Background: Benzene is one of the most widely used volatile organic compounds showing severely adverse effects on human health. Removing benzene from the airflow or controlling its amounts, is one of the issues put to discussion in the field of environmental engineering. The objective of this study was to examine the efficacy of the Ultraviolet-C (UV-C) radiations on removing benzene from the airflow under conditions of varying humidity and reaction time in the UV/O3 process.Methods: This was an experimental study which was performed on a laboratory scale. The testing and measurement system included an air pump, an injection pump, a mixing chamber, a rotameter, an ozone generator, a heater, an impinger, and a steel reactor with 45 cm long, and with a net volume of 1.35 L in which a 15-watt UV-C lamp with a wavelength of 254 nm was placed. Different concentrations of benzene were continuously exposed to the UV/O3 process under varying conditions of reaction time and humidity. The concentrations of benzene before and after exposure to the treatment process were measured taking aforementioned factors into account. The data were analyzed using descriptive and inferential statistics and three-way ANOVA test.Findings: The results demonstrated that increasing the humidity levels up to 60% led to an increase in the efficacy of UV-C in the removal of benzene, while this efficacy decreased at humidity levels above 60%. Additionally, the findings indicated that increasing the reaction time can lead to the highest benzene removal rates in the presence of humidity (13.2%, P<0.001).Conclusion: Given the improvement in the efficacy of benzene removal as a result of the simultaneous use of UV and humidity, and the effects of increased reaction times in a process involving the simultaneous use of the UV rays and relative humidity, it can be concluded that the use of UV-C rays in an airflow containing humidity levels of 50% to 60% can have a positive potentiating effect on the efficacy.

This research was conducted to study the effect of UV-B rays and gamma rays on the disinfection of plants harvested from the field and also to study the antimicrobial activity of Satureja mutica essential oil in the form of 3 separate experiments. In the first experiment, harvested plants were treated with UV-B for 0, 2.5, 5, 7.5, and 10 hours. In the second experiment, samples were exposed to gamma radiation at 0, 2.5, 5, 7.5, and 10 kGy. In the third experiment, the antimicrobial effect of the essential oil of fresh S. mutica on Escherichia coli, Pseudomonas fluorescens and Staphylococcus aureus was investigated. The effect of UV-B radiation on Enterobacteriaceae, Staphylococcus aureus, and total molds and yeasts showed that the highest inhibition of microbial activity was achieved with UV-B rays for 10 hours. The antimicrobial effect of gamma rays on Enterobacteriaceae, Staphylococcus aureus, Salmonella and all molds and yeasts was significant at the 1% level. The microbial activity of Enterobacteriaceae, Staphylococcus aureus, Salmonella, and total molds and yeasts was determined to be 2.24%, 1.83%, 0.79%, and 10.8%, respectively, at 10 kGy gamma irradiation as the optimal condition. The effect of essential oil concentration on the percentage of microbial contamination showed that the highest inhibition of growth of the studied bacteria was observed in the pure essential oil treatment, so that the activity of Escherichia coli was reduced by 41.3%, Pseudomonas fluorescens by 16.7% and Staphylococcus aureus by 42.3%. The results showed that the use of UV-B radiation was not effective for disinfecting plants. The use of gamma radiation of 7.5 kGy and more was very successful in controlling microbial agents, and the use of Satureja mutica essential oil in controlling microbial agents had promising results.

It emerged recently that there is an inter-relationship between drought and Ultraviolet-B (UV-B) radiation in plant responses, in that both stresses provoke an oxidative burst. The objective of the present investigation was to study the effect of drought stress, UV-B radiation and the combined effects of UV-B and drought stresses on two cultivars of gourd seedling. The gourd plants were grown with diurnal regime of 16h light and 8h dark and temperature of 22/26oC (night/day). The relative humidity 60% and average of photosynthetically active radiation was 150 mmol.m-2.s-1. Treatments was started 25 days after planting. Then, 25-days-old seedlings were divided in to four groups. The control and three groups subjected to stress conditions: UV-B radiation, drought stress conditions, UV-B radiation and drought stresses combined. The results of measurement on compounds which absorbs UV including flavonoids, anthocyanins, phenol and antioxidant enzymes activity including catalase, guaiacol peroxidase showed that these parameters increased when plant irradiated with UV-B, drought stress and their combination. Biochemical parameters indicate that with this experiment situation UV-B stress has stronger stress effectors than drought on the growth of seedling of both cultivars. The present results suggested that, under soil drought conditions, enhanced UV-B radiation had not let to greater decrease gourd biochemical markers. The results suggested that co-stresses of supplementary UV-B radiation and drought synergistically functioned and one of them could alleviate the inhibitory effects of another under the condition of arid and semiarid loessial soils.

Dunaliella salina microalgae is a unique eukaryotic microorganism that has a high range of tolerance against environmental fluctuations including salinity, temperature, and light. The aim of this study was to determine the growth factors and content of fatty acids in D. salina under salinity and ultraviolet conditions. The experiments were conducted at three different salinities (150, 200 and 250 ppt) under UVB and UVC irradiations in 3 replicates. Algae growth rate and total algae biomass were measured by counting the number of cells every alternate day for 11 days by hemacytometer. The fatty acids profile was measured by gas chromatography and the amount of total fat using a soxhlet device. The growth rate of algae in most of the treatments under high salinity stress, UVB and UVC irradiation was significantly lower compared to the control group (P≤0.05). The highest cell counts were detected in the control one (2.4 million cells/ml) and UVB-150 treatment (1.98 million cells/ml) on day 7. But despite the higher cell count in the control group, the highest fresh wet weight of algae was obtained in the UVC-200 ppt/salinity group. Substantial differences were detected in the fatty acids profile between the treatments (P≤0.05). Algae cultured under UVB-200 contained the highest PUFA-n3 (20.05%) and the sum of PUFA (32.05%), while the highest PUFA-n6 (13.96%) was found in the UVC-150 group. Algae cultured at 250 ppt salinity without UV irradiation had the highest level (52.75%) of saturated fatty acids (SFA). It was concluded that UV irradiations and high salinity suppresses the growth but improves the synthesis of polyunsaturated fatty acids.

Introduction UV-C (254-280 nm) and 280-320 nm) UV-B, UV-A (320-390nm) wavelengths are irradiated with three ultraviolet strips and have detrimental effects on the growth of a number of plants. Ultraviolet light is an important non-living factor that can stimulate the production of secondary metabolites, including antioxidant compounds in plants. Ozone depletion and its consequences, including direct UV radiation on the planet and its effects on crops and medicinal plants, are among the topics that have received very little study. Ultraviolet light in nature occurs only at low intensities, but if the inhibitory effect of the ozone layer in the stratosphere is significantly the result of nitrogen and hydrocarbon oxides the weaker the halogen, the higher its amount. Materials and Methods Portulaca oleracea seeds were prepared by Pakan Isfahan Company. The aim of this study was the effect of ultraviolet rays at different levels (UV-C: 0, 100, 200, 300, 400, 500, 600, and 700 nm) on the activity of photosynthetic pigments and biochemical traits of portulaca oleracea in factorial in a completely randomized design with three replications. After transferring the seeds of portulaca oleracea, the healthy and uniform seeds of this plant were sterilized in 15% sodium hypochlorite solution for 154 minutes and then washed thoroughly with distilled water and placed in a petri dish for germination. Moisture was supplied through filter paper soaked in distilled water. The seeds were planted in pots filled with cocopeat and perlite evenly and watered for 20 days with a half-strength Hoagland solution. Plants were grown for 20 days at a temperature of 30 ± 2 ° C and a light period of 8. 16 (light / dark, respectively). Plants for one week, every other day, and for 3 minutes each time by two fluorescent lamps with a wavelength of 260 nm exposed to ultraviolet C (at a distance of 30 cm from the UV light source with an intensity of 27 (w / m2) were located. The traits studied in this study included chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, phenol, flavonoids, and antioxidant activity. In this study, the effect of ultraviolet light on the activity of photosynthetic pigments and biochemical traits of portulaca oleracea was investigated factorially in a completely randomized design with three replications. Results and Discussion The results of the mean comparison showed that the UV treatment of chlorophyll a, b, total chlorophyll, carotenoid of portulaca oleracea was reduced compared to the control,However, UV treatment of portulaca oleracea significantly increased phenol, flavonoids, and antioxidants compared to the control. The effect of different doses of ultraviolet rays on phenol and portulaca oleracea antioxidants showed that the UV-C highest and lowest were 700 and 100 nm, respectively. Decreases in carotenoid content can result in either inhibition of pigment synthesis or their breakdown and degradation. The results of this report indicate significant changes in phenols and flavonoids as compounds it absorbed ultraviolet rays compared to control cells. Conclusion It can be said that excessive exposure to radiation may affect chlorophyll levels by inhibiting chlorophyll biosynthesis or accelerating its degradation. Oxygen is an electron receptor in the electron transport system that produces energy from adenosine triphosphate (ATP) in the body. Under certain conditions, oxygen can be converted to a single electron, creating free radicals. When oxygen is converted to a single electron, it is called active oxygen (ROS). These free radicals cause oxidative stress in plants which oxidative stress leads to damage to macromolecules such as DNA, proteins and so on. Environmental stresses, including UV radiation, produce active oxygen species (ROS) such as hydrogen peroxide (H2O2), superoxide (O2-), and hydroxyl radicals (OH), which cause oxidative stress and cause damage to cells, such as DNA. And cause the destruction of these compounds. The plant contains compounds that act as active antioxidants and sweep away active oxygen. In the present study, the observed increase in phenols, flavonoids and antioxidants indicates an increase in the production of free radicals under ultraviolet radiation and shows that the production of these radicals is more than the plant's defense capacity and has caused damage to plant biological membranes. In summary, the application of controlled ultraviolet light stress can provide a new alternative strategy to increase the productivity of the portulaca oleracea plant. Modulating UV-C light in agricultural systems is a promising tool to increase crop production.