中国烤烟含氯农残总量状况及其控制措施探讨

分析了中国2003—2005年2816份烤烟样品含氯农残总量在不同产区、不同品种、不同等级和不同年份间的变异,结果表明:中国烟叶含氯农残总量在样品间存在广泛的变异,变幅为0.00～5.40mg/kg,平均值为0.372mg/kg,变异系数为223.38%,有350个烟叶样品未检出,占总样品数的12.43%。其中云南(0.781mg/kg)、湖南(0.663mg/kg)烟叶样品的含氯农残总量较高,辽宁(0.037mg/kg)、四川(0.041mg/kg)烟叶样品的含氯农残总量较低;烤烟品种G80样品的含氯农残总量(0.599mg/kg)较高,9717品种样品的含氯农残总量(0.033mg/kg)较低;不同等级烟叶含氯农残总量表现为C2F>B2F>C3F>X2F;不同年份的烟叶含氯农残总量表现为2003年>2005年>2004年。针对中国烤烟含氯农残的状况,提出了控制烤烟农残含量、提高烟叶安全性的主要措施。     

Prediction and Analyses of Residual Chlorine Based on Support Vector Regression in Urban Water Distribution System

Support vector regression(SVR) algorithm is an application of structural risk minimization principle in function regression.In this paper,a residual chlorine prediction model based on SVR is established by using the data of manual sampling residual chlorine of water distribution system in a certain city in the north of China.SVR model is compared with the artificial neural network and multivariate linear regression.The result shows that SVR model has better generalization ability for small samples,the predicted average relative error of all monitoring points is 1.80%~8.73%,and can achieve unique and globally optimal solutions.It is practical and can solve the problem for small samples of residual chlorine when the fit precision of model is good but the predicted effect is worse.     

二氧化氯在蔬菜保鲜中的应用研究进展

综述了二氧化氯的性质、作用机理、安全性及近年来国内外二氧化氯在蔬菜保鲜中的应用研究状况,展望了二氧化氯在蔬菜保鲜中的应用前景.     

氯钾离子共体诱导后黄瓜叶片内几种酶活性的变化

在黄瓜幼苗子叶期及第一真叶期用不同浓度的氯钾离子共体液进行诱导处理,测定黄瓜叶片中的酶活性。结果表明:诱导后各处理的SOD活性均显著高于对照,且呈先升高后降低的趋势,到诱导后10 d各处理达到最大值;POD活性也呈先升高后降低的趋势,诱导初期对照和各处理变化平缓,10 d后急剧升高,15 d达最大值,之后下降,且经诱导后各处理均高于对照;脲酶活性均高于对照,随着时间的推移呈先升高后降低的趋势,诱导后10 d达到峰值。在诱导物浓度为0.5%~1.5%的范围内,黄瓜叶片内各生理生化指标较对照差异最大。     

不同质量浓度二氧化氯对三种河蟹致病菌的杀灭效果

以1％的Na2S2O3为中和剂，测定了五种质量浓度100，20，4，0．8，0．16mg/L ClO2溶液对副溶血弧菌、毛霉亮发菌以及嗜水气单胞菌等河蟹致病菌的杀灭效果。同时以蛋白胨质量为材料测定了有机物对ClO2杀菌效果的影响。结果表明：0．8mg/L的ClO2作用15min、0．16mg/L的ClO2作用30min可有效杀灭三种致病菌；蛋白胨浓度为25mg/L时，对ClO2的杀菌效果几乎没有影响，蛋白胨质量浓度为25mg/L时，ClO2作用15min的杀菌率下降为97．5％，蛋白胨质量浓度为625mg/L时下降为95．5％。     

硫酸盐法竹浆无元素氯漂白的研究

研究了硫酸盐法竹浆低二氧化氯用量的DQP漂白中各个漂段的影响因素,并对D段终点pH值、Q段EDTA用量以及P段MgSO4用量进行优化.结果表明:当D段终点pH值为4,Q段EDTA用量为0.2%,P段MgSO4用量为0.02%(以Mg2+计),DQP漂白效果较好.仅用1.5%的有效氯(0.57%的ClO2)和1.5%的H2O2,就可将硫酸盐竹浆漂到83%ISO的白度.还对竹浆DQP和CEH漂白的漂终结果、纸浆强度性质以及废水特性进行了比较.结果表明:与CEH漂白相比,DQP漂白浆的白度稍低,但白度稳定性好,纸浆粘度高,强度性质较好,对环境污染较小.     

Effects of Chlorine Dioxide Gas on Postharvest Physiology and Storage Quality of Green Bell Pepper （Capsicum frutescens L. var. Longrum）

The effects of treatment of chlorine dioxide (ClO2) gas on postharvest physiology and preservation quality of green bell peppers were studied. Green bell peppers were collected in bags and treated with 0, 5, 10, 20, and 50 mg L-1 ClO2 gas at 10 ± 0.5℃ for over 40 d, and the changes in postharvest physiology and preservation quality of the peppers were evaluated during the storage. The inhibition of rot of the peppers was observed for all the tested ClO2 gas treatments. The rot rates of the treated samples were 50% lesser than those of the control after day 40 of storage. The highest inhibitory effect was obtained after 50 mg L-1 ClO2 gas treatment, where the peppers did not decay until day 30 and showed only one-fourth of the rot rate of the control at day 40 of storage. The respiratory activity of the peppers was significantly (P ＜ 0.05) inhibited by 20 and 50 mg L-1 ClO2 treatments, whereas no significant effects on respiratory activity were observed with 5 and 10 mg L-1ClO2 treatments (P＞ 0.05). Except for 50 mg L-1 ClO2, malondialdenyde (MDA) contents in the peppers treated with 5,10, or 20 mg L-1 ClO2 were not significantly (P＞0.05) different from those in the control. Degradation of chlorophyll in the peppers was delayed by 5 mg L-1 ClO2, but promoted by 10, 20, or 50 mg L-1 ClO2. The vitamin C content, titratable acidity,and total soluble solids of the peppers treated by all the tested ClO2 gas did not significantly change during the storage.The results suggested that ClO2 gas treatment effectively delayed the postharvest physiological transformation of green peppers, inhibited decay and respiration, maintained some nutritional and sensory quality, and retarded MDA accumulation.     

Chemical control of bacterial soft-rot of wounded potato tubers

Summary Five chemicals were applied to batches of wounded potato tubers by dipping in 1.5 g litre solutions for 1 min. After incubation for 10 days at 15 C under damp anaerobic conditions the amount of bacterial soft rotting was assessed. 5-nitro-8-hydroxyquinoline was the most effective in reducing rotting but 8-hydroxyquinoline, SD740823AX and chlorine dioxide also gave some control. Elbadyne had no significant effect. The results of tests in vitro were in broad agreement with those of tests in vivo for 5-nitro-8-hydroxyquinoline, 8-hydroxyquinoline and SD740823AX, but not Elbadyne and chlorine dioxide. The feasibility of controlling soft rotting by chemicals is demonstrated and screening procedures are discussed.