TECHNIQUES FOR DETECTING TRENDS IN LAKE WATER QUALITY1

ABSTRACT: With the advent of standards and criteria for water quality variables, there has been an increasing concern about the changes of these variables over time. Thus, sound statistical methods for determining the presence or absence of trends are needed. A Trend Detection Method is presented that provides: 1) Hypothesis Formulation - statement of the problem to be tested, 2) Data Preparation - selection of water quality variable and data, 3) Data Analysis - exploratory data analysis techniques, and 4) Statistical Tests - tests for detecting trends. The method is utilized in a stepwise fashion and is presented in a nonstatistical manner to allow use by those not well versed in statistical theory. While the emphasis herein is on lakes, the method may be adopted easily to other water bodies.     

Effects of stream channelization on exports of nitrogen and phosphorus from north Carolina coastal plain watersheds

Nitrogen and phosphorus exports from channelizedstream watersheds were elevated over those from nearby natural swamp-stream watersheds. Nitrate exports were significantly greater from channelized-stream watersheds, and higher exports were attributed to faster groundwater drawdown, continual streamflow, and transformation of former floodplain to croplands following channelization. Exports of total organic nitrogen and total nitrogen were also significantly greater from channelized-stream watersheds. Differences in the exports of ammonium, filterable reactive phosphorus, and filterable unreactive phosphorus between the two watershed types were not detectable. Particulate phosphorus exports were significantly higher from channelized-stream watersheds, presumably because of greater erosion potential of nearby croplands and steep channel banks in the altered watersheds. The presence of nonpoint sources of pollution increased watershed exports of nutrients regardless of stream morphology. Examination of nutrient budgets for a portion of swamp floodplain at the base of one natural-stream watershed revealed that changes in local groundwater hydrology and stream morphology associated with channelization appeared to have greater effect on nutrient exports than simply the loss of bordering forested floodplain.     

Characterization of physicochemical properties of beryllium aerosols associated with prevalence of chronic beryllium disease

Little is known about the physicochemical properties of beryllium aerosols associated with increased risk of beryllium sensitization and chronic beryllium disease (CBD). Such information is needed to evaluate whether airborne mass of beryllium is the appropriate metric of exposure or alternatively to provide a scientific basis for using information on particle size, surface area, and chemistry to support an improved exposure limit based on bioavailability through the inhalation and dermal routes of exposure. Thus, we used a suite of analytical techniques to characterize aerodynamically size-fractionated beryllium particles and powders that have been associated in epidemiological studies with higher prevalence of CBD. Aerosol particles were sampled from the ventilation systems of production lines for powders of beryllium metal and beryllium oxide and for ingots of copper-beryllium alloy. End product powders from the metal and oxide production lines were also collected.Particles released during production of beryllium metal were found to be complex, having heterogeneous composition, including reactive species such as fluorine. Powders from beryllium metal production were of high purity with only a minor component of beryllium oxide. Both particles and powders from oxide production were high-purity oxide. Particles released during production of copper-beryllium alloy were heterogeneous, being predominantly copper oxides. Thus, all particles and powders contain at least some beryllium in the form of beryllium oxide.These data justify efforts to thoroughly characterize beryllium aerosol properties when performing exposure assessments. The data also suggest that differences in particle chemical composition, size, number, and surface area may influence bioavailability of beryllium and contribute to risk of CBD. However, a scientific basis does not yet exist to replace mass as the current metric of exposure.     

Past and present water-quality conditions in the Hanford Reach,Columbia River

Twelve water quality variables from upstream and downstream locations in the Hanford Reach of the mainstem Columbia River, southcentral Washington, were compared statistically for the two time periods 1951 to 1953 and 1986 to 1988. During the 1951 to 1953 period, beta radioactivity and, most likely, water temperatures in the Hanford Reach were significantly higher downstream than upstream, while dissolved oxygen and sulfate were significantly lower. The increased beta radioactivity and temperature downstream were due to the discharge of cooling water from five single-purpose production reactors then operating on the Hanford Site. The last production reactor closed in January 1971. During the 1986 to 1988 period, beta radioactivity and water temperatures were similar upstream and downstream, but nitrate nitrogen had become significantly higher downstream. Comparison of 1951 to 1953 with 1986 to 1988 showed, as expected, that beta radioactivity was much lower today, at essentially background levels. Phosphate in the Hanford Reach had decreased significantly over the 35 year interval, while biochemical oxygen demand, dissolved oxygen, and nitrate nitrogen had increased. These changes, while detectable statistically, were relatively small. Today, the quality of water in the Hanford Reach remains well within Washington State standards for Class A waters. Occasional low pH values, which appear to orginate upriver, violate these standards.     

Organochlorine residues in New York waterfowl harvested by hunters in 1983–1984

Thirteen organochlorine compounds were detected in fat and breast muscle tissues of Canada goose and five species of ducks that were shot by sportsman in New York. Residues of DDE and PCB occurred most frequently and were positively identified along with DDT, heptachlor epoxide, trans-nonachlor, and hexachlorobenzene. Compounds that were detected but not positively confirmed by mass spectrometry were dieldrin, mirex, heptachlor, chlordane, oxychlordane, and endrin. Wood duck (Aix sponsa) and Canada goose (Branta canadensis) had significantly lower levels of DDE and PCB than black duck (Anas rubripes), mallard (Anas platyrhynchos), scaup (Athya sp.), and bufflehead (Bucephala albeola). Birds collected from Long Island and the Hudson River-Lake Champlain corridor carried highest concentrations.     

Lead in hawks,falcons and owls downstream from a mining site on the Coeur d'Alene River,Idaho

Mining and smelting at Kellogg-Smelterville, Idaho, resulted in high concentrations of lead in Coeur d'Alene (CDA) River sediments and the floodplain downstream, where American Kestrels (Falco sparverius), Northern Harriers (Circus cyaneus), Red-tailed Hawks (Buteo jamaicensis), Great Horned Owls (Bubo virginianus), and Western Screech-owls (Otus kennicotti) nested. Nestling American Kestrels contained significantly higher (P=0.0012) blood lead concentrations along the CDA River (0.24 µg/g, wet wt) than the nearby reference area (0.087 µg/g). A 35% inhibition of blood -aminolevulinic acid dehydratase (ALAD) in nestling Northern Harriers (P=0.0001), 55% in nestling American Kestrels (P=0.0001) and 81% in adult American Kestrels (P=0.0004) provided additional evidence of lead exposure in the CDA River population. In nestling American Kestrels and Northern Harriers, ALAD activity was negatively correlated with lead in blood. An earlier report on Ospreys (Pandion haliaetus) showed slightly less inhibition of ALAD than in American Kestrels, but no significant reduction in hemoglobin or hematocrit and no negative influence on production rates. The adult and nestling American Kestrels along the CDA River contained about twice as much blood lead as Ospreys during the same years (adult 0.46 vs. 0.20 µg/g, and nestling 0.24 vs. 0.09 µg/g), but adults showed a 7.5% reduction in hemoglobin (P=0.0356) and nestlings an 8.2% reduction in hemoglobin (P=0.0353) and a 5.8% reduction in hematocrit (P=0.0482). We did not observe raptor deaths related to lead, and although the production rate for American Kestrels was slightly lower along the CDA River, we found no significant negative relation between productivity and lead. Limited data on the other raptors provide evidence of exposure to lead along the CDA River. Several traits of raptors apparently reduce their potential for accumulating critical levels of lead which is primarily stored in bones of prey species.The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged.     

Analysis of the Threshold and Expected Coverage Approaches to the Probabilistic Reserve Site Selection Problem

Two approaches to formulating the reserve site selection problem when species occurrence data is probabilistic were solved for terrestrial vertebrates in a small set of potential reserve sites in Oregon. The expected coverage approach, which maximizes the sum of the occurrence probabilities, yielded solutions that covered more species on average in Monte Carlo simulations than the threshold approach, which maximizes the number of species for which the occurrence probability exceeds some threshold.