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concentrations in ground-water discharge, the life in the border region. A computerized
USGS Mineral Resources Data System. Each
site record provides the name of the site, its
Peter McMahon location, the commodity mined, the geology has over 10 years of experience as a USGS
of the site, a description of the workings and
opment, and production at the site. The data-
minerals and materials. Analysis of this infor-
mation indicates that a wide variety of nonis a research hydrologist whose recent work has
fuel mineral commodities are present in the focused on applications of chemical and isotopic
border region. Mineral resources and minmethods for determining ground-water residence
eral-related issues in the border region that
will affect the economies of the United States
Mineral-site data are
available from the Miner
improving water quality, isolating waste, has worked as a USGS hydrologist in Colorado for
als Information Offices of and mitigating environmental hazards. the last 10 years. His areas of interest include
the U.S. Geological SurImportant resources in the border region surface-water quality, water use, and the use of
vey in digital form or as
include diatomite and zeolites for waste geographic information systems in water studies.
listings, tables, and plots treatment, clays for sealing waste dumps,
and are summarized in and limestone for removing sulfur from
Circular 1098. emissions produced in coal- or oil-fired
power stations. Mineral occurrences and Environmental and
abandoned mine sites may be sources for Resource Studies
acid-mine drainage and elevated levels of
toxic trace elements in soils and ground in the U.S.-Mexico
Mineral materials such as limestone, sand,
gravel, and gypsum are widely used in the
especially in rapidly growing urban areas.
Trade Agreement (NAFTA) reinforces cent of the world's copper as well as other the need for geoscience data and information metallic commodities, including zinc, lead, in the U.S.-Mexico border region. NAFTA silver, and gold. Metals used in alloy man Area defined as the U.S.-Mexico will accelerate urban, agricultural, and indus ufacture, such as aluminum, cobalt, nickel, border region. trial growth and trade along the border. Such growth and the current and anticipated potential for increased effects on the environment necessitate development of a large,
ARIZONA NEW MEXICO TEXAS coherent geoscience database. Such a data
Santa Fe base is vital to both nations in many disci
Los Angeles Bagdad
Albuquerqu plines, including land-use management,
UNITED STATES urban planning, civil engineering, explora
Nogales tion geology, environmental sciences, envi
Nogales ronmental regulation, resource management,
Hermosillo MEXICO waste treatment, and industrial mineral sup
Chatvana ply. The U.S. Geological Survey (USGS) has
Mexico begun several cooperative projects to compile
Data on the distribution and characteris-
za to the dis
- cong Dutflows trate in
outh ch less
San Diegde: Mexicana
on the natural distribution of potentially toxic systems to be compared with anthropogenic activities such as mining.
The establishment and continued construction of a geoscience database, including elements of geology, geochemistry, geophysics, and mineral sites, will allow for effective implementation of NAFTA. The geoscience database forms part of the necessary framework for development of land- and ecosystem-management plans and increased infrastructure, industry, and agriculture in the border region.
For more information on USGS studies in the U.S.-Mexico border region, contact Norman ) Page at:
Telephone: (602) 670–5580
Norman J Page is Scientist-in-Charge of the USGS Center for Inter-American Mineral Resource Investigations,
which conducts cooperative mineral resource investigations, technology transfer and training,
mineral information exchange, and research.
Pesticides in the Atmosphere
and iron, are produced in relatively small
Another important layer of geoscience information for the U.S.-Mexico border region is a geologic map in digital format. The border region extends across six different geologic provinces from east to west-from the Gulf of Mexico Coastal Plain, across ancient rocks of the stable continental platform and remnants of past volcanic eruptions, to regions where the Earth's crust has been stretched and areas where rocks from ancient ocean environments have been stuck on to the continent. This complex geology complicates the task of producing a coherent map. Geologic maps of the States of Arizona and New Mexico are now available from the USGS in digital format at a scale of 1:1,000,000. The geology of the border region of Texas is being digitized at a scale of 1:500,000, as is the geology of California.
Other current investigations pertinent to the border region include evaluating hydrologic basins that contain aquifers along the border, establishing baseline geochemical information in the larger drainage areas, and examining the dispersion of metals and the natural availability of potentially toxic substances in the region. The San Pedro River Valley in southern Arizona and northern Sonora, Mexico, is composed of several subbasins. A multidisciplinary study to determine the three-dimensional shapes of these subbasins, to describe the relations among the subbasins, and to assess the character and distribution of the sediments filling the basins is underway
This project is an essential first step in assessing the potential for ground-water contamination in subbasin aquifers. Existing geochemical databases are being analyzed and evaluated to provide a geochemical baseline. Some of the samples are being reanalyzed for elements particularly important in identifying potential sites of pollution. These data will also provide a regional hydrogeochemical framework for a large part of southern Arizona and for investigations related to the USGS National Water-Quality Assessment Program in central and southern Arizona. Several investigations are being conducted on the dispersion of metals from mined and unmined ore deposits. Such data will allow the effect of natural mineralization
ne of the first issues to be addressed by
(NAWQA) Program National Synthesis is the presence of pesticides in the environment. The goal of the National Synthesis is to use existing data and new data collected during NAWQA studies to assess the status, trends, and cause-and-effect relations for the Nation's highest priority national and regional waterquality issues. About 1.1 billion pounds of pesticides are used each year in the United States to control many different types of weeds, insects, and other pests in a variety of agricultural and nonagricultural settings.
Total agricultural use and the number of different chemicals applied to crops have more than tripled since the early 1960's. Increased use has resulted in increased crop production, lower maintenance costs, and control of public health hazards, but concerns about the potential adverse effects of pesticides on the environment and human health also have grown steadily. The Pesticide National Synthesis begins with detailed reviews of existing information on pesticides in the hydrologic system, including ground and surface waters and the atmosphere. Results for the atmosphere are summarized below.
Pesticides have been recognized as potential atmospheric pollutants since the
1940's. Early in the history of agricultural pesticide use, off-target drift of applied pesticides was a concern. Long-range movement of pesticides was thought to be minimal, if any, because of their physical and chemical properties (low volatility and low solubility in water). The detection of DDT and other organochlorine compounds in Arctic and Antarctic snow, ice, fish, and mammals changed this notion. The atmosphere is now recognized as a major pathway by which pesticides can be transported and deposited in areas sometimes far removed from their sources.
which analyses have been made have been detected in at least one atmospheric matrix. Compared with the hundreds of pesticides that have been and are being used, the number and variety of pesticides analyzed from and detected in air and rain are few. These figures do not mean, however, that the majority of pesticides used are not present in the atmosphere. There are several reasons why a particular pesticide has not been found-for example, low use, short atmospheric residence time considering deposition and transformation), the timing of the sampling relative to the timing of use, the predominant atmospheric phase in which it will accumulate relative to the phase being sampled, and, perhaps most important, whether it has been analyzed for in the atmosphere.
High Atmospheric Concentrations of Pesticides Show Seasonal Trends
Atrazine use in 1988 through the study area (A) and the precipitation-weighted concentrations of atrazine throughout the Midwestern and Northeastern United States from mid-April through mid-July 1990 (B) and 1991 (9).
organochlorine insecticides have been detected in the atmosphere of every State in which they were sought. Organophosphorous insecticides also have been heavily used for decades and are still in high use. As a class, they are not as environmentally persistent as the organochlorine compounds, but they have been detected in most States in which analyses have been made. Triazine herbicides have been in use since the 1960's, but studies in which these compounds are analyzed from the atmosphere did not begin until the late 1970's, when atrazine was found in rain in Maryland. Subsequent studies have detected high levels of triazine herbicides in rain in major corn-producing areas, such as the Midwestern United States. Acetanilide herbicides are frequently used in conjunction with triazine herbicides. Although they are not as environmentally stable as the triazine herbicides, they have been detected in rain at equivalent and even higher concentrations. Many other types of herbicides are used in agriculture, and many of them have been detected in the
Pesticide occurrences in air, rain, and fog
often show seasonal trends; the highest concentrations correspond to local use and planting seasons. In a recent U.S. Geological Survey (USGS) study, samples of rain collected throughout the Midwestern and Northeastern United States were analyzed for a variety of triazine and acetanilide herbicides used in corn and soybean production. The analyses show that the highest concentrations occurred where corn was most intensively grown and corresponded to the spring and summer planting seasons. Observed concentrations for August through March were considerably less. There is a very detailed and strong relation, both spatially and temporally, between atrazine use and concentrations in rain. Pesticides also have been detected at low levels during periods before and after the high-use seasons. These off-season occurrences could be the result of the
The potential contribution and relative
Land their deposition into surface waters volatilization and wind erosion of previously exposures than humans are, and the U.S. applied material or long-range transport from Environmental Protection Agency and the areas where the planting growing season National Academy of Sciences have set maxistarted earlier. The more persistent pesticides, mum levels of several pesticides for the prosuch as organochlorine insecticides, have
tection of aquatic life. The majority of been detected in the atmosphere at low levels
pesticides in use today, however, do not have throughout the year even though they are no
such established levels. Pesticide concentralonger used in the United States. Another
tions in rain usually are one order of magni-
tude or more below the human health
standards or maximum contaminant levels
for water. There have been several instances, rine insecticides that have been banned in the though, where the concentrations of pestiUnited States are still being used in large cides in rain and fog have exceeded the maxiquantities.
mum contaminant level values for aquatic life
in or near agricultural areas.
Improved Databases Are
The extent of pesticides in our atmosphere importance of pesticides from the atmodanes sphere to a body of surface water depend on
are not well known because there is no conas been pesticide levels in atmospheric deposition
sistent nationwide monitoring of pesticides and on how much of the water budget is and their transformation products in atmoderived from surface runoff and direct precip spheric deposition. Existing data on pestiitation. However, very little research has been cides in the atmosphere show that pesticides done on the deposition of pesticides into sur have been found in air, rain, snow, or fog face waters. The most clearly documented throughout the Nation and that most pestieffects of atmospheric pesticides on human
cides studied have been found. The potential bal health and aquatic life, even at the low levels
significance to water quality has not been commonly found in air, rain, snow, and fog,
extensively studied except in the Great Lakes are related to long-lived, environmentally sta
area. The effects on the health of humans and ble organochlorine insecticides that concenfog trate in organisms through biomagnification
aquatic organisms brought about by chronic (food chain accumulation), bioconcentration
exposure to low levels of a wide variety of (environment organism partitioning), or
insecticides, herbicides, and fungicides also both. An example is the organochlorine
are not well known. Water-quality investigainsecticide toxaphene in the Great Lakes tions conducted as part of the NAWQA Proregion. Toxaphene, which is carcinogenic to gram will consider atmospheric deposition as laboratory animals, was never used to any a potentially important source of pesticides, great extent in this area but has been detected particularly during high-use seasons in highin the air, rain, water, sediments, and fish.
use areas, but generally will not conduct The most probable source for this contamina extensive sampling of atmospheric media. tion is long-range atmospheric transport from
The NAWQA Program will work with other the high-use areas in the Southern United
agencies and programs to encourage the States and Mexico.
development of more comprehensive Determining the environmental signifi
monitoring and the study of atmospheric
Michael S. Majewski
is a research chemist with the
Pesticide National Synthesis group of the are often more sensitive to low-level pesticide National Water-Quality Assessment Program.
est od ical
For more information on pesticides in the
Telephone: (916) 979–2609, ext. 345