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Elevated Nitrate Levels in Soils of the Eastern Mojave Desert
Author(s) -
Marrett D. J.,
Khattak R. A.,
Elseewi A. A.,
Page A. L.
Publication year - 1990
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1990.00472425001900040005x
Subject(s) - soil water , alluvium , nitrate , saturation (graph theory) , geology , leaching (pedology) , salinity , alluvial fan , lessivage , mineralogy , chemistry , environmental chemistry , soil science , geochemistry , sedimentary rock , geomorphology , oceanography , mathematics , organic chemistry , combinatorics
Deep cores taken on an uncultivated desert alluvial fan revealed two large volumes of coarse soil with high NO 3 levels (20–208 mg L −1 NO 3 ‐N in water saturation extracts). Nitrate levels were unpredictable both laterally and vertically and unrelated to alluvial strata. The large soil volumes with elevated NO 3 levels were found 2.7 to 7.3 m deep in four cores at one 3 by 3 m site, and 8.8 to 21 m deep in two cores at another site. Isolated samples with elevated NO 3 were found in three other cores and six cores contained no elevated NO 3 . Overall, nitrate was best correlated with EC, Na, SO 4 , and Cl ( r = 0.68, 0.66, 0.67, and 0.73, respectively; P ≤ 0.05). Stronger correlations were found within the four individual sites and 15 cores, but the ions best correlated with NO 3 varied, even between cores from the same site. Saturation extract NO 3 was not correlated with bulk soil total organic C or total N. The NO 3 distribution patterns found appear related to inorganic processes (salinization and leaching), but specific processes of N redistribution and primary N sources remain unclear. Elevated NO 3 in deep soils appears to be a natural phenomena that reflects Pleistocene site conditions and possible geologic NO 3 sources. Local volcanic rocks contain up to 73 mg NO 3 ‐N kg −1 rock (water‐extractable). Naturally elevated NO 3 levels in rocks and coarse alluvial fan soils are poorly understood and easily overlooked potential sources of groundwater NO 3 .