Sources of Nitrate in Ground Water in a Sewered Housing Development, Central Long Island, New York

Nitrate concentrations in ground water on Long Island, New York, have increased markedly in the last 30 years. A significant amount of this increase has been attributed to lawn and garden fertilizers in addition to cesspool and septic-tank discharges. The increase in nitrate concentration is of particular concern in the central and eastern part of the island, where ground water is the sole source of drinking water. Ground-water samples were collected from 14 wells screened near the water table in the sewered Twelve Pines housing development constructed in Medford, Suffolk County, in 1970. Samples were collected during 1972–79 and analyzed for total ammonium, organic nitrogen, and nitrate. Statistical analyses indicate that concentrations of nitrate-nitrogen in water from 10 of the wells increased significantly during 1972–79; those in water from the other four wells did not. Nitrogen loads were estimated to be 2,300 kg/yr from fertilizers, less than 80 kg/yr from irrigation water, 200 kg/yr from animals, and less than 670 kg/yr from precipitation. Leakage from sewers was considered negligible. Nitrate-nitrogen isotope ratios also suggest that the greatest source of nitrogen is from cultivation sources (either mineralized soil nitrogen or fertilizers) rather than human or animal wastes.     

A shear-mobile transform belt in the Precambrian Gondwanaland of Africa — South America

An Archaean-Lower Proterozoic mobile belt can be recognized in the West African — Brazilian — Southern African portions of Gondwanaland extending from the Kasila Group of Sierra Leone, through the Goias Belt of Central Brasil to the Namaqua Mobile Belt of Namibia (KGN). This belt is characterised by high shear strain deformation and high grade metamorphism and may represent a transform-shear mobile belt. Shear movement and displacement along the KGN during the Precambrian has affected the older cratons and controlled major secondary tensional and shear belts which are now recognized as younger Proterozoic mobile belts.

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Zusammenfassung In den westafrikanisch-brasilianischen und südafrikanischen Bereichen Gondwanalands lÄ\t sich ein archaischer — unterer protezoischer — mobiler Gürtel erkennen, der sich von der Kasila Group von Sierra Leone über den Goias Gürtel Zentral-Brasiliens bis zum Namaqua Mobile Belt von Namibia (KGN) erstreckt. Dieser Gürtel ist charakterisiert durch hohe Spannungsdeformation und hochgradige Metamorphose. Er könnte einen mobilen Gürtel mit Transformschub darstellen. Scherbewegung und Verstellung entlang der KGN wÄhrend des PrÄkambriums hatten die Älteren Kratone erfa\t und kontrollierten grö\ere sekundÄre Dehnungs- und Schergürtel, die heute als jüngere mobile Gürtel des Proterozoikums angesprochen werden.

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Résumé Une zone mobile d'âge archéen-protérozoÏque inférieur peut Être reconnue dans les parties du Gondwanaland de l'Afrique occidentale-Brésil-Afrique méridionale, depuis le Groupe de la Sierra Leone, en passant par la ceinture de Goia du Brésil central, jusqu'à la ceinture mobile de Namibie (KGN). Cette ceinture est caractérisée par une déformation cisaillante fortement prononcée et par un degré de métamorphisme élevé; elle peut représenter une ceinture mobile de faille transformante. Des mouvements de cisaillement et de déplacement de la KGN durant le Précambrien ont affecté les vieux cratons et ont conditionné les ceintures secondaires principales du point de vue de leur tension et de leur cisaillement, lesquelles sont maintenant reconnues comme des ceintures mobiles du ProtérozoÏque récent.

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Implications of an anti-glitch in AXP/SGR

The recently observed anti-glitch of AXP 1E 2259+586 may be explained as the consequence of sudden accretion of retrograde matter. AXP/SGR are explained as single neutron stars accompanied by fallback matter from their natal supernovæ, including rocky or metallic planetesimals. The upper bounds on a glitch or anti-glitch in the giant outburst of SGR 1806-20 pose a problem for any model.     

The origin of young mare basalts inferred from lunar meteorites Northwest Africa 4734, 032, and LaPaz Icefield 02205

Northwest Africa (NWA) 4734 is an unbrecciated basaltic lunar meteorite that is nearly identical in chemical composition to basaltic lunar meteorites NWA 032 and LaPaz Icefield (LAP) 02205. We have conducted a geochemical, petrologic, mineralogic, and Sm‐Nd, Rb‐Sr, and Ar‐Ar isotopic study of these meteorites to constrain their petrologic relationships and the origin of young mare basalts. NWA 4734 is a low‐Ti mare basalt with a low Mg* (36.5) and elevated abundances of incompatible trace elements (e.g., 2.00 ppm Th). The Sm‐Nd isotope system dates NWA 4734 with an isochron age of 3024 ± 27 Ma, an initial ε_Nd of +0.88 ± 0.20, and a source region ¹⁴⁷Sm/¹⁴⁴Nd of 0.201 ± 0.001. The crystallization age of NWA 4734 is concordant with those of LAP 02205 and NWA 032. NWA 4734 and LAP 02205 have very similar bulk compositions, mineral compositions, textures, and ages. Their source region ¹⁴⁷Sm/¹⁴⁴Nd values indicate that they are derived from similar, but distinct, source materials. They probably do not sample the same lava flow, but rather are similarly sourced, but isotopically distinct, lavas that probably originate from the same volcanic complex. They may have experienced slightly different assimilation histories in route to eruption, but can be source‐crater paired. NWA 032 remains enigmatic, as its source region ¹⁴⁷Sm/¹⁴⁴Nd definitively precludes a simple relationship with NWA 4734 and LAP 02205, despite a similar bulk composition. Their high Ti/Sm, low (La/Yb)_N, and Cl‐poor apatite compositions rule out the direct involvement of KREEP. Rather, they are consistent with low‐degree partial melting of late‐formed LMO cumulates, and indicate that the geochemical characteristics attributed to urKREEP are not unique to that reservoir. These and other basaltic meteorites indicate that the youngest mare basalts originate from multiple sources, and suggest that KREEP is not a prerequisite for the most recent known melting in the Moon.     

Factors affecting the movement and persistence of nitrate and pesticides in the surficial and upper Floridan aquifers in two agricultural areas in the southeastern United States

Differences in the degree of confinement, redox conditions, and dissolved organic carbon (DOC) are the main factors that control the persistence of nitrate and pesticides in the Upper Floridan aquifer (UFA) and overlying surficial aquifer beneath two agricultural areas in the southeastern US. Groundwater samples were collected multiple times from 66 wells during 1993–2007 in a study area in southwestern Georgia (ACFB) and from 48 wells in 1997–98 and 2007–08 in a study area in South Carolina (SANT) as part of the US Geological Survey National Water-Quality Assessment Program. In the ACFB study area, where karst features are prevalent, elevated nitrate-N concentrations in the oxic unconfined UFA (median 2.5 mg/L) were significantly (p = 0.03) higher than those in the overlying oxic surficial aquifer (median 1.5 mg/L). Concentrations of atrazine and deethylatrazine (DEA; the most frequently detected pesticide and degradate) were higher in more recent groundwater samples from the ACFB study area than in samples collected prior to 2000. Conversely, in the SANT study area, nitrate-N concentrations in the UFA were mostly <0.06 mg/L, resulting from anoxic conditions and elevated DOC concentrations that favored denitrification. Although most parts of the partially confined UFA in the SANT study area were anoxic or had mixed redox conditions, water from 28 % of the sampled wells was oxic and had low DOC concentrations. Based on the groundwater age information, nitrate concentrations reflect historic fertilizer N usage in both the study areas, but with a lag time of about 15–20 years. Simulated responses to future management scenarios of fertilizer N inputs indicated that elevated nitrate-N concentrations would likely persist in oxic parts of the surficial aquifer and UFA for decades even with substantial decreases in fertilizer N inputs over the next 40 years.     

Use of archaeology to date liquefaction features and seismic events in the New Madrid seismic zone,Central United States

Prehistoric earthquake-induced liquefaction features occur in association with Native American occupation horizons in the New Madrid seismic zone. Age control of these liquefaction features, including sand-blow deposits, sand-blow craters, and sand dikes, can be accomplished by extensive sampling and flotation processing of datable materials as well as archaeobotanical analysis of associated archaeological horizons and pits. This approach increases both the amount of carbon for radiocarbon dating and the precision dating of artifact assemblages. Using this approach, we dated liquefaction features at four sites northwest of Blytheville, Arkansas, and found that at least one significant earthquake occurred in the New Madrid seismic zone between A.D. 1180 and 1400, probably about A.D. 1300 ± 100 yr. In addition, we found three buried sand blows that formed between 3340 B.C. and A.D. 780. In this region where very large to great earthquakes appear to be closely timed, archaeology is helping to develop a paleoearthquake chronology for the New Madrid seismic zone. © 1996 John Wiley & Sons, Inc.