USGS Science⌕ Search

SEARCH · USGS Science

Results for “Genes”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

1,608 records · Page 90Linked to original sources
USGS2017

Extent and persistence of secondary water quality impacts after enhanced reductive bioremediation

Electron donor (ED) addition can be very effective in stimulating enhanced reductive bioremediation (ERB) of a wide variety of groundwater contaminants. However, ERB can result in Secondary Water Quality Impacts (SWQIs) including decreased levels of dissolved oxygen (O 2 ), nitrate (NO 3- ), and sulfate (SO 4 2- ), and elevated levels of dissolved manganese (Mn 2+ ), dissolved iron (Fe 2+ ), methane (CH 4 ), sulfide (S 2- ), organic carbon, and naturally occurring hazardous compounds (e.g., arsenic). Fortunately, this ‘plume’ of impacted groundwater is usually confined within the original contaminant plume and is unlikely to adversely impact potable water supplies. This report summarizes available information on processes controlling the production and natural attenuation of SWQI parameters and can be used as a guide in understanding the magnitude, areal extent, and duration of SWQIs in ERB treatment zones and the natural attenuation of SWQI parameters as the dissolved solutes migrate downgradient with ambient groundwater flow. This information was compiled from a wide variety of sources including a survey and statistical analysis of SWQIs from 47 ERB sites, geochemical model simulations, field studies at sites where organic-rich materials have entered the subsurface (e.g., wastewater, landfill leachate, and hydrocarbon plumes), and basic information on physical, chemical, and biological processes in the subsurface. This information is then integrated to provide a general conceptual model of the major processes controlling SWQI production and attenuation.

Technical Report↗
USGS2019

Toward a theory of connectivity among depressional wetlands of the great plains

Functions of inland, freshwater depressional wetlands of the Great Plains are driven by natural disturbance in the form of fluctuating water levels or shifts between wet and dry ecological states. The geographically isolated prairie potholes and playas form broad-scale systems or networks that support biodiversity and provide ecological goods and services. Anthropogenic disturbance, primarily in the form of sediment accretion, results in the functional loss of individual wetlands from the system. The ecological value of individual depressional wetlands has been documented, but there has not been any assessment of the contribution of individual wetlands to the system. Network analysis can be used to prioritize the contribution of individual wetlands to the system for the purpose of conservation and management. We utilized the playas wetland system of the Southern High Plains to illustrate this concept. Playas form a redundant, resilient network based on natural disturbance (i.e., inundation patterns) across broad spatial and temporal scales that support biodiversity. Loss of individual playas to sediment accretion is causing the network to break down, resulting in the need for a greater proportion of inundated playas to provide the original level of ecological goods and services. The effects of decreased functional connectivity due to anthropogenic disturbance at the system scale portend negative effects on movement strategies, dynamics and persistence of local populations, decreased biodiversity, and, ultimately, the redistribution and system-wide extinction of playa wetland-dependent populations and loss of associated functions.

Book chapter↗
USGS2004

Light attenuation profiling as an indicator of structural changes in coastal marshes

To best respond to natural and human-induced stresses, resource managers and researchers require remote sensing techniques that can map the biophysical characteristics of natural resources on regional and local scales. The implementation of advanced measurement techniques would provide significant improvements in the quantity, quality, and timeliness of biophysical data useful in understanding the sensitivity of vegetation communities to external influences. In turn, this biophysical data would provide resource planners with a rational decision-making system for resource allocation and response action development planning.

Book chapter↗