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Anne K. O’Brien

Publications and source records attributed to Anne K. O’Brien.

7 recordsLinked to original sources
USGS2010

Comparison of episodic acidification of Mid-Atlantic Upland and Coastal Plain streams

Episodic acidification was examined in five mid-Atlantic watersheds representing three physiographic provinces: Coastal Plain, Valley and Ridge, and Blue Ridge. Each of the watersheds receives a similar loading of atmospheric pollutants (SO 4 2− and NO 3 − ) and is underlain by different bedrock type. The purpose of this research was to quantify and compare the episodic variability in storm flow chemistry in Reedy Creek, Virginia (Coastal Plain), Mill Run and Shelter Run, Virginia (Valley and Ridge), and Fishing Creek Tributary and Hunting Creek, Maryland (Blue Ridge). Because episodic responses were similar from storm to storm in each of the watersheds, a representative storm from each watershed was discussed. Acidification, defined as the loss of acid-neutralizing capacity (ANC), was observed in all streams except Mill Run. Mill Run chemistry showed little episodic variability. During storms in the other streams, p H decreased while SO 4 2− , NO 3 − , and K + concentrations increased. Concentrations of Mg 2+ and Ca 2+ increased in Reedy Creek and Fishing Creek Tributary, but decreased in Shelter Run and Hunting Creek. Therefore the net effect of episodic changes on the acid-base status differed among the streams. In general, greater losses of ANC were observed during storms at Shelter Run and Hunting Creek, watersheds underlain by reactive bedrock (carbonate, metabasalt); comparatively smaller losses in ANC were observed at Reedy Creek and Fishing Creek Tributary, watersheds underlain by quartzites and unconsolidated quartz sands and cobbles. Increased SO 4 2− concentrations were most important during storms at Reedy Creek and Fishing Creek Tributary, but organic anions (inferred by anion deficit) were also a factor in causing the loss of ANC. Dilution of base cations was the most important factor in the loss of ANC at Shelter Run. Both increased sulfate and dilution of base flow were important in causing the episodic acidification at Hunting Creek. The role of SO 4 2− in contributing to episodic acidification in these watersheds is similar to that documented in studies conducted in other regions of the United States, Scandinavia, Canada, and the United Kingdom. The importance of SO 4 2− in mid-Atlantic United States streams contrasts with northeastern United States streams, in which increased NO 3 - derived from snowpack is more important in causing episodic acidification. Results support the importance of shallow subsurface processes in determining storm flow chemistry, regional climatic characteristics in determining the different sources of acidity during episodes, and the importance of bedrock geology in determining the amount of ANC loss.

Maryland, Virginia, West Virginia↗
USGS1999

Pesticides in streams in New Jersey and Long Island, New York, and relation to land use

Pesticide compounds were detected in all 50 water samples collected from streams in New Jersey and Long Island, New York, during June 9-18, 1997. Samples were analyzed for 47 compounds, of which 25 were detected. The number of pesticides detected at each site ranged from 1 to 14. The seven most frequently detected pesticides were atrazine (in 93 percent of samples), metolachlor (86 percent), prometon (84 percent), desethyl-atrazine (78 percent), simazine (78 percent), carbaryl (44 percent), and diazinon (44 percent). All pesticide concentrations were within both U.S. Environmental Protection Agency (USEPA) and State maximum contaminant levels (MCL?s) for drinking water and USEPA lifetime health advisory levels (HAL?s). Concentrations of dieldrin and methylazinphos at one or more sites, however, equaled or exceeded a Federal or State water-quality criterion for aquatic life. The pesticides detected in a stream were related to the land-use composition of the basin. Detection frequencies of 14 of the 25 pesticides detected were highest at agricultural sites; acetochlor, azinphos-methyl, carbofuran, and pebulate were detected only at agricultural sites. Seven compounds were detected most frequently at urban sites; trifluralin, dieldrin, napropamide, and benfluralin were detected only at urban sites. Four compounds were detected most frequently at sites draining areas of mixed land use. No pesticides were detected most frequently at sites draining forested areas. The median concentration and the detection frequency of a given pesticide always were highest in samples from sites in the same land-use category.The median concentrations of seven pesticides at the agricultural sites were at least twice as high as the median concentrations at sites in other land-use categories. The median concentrations of the seven compounds detected most frequently at urban sites were equal to or only slightly higher than the median concentrations at sites in other land-use categories. The median total-pesticide concentration was highest at agricultural sites (0.2 mg/L (micrograms per liter)) and lowest at forested sites (0.025 mg/L). Total-pesticide concentrations varied most at agricultural sites and least at forested sites. Total-pesticide concentration and number of pesticides detected at a site increased as the percentage of agricultural land in the basin increased and decreased as the percentage of undeveloped land increased. Only three of the seven most frequently detected compounds?atrazine, metolachlor, and carbaryl?are among the seven most heavily applied pesticides in New Jersey. This is because detection frequencies are the result of physical and chemical properties of the pesticide compounds as well as application rates. Water solubility and soil-adsorption coefficients appear to be the two physical properties of pesticides that most influence their presence in streams.

New Jersey, New York↗
USGS1997

Use of geochemical mass balance modelling to evaluate the role of weathering in determining stream chemistry in five mid-Atlantic watersheds on different lithologies

The importance of mineral weathering was assessed and compared for five mid-Atlantic watersheds receiving similar atmospheric inputs but underlain by differing bedrock. Annual solute mass balances and volume-weighted mean solute concentrations were calculated for each watershed for each year of record. In addition, primary and secondary mineralogy were determined for each of the watersheds through analysis of soil samples and thin sections using petrographic, scanning electron microscope, electron microprobe and X-ray diffraction techniques. Mineralogical data were also compiled from the literature. These data were input to NETPATH, a geochemical program that calculates the masses of minerals that react with precipitation to produce stream water chemistry. The feasibilities of the weathering scenarios calculated by NETPATH were evaluated based on relative abundances and reactivities of minerals in the watershed. In watersheds underlain by reactive bedrocks, weathering reactions explained the stream base cation loading. In the acid-sensitive watersheds on unreactive bedrock, calculated weathering scenarios were not consistent with the abundance of reactive minerals in the underlying bedrock, and alternative sources of base cations are discussed.

Hydrological Processes↗
USGS1997

Presence and distribution of trace elements in streambed sediments, New Jersey

The National Water Quality Assessment (NAWQA) Program, developed by the U.S. Geological Survey (USGS), was implemented in 1991 to (1) provide a nationally consistent description of the status of surface- and ground-water quality in systems that represent a large part of the Nation's water resources, (2) determine water-quality trends, and (3) determine relations between past and present water quality and land- and waste-management practices. Information collected and interpreted as part of NAWQA will add to the scientific basis for water-management decisions and policy formulation (Leahy and others, 1990).

New Jersey↗
USGS1997

Spatial variability of volatile organic compounds in streams on Long Island, New York, and in New Jersey

Volatile organic compounds (VOCs) are found in almost all natural and synthetic materials and are commonly used in fuels, fuel additives, solvents, perfumes, flavor additives, and deodorants. Potential health hazards and environmental degradation resulting from the widespread use of VOCs has prompted increasing concern among scientists, industry, and the general public.

New Jersey, New York↗