Effect of UV radiation and temperature on mineralization and volatilization of coumaphos in water

This study was undertaken to determine the dissipation and degradation of coumaphos [O-(3-chloro-4-methyl-2-oxo-2H-1-benzopyran-7-yl) O,O-diethyl phosphorothioate] under different sunlight conditions and at different temperatures. The effect of the ultra violet (UV) component of solar radiation was also studied using quartz tubes in addition to other radiation in the visible range using glass tubes and the results were compared with those obtained under the dark light conditions. Water suspensions of coumaphos were incubated at three temperatures viz. 22 degrees C, 37 degrees C and 53 degrees C in closed systems to study the effect of temperature. Volatilization, mineralization and degradation of coumaphos increased with an increase in temperature and exposure to solar radiation, particularly under the UV component of the solar radiation. Major loss of the pesticide occurred through volatilization. The optimum temperature for the degradation of coumaphos was found to be at 37 degrees C. The data obtained from the mineralization and degradation studies indicated that 53 degrees C crosses the biological range for suitable growth of microorganism. UV radiation exposure along with maintaining temperature at 37 degrees C may prove useful in the dissipation and/or degradation of coumaphos prior to its disposal as waste from cattle dipping vats.     

Persistence,degradation and leaching of coumaphos in soil

Abstract

Dissipation, degradation and leaching of fresh ¹⁴C coumaphos, alkylated ¹⁴C coumaphos and aged residues of ¹⁴C coumaphos from vats were studied in alkaline sandy loam soil in soil columns in the field under subtropical conditions in Delhi for a year. Dissipation, degradation and bound residue formation was more in case of alkali treated coumaphos than fresh coumaphos. After 365 days total residues of fresh coumaphos accounted for 33.25% while that of alkali treated coumaphos was 19.12%. Bound residue formation was almost double in case of alkali treated coumaphos (18.95%) than fresh coumaphos (9.53%) after 150 days followed by release of bound residue in both the cases. The proportion of metabolites 4 ‐ methylumbelliferone, chlorferon and potasan collectively was 86.05% in fresh coumaphos extractable residues while the same was 91.74% in alkali treated coumaphos after 365 days. Aged residues from vats containing copper sulphate and buffer were found to be more persistent in soil as total residues remained were 95.58% in comparison with 83.09% total residues of aged residues from vats containing only buffer after 150 days of treatment. Copper sulphate seems to inhibit the degradatiion of coumaphos in soil by microorganisms. Chlorferon was the major metabolite in generally all the samples. Coumaphos did not leach below 10 cm in all the cases.     

Gaseous mercury emissions from unsterilized and sterilized soils: The effect of temperature and UV radiation

Mercury (Hg) emissions from the soils taken from two different sites (deciduous and coniferous forests) in the Adirondacks were measured in outdoor and laboratory experiments. Some of the soil samples were irradiated to eliminate biological activity. The result from the outdoor measurements with different soils suggests the Hg emission from the soils is partly limited by fallen leaves covering the soils which helps maintain relatively high soil moisture and limits the amount of heat and solar radiation reaching the soil surface. In laboratory experiments exposure to UV-A (365 nm) had no significant effect on the Hg emissions while the Hg emissions increased dramatically during exposure to UV-B (302 nm) light suggesting UV-B directly reduced soil-associated Hg. Overall these results indicate that for these soils biotic processes have a relatively constant and smaller influence on the Hg emission from the soil than the more variable abiotic processes.     

SMX degradation by ozonation and UV radiation: a kinetic study

The rate constants of sulfamethoxazole (SMX) degradation by ozonation and UV₂₅₄ radiation were investigated under various parameters including influent ozone gas concentration, initial SMX concentration, UV light intensity, ionic strength, water quality in terms of varying anions (bicarbonate, sulfate and nitrate), humic acid (HA) and pH. The results indicated that the removal of SMX by ozonation and UV₂₅₄ radiation fitted well to a pseudo first-order kinetic model and the rate constants were in the range of (0.9-9.8) × 10⁻³ and (1.7-18.9) × 10⁻³ s⁻¹, respectively. The second-order rate constants of SMX with ozone (k_O3), under varying operational parameters, were also determined and varied in the range of (0.60-3.38) ± 0.13 × 10⁵ M⁻¹ s⁻¹. In addition, SMX degradation through UV pretreatment followed by ozonation in the presence of HA was proved to be an effective method which can remove SMX with a low ozone dose. The results suggested that ozonation of SMX was more affected by concentration of influent ozone gas, alkalinity, and HA, while incident UV light intensity, pH, and HA were the dominant factors influencing UV degradation of SMX.     

Cell size dependence of additive versus synergetic effects of UV radiation and PAHs on oceanic phytoplankton

Polycyclic Aromatic Hydrocarbons’ (PAHs) toxicity is enhanced by the presence of ultraviolet radiation (UVR), which levels have arisen due to the thinning of the ozone layer. In this study, PAHs’ phototoxicity for natural marine phytoplankton was tested. Different concentrations of a mixture of 16 PAHs were added to natural phytoplankton communities from the Mediterranean Sea, Atlantic, Arctic and Southern Oceans and exposed to natural sunlight received in situ, including treatments where the UVR bands were removed. PAHs’ toxicity was observed for all the phytoplankton groups studied in all the waters and treatments tested, but only for the pico-sized group a synergetic effect of the mixture and UVR was observed (p = 0.009). When comparing phototoxicity in phytoplankton from oligotrophic and eutrophic waters, synergy was only observed at the oligotrophic communities (p = 0.02) where pico-sized phytoplankton dominated. The degree of sensitivity was related to the trophic degree, decreasing as Chlorophyll a concentration increased.     

紫外消毒器辐射剂量模拟与设备设计

基于拉格朗日方法建立了耦合流体流动、紫外光强辐射与粒子辐射剂量的数值计算模型.利用该模型对工业尺寸的紫外消毒设备进行了模拟计算,获得了消毒设备内的场量信息;展示了利用CFD模拟优化设计紫外消毒反应器的方法;讨论了设置挡板和改变灯管布置2种方式对粒子辐射剂量的影响,计算结果表明,调整辐射场对紫外消毒设备性能的改善程度明显高于改变流动状态.     

Hydroxycinnamic acid derivatives in an aquatic liverwort as possible bioindicators of enhanced UV radiation

We examined, under laboratory conditions, the physiological responses of the aquatic liverwort Jungermannia exsertifolia subsp. cordifolia to artificially enhanced ultraviolet (UV) radiation for 82 days, especially considering the responses of five hydroxycinnamic acid derivatives. This species lives in mountain streams, where it is exposed to low temperatures and high UV levels, and this combination is believed to increase the adverse effects of UV. Enhanced UV radiation hardly caused any change in several physiological variables indicative of vitality, such as Fv/Fm and chlorophylls/phaeopigments ratio (OD430/OD410). Thus, this liverwort seemed to be tolerant to UV radiation, probably due to the accumulation of three UV-absorbing hydroxycinnamic acid derivatives: p-coumaroylmalic acid, 5'-(7',8'-dihydroxycoumaroyl)-2-caffeoylmalic acid, and 5'-(7',8'-dihydroxy-7-O-beta-glucosyl-coumaroyl)-2-caffeoylmalic acid. These compounds might serve as bioindicators of enhanced UV radiation.     

Photocatalytic mineralization of glyphosate in a small-scale plug flow simulation reactor by UV/TiO2

The present work involves the photocatalytic mineralization of glyphosate on a plug flow reactor by UV/TiO₂. The effect of catalyst loading shows an optimal value (0.4 g L^?1) which is necessary to mineralize glyphosate. The kinetic rate of glyphosate mineralization decreases with the increasing initial concentration of glyphosate, and the data can be described using the first-order model. An alkaline environment is conducive to glyphosate mineralization. The mineralization efficiency increases with elevated flow rate to 114 mL min^?1, which is followed by a decrease with a further increase in flow rate due to the reduction of the residence time. The presence of external oxidants (K₂S₂O₈, H₂O₂ and KBrO₃) and photosencitizer (humic acid) can significantly enhance glyphosate mineralization. Photocatalysis oxidation ability of the three studied oxidants decrease in the order of: S₂O₈ ^2? > BrO₃ ^? > H₂O₂. Finally, the Langmuir–Hinshelwood (L-H) model was used to rationalize the mechanisms of reactions occurring on TiO₂ surfaces and L-H model constants were also determined.     

水质对紫外消毒在两种典型再生水中应用的影响

以大肠杆菌为对象,研究了再生水水质变化对紫外消毒效果和光复活的影响。结果表明,紫外对大肠杆菌有很强的灭活作用,在紫外剂量为4mJ／cm^2时,大肠杆菌的灭活率达到了4．41个对数级。腐殖酸、铁和2种再生水水体中其他溶解性物质会影响光吸收和紫外透射率,但对紫外消毒动力学无影响。在颗粒物浓度为0～200mg／L的范围内,外源高岭土和活性污泥等颗粒物的投加对紫外消毒效果影响较小,而再生水水样W1中原有的2．61／1：g／L的颗粒物则会极大地影响消毒效果,使UV对细菌的灭活出现明显的拖尾现象。腐殖酸会增强紫外损伤大肠杆菌的光复活能力,但2种再生水中细菌的光复活能力相对磷酸盐缓冲溶液（PBS）中减弱,减弱程度在不同水样中有所不同。     

Effect of humic acids on photodegradation of chloroacetanilide herbicides under UV irradiation

The effects of two humic acids (HAs) of different origins on the photodegradation of the chloroacetanilide herbicides acetochlor, propisochlor and butachlor were investigated in this study. One of the tested HAs was a standard sample that was purchased from a commercial source, and the other was isolated from the black soil of Northeast China. The photolysis of all three herbicides followed pseudo-first-order kinetics under ultraviolet (UV) irradiation conditions, regardless of whether HAs were present or not. Both HAs improved the photolysis rates of acetochlor in a dose-reversed way, whereas they inhibited butachlor degradation under all experimental concentrations. The two HAs differed in their effects on propisochlor photolysis, changing from enhancement to inhibition, depending on the origin and concentration of HAs. Element and Fourier Transform Infrared spectroscopy analyses showed that the isolated HAs had more polysaccharides and less aliphatic groups than the commercial HAs, and it was indicated that some characteristic radicals (C═O, O─H and phenolic hydroxyls) in HAs were involved in the photolysis of the herbicides. Gas chromatography/mass spectrometry (GC/MS) analyses indicated that the presence of HAs had no effects on the photolysis pathway and photoproduct species of the three herbicides.     

紫外光去除水中微量甲苯的研究

紫外光（UV）去除水中微量甲苯（＜10mg/L)可以用一级动力学方程描述。pH为7时，去除速率常数k为0.453h^-1，半衰期为1.53h；在pH为5－9的范围内，速率常数和半衰期变化不大。利用气相色谱－质谱联用仪测定了甲苯的降解产物，讨论了甲苯降解的机理。测定了甲苯降解过程中溶解氧化的变化和pH的作用。     

Influence of solar UV radiation on the nitrogen metabolism in needles of Scots pine (Pinus sylvestris L.)

Needles of 20-year-old Scots pine (Pinus sylvestris L.) saplings were studied in an ultraviolet (UV) exclusion field experiment (from 2000 to 2002) in northern Finland (67 °N). The chambers held filters that excluded both UV-B and UV-A, excluded UV-B only, transmitted all UV (control), or lacked filters (ambient). UV-B/UV-A exclusion decreased nitrate reductase (NR) activity of 1-year-old needles of Scots pines compared to the controls. The proportion of free amino acids varied in the range 1.08-1.94% of total proteins, and was significantly higher in needles of saplings grown under UV-B/UV-A exclusion compared to the controls or UV-B exclusion. NR activity correlated with air temperature, indicating a “chamber effect”. The study showed that both UV irradiance and increasing temperature are significant modulators of nitrogen (N) metabolism in Scots pine needles.     

Ferrioxalate-mediated photodegradation and mineralization of 4-Chlorophenol

INTENTION, GOAL, SCOPE, BACKGROUND: Advanced oxidation processes are powerful methods which are capable of transforming refractory, nonbiodegradable and/or toxic organic compounds into harmless end products such as carbon dioxide and water. However, one commen problem of all advanced oxidation processes is the high demand of electrical energy for ultraviolet lamps, which causes high operational costs. Minimization of the required irradiation time, and therefore the energy consumption, by optimization of other reaction conditions such as catalyst-oxidant type and concentration, pH, temperature, pollutant/oxidant ratio etc., therefore continues to gain importance. OBJECTIVE: The main objective of this study was the minimization of the required irradiation time through optimization of the use of a newly patented catalyst, ferrioxalate, and also to compare the performance of this catalyst with the performance of other AOPs. METHODS: Oxidation of 4-chlorophenol by photo-Fenton process using potassium ferrioxalate as a mediator was studied in a lab scale photoreactor. The influence of parameters such as hydrogen peroxide and ferrioxalate concentrations, initial pH, power-output, oxalate/iron ratio and different iron sources was evaluated. An upflow photoreactor equipped with a 1000 Watt high-pressure mercury vapour lamp and operating in a recirculation mode was used during photodegradation experiments. The extent of the reduction of 4-chlorophenol, Total Organic Carbon and Chemical Oxygen Demand was used to evaluate the photodegradation reaction. RESULTS AND DISCUSSION: The optimum pH range observed was found to be 2.7-3. The efficiency of 4-chlorophenol oxidation increased with increasing concentrations of hydrogen peroxide and ferrioxalate, reaching a plateau after the addition of 10 and 0.072 mM of those reagents, respectively. Using an Oxalate/iron ratio of 12 was 18% less efficient than using a ratio of 3:1. The efficiency increased with increasing radiation power. However, this increase was not linear. The UV/ferrioxalate/H2O2 process, by which complete mineralization of 100 mg l(-1) 4-chlorophenol was achieved in 20 min of total reaction time, was the most efficient process among the alternatives applied. CONCLUSIONS: The use of ferrioxalate as the catalyst was found to be more efficient than the use of Fe(II) and Fe(III) iron species. It was possible to completely mineralize 4-chlorophenol. RECOMMENDATION AND OUTLOOK: The results of this study demonstrate that the ferrioxalate-mediated degradation of 4-chlorophenol requires less irradiation times than other advanced oxidation processes. There are mainly 19 phenol isomers and other toxic and nonbiodegradable organic compounds. We recommend that similar studies should be performed on many such compounds in order to attain a clear understanding of the performance of this catalyst. Because of its light sensitivity, this catalyst should be used immediately after its preparation. The use of low pressure mercury vapour lamps in this process should also be considered, since low power outputs may be enough for the process.     

紫外波长对UV/Cl2高级氧化去除水中有机物的影响

为明确紫外波长对UV/Cl2高级氧化体系的影响,使用中心波长分别为267、275和286 nm的发光二极管LED作为光源,探究Cl2光解动力学、UV/Cl2体系自由基生成、对模式化合物溶液以及天然水、再生水TOC的去除。结果表明：在中性或酸性体系中,267 nm最接近HClO最大吸收波长237 nm,吸光度和量子产率均较大,羟基自由基产生水平较高,有机物去除效果较好;在碱性体系中,286 nm最接近ClO-最大吸收波长292 nm,尽管量子产率较小,但吸光度很大,有机物去除效果较好;由于水杨酸在292 nm附近有较强的竞争吸收,使用UV286去除水杨酸效果被削弱。应用UV/Cl2技术选择波长时需要考虑吸光度、量子产率、竞争吸收等因素;对于弱碱性天然水或再生水,采用波长为292 nm的紫外光一般可获得较优处理效果。     

富油煤热解焦油在粉砂中的自然降解与挥发行为

富油煤原位热解的油、气等产物可通过开采形成的压裂缝进入地下环境,产生一系列环境行为。为进一步了解富油煤热解产物在地下环境中的自然降解与挥发行为,选择粉砂作为典型土壤,以富油煤热解焦油为典型污染物,开展了煤焦油5种组分在粉砂中的自然降解和挥发行为研究,建立了2种环境行为的动力学模型;进一步考察了温度、污染物初始质量浓度等因素对自然降解与挥发的影响。结果表明,煤焦油各组分在粉砂中的降解效果顺序为,酚油>洗油>萘油>沥青>蒽油,且粉砂中各组分的自然降解符合一级动力学方程。其中,酚油的降解速率常数最大,为6.18×10⁻³;而蒽油的半衰期最长,达到了228 d;温度35 ℃时的降解率为67%,初始质量浓度为10 g·kg⁻¹时,降解率高达72%。粉砂中煤焦油的挥发符合Elovich方程,各组分在粉砂中的挥发效果顺序为,酚油>萘油>洗油>蒽油>沥青。其中,酚油的挥发率是沥青挥发率的4倍;酚油在35 ℃时的挥发率是15 ℃的1.2~2.5倍,污染物初始质量浓度对煤焦油各组分的挥发影响较小。本研究结果可为开展原位开采引起的地下水环境污染控制与修复提供参考。     

紫外活化过硫酸盐工艺降解水中磺胺二甲氧嘧啶动力学特征与机理

采用紫外活化过硫酸盐(UV/PS)工艺降解典型磺胺类抗生素磺胺二甲氧嘧啶(SDM),比较单一紫外(UV)、单一过硫酸盐(PS)和UV/PS对SDM的去除效果,考察各因素对降解动力学的影响,并探究其降解机理,对SDM及其中间产物进行毒性测定和风险评价.结果显示,UV/PS可以加速SDM降解,反应速率常数分别是单一UV和单...     

光反应器中UV/Fenton光降解湖水中微囊藻毒素的研究

在光催化反应器中,采用UV/Fenton光催化氧化技术,对湖水中微囊藻毒素的光催化降解过程中各影响因子分析表明:微囊藻毒素光催化氧化降解率受光照强度、氧化剂种类及浓度、溶液pH和不同光催化体系等多因素的影响.光促催化氧化体系对MC-LR藻毒素降解具有显著的作用,在紫外光与氧化剂的协同作用下,紫外光照强度越高,越易于促进MC-LR藻毒素快速降解,降解率可到达80%以上.     

Decomposition and mineralization of cefaclor by ionizing radiation: kinetics and effects of the radical scavengers

There has been recent growing interest in the presence of antibiotics in different environmental sectors. One considerable concern is the potential development of antibiotic-resistant bacteria in the environment, even at low concentrations. Cefaclor, one of the beta-lactam antibiotics, is widely used as an antibiotic. Kinetic studies were conducted to evaluate the decomposition and mineralization of cefaclor using gamma radiation. Cefaclor, 30 mg/l, was completely degraded with 1,000 Gy of gamma radiation. At a concentration of 30 mg/l, the removal efficiency, represented by the G-value, decreased with increasing accumulated radiation dose. Batch kinetic experiments with initial aqueous concentrations of 8.9, 13.3, 20.0 and 30.0mg/l showed the decomposition of cefaclor using gamma radiation followed a pseudo first-order reaction, and the dose constant increased with lower initial concentrations. At a given radiation dose, the G-values increased with higher initial cefaclor concentrations. The experimental results using methanol and thiourea as radical scavengers indicated that ()OH radicals were more closely associated with the radiolytic decomposition of cefaclor than other radicals, such as e(aq)(-) or ()H. The radical scavenger effects were tested under O(2) and N(2)O saturations for the enhancement of the TOC percentage removal efficiencies in the radiolytic decomposition of cefaclor. Under O(2) saturation, 90% TOC removal was observed with 100,000 Gy. Oxygen is well known to play a considerable role in the degradation of organic substances with effective chain reaction pathways. According to the effective radical reactions, the enhanced TOC percentage removal efficiencies might be based on the fast conversion reactions of e(aq)(-) and ()H with O(2) into oxidizing radicals, such as O(2)(-) and HO(2)(), respectively. 100% TOC removal was obtained with N(2)O gas at 20,000 Gy, as reducing radicals, such as e(aq)(-) and ()H, are scavenged by N(2)O and converted into ()OH radicals, which have strong oxidative properties. The results of this study showed that gamma irradiation was very effective for the removal of cefaclor in aqueous solution. The use of O(2) or N(2)O, with radiation, shows promise as effective radical scavengers for enhancing the TOC or COD removal efficiencies in pharmaceutical wastewaters containing antibiotics. However, the biological toxicity and interactions between various chemicals during the radiolytic treatment, as well as treatments under conditions more representative of real wastewater will require further studies.     

炼化企业中水紫外线消毒及其影响因素简

研究水质对254 nm紫外线透射率的影响,通过动态实验考察了照射时间、254 nm紫外线透射率以及紫外线剂量对炼化企业中水消毒效果的影响并同时考察异养菌、硫酸盐还原菌和铁细菌的光复活及暗修复现象。结果表明,有机物是影响炼化企业中水紫外线消毒的重要因素;紫外线对炼化企业中水中的异养菌具有良好的灭活作用;增加照射时间对消毒效果的提升作用受254 nm紫外线透射率的影响;紫外线透射率在较低的范围内时对消毒效果的影响相对较大,在较高的范围内时影响较小;紫外线剂量-响应曲线受254 nm紫外线透射率的影响;剂量的“成分”,即照射时间和透射率的不同组合,也会对消毒效果产生影响;在80 mJ/cm²的剂量下,20 h内异养菌出现了较强烈的光复活和暗修复现象,铁细菌仅出现了明显的光复活现象,硫酸盐还原菌没有表现出明显的复活。     

六氯苯的O3及UV/O3高级氧化降解试验研究

采用O3、UV/O3高级氧化法对水中六氯苯（HCB）的降解效果及机理进行了研究,并对结果进行了比较,结果表明,UV本身对HCB的去除率贡献不大,HCB可被O3、UV/O3快速降解,即UV＜O3＜UV/O3;O3、UV/O3作用时,提高体系的初始pH值不利于HCB的降解,在pH＝3,HCB=0.2 mg/L,反应40 min时,HCB的去除可达50%左右,酸性条件下有利于降解反应的进行;无论是O3单独作用还是UV/O3联合作用,HCB的降解基本上满足准一级反应动力学规律,如果体系的pH值基本保持恒定,这种规律就更为明显。根据离子色谱(IC)、GC对六氯苯降解中间产物进行了测定,探讨了O3、UV/O3降解六氯苯的途径和机理。