John Hribljan | Geology Reports

USGS2026

Aging of biosolids in fields prolongs the release of biosolid-borne PFAS and promotes the release of select PFCA in water

Land application of biosolids can introduce PFAS into croplands. Biosolids transported to surface waters through runoff may subsequently release PFAS into aquatic environments. The objective was to evaluate the effects of the aging of biosolids and the presence of sediment on the release of biosolid-borne PFAS to water at the water-sediment interface under anaerobic conditions. Through two independent rounds of microcosm experiments, we demonstrate that by day 136, most of the PFAS compounds (e.g., perfluorocarboxylic acids, or PFCAs) released <10 ng per g biosolids dry weight, except for 5:3 FTCA. Kinetically, the aging process substantially delayed the release of some long-chain PFAS (i.e., PFNA, PFDA, and PFOS) to water, due to the collapse of the porous structure of biosolids during aging. After day 136, the amount of long-chain PFAS released from aged biosolids reached levels similar to those released from the fresh biosolids due to the recovery of the pore structure during the release experiment. Mass balance analysis showed considerably higher, final masses of PFPeA, PFHxA, and PFOA than their initial masses, suggesting that precursors were biotransformed into these compounds during the release experiment, and biosolid aging led to elevated biotransformation and release of these three PFCAs. Sediment had little effect on the kinetics or extent of PFAS release from biosolids, except that the extent of FTCA release was reduced in the presence of sediment potentially due to adsorption. Overall, biosolid aging can delay the release of long-chain PFAS and promote the biotransformation to and release of PFCAs.

Water Research↗

USGS2022

Variation in carbon and nitrogen concentrations among peatland categories at the global scale

Peatlands account for 15 to 30% of the world’s soil carbon (C) stock and are important controls over global nitrogen (N) cycles. However, C and N concentrations are known to vary among peatlands contributing to the uncertainty of global C inventories, but there are few global studies that relate peatland classification to peat chemistry. We analyzed 436 peat cores sampled in 24 countries across six continents and measured C, N, and organic matter (OM) content at three depths down to 70 cm. Sites were distinguished between northern (387) and tropical (49) peatlands and assigned to one of six distinct broadly recognized peatland categories that vary primarily along a pH gradient. Peat C and N concentrations, OM content, and C:N ratios differed significantly among peatland categories, but few differences in chemistry with depth were found within each category. Across all peatlands C and N concentrations in the 10–20 cm layer, were 440 ± 85.1 g kg -1 and 13.9 ± 7.4 g kg -1 , with an average C:N ratio of 30.1 ± 20.8. Among peatland categories, median C concentrations were highest in bogs, poor fens and tropical swamps (446–532 g kg -1 ) and lowest in intermediate and extremely rich fens (375–414 g kg -1 ). The C:OM ratio in peat was similar across most peatland categories, except in deeper samples from ombrotrophic tropical peat swamps that were higher than other peatlands categories. Peat N concentrations and C:N ratios varied approximately two-fold among peatland categories and N concentrations tended to be higher (and C:N lower) in intermediate fens compared with other peatland types. This study reports on a unique data set and demonstrates that differences in peat C and OM concentrations among broadly classified peatland categories are predictable, which can aid future studies that use land cover assessments to refine global peatland C and N stocks.

PLoS ONE↗