[atmos.pH.eric] threats

Since the Clean Water Act of 1970 and its following amendments, industrial and municipal discharges along the Delaware River have been dramatic reduced, and regions of special protection have shown biotic improvement. With point-sources of pollution at focus, we cannot neglect the not-so-locatable sources of ecological toxins. The Delaware Watershed faces non-point pollution from all regions of development, from urban to rural; pollutants such as lead or mercury deposits, accumulated from urban runoff, enter the river and mingle with other toxic wastes such as sewage discharge, or DDT and other agricultural pesticides. Besides runoff sources, one should also consider the effects from airborne pollutants, as stated by the IPCC, most of the ecological effects on freshwater systems depend on "hydrological responses to climatic change" (IPCC).
This climatic change is not only applied to a large scale such as global warming, but regional changes due to alterations in natural landscapes. It is commonly noted that urban development is a significant contributor of environmental pollution and as displayed on the map below, the result of this contrbution is very visible.

A major non-point contributor to the Delaware River Basin is acid rain, which is the result of atmospheric accumulation of harmful airborne pollutants from urban and industrial smog. Acid rain is usually associated with highly urbanized regions, and the northern headwaters of the Delaware Basin lies downwind of New York City, as well being among influential boundaries of other densely populated cities along the river borders such as Stroudsburg, Easton, Trenton, Philadelphia, and Wilmington.
The ecological threat begins when the chemical concoction begins its decent to the Earth's surface as precipitation. Like a sort of reverse atmospheric acupuncture, each droplet of contaminated rain delivers a multitude of toxins to be leached into the freshwater systems.
Rocky mountainous terrains such as the Catskills, from which the Delaware River draws it's headwaters, can prove to be as impervious as an urban city street, and high periods of precipitation can inundate the biotic communities with PCBs, mercury, dioxin, DDT and other wastes. This airborne pollutant is practically unavoidable. Policies such as the Clean Air Act, have helped lessen it impact, but the release of inorganic pollutants into the atmosphere is a continuing effect development.

To think that the Delaware River Basin faces such a continuing harmful threat, one would assume that the aquatic life would have been entirely eradicated by now, however biotic communities continue to thrive in these conditions. Shown on the left is a chart common to most biology textbooks. Various species of fish, more notably the Rainbow and Brook trout, thrive in these mildly acidic waters, but still can only thrive within a small range pH, a sensitivity common to most aquatic organisms.

A successful freshwater ecosystem is able to maintain sustainability of water conditions with the presence of a vegetative buffer, refered to as the riparian zone.

Plant life within this riparian boundary create a botanical bio-filter, which strain the influx of harmful chemicals, interrupting their entrance into our water systems in such heavy periods of inundation, but rather in a slow release in order to maintain suitable biotic living conditions for aquatic organisms. The importance of this environmental symbiosis between forest regions and river quality was demonstrated in a USGS assessment, which analyzed the effects of 'chronic episodic acidification' periods within the Catskill Moutains.

During the spring and fall seasons of 1989, the USGS conducted an analysis of fish mortality in relation to heavy acidic rain innundation. Juvenile brook trout were subjected to various acidic magnitiudes in varying increments, mimicking the upstream buffering conditions of the upstream Delaware River.
Although the climatic conditions of the Catskill experiences both extremes in summer and winter, precipitaiton is high year-round. There is a vicious cycle of pollutants interrelating through the atmospheric and hydrologic systems of the mountain region.
The degree of fish mortality was positively related to the riparian buffer zones which surrounded the Delaware River. The condition of a poorly buffered river under an acidic precipitation episode proved to be 100% deadly to fish communities.
The assessment implied that indirect environmental effects maybe be more disastrous to biotic communities than direct sources, and recognized the specific chemical culprits associated with the fish mortality(in order of importance), 1. inorganic monomeric aluminum, 2. dissolved carbon, 3. calcium, and 4. chloride.
Further examinations showed that the inorganic Aluminum concencrations, alone, could account for 76-85% of the variability within brook trout mortality(1). The effects of the acidic episodes among the rivers with a more densely vegetative riparian buffering zones yielded shorter durations and lower magnitudes of the acidification process(1).
The results of this assessment not only identified the specific airborne chemicals that are environmentally harmful, but also clearly demonstrates the importance of a preserved vegetated buffer zone along the river banks. Although the vast forested regions of the upper Delaware River is under constant threat of acidic rain, the densely forested river booundary are a necessity at maintaining the river's biotic conditions.
The isopleth map below represents the average annual pH of atmospheric precipitation. The highly urbanized northern east coast of our country has a visibly different influences to the quality of our waters compared to the rest of the country. The threat of non-point pollution is significant perhaps for its broad stretch and silent omniscience that is a part of all forms of human development, patiently wavering above our heads in the disguise of a beautiful cloud-filled sky.

1.) Effects of Forest Harvesting on Ecosystem Health in the Headwaters of the New York City Water Supply, Catskill Mountains, New York

By Michael R. McHale, Peter S. Murdoch, Douglas A. Burns, and Barry P. Baldigo


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