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The impact of sub-lethal concentrations (0.05, 0.5, 5 μmol L −1 ) of the heavy metals copper (Cu), chromium (Cr), zinc (Zn), cadmium (Cd) and lead (Pb) on the growth and photosynthesis of Chlorella vulgaris was studied during 96 h exposure experiments. The results showed that the effects of these five metals on the growth of Chlorella vulgaris were dependent on both concentration and exposure time. It was found that 5 μmol L −1 treatments of Cu, Cr, Zn, Cd and Pb significantly inhibited the growth of Chlorella vulgaris, and the effect became weaker with an increase in exposure duration. Different effects on chlorophyll fluorescence were found for different metals, with Cu and Cr having an inhibiting effect and Zn and Cd having a promoting effect. The effects of heavy metals upon the growth and photosynthesis of Chlorella vulgaris were independent of each other and not causally related.heavy metal, sub-lethal, Chlorella vulgaris, growth, photosynthesis Citation:Ouyang H L, Kong X Z, He W, et al. Effects of five heavy metals at sub-lethal concentrations on the growth and photosynthesis of Chlorella vulgaris.

Black carbon (BC) is a key short-lived climate change forcer. Motor vehicles are important sources of BC in the environment. BC emission factors (EF(BC)), defined as BC emitted per mass of fuel consumed, are critical in the development of BC emission inventories for motor vehicles. However, measured EF(BC) for motor vehicles vary in orders of magnitude, which is one of the major sources of uncertainty in the estimation of emissions. In this study, the main factors affecting EF(BC) for motor vehicles were investigated based on 385 measured EF(BC) collected from the literature. It was found that EF(BC) for motor vehicles of a given year in a particular country can be predicted using gross domestic product per capita (GDP(c)), temperature, and the year a country's GDP(c) reached 3000 USD (Y(3000)). GDP(c) represents technical progress in terms of emission control, while Y(3000) suggest the technical transfer from developed to developing countries. For global BC emission calculations, 87 and 64% of the variation can be eliminated for diesel and gasoline vehicles by using this model. In addition to a reduction in uncertainty, the model can be used to develop a global on-road vehicle BC emission inventory with spatial and temporal resolution.

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