Desert Research Institute (DRI) is the nonprofit research campus of the Nevada System of Higher Education (NSHE) and sister property of the University of Nevada, Reno (UNR), the organization that oversees all publicly supported higher education in the U.S. state of Nevada. At DRI, approximately 500 research faculty and support staff engage in more than $50 million in environmental research each year. DRI's environmental research programs are divided into three core divisions (Atmospheric Sciences, Earth and Ecosystem Sciences, and Hydrologic Sciences) and two interdisciplinary centers (Center for Arid Lands Environmental Management and the Center for Watersheds and Environmental Sustainability). Established in 1988 and sponsored by AT&T, the institute's Nevada Medal awards "outstanding achievement in science and engineering".S.
Studying coastal ecogeomorphic change relies on reliably and accurately dating recent sediment deposits. While a handful of short-lived radioisotopes are proven suitable geochronometers, all have limitations. One particularly useful anthropogenic radionuclide, 137Cs, is rapidly approaching extinction due to its half-life. We evaluate whether the bomb-produced radionuclide 241Am is a reliable alternative to 137Cs. In 75 cores from eight Oregon intertidal zones, 241Am was readily detectable in higher-elevation marsh sediments and, when present, was less mobile post-deposition than 137Cs. Accretion derived from the depth of the 241Am and 137Cs peaks associated with the height of nuclear proliferation were statistically similar to rates determined from excess 210Pb. Although 241Am activities are relatively low in these environments, their detectability is expected to increase as 241Pu continues to decay. 241Am may therefore be an accurate event-horizon chronometer in high marsh sediments, and will likely become an increasingly preferable dating technique compared to 137Cs geochronology.
For over fifty years, the Landsat satellite series has provided continuous and comprehensive data for monitoring changes on the Earth's terrestrial surface. Eight successive missions, carrying progressively more sophisticated sensors, with improved radiometric, geometric, and spatial characteristics, have provided an unbroken series of optical and thermal imagery, unparalleled globally. With limited lifetimes for each Landsat satellite, planning of each mission typically overlaps to ensure continuity. Commencing in 2021, planning of a Landsat-9 successor gathered user needs from across the Earth Observation (EO) community, resulting in the Landsat Next (LNext) mission design of three sun-synchronous satellites to acquire reflective and thermal wavelength observations with two to three times the temporal, spatial, and spectral resolution of previous missions. Proposed 2026 U.S. budgets have significantly reduced NASA Earth Science funding. Alternate architectures are now being investigated for Landsat Next that would only meet Landsat-9 design requirements. While this would provide observation continuity, this implies a revised Landsat Next program launched in the early 2030s with nearly 30 year old capabilities, that may acquire data with lower radiometric quality than the current on-orbit Landsat-8 and 9 missions, and that will not support the new capabilities advocated for by the EO user community. This correspondence serves to raise community awareness that the decision is pending, and outlines the observation requirements originally envisioned for LNext and how they were derived to provide context for evaluating the restructured and descoped capability now being considered.
MXene-based photocatalysts have demonstrated excellent potential for the selective conversion of hazardous nitric oxide (NO). In this work, Ag/AgCl@Bi-MXene nanocomposites were successfully synthesized using a dual-etching-assisted strategy and systematically implemented for the photocatalytic NO removal. Characterization results confirmed the successful anchoring of Ag/AgCl nanoparticles and Bi incorporation onto MXene nano-sheets, resulting in enhanced crystallinity and strong interfacial interactions. The photoluminescence (PL) and electron paramagnetic resonance (EPR) studies demonstrated suppressed charge recombination and surface defect states. Ag/AgCl nanoparticles on Mxene sheets can promote the formation of hot electrons and plasmonic effects, thereby favorably influencing the optical response. The optimized Ag/AgCl@Bi-MXene construction displayed 65.2% of NO removal in 10 min, substantially higher than Bi-MXene (38.6%), Ag/AgCl@MXene (51.4%), and pristine MXene (22.3%). Notably, NO2 byproduct formation remained below 10 ppb, ensuring high selectivity. Quenching and electron spin resonance (ESR) experiments identified photogenerated electrons and O2 center dot- radicals as the dominant reactive species, supported by in-situ diffuse reflectance infrared fourier transform spectroscopy (DRIFTS). Complementary density functional theory (DFT) calculations revealed bandgap alteration, an increased density of states near the Fermi level, and metallic-like behavior induced by Bi and Ag/AgCl, which corroborates the dual plasmonic enhancement and efficient ohmic contact at the Bi-MXene/AgCl interface. These synergistic effects collectively enable superior charge separation, directional electron transport, and light harvesting, establishing Ag/AgCl@Bi-MXene as a promising photocatalyst for light-driven NO abatement.
Water retention properties in frozen soils, including the soil freezing characteristic curve (SFCC), soil water characteristic curve (SWCC), and hydraulic conductivity, are crucial for understanding water infiltration and climate change in cold regions. In this study, a novel experimental system was developed and conducted to simultaneously investigate the SFCC, SWCC, and hydraulic conductivity of sandy soils during the freezing and thawing phases. SFCC and SWCC were measured during freezing and thawing, while hydraulic conductivity was assessed under unfrozen, frozen, and thawing conditions. The results showed that supercooling effects cause a freezing point suppression of approximately 2 degrees C, with significant hysteresis observed in SFCC and SWCC, especially at 100 % initial saturation (Sr,i). The ice-entry value (IEV) during freezing was determined to be inversely proportional to Sr,i, with values decreasing by up to 25 % as Sr,iincreased from 50 % to 100 %. Hydraulic conductivity during freezing was significantly lower than in thawing or unfrozen states, decreasing by up to 80 % at Sr,i >= 30 % due to pore ice formation. Differences in the IEV and air-entry value (AEV) between freezing and thawing phases were attributed to latent heat exchanges during phase transitions. This study highlights the interconnected behaviors of SFCC, SWCC, and hydraulic conductivity under freeze-thaw cycles. These findings enhance our understanding of soil behavior under freeze-thaw cycles and provide critical data for improving water infiltration models in frozen soils.
Light absorption by brown carbon (BrC) represents a major uncertainty in assessing the climatic effects of carbonaceous aerosols. Using 38,622 PM2.5 samples collected from the U.S. Chemical Speciation Network (2016-2018) and analyzed by a multiwavelength thermal/optical analyzer (TOA), we applied an enhanced spectral/mass balance receptor model to quantify black carbon (BC), BrC, and nonabsorbing white carbon (WtC) while allowing BrC optical properties to vary across samples. The model achieved excellent fits (r(2) > 0.98) and revealed a wide range of BrC absorption & Aring;ngstrom exponent (AAE(405-635 nm) = 2.13 +/- 0.74) and mass absorption efficiency (MAE(532 nm) = 2.03 +/- 0.35 m(2) g(-1)). An inverse AAE-MAE relationship was found, with strongly to moderately absorbing BrC being the most prevalent BrC classes. Seasonal patterns showed higher "organic brownness" (i.e., higher BrC mass fraction in organic carbon regardless of BrC class) but lower MAE in winter and the opposite in summer, reflecting the bleaching evolution of BrC with photochemical aging. BrC abundance also influenced the reconciliation between BC- and TOA-derived elemental carbon, likely through altered thermal-optical carbon analysis splits. This study provides the first nationwide characterization of BrC optical variability from national network data, establishing a scalable framework toward long-term monitoring of organic aerosol absorption within existing regulatory programs.
