Photochemical degradation of atrazine in UV and UV/H2O2 process: pathways and toxic effects of products

The degradation of atrazine in aqueous solution by UV or UV/H₂O₂ processes, and the toxic effects of the degradation products were explored. The mineralization of atrazine was not observed in the UV irradiation process, resulting in the production of hydroxyatrazine (OIET) as the final product. In the UV/H₂O₂ process, the final product was ammeline (OAAT), which was obtained by two different pathways of reaction: dechlorination followed by hydroxylation, and the de-alkylation of atrazine. The by-products of the reaction of dechlorination followed by hydroxylation were OIET and hydroxydeethyl atrazine (OIAT), and those of de-alkylation were deisopropyl atrazine (CEAT), deethyl atrazine (CIAT), and deethyldeisopropyl atrazine (CAAT). OIAT and OAAT appeared to be quite stable in the degradation of atrazine by the UV/H₂O₂ process. In a toxicity test using Daphnia magna, the acute toxic unit (TUa) was less than 1 of TUa (100/EC₅₀, %) in the UV/H₂O₂ process after 30 min of reaction time, while 1.2 to 1.3 of TUa was observed in the UV process. The TUa values of atrazine and the degradation products have the following decreasing order: OIET> Atrazine> CEAT≈CIAT> CAAT. OIAT and OAAT did not show any toxic effects.     

Reduction of toxicity of antimicrobial compounds by degradation processes using activated sludge,gamma radiation,and UV

The occurrence and persistence of pharmacologically active compounds in the environment has been an increasingly important issue. The objectives of this study were to investigate the decomposition of aqueous antimicrobial compounds using activated sludge, γ-irradiation, and UV treatment, and to evaluate the toxicity towards green algae, Pseudokirchneriella subcapitata, before and after treatment. Tetracycline (TCN), lincomycin (LMC) and sulfamethazine (SMZ) were used as target compounds. Gamma (γ)-irradiation showed the highest removal efficiency for all target compounds, while UV and activated sludge treatment showed compound-dependent removal efficiencies. TCN and SMZ were well degraded by all three treatment methods. However, LMC showed extremely low removal efficiency for UV and activated sludge treatments. Overall, the algal toxicity after degradation processes was significantly decreased, and was closely correlated to removal efficiency. However, in the case of γ-irradiated TCN, UV and activated sludge treated LMC as well as sludge treated SMZ, the observed toxicity was higher than expected, which indicates the substantial generation of byproducts or transformed compounds of a greater toxicity in the treated sample. Consequently, γ-radiation treatment could be an effective method for removal of recalcitrant compounds such as antibiotics.     

UV/H2O2降解水中磺胺嘧啶影响因素及机理

利用UV/H2O2光氧化反应器降解水中的磺胺嘧啶,考察了H2O2投量、pH值、紫外功率等因素对去除效果的影响,同时对反应动力学及降解产物进行了分析。结果表明,在紫外辐照与H2O2氧化共同作用下,UV/H2O2降解水中磺胺嘧啶效果显著,去除率达90%以上,其降解过程符合一级反应动力学模型（R2=0.991 2）。H2O2投量与磺胺嘧啶降解速率常数具有良好的线性关系,H2O2投量由0.03增大至1.50 mmol·L-1,反应速率常数由0.048 2增大至0.359 9 min-1;同时,随着紫外灯功率由5增大至15 W,反应速率常数由0.066 2增大至0.163 1 min-1;随着初始磺胺嘧啶浓度由0.02增加至0.08 mmol·L-1,反应速率常数由0.251 7逐渐降低至0.046 8 min-1;pH由3.0升高至7.0,反应速率常数由0.070 2增大至0.102 3 min-1,当pH继续增大时,反应速率常数反而降低。根据液相色谱/质谱（LC/MS）对中间产物分析,UV/H2O2降解磺胺嘧啶生成质荷比（m/z）为173、186和200的对氨基苯磺酸等中间产物,推测S-N键和C-N键被打开,这些中间产物可进一步被降解,但TOC去除率仅为7%,表明磺胺嘧啶仅部分被矿化。UV/H2O2工艺处理磺胺嘧啶的电能效率（EEO）采用每一对数减少级电能输入进行评价,优化条件下电能效率为0.078 kWh·m-3,可为实际工程应用提供参考。     

Sun light degradation of 4-chloroaniline in waters and its effect on toxicity. A high performance liquid chromatography - Diode array - Tandem mass spectrometry study

This paper studies the degradation reactions that 4-chloroaniline can naturally undergo in waters for the action of sun light. 10.00 mg L⁻¹ 4-chloroaniline aqueous solution, without any addition of organic solvent, are undergone to photoirradiation under conditions that simulate sun light. The degradation pathway, followed by HPLC-DAD-MS/MS methods, is complex since the pollutant gives rise to many photoproducts: the predominant species are characterized by m/z values of 217 (P5) and 218 (P6) and are compatible with dimeric structures of 4-chloroaniline. Vibrio fischeri tests indicate that the photoproducts of 4-chloroaniline are characterized by a toxicity level significantly greater than the precursor.     

UV/H2O2工艺降解典型消炎药布洛芬影响因素和降解机理

布洛芬是一种典型药物和个人护理用品（PPCPs）,大量生产和广泛使用给环境带来了一定危害。基于响应面方法,采用UV/H2O2工艺降解布洛芬（IB）,对降解过程中的影响因素（光强、H2O2投加量、初始IB浓度）进行了探讨,构建响应面模型。优化的最佳反应条件为：H2O2投加量0.10 mol·L-1、初始IB浓度5.00 mg·L-1、UV光强1 400 μW·cm-2,预测和实验IB以及反应动力学速率常数接近,说明响应面模型能够有效描述UV/H2O2降解反应过程。同时用离子阱质谱仪鉴定出IB羟基加成物、4-乙基苯酚、对异丁基苯甲酸等降解中间产物,其中IB羟基加成物的细胞毒性大于IB本身,最后提出降解机理。本研究为UV/H2O2工艺降解典型消炎药类污染物提供技术参考。     

Bioaccumulation and toxicity of a cationic surfactant (DODMAC) in sediment dwelling freshwater invertebrates

Dimethyldioctadecylammonium chloride (DODMAC, CAS No. 107-64-2) is the principal active component of Di(hydrogenated tallow alkyl) dimethylammonium chloride (DHTDMAC, CAS No. 61789-80-8), a cationic surfactant formerly used principally in laundry fabric softeners. After discharge to water, DODMAC partitions strongly to sediment, therefore the assessment of the effects of DODMAC to benthic organisms is essential in any risk assessment. Chronic toxicity studies were conducted with Lumbriculus variegatus (Oligochaete), Tubifex tubifex (Oligochaete) and Caenorhabditis elegans (Nematode). NOECs were greater than 5738, 1515 and 1351 mg/kg dw, respectively, even for sub-lethal effects. Measurement of the route of uptake of DODMAC by L. variegatus demonstrated the relative importance of uptake via ingestion (86%) compared with direct contact with the sediment and via pore water (14%). The overall tendency of DODMAC to bioaccumulate, however, was low with measured accumulation factors of 0.22 and 0.78 for L. variegatus and T. tubifex, respectively.     

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。     

Time-dependent degradation and toxicity of diclofop-methyl in algal suspensions

Background, aim, and scope  As emerging contaminants, transformation products of the pollutants via various environmental processes are rather unknown, and some may predominately contribute to the environmental risks of the parent compounds. Hence, studies on transformation products complement the assessment of the environmental safety of the parent compounds. In this study, degradation experiments and toxicity tests using diclofop-methyl (DM), a widely used herbicide, and selected major transformation products were carried out in algal cultures to assess the time course of DM toxicity and its relevance in the formation of new breakdown products. Methods  The alga Chlorella vulgaris was maintained in the algal growth medium HB IV. The inhibition of algal growth was determined by measuring optical density at 680 nm (OD₆₈₀). Initially, DM and two selected breakdown products were added to the algal cultures, and following degradation experiments analyses were carried out by high performance liquid chromatography. In addition, the possible relationship between DM degradation and toxicity was assessed, based on physico-chemical properties of the compounds and their toxicity. Results  DM was rapidly absorbed onto the surface of the algal cells where it was hydrolyzed to diclofop (DC). Further degradation to 4-(2, 4-dichlorophenoxy) phenol (DP) occurred in the cells. However, only a minor amount of DC was degraded to DP under the same conditions when DC was initially added to the algal culture. When C. vulgaris was exposed to these compounds for 96 h, the determined EC₅₀ showed that DC was about ten times less toxic than DM (EC₅₀ = 0.42 mg/L) and that DP (EC₅₀ = 0.20 mg/L) was the most toxic. Discussion  Due to strong hydrophobicity and rare dissociation, DM has tendency toward absorption as compared to DC. The higher average degradation rates of DC initially treated by DM revealed the damage of the cell membranes caused by the DM and, thus, enhanced movement of DC into the cells. Following occurrence of phenolic breakdown products, DP suggested that DC should be intracellularly degraded to DP, which had a more potent mode of action and a higher acute toxicity. Moreover, the results for EC₅₀ at various intervals were in accordance with degradation processes of the initial compounds, in which rapid formation of DP was attributed to an increasing toxicity of DM. Conclusions  The toxicity of DM in algal suspensions increased with time due to its degradation to DP, which contributed significantly to the determined toxicity. These results indicate that the toxicity of the pesticide probably depends significantly on degradation. It is thus important to consider the time-dependent environmental processes when evaluating the toxicological effects of pesticides for proper risk assessment. Recommendations and perspectives  Increasing transformation products of these contaminants are identified in the environment, although they seem to be unknown in terms of the lacking studies on environmental behavior and ecotoxicity concerning them. Certain breakdown products probably greatly contribute to the apparent toxicity of the parent compounds, which is ascribed to the parent compounds in general studies ignoring the dependence of their toxicity on various transformation pathways. These studies that identify new intermediates and assess their toxicity via the environmental processes will be helpful to distinguish the nature of toxicity of the parent contaminants.     

ZnIn2S4可见光催化降解水中的双氯芬酸

通过水热法制备了可见光下响应的光催化剂ZnIn2S4,研究了水中痕量医药类物质双氯芬酸的光解和光催化降解效果与降解途径,同时对催化剂进行了扫描电镜、X射线衍射、紫外可见漫反射、氮吸附和羟基自由基捕获的测试。结果表明,ZnIn2S4的比表面积为91.3 m2·g-1,且在可见光照射下具有良好光催化性能。以卤钨灯模拟太阳光,在双氯芬酸初始浓度100 μg·L-1,ZnIn2S4投加浓度10 mg·L-1条件下反应5 h可降解水中98%的双氯芬酸。卤钨灯直接光解5 h可降解91%的双氯芬酸。光解和光催化反应均符合假一级反应动力学,光催化反应速率是光解反应速率的1.5倍。双氯芬酸光解过程中主要发生光环化反应,生成了2-（1-氯-9H-咔吧唑-8-基）-乙酸;光催化过程则主要通过羟基自由基氧化降解双氯芬酸,中间产物主要有1-氯-8-甲基-9H-咔吧唑及2,6-二氯-N-邻甲苯基苯胺。     

Altered toxicity of organic pollutants in water originated from simultaneous exposure to UV photolysis and CdSe/ZnS quantum dots

The paper reports unforeseen results of increased toxicity of water, subsequent to interactions between CdSe/ZnS quantum dots (QDs), phenol and toluene under UV irradiation. The consistent pattern of changes in measured toxicity (TU) was observed and correlated with degradation of phenol and/or toluene. Spearman rank coefficients (SRCs) for data pairs sum-parameters vs. TU were calculated. The highest correlation between toxicity and degradation by-products was observed for hydroquinone (0.86) and catechol (0.89). The presence of QDs in tested concentration range in the absence of UV has shown low toxicity and no interactions with phenol and/or toluene. The leak of constituent core and shell metal ions was observed. The minor differences in physical characteristics of tested QDs of the same chemical composition led to rather different degradation patterns of phenol and toluene, and the amount of leak of the metal ions as well.     

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。     

Evaluation of photolysis and hydrolysis of pyraclostrobin in aqueous solutions and its degradation products in paddy water

This study evaluated the hydrolysis and photolysis kinetics of pyraclostrobin in an aqueous solution using ultra-high-performance liquid chromatography–photodiode array detection and identified the resulting metabolites of pyraclostrobin by hydrolysis and photolysis in paddy water using high-resolution mass spectrometry coupled with liquid chromatography. The effect of solution pH, metal ions and surfactants on the hydrolysis of pyraclostrobin was explored. The hydrolysis half-lives of pyraclostrobin were 23.1–115.5?days and were stable in buffer solution at pH 5.0. The degradation rate of pyraclostrobin in an aqueous solution under sunlight was slower than that under UV photolysis reaction. The half-lives of pyraclostrobin in a buffer solution at pH 5.0, 7.0, 9.0 and in paddy water were less than 12?h under the two light irradiation types. The metabolites of the two processes were identified and compared to further understand the mechanisms underlying hydrolysis and photolysis of pyraclostrobin in natural water. The extracted ions obtained from paddy water were automatically annotated by Compound Discoverer software with manual confirmation of their fragments. Two metabolites were detected and identified in the pyraclostrobin hydrolysis, whereas three metabolites were detected and identified in the photolysis in paddy water.     

Influence of pH on the sonolysis of ciprofloxacin: Biodegradability, ecotoxicity and antibiotic activity of its degradation products

The presence of antibiotics in the aquatic environment has raised concerns due to the potential risk for the emergence or persistence of antibiotic resistance. Antibiotics are often poorly degraded in conventional wastewater treatment plants. In this study, sonolysis at 520 kHz and 92 W L⁻¹ was used for the degradation of the fluoroquinolone antibiotic ciprofloxacin. In a first experiment at pH 7, 57% of the ciprofloxacin (15 mg L⁻¹) was degraded after 120 min of ultrasonic irradiation at 25 °C. pH proved to be an important parameter determining the degradation rate, since the pseudo first order degradation constant increased almost fourfold when comparing treatment at pH 7 (0.0058 min⁻¹) and pH 10 (0.0069 min⁻¹) with that at pH 3 (0.021 min⁻¹). This effect can be attributed to the degree of protonation of the ciprofloxacin molecule. The BOD/COD ratio of the solutions, which is a measure for their biodegradability, increased from 0.06 to 0.60, 0.17, and 0.18 after 120 min of irradiation depending on the pH (3, 7, and 10, respectively). The solution treated at pH 3 can even be considered readily biodegradable (BOD/COD > 0.4). The antibiotic activity against Escherichia coli (G−) and Bacillus coagulans (G+) of the treated solutions also reduced after sonolysis. The highest decrease was again found when irradiated at pH 3. In contrast, ecotoxicity of the solutions to the alga Pseudokirchneriella subcapitata increased 3- to 10-fold after 20 min of treatment, suggesting the formation of toxic degradation products. The toxicity slowly diminished during further treatment.     

Conductive-diamond electrochemical oxidation of chlorpyrifos in wastewater and identification of its main degradation products by LC-TOFMS

The electrochemical transformation of the organophosphorous insecticide chlorpyrifos (CPF) was investigated in wastewater. The oxidation of CPF was carried out in a single-compartment electrochemical flow cell working under batch operation mode, using diamond-based material as anode and stainless steel as cathode. In order to evaluate its persistence and degradation pathway, two different concentration levels (1.0 mg L⁻¹ and 0.1 mg L⁻¹) were studied. Liquid chromatography/mass spectrometry was used for evaluation of the initial and electrolyzed solutions. The identification of CPF transformation products was performed by liquid chromatography-time of flight-mass spectrometry (LC-TOFMS). Results showed that CPF is completely removed at the end of treatment time. Analysis by LC-TOFMS allowed the identification of six degradation products (with Mw 154, 170, 197, 305 321 and 333). Three of the identified intermediates (Mw 170, 305 and 321) were completely removed at the end of electrolysis time. Interestingly, the formation of diethyl 3,5,6-trichloropyridin-2yl phosphate (chlorpyrifos oxon) and 3,5,6-trichloropyridin-2-ol was also found in previous reported degradation pathways using different degradation technologies.     

Nitrate-induced photodegradation of atenolol in aqueous solution: kinetics, toxicity and degradation pathways

The extensive utilization of β-blockers worldwide led to frequent detection in natural water. In this study the photolysis behavior of atenolol (ATL) and toxicity of its photodegradation products were investigated in the presence of nitrate ions. The results showed that ATL photodegradation followed pseudo-first-order kinetics upon simulated solar irradiation. The photodegradation was found to be dependent on nitrate concentration and increasing the nitrate from 0.5 mM L⁻¹ to 10 mM L⁻¹ led to the enhancement of rate constant from 0.00101 min⁻¹ to 0.00716 min⁻¹. Hydroxyl radical was determined to play a key role in the photolysis process by using isopropanol as molecular probe. Increasing the solution pH from 4.8 to 10.4, the photodegradation rate slightly decreased from 0.00246 min⁻¹ to 0.00195 min⁻¹, probably due to pH-dependent effect of nitrate-induced OH formation. Bicarbonate decreased the photodegradation of ATL in the presence of nitrate ions mainly through pH effect, while humic substance inhibited the photodegradation via both attenuating light and competing radicals. Upon irradiation for 240 min, only 10% reduction of total organic carbon (TOC) can be achieved in spite of 72% transformation rate of ATL, implying a majority of ATL transformed into intermediate products rather than complete mineralization. The main photoproducts of ATL were identified by using solid phase extraction-liquid chromatography-mass spectrometry (SPE-LC-MS) techniques and possible nitrate-induced photodegradation pathways were proposed. The toxicity of the phototransformation products was evaluated using aquatic species Daphnia magna, and the results revealed that photodegradation was an effective mechanism for ATL toxicity reduction in natural waters.     

废水中2,6-二硝基酚厌氧毒性和降解动力学研究

在中温(35℃±1℃)厌氧条件下,以葡萄糖为共基质,采用间歇实验方法,研究了2,6-二硝基酚(2,6-DNP)的厌氧产甲烷毒性和厌氧降解动力学.厌氧毒性试验(ATA)以累计产甲烷量和相对活性(RA)为指标,评价了不同浓度2,6-DNP对产甲烷菌的抑制程度;结果表明,2,6-DNP浓度＜20 mg/L时,对产甲烷菌没有抑制作用,浓度为40 mg/L时产生轻度抑制,浓度为80～120 mg/L时产生重度抑制;24 h 2,6-DNP的75%、50%、25%相对抑制浓度分别为30、70和＞120 mg/L.2,6-DNP降解动力学可用Haldane方程来描述,利用非线性拟合求得动力学参数Ks、Rm、Ki分别为179.7 mg/L、4.84 mg/g VSS·h、206.5 mg/L,方差R2=0.94,拟合效果很好.     

Photodegradation of malachite green under natural sunlight irradiation: kinetic and toxicity of the transformation products

This article describes the photolytic degradation of malachite green (MG), a cationic triphenylmethane dye used worldwide as a fungicide and antiseptic in the aquaculture industry. Photolysis experiments were performed by direct exposure of a solution of MG in water to natural sunlight. The main transformation products (TPs) generated during the process were identified by liquid chromatography time-of-flight mass spectrometry (LC–TOF-MS) and gas chromatography mass spectrometry (GC–MS). The 28 TPs identified with this strategy indicate that MG undergoes three main reactions, N-demethylation, hydroxylation and cleavage of the conjugated structure forming benzophenone derivatives. These processes involve hydroxyl radical attack on the phenyl ring, the N,N-dimethylamine group and the central carbon atom. The Vibrio fischeri acute toxicity test showed that the solution remains toxic after MG has completely disappeared. This toxicity could be assigned, at least in part, to the formation of 4-(dimethylamine)benzophenone, which has an EC_50,30 min of 0.061 mg l⁻¹, and is considered “very toxic to aquatic organisms” by current EU legislation.     

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...