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The Republic of Korea, henceforth referred to as Korea, has successfully implemented intensive programs of reforestation and forest management over the last 30 years to restore its once‐rich forests. This nationwide effort has resulted in a massive accumulation of less than 30‐year‐old tree biomass, which now accounts for about 72% of the total forest biomass in Korea. Here we use a forest tree inventory data set for Korea to calculate the effectiveness of these planted trees in absorbing excess carbon dioxide from the atmosphere during the period 1954–2000. The forest carbon density in Korea has increased from 5–7 megagrams of carbon per hectare (Mg C ha−1, Mg = 106 grams) in the period 1955–1973 to more than 30 Mg C ha−1 in the late 1990s. The calculated carbon uptake has increased from a mean rate of 0.001 petagrams of carbon per year (Pg C yr−1, Pg = 1015 grams) in the period 1955–1973 to as high as 0.012 Pg C yr−1 in recent years, largely due to the 30‐year implementation of reforestation and forest management projects. The contemporary rate of carbon uptake by the total Korean tree biomass is approximately one‐half of the 1994–1998 mean rate of carbon uptake by the total Chinese forest biomass of 0.026 Pg C yr−1 [Fang et al., 2001]; the Chinese forest biomass has recently been found to be a significant carbon sink in northern temperate regions. The observed uptake rate for Korea is remarkably high, considering the fact that the total area of Korean forests is approximately 16 times smaller than that of Chinese forests. Our results show that long‐term rates of carbon sequestration by nationwide forests can be increased substantially through reforestation and forest management.

Background Titanium dioxide (TiO 2 ) nanoparticles are among the most manufactured nanomaterials in the industry, and are used in food products, toothpastes, cosmetics and paints. Pregnant women as well as their conceptuses may be exposed to TiO 2 nanoparticles; however, the potential effects of these nanoparticles during pregnancy are controversial, and their internal distribution has not been investigated. Therefore, in this study, we investigated the potential effects of oral exposure to TiO 2 nanoparticles and their distribution during pregnancy. TiO 2 nanoparticles were orally administered to pregnant Sprague-Dawley rats (12 females per group) from gestation days (GDs) 6 to 19 at dosage levels of 0, 100, 300 and 1000 mg/kg/day, and then cesarean sections were conducted on GD 20. Results In the maternal and embryo-fetal examinations, there were no marked toxicities in terms of general clinical signs, body weight, food consumption, organ weights, macroscopic findings, cesarean section parameters and fetal morphological examinations. In the distribution analysis, titanium contents were increased in the maternal liver, maternal brain and placenta after exposure to high doses of TiO 2 nanoparticles. Conclusion Oral exposure to TiO 2 during pregnancy increased the titanium concentrations in the maternal liver, maternal brain and placenta, but these levels did not induce marked toxicities in maternal animals or affect embryo-fetal development. These results could be used to evaluate the human risk assessment of TiO 2 nanoparticle oral exposure during pregnancy, and additional comprehensive toxicity studies are deemed necessary considering the possibility of complex exposure scenarios and the various sizes of TiO 2 nanoparticles.

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