LETTERS HOSE maintains minimum heat
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Designed for users who are concerned only about their minimum temperature needs! The new HeatlLine Self-Limiting (SL) Hose operates in all types of weather without requiring any temperature control or voltage limiting devices. It will maintain the minimum operating temperature desired by the customer in a sub-zero ambient, while not exceeding the design limits of the hose in a 125OF ambient. It is thus ideal for gas sampling where the sole aim is to prevent the temperature from dropping below the dew point. The “SL” Hose is available as a version of any one of the following high-heat hoses: Model 21 2, Model LP2i 2 (low-pressure), or Model 700 (for hazardous locations). Ail “SL” Hoses are supplied with V z ” thermal insulation and come in lengths from 35’ to 300’,depending on the operating voltage specifications.
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1730 First St., San Fernando, Ca. 91340 (213) 361.7185 CIRCLE 13 ON READER SERVICE CARD
1042
Environmental Science & Technology
Pesticides Dear Sir: Dr. Weber’s feature (The Pesticide Scorecard, €S& T August 1977, p 756) is very interesting, but we find ourselves in disagreement with some of the points he made. He classified pesticides into four groups based on their bioaccumulation factors, and continued to say that pesticides which have factors of 8000 or above are not excreted or metabolized to an appreciable extent. We find, based on certain references, and our own experience, that the accumulation of the DDT group 0: compounds (DDT-R) is best described as an equilibrium process in freshwater mussels. Bedford, Roelefs, and Zabik (Limnol. Oceanogr., 13, 1968) studied the accumulation of DDT-R by Anodonfa grandis and Lampsilis siliquoideae in the Red Cedar River. Their data indicate that the concentrations of these compounds are variable with the concentrations in the water of the river. More importantly, we find that a decrease in the concentration of DDT-R in the water is followed by a decrease in the concentration of DDT-R in the mussels. Fikes and Tubb (Proceedings of a Symposium on Rare and Endangered Mollusks, 1971) reported the accumulation of Dieldrin by Amblema plicata in an aquarium study. Their results appear to confirm Dr. Weber’s conclusions regarding pesticides having accumulation factors of less than 8000, i.e., that they are metabolized or excreted. The description of the process is somewhat open to question, but this question should be resolved soon, by certain work that is in process in our laboratories. Lastly, Dr. Weber reported that fish and oysters appear not to accumulate organophosphorus pesticides. The work of Miller, Zuckermann, and Charig (Trans. Am. Fish. Soc., 95) reports the accumulation of Parathion and Dizainon by the fish Fundulus heroditus L., and by the mussel Elliptio complanatus Solander. Our own experiences tend to confirm that these compounds and several others, including Malathion, can be accumulated by fish and mussels and subsequently detected unchanged. We feel, on the basis of the results reported in the literature cited, and on the basis of our own experiences, that Dr. Weber’s article, although it is informative, does not reveal the entire “Pesticide Scorecard.” Obviously, different species will accumulate pesticides with varying degrees of efficiency. We believe that this is an extremely important and oftenoverlooked aspect of the chemistry of pesticide residues that should again be brought to the attention of the readers of € S T . The information presently available on the bio-accumulation of pesticides by
freshwater fauna would seem to indicate that no general statement should be made about the compounds or the animals in this context, and we find our experiences in complete agreement with this statement. Charles M. Earnest S.Michael McCown Northeast Louisiana University Monroe, La. 7 1 2 0 3
Scrubbers Dear Sir: The brief article, “Removing SO2 in Heating Plant Boilers” (€S&T, July 1977, p 645), is so superficial and lacking in substantive technical details that unwarranted conclusions might be drawn from it. The Bahco scrubber system at Rickenbacker Air Force Base is acknowledged to have “drawbacks,” but only one-disposal of the sludge byproduct-is mentioned. What are the others? Some information on the installation can be obtained from “Summary Report-Flue Gas Desulfurization Systems-November-December 1976,” prepared by PEDCo-Environmental for the Environmental Protection Agency: It is installed on a small (20-megawatt equivalent) plant; capital cost was $110 per kilowatt in 1976 dollars; reportedly, it is operated in the “open-loop’’ mode, requiring 2.5 gpm makeup water; particulate collection efficiency is given as 99 % and SO2 removal as 85-90%; electrical and mechanical problems, as well as sedimentation buildup in the scrubber vessel, are reported. No information is given on operating costs, and no “availability,” “operability,” “reliability,” or “utilization” figures are reported. Since the Environmental Protection Agency reportedly “keeps close tabs on the operation” of the Rickenbacker scrubber, one would hope that EPA or the Air Force would publish an indepth report of the installation. Based on knowledge of other scrubbers, I doubt that everything is as rosy as your article seems to convey. William H. Megonnell National Association of Electric Companies Washington, D.C. 20036 Drinking water, correction Dear Sir: I would like to correct a mistake in the article by Angino, Wixson, and Smith that appeared on page 660 of the July 1977 issue of Environmental Science & Technulogy. Table 1 has two mislabled columns-the first and third. The units should read micrograms per liter instead of milligrams per liter. The mistake is ours. On earlier drafts the proper units were used (the Greek letter mu for micro). As is easily done this was later typed as an m, and so we have mg/L instead of pg/L. We missed this in proof-reading it. Ernest E. Anglno The University of Kansas Lawrence, Kans. 66044
