scholarly journals Spatially-distributed influence of agro-environmental factors governing nitrate fate and transport in an irrigated stream-aquifer system

2015 ◽  
Vol 12 (2) ◽  
pp. 1653-1696
Author(s):  
R. T. Bailey ◽  
M. Ahmadi ◽  
T. K. Gates ◽  
M. Arabi
Keyword(s):  
Reactive Transport ◽  
Regional Scale ◽  
Fate And Transport ◽  
Human Populations ◽  
Arkansas River ◽  
Entire Study ◽  
Management Actions ◽  
Aquifer Systems ◽  
Canal Command ◽  
Aquifer Sensitivity

Abstract. Elevated levels of nitrate (NO3) in groundwater systems pose a serious risk to human populations and natural ecosystems. As part of an effort to remediate NO3 contamination in irrigated stream-aquifer systems, this study elucidates agricultural and environmental parameters and processes that govern NO3 fate and transport at the regional (500 km2), local (50 km2), and field scales (< 1 km2). Specifically, the revised Morris sensitivity analysis method was applied to a finite-difference nitrogen cycling and reactive transport model of a regional-scale study site in the Lower Arkansas River Valley in southeastern Colorado. The method was used to rank the influence of anthropogenic activities and natural chemical processes on NO3 groundwater concentration, NO3 mass leaching, and NO3 mass loading to the Arkansas River from the aquifer. Sensitivity indices were computed for the entire study area in aggregate as well as each canal command area, crop type, and individual grid cells. Results suggest that fertilizer loading, crop uptake, and heterotrophic denitrification govern NO3 fate and transport for the majority of the study area, while canal NO3 concentration and rates of autotrophic denitrification, nitrification, and humus decomposition dominate or partially dominate in several canal command areas. Also, NO3 leaching and groundwater concentration in adjacent cultivated fields often are governed by different processes and mass inputs/outputs. Results can be used to determine critical processes and key management actions for future data collection and remediation strategies, with efforts able to be focused on localized areas.

scholarly journals Spatially distributed influence of agro-environmental factors governing nitrate fate and transport in an irrigated stream–aquifer system

2015 ◽  
Vol 19 (12) ◽  
pp. 4859-4876 ◽  
Author(s):  
R. T. Bailey ◽  
M. Ahmadi ◽  
T. K. Gates ◽  
M. Arabi
Keyword(s):  
Regional Scale ◽  
Reduction Rate ◽  
Fate And Transport ◽  
Command Area ◽  
Human Populations ◽  
Arkansas River ◽  
Entire Study ◽  
Crop Type ◽  
O2 Reduction ◽  
Aquifer Sensitivity

Abstract. Elevated levels of nitrate (NO3) in groundwater systems pose a serious risk to human populations and natural ecosystems. As part of an effort to remediate NO3 contamination in irrigated stream–aquifer systems, this study elucidates agricultural and environmental parameters and processes that govern NO3 fate and transport at the regional (500 km2), local (50 km2), and field scales (< 1 km2). Specifically, the revised Morris sensitivity analysis method was applied to a finite-difference nitrogen cycling and reactive transport model of a regional-scale study site in the lower Arkansas River valley in southeastern Colorado. The method was used to rank the influence of anthropogenic activities and natural chemical processes on NO3 groundwater concentration, NO3 mass leaching, and NO3 mass loading to the Arkansas River from the aquifer. Sensitivity indices were computed for the entire study area in aggregate as well as each canal command area, crop type, and individual grid cells. Results suggest that fertilizer loading, crop uptake, and heterotrophic denitrification govern NO3 fate and transport for the majority of the study area, although their order of influence on NO3 groundwater concentration and mass leaching varies according to crop type and command area. Canal NO3 concentration and rates of autotrophic denitrification, nitrification, and humus decomposition also dominate or partially dominate in other locations. Each factor, with the exception of O2 reduction rate, is the dominating influence on NO3 groundwater concentration at one or more locations within the study area. Results can be used to determine critical processes and key management actions for future data collection and remediation strategies, with efforts able to be focused on localized areas.

Assessment of groundwater contamination by chlorpyrifos using the PWC model in Valencia Region (Spain)

2021 ◽  
Author(s):  
Ricardo Pérez Indoval ◽  
Javier Rodrigo-Ilarri ◽  
Eduardo Cassiraga
Keyword(s):  
Reactive Transport ◽  
Management Practices ◽  
Fate And Transport ◽  
Environmental Modeling ◽  
Transport Processes ◽  
Negative Effects ◽  
Advection Dispersion ◽  
Agricultural Applications ◽  
Transformation Processes ◽  
Mass Transport Equation

&lt;p&gt;Chlorpyrifos is commoly used as an pesticide to control weeds and prevent nondesirable grow of algae, fungi and bacteria in many agricultural applications. Despite its highly negative effects on human health, environmental modeling of this kind of pesticide in the groundwater is not commonly done in real situations. Predicting the fate of pesticides released into the natural environment is necessary to anticipate and minimize adverse effects both at close and long distances from the contamination source. A number of models have been developed to predict the behavior, mobility, and persistence of pesticides. These models should account for key hydrological and agricultural processes, such as crop growth, pesticide application patterns, transformation processes and field management practices.&lt;/p&gt;&lt;p&gt;This work shows results obtained by the Pesticide Water Calculator (PWC) model to simulate the behavior of chlorpyrifos. PWC model is used as a standard pesticide simulation model in USA and in this work it has been used to&amp;#160; simulate the fate and transport of chlorpyrifos in the unsaturated zone of the aquifer. The model uses a whole set of parameters to solve a modified version of the mass transport equation considering the combined effect of advection, dispersion and reactive transport processes. PWC is used to estimate the daily concentrations of chlorpyrifos in the Bu&amp;#241;ol-Cheste aquifer in Valencia Region(Spain).&lt;/p&gt;&lt;p&gt;A whole set of simulation scenarios have been designed to perform a parameter sensitivity analysis. Results of the PWC model obtained in this study represents a crucial first step towards the development of a pesticide risk assessment in Valencia Region. Results show that numerical simulation is a valid tool for the analysis and prediction of the fate&amp;#160; and transport of pesticides in the groundwater.&lt;/p&gt;

Source apportionment of heavy metal pollution in farmland soils on a regional scale using geographically weighted PCA

2021 ◽  
Author(s):  
Liu Shuyi ◽  
Gao Bingbo
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Source Apportionment ◽  
Rapid Development ◽  
Regional Scale ◽  
Analytical Framework ◽  
Pollution Sources ◽  
Entire Study ◽  
Soil Heavy Metals ◽  
Farmland Soils

&lt;p&gt;Source apportionment of soil heavy metals is an challenge and urgent work as the result of the rapid development of industrialization and urbanization. The common approach is multivariate statistical analysis, such as PCA and APCS/MLR, which infers only a single pattern of sources of heavy metals in entire study area. Due to complicated pathways and processes, patterns of pollution sources in a whole region may include two or more. Hence, we developed an analytical framework based on GWPCA to explore multiple patterns of sources of soil heavy metals on a regional scale. Xiangtan county, an important grain-producing area in China, was taken as a case study, which suffers the problem of heavy metal pollutions. Our results revealed the pollution situations of five soil heavy metals(Pb, Cd, As, Cr and Hg) in farmland soils and suggested that there exists various pollution patterns of these heavy metals in Xiangtan county. In each pattern, the structure of contamination sources is different. Our study also indicates that the analytical framework considering the spatial heterogeneity of pollution sources can help take more precise practices to solve this vital problem.&lt;/p&gt; &lt;p&gt;&amp;#160;&lt;/p&gt;

Multi-scale influence of topography on shallow-marine successions associated with long-term transgressions

2021 ◽  
Author(s):  
Miquel Poyatos-Moré ◽  
Ernesto Schwarz ◽  
Salvador Boya ◽  
Luz Elena Gomis-Cartesio ◽  
Ivar Midtkandal
Keyword(s):  
Regional Scale ◽  
Coarse Grained ◽  
Continuous Exposure ◽  
Entire Study ◽  
Shallow Marine ◽  
Sedimentary Characteristics ◽  
Multi Scale ◽  
Depositional Processes ◽  
Mouth Bars

&lt;p&gt;Thick shallow-marine successions associated with long-term transgressions are less well known than their thin, well-sorted counterparts, widely studied due to their potential to form good reservoirs. In these successions, particularly in storm-dominated examples, bioturbation can obliterate primary sedimentary characteristics, making stacking patterns and sequences difficult to define, and challenging our understanding of the main controls in their resulting depositional architecture. This study presents an example from the Jurassic of the Neuqu&amp;#233;n Basin (Argentina), with the aim to: a) refine the depositional model of a thick, shallow-marine succession associated with a long-term, early post-rift transgression, b) constrain multi-scale controls on stratigraphic architecture and lateral facies variability, and c) discuss their preservation and response to post-depositional processes. To do this, a &lt;300 m-thick succession has been studied along a &gt;10 km continuous exposure, with mapping, sedimentary logging and correlation of stratigraphic units, integrated with subsurface, biostratigraphic and ichnological data. The succession shows an overall retrogradational-aggradational-retrogradational stacking pattern, with several higher frequency regressive units (parasequences and parasequence sets, PSS). The lower part (PSS I) comprises laterally-discontinuous (10's of m) mouth-bars and distributary channel fills, dominated by several m-thick coarsening- and fining-up sandstone packages and m-scale erosive conglomeratic lenses. Above these, the succession (PSS II-IV) is composed by laterally-continuous (&gt;100's of m) storm-dominated lower-shoreface to upper-offshore deposits, dominated by &lt;1m-thick fine-grained and highly bioturbated tabular muddy sandstones and sandy mudstones, with rarely-preserved HCS and bioclastic-rich limestones; their internal characteristics and bed boundaries are diffuse due to pervasive bioturbation, suggesting overall low sedimentation rates and recurrent periods of colonization. The coarse-grained nature and lithology of the mouth bars and channel fills in the lower succession (PSS I) are consistent with a proximal sediment source, associated with erosion of intra-basinal highs. Its variable thickness, lateral distribution and onlap against underlying syn-rift deposits demonstrates partial infill of localized higher-accommodation areas. The well-sorted and finer-grained nature of the shoreface-offshore strata the middle and upper succession (PSS II-IV) indicates a more mature, distal source, with sediment redistributed by longshore currents, and then intensely bioturbated. These deposits display well-defined parasequences internally composed of laterally-continuous bedsets (&lt;5 m-thick). They extend along the entire study area, but show a significant vertical thickness variability. The integration of outcrop and subsurface data mapping (well and seismic) reveals this variability records the stratigraphic response of transgression over a complex, regional-scale ramp-step and underfilled rift topography, which controlled the location of main thickness and facies changes, and promoted areas of favored biogenic reworking. This study offers new insights in how to interpret thick transgressive successions based on primary depositional mechanisms and postdepositional processes, and provides useful tools to understand and predict the nature and potential preservation of these deposits in limited subsurface datasets.&lt;/p&gt;

scholarly journals Evaluating impacts of bottom trawling and hypoxia on benthic communities at the local, habitat, and regional scale using a modelling approach

2019 ◽  
Vol 77 (1) ◽  
pp. 278-289 ◽  
Author(s):  
P D van Denderen ◽  
S G Bolam ◽  
R Friedland ◽  
J G Hiddink ◽  
K Norén ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Spatial Scales ◽  
Benthic Communities ◽  
Regional Scale ◽  
The Baltic Sea ◽  
Benthic Habitats ◽  
Bottom Trawling ◽  
Management Actions ◽  
The Baltic ◽  
Local Habitat

Abstract Bottom trawling disturbance and hypoxia are affecting marine benthic habitats worldwide. We present an approach to predict their effects on benthic communities, and use the approach to estimate the state, the biomass relative to carrying capacity, of the Baltic Sea at the local, habitat, and regional scale. Responses to both pressures are expected to depend on the longevity of fauna, which is predicted from benthic data from 1558 locations. We find that communities in low-salinity regions mostly consist of short-lived species, which are, in our model, more resilient than those of the saline areas. The model predicts that in 14% of the Baltic Sea region benthic biomass is reduced by at least 50%, whereas an additional 8% of the region has reductions of 10–50%. The effects of hypoxia occur over larger spatial scales and lead to a low state of especially deep habitats. The approach is based on a simple characterization of the benthic community, which comes with high uncertainty, but allows for the identification of benthic habitats that are at greatest risk and prioritization of management actions at the regional scale. This information supports the development of sustainable approaches to manage impact of human activities on benthic ecosystems.

An approach for assessing suitability for forest management based on constraints of the physical environment at a regional scale

2015 ◽  
Vol 45 (5) ◽  
pp. 529-539 ◽  
Author(s):  
André Robitaille ◽  
Jean-Pierre Saucier ◽  
Michel Chabot ◽  
Damien Côté ◽  
Catherine Boudreault
Keyword(s):  
Forest Management ◽  
Physical Environment ◽  
A Priori ◽  
Regional Scale ◽  
Forest Growth ◽  
Sensitivity Analyses ◽  
Land Area ◽  
Forest Operations ◽  
Entire Study ◽  
Aeolian Deposits

Constraints of the physical environment affect forest growth and forest operations. At a local scale, these constraints are generally considered during forest operations. At regional or continental scales, they are often integrated to larger assessments of the potential for a given land unit to be managed. In this study, we propose an approach to analyze the integration of physical-environment constraints in forest management activities at the regional scale (482 000 km2). The land features that pose constraints to forest management (i.e., hydromorphic organic deposits, dead-ice moraines, washed till, glacial block fields, talus, and active aeolian deposits, slopes > 40%) were evaluated within 1114 land districts. To distinguish land districts that can be suitably managed from those where constraints are too important for sustainable timber production, we carried out a sensitivity analysis of physical constraints for the 1114 land districts. After analysis of two portions of the study area under management, a land district was considered suitable for management when more than 20% of its land area consists of features imposing few constraints or, for mountain-type relief districts, when more than 40% of the land area consists of features imposing few constraints. These cutoff values were defined by expert opinion, based on sensitivity analyses performed on the entire study area, on analyses of two different sectors with different types of constraints and on a strong understanding of the study area. Our results show that land districts where the physical environment posed significant constraints covered 7.5% of the study area (36 000 km2). This study shows that doing an a priori classification of land units based on permanent environmental features could facilitate the identification of areas that are not suitable for forest management activities.

Shallow groundwater dynamics in smectite dominated clay on the Liverpool Plains of New South Wales

Soil Research ◽  
2001 ◽  
Vol 39 (2) ◽  
pp. 203 ◽  
Author(s):  
W. Timms ◽  
R. I. Acworth ◽  
D. Berhane
Keyword(s):  
New South ◽  
Regional Scale ◽  
New South Wales ◽  
Shallow Groundwater ◽  
Important Indicator ◽  
Groundwater Levels ◽  
South Wales ◽  
Aquifer Systems ◽  
North Eastern ◽  
Shallow Groundwater System

Dynamic shallow (<5 m) groundwater levels are an important indicator of water and salt fluxes in smectite-dominated clay on the Liverpool Plains in north-eastern New South Wales. Previous hydrogeological assessments of shallow groundwater related salinity risk have focused on regional scale distribution and interaction with rising pressure levels in confined aquifer systems. In this study, groundwater levels over a 7-year period for the saline Yarramanbah subcatchment are presented, along with data from 60 new and existing shallow piezometers and precise elevation surveying and intensive automated monitoring at selected sites. The shallow groundwater system is shown to respond to recharge; however, over the medium-term it is in hydrologic balance, with no evidence of increased water storage. A proportion of recharge is lost by discharge into deeply incised surface channels. Groundwater salinity in the banks of Warrah Creek indicate that flushing of salts from clay is related to increased flux of fresh water. Concern exists that there may be increased salt export from the catchment. If this is in fact occurring while the plains are in hydrologic equilibrium, then increased salt fluxes must be related to factors other than rising groundwater levels.

Assessing the importance of fishing impacts on Hawaiian coral reef fish assemblages along regional-scale human population gradients

2008 ◽  
Vol 35 (3) ◽  
pp. 261-272 ◽  
Author(s):  
I. D. WILLIAMS ◽  
W. J. WALSH ◽  
R. E. SCHROEDER ◽  
A. M. FRIEDLANDER ◽  
B. L. RICHARDS ◽  
...  
Keyword(s):  
Coral Reef ◽  
Population Density ◽  
Human Population ◽  
Fish Assemblages ◽  
Regional Scale ◽  
Reef Fishes ◽  
Human Populations ◽  
Fish Biomass ◽  
Human Population Density ◽  
General Decline

SUMMARYHumans can impact coral reef fishes directly by fishing, or indirectly through anthropogenic degradation of habitat. Uncertainty about the relative importance of those can make it difficult to develop and build consensus for appropriate remedial management. Relationships between fish assemblages and human population density were assessed using data from 18 locations widely spread throughout the Main Hawaiian Islands (MHI) to evaluate the significance of fishing as a factor potentially driving fish trends on a regional scale. Fish biomass in several groups was negatively correlated with local human population density and a number of lines of evidence indicate that fishing was the prime driver of those trends. First, declines were consistently evident among fish groups targeted by fishers, but not among lightly fished or non-target groupings, which indicates that declines in target groups were not simply indicative of a general decline in habitat quality along human population gradients. Second, proximity to high human populations was not associated with low fish biomass where shoreline structure prevented ready access by fishers. Relatively remote and inaccessible locations within the MHI had 2.1–4.2 times the biomass of target fishes compared to accessible and populous locations, and may therefore function as partial refugia. However, stocks in those areas were clearly far from pristine, as biomass of large predators was more than an order of magnitude lower than at more intact ecosystems elsewhere in the Pacific.

Multi-scale spatial analysis of human alveolar echinococcosis risk in China

Parasitology ◽  
2003 ◽  
Vol 127 (S1) ◽  
pp. S133-S141 ◽  
Author(s):  
F. M. DANSON ◽  
A. J. GRAHAM ◽  
D. R. J. PLEYDELL ◽  
M. CAMPOS-PONCE ◽  
P. GIRAUDOUX ◽  
...  
Keyword(s):  
Spatial Data ◽  
Disease Transmission ◽  
Spatial Scales ◽  
Regional Scale ◽  
Central China ◽  
Spatial Data Analysis ◽  
Transmission Risk ◽  
Spatial Proximity ◽  
Human Populations ◽  
Remotely Sensed Data

Risk factors for the transmission of Echinococcus multilocularis to humans operate at a range of spatial scales. Over a large area, such as China, regional scale risk is correlated with variation in climatic conditions because of its effect on the spatial distribution of landscapes that can support E. multilocularis transmission in wildlife hosts and the probability of egg survival. At a local scale of a few kilometres, or tens of kilometres, transmission risk is related to the spatial proximity of human populations and landscapes with active transmission. At the patch scale, when considering individual villages or households, human behavioural factors are important and for individuals genetic and immunological factors play a role. Satellite remote sensing can provide landscape information at a range of spatial scales and provide a spatial framework within which to examine transmission patterns. This paper reviews the application of remotely sensed data and spatial data analysis to develop a better understanding of disease transmission and shows how such data have been used to examine human alveolar echinocossosis infection patterns, at a range of spatial scales, in an endemic area in central China.

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