Environmental Samples Holding Time Studies with Alternative Preservation Strategy
Oral Presentation
Prepared by D. Kong1, G. Douglas2, J. Hardenstine2, R. Arnold1, W. Gala1
1 - Chevron Energy Technology Company, 100 Chevron Way, 50-1263, Richmond, CA, 94802, United States
2 - NewFields Environmental Forensics, 300 Ledgewood Place, Suite 305, Rockland, MA, 02370, United States
Contact Information: kitty.kong@chevron.com; 510-242-1654
ABSTRACT
Site investigations require the collection and analysis of representative environmental samples to delineate impacts, risk, and remediation options. For petroleum related sites, BTEX and semi-volatile polycyclic aromatic hydrocarbons (PAH) are the primary contaminants of concern. When environmental samples such as water and soil/sediment are removed from the natural environment, the chemical components such as BTEX and the semi-volatile polycyclic aromatic hydrocarbons (PAH) begin to change due to physical processes such as evaporation, adsorption, precipitation, chemical processes such as photo-degradation and microbial degradation. Preservation techniques are used to minimize these changes between collection and analysis of the environmental sample. The most common preservation methods for samples are refrigeration and freezing (solid samples) and acidification (water samples) at sub-ambient temperatures (e.g., 4ᴼC). The regulatory agencies have created consensus holding time requirements of seven (7) days for water and (14) fourteen days for soil samples. The technical basis for these requirements are not well defined, yet the cost and data usability impacts are substantial.
Laboratory based studies were performed on water samples for BTEX and on water and sediment samples for PAH compounds to determine if acid (water) and sodium azide (sediment) preservation methods could be used to minimize sample degradation at ambient temperature. Statistical analysis of the data determined that there was no statistical difference from T=0 days for the PAH in the sediment samples for up to 60 days preserved with sodium azide and up to at least 14-days with no preservative. The largest impact to sample degradation was PAH phytolysis of samples for one time series of sample extracts that were exposed to ambient light for an excessive period of time (> 5 days). Corrective action to remedy this issue was later implemented by having the laboratory process the extracts immediately after sample extraction, and to store the extracts in a dark environment when they were not being processed. Finally, a study of BTEX holding times in water determined that these compounds were stable when preserved at ambient temperature for 21 days.
Additional studies are planned to further delineate accurate and defensible holding times for water and soil/sediment samples collected at petroleum impacted sites. Although every attempt is made to achieve USEPA holding time guidelines, when samples are lost in transit, or cooler temperatures exceed recommended values (e.g., 4ᴼC ± 2ᴼC) an understanding of ambient temperature impacts could be used to support the reliability of BTEX and PAH analyses performed on these nonconforming samples.
Site investigations require the collection and analysis of representative environmental samples to delineate impacts, risk, and remediation options. For petroleum related sites, BTEX and semi-volatile polycyclic aromatic hydrocarbons (PAH) are the primary contaminants of concern. When environmental samples such as water and soil/sediment are removed from the natural environment, the chemical components such as BTEX and the semi-volatile polycyclic aromatic hydrocarbons (PAH) begin to change due to physical processes such as evaporation, adsorption, precipitation, chemical processes such as photo-degradation and microbial degradation. Preservation techniques are used to minimize these changes between collection and analysis of the environmental sample. The most common preservation methods for samples are refrigeration and freezing (solid samples) and acidification (water samples) at sub-ambient temperatures (e.g., 4ᴼC). The regulatory agencies have created consensus holding time requirements of seven (7) days for water and (14) fourteen days for soil samples. The technical basis for these requirements are not well defined, yet the cost and data usability impacts are substantial.
Laboratory based studies were performed on water samples for BTEX and on water and sediment samples for PAH compounds to determine if acid (water) and sodium azide (sediment) preservation methods could be used to minimize sample degradation at ambient temperature. Statistical analysis of the data determined that there was no statistical difference from T=0 days for the PAH in the sediment samples for up to 60 days preserved with sodium azide and up to at least 14-days with no preservative. The largest impact to sample degradation was PAH phytolysis of samples for one time series of sample extracts that were exposed to ambient light for an excessive period of time (> 5 days). Corrective action to remedy this issue was later implemented by having the laboratory process the extracts immediately after sample extraction, and to store the extracts in a dark environment when they were not being processed. Finally, a study of BTEX holding times in water determined that these compounds were stable when preserved at ambient temperature for 21 days.
Additional studies are planned to further delineate accurate and defensible holding times for water and soil/sediment samples collected at petroleum impacted sites. Although every attempt is made to achieve USEPA holding time guidelines, when samples are lost in transit, or cooler temperatures exceed recommended values (e.g., 4ᴼC ± 2ᴼC) an understanding of ambient temperature impacts could be used to support the reliability of BTEX and PAH analyses performed on these nonconforming samples.
Oral Presentation
Prepared by D. Kong1, G. Douglas2, J. Hardenstine2, R. Arnold1, W. Gala1
1 - Chevron Energy Technology Company, 100 Chevron Way, 50-1263, Richmond, CA, 94802, United States
2 - NewFields Environmental Forensics, 300 Ledgewood Place, Suite 305, Rockland, MA, 02370, United States
Contact Information: kitty.kong@chevron.com; 510-242-1654
ABSTRACT
Site investigations require the collection and analysis of representative environmental samples to delineate impacts, risk, and remediation options. For petroleum related sites, BTEX and semi-volatile polycyclic aromatic hydrocarbons (PAH) are the primary contaminants of concern. When environmental samples such as water and soil/sediment are removed from the natural environment, the chemical components such as BTEX and the semi-volatile polycyclic aromatic hydrocarbons (PAH) begin to change due to physical processes such as evaporation, adsorption, precipitation, chemical processes such as photo-degradation and microbial degradation. Preservation techniques are used to minimize these changes between collection and analysis of the environmental sample. The most common preservation methods for samples are refrigeration and freezing (solid samples) and acidification (water samples) at sub-ambient temperatures (e.g., 4ᴼC). The regulatory agencies have created consensus holding time requirements of seven (7) days for water and (14) fourteen days for soil samples. The technical basis for these requirements are not well defined, yet the cost and data usability impacts are substantial.
Laboratory based studies were performed on water samples for BTEX and on water and sediment samples for PAH compounds to determine if acid (water) and sodium azide (sediment) preservation methods could be used to minimize sample degradation at ambient temperature. Statistical analysis of the data determined that there was no statistical difference from T=0 days for the PAH in the sediment samples for up to 60 days preserved with sodium azide and up to at least 14-days with no preservative. The largest impact to sample degradation was PAH phytolysis of samples for one time series of sample extracts that were exposed to ambient light for an excessive period of time (> 5 days). Corrective action to remedy this issue was later implemented by having the laboratory process the extracts immediately after sample extraction, and to store the extracts in a dark environment when they were not being processed. Finally, a study of BTEX holding times in water determined that these compounds were stable when preserved at ambient temperature for 21 days.
Additional studies are planned to further delineate accurate and defensible holding times for water and soil/sediment samples collected at petroleum impacted sites. Although every attempt is made to achieve USEPA holding time guidelines, when samples are lost in transit, or cooler temperatures exceed recommended values (e.g., 4ᴼC ± 2ᴼC) an understanding of ambient temperature impacts could be used to support the reliability of BTEX and PAH analyses performed on these nonconforming samples.
Site investigations require the collection and analysis of representative environmental samples to delineate impacts, risk, and remediation options. For petroleum related sites, BTEX and semi-volatile polycyclic aromatic hydrocarbons (PAH) are the primary contaminants of concern. When environmental samples such as water and soil/sediment are removed from the natural environment, the chemical components such as BTEX and the semi-volatile polycyclic aromatic hydrocarbons (PAH) begin to change due to physical processes such as evaporation, adsorption, precipitation, chemical processes such as photo-degradation and microbial degradation. Preservation techniques are used to minimize these changes between collection and analysis of the environmental sample. The most common preservation methods for samples are refrigeration and freezing (solid samples) and acidification (water samples) at sub-ambient temperatures (e.g., 4ᴼC). The regulatory agencies have created consensus holding time requirements of seven (7) days for water and (14) fourteen days for soil samples. The technical basis for these requirements are not well defined, yet the cost and data usability impacts are substantial.
Laboratory based studies were performed on water samples for BTEX and on water and sediment samples for PAH compounds to determine if acid (water) and sodium azide (sediment) preservation methods could be used to minimize sample degradation at ambient temperature. Statistical analysis of the data determined that there was no statistical difference from T=0 days for the PAH in the sediment samples for up to 60 days preserved with sodium azide and up to at least 14-days with no preservative. The largest impact to sample degradation was PAH phytolysis of samples for one time series of sample extracts that were exposed to ambient light for an excessive period of time (> 5 days). Corrective action to remedy this issue was later implemented by having the laboratory process the extracts immediately after sample extraction, and to store the extracts in a dark environment when they were not being processed. Finally, a study of BTEX holding times in water determined that these compounds were stable when preserved at ambient temperature for 21 days.
Additional studies are planned to further delineate accurate and defensible holding times for water and soil/sediment samples collected at petroleum impacted sites. Although every attempt is made to achieve USEPA holding time guidelines, when samples are lost in transit, or cooler temperatures exceed recommended values (e.g., 4ᴼC ± 2ᴼC) an understanding of ambient temperature impacts could be used to support the reliability of BTEX and PAH analyses performed on these nonconforming samples.
