Chlorinated polyfluoroalkyl ether sulfonic acid (known by its commercial name F-53b) and ammonium salt of 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-hepta-fluoropropoxy)-propanoic acid (called GenX), two emerging per- and polyfluoroalkyl substances (PFAS), are widely used to replace the perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA)-related compounds. However, the bioaccumulation potential and toxicity effects of the two emerging PFAS are unknown. Soil is an important sink for persistent organic pollutants, and PFASs in soil may transport to surface water, groundwater, and the atmosphere via different pathways. The fate and transport of emerging F-53B and GenX in soil remains a critical knowledge gap. This research advances the understanding of the environmental behavior of F-53b and GenX and would facilitate the government to establish regulations and practices on their production and uses. <br/><br/>The specific objectives of the research include: (1) to examine the sorption-desorption and degradation mechanisms of F-53b and GenX in soils; (2) to investigate the transport and accumulation of F-53b and GenX under the work of plant and microbe in vadose zone; and (3) to study the long-term environmental impacts of F-53b and GenX with fate and transport models verified with experimental data. The successful completion of this project will benefit society through the generation of new fundamental knowledge that will advance the treatment of PFAS in soil and vadose zones. Additional benefits to society will be accomplished through education and training activities including the mentoring of one graduate student and up to nine underrepresented students.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.