兽药抗生素对土壤微生物群落的影响

兽药抗生素广泛应用于畜禽养殖业,用于预防、治疗动物疾病及促进动物生长。然而,养殖过程中使用的抗生素不能被动物完全吸收,其中40%～90%以母体或其代谢物的形式排出动物体外并随畜禽粪便进入土壤环境,对土壤微生物群落结构和功能产生影响。在汇总了畜禽粪便和土壤中兽药抗生素的残留特征之后,概述了抗生素对土壤微生物群落结构和功能的影响以及微生物产生的污染诱导群落耐性。重点探讨了抗生素微生物毒性的影响因素和近年来对微生物共耐性方面的研究,并对未来的研究方向及目标提出了建议。     

Distribution pattern of polycyclic aromatic hydrocarbons in particle-size fractions of coking plant soils from different depth

The concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) in four size fractions (<2, 2–20, 20–200, >200 μm) in soils at different depth from a heavily contaminated crude benzol production facility of a coking plant were determined using GC–MS. Vertically, elevated total PAHs concentrations were observed in the soils at 3.0–4.5 m (layer B) and 6.0–7.5 m (layer C), relatively lower at 1.5–3.0 m (layer A) and 10.5–12.0 m (layer D). At all sampling sites, the silt (2–20 μm) contained the highest PAHs concentration (ranged from 726 to 2,711 mg/kg). Despite the substantial change in PAHs concentrations in soils with different particle sizes and lithologies, PAHs composition was similarly dominated by 2–3 ring species (86.5–98.3 %), including acenaphthene, fluorene, and phenanthrene. For the contribution of PAHs mass in each fraction to the bulk soil, the 20–200 μm size fraction had the greatest accumulation of PAHs in loamy sand layers at 1.0–7.5 m, increasing with depth; while in deeper sand layer at 10.5–12.0 m, the >200 μm size fraction showed highest percentages and contributed 81 % of total PAHs mass. For individual PAH distribution, the 2–3 ring PAHs were highly concentrated in the small size fraction (<2 and 2–20 μm); the 4–6 ring PAHs showed the highest concentrations in the 2–20 μm size fraction, increasing with depth. The distribution of PAHs was primarily determined by the sorption on soil organic matter and the characteristics of PAHs. This research should have significant contribution to PAH migration study and remediation design for PAHs-contaminated sites.     

Three-dimensional barricading of a predatory trap reduces predation and enhances prey capture

Animal structures come at material, energetic, time, and expression costs. Some orb-web spiders add three-dimensional barrier structures to their webs, but many do not. Predator protection is considered to be the principal benefit of adding these structures. Accordingly, it remains paradoxical why some orb-web spiders might construct the barriers while others do not. Here, we experimentally determined whether the barrier structure added to the horizontal orb web of the spider Cyrtophora moluccensis deters predators at the cost of reducing the amount of prey captured in the field. We conducted experiments by day and night to assess whether the effects vary with the time of day. We found that the three-dimensional barriers not only offered protection from predatory wasps by day but also enhanced the amount of prey captured by day and night. Moreover, the barrier structure appears particularly useful at catching moths, the largest and most energetically profitable prey that it encounters. We, therefore, concluded that reducing the energetic and time costs associated with producing and depositing extra silk threads is the principal reason why barrier structures are used intermittently among orb-web spiders.     

兼氧型MBR工艺对污泥自消化效果的研究

研究了兼氧型MBR工艺中,当溶解氧控制在0.1～3.0 mg/L时,兼性厌氧菌和厌氧菌所占比例达80%。实验进水COD浓度为60～600 mg/L,COD去除率平均达93%;MLVSS浓度一直保持稳定,平均值为11 090 mg/L,而无机灰分浓度逐渐积累,实验开始时为3 107 mg/L,实验结束时达5 830 mg/L。结果表明,兼氧型MBR工艺可实现污泥自消化,不排放有机性污泥。兼氧型MBR工艺还对膜组件有一定自清洁作用,运行周期可达4个月。实验证明,兼氧型MBR工艺具有处理效率高、不排放有机污泥以及减轻膜污染的特点,是一种创新性的污水处理技术。     

Predation affects the susceptibility of hard clam Meretrix lusoria to Hg-stressed birnavirus

Predator–prey interaction in aquatic ecosystem is one of the simplest drivers affecting the species population dynamics. Predation controls are recognized as important aspects of ecosystem husbandry and management. In this paper we investigated how predation control cause an increase in host growth in the abundance of hard clam (Meretrix lusoria) populations subject to mercury (Hg)-stressed birnavirus. Here we linked predator–prey relationships with a bioenergetic matrix population model (MPM) associated with a susceptible–infectious–mortality (SIM) model based on a host–pathogen–predator framework to quantify the predator effects on population dynamics of disease in hard clam populations. Our results indicated that relative high predation rates could promote the hard clam abundances in relation to predators that selectively captured the infected hard clam, by which the disease transmission was suppressed. The results also demonstrated that predator-induced modifications in host behavior could have potential negative or positive effects on host growth depending on relative species density and resource dynamics. The most immediate implication of this study for the management of aquatic ecosystem is that, beyond the potential for causing a growth in abundance, predation might provoke greater predictability in aquatic ecosystem species populations and thereby increase the safety of ecosystem production from stochastic environmental events.     

海南芒果园土壤环境及其对芒果品质的影响

针对海南芒果(Mangifera indica)生产的环境条件进行了研究,分别在芒果园采集了植株和土壤样品,采用国家标准测定方法对比分析了各种元素的含量和分布特征,并阐明了芒果对环境条件的生态适应性.研究结果表明:海南芒果园土壤有机质、全氮、有效磷含量较低(为四级以下水平),有效钾含量相对较高.Ca、Mg、B、Ni含量较低,Cu、Mn含量较高.海南芒果种植地环境质量较好,Cr、Pb、Cd等低于国家土壤环境质量一级标准.Hg、Cu、As、Pb含量为一至二级标准.六六六、滴滴涕含量低于一级标准.海南芒果矿质元素含量丰富,农药残留量和Cr、As、Cd含量符合无公害芒果的要求.芒果对大中量元素、微量元素和有害元素(Hg、As、Cd)的生物吸收系数较大.锰主要在叶片中积累,铜则主要积累在果实中.     

硅酸盐、腐殖酸对Cr污染土壤中小白菜生理及吸铬量的影响

针对在铬污染区土壤中的叶菜类吸铬量是果菜类2~3倍,以及硅酸盐或腐植酸在重金属污染土壤上的最佳施用量研究较少的问题,为保障蔬菜的品质安全,文章通过土壤盆栽试验,研究硅酸盐、腐殖酸不同用量对Cr污染土壤中小白菜(Brassica Chinensis)生理指标和吸铬量的影响.结果表明,施低质量分数的硅酸盐(1.0 g·kg-1)效果最佳,既能提高受Cr污染小白菜的生物量、叶绿素相对含量,又能减轻Cr毒害对抗氧化酶系统中SOD酶活性的抑制,缓解小白菜受到的过氧化胁迫,有效降低小白菜吸铬量;高质量分数硅酸盐(2.0 g·kg-1)对生长产生抑制.腐殖酸在设计的3个质量分数水平上均不能有效降低小白菜吸铬量,对生长的促进作用也不明显.     

曝气复氧对滇池重污染支流底泥污染物迁移转化的影响

利用模拟试验方法,研究和探讨了河道曝气复氧对滇池重污染支流底泥污染物迁移转化的影响,结果表明:(1)曝气复氧会导致上覆水体pH值上升0.6～1.0;(2)曝气复氧对上覆水体中TN、TP的质量浓度影响相似,在好氧处理条件下呈下降趋势,而在不曝气的对照处理中呈持续上升趋势,两种状况上覆水体TN、TP的平均变化速率分别为:-0.156 mg·L-1·d-1、-0.060mg·L-1·d-1和0.414mg·L-1·d-1、0.036mg·L-1·d-1;(3)上覆水体中COD的质量浓度在好氧和对照两种处珲条件下,表现出两种不同的变化趋势,前者先上升后下降,而后者先下降后上升,平均变化速率分别为-0.361 mg·L-1·d-1和0.314 mg·L-1·d-1;(4)曝气复氧可抑制河道底泥向上覆水释放污染物质,适合于重污染河道水体修复.     

Maternal serum levels of total activin-A in first-trimester trisomy 21 pregnancies

Maternal serum total activin-A concentration was measured in 45 pregnancies affected by trisomy 21 and 493 control unaffected pregnancies at 10–14 weeks of gestation. In the trisomy 21 pregnancies total activin-A concentration was significantly higher (1.36 MoM of the unaffected pregnancies) and in 16% of cases the level was above the 95th centile of normal. The log₁₀ SD for the control group and the trisomy 21 group were 0.17 and 0.22, respectively. The median pregnancy associated plasma protein-A (PAPP-A) in this trisomy 21 series was 0.49 and for free β-hCG was 2.05. In the trisomy group there were significant positive associations between total activin-A and PAPP-A (0.6071) and free β-hCG (0.4255). The low median difference and the high overlap in values between trisomic and unaffected pregnancies make total activin-A of little practical use in first-trimester screening for trisomy 21. Copyright © 2001 John Wiley & Sons, Ltd.     

Adsorption of phenol on inorganic-organic pillared montmorillonite in polluted water

Both inorganic- and organic-pillared montmorillonites (PMts) were used to adsorb phenol to study suitable conditions for adsorption and adsorption isotherms. The adsorbing capacity of modified clays depends not only surface area, but mainly on micropore structure and surface components. After incandescing at 500 degrees C, the pillar structure and the basal interlayer spacing (1.83 nm) remained stable. Using modified PMt with surfactant can improve adsorbing capacity greatly. The PMt can be recycled, and it is a potential substance for adsorption of environmental pollutants.