Quantification of Per- and Polyfluoroalkyl Substances in Landfill Gas and Estimate of Emissions from US Landfills

Project Sponsor: EPA STAR Grant

Project Cost: $900, 000

Investigators: Florentino De la Cruz1, Ivan Titaley2, Morton A. Barlaz (PI)1, Jennifer A. Field (Co-PI)2, Staci Simonich (Co-PI)2

Institution: (1) North Carolina State Univ. (lead), Raleigh, NC; (2) Oregon State Univ. (sub),

Overview and Objectives

To our knowledge, there is no complete study that characterized PFAS in LFG. We are developing methods to collect landfill gas samples and analyze these samples for PFAS. The overall research objective is to estimate the mass of per- and polyfluoroalkyl substances (PFAS) that are present in landfill gas (LFG) and the mass of PFAS emitted as fugitive emissions. Sub-objectives are to:

  • develop methods to sample and analyze LFG for targeted and non-targeted PFAS
  • measure PFAS concentrations at a cross section of U.S. landfills in different climatic regions
  • develop a model to estimate PFAS production and emissions at the U.S. national scale
  • evaluate the potential impact of soil attenuation on PFAS emissions
  • measure PFAS production from mixed waste and food packaging materials.

Research Approach

We are working with landfill operators on strategies to pump LFG through sorbent traps that will be analyzed by low- and high-resolution gas chromatography mass spectrometry. Samples will be collected from headers to measure overall PFAS production and from individuals gas wells for analysis of the impact of waste age on PFAS concentrations. We will also use near surface LFG sampling and static chambers to qualitatively evaluate the impact of soil attenuation on PFAS concentrations as fugitive PFAS emissions will largely pass through landfill cover soils. Laboratory reactors will be operated to measure PFAS production and to understand the relationship between PFAS production and methane production for residential solid waste and food packaging materials. Finally, we will develop a model to estimate PFAS production and emissions in consideration of LFG production and emissions, climate, waste age and PFAS concentrations. Monte Carlo analyses will be used to estimate probable ranges in consideration of uncertainty.

Task 1: Develop methods to sample and analyze PFAS in LFG

We have developed and are fine tuning a sampling system (Figure 1) that will allow us to collect and pass a precise volume of LFG though a sorbent tube. We designed this system to allow us to collect samples from two target sampling points within the landfill gas collection system: (1) main header (2) well head (Figure 1).

Figure 1. Sampling diagram for landfill gas collection. Two types of sampling points (main header and well head) are shown.

A total of 47 target, semi-quantitative, and suspect volatile PFAS from nine classes will be analyzed including fluorotelomer alcohols (4:2, 6:2, 8:2, and 10:2 FTOHs), C8 perfluorinated sulfonamides (N-MeFOSA, N-EtFOSA), and C8 perfluorinated sulfonamidoethanols (N-MeFOSE, N-EtFOSE). Suspect PFAS include the C2-C7 perfluorinated sulfonamidoethanols and14:2-FTOH based on prior ambient air studies within and around landfills as well as prior studies of PFAS in atmospheric samples. 1-3 Figure 2A shows a chromatogram for the 47 compounds analyzed by TD-GC-MS, demonstrating the capability of the TD -GC-MS method to detect PFAS. Preliminary analysis on a field sample collected from a landfill in NC (Figure 2B) revealed the predominance of 4:2, 6:2, 8:2, 10:2  and 12:2 FTOHs with semi-quantitative concentrations ranging from 74 – 224 , one or two orders of magnitude higher than ambient air measurements reported above a landfill. 1-3

Figure 2. Detection of volatile PFAS by TD-GC-MS operated in PCI scan mode.

Task 2: Measure PFAS concentrations at a cross section of US landfills in different climate regions

Task 3: Develop a model to estimate PFAS production and emissions at the US national scale

Task 4: Assess the impact of soil on the attenuation of PFAS in LFG that is not collected

Task 5: Measure the production of volatile PFASs from residential MSW and food waste packaging during anaerobic decomposition  

References

1. Tian, Y.; Yao, Y.; Chang, S.; Zhao, Z.; Zhao, Y.; Yuan, X.; Wu, F.; Sun, H. Occurrence and Phase Distribution of Neutral and Ionizable Per- and Polyfluoroalkyl Substances (PFASs) in the Atmosphere and Plant Leaves around Landfills: A Case Study in Tianjin, China. Environ. Sci. Technol. 2018, 52 (3), 1301-1310; 10.1021/acs.est.7b05385.

2. Weinberg, I.; Dreyer, A.; Ebinghaus, R. Landfills as sources of polyfluorinated compounds, polybrominated diphenyl ethers and musk fragrances to ambient air. Atmos. Environ. 2011, 45 (4), 935-941; https://doi.org/10.1016/j.atmosenv.2010.11.011.

3. Ahrens, L.; Shoeib, M.; Harner, T.; Lee, S.C.; Guo, R.; Reiner, E.J. Wastewater Treatment Plant and Landfills as Sources of Polyfluoroalkyl Compounds to the Atmosphere. Environ. Sci. Technol. 2011, 45 (19), 8098-8105; 10.1021/es1036173.