Volatile organic compounds of some Trichoderma spp. increase growth and induce salt tolerance in Arabidopsis thaliana

Many beneficial effects of Trichoderma spp. on plant growth and/or resistance to biotic/abiotic stresses can result from the production of bioactive compounds including volatile organic compounds (VOCs). We evaluated the effects of the volatile mixtures from 13 strains of different Trichoderma species on induction of tolerance to salt stress (100 mM NaCl) as well as growth promotion of Arabidopsis thaliana. Plants responded differently due to the presence of VOCs from various Trichoderma species ranging from both growth promotion and induction of salt tolerance to no significant changes under any of the conditions tested. In plants exposed for 2 weeks to VOCs of the selected strain, i.e. Trichoderma koningii, there was less H₂O₂ accumulation under salt stress compared to that in control plants. This result may reflect the possible role of VOCs of this strain in plant protection against oxidative damage under salt stress. Together, induction of salt tolerance using VOCs should be added to the known mechanisms of plant vigor enhancement by Trichoderma spp.     

A Model to Derive Soil Criteria for Benzene Migrating from Soil to Dwelling Interior in Homes with Crawl Spaces

The establishment of Australian soil criteria for volatile hydrocarbons such as benzene has been limited due to the lack of a suitable transport model to predict human exposures. In a confined environment representing worst case exposure, the inhalation of volatile hydrocarbons from sub-surface regions may be used to establish health-based soil criteria. A volatilisation model is presented for the case of a crawl space home which is a common housing design in Australia. The model is used to estimate a cumulative indoor human dose (CIHD) based on one-dimensional movement from a finite subsurface source through soil to the dwelling interior. A non-homogeneous surface boundary condition is represented where the volatile is not immediately swept away from the air/soil boundary. Time-dependent differential equations established to represent transport are solved using Laplace transforms. Australian experimental field data are used in considering mixing, dilution, ventilation and sink effects and first-order soil and air degradation of the volatile incorporated. A CIHD from the model is compared to various benzene exposure standards to determine a criterion for benzene in soil. Sensitivity analysis has revealed that the dominant influencing parameters are those relating to dwelling characteristics and not soil properties or the physico-chemical properties of the volatile. Each of the group-input parameters has been found to act virtually independently in the model presenting the potential for model refinement and establishment of a generic soil criterion for benzene.     

Volatile compounds released by microalgae-water phase from Taihu Lake in China

The spectrum of Volatile Organic Compounds (VOCs) released by the microalgae-water phase of Taihu Lake in China was examined, then release behaviors were studied using non-methane hydrocarbons (NMHC, including a few polar organics) to describe the total amount of the released VOCs. Coupled dynamic headspace sampling with on-line monitoring of methane and NMHC was used to reflect the quasi-realtime release behavior of methane and NMHC by the microalgae-water phase. Alkanes, alkenes, oxygenated VOCs (OVOCs) and volatile sulfide chemicals (VOSCs) were detected. Their relative contents over time varied markedly from the stationary to the apoptosis phase, with their release rates as described by NMHC estimated from 0.02 to 0.59 μgC/(h g). Methane was investigated simultaneously, and its release rate was found to be 0.05–3.96 μgC/(h g). The release rates of both NMHC and methane were found to relate to the culture phase of the microalgae.     

Source analysis and health risk-assessment of ambient volatile organic compounds in automobile manufacturing processes

Abstract

The sources and process-specific emission of volatile organic compounds (VOCs) from an automobile manufacturing plant in Beijing, China were explored and monitored to assess the health risk from VOCs to workers of the automobile manufacturing plant. Eleven VOCs were detected in the air samples collected from the 12 working posts of five workshops of the automobile manufacturing plant using a meteorological chromatographic analytical method. The health risks exposed to VOCs were assessed using the probabilistic risk-assessment method, and the sensitivity and uncertainty analysis were conducted using the Monte Carlo simulation method. The results showed that VOCs mainly originated from the use and volatilization of chemical raw materials. The total carcinogenic risks were large owing to the high concentrations of benzene and ethylbenzene in various processes, suggesting a definite risk. The total non-carcinogenic risk in the paint shop was the highest, and the topcoat post, mixing paint post and basecoat post contributed to more than 70% of the total risk of this workshop. Exposure duration and concentration of VOCs had a greater impact on the health risk. These research findings may provide scientific basis for policy toward improving the health status of workers in automobile manufacturing enterprise in China.     

The role of field-collected cues in the host recognition of twig girdlers (Oncideres rhodosticta) on honey mesquite (Prosopis glandulosa)

Conspecific gravid females integrate volatile organic compounds (VOCs) to exploit potential oviposition sites; the role of VOCs has not been examined on twig girdlers, Oncideres rhodosticta, and honey mesquite, Prosopis glandulosa. To examine the host selection behavior of female twig girdlers, we examined the preference and searching time between healthy and girdled twigs of honey mesquites in New Mexico, USA. Among 21 different volatile organic compounds, female twig girdlers reacted to six chemical compounds from girdled twigs and four from healthy twigs. While females responded to Heptanal, (E)-2-Heptenal, and Linalool oxide on both healthy and girdled twigs, they also reacted to one healthy specific compound and two girdled specific compounds. Female twig girdlers distinguished healthy twigs over girdled twigs with faster searching time. Our finding demonstrates VOCs in the genus Oncideres for the first time, providing additional empirical information to help decide on the biological control potential of possible agents during the pre-release risk assessment.     

Distribution and Volatilization of Organic Compounds Following Uptake by Hybrid Poplar Trees

Hybrid poplar trees were exposed to eleven organic compounds in hydroponic systems. The eleven contaminants were common pollutants with a wide range of physio-chemical properties such as the octanol-water partition coefficient, Henry's constant, vapor pressure, and molecular weight. Contaminants, ¹⁴C-labeled, were introduced into the root zone, and contaminant transport and fate were examined. Aqueous concentrations were monitored throughout each experiment as was vapor phase concentrations in the air stream passing over the leaves. At experiment conclusion, plant tissues were oxidized to determine ¹⁴C concentrations. The uptake, distribution, and volatilization of these contaminants varied greatly among the 11 contaminants in the study. Uptake and translocation of the contaminants ranged from < 0.3% (of the applied ¹⁴C-labeled compound) for 1,2,4-trichlorobenzene to 20% for benzene. Volatile compounds were volatilized from the leaves. Volatilization in the transpiration stream was related to the vapor pressure of the compound. The fate and transport mechanisms investigated in this study provide valuable insight into the potential fate of contaminants in full-scale phytoremediation.     

Effects of aphid herbivory on volatile organic compounds of Artemisia annua and Chrysanthemum morifolium

We showed the effect of aphid infesting on the volatile organic compounds (VOCs) emitted by the infested Artemisia annua and Chrysanthemum morifolium cultivar ‘Nan nong hong feng’ plants by using headspace solid-phase microextraction (HS-SPME) method combined with gas chromatography mass spectrometry (GC–MS). In olfactometer bioassay experiment, aphids showed a preference for the odour of both healthy and infested chrysanthemum, while we found an opposite result in A. annua. Aphids tend to healthy plants compared with the infested, and the phenomenon became obvious with time. Different extracts were tested with the healthy plants and aphid infested plants. Eucalyptol, β-caryophyllene, (E)-β-farnesene, and germacrene D were released as the major constituents in both species. After aphid infesting, we observed a great increase in artemisia ketone and (E)-β-farnesene and a decrease in germacrene D in A. annua; comparatively, eucalyptol, isoborneol and β-caryophyllene increased in chrysanthemum. Combined with the GC–MS data and olfactometer bioassay results we concluded that (E)-β-farnesene and artemisia ketone emitted from A. annua might act as a potential volatile compound to resist aphids, and the two compounds would be useful for future ecological control of aphid in chrysanthemum cultivation.     

Effects of UV pretreatment on microbial community structure and metabolic characteristics in a subsequent biofilter treating gaseous chlorobenzene

To provide insight into effects of UV pretreatment on microorganisms in subsequent biofilters, the changes of microbial community structure and metabolic characteristics of biofilters with (UV–BF) and without (BF) UV pretreatment were studied. The respiratory quinone and BIOLOG methods were used to analyze microbial community structure and metabolic characteristics, respectively. The results indicated the quinone profiles, the species of dominant quinone and its molar fraction of the biofilm in both biofilters showed different behaviors. Ubiquinones-8 and menaquinone-9(H₂) was the dominant quinones in BF and UV–BF processes, respectively. The dissimilarity index of two biofilters markedly increased to nearly 60 after turning on the UV lamp. The microbial samples from UV–BF process showed higher metabolic activities of 0.040 cm⁻¹ h⁻¹ than 0.028 cm⁻¹ h⁻¹ in BF process. Moreover, the microorganisms in both biofilters demonstrated distinct metabolic characteristics. Further, the performance of biofilters showed good correlation with microbial community structure and metabolic characteristics.     

Biological treatment of n-hexane and methanol in trickle bed air biofilters under acidic conditions

This study focuses on evaluating the degradation of n-hexane/methanol mixture in trickle-bed-air-biofilters (TBABs). Two different concentration ratios of methanol:n-hexane were evaluated (3:1) for TBAB “A” and (5:1) for TBAB “B”. Both TBABs were run and fed with nutrients buffered at pH 4 for encouraging the growth of fungi. The TBABs were loaded with pelletized diatomaceous earth support media and were run at an empty bed residence time of 120 s. n-Hexane loading rates (LRs) ranged from 0.9 to 13.2 g/m³ h for both TBABs. The corresponding methanol LRs varied from 2.3 to 37.7 g/m³ h and from 4.6 to 64.5 g/m³ h for TBABs “A” and “B”, respectively. Experimental results have shown that the degradation of n-hexane in presence of methanol is enhanced for n-hexane LRs less than 10.6 g/m³ h as compared to previous study for sole-fed n-hexane, but for n-hexane LRs of 13.2 g/m³ h, the performance of TBABs in eliminating n-hexane depended on the methanol to n-hexane ratios. The impact was less severe for TBAB “A” (RE 85%) as compared to TBAB “B” (RE 72%). This is attributed to the high LRs of methanol in TBAB “B”. n-Hexane performance stability was another advantage attained.