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Inorganic mercury is toxic when humans or wildlife are exposed to high levels for a short peri- od of time. Organic methylmercury has a greater tendency to accumulate in the body over time, eventually causing harm, even in small amounts. Methylmercury has the three properties that make substances particularly harmful to humans and other organisms — it persists, it bioaccumulates, and it is toxic to most life forms. The health effects of mercury are described in more detail in the next chapter of this primer. The terms “biological uptake” and “bioaccumu- lation” describe the processes whereby methylmer- cury can enter the food chain — either directly from the water or through the consumption of small. | 451 Air Pollution and Environmental Chemistry The facts Man-made emissions have contributed to two conditions that are under close scrutiny by the scientific community and the developed nations world-wide. 1. Global warming which is an increase in Green House Gases 2. Ozone depletion in upper stratosphere What is the public s perception of the facts A. Depends on which side of the political arena you are on. Until very recently partisan politicians have denied and distorted the facts to John Q. Public. Respect for science and its findings has been diminished due to wishful thinking. We all like to hide our heads in the sand sometimes but at what cost 452 The Greenhouse Effect is the process in which the emission of infrared radiation by the atmosphere warms a planet s surface. The name comes from an incorrect analogy with the warming of air inside a greenhouse compared to the air outside the greenhouse. The greenhouse effect was discovered by Joseph Fourier in 1824 and first investigated quantitatively by Svante Arrhenius in 1896. The Earth s average surface temperature of 14 C 57 F would otherwise be about -19 C -2.2 F in the absence of the greenhouse effect. Global warming a recent warming of the Earth s lower atmosphere is believed to be the result of an enhanced greenhouse effect due to increased concentrations of greenhouse gases in the atmosphere. In addition to the Earth Mars and Venus have greenhouse effects. The Earth receives energy from the Sun in the form of radiation. Most of the energy is in visible wavelengths and in infrared wavelengths that are near the visible range often called near infrared . The Earth reflects about 30 of the incoming solar radiation. The remaining 70 is absorbed warming the land atmosphere and oceans. For the Earth s temperature to be in steady state so that the Earth does not rapidly heat or cool this absorbed solar radiation must be very closely balanced by energy radiated back to space in the infrared wavelengths. Since the
