Universidad Estatal de Sonora

The increasing prevalence of organic pollutants such as rhodamine B (RB), p-nitrophenol (PNP), ciprofloxacin (CPX), ibuprofen (IBP) and paracetamol (PCT) in water sources necessitates the development of effective and sustainable degradation technologies.Herein, Santa Barbara Amorphous-15 (SBA-15) supported silica was impregnated with iron (Fe) nanoparticles using the wet-incipient volume impregnation method, followed either by drying (Fe/SBA-15 D) or calcination (Fe/SBA-15 C).The organic pollutant-degrading performance of these catalysts was evaluated via photolysis and heterogeneous photo-catalysis and photo-Fenton process under ultra-violet (UV) irradiationCharacterization via X-ray diffraction confirmed the preservation of the mesoporous structure of SBA-15 after Fe impregnation.The presence of iron oxide nanoparticles was identified, particularly in Fe/SBA-15 C.Nitrogen adsorption-desorption analyses revealed a decrease in the sp. surface area, indicating the partial filling of SBA-15 pores with Fe species.UV-visible diffuse reflectance spectroscopy showed a reduction in the bandgap energy after the incorporation of Fe, which enhanced photo-catalytic activity.X-ray photo-electron spectroscopy results revealed that Fe/SBA-15 D contained a high proportion of Fe²⁺, whereas Fe/SBA-15 C exhibited excess Fe³⁺.Fe/SBA-15 D with hydrogen peroxide (H₂O₂) degraded RB, PNP, IBP and PCT with high efficiency, while Fe/SBA-15 C was substantially effective for CPX degradationThe maximum degradation% of RB, PNP, CPX, IBP and PCT were 100 %, 99.45 %, 91.54 %, 86.08 % and 86.11 %, resp.These results are attributed to the generation of hydroxyl radicals (•OH) facilitated by the synergistic effect of a highly concentrated Fe²⁺ with H₂O₂ and the presence of sulfate (SO^2-₄) ions, which serve as active sites and electron-hole traps.This study confirms that •OH radicals are the primary reactive species responsible for the effective degradation of target organic pollutants.

Climate change is a global phenomenon affecting species, which in arid regions will translate into more frequent and intense periods of drought. The Sonoran Desert is becoming hotter and drier, and many organisms are rapidly changing in abundance and distribution. These population attributes depend directly on the dynamics of the population, which in turn depends on the vital rates of its individuals; yet few studies have documented the effects of climate change on the population dynamics of keystone species such as the saguaro cactus (Carnegiea gigantea). Although saguaros have traits that enable them to withstand present environmental conditions, climate change could make them vulnerable if forced beyond their tolerance limits.

We evaluated the effect of climate change on 13 saguaro populations spanning most of the species’ distribution range. Using field data from 2014 to 2016, we built an integral projection model (IPM) describing the environmentally explicit dynamics of the populations. We used this IPM, along with projections of two climate change scenarios and one no-change scenario, to predict population sizes (N) and growth rates (λ) from 2017 to 2099 and compared these scenarios to demonstrate the effect of climate change on the future of saguaro cactuses.

We found that all populations will decline, mainly due to future increases in drought, mostly hindering recruitment. However, the decline will be different across populations, since those located near the coast will be affected by harsher drought events than those located further inland.

Our study demonstrates that climate change and its associated increase in drought pose a significant threat to the saguaro cactus populations in the Sonoran Desert. Our findings indicate that the recruitment of saguaros, vital for establishing new individuals, is particularly vulnerable to intensifying drought conditions. Importantly, regional climate trends will have different impacts on saguaro populations across their distribution range.

This work provides the first description of the synthesis and characterization of polymeric nanoparticles (NPs) obtained by polyelectrolyte complexes (PECs) of three polysaccharides: chitosan (Cs) or its catecholic derivative, ulvan, and hyaluronic acid (HA). The carbodiimide method used catechol group conjugation onto the Cs backbone using the catechol-containing compound hydrocaffeic acid. A degree of substitution of 2.98% was determined by spectroscopy in the chitosan-catechol (CsC) conjugate. DLS studies showed hydrodynamic diameter (D _h) close to 300 nm for PECs of Cs and CsC with ulvan, with positive zeta potential for both complexes. HA coating was confirmed by obtaining negative zeta potential. The HA coating reduced the D _h values of the materials by approximately 100 nm. This resulted in maintaining stability in water suspension for up to 8 weeks, yielding unimodal size distribution. ATR-FTIR spectra confirmed the presence of the polyelectrolytes in the PECs. FE-SEM studies demonstrated that HA-coated NPs exhibited smaller sizes than their uncoated counterparts. PECs with CsC maintained higher free radical scavenging activity than those with unmodified Cs, with the HA coating only reducing antioxidant activity by 16%. All tested NPs demonstrated biocompatibility at concentrations up to 200 μg/mL in ARPE-19 cell cultures derived from human retinal pigment epithelial cells.