Biogenic volatile organic compound emissions (BVOCs). I. Identifications from three continental sites in the U.S

Vegetation composition and biomass were surveyed for three specific sites in Atlanta, GA; near Rhinelander, WI; and near Hayden, CO. At each research site emissions of biogenic volatile organic compounds (BVOCs) from the dominant vegetation species were sampled by enclosing branches in bag enclosure systems and sampling the equilibrium head space onto multi-stage solid adsorbent cartridges. Analysis was performed using a thermal desorption technique with gas chromatography (GC) separation and mass spectrometry (MS) detection. Identification of BVOCs covering the GC retention index range (stationary phase DB-1) from approximately 400 to 1400 was achieved (volatilities C4-C14).     

Endocrine disrupting nonyl- and octylphenol in infant food in Germany: considerable daily intake of nonylphenol for babies

Nonylphenol and octylphenol are persistent endocrine disrupters that are priority substances of the European Union Water Framework Directive. Their presence in the environment has caused increasing concern about their impact to human health. Infants are more sensitive to hormonal impacts of environmental chemicals than adults. The results of the present study indicate that nonylphenol is ubiquitous in foodstuffs for babies and toddlers commercially available in Germany, while octylphenol could only be determined in 80% of all food samples. The daily intakes based on consumption studies in μg nonylphenol kg⁻¹ body weight per day for high consumers in the baby category (0.23-0.65 μg kg⁻¹ bw d⁻¹) were relatively high. This could lead to a higher risk especially for babies.     

The impacts of reactive terpene emissions from plants on air quality in Las Vegas,Nevada

A three-part study was conducted to quantify the impact of landscaped vegetation on air quality in a rapidly expanding urban area in the arid southeastern United States. The study combines in situ, plant-level measurements, a spatial emissions inventory, and a photochemical box model. Maximum plant-level basal emission rates were moderate: 18.1 μgC gdw^?1 h^?1 (Washingtonia spp., palms) for isoprene and 9.56 μgC gdw^?1 h^?1 (Fraxinus velutina, Arizona ash) for monoterpenes. Sesquiterpene emission rates were low for plant species selected in this study, with no measurement exceeding 0.1 μgC gdw^?1 h^?1. The high ambient temperatures combined with moderate plant-level emission factors resulted in landscape emission factors that were low (250–640 μgC m^?2 h^?1) compared to more mesic environments (e.g., the southeastern United States). The Regional Atmospheric Chemistry Mechanism (RACM) was modified to include a new reaction pathway for ocimene. Using measured concentrations of anthropogenic hydrocarbons and other reactive air pollutants (NO_x, ozone), the box model employing the RACM mechanism revealed that these modest emissions could have a significant impact on air quality. For a suburban location that was downwind of the urban core (high NO_x; low anthropogenic hydrocarbons), biogenic terpenes increased time-dependent ozone production rates by a factor of 50. Our study demonstrates that low-biomass density landscapes emit sufficient biogenic terpenes to have a significant impact on regional air quality.     

Effect of modulated at different low frequencies microwave radiation on human EEG

This study is aimed to clarify whether effect of low-level microwave radiation on human brain differs at different modulation frequencies. Resting EEG recordings were done on different groups of healthy volunteers. The 450 MHz microwave radiation modulated at 40 and 70 Hz (15 subjects) and 217 and 1,000 Hz (19 subjects) frequencies was applied. The results of our previous study at 7, 14 and 21 Hz modulation were included into analysis. Ten cycles of the exposure (1 min off and 1 min on) at each fixed modulation frequencies were applied. The field power density at the scalp was always 0.16 mW/cm². Our results showed that microwave exposure increased the EEG energy at EEG frequencies lower or close to the modulation frequency. No effect was detected at EEG frequencies higher than the modulation frequency. Statistically significant changes were caused by exposure in the EEG alpha and beta frequency bands; no significant effect was detected in the theta band. Our results suggest that telecommunication devices with complex spectrum of modulation frequencies like mobile phone can affect all human EEG frequency bands.     

Degradation of a chiral nonylphenol isomer in two agricultural soils

The degradation of a chiral nonylphenol isomer, 4-(1-ethyl-1,4-dimethylpentyl)phenol (NP₁₁₂), in two agricultural soils from Monheim and Dortmund, Germany has been studied. The degradation of NP₁₁₂ and the formation of a nitro-nonylphenol metabolite were determined by means of GC-MS analysis. The degradation followed bi-exponential order kinetics, with half-life of less than 5 days in both soils. The nitro-metabolite was found at different concentration levels in the two soils. The nitro-metabolite of NP₁₁₂ was more persistent than its parent compound. After 150 days about 13% of the initially applied NP₁₁₂ remained in the Monheim soil as its nitro-metabolite. Results of the E-screen assay revealed that the nitro-NP₁₁₂ has oestrogenic potency of 85% of that of NP₁₁₂. Furthermore, the results of chiral GC-MS analysis revealed that no chiral degradation of NP₁₁₂ occurred in this study.     

西双版纳热带森林挥发性有机物的观测研究

2002年7月中旬利用异戊二烯通量测定系统对云南西双版纳热带森林异戊二烯的排放通量进行了连续测量,同时对光合有效辐射(PAR)、气温、湿度、风等参数进行了观测.结果表明,热带地区人工橡胶林区域湿季异戊二烯的排放有明显的日变化规律,中午前后为一天中的最大值,异戊二烯排放通量的日平均值在0.85～0.24mgC/(m²h)之间.对小时值和日平均值而言,异戊二烯的排放与PAR和气温的变化规律比较一致,但它对PAR比对气温更加敏感.不同的天气状况对异戊二烯的排放有非常明显的影响.橡胶林是一个单萜烯排放者,其单萜烯的排放速率明显依赖于PAR.橡胶林和热带雨林冠层上空异戊二烯和单萜烯的浓度也有明显的日变化规律,而且橡胶林区域的异戊二烯和单萜烯的浓度均明显高于热带雨林.     

Aerosol properties,in-canopy gradients,turbulent fluxes and VOC concentrations at a pristine forest site in Amazonia

Aerosol physical and chemical properties were measured in a forest site in central Amazonia (Cuieiras reservation, 2.61S; 60.21W) during the dry season of 2004 (Aug–Oct). Aerosol light scattering and absorption, mass concentration, elemental composition and size distributions were measured at three tower levels (Ground: 2 m; Canopy: 28 m, and Top: 40 m). For the first time, simultaneous eddy covariance fluxes of fine mode particles and volatile organic compounds (VOC) were measured above the Amazonian forest canopy. Aerosol fluxes were measured by eddy covariance using a Condensation Particle Counter (CPC) and a sonic anemometer. VOC fluxes were measured by disjunct eddy covariance using a Proton Transfer Reaction Mass Spectrometer (PTR-MS). At nighttime, a strong vertical gradient of phosphorus and potassium in the aerosol coarse mode was observed, with higher concentrations at Ground level. This suggests a source of primary biogenic particles below the canopy. Equivalent black carbon measurements indicate the presence of light-absorbing aerosols from biogenic origin. Aerosol number size distributions typically consisted of superimposed Aitken (76 nm) and accumulation modes (144 nm), without clear events of new particle formation. Isoprene and monoterpene fluxes reached respectively 7.4 and 0.82 mg m^?2 s^?1 around noon. An average fine particle flux of 0.05 ± 0.10 10⁶ m^?2 s^?1 was calculated, denoting an equilibrium between emission and deposition fluxes of fine mode particles at daytime. No significant correlations were found between VOC and fine mode aerosol concentrations or fluxes.