Although Krakow has relatively high ambient concentrations of PAH from coal - burning and vehicle emissions, levels are within the range seen in many other urban areas worldwide. (sciencedaily.com)
Called AmazonFACE (Free - Air Carbon dioxide Enrichment), it's based on a simple idea: For 12 years, researchers will spray pure CO2 into instrumented plots in the rainforest northwest of Manaus, Brazil, raising ambient concentrations to 600 parts per million — a level the world could reach as early as 2050 — all the while taking meticulous measurements to determine how the gas affects the growth of plants. (science.sciencemag.org)
A clear, odorless gas that is non-toxic to humans at many times ambient concentrations, carbon dioxide is an essential plant nutrient, and elevated concentrations boost most plants» biomass productivity, water use efficiency, and resistance to environmental stresses such as ozone pollution. (masterresource.org)