen. The final volume was adjusted to 5 ml with n-hexane and extracts dried over anhydrous sodium sulphate. Recoveries of dissolved aromatic hydrocarbons through the analytical procedure estimated by additions of 5/~g of m-terphenyl and chrysene to filtered aliquots of lake water were 81 + 11% (n = 5) and 83 + 9% (n = 5) respectively. Filters were extracted with 20 ml ofn-hexane with ultrasonic treatment for 20 min. The extracts were concentrated to less than 5 ml by evaporation using a stream of nitrogen and, after adjusting the volume to 5 ml with n-hexane, dried over anhydrous sodium sulphate. The aromatic hydrocarbon contents of the extracts were estimated by fluorescence emission measurements. Solutions were excited at 300 nm and the fluorescence intensity emission measured at 330 and 380 nm. The results are reported as concentration equivalents ofm-terphenyl (T) and chrysene (C). Standard solutions of the compounds in n-hexane were run with each batch of samples and were quantified by comparison of peak heights of standards and samples. The fluorescence emission intensities of impurities in the reagents were measured as the blank.
Petroleum hydrocarbon pollution of Lake Burley Griffin
85
To identify the probable source of aromatic hydrocarbon inputs to these waters, synchronous scanning of excitation and emission wavelengths was used with the direct excitation mode. The excitation and emission wavelengths were offset by 25 nm, both slit widths were set at 5 nm and the emission spectrum from 265 to 450 nm recorded. The synchronous fluorescence emission spectra obtained were compared with those of reference materials (Fig. 2) and the most likely source assigned.
4 RESULTS A N D DISCUSSION 4.1 Fluorescence spectroscopy The fluorescence emission spectra of several crude oils and refined oils have been examined in previous studies (Maher, 1983; Smith & Maher, 1984) to determine whether they had any common features. The results showed that there were two broad groups: (1) oils with fluorescence arising predominantly from two- and three-ringed aromatic hydrocarbons with an emission m a x i m u m near 330 nm and (2) oils containing
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300
400
500
W a v e L e n g t h (nm)
Fig. 2. Synchronous fluorescence emission spectra of reference materials. (a) Arabian crude oil, (b) Gippsland crude oil, (c) outboard engine fuel and diesel fuel, (d) lubricating oil. From Smith & Maher (1984).
86
vv Maher, C. Tomlins, J. Furlonger
aromatic hydrocarbons with three or more rings with a fluorescence emission maximum near 380 nm. It was considered appropriate to report results based on a fluorescence emission of 330 and 380 nm. Reference materials used were m-terphenyl with a fluorescence maximum at 330 nm and chrysene with a fluorescence maximum at 380 nm. The measurement of fluorescence intensity of sample extracts at two wavelengths allows the estimation of the presence of oil products based on distillate (petrol and diesel fuels) and lubricating oils. 4.1.1 Synchronous
Synchronous fluorescence emission spectra of extracts were used to assign possible sources of petroleum contamination (Lloyd, 1971; Wakeham, 1977; Smith & Maher, 1984; Maher, 1985). Three major sources are identifiable (Fig. 2): (1) fuel-distillates including gasoline and diesel fuel, with a synchronous fluorescence peak at 300 nm; (2) lube-refined products including lubricating oil with a fluorescence peak at 340 nm; (3) crude-lube oils with significant fluorescence at wavelengths of 380 nm and greater.
4.2 Petroleum hydrocarbons in Lake Burley Griffin Concentrations of aromatic hydrocarbons in sample extracts, expressed as equivalent concentrations ofm-terphenyl and chrysene, and probable sources are given in Table 1. The concentrations of dissolved and particulate aromatic hydrocarbons were up to an order of magnitude higher than those found in Lee's Creek, a creek draining an undisturbed forested catchment. The highest concentration of dissolved and particulate aromatic hydrocarbons were found in a water sample taken at a lagoon connected to Lake Burley Griffin (sample location 7). This lagoon serves as a settling trap and would account for the higher particulate aromatic hydrocarbon values. In most samples particulate aromatic hydrocarbons were low. As samples were collected in a period of low rainfall, it is expected that a high rainfall storm event would significantly increase the particulate matter and hence aromatic hydrocarbons in Lake Burley Griffin by flushing out particulate material accumulated within storm water drains. The higher levels of dissolved aromatic hydrocarbons at sample location 7 in relation to other locations is not readily explained. No point sources of petroleum hydrocarbons are evident and it can only be postulated that particulate matter is removing part of the dissolved aromatic hydrocarbon load as it enters the lake. Examination of the synchronous fluorescence emission spectra of extracts showed that the one- and two-ring aromatic hydrocarbons are
87
Petroleum hydrocarbon pollution of Lake Burley Griffin TABLE 1
Aromatic Hydrocarbons in Lake Burley Griffin Sample location
Aromatic hydrocarbon c o n e Dissolved
1 2 3 4 5 6 7 8 9 10 11 Lee's Creek
(~g/L) a
Probable source
Particulate
(T)
(C)
(T)
(C)
0-9 0.9 1.1 1-4 1.1 0.3 3.2 1-8 0.3 0.7 0.6 0.14
2.2 1.6 1.5 1.5 1.7 1.7 1.8 1.4 1.6 1.7 1.8
Petroleum Hydrocarbon Pollution of Lake Burley Griffin
W. M a h e r , C. T o m l i n s & J. F u r l o n g e r Water Research Center, Canberra College of Advanced Education, PO Box 1, Belconnen0 ACT 2616, Australia (Received 22 August 1988; accepted 25 October 1988)
ABSTRACT Aromatic hydrocarbons were measured in Lake Burley Griffin by fluorescence spectroscopy to gain an estimate of the pollution of the lake by petroleum hydrocarbons. Aromatic hydrocarbons are reported as equivalents of m-terphenyl (T) and chrysene (C). Observed concentrations are 0.3-2.2 pg/litre (T) and 0.1-0.5 pg/litre (C). Widespread distribution of fuel distillates is evident with only a small contribution from lubricating and heavier oils.
1 INTRODUCTION Pollution of aquatic environments by petroleum hydrocarbons is of concern as it is recognized that low level hydrocarbon inputs may have long-term ecological effects (Steele, 1977; H a n n a h et al., 1982; Cowles & Remillard, 1983) even in the absence of acute immediate detrimental effects (Connell & Miller, 1980). The presence of aromatic hydrocarbons in water samples provides a marker of petroleum hydrocarbon pollution as all oils contain aromatic hydrocarbons while few, if any, biogenic aromatic hydrocarbons are produced in aquatic environments (Hase &Hites, 1976; Neff, 1979). This study uses fluorescence spectroscopy to obtain an estimate of the aromatic hydrocarbon concentrations (and hence an estimate of the petroleum contamination) in Lake Burley Griffin, a lake that serves as a recreational focus for Canberra, the Australian National Capital. 81 Oil & Chemical Pollution 0269-8579/90/$03.50 © 1990 Elsevier Science Publishers Ltd, England. Printed in Ireland.
82
w. Maher, C Tomlins, J. Furlonger
2 STUDY AREA AND SAMPLE LOCATIONS Lake Burley Griffin was created in 1964 by the construction of the Scrivener Dam across the Molonglo River. The lake has a surface area of 704.2 ha, an average depth of 4.71 m (maximum depth 14.7 m) and a mean retention time of 0-13 years. The catchment area of the lake is 186 500 ha and the land use is about 3% urban, 76% agricultural and 31% native forests. Urban development is centred on the lake with approximately 250 000 people living in the catchment area. Upstream, secondary treated sewage effluent from another city, Queanbeyan (population 20 000), enters the river draining into the lake. The locations of sampling stations are shown in Fig. 1. Sample sites on the perimeter of the lake correspond to inflows from storm water drains. A water sample was also collected from Lee's Creek, an upland stream draining an undisturbed forest catchment near Canberra. This water sample was used to give an indication of natural background levels.
3 MATERIALS AND METHODS
3.1 Equipment All fluorescence measurements were made with a Hitachi F-4000 spectrofluorimeter with 1 cm quartz cells.
3.2 Reagents All solvents were HPLC grade. Stock solution of m-terphenyl and chrysene (200 ~g/ml) were prepared by dissolving these compounds in n-hexane. Aliquots of these solutions were diluted when required with n-hexane. Microparticulate separatory columns (Sep-pak C 18 and silica) were obtained from Waters Associates. Water used was deionized, distilled and hydrocarbon filtered using a Barnstead/Nanopure water purification system.
3.3 Preparation of equipment Glassware and utensils were soaked in 6% V/V Decon 90 for 24 h, rinsed in distilled water and soaked for a further 24 h in dilute chromic acid. After rinsing five times with distilled water and drying in an oven (110°C) all items were rinsed with n-hexane and allowed to air dry. Used items were soaked in ethanol before washing with detergent.
Petroleum hydrocarbon pollution of Lake Burley Griffin
83
to)
t.d
o
o
o
(D
E
E
z
84
W. Maher, C. Tomlins, J. Furlonger
3.4 Sample collection Water samples were taken at a depth of 0.5 m, and 2. 5 litres were collected in 4 min. The sampler, specially constructed to collect water at the depth required and to exclude contact with any other water, consists of a Teflon inlet valve mounted on a 2.5-1itre glass Winchester held in a stainless steel cradle. Water samples that were not analysed within 24 h were acidified to pH 2-3 with sulphuric acid and stored at 4°C. Samples were neutralized with 30% W/V sodium hydroxide before filtering (German Chemists Association, 1981).
3.5 Analysis One-litre subsamples of water were filtered through hexane-rinsed Millipore glass fibre filters (0.3/2m) in an all-glass Millipore filtration apparatus. The hydrocarbons in the filtrate are described as 'dissolved' and the hydrocarbons retained on the filter as 'particulate'. Dissolved aromatic hydrocarbons were concentrated from water samples by passing 1 litre of water through a silica and a C18 Sep-pak (pre-washed with methanol (3 ml) and water (5 ml) in tandem using suction (Fisher et al., 1987). The silica cartridges were discarded and the C18 cartridges washed with water (3 ml) and the aromatic hydrocarbons eluted with dichloromethane (5 ml). About 0.1 ml of hexane was added to the extracts and the dichloromethane removed by evaporation to near dryness using a stream of nitrogen. The final volume was adjusted to 5 ml with n-hexane and extracts dried over anhydrous sodium sulphate. Recoveries of dissolved aromatic hydrocarbons through the analytical procedure estimated by additions of 5/~g of m-terphenyl and chrysene to filtered aliquots of lake water were 81 + 11% (n = 5) and 83 + 9% (n = 5) respectively. Filters were extracted with 20 ml ofn-hexane with ultrasonic treatment for 20 min. The extracts were concentrated to less than 5 ml by evaporation using a stream of nitrogen and, after adjusting the volume to 5 ml with n-hexane, dried over anhydrous sodium sulphate. The aromatic hydrocarbon contents of the extracts were estimated by fluorescence emission measurements. Solutions were excited at 300 nm and the fluorescence intensity emission measured at 330 and 380 nm. The results are reported as concentration equivalents ofm-terphenyl (T) and chrysene (C). Standard solutions of the compounds in n-hexane were run with each batch of samples and were quantified by comparison of peak heights of standards and samples. The fluorescence emission intensities of impurities in the reagents were measured as the blank.
Petroleum hydrocarbon pollution of Lake Burley Griffin
85
To identify the probable source of aromatic hydrocarbon inputs to these waters, synchronous scanning of excitation and emission wavelengths was used with the direct excitation mode. The excitation and emission wavelengths were offset by 25 nm, both slit widths were set at 5 nm and the emission spectrum from 265 to 450 nm recorded. The synchronous fluorescence emission spectra obtained were compared with those of reference materials (Fig. 2) and the most likely source assigned.
4 RESULTS A N D DISCUSSION 4.1 Fluorescence spectroscopy The fluorescence emission spectra of several crude oils and refined oils have been examined in previous studies (Maher, 1983; Smith & Maher, 1984) to determine whether they had any common features. The results showed that there were two broad groups: (1) oils with fluorescence arising predominantly from two- and three-ringed aromatic hydrocarbons with an emission m a x i m u m near 330 nm and (2) oils containing
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/
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11
]11
(c)/// E LLJ
/4\ / X \
\
"/
X
iiIl",.x~\\\,,\~
(d)/
g o LI-
300
400
500
W a v e L e n g t h (nm)
Fig. 2. Synchronous fluorescence emission spectra of reference materials. (a) Arabian crude oil, (b) Gippsland crude oil, (c) outboard engine fuel and diesel fuel, (d) lubricating oil. From Smith & Maher (1984).
86
vv Maher, C. Tomlins, J. Furlonger
aromatic hydrocarbons with three or more rings with a fluorescence emission maximum near 380 nm. It was considered appropriate to report results based on a fluorescence emission of 330 and 380 nm. Reference materials used were m-terphenyl with a fluorescence maximum at 330 nm and chrysene with a fluorescence maximum at 380 nm. The measurement of fluorescence intensity of sample extracts at two wavelengths allows the estimation of the presence of oil products based on distillate (petrol and diesel fuels) and lubricating oils. 4.1.1 Synchronous
Synchronous fluorescence emission spectra of extracts were used to assign possible sources of petroleum contamination (Lloyd, 1971; Wakeham, 1977; Smith & Maher, 1984; Maher, 1985). Three major sources are identifiable (Fig. 2): (1) fuel-distillates including gasoline and diesel fuel, with a synchronous fluorescence peak at 300 nm; (2) lube-refined products including lubricating oil with a fluorescence peak at 340 nm; (3) crude-lube oils with significant fluorescence at wavelengths of 380 nm and greater.
4.2 Petroleum hydrocarbons in Lake Burley Griffin Concentrations of aromatic hydrocarbons in sample extracts, expressed as equivalent concentrations ofm-terphenyl and chrysene, and probable sources are given in Table 1. The concentrations of dissolved and particulate aromatic hydrocarbons were up to an order of magnitude higher than those found in Lee's Creek, a creek draining an undisturbed forested catchment. The highest concentration of dissolved and particulate aromatic hydrocarbons were found in a water sample taken at a lagoon connected to Lake Burley Griffin (sample location 7). This lagoon serves as a settling trap and would account for the higher particulate aromatic hydrocarbon values. In most samples particulate aromatic hydrocarbons were low. As samples were collected in a period of low rainfall, it is expected that a high rainfall storm event would significantly increase the particulate matter and hence aromatic hydrocarbons in Lake Burley Griffin by flushing out particulate material accumulated within storm water drains. The higher levels of dissolved aromatic hydrocarbons at sample location 7 in relation to other locations is not readily explained. No point sources of petroleum hydrocarbons are evident and it can only be postulated that particulate matter is removing part of the dissolved aromatic hydrocarbon load as it enters the lake. Examination of the synchronous fluorescence emission spectra of extracts showed that the one- and two-ring aromatic hydrocarbons are
87
Petroleum hydrocarbon pollution of Lake Burley Griffin TABLE 1
Aromatic Hydrocarbons in Lake Burley Griffin Sample location
Aromatic hydrocarbon c o n e Dissolved
1 2 3 4 5 6 7 8 9 10 11 Lee's Creek
(~g/L) a
Probable source
Particulate
(T)
(C)
(T)
(C)
0-9 0.9 1.1 1-4 1.1 0.3 3.2 1-8 0.3 0.7 0.6 0.14
2.2 1.6 1.5 1.5 1.7 1.7 1.8 1.4 1.6 1.7 1.8
