Petroleum hydrocarbon contamination and remediation et... · Petroleum–hydrocarbon contamination…
Post on 01-Aug-2018
Embed Size (px)
ology 48 (2007) 139153www.elsevier.com/locate/coldregions
Cold Regions Science and Techn
Petroleumhydrocarbon contamination and remediation bymicrobioventing at sub-Antarctic Macquarie Island
John L. Rayner a,, Ian Snape a, James L. Walworth b,Paul McA. Harvey a, Susan H. Ferguson a
a Environment, Protection and Change Program, Australian Government Antarctic Division,Channel Highway, Kingston, Tasmania, 7050, Australia
b Department of Soil, Water and Environmental Science, 429 Shantz Bldg. #38, University of Arizona, Tucson, AZ 85721, USA
Natural attenuation of petroleum hydrocarbons in polar and subpolar soils is limited by low nutrients, low temperatures, andwater availability. This study investigated three sites contaminated with diesel fuel and the use of aeration to remediate one of thesites at sub-Antarctic Macquarie Island. These sites were of differing ages and had different soilwater regimes. The most recentspill (New Main Power House) occurred in 2002 and resulted in 180 metric tons of highly-contaminated (7000 mg kg1),moderately-drained, sandy soil. An older site (b1994; Old Main Power House) comprised 100 metric tons of moderately-contaminated (2800 mg kg1) water-saturated peaty soil. A third spill (b1994; Fuel Farm) contained approximately 600 metrictons of low- to moderately-contaminated (800 mg kg1) sandy soil. Using a hydrocarbon distribution model (NAPLANAL) wedetermined that non-aqueous phase liquid droplets start to form in these soils at concentrations 501000 mg kg1 mostlydepending on organic carbon fraction. An in-field treatability evaluation with an air sparge port to increase oxygen concentration inthe soils proved unsuccessful because the shallow water table and thin soil cover led to channel development. However, an easily-installed microbioventing system, comprising many small air injecting rods, successfully aerated a wide area of soil. Fieldestimates of biodegradation rates under unamended aerobic conditions were 1020 mg kg1 d1. When considered with resultsfrom a nutrient optimisation respiration experiment [Walworth, J., Pond, A., Snape, I., Rayner, J.L. and Harvey, P.M., 2007-thisissue. Nitrogen requirements for maximizing petroleum bioremediation in a sub-Antarctic soil. Cold Regions Science andTechnology, In Press.], we conclude that in situ bioremediation for these sites should treat the soil to a target concentration of200 mg kg1 in approximately 12 years of continual operation at ambient temperatures. This simple methodology could haveuseful application in the summer treatment of other waterlogged tundra soils. 2007 Published by Elsevier B.V.
Keywords: Petroleum hydrocarbons; Air sparging; Bioremediation; Sub-Antarctic; Tundra
Petroleum contamination of soil is a widespread andwell recognized global environmental issue. In cold
Corresponding author.E-mail address: email@example.com (J.L. Rayner).
0165-232X/$ - see front matter 2007 Published by Elsevier B.V.doi:10.1016/j.coldregions.2006.11.001
region soils, oil and fuel spills are among the mostextensive and environmentally damaging pollutionproblems constituting potential threats to human healthand ecosystems (Snape et al., in press). There is evi-dence that spills are more damaging in cold regions, andthat ecosystem recovery is slower than in warmerclimates (AMAP, 1998; Det Norske Veritas, 2003). In
140 J.L. Rayner et al. / Cold Regions Science and Technology 48 (2007) 139153
this environment the rate of natural attenuation is veryslow, and the rate of off-site migration is often relativelyfast (Gore et al., 1999; Snape et al., 2006a).
Remediation of petroleum contaminated soils ismuch more expensive in polar and subpolar regionsthan in developed temperate regions. Dig-and-haul andoffsite treatment is particularly expensive, with costestimates from Antarctica being around US$4000/metric ton, and up to US$450/metric ton in Alaska(Filler et al., 2006; Snape et al., 2005). Such treatment isalso environmentally damaging because the soil that isremoved is essentially destroyed, and the underlyingpermafrost can be degraded. Low-cost, on-site remedi-ation alternatives have not been widely adopted in theseregions, largely because problems such as remoteaccess, high energy costs and environmental factorsmust be managed to achieve accelerated clean-up.Environmental factors include low temperatures, spa-tially- and temporally-variable water distributions, lownutrients and soil heterogeneity. Unlike some sitescloser to the poles, (Ferguson et al., 2003a,b; Walworthet al., 1999), many subpolar or polar tundra sites areprimarily limited by excess rather than lack of water.Soils with high water contents typically have lowoxygen diffusivities and associated low oxygen levelswhich, when coupled with other limitations such as lowtemperatures and low nutrient availability, can reducenatural biodegradation to nearly negligible rates.
Few studies have evaluated the effects of increasedaeration on hydrocarbon contaminant degradation inArctic soils, and we are aware of none in the Antarctic.Although their studies did not directly evaluate soilaeration, Reynolds et al. (1998) observed that longerhydrocarbon half-lives were associated with areas of aFairbanks (Alaska, USA) landfarm that tended to remainsaturated for longer periods after rain, indicating thatpoor aeration may have limited bioremediation. Simi-larly Yeung et al. (1997) found that the half-life of crudeoil in contaminated soil was reduced from 248 to182 days by providing aeration to a bio-treatment cell inAlberta, Canada. Research quantifying the relationshipbetween soil oxygen levels and hydrocarbon biodegra-dation in cold region soils is lacking, however severalstudies (such as those cited above) indicate that rates ofdegradation may be increased by aerating oxygenlimited soils. Research on biodegradation of naturallyoccurring organic material (NOM) in northern soils alsodemonstrates that degradation of these materials in wetenvironments is limited by lack of oxygen and can beaccelerated by providing aeration (Shaver et al., 2006).
As part of a regional survey of fuel-contaminatedsoils in Australian Antarctic Territory and the Australian
sub-Antarctic islands, the Australian Government Ant-arctic Division (AGAD) has been evaluating the natureof fuel contamination and determining the remediationpotential of on-site techniques. Here we report theresults of our field evaluation for sub-AntarcticMacquarie Island and discuss the results of a remedi-ation technique using microbioventing that couldbenefit other subpolar contaminated sites and wet tundrasoils.
Macquarie Island is a World Heritage sub-Antarcticarea located in the Southern Ocean approximately1500 km south of Tasmania (Fig. 1). It is an importantbreeding ground and terrestrial habitat for migratingmammals and birds. Temperatures range from 3 to 8 C.It has strong winds and an annual rainfall of 920 mmover 326 rain days. A research station is situated on anarrow isthmus at the northern extremity of the islandand has an elevation b10 m above sea level. Soils on theisthmus are derived from basalts and dolerites and areprincipally medium- to coarse-grained sand with littlefine material.
The AGAD has maintained a permanent station onMacquarie Island since 1948. For station operationsthere is a need to supply and store fuel (Special AntarcticBlend, SAB) and lubricants, and a number of spills inthe range 100010000 L have occurred. In 1994,Deprez et al. conducted a preliminary assessment ofcontaminants at Macquarie Island. Their survey com-prised soil samples from the surface and composite bulksamples, but with little depth information to delineatethe vertical extent of contaminated soil. Two contam-inated sites identified by Deprez et al. (1994), the MainPower House (MPH) and the Fuel Farm (FFM), areexamined in detail here. An additional site from a recentspill adjacent to the culvert to the south of thepowerhouse is also examined. To distinguish the twoMPH sites they are referred to as the Old MPH and NewMPH sites respectively.
The soils associated with areas of fuel contaminationare variable. To the southeast of the powerhouse at theOld MPH spill, soil has high organic matter content; it isoverlain with tussock grass and is periodically saturatedwith water. More generally, there is a perched watertable 1020 cm below the soil surface that is rechargedby almost daily rain and subsurface runoff fromWireless Hill to the east. Soil to the south and southeastof the powerhouse at the New MPH site is sandy; it iswithout tussock covering and is moderately free-draining. The water table fluctuates, but typically occurs
Fig. 1. A, location of Macquarie Ocean in the Southern Ocean; B, location of Macquarie Island Station and reference sample sites south of the station(SST); C, location of the contaminated areas investigated at the Main Powerhouse and Fuel Farm.
141J.L. Rayner et al. / Cold Regions Science and Technology 48 (2007) 139153
at depths of 2030 cm. Water can sometimes be seen todischarge at the break in slope to the SE onto the beach.Soil surrounding the FFM is sandy fill and is largelydevoid of vegetation. It is highly free-draining but isshallow and underlain by impermeable bedrock. Adiscontinuous spring line occurs at the bedrock-soil/overburden interface.
To date there has been no active remediation of fuelspills and any reduction of fuel concentrations has beenachieved by natural attenuation through runoff, disso-lution and biodegradation.
3. Materials and methods
3.1. Sample collection and handling
Soils were collected in March 2003 from two sitescorresponding to the recorded fuel spills at the Old MPHand New MPH (Fig. 2). A third site, the FFM, was alsosampled (Fig. 3). Uncontaminated reference sampleswere collected from 500 m to the south of the stationbuildings (SST) and from Green Gorge and WaterfallBay, 15 and 20 km away respectively (Fig. 1, inset B).
Soil samples were collected from pits and soil cores.Cores were retrieved in 50 mm (i.d.) polycarbonatesleeves which were driven into the ground inside a steelcasing with a 50 mm diameter stainless steel cuttingshoe. A one-way ball valve at the top of the pistonmaintained recovery, and soil core compaction (525%mean=9%) was measured by the difference between thedepth of the hole and the length of the core. Samplesfrom pits were collected by digging an open pit(4040 cm) with a spade and taking samples fromthe pit face with a stainless steel spoon.
Samples from MPH1-10 (Fig. 2) were taken by core;MPH11-17 were from soil pits; MPH18 was apiezometer installation installed with an auger. Coringwas not possible in the region of MPH11 to MPH17 dueto large cobbles in the profile and the close proximity togentoo penguins. Sites FFM1-6 and FFM13 werecollected by core (Fig. 3). All other samples weretaken from soil pits.
Water samples were collected from multiport sam-plers, piezometers, soil pits, and seeps using a 50 mLglass syringe. Samples for chemical analysis werefrozen until analysed on return to Australia.
Fig. 2. A Contour Map of the area surrounding the Main Powerhouse. The locations of the monitoring arrays are indicated by dashed circle.
142 J.L. Rayner et al. / Cold Regions Science and Technology 48 (2007) 139153
3.2. Physical analysis
Cores were cut into 5-cm sections, sub-sampled forchemical analysis, and the remaining soil oven dried toconstant weight at 105 C to determine gravimetricwater content. The core barrels were cleaned anddimensions measured with callipers to determine thevolume for estimates of soil bulk density and porosity(results available on-line at www.aadc.aad.gov.au).
3.3. Chemical analysis
Sub-sampleswere taken from 5-cm core sectionswith a6 mm diameter stainless steel mini-corer. The soil wasextruded from the mini-corer into a 40 mL screw top vialwith a stainless steel pushrod. Four sub-samples weretaken from each 5 cm core section to give amass of soil forextraction of 101 g. A 0.5-mL volume of internal stan-dard solution containing 1000 mg L1 cyclo-octane,100 mg L1 d8-naphthalene, 100 mg L
1 p-terphenyl and1000 mg L1 1-bromoeicosane dissolved in hexane wasadded to the soil, followed by the addition of 10 mL ofwater and 10 mL of hexane. The vials were then tumbledend over end (50 rpm) overnight, centrifuged at 110 g,and the hexane layer transferred into a 2 mL vial for Gas
Chromatography-Flame Ionisation Detector (GC-FID)analysis.
The GC-FID was a Varian 3800 fitted with 30 mcapillary column (BP-1, 0.22 mm i.d., 0.25 m filmthickness, supplier SGE). The injector temperature was270 C and 1 L of sample was injected at a split ratio of1:32. The carrier gas used was helium and GC ovenconditions were 35 C for 2.5 min, ramped at 25 Cmin1 to 310 C and held isothermally for 1.5 min,giving a total run time of 15 min. The detectortemperature was 260 C.
Calibration was carried out by dissolving SAB inhexane and using an identical extraction and analyticalprocedure to that outlined above. Standards were run atthe start, middle, and end of each batch of 35 samples.Blank hexane and hexane with internal standard wererun with each batch to allow for correction of baselinedrift and column bleed. The concentration of fuel, whichis mostly aliphatic, was determined by integrating allpeaks between 5 and 15 min with the Varian Starsoftware (Version 5.3) and subtracting the internalstandards.
Water samples with a high particulate content wereextracted as two parts: an aqueous phase and acombined particulate and aqueous phase. For the
Fig. 3. A Contour Map of the area surrounding the Fuel Farm.
143J.L. Rayner et al. / Cold Regions Science and Technology 48 (2007) 139153
aqueous phase, a spike of D8-toluene was added toapproximately 200 mL of sample. This was allowed toequilibrate for 30 min. Then 7.5 mL dichloromethanewas added, mixed end over end for 16 h, andcentrifuged. When an emulsion formed this was brokenby the addition of salt (NaCl).
The solubility of SAB in water was determined byequilibrating 30 mL of SAB with 1 L of MilliQ water ina separating funnel, and mixing on a rotary shaker(100 rpm) at 20 C. After equilibrating for 50 days watersamples were collected from the bottom of the funnelbefore being centrifuged to remove any microdroplets,and extracted as described above.
Samples taken from the cores were sent to AnalyticalServices Tasmania for analysis of ammonium (NH4
), potassium (K) and phosphorous (P) usingstandard methods.
The organic matter profile from core samples wasdetermined to assess how fuel distribution coincides withorganic matter, and to allow more accurate calculation ofair filled porosity given the density differences betweenorganic and inorganic soil constituents. Organic mattercontents were determined by loss on ignition (Dean,1974). Approximately 10 g soil was put into a cru...