Questions 6277. An average of 0.2 ppm Hg is found in the 3 X 1012 kg of coal burned annually in the world. Assuminga residence time of one year and uniform distribution of t h e mercury in the lower 1000 m of the atmosphere, calculate the average concentration of mercury in the atmosphere due to this source. The radius of the earth is about 107m. You breathe about 2 X lo7 cm" of air per day. How does your daily inhalation of Hg comDare with the toxic dose of 300 d d a v ? ~ 2 7 8 . Fresh water normally contains about 10 ppm 0 2 , surface ocean water about 8 ppm. The sewage per person in the US. requires about 0.060 kg of Odday to oxidize it to harmless products. If the average person also flushes 105cm3 of water with his daily sewage does this supply enough 0 2 to oxidize the sewage? 6279. The Torrey Canyon steamship oil spill spread 1.19 X loHkg on the ocean. If the resulting slick covered 500 square kilometers (200 square miles) what was its average thickness. 0280. A kidnev filters the hlood cells and other laree h a t a rate of about 130 mllmin, or 1 b&es from the Ildav. About 1.5 Ildav. . . . containing most of the unwanted metutx,litt!s, is excreted as urine while the rest (in(hdingglucose and other desirable moleculesl are rrabsorbed into the blond thnwgh the renal t t h l e s . The kidnry filters are rssrntially rhar,diaphraymi pertorated by holeitoosmnll to pass blood
cells. Discuss the molecular transport processes probably occurring across the tubule membranes. Q281. Almonds and other foods contain cyanide which is converted in the liver and kidney by sulfurtransferase, to CNS- in a catalyzed reaction with S20:12-. Write a likely net reaction. 6282. About 5000 persons per year die of carbon monoxide poisoning in the US. The danger level is reached when 50% or more of the hemoglobin sites which can hold 0?actually hold CO. These sites hold CO 250 times more strongly than they hold Or. Calculate the danger level of CO in the atmosphere. 6283. Most insects, mammals, reptiles, and birds can oxidize foreign compounds as well as their foods, but most fish and amphibia can~onlyoxidize their normal foods. Interpret.
first-year, college level course, a data handbook, and a willingness to apply fundamental chemical ideas to the systems which surround us (or even are inside us). Contributions for possible inclusion are solicited, Initiated in the January, 1912 issue of thi.9 Journal.
Answers A277.
3 X 1012kg coal X 0.2 X 10-VkgHg/kgcoal) = 6 X
lo5
kg Hg. [6 X 10"(kg Hglyr) X lOV(pg/kg)/411(lo7X 102)2cm2X 105
cm] X 2 X lo7 (cmt')I4 X lo2 (dalyr) = 3 X lOW((rg1da) average intake if He is unifarmlv distributed. I t is not, of course, but the chance of obtainine ineestion of He- from the air - an;. significant is negligible except near power plants. A278. Assume flushing with fresh water (10 ppm O2 = 10 X 10-"0&H20). l D 5 c d H 2 0= lD5gHzO;lD5gH;0 X 10 x l0W g o & H 2 0 = 1g 0 2 in the water used for flushing. But 0.06 kg = 60 g of Oxare required so the flushsewage has only 'h the required oxygen. Even allowing for all the other household water (bath, lavatory, sinks) it is clear that sewage reaches the sewage plant with most of its biological oxygen demand (BOD) unmet. Oxygenation is a major part of sewage disposal. A279. Assume a density of 2 1 glcm". Then 1.19 X 10Rkg = 1.19 X 10" g = 1.19 X 10" cm:'. 500 kmz = 600 X (10" m/km)2 X (100 emlm)" = 5 X 1012cm2. 1X 10" cm9/5 X 10'2cm2= 0.02 cm as an average thickness. A280. Urine clearly has a lower concentration of water than the plasma; thus its transfer across the tubules cannot be by simple diffusion or osmotic flow. There must be some enerev used as the
190 Vda, a large volume. A281. The enzyme,sulfurtransferase, should (from its name) transfer sulfur atoms. Assuming this gives CN-
+ S20.,2- = CNS- + SO.;l-
A282. If the danger level is a t 50-50 occupancyand the CO is held 250 times morestrongly, the COIO? ratio in the atmosphere must be 250A. Air is 20 mole % 07 so the daneerous CO level must with this argument. A283. Fish are bathed in a continual flow of water and can eliminate foreign materials directly into it. Air-bathed animals must concentrate the foreign material, for example into urine. Clearly polar substances, which can be farmed by oxidizing the foreien materials. are concentrated in water more easilv than are air-bathed species.
Volume 54, Number I, January 1977 / 37
