pond of a paper mill were the levels comparable with the average value for the LaHave River. Few data exist for the quantitative determination of mercury in industrial settling ponds. However, it appears that the relatively low mercury level in the water from the paper mill settling pond may be due to adsorption on suspended sediment. The levels for a fertilizer plant, paper mill, and smelting plant effluents were an average of 43 times higher than the dissolved level for the LaHave River. The discharge of the chlor-alkali plant was up to 28,500 times higher than the LaHave River. The nature of discharged particulate matter from the industrial sites varied with the type of manufacture or processing and in no case could the inorganic content of the particulate matter be considered similar to natural suspended sediments. The amount of mercury found in the particulate matter at all sites was less than the maximum level found in the particulate matter from the LaHave. This observation was especially noteworthy at the chlor-alkali plant. Here, although the concentration of dissolved mercury was up to 28,500 times higher than the average for the LaHave River, the particulate mercury was only slightly higher than the average for the LaHave. Bottom sediments collected from areas up to 800 meters from these effluent outlets contained mercury concentrations higher
than those from the LaHave but are still considerably lower than average suspended particulate matter. Acknowledgment The authors wish to thank J. M. Bewers, D. Loring, and A. Walton of the Bedford Institute for reviewing the manuscript and making helpful suggestions in the manner of presentation of the data. Literature Cited “Analytical Methods for Atomic Absorption Spectrophotometry,” Perkin-Elmer Corp., Norwalk, Conn., 1971. Bligh, E. G., Fisheries Research Board of Canada, Manuscript Report Series No. 1088,1970. Buckley, D. E., Atlantic Oceanographic Laboratory, Cruise Report 70-016,1970. Flanagan, F. J., Geochim. Cosmochim. Acta, 33,100 (1969). Hatch, W. R., Ott, W. L., Anal. Chem., 40,2085-7 (1968). Jensen, S., Jernelove, A., Nature, 223, 753-4 (1969). Jonasson, I. R., Geological Survey of Canada, Paper 70-57, 1970. Kennedy, V. C., Geological Survey Prof. Paper 433-D, 1965. Klein, D. H., Goldberg, E. D., ENVIRON. SCI. TECHNOL., 4, 765-8 (1970). Received for review May 4, 1971. Accepted August 31, 1971.
COM MU N ICAT ION
Solubilization of Lead in Lake and Reservoir Sediments by NTA Charles D. Gregorl Leonia High School, Leonia, N.J. 07605
The proposed replacement of phosphate by nitrilotriacetic acid (NTA)in detergent formulations could result in the latter compound finding its way into public water supplies. Reservoir bottom sediments frequently contain insoluble lead deposited from automobile exhausts. The possibility of NTA solubilizing significant amounts of lead into drinking water was investigated by shaking suburban reservoir and lake sediments with water containing NTA. A concentration of soluble lead 12 times the maximum permitted level was observed in certain experiments.
S
ince nitrilotriacetic acid (NTA)has been under consideration as a replacement for phosphates in laundry detergents, and hence could be used in amounts ranging from 200-500 million lb/year, some of the possible effects of this compound on the environment have received attention. Significant amounts of this compound could, under certain circumstances, be released into water supply systems. Our conPresent address : Carleton College, Northfield, Minn. 55057 278 Environmental Science & Technology
cern in this study was the possible solubilization of reservoir lead by NTA. NTA is a well-known complexing agent, having first been characterized by Schwarzenbach et al. (1945). Its biodegradation in sewage treatment was studied by Swisher et al. (1967), who added NTA at different dosages to laboratory-activated sludge units. They concluded that there was substantially complete biodegradation in a short time, since NTA was reduced from initial levels of a few hundred ppm down to about IO of that in periods of time ranging from 5 to 10 hr. The analysis for NTA was through the formation of its complex with an excess of ferric ions, precipitation of unchelated iron, and a colorimetric Fe determination after filtration. Accordingly, the direct determination of NTA itself was not employed in these studies. In many parts of the United States, particularly in suburban areas, there is considerable automobile traffic near and directly around main water reservoirs. An appreciable lead fallout from traffic is deposited in the soil adjacent to the highways in various insoluble forms, largely as carbonates and salts of soil anions (Motto et al., 1970; Daines et al., 1970). Because these compounds are both insoluble and heavy, they settle out to the bottom of bodies of water. A detectable amount of lead
Table I. Solubilization of Lead by NTA Lead concn. Duma Mamaroneck Reservoir Crystal Lake Rt. 80 bottom shoulder bottom Total Pb 36 120 160 After 1 hr O ppm N T A ~
