Progress report

FINAL REPORT
22 November 2005
SCREENING ASSESSMENT OF CHEMICAL CONTAMINANTS AT THE
BOWSERTOWN LANDFILL, MANTEO, NC
Nancy M. White
Director, UNC Coastal Studies Institute
217 Budleigh Street, PO Box 699
Manteo, NC 27954
Dare County
PO Box 1000
Manteo, NC 27954
Damian Shea
Department of Environmental and Molecular Toxicology
North Carolina State University
Raleigh, NC 27695
(919) 513-3899
[email protected]
Background
Dare County, NC would like to investigate the possibility of reclaiming and improving the Bowsertown Landfill Site in Manteo, NC for other public use. Prior to any formal action to reclaim this property, Dare County requested that a screening assessment for chemical contaminants be conducted to provide an initial assessment of the types and amounts of chemicals that might be present at or near the landfill. Objectives and Scope
Discussions with interested parties led to a request for a chemical screening assessment in water and sediment surrounding the landfill. Chemical contamination at landfills typically is not distributed evenly across the site because significant chemical sources usually originate from the disposal of specific storage or waste containers. Therefore, random sampling of the landfill soils themselves could easily miss any possible chemicals. Instead, it was decided to assess the long term, chronic release of chemicals (through leaching and erosion) to the water and sediment that surrounds the landfill. The landfill is surrounded by water on three sides (Figure 1), though the north side of the site has only an intermittent stream/channel. The scope of work included sampling water and sediment, and deploying passive sampling devices in water surrounding the site and measuring a broad suite of chemicals in these samples. These data are intended to provide Dare County with an initial assessment of whether or not the site is obviously contaminated with significant quantities of chemicals. Water, sediment, and passive sampling devices (PSDs) were collected from the waters surrounding the landfill (Figure 1). Sites 1-3 were along the channel on the south side of the landfill. Site 1 was near the boat ramp; Sites 2 and 3 were approximately one-third and two- thirds of the distance toward the open bay waters toward the west side of the landfill. Sites 4 and 5 were located on the western, bay-side of the landfill, approximately equidistant from the two channels surrounding the landfill. Sites 6-8 were on the stream/channel on the northern side of the landfill. Sites 7 and 8 were nearly dry when the passive sampling devices were collected, so only water and sediment data are available for those two sites. Sample collection methods followed standard procedures. Water samples were collected in 1-L amber glass jars (for semi-volatile organics), 40-mL VOC vials (for volatile organic chemicals), or Teflon® bottles (for metals). Samples were placed on ice, transported to the laboratory, held at 4° C, and extracted within 24 hours of collection. Sediment samples were collected in the shallow waters by hand using a scoop. Sediment was scooped into a glass jar, placed on ice, transported to the laboratory, held at -20° C, and extracted within 30 days of collection. PSDs were placed in protective cages tethered to a line, submerged in the water, and retrieved ~30 days later. PSDs were placed in aluminum foil, placed on ice, transported to the laboratory, held at -20° C, and extracted within 30 days of collection. All materials that came in contact with water, sediment, or PSD samples were cleaned with solvents/acids or by baking at 400° C. Samples were analyzed for polycyclic aromatic hydrocarbons (PAHs) by gas chromatography mass spectrometry (GC-MS) using a modification of EPA Method 8270, volatile organic chemicals by GC-MS using EPA Method 8260, chlorinated pesticides and polychlorinated biphenyls (PCBs) by GC with dual-column electron capture detection (GC-ECD) using a combined EPA Method 8081/8082, and metals by inductively coupled plasma mass spectrometry (ICP-MS) using EPA Method 6020. Current-use pesticides were measured by GC- MS using a method similar to EPA Method 8270 that was developed by the Analytical Toxicology Laboratory at NCSU. Finally, water extracts were also analyzed by full-scan GC- MS to obtain spectra that can be matched with a computer library of spectra for over 100,000 organic chemicals (many synthetic and industrial chemicals). The intent was to determine whether any of these >100,000 chemicals were detectable in the water. The detection limits of this full-scan method is approximately 100-1000 times higher (that is, less sensitive) than the methods used above, but the full-scan method allows for the identification of many more chemicals. The methods discussed above target a specific list of chemicals of possible concern and allow both identification and quantification (how much) of the chemicals. Results and Discussion
Water Analyses
Concentrations of chemicals in water samples are listed in Tables 1-5 (at the end of the report). The only PCBs detected were PCBs 101 and 153 (Table 1). Concentrations of all PCBs were below 1 ng/L. These are very low concentrations, on the order expected in relatively pristine and uncontaminated waters, and indicate there is probably no significant human or ecological health hazard in these waters associated with PCBs. The listed concentration of total PCBs is well below the EPA chronic Water Quality Criteria (WQC) for the protection of aquatic life in salt water (30 ng/L), slightly below the NC aquatic life water quality standard for saltwater (1 ng/L), slightly below the EPA 10-5 cancer risk WQC for human health (0.64 ng/L), and above the NC water quality standard for human health (0.079 ng/L). The closeness of the measured PCB to the human health WQC should not be cause for alarm because the methodology used by EPA to establish this WQC (and the NC standard is based on the EPA criteria) has been widely criticized and is rarely used for regulation. The PCB concentrations measured here are similar to those measured throughout the coastal waters of NC and thus the landfill is probably not a significant contributor to the measured PCB concentrations. The only chlorinated pesticides detected in the water were heptachlor and the chlordanes (alpha, gamma, and trans-nonachlor) and all were below 1 ng/L (Table 1). These are very low concentrations, approximately 10 times below the NC aquatic life water quality standard for saltwater (4 ng/L) and slightly above NC water quality standards for human health (0.214 ng/L for heptachlor and 0.588 ng/L for chlordane). These human health criteria/standards have received the same criticism as the PCB criteria. The measured concentrations of heptachlor and chlordanes are similar to those reported in many waters adjacent to land and are even below the concentrations that often result from blank contamination in the laboratory. It is quite possible that the measured concentrations of chlordane and heptachlor are a result of contamination. No volatile organic chemicals were detected in any of the water samples (Table 2). Several of the lower molecular weight PAHs were detected in waters samples, but no higher molecular weight PAHs were detected. Note that the molecular weight of the PAH generally increases as one goes down the list of PAH in Table 3. More specifically, the naphthalenes were detected along with small amounts of phenanthrene. This is indicative of petroleum and with the highest concentrations being in the channel used for boats (Sites 1-3), the source of these PAHs is likely dominated by boat traffic. All of the PAH concentrations listed are below the EPA WQC. The NC water quality standard for human health is based on the sum of the 16 EPA Priority Pollutant PAH (PP-PAH); naphthalene and phenanthrene were the only PP-PAH detected and their sum is below the NC standard (31.1 ng/L). No current-use pesticides were detected in any water samples (Table 4), excepting the All of the metals were detected in all samples, except cadmium which was only detected at Sites 1 and 2. We used a particularly sensitive method to measure the metals and all concentrations measured are well below both EPA WQC and NC standards. The full-scan GC-MS analysis identified very few additional chemicals from the library search of over 100,000 chemicals. In addition to identifying some of those chemicals already identified above, phthalates and nonylphenol were detected in all water samples. These chemicals are used in plastics and are commonly detected in the environment and often even just in laboratory blank samples (contamination of laboratory plastic ware). Although this full-scan method is not quantitative, there was no apparent pattern to the magnitude of instrument response (which is related to the amount present) and all samples seemed to have about the same amount of these chemicals and similar to that often found in uncontaminated waters. Therefore, the landfill does not appear to be a dominant source of these chemicals and they may simply be a result of laboratory contamination. Water samples from Sites 1 and 2 also had detections of N,N-diethyl- m-toluamide (the insect repellant DEET), acetominophen (Tylenol), and mesalamine (a drug used to treat colitis). DEET is often found in waters where people in or on the water use DEET; the person sampling was not using DEET. The other two chemicals have been found in waters that receive municipal or septic or hospital wastes, acetominophen is particularly common. It is not clear what the source of these two chemicals would be in the boat channel and it is possible that some other chemical(s) of similar structure was interfering with the analysis. The library match of the mass spectra was very good, but uncertainty in this identification still exists. There were no other chemicals identified that are not commonly found in natural waters. For example, many plant sterols were detected but they are naturally occurring. Passive Sampling Device (PSD) Analyses
The PSDs are made of an inert polymer and they passively accumulate persistent hydrophobic chemicals such as PCBs, chlorinated pesticides, and PAHs from water. PSDs can provide an indication of what chemicals are present in the water below the detection limit of standard water analysis and what chemicals could potentially accumulate in the food chain. There are no state or Federal guidelines associated with chemical residues in PSDs. Using calibration data that we have previously published, we can convert measured residues in the PSDs to estimated average concentrations of the chemicals in the water over the period of time that the PSDs were deployed (~30 days). These estimated concentrations of chemicals in water are listed in Tables 6 and 7 and they are similar to those measured directly in the water. This provides some confirmation that the values we reported in Tables 1 and 3 using more standard methods (grabbing a water sample, extracting it, and analyzing it) are probably representative of chronic longer term exposure in these waters. Note that a few chemicals not detected by the standard methods (Tables 1 and 3) were detected by the PSDs, such as a few of the PCBs and a DDT degradation product (4,4’-DDE). This is likely a result of better detection limits using the PSDs and these very low estimated concentrations in water confirm the statement above that concentrations of PCBs, chlorinated pesticides, and PAHs are very low in the waters surrounding the landfill. Sediment Analyses
Sediments often serve as a sink and the ultimate repository for persistent chemicals that enter water and thus they provide a complementary means of assessing chronic input of chemicals to a system. Trace levels of PCBs and chlorinated pesticides were detected in sediments at Sites 1-3 and 6-8 (Table 8). The concentrations are in the range expected for relatively uncontaminated sediment and the data provide no indication of potential hazards associated with PCBs or pesticides. Concentrations of PAH were low and dominated by the higher molecular weight PAH (Table 9) that are known to be associated with combustion sources and to have a preference to absorb into the organic carbon (detritus) in sediment rather than remain dissolved in the water. The lower molecular weigh PAH (e.g., naphthalene) prefer to remain dissolved in water and thus it is not surprising to see lower concentrations of these PAHs in the sediment even though they were found in the water above the sediment. It appears that Sites 1-3, that are in the boat channel, are receiving PAH input from boat motor exhaust and that these PAHs are absorbing into the sediment. However, even the highest PAH concentrations in the sediment are not a cause for concern. Although there are no EPA criteria or NC standards for chemicals in sediment, various “guidelines” do exist for many PAH and those guidelines are much higher than what has been measured at these sites. Metals were detected in all samples (Table 10), but the concentrations were within the range expected for clean or minimally contaminated sediment . Based on the analyses of water, sediment, and passive sampling device (PSD) samples, there is no evidence of significant risk to human or ecological health from concentrations of PCBs, pesticides, PAHs, volatile organic chemicals or metals in the aquatic area surrounding the Bowsertown Landfill. Concentrations of most chemicals are similar to what one would expect for a relative clean environment. The only chemicals that are at somewhat elevated concentrations are certain PAHs and they appear to be coming from boat traffic in the channel on This study was intended only as a screening assessment and the data provided here cannot be used to perform a risk assessment or to “clear” the site for improvement. However, given the generally uncontaminated condition of the waters and sediment surrounding the Bowsertown Landfill, there is no apparent reason not to begin more formal proceedings to reclaim the site for other public use as prescribed by State and Federal regulations. Figure 1.
Tabel 1. Concentrations of PCBs and pesticides in water collected from BowserTown Landfill (ng/L) PCBs
PCB 8
Pesticides
chlorpyrifos
Table 2. Concentrations of Volatile Organic Chemicals in water collected from BowserTown Landfill (ng/L) bdl: below detection limit (1000 ng/L or 1 ug/L) Table 3. Concentrations of PAHs in water collected from BowserTown Landfill (ng/L) Table 4. Concentrations of current-use pesticides in water collected from BowserTown Landfill (ng/L) Table 5. Concentrations of metals in water collected from BowserTown Landfill (ng/L) Table 6. Concentrations of PCBs and pesticides in water based on PSDs collected from BowserTown Landfill (ng/L) PCBs
PCB 8
Pesticides
chlorpyrifos
Table 7. Concentrations of PAHs in water based on PSDs collected from BowserTown Landfill (ng/L) Table 8. Concentrations of PCBs and pesticides in sediment collected from BowserTown Landfill (ng/g, dry weight) PCBs
PCB 8
Pesticides
chlorpyrifos
Table 9. Concentrations of PAHs in sediment collected from BowserTown Landfill (ng/g, dry weight) Table 10. Concentrations of metals in sediment collected from BowserTown Landfill (mg/kg, dry weight) bdl: below detection limit (1 mg/kg, dry weight)

Source: http://csi.northcarolina.edu/content/Bowsertown_toxicology_report.pdf