Effect of temperature,organic amendment rate and moisture content on the degradation of 1,3‐dichloropropene in soil

1,3‐Dichloropropene (1,3‐D), which consists of two isomers, (Z)‐ and (E)‐1,3‐D, is considered to be a viable alternative to methyl bromide, but atmospheric emission of 1,3‐D is often associated with deterioration of air quality. To minimize environmental impacts of 1,3‐D, emission control strategies are in need of investigation. One approach to reduce 1,3‐D emissions is to accelerate its degradation by incorporating organic amendments into the soil surface. In this study, we investigated the ability of four organic amendments to enhance the rate of degradation of (Z)‐ and (E)‐1,3‐D in a sandy loam soil. Degradation of (Z)‐ and (E)‐1,3‐D was well described by first‐order kinetics, and rates of degradation for the two isomers were similar. Composted steer manure (SM) was the most reactive of the organic amendments tested. The half‐life of both the (Z)‐ and (E)‐isomers in unamended soil at 20 °C was 6.3 days; those in 5% SM‐amended soil were 1.8 and 1.9 days, respectively. At 40 °C, the half‐life of both isomers in 5% SM‐amended soil was 0.5 day. Activation energy values for amended soil at 2, 5 and 10% SM were 56.5, 53.4 and 64.5 kJ mol^?1, respectively. At 20 °C, the contribution of degradation from biological mechanisms was largest in soil amended with SM, but chemical mechanisms still accounted for more than 58% of the (Z)‐ and (E)‐1,3‐D degradation. The effect of temperature and amendment rate upon degradation should be considered when describing the fate and transport of 1,3‐D isomers in soil. Use of organic soil amendments appears to be a promising method to enhance fumigant degradation and reduce volatile emissions. Published in 2001 for SCI by John Wiley & Sons, Ltd     

烯唑醇的顺反立体异构体分析方法研究

通过气相色谱和高效液相色谱法研究分析了烯唑醇的顺/反异构体分离方法.正相和反相HPLC的条件如下不锈钢柱200 mm×5 mm(i.d.),填料YWG-Si 10 μm,流动相正己烷-异丙醇为95+5(V/V)或者用正己烷-无水乙醚-无水甲醇89+9+2(V/V),流速2.0 mL·min-1,检测波长254 nm;不锈钢柱200 mm×5 mm(i.d.),填料YWG-C1810 μm,流动相甲醇-水-乙酸为70+30+0.35(V/V),流速1.0 mL·min-1.气相色谱的条件熔融石英毛细管柱10m×0.53 mm×1.0 μm膜厚,用聚乙二醇-20000涂渍,柱温160℃,进样口和检测器温度250℃,载气H216 mL·min-1.在上述气相色谱的条件下,烯唑醇顺/反异构体能达到部分分离.     

水库微囊藻毒素3种异构体的年变化过程研究

应用高效液相色谱,对华北地区某水库5个采样点水体中微囊藻毒素（MC-LR、RR和YR）3种异构体进行了为期1a的监测,研究3种异构体随时间的变化规律及相互关系。结果表明,水体中3种异构体（-LR、YR和RR）含量分别为0.941±1.338、0.365±0.647和（2.893±5.387）μg·L-1;3种异构体出现时间不一样,LR异构体出现时间最早,在4月下旬即可检测到,而RR和YR异构体则需到5月中旬才能检测到;3种异构体峰值出现时间也不一致,LR和YR异构体峰值出现在8—9月,而RR异构体出现时间较晚,到10—11月才达到全年最高值;LR和RR异构体的含量比较高,是主要毒素,5—11月,其比值由2.20降到0.04,这与水体中的N/P比值有关,它随N/P比值的减少而减少。     

金霉素及其异构体降解产物对斜生栅藻的毒性效应研究

为探索水体中四环素类抗生素异构体降解产物的毒性效应,选取金霉素及其异构体降解产物为目标化合物,斜生栅藻(Scenedesmus obliquus)为受试生物,结合藻类生理指标探讨金霉素及其异构体降解产物的毒性效应。研究结果表明,在斜生栅藻藻液中,金霉素主要的异构体降解产物为异金霉素及异差向金霉素。暴露72 h后,金霉素及其异构体降解产物处理组的藻细胞形态发生了明显的质壁分离,且细胞通透性均显著增大。但是,金霉素母体药物与不同异构体降解产物对斜生栅藻的毒性效应表现出了明显的差异。金霉素母体药物处理组的斜生栅藻细胞中可溶性蛋白质和叶绿素a浓度降低得更为显著,且氧化损伤更为严重。金霉素母体药物与其异构体降解产物虽然具有相似的化学结构,但取代基空间构象的不同会导致药物与藻细胞中的可溶性蛋白质的结合位点不同,因而对藻细胞产生不同的毒性效应。探究金霉素及其异构体降解产物对水生环境产生的毒性效应,有望为全面认识四环素类抗生素的生态环境风险提供新的依据。     

水库微囊藻毒素3种异构体的年变化过程研究

应用高效液相色谱,对华北地区某水库5个采样点水体中微囊藻毒素(MC-LR、RR和YR)3种异构体进行了为期1a的监测,研究3种异构体随时间的变化规律及相互关系。结果表明,水体中3种异构体(-LR、YR和RR)含量分别为0.941±1.338、0.365±0.647和(2.893±5.387)μg·L-1;3种异构体出现时间不一样,LR异构体出现时间最早,在4月下旬即可检测到,而RR和YR异构体则需到5月中旬才能检测到;3种异构体峰值出现时间也不一致,LR和YR异构体峰值出现在8—9月,而RR异构体出现时间较晚,到10—11月才达到全年最高值;LR和RR异构体的含量比较高,是主要毒素,5—11月,其比值由2.20降到0.04,这与水体中的N/P比值有关,它随N/P比值的减少而减少。     

乳酸菌剂对青贮饲料发酵品质的改善效果

 为探讨添加乳酸菌对青贮饲料发酵过程中微生物的动态变化、发酵品质及乳酸异性体生成比率的影响，以意大利黑麦草（Lolium multiflorum）为材料草，选用2种乳酸球菌及1种乳酸杆菌进行青贮饲料的添加调制。其结果如下：⑴乳酸球菌添加区，于贮藏初期，乳酸球菌旺盛繁殖；乳酸杆菌添加区，在发酵全过程保持了高水准的乳酸杆菌数，促进了乳酸发酵。⑵添加乳酸菌有效地抑制了与青贮饲料共存的丝状菌（霉菌）、酵母菌及一般细菌的繁殖，其制菌效果，乳酸杆菌大于乳酸球菌。⑶添加乳酸菌使pH值及挥发性氮与全氮（VBN/T-N）比值降低，乳酸含量提高，改善了青贮饲料发酵品质。⑷乳酸菌添加改善了L（+）乳酸的生成比率，与无添加区相比，乳酸球菌添加区和乳酸杆菌添加区分别提高了7%-8%和12%-14%。     

Effects of reactive radicals and heat on <Emphasis Type="Italic">trans</Emphasis>-isomerization of eicosapentaenoic acid

Trans geometric isomers of eicosapentaenoic acid (TEPA) have been found as minor components in human platelets. However, there is little information on the mechanism of trans-isomerization of eicosapentaenoic acid (EPA) in vitro and in vivo. The effects of reactive radicals and heat on trans-isomerization of EPA were examined. Trans-isomerization occurred when EPA ethyl ester reacted with nitrogen dioxide radical (NO₂) but not with 2,2′-azobis(2,4-dimethylvaleronitrile). TEPA was also produced from EPA ethyl ester heated at 200°C for 60 h. No TEPA, however, was detected in sardines Sardinops melanostictus after boiling, roasting, or microwave heating. These results suggest that EPA is trans-isomerized by NO₂ in vivo while trans-isomerization of EPA does not occur during conventional cooking.     

Compositions of fatty acid hydroperoxide positional isomers in sweet smelt, yellowtail and rainbow trout livers phosphatidylcholine

ABSTRACT: Hydroxy fatty acid isomers derived from phosphatidylcholine hydroperoxides (PC-OOH) in the livers of three fish species, including sweet smelt, yellowtail and rainbow trout, were determined by selected ion monitoring of gas chromatography/mass spectrometry. Total molar amounts of all hydroxy fatty acids determined in the present study coincided well with those of PC-OOH reported previously, suggesting that hydroxy fatty acid composition reflects hydroperoxide composition. The total amount of hydroperoxide isomers accumulated in the livers of sweet smelt was much higher than those of yellowtail and rainbow trout. The amounts of certain isomers, including 10-hydroperoxy octadecanoic acid, 12-hydroperoxy eicosanoic acid and 14-hydroperoxy docosanoic acid, were significantly higher than those of rainbow trout and yellowtail. These results suggest that differences in the contents and compositions of certain hydroperoxide isomers, which are possible precursors of a watermelon-like or cucumber-like aroma, result in differences of fresh fish aroma between aromatic fish and non-aromatic fish.     

The use of gas‐liquid chromatography to determine the proportions of inositol isomers present as pentakis‐ and hexakisphosphates in alkaline extracts of soils

Abstract

A method for determining the relative proportions of inositol isomers present in soil as their pentakis‐ and hexakisphosphate derivatives (IP₅ + IP₆) is presented. The method involves determination of the isomers as their hexakis‐O‐acetyl derivatives by gas‐liquid chromatography. The only isomers detected in extracts of 4 soils were chiro‐inositol, neo‐inositol, myo‐inositol and soyllo‐to‐inositol. Little variation in the relative proportions of the isomers was found between the 4 soils but the relative proportion of the neo‐isomer was considerably greater than previously published estimates. The method also makes possible the estimation of the (IP₅ + IP₆) fraction, using anion‐exchange chromatography on a aliquot of the extract.