m
EDITORIAL Phosphate here, phosphate there.
..
Most of us have felt a sense of frustration over public environmental debates in which a clearly correct and effective course of action is not obvious. When this is the case, scientists conclude that more research is needed, and more enlightened members of the public conclude, properly, that no one h& the answers. These conclusions, however, do not prevent municipalities and state and federal agencies from acting-public and political processes being what they are. The frustration is particularly intense when relatively old and heavily researched issues fall into this trap, as is the case with eutrophication and public consideration of the favorite political control option of banning phosphates in detergents. Not many environmental issues have received more scientific thought and research investment than eutrophication. The currently accepted definition is that eutrophication is a process of nutrient enrichment in water bodies that can be accelerated by natural or synthetic means. Even the most respected limnological experts, however, have disagreed over whether the amount of algae present should be included in the definition. While the scientific community has been studying the complex chemical and ecological processes involved, the public has learned that eutrophication can mean unsightly algal blooms, the presence of unpleasant odors, and a tendency to stain and, perhaps, to kill fish. Eutrophic waters can exist without unsightly or noxious conditions where productivity is limited by nonnutrient factors. More than one factor can control the growth of aquatic plants, although much of the early research base was established on relatively pure northcentral lakes sensitive to as little as 10 pglL of total phosphorus. In southeastern waters, natural phosphorus levels are higher (40-70 pg/L) and can exceed 100 pg/L as a result of rainstorm-induced erosion. Much of this phosphorus load is particulate and is removed by natural assimilative processes as streams cut new channels, depositing alluvial soil on flood plains, and as suspended matter settles to the bottom of lakes. High turbidity values associated with this particulate
flux may make algal growth in such waters light limited, but other limiting factors may be equally important. In all such cases control of phosphorus is less directly associated with reductions of nuisance algal growth. What is known scientifically suggests that natural variations in the complex interrelations among nutrient levels, light availability, and plant growth are so substantial that single control measures (such as phosphate bans) are likely to have extremely variable results if applied over large areas. Indeed, there are surface waters that benefit from phosphorus reductions, such as Lake Washington in Seattle, but phosphorus bans are not a panacea nationally, regionally, or perhaps even on a statewide level. For one thing, detergents are not the largest source of phosphates in domestic sewage, and in any case it may well be more economical to remove them by sewage treatment than it is to require the use of more expensive soap. At least this is EPA’s apparent message in deciding not to pursue national efforts to ban phosphates in detergent. Ban advocates, who often speak as though the entire environmental research community were united behind them, present cost data suggesting the reverse. Which data are more credible? We don’t have much national experience with either approach and “actual” cost data are likely site specific. Another disadvantage of phosphate bans over large areas as a mandatory single solution to eutrophication is the unwitting support it lends to the efforts of community officials to avoid expanded investments in sewage treatment facilities. This is extremely counterproductive in the Southeast, where municipal sewage effluents are a major contaminant of surface water and where phosphate reductions that result from bans may produce no noticeable improvement in water quality.
0013-936X/85/0919-0467$01.50/0 0 1985 American Chemical Society
n
Environ. Sci. Technol., Vol. 19, No. 6,1985 467
