副干酪乳杆菌X12抑制N-二甲基亚硝胺诱导IEC-6细胞损伤作用研究

目的 选用分离自新疆传统发酵奶酪,且具有潜在益生功能的副干酪乳杆菌X12（L. paracasei subsp. paracasei X12）进行实验,分析其抑制NDMA（N-nltrosodimethylamine,N-二甲基亚硝胺）诱导IEC-6细胞（大鼠肠道黏膜细胞）毒性损伤的作用。方法 通过胃液、肠液耐受性实验、扫描电镜法分析副干酪乳杆菌X12益生功能和菌株的形态;通过CCK-8实验对副干酪乳杆菌X12抑制NDMA诱导IEC-6毒性作用进行分析。结果 胃肠道耐受性实验显示,副干酪乳杆菌X12可耐受胃肠液的消化,但对胆盐耐受性略差些;扫描电镜下副干酪乳杆菌X12菌体呈短而圆的杆状结构,无鞭毛;CCK-8实验结果显示,在MRS培养基中NDMA（0～80 μg/mL）对副干酪乳杆菌X12的生长无显著影响,反之亦然;副干酪乳杆菌X12可抑制NDMA致大鼠肠道黏膜细胞IEC-6毒性的作用,且该作用与副干酪乳杆菌X12的剂量有关。结论 副干酪乳杆菌X12可抑制NDMA诱发的IEC-6细胞毒性损伤。     

Impact of IX-UF Pretreatment on the Feasibility of UV/H2O2 Treatment for Degradation of NDMA and 1,4-Dioxane

PWN considers ion exchange and ultrafiltration (IX-UF) for replacing the existing CSF pretreatment at the Andijk water treatment plant. Advanced oxidation (UV/H₂O₂) in combination with granular activated carbon filtration (GAC) as a non selective barrier against organic micro pollutants is operational since 2004. Effects of an improved pretreatment on the UV/ H₂O₂ in terms of direct photolysis, OH-radical oxidation and energy consumption are presented in this paper. NDMA and 1,4-dioxane are selected to show the impact of pretreatment on UV photolysis and hydroxyl radical oxidation, respectively. Key water quality parameters are DOC and nitrate for scavenging and competition for UV light. Compared to CSF, the electrical energy per order (EEO) for IX-UF treated water was reduced with about 50%.     

消毒副产物N-亚硝基二甲胺的生成规律研究

为了研究氨氮和有机氮化合物共存体系加氯消毒条件下N-亚硝基二甲胺（NDMA）的生成规律,采用50mg/L氨氮加氯消毒再与30mg/L 的二甲胺（DMA）反应,首先研究了反应时间、氯胺浓度、pH值、氯氮比（自由氯与氨氮的质量比）对NDMA生成量的影响;然后在此基础上选取废水体系中具有代表性的3种有机氮化合物尿素、甘氨酸、苯丙氨酸,重点考察了这3种有机氮化合物对氯胺以及对NDMA生成情况的影响。结果表明：pH值和氯氮比对NDMA生成量影响最大;氨氮溶液中加入有机氮化合物后加氯消毒,会使生成一氯胺浓度的峰值点向氯氮比增大的方向移动,同时会降低同一氯氮比下NDMA的生成量。     

NDMA formation kinetics from three pharmaceuticals in four water matrices

N, N-nitrosodimethylamine (NDMA) is an emerging disinfection by-product (DBP) that has been widely detected in many drinking water systems and commonly associated with the chloramine disinfection process. Some amine-based pharmaceuticals have been demonstrated to form NDMA during chloramination, but studies regarding the reaction kinetics are largely lacking. This study investigates the NDMA formation kinetics from ranitidine, chlorphenamine, and doxylamine under practical chloramine disinfection conditions. The formation profile was monitored in both lab-grade water and real water matrices, and a statistical model is proposed to describe and predict the NDMA formation from selected pharmaceuticals in various water matrices. The results indicate the significant impact of water matrix components and reaction time on the NDMA formation from selected pharmaceuticals, and provide fresh insights on the estimation of ultimate NDMA formation potential from pharmaceutical precursors.     

Analysis of N-nitrosamines and other nitro(so) compounds in water by high-performance liquid chromatography with post-column UV photolysis/Griess reaction

Despite their potential carcinogenicity and probable formation during water disinfection processes, little is known about the occurrence of other nitro(so) compounds than a few specific N-nitroso compounds such as N-nitrosodimethylamine (NDMA). An analytical method was developed to monitor various nitro(so) compounds including N-nitrosamines based on the Griess colorimetric determination of nitrite generated by UV-254 nm photolysis of nitro(so) compounds after separation by HPLC (HPLC-Post Column UV photolysis/Griess reaction (HPLC-PCUV)). To differentiate N-nitro(so) compounds (i.e. UV-labile) from other nitro(so) and N-containing compounds (i.e. UV-resistant), a pre-treatment was established by photolyzing solid-phase extracted samples at 254 nm (1000 mJ/cm²) and thus removing N-nitro(so) compounds selectively. Considering a 1000-fold concentration factor and extraction efficiencies (57–83%) during solid phase extraction, the method detection limits ranged from 4 to 28 ng/L for dimethylnitramine and eight N-nitrosamines (EPA 8270 nine nitrosamines mixture except for N-nitrosodiphenylamine). For four pool waters, the UV-resistant groups accounted for more than 78% of the estimated total concentration of nitro(so) and other N-containing compounds (6.1–48.6 nM). Only one unknown UV-labile compound was detected in one pool water (2.0–7.9 nM). NDMA was most frequently detected and N-nitrosodipropylamine (NDPA) and N-nitrosodibutylamine (NDBA) were additionally detected in one pool water. Chloramination of a secondary wastewater effluent with NDMA (0.2 nM) and UV-resistant compounds (7.9 nM) from a pilot-scale municipal wastewater treatment plant led to a significant formation of not only unidentified UV-resistant compounds (67.8 nM) and UV-labile compounds (14.6 nM), but also identified nitrosamines such as NDMA (4.3 nM), N-nitrosopiperidine (1.8 nM), NDPA (0.5 nM), and NDBA (0.5 nM). Overall, the novel HPLC-PCUV system is a powerful screening tool for the detection of (un)known N-nitro(so) as well as other nitro(so) and UV-induced nitrite-producing compounds.     

Oxidative degradation of N-nitrosodimethylamine by conventional ozonation and the advanced oxidation process ozone/hydrogen peroxide

This study investigates the oxidative degradation of N-nitrosodimethylamine (NDMA), a probable human carcinogen, by conventional ozonation and the advanced oxidation process ozone/hydrogen peroxide (AOP O(3)/H(2)O(2)). The rate constants of reactions of NDMA with ozone and hydroxyl radical ((*)OH) were determined to be 0.052+/-0.0016M(-1)s(-1) and (4.5+/-0.21)x10(8)M(-1)s(-1), respectively. The experiments performed with buffered deionized water varying solution pH and employing H(2)O(2) and HCO(3)(-) clearly showed that the reaction with (*)OH dominates the NDMA oxidation during ozonation. Conventional ozonation with up to 160 microM (=7.7 mgL(-1)) ozone led to less than 25% NDMA oxidation in natural waters. The AOP O(3)/H(2)O(2) required 160-320 microM ozone ([O(3)](0)/[H(2)O(2)](0)=2:1) to achieve 50-75% NDMA oxidation. However, multiple injections of ozone of the same overall dose somewhat improved the oxidant utilization efficiency by minimizing (*)OH scavenging contribution of oxidants. Methylamine (MA) was found to be a major amino product from NDMA oxidation initiated by (*)OH. The mechanism of NDMA oxidation to MA is discussed based on the results obtained in this study and the previous literature. Bromate formation may be the limiting factor for NDMA oxidation during ozonation and ozone-based AOPs in bromide-containing waters.     

氯化消毒副产物NDMA的生成与控制研究进展

NDMA（N-Nitrosodimethylamine）是水处理领域新近发现的一种氯化消毒副产物,由于其具有检出率高、致癌风险大、难以有效去除等特性,已成为国际关注的重要水质问题之一。饮用水中的NDMA主要产生于氯化消毒过程,尤为严重的是氯胺消毒过程,而臭氧和过氧化氢氧化基本不产生NDMA。NDMA为亲水性小分子有机物,常规处理和深度处理均难于有效去除,而且管网中的浓度显著高于出厂水。目前控制饮用水中NDMA的常用方法是紫外线照射,但能耗较高。其他方法如延长自由氯接触时间和采用高铁酸盐预氧化、反渗透、臭氧／过氧化氢高级氧化工艺等也可以不同程度地控制NDMA及其前体物。     

模拟条件下香辛类蔬菜对N-二甲基亚硝胺形成的影响

研究采用体外模拟条件及亚硝化反应体系,探究大葱、生姜、大蒜、洋葱4种香辛类蔬菜的冻干粉及其可溶性组分干粉对N-二甲基亚硝胺(N-nitrosodimethylamine,NDMA)形成的影响。结果表明:香辛类蔬菜的种类和添加量、亚硝化反应体系的温度、时间等都对NDMA的形成表现出不同程度的促进或抑制作用。在模拟温度(腌制(4±1)℃、室温(25±1)℃、低温加工(80±1)℃)条件下,大葱粉、洋葱粉及生姜粉均明显促进NDMA形成(P0.05),且80℃时促进率最大;同一温度条件下,随反应时间延长,大葱粉和洋葱粉对NDMA形成的促进作用明显增强(P0.05),生姜粉对NDMA形成没有显著影响(P0.05);在同一温度同一反应时间内,随香辛类蔬菜粉添加量增加,对NDMA形成的促进作用显著增强(P0.05)。但在4℃或25℃时,大蒜粉及生姜水溶性组分干粉对NDMA形成表现为抑制作用,其中生姜水溶性组分干粉抑制作用较弱(10%);在80℃时大蒜粉表现为促进NDMA的形成。实验说明4类香辛类蔬菜在模拟条件下对NDMA的形成未能起到抑制作用。     

八角和丁香提取方法对NDMA阻断效果的影响

采用体外模拟亚硝化反应的条件,优选对二甲基亚硝胺(NDMA)阻断效果较强的香辛料提取液的提取方法。实验选用干燥的八角果实和丁香花蕾为原料,利用水浸提法、索氏提取法、超声-微波辅助溶剂萃取法得到了这2种香辛料的水溶物和精油成分。结果表明:采用水浸提法得到的八角水溶物对NDMA的抑制效果较弱,而丁香水溶物则对NDMA的产生没有抑制作用;采用索氏提取法得到的八角和丁香精油成分对NDMA均有较高的抑制作用。在3种方法中,超声-微波法提取的物质抑制作用最强,利用正交方法得到两种精油对NDMA的阻断效果最佳提取条件为:八角在料液比为1:25(g/mL)、60℃下浸取20 min可使抑制率达到80.32%,丁香利用1:25(g/mL)的料液比,在60℃下浸取30min可使抑制率达到79.45%。