Assessment of the relative toxicity of Cu2+ by measuring structural changes of supercoiled DNA

A method for the measurement of the relative toxicity of Cu2+ in aquatic environments is proposed. It is based on the quantitative measurement on the shape change of the supercoiled DNA after it is contacted with different levels of Cu2+ for various time intervals. In the absence of any redox reagents, all supercoiled DNA degraded into other forms of DNA after 24h incubation in the presence of 5.13 x 10(-3), 5.08 x 10(-4) and 5.35 x 10(-5)mol/L Cu2+. At a lower Cu2+ concentration (10(-6)mol/L), 44% of supercoiled DNA retained its original supercoiled form after 24 h, and 29% after 48 h. The concentration of RC50, i.e. concentration of pollutants at which 50% of the supercoiled DNA was relaxed compared to control samples, can be obtained from the does-response curves at different exposure time, which may provide a rapid and convenient approach to assess the relative toxicity of environmental pollutants.     

淮安市农产品中重金属及有机氯、有机磷农药残留量调查

淮安市环境监测中心站于1999年－2000年对淮安市农产品中重金属以及有机氯、有机磷农药残留量进行了调查。结果表明，粮食和蔬菜作物中，六六六的4种同分异构体只有γ－六六六能检出，检出率分别为24．0％和51．7％，都未超标；DDT的4种同分异要体均未检出；有机磷农药的检出率分别为5％和25％，其中蔬菜中敌敌畏含量出现个别超标现象，倍硫磷、乐果和杀螟松在粮食和蔬菜作物中的含量都不超标。重金属中金属“五毒”在粮食和蔬菜作物中，只有Cr和Pb能检出，Cd、Hg和As都未检出，Cu、Zn和Mn能检出，但不超标。提出，应严格按照农牧渔业部和卫生部颁发的《农药安全使用规定》用药，多使用高效低残留量的“绿色农药”；农业、环保和卫生部门必须加强合作，对蔬菜生产销售的全过程进行监督监测，以确保生产无公害蔬菜。     

外源锌对镉胁迫下玉米幼苗生长及根系构型分级的影响

为探究不同浓度锌（Zn）对镉（Cd）胁迫条件下玉米幼苗生长及根系构型分级的影响,通过水培试验,以玉米品种郑单958为试验材料,研究Cd胁迫条件下（50 μmol·L^-1）,外源施加不同浓度Zn（0、10、25、50、100、200和400 μmol·L^-1）对玉米幼苗生长、根系构型及其分级特征、Cd含量及根系Cd吸收能力、光合系统的影响,并通过主成分分析和隶属函数法进行综合评价.结果表明,50 μmol·L^-1 Cd胁迫对玉米幼苗具有明显的毒害作用,使叶绿素含量和光合参数显著降低,主根长、株高、生物量、根分枝数和根尖数,包括Ⅰ~Ⅲ级径级区间的根长、根表面积及Ⅰ~Ⅱ级径级区间的根体积显著下降,阻碍了玉米幼苗的正常生长发育.施用100 μmol·L^-1和200 μmol·L^-1 Zn与不施Zn相比,降低了玉米幼苗对Cd的吸收,显著降低了Cd含量和Cd吸收效率,缓解了对玉米幼苗的毒害作用,使地上地下部鲜重、地上部干重、地上地下部耐受指数和根分枝数均显著升高;显著增强了玉米幼苗的光合作用,促使幼苗光合速率和总叶绿素含量显著升高;Ⅰ级径级区间的RL、Ⅰ~Ⅱ级径级区间的SA和RV在100 μmol·L^-1 Zn时达到最大,Ⅲ级径级区间的RL、SA和RV在200 μmol·L^-1 Zn时达到最大,均显著高于不施Zn处理;玉米幼苗生长耐受性综合评价表明,100 μmol·L^-1和200 μmol·L^-1 Zn缓解Cd毒害作用效果较好.综合分析可知,施加适宜浓度的Zn可以降低玉米幼苗植株内Cd含量、根系Cd吸收能力及Cd吸收效率,提高玉米幼苗生物量的积累,减轻Cd毒害对根系构型的影响,减少对光合系统的影响,提高玉米幼苗对Cd的耐受性.     

静电放电电磁辐射模式的建立与仿真

介绍了静电放电电磁辐射场的理论模型;针对长导体模型分析了其数学模型的建立方法;讨论了长导体模型实验仿真方法与结果.     

城乡养狗隐患多

近几年来,对于城乡居民来说,养狗已是生活中的一部分。然而狗养多了,隐患也会出现。一是盲目养狗、只养少管。尤其是农村,很多家庭养狗,少则一只,多则二三只,以散养为主。这些狗到处乱窜,咬人伤人,防不胜防。二是养狗户防疫知识欠缺,养狗者为狗打     

Prenatal sonographic appearance of Beare-Stevenson cutis gyrata syndrome: two- and three-dimensional ultrasonographic findings

Beare-Stevenson cutis gyrata syndrome is characterized by craniofacial anomalies, particularly craniosynostosis, ear defects, cutis gyrata, acanthosis nigricans, anogenit anomalies, skin tags, and prominent umbilical stump. The prenatal two- and three-dimensional ultrasonographic findings of this rare condition is reported. The detection was made at 32 weeks of gestation in a woman with polyhydramnios and fetal head anomaly. The ultrasound appearance and postnatal follow‒up are presented. Copyright © 2001 John Wiley & Sons, Ltd.     

Photodegradation of the endocrine-disrupting chemical 4-nonylphenol in biosolids applied to soil

There is increasing concern about the environmental fate and impact of biosolids-associated anthropogenic organic chemicals, among which 4-nonylphenol (4-NP) is one of the most studied chemicals. This is primarily because 4-NP is an endocrine disruptor and has been frequently detected in environmental samples. Due to its high hydrophobicity, 4-NP has high affinity for biosolids. Land application of 4-NP-containing biosolids could potentially introduce large quantities of this chemical into the environment. A laboratory experiment was conducted to investigate the effect of artificial sunlight on 4-NP degradation in biosolids applied to soil. When exposed to artificial sunlight for 30 d, the top-5-mm layer of biosolids showed a 55% reduction of 4-NP, while less than 15% of the 4-NP was degraded when the biosolids were kept in the dark. Our results indicate that sensitized photolysis reaction plays an important role in reducing the levels of 4-NP in land-applied biosolids. Surface application rather than soil incorporation of biosolids could be effective in reducing biosolids-associated organic chemicals that can be degraded through photolysis reactions. However, the risks of animal ingestion, foliar deposition, and runoff should also be evaluated when biosolids are applied on the soil surface.     

Relationship between air pollution and daily mortality in a subtropical city: Taipei, Taiwan

Air pollution has been associated with daily mortality in numerous studies over the past decade. However most of these studies were conducted in the United States and Europe with relatively few done in Asia. In the current study, the association between ambient air pollution and daily mortality in Taipei, Taiwan's largest city which has a subtropical climate was undertaken, for the period 1994-1998 using a case-crossover analysis. This design is an alternative to Poisson time series regression for studying the short-term adverse health effects of air pollution. The air pollutants examined included particulate matter (PM(10)), sulfur dioxide (SO(2)), ozone (O(3)), nitrogen dioxide (NO(2)), and carbon monoxide (CO). The largest observed effect, which was without statistical significance, was seen for NO(2) and CO levels on deaths due to respiratory diseases (ORs=1.013 and 1.014, respectively). The well established link between air pollution levels and daily mortality may not be as strong in cities in subtropical areas, although other factors such as differences in pollutant mix or the underlying health of the population may explain the lack of a strong association in this study. Further studies of this type in cities with varying climates and cultures are needed.