生物有机肥对香蕉枯萎病及根系分泌物的影响

生物有机肥通过调节微生物群落多样性来改善土壤生态环境,而根际微生物生态环境变化取决于根系分泌物的种类和数量.研究通过盆栽试验和离位溶液培养法研究了生物有机肥对香蕉枯萎病及香蕉根系分泌物的影响.结果表明,生物有机肥对香蕉枯萎病的防病效果高于有机肥和不施肥处理,生物有机肥和有机肥防病效果分别达到55.4%和28.5%;香蕉根系分泌物中低分子量有机酸包括草酸、苹果酸和反丁烯二酸,以草酸为主,ρ(草酸)占ρ(有机酸总量)的百分比为83.6%~93.0%;生物有机肥比有机肥更显著降低香蕉根系分泌物中ρ(苹果酸)、ρ(反丁烯二酸)和ρ(有机酸总量),不同处理处理根系分泌物的ρ(有机酸)依次为:有机肥>生物有机肥>不施肥;生物有机肥处理的氨基酸种类和质量浓度最大,有机肥次之,生物有机肥处理中根系分泌物的ρ(γ-氨基丁酸)、ρ(β-丙氨酸)、ρ(a-氨基丁酸)、ρ(谷氨酸)、ρ(天冬氨酸)和ρ(磷酸丝氨酸)均显著高于有机肥和不施肥处理;生物有机肥处理的主要氨基酸[各氨基酸质量浓度占ρ(氨基酸总量)的百分比大于5%]有磷酸丝氨酸、苏氨酸、γ-氨基丁酸、乙醇氨和肌肽,其中ρ(磷酸丝氨酸)和ρ(γ-氨基丁酸)显著高于不施肥和有机肥处理;香蕉枯萎病病情指数与ρ(磷酸丝氨酸)、ρ(丝氨酸)、ρ(异亮氨酸)呈显著负相关,相关系数分别为-0.99、-0.98和-0.95,与ρ(鹅肌肽)呈极显著正相关,相关系数为1.00.生物有机肥降低了根系分泌物中有机酸的质量浓度,增加了氨基酸的种类和质量浓度,且香蕉枯萎病病情指数与根系分泌物中一些氨基酸质量浓度存在显著相关性,这可能是生物有机肥在香蕉枯萎病防治中起作用的原因之一.     

两种生态型东南景天根系分泌物的差异性

东南景天(Sedum alfredii Hance)具有很强的耐高Zn 胁迫、吸收和运输Zn的能力,但其根系如何通过分泌作用实现对Zn胁迫的适应和对土壤难溶性Zn的活化作用,还缺乏机理方面的解释.因此,本研究运用离子色谱、氨基酸自动分析等技术较系统地研究了两种生态型东南景天根系分泌物组成的差异性及其对土壤中不同化合物Zn的活化效应,旨在探明根系分泌物与东南景天超积累Zn的关系.结果表明,两种东南景天的根系分泌物均能够活化土壤中难溶态的ZnO、ZnCO3和Zn3(PO4)2,而对ZnS没有明显地活化作用.通过对根系分泌物组成成分分析,两种生态型东南景天根系分泌物中可溶性糖占绝对优势,有机酸和氨基酸含量很低,且均以非超积累生态型>超积累生态型.超积累生态型东南景天根系分泌物中的可溶性总糖、有机酸(苹果酸除外)、氨基酸等各成分含量均以Zn 1.0 μmol·L-1处理>Zn 500 μmol·L-1处理,非超积累生态型东南景天根系分泌物中糖和有机酸含量也随着Zn浓度的增加而减少,而绝大多数氨基酸含量则随着Zn浓度的增加而增加.这说明本试验条件下测定的根系分泌物组分在东南景天超积累Zn过程中并不起主导作用.     

Diuron herbicide degradation catalyzed by low molecular weight humic acid-like compounds

Phenylureas such as diuron are major herbicides used worldwide to control undesirable weeds. The environmental fate of phenylureas is of great interest because massive amounts of those herbicides are used. It is known that abiotic degradation of phenylureas in soil–water systems is catalyzed by humic acids. However, due to the chemical heterogeneity and large molecular sizes of humic acids, the specific effects of functional groups during catalysis have not been elucidated. Therefore, we studied here for the first time the kinetics of diuron degradation in the presence of low molecular weight humic acid-like compounds such as benzoic acid derivatives. Experiments were carried out at various pH and temperature, and monitored by high-performance liquid chromatography. Results show that all benzoic acid derivatives efficiently catalyzed diuron hydrolysis. The catalytic efficiency decreased in the following order: 0.88 M^?1 day^?1 for 3,4-dihydroxybenzoic acid, 0.72 M^?1 day^?1 for 4-hydroxybenzoic acid, 0.23 M^?1 day^?1 for phthalic acid, 0.11 M^?1 day^?1 for 2-hydroxybenzoic acid, and 0.09 M^?1 day^?1 for 2,4-dihydroxybenzoic acid. These differences in the catalytic efficiency are explained by steric hindrance affecting the accessibility of reactive sites and hence influencing the rate of the overall process. Steric factors are therefore expected to control the catalytic activity of humic acids because of the chemical similarities between humic acids and low molecular weight humic acid-like compound. Our results should help predict more accurately the fate and abiotic degradation mechanism of phenylureas in the environment.     

Effect of low molecular weight organic acids on adsorption and desorption of fluoride on variable charge soils

The effect of four low molecular weight organic acids on F⁻ adsorption by two variable charge soils was investigated using a batch method. The organic acids reduced F⁻ adsorption through competition by the acids with F⁻ for sorption sites. Oxalic and malonic acids, both of which have simpler chemical structures, were more effective than citric or malic acid. The effect of organic acids on F⁻ adsorption was more prominent at higher pH values and with larger amounts of the organic acids. The desorption study showed that the organic acids enhanced the desorption of F⁻ adsorbed by the soils. In the control and malic acid systems, desorption increased sharply with decreasing pH, while in the oxalic acid system, desorption rose slightly with decreasing pH. Desorption also increased with increasing amount of organic acid added. There are two possible mechanisms for the effect of the organic acids on F⁻ adsorption and desorption: (1)␣competition of the organic acids with F⁻ for adsorption sites and (2) dissolution of the adsorbents, especially dissolution of soil Al.     

Effect of co-existing organic compounds on adsorption of perfluorinated compounds onto carbon nanotubes

Co-existing organic compounds may affect the adsorption of perfluorinated compounds (PFCs) and carbon nanotubes in aquatic environments. Adsorption of perfluorooctane sulfonate (PFOS), perfluorooctane acid (PFOA), perfluorobutane sulfonate (PFBS), and perfluorohexane sulfonate (PFH_xS) on the pristine multi-walled carbon nanotubes (MWCNTs-Pri), carboxyl functionalized MWCNTs (MWCTNs-COOH), and hydroxyl functionalized MWCNTs (MWCNTs-OH) in the presence of humic acid, 1-naphthol, phenol, and benzoic acid was studied. Adsorption kinetics of PFOS was described well by the pseudo-second-order model and the sorption equilibrium was almost reached within 24 h. The effect of co-existing organic compounds on PFOS adsorption followed the decreasing order of humic acid>1-naphthol>benzoic acid>phenol. Adsorbed amounts of PFOS decreased significantly in the presence of co-existing or preloaded humic acid, and both adsorption energy and effective adsorption sites on the three MWCNTs decreased, resulting in the decrease of PFOS adsorption. With increasing pH, PFOS removal by three MWCNTs decreased in the presence of humic acid and phenol. The adsorbed amounts of different PFCs on the MWCNTs increased in the order of PFBSxS相似文献   

Some biologically important low molecular weight organic acids in the sediments of Loch Eil

The isolation of biologically important low molecular weight organic acids from organically enriched sediments in Loch Eil, Scotland, was carried out by extraction of pore water with acidified ethyl acetate. High concentrations of acetic acid, up to 1.8 mg g^-1 dry weight of sediment were found at Station E-24. Propionate, butyrate, valerate, lactate and traces of succinate were also found. Succinate was present in significant amounts, 42.2 g g^-1 dry weight of sediment at Station E-70, which received a higher input of organic matter than E-24. Both propionate and succinate were absent from a control station in the Lynn of Lorne where the sediment was low in carbon compared with Loch Eil. In experimental tanks, acetate levels increased as the input of organic carbon (as cellulose) was increased up to a load level of 1.5 g m^-2 day^-1. Above this, acetate decreased and succinate appeared. Succinate was not detected in low-loaded tanks. Experiments with sieved mud showed a vertical distribution of the different acids with depth. Lactate and succinate reached highest concentration in the 0 to 3 cm layer, acetate at 3 to 6 cm and propionate at 6 to 9 cm. The results are discussed in relation to the role of these acids as food sources and as indicators of biochemical pathways taking place in sediments with different carbon input levels.     

Variations between rice cultivars in root secretion of organic acids and the relationship with plant cadmium uptake

To attempt to understand certain mechanisms causing the variations between rice cultivars with regard to Cd uptake and accumulation, pot soil experiments were conducted with two rice cultivars at different levels of Cd, i.e., 0 (the control), 10, 50 mg Cd kg⁻¹ soil. The two rice cultivars differ significantly with regard to Cd uptake and accumulation. Root secretions of low-molecular-weight organic acids (LMWOA) for each treatment were measured with ion chromatography. The results showed that LMWOA concentrations in the soil planted with Shan you 63 (a high soil Cd accumulator) were all higher than those in the soil planted with Wu yun jing 7 (low soil Cd accumulator) at different soil Cd levels, although the magnitudes of the differences varied for individual LMWOA and depend on soil Cd concentrations. For all six LMWOA, there were significant differences at P < 0.05 or < 0.01 levels for soils treated with 10 and 50 mg kg⁻¹ Cd. The magnitude of the differences was greater under soil Cd treatments, especially at relatively low levels (for example, 10 mg Cd kg⁻¹ soil), than in the control. Acetic acid and formic acid constituted more than 96% of the total concentration of the six LMWOA, while citric acid constituted only about 0.1%. The rice cultivar with higher concentrations of LMWOA in soil accumulated more Cd in the plants. The results indicate that LMWOA secretion by rice root, especially in Cd-contaminated soils, is likely to be one of the mechanisms determining the plant Cd uptake properties of rice cultivars.     

表面活性剂及水溶性有机物对菲生态毒性的影响

采用室内培养试验及化学试验研究了表面活性剂及水溶性有机物(DOM)对土壤中菲对小麦的生态毒性的影响.结果表明,绿肥和猪粪堆肥DOM具有具有类似表面活性剂的表面活性性质,且猪粪堆肥的表面活性较大;在本试验条件下,DOM对菲对小麦的生态毒性有减轻作用,而表面活性剂对菲生态毒性有增加的趋势;当DOM和表面活性剂共存时,菲的生态毒性则比DOM单独作用时的结果强,而弱于表面活性剂单独作用的结果.     

添加小分子有机物对污泥重金属生物沥滤的抑制作用

采用向城市污泥添加小分子有机物后进行生物沥滤,探讨了不同小分子有机物(甲酸、乙酸、丙酸、丁酸、乙醇、水杨酸、草酸、苯甲酸)对生物沥滤过程污泥中pH值、Eh、Cu含量和Zn含量的影响。结果表明,对于污泥中的pH和Eh,不同有机物对其影响程度在整个沥滤过程中大体上相似,即pH值都呈先升后降的趋势,Eh呈先降后升趋势。对不同类型的重金属来说,不同有机物对其影响程度Cu大于Zn,其中Cu的沥出效果从强到弱依次为:对照>苯甲酸>乙醇>草酸>水杨酸>丙酸>甲酸>丁酸>乙酸,而对Zn的沥出效果在整个沥滤过程中相似。总之,整体规律为:醇类化合物和二羧基酸对污泥中的硫细菌的生物沥滤影响不大,而对于结构相似的单羧基有机酸来说,碳链越短,对生物沥滤的影响越大,分子量较高的芳香族有机酸对于重金属的去除也有明显的抑制作用,影响程度随着羧基数目的增加而加剧,但其抑制作用不及小分子有机酸显著。此外,污泥中营养物质TN、TP和TK的释放也受到一定影响。     

不同纳米材料作用下菲对鲫鱼的毒性效应

研究了纳米材料(多壁碳纳米管和纳米氧化锌)泄漏进入水环境后吸附多环芳烃(菲)对水生生态系统可能造成的影响及其影响机制,以便能及早采取相应的风险管理措施.实验结果表明,多壁碳纳米管(MWCNTs)显著降低了菲(Phe)在鲫鱼肌肉和肝脏中的富集,但增加了其在鱼脑中的富集量;C-Phe组菲在眼部、胚胎和生殖腺中含量均高于ZnO-Phe组.MWCNTs、nZnO与菲均诱导鲫鱼脑部和肝脏组织中自由基的生成.     

大气中全氟与多氟有机化合物研究进展

全氟与多氟有机化合物(PFCs)作为表面活性剂被广泛应用于工业生产及生活家居领域,部分PFCs已被列为斯德哥尔摩公约受控持久性有机污染物(POPs).PFCs具有一些特殊的理化性质(如高表面活性、憎水憎油性等),使其采样、分析、环境迁移转化过程等都不同于"传统"POPs(如PCBs、PAHs等).相对于其它环境介质(水、沉积物和生物等)研究,大气中PFCs的研究相对较少.本文针对大气中PFCs的研究现状进行综述,内容涵盖了大气PFCs的样品采集、前处理、仪器分析、含量水平和迁移转化过程,其中重点概述了大气中PFCs的气-颗粒两相分配、长距离迁移、干湿沉降和大气降解,并提出了今后的重点研究方向建议.     

Transformation of some dissolved organic compounds by a natural heterotrophic population

Uptake of radioactively labeled glycolic acid, arginine, glutamic acid, and glycine by natural marine bacterial population was rapid and approached a maximum value which was over 90% of the total substrate. Uptake of glucose was rapid, but had a maximum uptake of less than 80%. All substrates except glycolic acid were assimilated to a similar degree (a maximum of more than 30% of the total given substrate). Glycolic acid had a maximum assimilation of less than 10%. The presence of glycolic acid resulted in no extracellular metabolites detectable on a gel permeation column. Between 5 and 10% of the other substrates were transformed and excreted within 72 h by the bacteria. These exudates were both nominally larger and smaller than the given substrates.NORDA publication number: JA 330:008:80