In the present study, we evaluated the protective effect of exogenous heme oxygenase-1 (HO-1 EC 1.14.99.3) inducer hematin against mercury-induced oxidative damage in the roots of Alfalfa (Medicago sativa L.). Plants exposed to mercury (HgCl 2 ) exhibited a significant increase of lipid peroxidation, as well as inhibition of root elongation. However, hematin (50 µM) supplementation to HgCl 2 (100 µmol/L) treated plants effectively reduced the lipid peroxidation and partially increased the root elongation. These responses were mimicked by the application of aqueous solution of carbon monoxide (CO) with 50% saturation. Also, treatment with hematin could result in the potent induction of HO-1 transcript in the root tissues, as detected 12 h following treatment. Moreover, the activation of anti-oxidant enzyme, including glutathione reductase, monodehydroascorbate reductase and superoxide dismutase activities, and the decrease of lipoxygenase activity, were induced by hematin at 12 h or 24 h, which was further confirmed by histochemical staining for the detection of lipid peroxidation and loss of membrane integrity. Whereas, ascorbate peroxidase and guaiacol peroxidase isozyme activities or their transcripts were reduced, respectively, indicating that hydrogen peroxide might act as a signal to mediate Hgtolerance at the beginning of treatment. The ameliorating effects of hematin were specific, since the CO scavenger hemoglobin differentially reversed the above actions. Taken together, our results suggested that hematin exhibits a vital role in protecting the plant against Hg-induced oxidative damage.

Volatile organic compounds (VOCs) emitted from surface coatings have caused growing public concern for air quality. Even the low-emitted VOC impact from water-based paints on indoor air quality in urban areas has caused concern. This paper presents experimental data using a mathematical model to simulate dynamic VOC emissions from water-based paints that is based on mass transfer and molecular diffusion theories. A series of field-analogous experiments were carried out to continuously measure the VOCs emitted from two typical water-based paints using a gas chromatography-flame-ionization detector monitor in an artificial wind tunnel system. In the study cases, the mass flux of VOCs emitted from the water-based paints was up to 50 g/m 2 sec. It was found that the time needed to completely emit VOCs from water-based paints is just hundreds of seconds. However, the order of magnitude of the VOC emission rate from water-based paints is not lower than that from some dry building materials and solvent-based paints. The experimental data were used to produce a useful semiempirical correlation to estimate the VOC emission rates for water-based paints. This correlation is valid under appropriate conditions as suggested by this work with a statistical deviation of Ϯ7.6%. With this correlation, it seems feasible to predict the dynamic emission rates for VOCs during a painting process. This correlation is applicable for assessing the hazardous air pollutant impact on indoor air quality or for environmental risk assessment. Associated with the dynamic VOC emission characterization, the air-exchange rate effect on the VOC emission rates is also discussed.