The Use Of Ecological Risk Assessment For Regional Management Of Aquatic Impacts. Henri de Pennart and Roy Crowther, Alpine Environmental Ltd. Tim Taylor and Mike Morden, Petro-Canada Shawna Mattison, Pembina Pipeline Corporation

Introduction

Through a series of acquisitions, Petro-Canada has obtained a number of inactive oil and gas properties located along the Beatton River, north of Fort St. John, British Columbia. In a preliminary risk screening by Petro-Canada, all sites located within 300 m of the river were selected for investigation. In order to assess the liability associated with these properties, Alpine Environmental Ltd. (Alpine) was asked to design and implement a program to examine the upper Beatton River watershed using a holistic ecosystem based approach and document the existence of potential impacts on the river.

In agreement with Petro-Canada, Alpine developed a program designed to assess the general health of the Beatton River’s ecosystem before focusing on specific areas. This regional assessment encompassed a 75 km section of the Beatton River watershed and included several tributaries to the mainstem river (Figure 1).

Figure 1: Beatton River study area and 2003 sampling locations

Results from the regional assessment will allow Petro-Canada to implement a long-term management plan for the properties located within 300 m of the Beatton River or its associated tributaries.

Program Design

The 2003 Beatton River regional assessment program was designed as a screening program to define the scope and extent of the study area and to identify risk factors. Sampling locations along the river within the identified risk buffer were chosen based on ease of access and the availability of suitable substrate and habitat to provide samples for the various components of the program (Figure 1). In addition, similar channel morphology at each site allowed for site to site comparisons.

Sampling locations in the Beatton River initially extended from Apassin Creek to the Mile 126 road crossing (Figure 1). Results from the July 2003 survey indicated that the upstream “reference” site had likely been impacted by hydrocarbons. As a result, the section of the Beatton River investigated during the subsequent August and September surveys was extended 40 km upstream, to the Highway 97 crossing and included four tributaries (Figure 1).

Analytical parameters measured in water and sediment samples were chosen based on the chemicals anticipated to be present in the type of oil and gas operations being investigated. The analytical analysis included dissolved metals, volatile hydrocarbons including benzene, toluene, ethylbenzene and xylenes (BTEX) and light and heavy extractable petroleum hydrocarbons (EPHs) including polycyclic aromatic hydrocarbons (PAHs).

Various types of samples designed to assess surface water quality, sediment quality, benthic invertebrate diversity and abundance and the potential for impact to fish in the study area were collected as part of the program.

The Beatton River impact assessment program was based on techniques and procedures developed by Alpine for Pembina Pipeline Corporation (Pembina) in response to a large oil spill in the Pine River near Chetwynd, B.C.

Rationale and Design Basis

The results from the Pine River impact assessment showed that most ecosystem indicators were found to meet federal (CCME 2003) and/or provincial (BC AWQG 2001; BC CSR 2003) guidelines shortly after the spill. In spite of this, the ecosystem exhibited on-going impact effects from the introduction of hydrocarbons. To address these evident effects, the scope of the study was extended beyond what was required by the regulators and clearly showed the extent of impacts from the spill as well as the subsequent recovery of the Pine River ecosystem.

The Pine River aquatic impact assessment was designed from an ecosystem and risk-based perspective and included the following inter-related components: water quality (both grab samples and semi-permeable membrane devices (SPMDs)), fisheries, benthic invertebrates, periphyton and sediment quality.

SPMDs are in-situ, passive sampling devices used to detect trace levels of organic compounds in aquatic environments. As such, SPMD's are also used as a surrogate for

fish to detect long-term exposure to organic contaminants and from this information, to determine risk levels as they pertain to accumulation and/or biomagnification.

Because of the presence of hydrocarbons trapped in the river’s sediments as a result of the spill, SPMDs were used to determine the concentration of water soluble hydrocarbon compounds that were being released into the water column over time.

Benthic invertebrates form a primary receptor of impacts in aquatic ecosystems and are an important link in the food chain for fish. The destruction of and/or population denudation that can occur following a pollution event can therefore affect the upper ecosystem by elimination of an important food source. The assessment consisted of a study of the benthic community structure, biomass, species abundance and relative abundance along a longitudinal gradient.

Sediment quality is also a good indicator of aquatic ecosystems health. Most hydrocarbons are hydrophobic and when released in a waterbody will partition into the suspended solids and bottom sediments. Hydrocarbons can persist for long periods in the sediments and eventually leach back into the water column upon disturbance. The Pine River study showed that hydrocarbon impacts to sediments, particularly PAHs, persisted long after surface water quality results met criteria. PAHs are amongst the most toxic components found in products such as crude oil, diesel or condensate. Some PAHs such as benzo[a]pyrene are known human carcinogens. PAHs are ubiquitous chemicals that can be found in coal, smoked food, cigarette smoke and combustion engines exhaust.

In unrefined products, PAHs as defined by various regulatory bodies only represent a small fraction of the polyaromatic hydrocarbons. Substituted (alkylated) forms of PAHs as well as polynuclear aromatic hydrocarbons (PNAs) such as biphenyl and heterocyclic aromatic hydrocarbons (HAHs), such as dibenzothiophene can represent over 90% of the polyaromatic content of an unrefined hydrocarbon. In addition to their presence in larger concentrations, alkylated PAHs have the following properties:

• Alkylated homologues are usually more hydrophobic and more lipophilic than their parent compound;

• Alkylated homologues are considered as or more toxic than their parent compounds. Their toxicity increases with the degree of alkylation;

• Alkylated homologues are more persistent and tend to bioaccumulate to a greater degree than their parent compounds. The persistence increases with the degree of alkylation and results in an increase percentage of alkyl-PAHs vs. PAHs as the product ages.

On the Pine River, because of their persistence in the environment and potential toxicity, PAHs were used as a surrogate to trace oil spill effects and system recovery. The methods used and general ecosystem risk approach developed on the Pine River was also used to determine possible impact zones on the Beatton River. Because of the highly turbid nature of the water in the Beatton River, periphyton collection and analysis was not included in the program.

Methods

Water

Sampling protocols used followed those outlined in the British Columbia Ambient Freshwater and Effluent Sampling Manual (1997).

Semi Permeable Membrane Devices

Commercially available SPMDs were obtained from Environmental Sampling Technologies (EST), A Division of Custom Industrial Analysis Labs (CIA), St. Joseph, Missouri, USA. The preparation, deployment, retrieval and storage of the samplers followed the standard operating procedures (SOP E-42) provided by the supplier.

SPMD samplers were deployed in transects at each location in the Beatton River. A transect consisted of three samplers, one situated near each shoreline and one placed approximately mid-channel. Each sampler was deployed for a minimum of thirty days. In each of the tributaries selected, a single SPMD was deployed mid-channel, upstream of an established surface water sampling site.

Dedicated field blanks consisting of a single membrane were exposed to the atmosphere. Atmospheric exposure time for blanks was equivalent to the time required for deployment at each of these sites. Following exposure, the blanks were re-sealed in their original containers, and re-exposed during the retrieval of the samplers. SPMDs are potent vapour phase samplers and as such, blank exposure is required to account for atmospheric conditions and potential airborne constituents that may interfere with the analysis of the river water.

Huckins et al. (1993, 1996 and 1999) described the theory and various mathematical models for estimating ambient water concentrations of analytes from those sequestered by SPMDs.

Benthic

Five benthic samples were collected at each site according to the protocols described by Barbour (1999) using a modified Neill-Hess cylinder sampler.

Following taxonomic analysis, all identified benthic taxa were assigned a unique identifier code for use in later analysis. In addition, all taxa were classified into trophic, or feeding groups, to enable communities to be classified (Merritt and Cummins, 1977). Trophic classification was then used to determine whether or not community structure had been affected at the feeding level.

A number of classic benthic analytical techniques were used during the analysis to determine whether or not species diversity had been affected by the spill. The indices computed were as follows: Shannon-Weaver Index (1949), Simpson’s Index (1949), species richness (Margalef 1958) and family biotic index (Mandaville 2002), all of which are measures of species diversity. In addition, the percent contribution to the total

benthic fauna of Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddis flies), the EPT taxa, within each site was calculated.

Benthic species and the collected environmental variable data related to each survey site were analyzed using a canonical community ordination technique (Canoco V4.0, Microcomputer Power, Ithaca, NY). This pattern recognition technique was used to assess the potential effects of various environmental factors such as; current velocity, substrate complexity, depth, sediment hydrocarbon chemistry (as represented by total PAH concentrations), sediment organic content, water temperature, and distance from R0.1. The technique has been described previously in Green (1979) and Crowther and Luoma (1983).

Sediments

At each site, five replicate sediment samples were collected using modified Shelby tubes. Sampling protocol followed the standard operating procedure described in Rust (2001). The replicates were collected at or above the waterline unless stream and shoreline sediments were too shallow and/or too coarse for the coring tubes to penetrate.

Results

Pine River Case Study

In the Pine River the source and type of contamination was known. The spilled product was characterized and hydrocarbons present in the oil were tracked through the ecosystem. The study area extended over a 175 km stretch of the Pine River and included six of its major tributaries.

Figure 2: PAH concentrations in sediment collected in July 2001 in the Pine River (blue bars) and some of its tributaries (red bars). Star represents the location of the August 2000 oil spill.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

-1.8

Callazo

n Cree

k 1.5 9.5 15.6

26.0

37.3

Willo

w Cree

k 60.4

62.8

80.9

Hasler

Creek

110.1

Centur

ion C

reek

Suku

nka R

iver

121.7

Murray

Rive

r18

6.6

Distance from Spill (km)

Co

nce

ntr

atio

n (

pp

m)

Hydrocarbons were still detectable in river sediments two years after the spill. Over time hydrocarbon concentrations steadily decreased in sediments collected up to 26 km downstream of the spill but this trend was reversed in samples collected further downstream. This suggested the presence of other sources of hydrocarbons in the Pine River watershed. Results from sediments samples collected in the Pine River tributaries

confirmed that PAH loading to the Pine River were being contributed from these streams (Figure 2).

Previous studies have shown that ratios of PAHs compounds can be used to determine the origin of a hydrocarbon source. For example, the rate of degradation of C2-phenanthrenes and C2-dibenzothiophene (C2Ph/C2DBT) are similar. For this reason, these compounds are called weathering co-variants and when both present in a hydrocarbon mixture, their ratio should remain constant during the weathering process (Page et al., 1995; Douglas et al., 1996; Hostettler et al., 1999). As a result, various ratios would indicate the presence of multiple sources of hydrocarbons. PAH weathering covariant analysis and fingerprinting were performed and showed that coal was a major contributor of PAHs to the Pine River watershed (Figure 3).

Figure 3: C2-Phenanthrene/C2-Dibenzothiophene Ratio in Pine River Sediment - 2001. Although the concentrations of C2-Ph and C2-DBT in weathered and non-weathered oil are different, the C2-Ph/C2-DBT ratio remains the same. Similarly, different samples of coal collected in the Pine River valley have the same C2-Ph/C2-DBT ratio. The position of the sediment samples in relation to each regression line indicates the origin of the hydrocarbons present in them.0.01

0.1

1

10

100

1000

10000

0.01 0.1 1 10 100 1000 10000

C2-DBT (ppm)

C2-

Ph

(p

pm

)

Oil Coal Weathered Oil River Sediment (n=140)

Analytical results from surface water samples showed that the water quality in the Pine River had returned to pre-spill conditions less than three weeks after the spill. In order to determine if hydrocarbons present in the sediments were leaching into the water column, SPMDs were deployed in the Pine River and in selected tributaries. Results indicated that hydrocarbons were still present in the water column two years after the spill. However, PAH concentrations measured in the water were five orders of magnitude lower than the threshold effect levels for these chemicals (Figure 4).

Figure 4: Ambient alkylated PAHs concentrations. Pine River SPMD samples - 2000/2001. Star represents the location of the August 2000 oil spill. The red line represents the concentration at which methylnaphthalene would kill 50% of the most sensitive of fish species exposed to it (in this example Brown Trout).

0.001

0.01

0.1

1

10

100

1000

10000

2000 2001 2000 2001 2000 2001 2000 2001 2000 2001

-1.8 9.5 26 80.9 113

Distance from Spill (km)

Co

nce

ntr

atio

n (p

pb

)

Total PAHs Methyl naphthalene

Methylnaphthalene 48 Hr. LC50 - Brown Trout

The collection of benthic invertebrate samples in the Pine River initially showed a depletion of all trophic classes downstream of the spill site. By 2001 however, the benthic populations had partially recovered in the most affected areas (Figure 5). The data also showed that benthic invertebrates were apparently unaffected by the hydrocarbon loading originating from coal. This confirms previous studies showing that PAHs of coal origin are not readily bioavailable (Chapman et al. 1996).

Figure 5: Relative abundance of benthic invertebrates vs. sample location. Pine River 2000/2001. The 2000 data shows a depletion in benthic organisms downstream of the spill site. By 2001, the benthic invertebrate population had recovered. Star represents the location of the August 2000 oil spill.

0

0.5

1

1.5

2

2.5

-1.8 1.6 9.5 15.6 26 37.3 60.4 62.8 80.9 121.7 186.6

Distance from Spill (km)

August '00 August '01

The pattern recognition technique showed that shortly after the spill some trophic classes of benthic invertebrates were affected by the spill and their distribution in the river was influenced by the concentration of hydrocarbons present in the sediments (Figure 6). The relationship between sediment hydrocarbon concentrations and trophic class distributions was no longer observed in subsequent surveys, indicating a recovery of the system.

Figure 6: Spatial distribution of the collector-gatherer-scraper class of invertebrates in the Pine River in November 2000. Open circles represent benthic sampling locations, closed circles represent benthic species. Arrows represent specific environmental factors influencing the distribution of benthic invertebrates. In this example, the distribution of benthic invertebrates at sites BEN6.0, BEN6.2 and BEN7.0 was affected by the concentration of PAHs in the sediments.

Beatton River Case Study

Unlike the Pine River where the contaminants main source and point of entry in the river were known, the Beatton River was potentially affected by multiple sources and types of contaminants.

The initial sediment program conducted in July was a reconnaissance survey designed to assess the potential impacts of Petro-Canada wellsites located along or within 300 m of the Beatton River. The initial reference site (R1.0) was located upstream of most of the wellsites of interest in an attempt to collect sediment chemistry data in an area unaffected by oil and gas activities (Figure 1). However, data obtained from R1.0 indicated that the concentrations of some hydrocarbons (PAHs) were above the CCME guidelines and, as a result, a new reference site (R0.1) was added to the program. Despite being over 40 km upstream of R1.0 and outside of the potential zone of influence of the wellsites under investigation, sediments collected at R0.1 contained PAHs.

Because of the existence of "background" concentrations of PAHs, subsequent surveys were extended to assess sediment quality in tributaries to the Beatton River. The tributaries studied were those entering the Beatton River in, or near, the initial survey area, between R1.0 and R6.0. Tributaries sampled included Apassin Creek (RAC), Julienne Creek (RJC) and two unnamed tributaries (RT#1 and RT#2). Results from this extended sediment survey indicated the ubiquitous presence of PAHs in sediments collected in the Beatton River watershed (Figure 7).

Figure 7: PAH concentrations in sediment collected in August 2003 in the Beatton River (blue bars) and some of its tributaries (red bars).

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

R0.1 R0.9 ApassinCreek 2.0

ApassinCreek 1.0

R1.0 R2.0 R3.0 R4.0 JulienneCreek

R5.0 UnnamedTributary

#2

UnnamedTributary

#1

R6.0

Sample Location

Co

nce

ntr

atio

n (

pp

m)

Although PAHs may originate from various natural and anthropogenic sources, it is likely that some of the PAHs found in the Beatton River sediments were related to the oil and gas activities in the area investigated. Indications in favour of this hypothesis were the following:

• If PAHs present in the sediment were of natural origin, it is likely that their concentrations in sediments would be similar throughout the watershed and/or increased steadily from upstream to downstream locations as observed in the Pine River study. This was found not to be the case. In fact, some tributaries surveyed such as unnamed tributary #1 were almost PAH-free. Also, PAH concentrations showed important variations, both increasing and decreasing between sites;

• The composition of PAHs in the sediments varied greatly between sites suggesting the presence of local sources of hydrocarbons; and,

• The analysis of various PAH ratios indicated that the sources, the weathering state and the nature of hydrocarbon varied between sites.

A statistical analysis was developed in order to identify trends in the type and concentration of alkylated PAH compounds found in the sediments at each site. Because of the ubiquitous presence of PAHs in the sediments collected in the Beatton River watershed, the statistical analysis was used to identify sites were PAH composition or concentration was significantly different.

Of particular interest were the sediment sampling sites located along the Beatton River in the zone of influence of the Petro-Canada wellsites being investigated. These sediment sites (R1.0 through R6.0) were also compared to each other in the statistical analysis.

In all three surveys, reference site R0.1 appeared to be statistically “different" from the other sites. R0.1 seemed to have been impacted by hydrocarbons from unknown origin and should probably not be considered indicative of baseline conditions for sediment quality in the Beatton River. A bar graph comparing selected PAH compounds present in

the sediments collected at R0.1 and R4.0 illustrates the difference in PAH composition between the two sites (Figure 8). This “difference” was also noted during the analysis of PAH ratios. While hydrocarbons collected at most sites were clearly of petrogenic origin, hydrocarbons collected at R0.1 may partially be of pyrogenic origin.

Figure 8: Alkylated PAHs concentrations in sediment samples collected at R0.1 and R4.0. The PAH composition is clearly different between the two samples.

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

Benz

o(a)an

thrac

ene

C1-sub

stitute

d Ben

zo(a)a

nthrac

ene

C2-sub

stitute

d Ben

zo(a)a

nthrac

ene

Benzo

(a)pyr

ene

C1-sub

stitute

d Ben

zo(a)

pyren

e

C2-sub

stitute

d Ben

zo(a)p

yrene

Dibenzo

thioph

ene

C1-sub

stitute

d Dibe

nzoth

iophe

ne

C2-sub

stitute

d Dibe

nzoth

iophe

ne

C3-sub

stitute

d Dibe

nzoth

iophe

ne

C4-sub

stitute

d Dibe

nzoth

iophe

ne

Fluora

nthen

e

C1-sub

stitute

d Fluo

ranthe

ne

Co

nce

ntr

atio

n (p

pm

)

R0.1 R4.0

Despite, the presence of PAHs in the sediments at most of the sites sampled, no hydrocarbon were detected in water samples collected from the same locations. As previously mentioned, this is likely due to the nature of the PAHs which are hydrophobic compounds. The presence of PAHs in the water column is usually transient and observed as a result of a spill when large volumes of hydrocarbons are released at once. PAHs detected in the Beatton River are probably the result of small, but continuous and cumulative release of hydrocarbons from nearby oil and gas operations.

Analytical results of the SPMD surveys indicated the presence of PAH compounds in samples collected at all sampling locations within the study area. The compounds detected consisted of naphthalene and its alkylated homologues (methylnaphthalenes, C2- and C3-substituted naphthalenes). The detection of low concentrations of these compounds, particularly at or marginally above the method detection limit, likely indicates that there is a background level of naphthalene in the Beatton River.

Conclusion

Despite the absence of substantial concentrations of soluble PAHs, which can directly affect fish and/or other aquatic organisms, the presence of PAHs in the sediments seems to have impacted the benthic fauna at sites investigated during the 2003 benthic program. A depleted benthic fauna could have a negative impact on the aquatic ecosystem by limiting the food source for some fish and/or waterfowl species. The relationship between PAHs-impacted sediment and benthic abundance and diversity will be further examined before any conclusion can be made on the potential effects of PAHs on benthic organisms.

The ecosystem approach developed for the Pine River spill and applied in the Beatton River is now the preferred approach chosen by the British Columbia regulators in the new Criteria for Managing Contaminated Sediment (BC CSR 2003).

References

Barbour, M.T., J. Gerritsen, B.D. Snyder, and J.B. Stribling (1999). Rapid Bioassessment Protocols for Use in Streams and Wadeable Rivers: Periphyton, Benthic Macroinvertebrates and Fish, Second Edition. EPA 841-B-99-002. U.S. Environmental Protection Agency; Office of Water; Washington, D.C.

British Columbia Ministry of Water, Land and Air Protection (2001). British Columbia Approved Water Quality Guidelines (Criteria).

Canadian Council of the Ministers of the Environment (Update 3.2, 2003). Canadian Environmental Quality Guidelines.

Chapman, P.M., Downie, J., Maynard, A. and Taylor, L.A. (1996). Coal and Deodorizer Residues in Marine Sediment Contaminants or Pollutants. Environ. Contamin. Toxicol. 15: 638-642.

Contaminated Sites Regulation (2003). B.C. Reg. 375/96. Criteria for managing Contaminated Sediment in British Columbia.

Crowther, R.A. and M. E. Luoma. (1983). Pattern recognition techniques to determine benthic invertebrate trophic and community responses to industrial input. Verh. Int. Ver. Limnol. 22: 1321-19.

Douglas, G.S., Bence, A.E., Prince, R.C., McMillen, S.J. and Butler, E.L. (1996). Environmental Stability of Selected Petroleum Hydrocarbon Source and Weathering Ratios. Environmental Science and Technology 30: 2332-2339.

Green R. H. (1979). Sampling Design and Statistical Methods for Environmental Biologists. John Wiley & Sons, New York, NY.

Hostettler, F.D., Kvenvolden, K.A., Rosenbauer, R.J. and Short, J.W. (1999). Aspects of the Exxon Valdez Oil Spill - A Forensic Study and a Toxics Controversy. U.S. Geological Survey. Water Resource Investigations Report #99-4018B Volume 2. Pp 135-144.

Huckins, J.N., G.K. Manuweera, J.D. Petty, D. MacKay and J.A. Lebo (1993). Lipid-containing Semipermeable Membrane Devices for Monitoring Organic Contaminants in Water. Environ. Sci. Technol. 27: 2489-2496.

Huckins, J.N., Petty, J.D., Lebo, J.A., Orazio, C.E., Prest, H.F., Tillit, D.E., Ellis, G.S., Johnson, B.T. and G.K. Manuweera (1996). Semipermeable Membrane Devices (SPMDs) for the Concentration and Assessment of Bioavailable Organic Contaminants in

Aquatic Environments. In: Techniques in Aquatic Toxicology (G. Ostrander, editor). Lewis Publishers. CRC Press, Boca Raton, FL 704 pp.

Huckins, J.N., J.D Petty, C.E. Orazio, J.A. Lebo, R.C. Clark, V.L. Gibson, W.R. Gala and K.R. Echols. (1999). Determination of Uptake Kinetics (Sampling Rates) by Lipid-Containing Semipermeable Membrane Devices (SPMDs) for Polycyclic Aromatic Hydrocarbons (PAHs) in Water. Environ. Sci. Technol. 33: 3918-3923.

Mandaville, S.M. (2002). Benthic Macroinvertebrates in Freshwaters - Taxa Tolerance Values, Metrics, and Protocols. (Project H-1). Soil and Water Conservation Society of Metro Halifax. (http://chebucto.ca/Science/SWCS/SWCS.html)

Margalef (1958). Information Theory in Ecology. Gen. Syst. 3: 36-71.

Merritt R. W. and K. W. Cummins (1977). An Introduction to the Aquatic Insects of North America. Merritt & Cummins Eds. Kendall/Hunt Publishing Company. Dubuque, Iowa.

Page, D.S., Boehm, P.D., Douglas, G.S. and Bence, A.E. (1995). Identification of Hydrocarbon Sources in the Benthic Sediments of Prince William Sound and the Gulf of Alaska Following the Exxon Valdez Oil Spill. In: Exxon Valdez Oil Spill: Fate and Effects in Alaskan Waters, ASTM STP 1219, pp. 41-83. Peter G. Wells, James S. Hughes and Jane S. Hughes Eds. American Society for Testing and Materials, Philadelphia.

Resource Inventory Committee of British Columbia (1997). Ambient Freshwater and Effluent Sampling Manual.

Rust, T. (2001). Environmental Restoration Project Standard Operating Procedure for Sample Collection from Split-Spoon Samplers and Shelby Tube Samplers. ER2000-0737 Los Alamos National Laboratory, New Mexico.

Shannon, C. E. and W. Weawer (1949). The Mathematical Theory of Communication. University of Illinois Press, Urbana.

Simpson, E. H. (1949). Measurement of Diversity. Nature 163: 688.