Ultraviolet Intensity Research Articles

Which factors mainly drive the photoaging of microplastics in freshwater?

Light irradiation is considered as most important process for the aging of microplastics (MPs); however, which factors drive the process is still unknown. This study investigated the role of typical environmental factors including ultraviolet (UV), oxygen, temperature and physical abrasion in the photoaging of polystyrene (PS) in freshwater. Results showed that UV irradiation and abrasion were dominant factors for affecting photoaging of PS based on dynamic analysis in the property of MP itself and leachate. Especially, when both factors worked together on MPs, they caused more destructive effect. Mechanical exploration revealed that photoaging of MPs was mainly controlled by reactive oxygen species (ROS, 1O2) generated from the reaction of dissolved oxygen/water molecules with polymer radicals initiated by UV energy. As an attacker on MPs, ROS formation was significantly linked with UV intensity, highlighting the important role of UV. The fragmentation was correlated to abrasion intensity, where a higher abrasion generated stronger physical force to tear MPs into fragments. The low roles of oxygen and temperature were presumably related to multiple effects of ROS formation and UV absorption. The findings firstly clarify the drivers in the photoaging of MPs, and contribute our effort to assess their fate and pollution risk in the environment.

Topically applied bacteriophage to control multi-drug resistant Pseudomonas aeruginosa-infected wounds in a New Zealand rabbit model.

Pseudomonas aeruginosa (P. aeruginosa) is a widespread, gram-negative, pathogenic bacterium that causes serious internal and external infections in humans and other animals. The increasing antibiotic resistance has complicated bacterial infection treatment, and current antibiotic therapies cannot cure all infections. Owing to this, bacteriophages (phages) have regained attention as potential therapeutics for bacterial infections. In this study, the phage "PaVOA" was isolated from hospital sewage and characterized. Next, a New Zealand rabbit skin infection model was used to determine the therapeutic efficacy of PaVOA as compared to a phage cocktail or the cephalosporin antibiotic ceftriaxone. Characterization results demonstrated that phage PaVOA belongs to the Myoviridae family, has a double-stranded DNA genome, is resistant to low temperatures (-20°C), is most optimal at 40°C, has good acid-base tolerance, and remains stable for 30 min under 20 W ultraviolet (UV) intensity. The optimal multiplicity of infection of PaVOA was 0.1, and a one-step growth curve showed a short latency period (10 min), thus demonstrating its ability to rapidly kill bacteria. Furthermore, the addition of calcium (Ca) and magnesium (Mg) ions significantly increased the PaVOA titer. An in vivo phage kinetic curve showed that PaVOA was rapidly inactivated within the blood of New Zealand rabbits (undetectable after 12 h), and no animals died due to phage treatment. Wound healing studies showed that the phage cocktail induced a high healing rate and an acceleration of the skin remodeling process, and was more efficacious than ceftriaxone. Therefore, phage cocktail therapy represents a novel therapeutic approach in the treatment of traumatic skin infections caused by multi-drug resistant P. aeruginosa.

Distribution, Risk, and Influencing Factors of Microplastics in Surface Water of Huangshui River Basin

In order to explore the distribution of microplastics in the freshwater environment of Qinghai-Tibet Plateau, 63 surface water samples were collected in Huangshui River basin of Qinghai province during the wet season, and the distribution characteristics and main influencing factors of microplastics in the surface water were analyzed by means of metallographic microscope, Fourier infrared spectroscopy, field investigation, and image data analysis. The potential ecological risks of microplastics were evaluated using risk index (H) and pollution load index (PLI) models. The abundance of microplastics in surface water ranged from 665-8780 n·m-3, with the highest average abundance of 5414 n·m-3 in Huangyuan County. The abundance of microplastics increased from upstream to downstream. The main colors of microplastics were transparent (67%) and black (17%), and the particle size was less than 50 μm (70%). Polyethylene (66%) and polypropylene (12%) were the main polymer types. The abundance of microplastics was positively correlated with cultivated land area, precipitation, and ultraviolet intensity, but the opposite results were observed in dissolved oxygen, redox potential, and wind speed. Additionally, the potential ecological risk of surface water in the Huangshui River basin was relatively low.

Floral ultraviolet absorbance area responds plastically to ultraviolet irradiance in Brassica rapa.

Solar ultraviolet (UV) radiation is known to have significant effects on the development and performance of plants, including flowers. In multiple species, UV-absorbing floral patterns are associated with environmental conditions such as the solar UV exposure they typically receive. However, it is not known whether plants can increase the UV-absorbing areas found on petals plastically when in a high-UV environment. We grew Brassica rapa at three different UV radiation intensities (control, low, and high) and under two exposure duration regimes. We removed petals from flowers periodically during the flowering period and measured the proportion of the petal that absorbed UV. UV-absorbing areas increased when plants were exposed to longer periods of UV radiation, and at high UV radiation intensities. UV-absorbing area of petals of the UV intensity treatments decreased over time in long exposure plants. This study demonstrates that flowers can potentially acclimate to different UV radiation intensities and duration of exposure through an increase in UV-absorbing areas even after a relatively short exposure time to UV. Such a rapid plastic response may be especially beneficial for dynamically changing UV conditions and in response to climate change.

Development of a geometrical model for the determination of the average intensity in a flow-through UV-LED reactor and validation with biodosimetry and actinometry

Ultraviolet (UV) treatment is widely used for water disinfection. The recent development and improvement of the light emitting diodes (LEDs) in the UVC range makes them an alternative to the traditional mercury vapor UV lamps in the middle or long term. Determining the UV intensity applied by a reactor is essential for evaluating its efficacy. Although doing so is relatively straightforward in simple laboratory reactors, such as a collimated beam reactor (CBR), its calculation for more complex devices, such as a flow-through reactor (FTR), requires indirect approaches. The objective in this study is determining the UV intensity in FTRs equipped with UV-C LEDs by utilizing indirect approaches such as the geometrical modeling of the intensity distribution, chemical actinometry, and biodosimetry using a CBR as a reference. With this method, the inactivation of four bacterial indicators in both the CBR and FTR have also been addressed. The three approaches that were used reported similar values of mean intensity with an average value of 0.86 mW cm−2. Determining the mean intensity enabled calculating the UV doses that were applied to the target water and then determining the inactivation kinetics parameters. The UV dose that was necessary to achieve four-log reductions from the initial bacterial concentration ranged from 5.8 to 17.5 mJ cm−2 depending on the target species. Additionally, the geometrical model developed in this study introduces new possibilities into the optimization of the reactor design.

The Ultraviolet C ii Lines as a Diagnostic of κ-distributed Electrons in Planetary Nebulae

Non-Maxwellian κ electron energy distributions (EEDs) have been proposed in recent years to resolve the so-called “electron temperature and abundance discrepancy problem” in the study of planetary nebulae (PNs). Thus the need to develop diagnostic tools to determine from observations the EED of PNs is raised. Arising from high-energy levels, the ultraviolet (UV) emission lines from PNs present intensities that depend sensitively on the high-energy tail of the EED. In this work, we investigate the feasibility of using the C ii]λ2326/C ii λ1335 intensity ratios as a diagnostic of the deviation of the EED from the Maxwellian distribution (as represented by the κ index). We use a Maxwellian decomposition approach to derive the theoretical κ-EED-based collisionally excited coefficients of C ii, and then compute the C ii UV intensity ratio as a function of the κ index. We analyze the archival spectra acquired by the International Ultraviolet Explorer and measure the intensities of C ii UV lines from 12 PNs. By comparing the observed line ratios and the theoretical predictions, we can infer their κ values. With the Maxwellian-EED hypothesis, the observed C ii]λ2326/C ii λ1335 ratios are found to be generally lower than those predicted from the observed optical spectra. This discrepancy can be explained in terms of the κ EED. Our results show that the κ values inferred range from 15 to infinity, suggesting a mild or modest deviation from the Maxwellian distribution. However, the κ-distributed electrons are unlikely to exist throughout the whole nebulae. A toy model shows that if just about 1%–5% of the free electrons in a PN had a κ EED as small as κ = 3, it would be sufficient to account for the observations.

Disinfection performance of an ultraviolet lamp: a CFD investigation

Ultraviolet (UV)-based devices have shown their effectiveness on various germicidal purposes. To serve their design optimisation, the disinfection effectiveness of a vertically cylindrical UV lamp, whose wattage ranges from P = 30 − 100 W, is numerically investigated in this work. The UV radiation is solved by the Finite Volume Method together with the Discrete Ordinates model. Various results for the UV intensity and its bactericidal effects against several popular virus types, i.e., Corona-SARS, Herpes (type 2), and HIV, are reported and analysed in detail. Results show that the UV irradiance is greatly dependent on the lamp power. Additionally, it is indicated that the higher the lamp wattage employed, the larger the bactericidal rate is observed, resulting in the greater effectiveness of the UV disinfection process. Nevertheless, the wattage of P ≤ 100W is determined to be insufficient for an effective disinfection performance in a whole room; higher values of power must hence be considered in case intensive sterilization is required. Furthermore, the germicidal effect gets reduced with the viruses less sensitive to UV rays, e.g, the bactericidal rate against the HIV virus is only ∼8.98% at the surrounding walls.

A naphthalimide-based fluorescent probe for quantitative sensing of UV light

Developing ultraviolet (UV) sensors that can visualize UV light in the environment for productive life has been widely practiced. A challenging problem that arises in this domain is the quantitative analysis of UV light. In this study, we identified a novel naphthalimide derivative, NDGF, which can undergo decomposition to various degrees when irradiated by UV light with different intensities, so as to produce corresponding fluorescence intensities. Moreover, NDGF was prepared as a UV-responsive film NDGF-PEO which also has outstanding competence in the quantification of UV intensity. The surprising thing is that this novel UV-responsive decomposition mechanism of NDGF has been demonstrated and has great potential to open new doors for the development of naphthalimide-based photocages and novel UV quantitative sensors.

Regression models for predicting the die-off rate of E. coli in solar water disinfection

Abstract Solar disinfection (SODIS) is an economical and user-friendly method of water purification mostly applied in the tropical countries. SODIS uses the ultraviolet (UV) and temperature effects of the sun to kill pathogens in drinking water. The objective of the study was to develop a functional relationship between pathogen die-off rate and SODIS treatment conditions, namely daily maximum of 5-h averages of UV intensity , daily maximum water temperature , and water turbidity . Regression analyses/models based on 5-month data revealed that although and can be excellent predictors of pathogen die-off rate, their variable inflation factors (6.75 and 6.57, respectively), which is a measure of dependence between the two variables and adequacy of the estimated regression coefficients, suggest that they cannot be successfully combined in a single least-square regression model. was found to be a better predictor of in SODIS than . Water turbidities in the range of 1–30 NTU had no significant effect on the pathogen die-off rate. The study concluded that regression models/analyses can be successfully employed to explain the day-to-day variability in pathogen die-off rate, predict SODIS applicability, and exposure period in different regions of the world based on UV, water temperature, and water turbidity.

Photodegradation of oxytetracycline by UV-assisted persulfate and percarbonate processes: kinetics, influencing factors, anion effect, and radical species.

In this study, the performance of ultraviolet (UV)-assisted persulfate (PS) and percarbonate (PC) oxidation processes in oxytetracycline (OTC) removal was investigated. UVC lamps were used for the photolysis process and the effect of operating parameters (initial pH, oxidant dose, initial OTC concentration, UV intensity) on OTC removal efficiency was determined. Control experiments were carried out at pH 5.5 and 32W UV power for 60min by adding a 4mM oxidant with 10mg/L initial OTC concentration. The OTC removal efficiency obtained as a result of only photolysis was 17.3% and the removal efficiency obtained by PS and PC oxidation alone was 18.3% and 12.7%, respectively. The OTC removal efficiencies increased in the combined processes and reached 58.1% and 69.9% for the UV-PS and UV-PC processes, respectively. The reaction rates of the processes were ranked as UV-PC > UV-PS > PS > UV > PC. In the UV-PS and UV-PC processes, the highest removal efficiencies were achieved at alkaline pH values. The OTC removal efficiency was increased with the increase in oxidant dose; however, the efficiency decreased after a certain dose due to the scavenging effect. The removal efficiency also increased as the initial OTC concentration decreased. The UV intensity had a positive effect on OTC removal efficiency. The effect of the water matrix on OTC removal efficiency was investigated while the dominant radical types were determined in UV-assisted processes. The EE/O values for the UV-PS and UV-PC processes were calculated as 211 kWh/m3 and 153 kWh/m3, respectively for 60min of reaction time. Although similar removal efficiencies were obtained with both UV-assisted processes, the UV-PC process steps forward in terms of being a novel, environmentally friendly, more economic, and promising technology for OTC removal.

Ultraviolet‐Sensitive OLED with Tunable Wavelength and Intensity by Integrated ZnO Nanowires Schottky Junction

AbstractOrganic light‐emitting diode (OLED) displays are one of the dominant flat panel display technologies. Here, a novel ultraviolet (UV)‐sensitive OLED (USO) is reported, which emits visible light with adjustable wavelength and brightness according to the intensity of the incident UV light. The USO employs zinc oxide nanowires (ZnO NWs) with Schottky junctions to control current and engages exciplex‐emitting OLED to emit light according to the incident UV light. As the UV light intensity increases from 0.09 to 8.15 mW cm−2, USO emits light with a peak wavelength that ranges from 595 to 525 nm, a color coordinate from (0.458, 0.485) to (0.339, 0.555), and a light intensity that is anywhere from 97 to 6915 cd m−2. The USO has a fast photoresponse characteristic due to the effect of the Schottky barrier introduced by the close contact of the ZnO NWs and gold electrodes. The luminescence color of the USO changes from dark orange to harsh green because of the exciplexes’ different formation ratios under differing UV intensities. As a result of the USO taking advantage of the Schottky barrier and exciplex, the realization of many innovative applications in optoelectronic devices is possible.

Determination of glucosamine and galactosamine in food by liquid chromatography with pre-column derivatization

ABSTRACT A pre-column derivatization liquid chromatographic method was developed for the simultaneous determination of both glucosamine and galactosamine in selected food samples. The derivatization of glucosamine and galactosamine with 9-fluorenylmethoxycarbonyl chloride was accomplished under alkaline conditions and UV irradiation. When the detection wavelength was 265 nm and acetonitrile-0.1% phosphoric acid was the mobile phase at a flow rate of 1.0 mL/min, the linear range of ultraviolet intensity of glucosamine and galactosamine was 10–100 μg/mL,correlation coefficient of glucosamine was 0.9994 and correlation coefficient of galactosamine was 0.9993. The standard recovery of three kinds of food was in the range of 94.09–114.5%, the relative standard deviation (RSD) was 0.38–5.29%, the detection limit was 1.0 mg/kg, and the quantitative limit was 4.0 mg/kg. The results of this research indicate that this method is suitable for the simultaneous determination of glucosamine and galactosamine in food.

Optical properties of broadband reflection of cholesteric liquid crystal by thermal diffusion of benzotriazoles.

Polymer stabilized cholesteric liquid crystal broadband reflective films are prepared by the thermal diffusion of a benzotriazoles organic ultraviolet (UV) absorber (UV-327) combined with photopolymerization. A gradient of UV intensity is established in the direction of film thickness, inducing the formation of a pitch gradient distribution, thus broadening the reflected bandwidth. The effects of UV-327 concentration, UV irradiation intensity, irradiation time, polymerization temperature, and C6M concentration on the reflected bandwidth of the sample are examined in detail. The results indicate that the diffusion method of the organic UV absorber enables the reflected bandwidth to be broadened under appropriate conditions.

Direct Visualization of UV-Light on Polymer Composite Films Consisting of Light Emitting Organic Micro Rods and Polydimethylsiloxane.

We experimentally demonstrate the direct visualization of ultraviolet (UV) light using flexible polymer composite films consisting of crystalline organic tris-(8-hydroxyquinoline) aluminum (Alq3) micro-rods and polydimethylsiloxane (PDMS). The representative organic mono-molecule Alq3, which is a core material of organic light-emitting diodes, was used to detect light in the invisible UV region and visualize photoluminescence (PL). Alq3 shows absorption in the UV region and light-emitting characteristics in the green region, making it an optimal material for UV visualization because of its large Stokes transition. Crystalline Alq3 micro-rods were fabricated in a deionized water solution through a sequential process of reprecipitation and self-assembly. Highly bright photoluminescence was observed on the highly crystalline Alq3 micro-rods under UV light excitation, indicating that the crystalline structures of Alq3 molecules affect the visible emission decay of excitons. The Alq3 micro-rods were manufactured as flexible polymer composite films using a PDMS solution to observe UV photodetector characteristics according to UV intensity, and it was confirmed that the intensity of the fine UV light reaching the earth’s surface can be visualized by making use of this UV photodetector.

Impacts of haze on the photobleaching of chromophoric dissolved organic matter in surface water

Sunlight plays an important role in the photochemical processes of chromophoric dissolved organic matter (CDOM), which is closely related to water self-purification and primary productivity of healthy aquatic ecosystem health. The fine particles of haze, a widespread air pollutant, absorb natural ultraviolet (UV) irradiation and have an unknown degree of influence on the photochemical transformation of CDOM. Here, an in-situ experiment investigating how the amount and composition of CDOM changes under hazy conditions was conducted in Ningbo, southeastern China, a city that frequently suffers from seasonal haze pollution. The results indicated that haze attenuated UV light under different weather conditions. The UV intensities were reduced from 1124.90 ± 91.58 to 510.26 ± 40.26 μW cm-2 and 748.54 ± 101.68 to 316.32 ± 40.48 μW cm-2 on sunny and cloudy days, respectively; these values approached those on rainy days (186.97 ± 28.58 μW cm-2). Consequently, the loss of dissolved organic carbon during the irradiation test was reduced on hazy days (e.g., from 5.63% to 2.59% on sunny/hazy days). The impact of haze on CDOM photobleaching was further assessed by an excitation-emission matrix (EEM) combined with parallel factor (PARAFAC) analysis. On hazy days, the EEM-PARAFAC components were saved from photobleaching to different degrees; and humic-like substances showed a stronger protective effect from haze than protein-like substances because of their higher photosensitivity. Consequently, haze could cause more terrestrial CDOM to remain in surface water. UV intensity played a critical role in the composition characteristics of CDOM. This study identifies the linkage between atmospheric pollution and water quality and demonstrates that long-term and large-scale haze may adversely influence aquatic ecology through pollutant/nutrient accumulation.

Skin‐Mimicking, Stretchable Photodetector for Skin‐Customized Ultraviolet Dosimetry

AbstractDespite extensive research on photoelectric sensors that typically output signals to indicate the transient ultraviolet (UV) intensity, developing wearable, electrometric photodetectors that can reveal the cumulative UV exposure remains challenging. Here, an organic–inorganic hybrid bulk heterojunction (BHJ) is used to construct a skin‐mimicking, wearable photodetector, based on conductive polymer sensitized with semiconducting nanoparticles. Owing to the UV‐induced reduction reactions, the BHJ photodetectors (PDs) can long remember the UV radiation previously exposed. Moreover, based on the solution processability of bulk heterojunction blends and rich surface functional groups of polydopamine, BHJ PDs can fully inherit the ultraflexibility from electrospun fiber‐networked structure. Thus, this fiber‐configured photodetector is working well even at the strains of up to 60%. Without requiring any complicated analytical tool, its memory effect and simple‐to‐process output facilitate the working mechanism of power‐free UV monitor, while catering to the individual need of different skin types. This work combines the bottom materials design to the top device application, pointing out a new direction in wearable UV sensor technologies.

Simulation and Optimization of the Combined High-Gradient Magnetic Separation-Ultraviolet Photocatalysis (HGMS-UV/TiO2) System for Ballast Water Treatment

Ballast water has a negative impact on marine environment; the existing combined ultraviolet (UV) filtration system that for treating ballast water has relatively low effective rate and instability in inactivating microorganisms. In this study, the established high gradient magnetic separation-ultraviolet photocatalysis (HGMS-UV/TiO2) system was taken, the back propagation (BP) neural network and TracePro was used to simulate and analyse the UV field intensity in the system for optimizing. Further experimental verification was carried out with seawater sample to measure its inactivation effects on microorganisms including zooplankton, phytoplankton and bacteria. The results showed that HGMS-UVC/TiO2 system had good inactivation effect on zooplankton and bacteria, but relatively poor inactivation effect on phytoplankton. The optimal strategy for optimizing the UV intensity was further obtained, it is concluded that after adding ultraviolet A (UVA), the UV intensity distribution of the system is more uniform, and the average illumination intensity is also improved, but the optical path of UV in ballast water should not be too long. The optimized system could increase the intracellular K+ leakage of phytoplankton cells by more than 25%, indicating that the damage to cell membrane permeability was stronger. In conclusion, the optimized HGMS-UVA/UVC/TiO2 system can improve the inactivation capacity of microorganisms and provide basic theoretical support for improving the capacity and level of treatment in ballast water.

Investigation of Cinnamaldehyde Derivatives as Potential Organic UV Filters

Long-term exposure to ultraviolet (UV) rays has been attributed to irreversible health defects at the cellular level. Most importantly, damage to DNA by UVA and UVB rays can result in uncontrolled cellular growth, leading to skin cancer. As a result, topical treatments have been developed over time to protect the skin from UVA and UVB rays. The active ingredients in sunscreens or sun creams are sometimes unsaturated, aromatic organic compounds capable of absorbing harmful UV photons at a great range of wavelengths. Absorption capabilities of these species depend on their degree of conjugation and their molar absorptivity. With this knowledge, two cinnamaldehyde derivatives were synthesized into five potential organic UV filters by the aldol condensation reaction. The products were identified using nuclear magnetic resonance (NMR) and attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopies, and ultraviolet-visible (UV-vis) spectroscopy was used to determine the UV absorption range and intensity of absorption for each compound. Since the compounds would hypothetically be utilized in topical ointments to aide in skin protection, these compounds were assessed in the presence of Pseudomonas aeruginosa, a representative bacterium of the skin’s natural flora. A time-course assay was conducted to detect growth effects of P. aeruginosa in the presence of the organic compounds. According to the spectroscopic and bacterial analyses of these UV-blocking compounds, three compounds were determined to be potential UV filters that cover UVA region while demonstrating no apparent harm to the natural skin bacteria P. aeruginosa, while the other two likely diminished bacterial growth by simple niche inhibition.

Removal effect and mechanism of typical pharmaceuticals and personal care products by AAO-MBR and UV/Chlorine in black water

Pharmaceuticals and personal care products (PPCPs) are emerging pollutants that have gradually attracted the attention of researchers. PPCPs in urban sewage treatment plants mainly originate from human excreta, while water that is mainly composed of human excreta and flushing water is referred to as black water. Based on a traditional anaerobic-anoxic-oxic-membrane bioreactor (AAO-MBR) design, we optimized the strategy of prolonging the anaerobic-anoxic section length and tested its effect on the bioreactor's efficiency in removing conventional pollutants and PPCPs from blackwater. We assessed the PPCP removal mechanism and efficiency of the AAO-MBR system and a combined advanced ultraviolet (UV)/chlorine treatment system. Under the condition with a hydraulic retention time of 40 h, reflux ratio of the mixed liquid of 400%, and carbon source addition to the blackwater (chemical oxygen demand = 780 mg/L), the removal of ibuprofen, carbamazepine, and bezafibrate by the improved AAO-MBR process exceeded 90%. The PPCP removal mechanisms in the AAO-MBR system were mainly biodegradation, sludge adsorption, and effluent residue. More than 95% of ibuprofen and bezafibrate were biodegraded, and the remaining portions were adsorbed on sludge or remained in the effluent, whereas only approximately 50% of carbamazepine was biodegraded, and the rest was adsorbed on sludge or remained in the effluent. When the UV intensity was 8.0 W/m2, the pH was 6, and the free chlorine concentration was 18 mg/L in the NaClO system, the target PPCPs were completely removed after 23 min. The effective removal of PPCPs from blackwater is essential for alleviating potential environmental risks. Our research provides technical support for the discharge of conventional pollutants and the coordinated removal of PPCPs using a UV/chlorine treatment process.

Postharvest Ultraviolet Radiation in Fruit and Vegetables: Applications and Factors Modulating Its Efficacy on Bioactive Compounds and Microbial Growth.

Ultraviolet (UV) radiation has been considered a deleterious agent that living organisms must avoid. However, many of the acclimation changes elicited by UV induce a wide range of positive effects in plant physiology through the elicitation of secondary antioxidant metabolites and natural defenses. Therefore, this fact has changed the original UV conception as a germicide and potentially damaging agent, leading to the concept that it is worthy of application in harvested commodities to take advantage of its beneficial responses. Four decades have already passed since postharvest UV radiation applications began to be studied. During this time, UV treatments have been successfully evaluated for different purposes, including the selection of raw materials, the control of postharvest diseases and human pathogens, the elicitation of nutraceutical compounds, the modulation of ripening and senescence, and the induction of cross-stress tolerance. Besides the microbicide use of UV radiation, the effect that has received most attention is the elicitation of bioactive compounds as a defense mechanism. UV treatments have been shown to induce the accumulation of phytochemicals, including ascorbic acid, carotenoids, glucosinolates, and, more frequently, phenolic compounds. The nature and extent of this elicitation have been reported to depend on several factors, including the product type, maturity, cultivar, UV spectral region, dose, intensity, and radiation exposure pattern. Even though in recent years we have greatly increased our understanding of UV technology, some major issues still need to be addressed. These include defining the operational conditions to maximize UV radiation efficacy, reducing treatment times, and ensuring even radiation exposure, especially under realistic processing conditions. This will make UV treatments move beyond their status as an emerging technology and boost their adoption by industry.