MNPs coated with amorphous silica are protected from acidic erosion. Correspondingly, the particle stability translates into reduced cytotoxicity and cellular influence on human airway epithelial cells.

Environmental context In the coastal and ocean environment, oil spills and ship movement can produce hazardous, organic aerosols. In this study, the role of sea salt in the formation processes of crude-oil-derived organic aerosols derived was explored, and it was found that sea salt can greatly increase the formation and growth of these toxic aerosols. Understanding of this process is crucial for evaluating the effect of oil spills and ship movements on air quality and human health. Abstract Dual, large (52m3), outdoor chambers were used to investigate the effect of aerosol aqueous phase chemistry on the secondary organic aerosol (SOA) yields of the photooxidation products of aromatic hydrocarbons in the coastal environment. Toluene and 1,3,5-trimethylbenzene were photochemically oxidised in the presence and absence of inorganic seeds (sea salt aerosol (SSA) or NaCl) at low NOx conditions. Overall, the presence of SSA, which was shown to contain water even at low relative humidities (RHs), led to higher SOA yields than the presence of NaCl seeds and the seedless condition. The results suggest that SOA yields in the coastal environment will be higher than those produced in terrestrial environment. To study the effect of SOA formation on the chemical composition of SSA, inorganic species were measured using a particle-into-liquid-sampler coupled to an ion chromatograph. The hygroscopic properties of the SSA internally mixed with SOA were analysed using a Fourier-transform infrared spectrometer. The fresh SSA shows a weak phase transition whereas no clear phase transition appeared in the aged SSA. The depletion of Cl– due to the accommodation of nitric acid and carboxylic acids on the surface of SSA coincides with changes in aerosol hygroscopic properties.

A fundamental aspect of the carbon cycle is the exchange of carbon between plants and the atmosphere. It is therefore important to understand factors that affect differences in gas exchange and carbon balance within and among species. Concentrations of non-structural carbohydrates are often used as a proxy for carbon balance. We determined diel patterns of leaf carbohydrate concentrations in relation to irradiance (sun vs shade) in seedlings and mature trees of two sympatric oak species (Quercus virginiana and Quercus hemisphaerica). For seedlings we also measured leaf gas exchange. Higher sun exposure significantly increased photosynthesis and carbohydrate concentrations in both species. Carbohydrate concentrations of seedling leaves showed strong diel fluctuations, whereas concentrations in mature tree leaves did not. This contrast might be attributed to faster carbohydrate export from leaves of mature trees. The difference in sink strength between seedlings and adults may be related to the decreasing ratio of leaf mass to plant mass with ontogeny, increasing the demand for carbohydrates per unit leaf mass. Seedlings and mature trees are clearly functionally different and care must be taken when extrapolating results from seedling experiments to mature trees.