Citrate is an important component of metal processing effluents such as chemical mechanical planarization wastewaters of the semiconductor industry. Citrate can serve as an electron donor for sulfate reduction applied to promote the removal of metals, and it can also potentially be used by methanogens that coexist in anaerobic biofilms. The objective of this study was to evaluate the degradation of citrate with sulfate-reducing and methanogenic biofilms. During batch bioassays, the citrate, acetate, methane and sulfide concentrations were monitored. The results indicate that independent of the biofilm or incubation conditions used, citrate was rapidly fermented with specific rates ranging from 566 to 720 mg chemical oxygen demand (COD) consumed per gram volatile suspended solids per day. Acetate was found to be the main fermentation product of citrate degradation, which was later degraded completely under either methanogenic or sulfate reducing conditions. However, if either sulfate reduction or methanogenesis was infeasible due to specific inhibitors (2-bromoethane sulfonate), absence of sulfate or lack of adequate microorganisms in the biofilm, acetate accumulated to levels accounting for 90-100% of the citrate-COD consumed. Based on carbon balances measured in phosphate buffered bioassays, acetate, CO(2) and hydrogen are the main products of citrate fermentation, with a molar ratio of 2:2:1 per mol of citrate, respectively. In bicarbonate buffered bioassays, acetogenesis of H(2) and CO(2) increased the yield of acetate. The results taken as a whole suggest that in anaerobic biofilm systems, citrate is metabolized via the formation of acetate as the main metabolic intermediate prior to methanogenesis or sulfate reduction. Sulfate reducing consortia must be enriched to utilize acetate as an electron donor in order to utilize the majority of the electron-equivalents in citrate.

No abstract

There is a need for effective, environmentally compatible photoacid generators (PAGs) for application in photolithography for microelectronic device fabrication. Perfluoroalkyl sulfonates (PFAS) used in conventional PAG formulations, such as perfluorooctane sulfonate (PFOS), are under increasing scrutiny due to their widespread environmental distribution and toxicity. Recently, two new PFAS-free, PAG anions with semifluorinated sulfonate anions containing biomolecules (γ-butyrolactone or D-glucose groups) were successfully applied as PAGs. In this study, the biodegradation potential, cytotoxicity, and physicochemical treatability of the new PAG anions was evaluated. PFOS and perfluorobutane sulfonate (PFBS) were used as reference materials in all of the assays. The new PAGs were susceptible to partial degradation by microorganisms in aerobic activated sludge, and these were also readily removed by chemical oxidative treatment with Fenton's reagent [H(2)O(2)/Fe(II)]. In contrast, the compounds were resistant to microbial and chemical attack under reductive conditions as indicated by the low removal efficiencies observed with anaerobic biodegradation assays and chemical assays with zero-valent iron, respectively. The enhanced biodegradation potential and treatability make of the new PAGs attractive materials to resolve current issues related to the lithographic performance and environmental concerns.

The Hook-billed Kite (Chondrohierax uncinatus) is a specialized and secretive Neotropical raptor that has received little research attention. Despite scattered records of Hook-billed Kite movements, this species was long thought to be non-migratory. We studied the southbound autumn migration of Hook-billed Kites in Veracruz, Mexico, and Belize and investigated whether environmental conditions on their breeding grounds influenced migration. We collected migration count data over 8 years (2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020) in Belize and 25 years (1995-2019) in Veracruz. In Belize, we recorded 39,928 Hook-billed Kites on their southbound autumn migration during a total of 3093.1 count hours, with an autumn seasonal mean (±SE) count of 4991 ± 1083 kites/year, with flocks consisting of up to 200 individuals. In comparison, during a total of 42,531 count hours at two count sites in Veracruz, we recorded 3870 Hook-billed Kites with a seasonal mean (±SE) count of 154.8 ± 12.1 kites/year. Most kites in Veracruz migrated as single individuals or groups of < 4 birds and the largest flock ever recorded had 12 individuals. The mean 95% seasonal passage window of Hook-billed Kites in Belize lasted 44.9 ± 2.5 d (N = 8 years) from 26 October to 9 December compared to an earlier passage from 13 September-11 November in Veracruz (N = 25 years). Precipitation on the breeding grounds had no influence on the timing or magnitude of the kite migration through Belize; whereas, in Veracruz, migration timing occurred later as precipitation north of the count site increased. Notably, age, sex, and color morph classes migrated in mixed flocks; therefore, we detected no signs of differential migration, which is uncommon among raptors. Our study describes, for the first time, the largest known southbound autumn migration of Hook-billed Kites. Working to understand the life histories of tropical raptors provides critical ecological information, which can aid in identifying potential threats, conservation needs, and population statuses.RESUMEN. Chonrrohierax uncinatus es una ave rapaz Neotropical especializada y sigilosa que ha recibido poca atención en la investigación. A pesar de los registros dispersos de los movimientos de C. uncinatus, por largo tiempo se ha pensado que esta especie no es migratoria. Estudiamos la migración de otoño hacia el sur de C. unicnatus en Veracruz, México y Belice e investigamos si las condiciones ambientales en la zona de reproducción influencian la migración. Colectamos datos de conteos migratorios durante 8 años (2013-2020) en Belice y 25 años en Veracruz. En Belice registramos 39,928 individuos durante su migración de otoño hacia el sur durante un total de 3093.1 horas de conteo, con un promedio de los conteos de otoño estacionales (±SE) de 4991 ± 1083 aves/ año, con bandadas compuestas por hasta 200 individuos. En comparación, durante un total de 42,531 horas de conteo en dos sitios en Veracruz, registramos 3870 C. uncinatus con un promedio en los conteos estacionales (±SE) de 154.8 ± 12.1 ave...