水溶性有机物对土壤中菲的生态毒性影响

采用生物培养和物理化学试验,研究了水溶性有机物(DOM)对土壤中phe生态毒性的影响.结果表明,本研究所用DOM均具有表面活性;小麦根phe毒害的敏感区间为0～200mg/kg,200mg/kg是土壤中phe的50%小麦根伸长抑制率浓度.DOM的存在会降低phe的生态毒性,但是降低程度与其疏水性馏分含量和表面活性有关,且phe生态毒性的降低程度随DOM浓度的增大而增大.本研究的结果说明DOM能减轻土壤中phe的生态毒性.     

Cd对野茼蒿种子发芽的影响

为了研究重金属Cd在野茼蒿生长初期所产生的毒性效应,本文以野茼蒿种子为实验材料,分别设定了低浓度组(0、0.2、0.5、0.8、1.0和5.0 mg·L-1)和高浓度组(0、10、25、50和100 mg·L-1)2组实验,对在Cd胁迫作用下野茼蒿种子的萌发生长进行了研究.结果表明:在低浓度(＜5 mg·L-1)下,C...     

氯丹和灭蚁灵污染场地土壤对陆生生物的毒性效应

为向污染土壤的监测、生态毒理诊断及修复提供方法和数据,以氯丹、灭蚁灵污染场地土壤为供试土壤,测定了氯丹、灭蚁灵复合污染对蚯蚓的急性毒性效应以及对小麦、小白菜、玉米和水稻4种植物种子发芽率和根伸长抑制率的影响.结果表明,蚯蚓对本场地污染响应十分敏感,处理d 3高浓度组开始出现死亡,此后死亡率随污染物浓度增大而上升,d 14部分高浓度组死亡率达到100%;同一浓度下,氯丹和灭蚁灵对4种植物种子根伸长抑制率均显著大于对种子发芽的抑制率,植物的根生长比种子发芽对有机污染物的毒性更为敏感.4种植物种子对污染场地土壤的敏感性为小麦>小白菜>水稻>玉米.氯丹和灭蚁灵对蚯蚓的毒性要大于对这几种植物的毒性,蚯蚓对氯丹和灭蚁灵的响应更加敏感.因此,蚯蚓作为指示生物,其急性毒性试验可作为氯丹和灭蚁灵污染场地的诊断指标,诊断周期以14 d为宜.     

1,4-二氯苯对小白菜种子萌发和幼苗的毒性

采用室内模拟染毒法,研究1,4-DCB(1,4-二氯苯)对3种小白菜种子(矮青6号、上海青和秦白2号)萌发和蔬菜幼苗的毒性作用. 结果表明:1,4-DCB作用后,3种小白菜种子的发芽势、种子发芽率、发芽指数和活力指数均降低,并呈现一定的剂量-效应关系;种子受1,4-DCB胁迫后,小白菜幼苗的根和苗生长都受到了抑制,根长和苗高降低,根苗比显著下降;随着ρ(1,4-DCB)的升高,受胁迫后的幼苗叶片的w(游离脯氨酸)呈现先升高后降低的趋势,而MDA(丙二醛)含量逐渐升高,与ρ(1,4-DCB)呈正相关;幼苗叶片SOD(超氧化物歧化酶)活性在ρ(1,4-DCB)为5 mg/L时升高,在ρ(1,4-DCB)为10和50 mg/L时明显降低;与对照组相比,各处理组幼苗叶片POD(过氧化物酶)活性均升高,但是ρ(1,4-DCB)为50mg/L时酶活性比ρ(1,4-DCB)为10 mg/L时下降. 表明水体中1,4-DCB污染对蔬菜种子萌发和幼苗生长产生毒性,其毒性机制与膜脂质过氧化有关.      

The representation of cyanobacteria life cycle processes in aquatic ecosystem models

Two simplified versions of a numerical life cycle model for diazotrophic cyanobacteria (of the order Nostocales) are developed and evaluated. Both consider two-life cycle stages, one growing, nitrogen-fixing stage and one stage that combines the resting, germinating and vegetative stages. The versions differ in the vertical resolution of the non-diazotrophic stage: version 1 collects the biomass in one layer at the bottom, version 2 considers sinking and rising of biomass explicitly. The results of the two versions are compared with a complex cyanobacteria life cycle model which describes four different life cycle stages each with two internal quotas for energy and nitrogen. The two simplified approaches show a good agreement with respect to the main characteristics of cyanobacteria dynamics (timing and duration of blooms, magnitude of nitrogen fixation, interannual variability). Our model study shows that both simplified approaches are suitable to be implemented into three-dimensional coastal or lake models.     

苗期棉花对向日葵列当种子萌发诱导作用初探

以5个推广棉花（Gossypium hirsutum L.）品种（中棉所63、中棉所57、中棉所47、中棉所44和中棉所41）为研究对象,利用盆栽试验分别采集棉花苗期3个时期（二叶一心、四叶一心和六叶一心期）的根际土和植株样品,并用其甲醇浸提测试对向日葵列当（Orobanche cumana Wallr.）种子的发芽率。结果表明,根际土、植株样（根、茎和叶）甲醇浸提液诱导种子发芽率高低顺序为根际土〉根〉茎〉叶,表明棉花的根际土和根的甲醇提取液对向日葵列当种子的萌发诱导作用较强。3个时期中,二叶一心期诱导向日葵列当的发芽在品种之间不存在显著性差异,表现为较稳定的诱导种子萌发作用。综合得出,棉花二叶一心期的根际土和根的甲醇提取液对向日葵列当种子萌发的诱导作用较强,二叶一心期为棉花作为＂诱捕作物＂生物防除寄生杂草提供科学依据。     

大亚湾沉积物中浮游植物休眠体萌发研究

为了解孢囊在浮游植物种群动态及赤潮发生中的作用,于2005年4月~2006年6月采集大亚湾养殖海域沉积物样品,经孔径为125,20μm的网筛过滤,在25℃下进行萌发,观察培养20,40d的浮游植物休眠体的萌发状况.结果表明,共萌发出浮游植物27属37种.裸甲藻(Gymnodinium corii Schiller)为优势甲藻类,其占甲藻细胞数量平均百分比为73.1%,最高百分比可达99.7%.定鞭藻中的金色藻(Chrysochromulima spp.)和蓝藻中的拟鱼腥藻(Anabaenopsis spp.)也萌发出较高数量.不同时间培养、萌发的浮游植物种类组成有所差异,同时也随沉积物捕捉时间的不同而出现一定的季节差异.休眠体的萌发可在一定程度上反映水体浮游植物组成,但在萌发中大量出现的一些微型和微微型浮游植物可能会由于体型过小而在浮游植物监测中被忽略.     

模拟氮沉降对大豆萌发和幼苗生长的影响

氮沉降是当今倍受关注的全球性环境问题.采用大田试验和室内培养的方法,研究大豆种子萌发和幼苗生长对氮沉降的响应.实验设4组处理(CK、T1、T2、T3),所施氮肥为NH4NO3,在室内培养实验中,4组处理的浓度分别为0、0.08、0.16、0.24mol/L.大田实验中,4组处理的氮施入量分别为0,50,100,150 kg·hm-2·a-1.结果表明:过量氮沉降对种子萌发有一定的抑制作用,降低了种子的发芽速度和发芽率;抑制了幼苗的生长速度,降低了植株的株高、叶面积和生物量,并减小了根冠比;随着氮施入量的增加幼苗的蒸腾速率逐渐降低,但叶片叶绿素含量逐渐增加.     

Spore inhibition-based enzyme substrate assay for monitoring of aflatoxin M1 in milk

A spore germination-based concept and its transformation into a field level prototype for monitoring aflatoxin M₁ (AFM₁) in milk was developed. Initially, 15 strains of Bacillus spp. procured from different culture collection were screened for AFM₁ sensitivity using spot assay and marker strain showing inhibition at 0.5 ppb was selected based upon maximum zone of inhibition. The selected strain B. megaterium 2949 was further screened for different enzymes activities and subsequently its spores were produced to an extent of 73.13% ± 3.197% in newly developed sporulation medium containing beef extract (0.0075% ± 0.0004%), yeast extract (0.015% ± 0.001%), peptone (0.0375% ± 0.0016%), and sodium chloride (0.0375% ± 0.0018%). A spore germination-based concept/ assay was optimized by immobilizing spores in eppendorf with pretreated milk (80°C/15 min) containing germinant and chromogenic substrate followed by incubation at 37°C. The appearance of sky blue color within real time of 45 min indicated spores germination and release of specific marker enzyme such as acetyl esterase and its specific action on chromogenic substrate which demonstrates absence of AFM₁ in milk. However, if there was no color change, presence of AFM₁ at 0.5 ppb MRL was denoted by Codex. The developed concept on AFM₁ detection was validated and a correlation of 0.97 was established with AOAC approved Charm 6602 and ELISA at Codex MRL with minimal false positive and negative results. The cost effective test has potential application in dairy farms, manufacturing, and R&D units for routine monitoring of AFM₁ in milk.     

Biodegradation and phytotoxicity assessment of phenanthrene by biosurfactant-producing Bacillus pumilus 1529 bacteria

ABSTRACT

Phenanthrene is a toxic and mutagenic pollutant that can cause severe environmental and human health issues. The bioremediation of these polyaromatic hydrocarbons (PAHs) is possible with a biosurfactant by enhancing hydrophobicity. In this study, the production of a biosurfactant by Bacillus pumilus 1529 and its effects on the phenanthrene biodegradation pathway were examined. Biosurfactant production was determined using hemolytic activity, emulsification index, and surface tension. For phenanthrene metabolite detection, samples at 0, 7, 14, and 21 incubation days were analysed by gas chromatography-mass (GC-mass) spectrometry. The results showed that Bacillus pumilus 1529 can reduce surface tension to 22.83?±?1.1?mN?m^?1. Furthermore, the GC-mass spectrometry analysis showed that 1-hydroxy-2-naphthoic acid, benzaldehyde, o-phthalic acid, and phenylacetic acid were notable phenanthrene metabolites produced during phenanthrene biodegradation. Biodegraded phenanthrene and its metabolites have a less toxic effect on the germination of safflower seeds than non-biodegraded phenanthrene. The IC50 of phenanthrene on seed germination after biodegradation was increased to approximately 113?mg?L^?1. In general, biodegradation aided by biosurfactant producing bacteria contributed to turning the toxic phenanthrene into less harmful metabolites with lower phytotoxicity effects, indicating that its application in the bioremediation of PAHs is promising.