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1.
Front Environ Sci ; 12: 1-19, 2024 Feb 22.
Artículo en Inglés | MEDLINE | ID: mdl-38516348

RESUMEN

Continued large-scale public investment in declining ecosystems depends on demonstrations of "success". While the public conception of "success" often focuses on restoration to a pre-disturbance condition, the scientific community is more likely to measure success in terms of improved ecosystem health. Using a combination of literature review, workshops and expert solicitation we propose a generalized framework to improve ecosystem health in highly altered river basins by reducing ecosystem stressors, enhancing ecosystem processes and increasing ecosystem resilience. We illustrate the use of this framework in the Mississippi-Atchafalaya River Basin (MARB) of the central United States (U.S.), by (i) identifying key stressors related to human activities, and (ii) creating a conceptual ecosystem model relating those stressors to effects on ecosystem structure and processes. As a result of our analysis, we identify a set of landscape-level indicators of ecosystem health, emphasizing leading indicators of stressor removal (e.g., reduced anthropogenic nutrient inputs), increased ecosystem function (e.g., increased water storage in the landscape) and increased resilience (e.g., changes in the percentage of perennial vegetative cover). We suggest that by including these indicators, along with lagging indicators such as direct measurements of water quality, stakeholders will be better able to assess the effectiveness of management actions. For example, if both leading and lagging indicators show improvement over time, then management actions are on track to attain desired ecosystem condition. If, however, leading indicators are not improving or even declining, then fundamental challenges to ecosystem health remain to be addressed and failure to address these will ultimately lead to declines in lagging indicators such as water quality. Although our model and indicators are specific to the MARB, we believe that the generalized framework and the process of model and indicator development will be valuable in an array of altered river basins.

2.
J Environ Qual ; 53(2): 209-219, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38263599

RESUMEN

Few strategies are available to reduce nitrate-nitrogen (NO3 -N) loads at larger landscape scales, but flood control reservoirs are known to reduce riverine loads. In this study, we evaluated the potential to increase nitrogen (N) loss at Lake Red Rock, a large reservoir located in central Iowa, by evaluating the inundation of sediments deposited at the reservoir inflow. Sediment samples were collected at 51 locations in the lower delta region and analyzed for particle size and nutrient content. Nitrogen loss rates in delta sediments were determined from laboratory assays, and satellite imagery was used to develop a rating curve to quantify land area inundated within the delta. The daily mass of NO3 -N reduced with delta inundation was estimated by applying the mean N 24-h loss rate (0.66 g N m2 day-1 ) by the area of inundation (m2 ). Results indicated that raising pool elevations to inundate more of the delta would result in greater N losses, ranging from 2 to 377 Mg per year. Potential N loss of 102 Mg achieved by increasing pool stage by 0.5 m would be equivalent to installing nearly 650 edge-of-field practices in the watershed. Although more work is needed to integrate with an existing environmental pool management plan, study results indicate that reservoir management could achieve N reductions at a novel landscape scale.


Asunto(s)
Nitrógeno , Contaminantes Químicos del Agua , Nitrógeno/análisis , Nitratos/análisis , Inundaciones , Lagos , Iowa , Monitoreo del Ambiente/métodos , China , Contaminantes Químicos del Agua/análisis
3.
J Environ Qual ; 52(6): 1063-1079, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37725393

RESUMEN

To monitor and meet water quality objectives, it is necessary to understand and quantify the contribution of nonpoint sources to total phosphorus (P) loading to surface waters. However, the contribution of streambank erosion to surface water P loads remains unclear and is typically unaccounted for in many nutrient loading assessments and policies. As a result, agricultural contributions of P are overestimated, and a potentially manageable nonpoint source of P is missed in strategies to reduce loads. In this perspective, we review and synthesize the results of a special symposium at the 2022 ASA-CSSA-SSSA annual meeting in Baltimore, MD, that focused on streambank erosion and its contributions to P loading of surface waters. Based on discussions among researchers and policy experts, we overview the knowns and unknowns, propose next steps to understand streambank erosion contribution to P export budgets, and discuss implications of the science of streambank erosion for policy and nutrient loss reduction strategies.


Asunto(s)
Monitoreo del Ambiente , Fósforo , Monitoreo del Ambiente/métodos , Fósforo/análisis , Calidad del Agua , Agricultura , Nutrientes
4.
Sci Total Environ ; 883: 163607, 2023 Jul 20.
Artículo en Inglés | MEDLINE | ID: mdl-37098395

RESUMEN

While carbon is a critically important natural element cycling through the soil profile of agricultural systems, few studies have examined the flux of dissolved organic carbon (OC) and inorganic carbon (IC) through artificially-drained cropped fields. In this study, we monitored eight tile outlets, nine groundwater wells and the receiving stream during a March to November period in 2018 to quantify subsurface IC and OC flux from tiles and groundwater to a perennial stream from a single cropped field in north-central Iowa. Results showed that carbon export from the field was dominated by IC losses through subsurface drainage tiles that were 20× higher than dissolved OC concentration in tiles, groundwater and in Hardin Creek. IC loads from tiles comprised approximately 96 % of the total carbon export. Detailed soil sampling within the field quantified TC stocks to a 1.2 m depth (246,514 kg/ha), and based on the maximum annual rate of IC loss from the field (553 kg/ha per year), we estimated that approximately 0.23 % of the TC content (0.32 % of the TOC content and 0.70 % of the TIC content) of the shallow soils was lost in a single year. Loss of dissolved carbon from the field is likely offset by reduced tillage and additions of lime. Study results suggest that attention should be given to improved monitoring of aqueous total carbon export from fields for accurate accounting of carbon sequestration performance.

5.
mSphere ; 8(3): e0057122, 2023 Jun 22.
Artículo en Inglés | MEDLINE | ID: mdl-37017537

RESUMEN

Row crop production in the agricultural Midwest pollutes waterways with nitrate, and exacerbates climate change through increased emissions of nitrous oxide and methane. Oxygenic denitrification processes in agricultural soils mitigate nitrate and nitrous oxide pollution by short-circuiting the canonical pathway to avoid nitrous oxide formation. Furthermore, many oxygenic denitrifiers employ a nitric oxide dismutase (nod) to create molecular oxygen that is used by methane monooxygenase to oxidize methane in otherwise anoxic soils. The direct investigation of nod genes that could facilitate oxygenic denitrification processes in agricultural sites is limited, with no prior studies investigating nod genes at tile drainage sites. Thus, we performed a reconnaissance of nod genes at variably saturated surface sites, and within a variably to fully saturated soil core in Iowa to expand the known distribution of oxygenic denitrifiers. We identified new nod gene sequences from agricultural soil and freshwater sediments in addition to identifying nitric oxide reductase (qNor) related sequences. Surface and variably saturated core samples displayed a nod to 16S rRNA gene relative abundance of 0.004% to 0.1% and fully saturated core samples had relative nod gene abundance of 1.2%. The relative abundance of the phylum Methylomirabilota increased from 0.6% and 1% in the variably saturated core samples to 3.8% and 5.3% in the fully saturated core samples. The more than 10-fold increase in relative nod abundance and almost 9-fold increase in relative Methylomirabilota abundance in fully saturated soils suggests that potential oxygenic denitrifiers play a greater nitrogen cycling role under these conditions. IMPORTANCE The direct investigation of nod genes in agricultural sites is limited, with no prior studies investigating nod genes at tile drains. An improved understanding of nod gene diversity and distribution is significant to the field of bioremediation and ecosystem services. The expansion of the nod gene database will advance oxygenic denitrification as a potential strategy for sustainable nitrate and nitrous oxide mitigation, specifically for agricultural sites.


Asunto(s)
Óxido Nitroso , Suelo , Óxido Nitroso/metabolismo , Nitratos/metabolismo , Ecosistema , Oxígeno/metabolismo , ARN Ribosómico 16S/genética , Bacterias , Óxido Nítrico , Metano/metabolismo
6.
Environ Monit Assess ; 194(10): 784, 2022 Sep 13.
Artículo en Inglés | MEDLINE | ID: mdl-36098866

RESUMEN

Accurate field-scale maps of soil properties including features such as texture, soil organic matter (SOM) content, and hydraulic conductivity are essential for proper placement of conservation practices that utilize anoxic soil environments for denitrification. However, in many cases, soil maps inaccurately represent subsoil properties and can mislead managers about where to install new practices. Non-invasive methods of subsoil property analysis including electromagnetic induction techniques are a potentially efficient method for improving existing field-scale soil maps. In this study, we quantified the accuracy of existing soil maps in an agricultural field in north-central Iowa. Of 60 soil cores collected and reclassified, 19 were identified as taxadjunct at the soil series level primarily due to hydrologic indicators and soil particle size. We assessed the correlation among physical and chemical soil properties measured in-lab and geophysical responses measured in-field. We identified significant correlation of SOM and sand to electrical conductivity for individual core and mean soil series data. From this analysis, we developed a conservation practice suitability map and evaluated the potential for field-scale geophysical investigations to serve as a new tool for agricultural conservation planning and placement of site-specific denitrifying conservation practices. Study results suggest that incorporating a geophysical conductivity investigation into conservation planning may improve understanding of critical soil properties beyond those ascertained with limited soil borings.


Asunto(s)
Monitoreo del Ambiente , Suelo , Agricultura/métodos , Conductividad Eléctrica , Monitoreo del Ambiente/métodos , Hidrología , Suelo/química
7.
Environ Monit Assess ; 194(7): 506, 2022 Jun 16.
Artículo en Inglés | MEDLINE | ID: mdl-35705832

RESUMEN

The use of saturated buffers for reducing NO3-N loads from tile-drained croplands is increasing in the US Midwest and there is a need to develop options for estimating reductions at riparian sites. In this study, we present a paired water table monitoring approach to estimate hydraulic and NO3-N loading into a saturated buffer in eastern Iowa. One well was located within the saturated buffer (treatment) and a second well was installed in the same section of the riparian buffer but without the saturated buffer (control). Over a season of monitoring, water table depths were remarkably consistent between the two wells but the water table beneath the saturated buffer was consistently 0.22 m higher than the non-saturated buffer control. The increase in water table height increased the amount of water discharged from a 162 m long buffer by 468.2 m3/year and, assuming concentration reduction of 15 mg/l, resulted in a N reduction of approximately 7 kg. Although more work is needed to document this paired monitoring approach elsewhere, the method may hold promise for inexpensively quantifying the performance of conservation practices at landowner-led sites.


Asunto(s)
Agua Subterránea , Contaminantes Químicos del Agua , Monitoreo del Ambiente , Nitratos/análisis , Estaciones del Año , Agua
8.
Sci Total Environ ; 839: 156302, 2022 Sep 15.
Artículo en Inglés | MEDLINE | ID: mdl-35640760

RESUMEN

Improving food systems to address food insecurity and minimize environmental impacts is still a challenge in the 21st century. Ecohydrological models are a key tool for accurate system representation and impact measurement. We used a multi-phase testing approach to represent baseline hydrologic conditions across three agricultural basins that drain parts of north central and central Iowa, U.S.: the Des Moines River Basin (DMRB), the South Skunk River Basin (SSRB), and the North Skunk River Basin (NSRB). The Soil and Water Assessment Tool (SWAT) ecohydrological model was applied using a framework consisting of the Hydrologic and Water Quality System (HAWQS) online platform, 40 streamflow gauges, the alternative runoff curve number method, additional tile drainage and fertilizer application. In addition, ten SWAT baselines were created to analyze both the HAWQS parameters (baseline 1) and nine alternative baseline configurations (considering the framework). Most of the models achieved acceptable statistical replication of measured (close to the outlet) streamflows, with Nash-Sutcliffe (NS) values ranging up to 0.80 for baseline 9 in the DMRB and SSRB, and 0.78 for baseline 7 in the NSRB. However, water balance and other hydrologic indicators revealed that careful selection of management data and other inputs are essential for obtaining the most accurate representation of baseline conditions for the simulated stream systems. Using cumulative distribution curves as a criterion, baselines 7 to 10 showed the best fit for the SSRB and NSRB, but none of the baselines accurately represented 20% of low flows for the DMRB. Analysis of snowmelt and growing season periods showed that baselines 3 and 4 resulted in poor simulations across all three basins using four common statistical measures (NS, KGE, Pbias, and R2), and that baseline 9 was characterized by the most satisfactory statistical results, followed by baselines 5, 7 and 1.


Asunto(s)
Suelo , Calidad del Agua , Hidrología , Iowa , Modelos Teóricos
9.
Environ Sci Process Impacts ; 23(10): 1531-1541, 2021 Oct 20.
Artículo en Inglés | MEDLINE | ID: mdl-34515719

RESUMEN

Abiotic reduction of nitrite (NO2-) by Fe(II) species (i.e., chemodenitrification) has been demonstrated in a variety of natural environments and laboratory studies, and is a potentially significant source of atmospheric nitrous oxide (N2O) emissions. It is, however, unclear how chemodenitrification rates and N2O yields vary among heterogeneous Fe(II) species under similar conditions and whether abiotic reduction competes with biological NO2- reduction. Here, we measured rates of NO2- reduction and extents of N2O production by several Fe(II) species under consistent, environmentally relevant conditions (i.e., pH 7.0, bicarbonate buffer, and 0.1 mM NO2-). Nitrite reduction rates varied significantly among the heterogeneous Fe(II) species with half-lives (t1/2) ranging from as low as an hour to over two weeks following the trend of goethite/Fe(II) ∼ hematite/Fe(II) ∼ magnetites > maghemite/Fe(II) > sediment/Fe(II). Interestingly, we observed no clear trend of increasing NO2- reduction rates with higher magnetite stoichiometry (x = Fe2+/Fe3+). Nitrogen recovery as N2O also varied significantly among the Fe species ranging from 21% to 100% recovery. We further probed both chemodenitrification and biological denitrification in the absence and presence of added aqueous Fe(II) with a sediment collected from the floodplain of an agricultural watershed. While abiotic NO2- reduction by the sediment + Fe(II) was much slower than the laboratory Fe(II) species, we found near complete mass N balance during chemodenitrification, as well as evidence for both abiotic and biological NO2- reduction potentially occurring in the sediment under anoxic conditions. Our results suggest that in redox active sediments and soils both chemodenitrification and biological denitrification are likely to occur simultaneously, and that agricultural watersheds may be significant sources of N2O emissions.


Asunto(s)
Desnitrificación , Nitritos , Óxido Ferrosoférrico , Nitrógeno , Óxido Nitroso
10.
J Environ Manage ; 299: 113647, 2021 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-34523537

RESUMEN

Shallow constructed ponds are abundant landscape features in the midwestern United States, suggested as an edge of field best management practice (BMP) in voluntary nutrient reduction strategies. The efficacy of such features is highly uncertain, however, and previous studies have lacked sufficient temporal resolution to determine N and P removals during critical periods of transport. We utilized high-frequency in-situ measurements and flow-weighted grab sampling to determine water and nutrient budgets for a typical constructed "farm pond" in central Iowa situated within the Iowa Southern Drift Plain. Our monitoring approach yielded insight into in-stream nitrogen processing and the relative importance of transport-vs. supply-limited N delivery. Diel patterns in NO3-N observed during early Spring, prior to canopy closure, revealed that in-stream primary production and NO3-N assimilation can influence downstream N delivery in a stream with nitrate pollution (mean annual NO3-N of nearly 5 mg/L). Analysis of discharge-concentration hysteresis for NO3-N showed a shift from transport to supply limitation for NO3-N delivery over the growing season, influenced by antecedent moisture, with wet antecedent conditions leading to supply limitation. Significant NO3-N removal (64% of 19.8 kg/ha inputs) occurred within the 4.2 ha pond (230 ha watershed), but total N removal was much lower (36% removal of 22.3 kg/ha inputs). The lower total N removal highlights the importance of both particulate N and dissolved organic N and ammonia export to the N budgets of hypereutrophic small ponds. Total P removal in the pond was only 8% of 2.3 kg/ha inputs, likely due to internal loading of recent and legacy sedimentary P within the pond. High-flow events dominated N and P inputs, during which removal efficacy of the pond was significantly diminished. Poor process performance during critical moments may partially explain lower than expected water quality improvements post-BMP implementation. Accordingly, shifting hydroclimatic regimes (e.g., frequency of intense rainfall events) will impact the efficacy of small ponds and other edge of field BMPs for nutrient reduction.


Asunto(s)
Estanques , Contaminantes Químicos del Agua , Monitoreo del Ambiente , Granjas , Iowa , Nitrógeno/análisis , Nutrientes , Fósforo/análisis , Contaminantes Químicos del Agua/análisis
11.
Environ Monit Assess ; 193(8): 500, 2021 Jul 21.
Artículo en Inglés | MEDLINE | ID: mdl-34291322

RESUMEN

Agricultural drainage tiles are primary contributors to NO3-N export from Iowa croplands. Saturated buffers are a relatively new conservation practice that diverts tile water into a distribution tile installed in a riparian buffer parallel to a stream with the intent of enhancing NO3-N processing within the buffer. In this study, tile NO3-N concentration reductions were characterized through two different saturated buffers at a working farm site in eastern Iowa. Study objectives were to (1) evaluate the hydrogeology and water quality patterns in the saturated buffer and (2) quantify the reduction in tile NO3-N concentration from the saturated buffer installation. Results showed that the two saturated buffers are reducing NO3-N concentrations in tile drainage water from input concentrations of approximately 15 mg/l to levels < 1.5 mg/l at the streamside well locations. The reduction occurs rapidly in the fine-textured and organic-rich alluvial soils with most of the reduction occurring within 1.5 m of the distribution line. Denitrification is hypothesized as being primarily responsible for the concentration reductions based on soil and water chemistry conditions, completion of a geophysical survey (quantifying low potential for N loss to deeper aquifers), and comparisons to other similar Iowa sites. The study provides more assurance to new adopters that this practice can be installed in many areas throughout the Midwestern Cornbelt region.


Asunto(s)
Monitoreo del Ambiente , Ríos , Agricultura , Iowa , Nitratos/análisis , Nitrógeno/análisis , Suelo
12.
Sci Total Environ ; 782: 146643, 2021 Aug 15.
Artículo en Inglés | MEDLINE | ID: mdl-33838365

RESUMEN

There is an ongoing need to increase our understanding of the sources and timing of stream nitrate loads across agricultural watersheds in Iowa as water quality improvement strategies are implemented. The goal of this study was to model the relationship between nitrate load and the two components of streamflow (i.e., baseflow and stormflow) to quantify in-stream nitrate patterns and develop a new method for estimating loads on days when monitoring data are not available. We analyzed eight watersheds in Iowa that had long-term water quality data where grab samples have been collected from 1987 to 2019. Four regression models were developed that related daily nitrate load to daily baseflow, stormflow, and streamflow discharge. The first model considered baseflow as a predictor, the second model used stormflow, the third model included both baseflow and stormflow as two different covariates, and the final model used total streamflow (unseparated). For all eight watersheds, the baseflowstormflow models had the highest correlation coefficients, which indicates that both components are necessary and together improve nitrate load estimates. While baseflow models estimated lower nitrate loads better, stormflow models captured the variability associated with larger loads. In addition, streamflow models tended to overestimate large nitrate loads. This simple modeling framework can be used to calculate daily, monthly and annual nitrate loads. Delineating nitrate loads between stormflow and baseflow can help identify differences in nitrate sources for nutrient reduction and remediation.

13.
J Environ Qual ; 49(4): 909-920, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-33016492

RESUMEN

Regional groundwater phosphorus (P) concentrations are rarely reported, and it is important to develop a better understanding of background concentrations in shallow groundwater to help develop strategies to mitigate environmental risks. In this study, results collected from 17 different Iowa-based studies conducted from 2006 to 2019 and a total of 210 discrete locations of water table dissolved phosphate (DPO4 3- ) measurements are summarized (a) to assess the occurrence, range, and statistical distribution of groundwater DPO4 3- concentrations in Iowa and (b) to evaluate statewide patterns of DPO4 3- concentrations related to land use or land cover and landscape position. The DPO4 3- concentrations ranged from 0.02 to 1.56 mg L-1 and averaged 0.15 ± 0.19 mg L-1 with a median value of 0.10 mg L-1 (95% confidence interval of 0.08-0.11 mg L-1 ). Although minor variations were observed among land cover class and landscape position, concentrations exhibited uniformity across the state, likely attesting to the legacy of P from historical agricultural management. Median concentrations are higher than typical water quality criteria used to assess risk to surface water systems, implying that simply discharging groundwater DPO4 3- to streams, rivers, and lakes would be sufficient to cause environmental degradation.


Asunto(s)
Agua Subterránea , Fosfatos , Monitoreo del Ambiente , Iowa , Calidad del Agua
15.
Environ Sci Process Impacts ; 22(6): 1315-1346, 2020 Jun 24.
Artículo en Inglés | MEDLINE | ID: mdl-32267911

RESUMEN

Neonicotinoid insecticides are widely used in both urban and agricultural settings around the world. Historically, neonicotinoid insecticides have been viewed as ideal replacements for more toxic compounds, like organophosphates, due in part to their perceived limited potential to affect the environment and human health. This critical review investigates the environmental fate and toxicity of neonicotinoids and their metabolites and the potential risks associated with exposure. Neonicotinoids are found to be ubiquitous in the environment, drinking water, and food, with low-level exposure commonly documented below acceptable daily intake standards. Available toxicological data from animal studies indicate possible genotoxicity, cytotoxicity, impaired immune function, and reduced growth and reproductive success at low concentrations, while limited data from ecological or cross-sectional epidemiological studies have identified acute and chronic health effects ranging from acute respiratory, cardiovascular, and neurological symptoms to oxidative genetic damage and birth defects. Due to the heavy use of neonicotinoids and potential for cumulative chronic exposure, these insecticides represent novel risks and necessitate further study to fully understand their risks to humans.


Asunto(s)
Insecticidas , Neonicotinoides , Agricultura , Animales , Anomalías Congénitas , Estudios Transversales , Exposición a Riesgos Ambientales , Salud Ambiental , Humanos , Insecticidas/toxicidad , Neonicotinoides/toxicidad
16.
J Environ Qual ; 48(3): 579-585, 2019 May.
Artículo en Inglés | MEDLINE | ID: mdl-31180425

RESUMEN

The Neal Smith National Wildlife Refuge was established as a tallgrass prairie ecosystem reconstruction in the Walnut Creek watershed (5238 ha), Jasper County, Iowa, with >1200 ha of prairie plantings initiated between 1993 and 2006. This study updates the documented decreases in watershed NO-N losses that accompanied this change in land cover to a 20-yr record. Annual flow-weighted NO-N concentrations declined by 0.15 mg NO-N L yr, which was not significantly different from the rate of 0.07 mg NO-N L yr reported after the first decade of monitoring. There was also evidence ( < 0.1) that prairie reconstruction led to a declining trend in annual watershed water yield, which would have contributed to the trend of decreasing NO-N loads. However, variability in climate, including 2 yr with significant flooding events followed by a major drought during the second decade of monitoring, challenged any notion that a watershed water quality record will stabilize even >10 yr after a substantial change in land cover, in this naturally drained watershed underlain by fine grained glacial deposits that exhibit multidecadal groundwater transport times. Efforts to document progress toward water quality goals will need to consider dominant flow paths and associated travel times, uncertainty in the effectiveness of management changes, and a changeable climate.


Asunto(s)
Ecosistema , Calidad del Agua , Pradera , Illinois , Iowa , Mississippi
17.
Environ Monit Assess ; 191(4): 231, 2019 Mar 20.
Artículo en Inglés | MEDLINE | ID: mdl-30895458

RESUMEN

Baseflow is an important component of streamflow and watershed hydrologic budgets, yet quantifying the baseflow fraction of tile drainage has rarely been reported. In this study, we used two common hydrograph separation methods (local minimum method, recursive digital filter) to separate the discharge hydrographs from three drainage district tiles located in Iowa. Based on data collected from 2009 to 2013, annual baseflow ranged from 116 to 162 mm and comprised approximately 60% of the annual discharge. Baseflow was greatest during June (average of 34% of annual baseflow) and the March through August period produced 86% of the total annual baseflow. We found that the two methods of hydrograph separation produced similar results but the digital filter method was less erratic in estimating baseflow fraction. Study results can be used to better quantify hydrologic pathways in tiled landscapes and improve the design, implementation, and evaluation of nutrient reduction strategies.


Asunto(s)
Monitoreo del Ambiente , Agua Subterránea/análisis , Movimientos del Agua , Abastecimiento de Agua/estadística & datos numéricos , Iowa
18.
Sci Total Environ ; 660: 1015-1028, 2019 Apr 10.
Artículo en Inglés | MEDLINE | ID: mdl-30743899

RESUMEN

Floodplain storage commonly represents one of the largest sediment fluxes within sediment budgets. In watersheds responding to large scale disturbance, floodplain-channel lateral connectivity may change over time with progression of channel evolution and associated changes in channel geometry. In this study we investigated the effects of channel geometry change on floodplain inundation frequency and flux of suspended sediment (SS) and total phosphorus (TP) to floodplain storage within the 52.2 km2 Walnut Creek watershed (Iowa, USA) through a combination of 25 in-field channel cross section transects, hydraulic modeling (HEC-RAS), and stream gauging station-derived water quality and quantity data. Cross sectional area of the 25 in-field channel cross sections increased by a mean of 17% over the 16 year study period (1998-2014), and field data indicate a general trend of degradation and widening to be present along Walnut Creek's main stem. Estimated stream discharge required to generate lateral overbank flow increased 15%, and floodplain inundation volume decreased by 37% over study duration. Estimated annual fluxes of SS and TP to floodplain storage decreased by 61 and 62% over study duration, respectively. The estimated reductions in flux to floodplain storage have potential to increase watershed export of SS and TP by 9 and 18%, respectively. Increased contributions to SS and TP export may continue as channel evolution progresses and floodplain storage opportunities continue to decline. In addition to loss of storage, higher discharges confined to the channel may have greater stream power, resulting in further enhancement of SS and TP export through accelerated bed and bank erosion. These increased contributions to watershed loads may mask SS and TP reductions achieved through edge of field practices, thus making it critical that stage and progression of channel evolution be taken into consideration when addressing sediment and phosphorus loading at the watershed scale.

19.
Sci Total Environ ; 657: 1432-1440, 2019 Mar 20.
Artículo en Inglés | MEDLINE | ID: mdl-30677909

RESUMEN

Roadside ditches are an integral component to the >6.3 million km of roadsides in the U.S. and act as drainageways for millions of hectares of watershed runoff. Our study of six roadside ditches in Lime Creek watershed characterized soil nutrients and heavy metal patterns as well as quantified the physical and hydrological properties of ditch soils. At all ditch sites, we identified significant sedimentation of silt-sized particles, total nitrogen, and soil carbon in shallow roadside ditch soils. A post-settlement surface soil horizon significantly higher in silt content was observed compared to the underlying subsoil and parent material. Although accumulation of several heavy metals was measured in ditch soils, significant variability was not observed within the ditch environment. Most of the heavy metal concentrations were found to be either similar to or lower than state-wide averages. Higher levels of calcium near the roads were likely due to annual use of road deicers. Overall, we estimated that 42 Mg/ha of total carbon and 5 Mg/ha of total nitrogen are being stored in agricultural ditch soils, which is similar to that of surrounding agricultural land in terms of total carbon storage, but much higher than estimates of total nitrogen storage. Our study of six roadside ditches in an eastern Iowa watershed documented the soil chemistry, morphology, and sediment accumulation that occurred since ditch construction. Further research is needed to develop a better understanding of how the soil and water conditions in the ditches related to the watershed areas that feed them.

20.
J Patient Saf ; 15(4): e64-e69, 2019 12.
Artículo en Inglés | MEDLINE | ID: mdl-28820796

RESUMEN

OBJECTIVES: A culture-of-safety survey of our hospital staff revealed fear-based reluctance to question those in authority. We aimed to examine provider approachability (words and actions that promote trust and reduce or eliminate fear of interaction). METHODS: Providers and staff completed an anonymous facility-wide survey (survey 1) regarding perceptions of provider approachability. Results were safely communicated to providers, and improvement resources were offered. A follow-up survey (survey 2 [S2]) was performed. RESULTS: The survey participation rate was 59% (389/658). Eighty-four percent of providers had improved scores in S2. Mean top-box scores improved from 0.63 to 0.76 (P < .001). Providers deemed less approachable by nonprovider staff were also deemed less approachable by their peers (r = 0.82; survey 1). Forty-four percent reported improvement in the safety culture in S2. Twenty-eight percent of providers reported making efforts to improve how they were perceived by others. CONCLUSIONS: Provider approachability surveys are a safe, effective method of assessing and encouraging positive interactions that promote trust and influence positive communication. The process created an opportunity to identify and assist providers who were less approachable.


Asunto(s)
Comunicación , Hospitales , Cultura Organizacional , Seguridad del Paciente , Personal de Hospital , Administración de la Seguridad , Actitud del Personal de Salud , Miedo , Humanos , Liderazgo , Médicos , Poder Psicológico , Encuestas y Cuestionarios , Confianza
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