Herbivory by an Outbreaking Moth Increases Emissions of Biogenic Volatiles and Leads to Enhanced Secondary Organic Aerosol Formation Capacity.

In addition to climate warming, greater herbivore pressure is anticipated to enhance the emissions of climate-relevant biogenic volatile organic compounds (VOCs) from boreal and subarctic forests and promote the formation of secondary aerosols (SOA) in the atmosphere. We evaluated the effects of Epirrita autumnata, an outbreaking geometrid moth, feeding and larval density on herbivore-induced VOC emissions from mountain birch in laboratory experiments and assessed the impact of these emissions on SOA formation via ozonolysis in chamber experiments. The results show that herbivore-induced VOC emissions were strongly dependent on larval density. Compared to controls without larval feeding, clear new particle formation by nucleation in the reaction chamber was observed, and the SOA mass loadings in the insect-infested samples were significantly higher (up to 150-fold). To our knowledge, this study provides the first controlled documentation of SOA formation from direct VOC emission of deciduous trees damaged by known defoliating herbivores and suggests that chewing damage on mountain birch foliage could significantly increase reactive VOC emissions that can importantly contribute to SOA formation in subarctic forests. Additional feeding experiments on related silver birch confirmed the SOA results. Thus, herbivory-driven volatiles are likely to play a major role in future biosphere-vegetation feedbacks such as sun-screening under daily 24 h sunshine in the subarctic.

An amorphous solid state of biogenic secondary organic aerosol particles.

Secondary organic aerosol (SOA) particles are formed in the atmosphere from condensable oxidation products of anthropogenic and biogenic volatile organic compounds (VOCs). On a global scale, biogenic VOCs account for about 90% of VOC emissions and of SOA formation (90 billion kilograms of carbon per year). SOA particles can scatter radiation and act as cloud condensation or ice nuclei, and thereby influence the Earth's radiation balance and climate. They consist of a myriad of different compounds with varying physicochemical properties, and little information is available on the phase state of SOA particles. Gas-particle partitioning models usually assume that SOA particles are liquid, but here we present experimental evidence that they can be solid under ambient conditions. We investigated biogenic SOA particles formed from oxidation products of VOCs in plant chamber experiments and in boreal forests within a few hours after atmospheric nucleation events. On the basis of observed particle bouncing in an aerosol impactor and of electron microscopy we conclude that biogenic SOA particles can adopt an amorphous solid-most probably glassy-state. This amorphous solid state should provoke a rethinking of SOA processes because it may influence the partitioning of semi-volatile compounds, reduce the rate of heterogeneous chemical reactions, affect the particles' ability to accommodate water and act as cloud condensation or ice nuclei, and change the atmospheric lifetime of the particles. Thus, the results of this study challenge traditional views of the kinetics and thermodynamics of SOA formation and transformation in the atmosphere and their implications for air quality and climate.

Effective density and morphology of particles emitted from small-scale combustion of various wood fuels.

The effective density of fine particles emitted from small-scale wood combustion of various fuels were determined with a system consisting of an aerosol particle mass analyzer and a scanning mobility particle sizer (APM-SMPS). A novel sampling chamber was combined to the system to enable measurements of highly fluctuating combustion processes. In addition, mass-mobility exponents (relates mass and mobility size) were determined from the density data to describe the shape of the particles. Particle size, type of fuel, combustion phase, and combustion conditions were found to have an effect on the effective density and the particle shape. For example, steady combustion phase produced agglomerates with effective density of roughly 1 g cm(-3) for small particles, decreasing to 0.25 g cm(-3) for 400 nm particles. The effective density was higher for particles emitted from glowing embers phase (ca. 1-2 g cm(-3)), and a clear size dependency was not observed as the particles were nearly spherical in shape. This study shows that a single value cannot be used for the effective density of particles emitted from wood combustion.

Nanosized TiO2 caused minor airflow limitation in the murine airways.

The use of nanotechnology is increasing exponentially, whereas the possible adverse health effects of engineered nanoparticles (NPs) are so far less known. Standardized mouse bioassay was used to study sensory and pulmonary irritation, airflow limitation, and inflammation potency of nanosized TiO(2). Single exposure (0.5 h) to in situ generated TiO(2) (primary particle size 20 nm; geometric mean diameters of 91, 113, and 130 nm at mass concentrations of 8, 20, and 30 mg/m(3), respectively; crystal phase anatase + brookite (3:1)) caused airflow limitation in the conducting airways at each studied exposure concentration, which was shown as a reduction in expiratory flow, being at the lowest 73% of baseline. The response was not dose dependent. Repeated exposures (altogether 16 h, 1 h/day, 4 days/week for 4 weeks) to TiO(2) at mass concentration of 30 mg/m(3) caused as intense airflow limitation effect as the single exposures, and the extent of the responses stayed about the same along the exposure days. Sensory irritation was fairly minor. Pulmonary irritation was more pronounced during the latter part of the repeated exposures compared to the single exposures and the beginning of the repeated exposures. Sensory and pulmonary irritation were observed also in the control group, and, therefore, reaction by-products (NO(2) and C(3)H(6)) may have contributed to the irritation effects. TiO(2) NPs accumulated mainly in the pulmonary macrophages, and they did not cause nasal or pulmonary inflammation. In conclusion, the irritation and inflammation potencies of studied TiO(2) seemed to be low.

Ion mobility distributions during the initial stages of new particle formation by the ozonolysis of α-pinene.

An ion mobility spectrometer (IMS) was used to study gas phase compounds during nucleation and growth of secondary organic aerosols (SOA). In this study SOA particles were generated by oxidizing α-pinene with O(3) and OH in a 6 m(3) reaction chamber. Positive ion peaks with reduced mobilities of 1.59 cm(2)(Vs)(-1) and 1.05 cm(2)(Vs)(-1) were observed 7 min after α-pinene and ozone were added to the chamber. The detected compounds can be associated with low volatility oxidation products of α-pinene, which have been suggested to participate in new particle formation. This is the first time that IMS has been applied to laboratory studies of SOA formation. IMS was found suitable for continuous online monitoring of the SOA formation process, allowing for highly sensitive detection of gas phase species that are thought to initiate new particle formation.

Inhaled silica-coated TiO2 nanoparticles induced airway irritation, airflow limitation and inflammation in mice.

The wide use of nanotechnology is here to stay. However, the knowledge on the health effects of different engineered nanomaterials (ENMs) is lacking. In this study, irritation and inflammation potential of commercially available silica-coated TiO2 ENMs (10 × 40 nm, rutile) were studied. Single exposure (30 min) at mass concentrations 5, 10, 20 and 30 mg/m(3), and repeated exposure (altogether 16 h, 1 h/day, 4 days/week for 4 weeks) at mass concentration of 30 mg/m(3) to silica-coated TiO2 induced first phase of pulmonary irritation (P1), which was seen as rapid, shallow breathing. During repeated exposures, P1 effect was partly evolved into more intense pulmonary irritation. Also sensory irritation was observed at the beginning of both single and repeated exposure periods, and the effect intensified during repeated exposures. Airflow limitation started to develop during repeated exposures. Repeated exposure to silica-coated TiO2 ENMs induced also pulmonary inflammation: inflammatory cells infiltrated in peribronchial and perivascular areas of the lungs, neutrophils were found in BAL fluids, and the number of CD3 and CD4 positive T cells increased significantly. In line with these results, pulmonary mRNA expression of chemokines CXCL1, CXCL5 and CXCL9 was enhanced. Also expression of mRNA levels of proinflammatory cytokines TNF-α and IL-6 was elevated after repeated exposures. Taken together, these results indicated that silica-coated TiO2 ENMs induce pulmonary and sensory irritation after single and repeated exposure, and airflow limitation and pulmonary inflammation after repeated exposure.

Contrasting responses of silver birch VOC emissions to short- and long-term herbivory.

There is a need to incorporate the effects of herbivore damage into future models of plant volatile organic compound (VOC) emissions at leaf or canopy levels. Short-term (a few seconds to 48 h) changes in shoot VOC emissions of silver birch (Betula pendula Roth) in response to feeding by geometrid moths (Erannis defoliaria Hübner) were monitored online by proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS). In addition, two separate field experiments were established to study the effects of long-term foliage herbivory (FH, 30-32 days of feeding by geometrids Agriopis aurantiaria (Clerck) and E. defoliaria in two consecutive years) and bark herbivory (BH, 21 days of feeding by the pine weevil (Hylobius abietis L.) in the first year) on shoot and rhizosphere VOC emissions of three silver birch genotypes (gt14, gt15 and Hausjärvi provenance). Online monitoring of VOCs emitted from foliage damaged by geometrid larvae showed rapid bursts of green leaf volatiles (GLVs) immediately after feeding activity, whereas terpenoid emissions had a tendency to gradually increase during the monitoring period. Long-term FH caused transient increases in total monoterpene (MT) emissions from gt14 and sesquiterpene (SQT) emissions from Hausjärvi provenance, mainly in the last experimental season. In the BH experiment, genotype effects were detected, with gt14 trees having significantly higher total MT emissions compared with other genotypes. Only MTs were detected in the rhizosphere samples of both field experiments, but their emission rates were unaffected by genotype or herbivory. The results suggest that silver birch shows a rapid VOC emission response to short-term foliage herbivory, whereas the response to long-term foliage herbivory and bark herbivory is less pronounced and variable at different time points.

Effects of species-specific leaf characteristics and reduced water availability on fine particle capture efficiency of trees.

Trees can improve air quality by capturing particles in their foliage. We determined the particle capture efficiencies of coniferous Pinus sylvestris and three broadleaved species: Betula pendula, Betula pubescens and Tilia vulgaris in a wind tunnel using NaCl particles. The importance of leaf surface structure, physiology and moderate soil drought on the particle capture efficiencies of the trees were determined. The results confirm earlier findings of more efficient particle capture by conifers compared to broadleaved plants. The particle capture efficiency of P. sylvestris (0.21%) was significantly higher than those of B. pubescens, T. vulgaris and B. pendula (0.083%, 0.047%, 0.043%, respectively). The small leaf size of P. sylvestris was the major characteristic that increased particle capture. Among the broadleaved species, low leaf wettability, low stomatal density and leaf hairiness increased particle capture. Moderate soil drought tended to increase particle capture efficiency of P. sylvestris.

Airway exposure to silica-coated TiO2 nanoparticles induces pulmonary neutrophilia in mice.

The importance of nanotechnologies and engineered nanoparticles has grown rapidly. It is therefore crucial to acquire up-to-date knowledge of the possible harmful health effects of these materials. Since a multitude of different types of nanosized titanium dioxide (TiO(2)) particles are used in industry, we explored their inflammatory potential using mouse and cell models. BALB/c mice were exposed by inhalation for 2 h, 2 h on 4 consecutive days, or 2 h on 4 consecutive days for 4 weeks to several commercial TiO(2) nanoparticles, SiO(2) nanoparticles, and to nanosized TiO(2) generated in a gas-to-particle conversion process at 10 mg/m(3). In addition, effects of in vitro exposure of human macrophages and fibroblasts (MRC-9) to the different particles were assessed. SiO(2)-coated rutile TiO(2) nanoparticles (cnTiO(2)) was the only sample tested that elicited clear-cut pulmonary neutrophilia. Uncoated rutile and anatase as well as nanosized SiO(2) did not induce significant inflammation. Pulmonary neutrophilia was accompanied by increased expression of tumor necrosis factor-alpha (TNF-alpha) and neutrophil-attracting chemokine CXCL1 in the lung tissue. TiO(2) particles accumulated almost exclusively in the alveolar macrophages. In vitro exposure of murine and human macrophages to cnTiO(2) elicited significant induction of TNF-alpha and neutrophil-attracting chemokines. Stimulation of human fibroblasts with cnTiO(2)-activated macrophage supernatant induced high expression of neutrophil-attracting chemokines, CXCL1 and CXCL8. Interestingly, the level of lung inflammation could not be explained by the surface area of the particles, their primary or agglomerate particle size, or radical formation capacity but is rather explained by the surface coating. Our findings emphasize that it is vitally important to take into account in the risk assessment that alterations of nanoparticles, e.g., by surface coating, may drastically change their toxicological potential.