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1.
J Environ Qual ; 49(3): 675-687, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-33016383

RESUMO

Legacy phosphorus (P) in agricultural soils can be transported to surface waters via runoff and tile drainage, where it contributes to the development of harmful and nuisance algal blooms and hypoxia. However, a limited understanding of legacy P loss dynamics impedes the identification of mitigation strategies. Edge-of-field data from 41 agricultural fields in northwestern Ohio, USA, were used to develop regressions between legacy P concentrations (C) and discharge (Q) for two P fractions: total P (TP) and dissolved reactive P (DRP). Tile drainage TP concentration (CTP ) and DRP concentration (CDRP ) both increased as Q increased, and CTP tended to increase at a greater rate than CDRP . Surface runoff showed greater variation in C-Q regressions, indicating that the response of TP and DRP to elevated Q was field specific. The relative variability of C and Q was explored using a ratio of CVs (CVC /CVQ ), which indicated that tile drainage TP and DRP losses were chemodynamic, whereas losses via surface runoff demonstrated both chemodynamic and chemostatic behavior. The chemodynamic behavior indicated that legacy P losses were strongly influenced by variation in P source availability and transport pathways. In addition, legacy P source size influenced C, as demonstrated by a positive relationship between soil-test P and the CTP and CDRP in both tile drainage and surface runoff. Progress towards legacy P mitigation will require further characterization of the drivers of variability in CTP and CDRP , including weather-, soil-, and management-related factors.


Assuntos
Fósforo/análise , Movimentos da Água , Agricultura , Ohio , Solo
2.
J Environ Qual ; 49(5): 1370-1383, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33016447

RESUMO

Recent research on tile-drainage has placed emphasis on dissolved reactive phosphorus (DRP) delivery and transport pathways but less emphasis on particulate P (PP), resulting in its exclusion from agricultural water management models. In this study, we quantified the fluxes, mechanisms, and factors driving PP delivery into tiles through statistical analysis of a long-term hydrologic and water quality dataset. The dataset includes 5 yr of surface and tile discharge, total P (TP), DRP, total nitrogen (TN), and dissolved inorganic N concentrations from two edge-of-field study sites with contrasting soil and management practices. Hydrograph recession techniques were coupled with multiple linear regression for understanding hydrologic flow pathways, and empirical mode decomposition (EMD) time-series analysis was used to determine the significance of PP seasonality processes and the effect of management practices. The analysis of hydrologic flow pathways demonstrated that quickflow contributed 66 and 36% of subsurface discharge in the clay and loam sites, respectively. Phosphorus loading analysis showed that macropore flow plays a significant role in PP delivery to subsurface P loading and that PP significantly contributed to TP and DRP delivery; however, greater PP loadings were observed at the clay site despite greater subsurface discharge and soil test P levels at the loam site. Furthermore, PP delivery was significantly affected by environmental conditions and management practices. We highlight the efficacy of hydrograph recession analysis for identifying macropore and diffuse drainage, of P/N ratios to characterize sediment delivery mechanisms in tiles, and of EMD to detect management impacts on TP and DRP at the field scale.


Assuntos
Fósforo/análise , Movimentos da Água , Agricultura , Hidrologia , Solo
3.
Environ Monit Assess ; 192(4): 227, 2020 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-32157442

RESUMO

Crayfishes (Decapoda) are common inhabitants of agricultural headwater streams in the Midwestern USA that have been impacted by physical habitat degradation and contamination by agricultural pollutants. The frequency and severity of injuries within crayfish communities are indicators of crayfish aggression, which is influenced by physical, chemical, and biotic factors. Previous studies have not evaluated the relationships of the frequency and severity of crayfish injuries with physical habitat quality, water quality, and biotic factors within agricultural headwater streams. Understanding these relationships will assist with determining if crayfish injury variables can serve as an indicator of physical habitat quality or water quality in these small degraded streams. We sampled crayfishes, documented the frequency and type of injuries, and measured instream habitat and water chemistry in 2014 and 2015 within 12 agricultural headwater streams in Indiana, Michigan, and Ohio. We documented five native crayfish species from 1641 adult captures. The most abundant species were Faxonius rusticus, Faxonius immunis, and Faxonius propinquus. Linear mixed effect model analyses indicated that four crayfish injury response variables were positively correlated (p < 0.05) with crayfish density, physical habitat quality, and water velocity diversity and that crayfish injury response variables were more strongly correlated with crayfish density than physical habitat quality or water quality. Our results indicate that response variables describing the severity and frequency of crayfish injuries can be effective indicators of physical habitat quality in agricultural headwater streams.


Assuntos
Astacoidea , Rios , Qualidade da Água , Animais , Ecossistema , Monitoramento Ambiental , Indiana , Michigan , Ohio
4.
Environ Sci Technol ; 54(1): 176-183, 2020 01 07.
Artigo em Inglês | MEDLINE | ID: mdl-31763838

RESUMO

Internal phosphorus (P) in sediments plays an important role in the nutrient dynamics of lakes, sometimes long after external loads have been reduced. Similarly, internal P sources may drive the nutrient dynamics of small agricultural streams that drain to larger rivers and lakes, despite best management practices intended to reduce external P loads from adjacent fields. Here, internal P concentrations were measured with sequential extraction on cores collected in spring and summer from two small agricultural streams in the drainage basin of Lake Erie, a large, eutrophic lake experiencing increasing SRP loads. Average total extractable P concentrations were similar to within 5% during spring and summer, but mobile P binding fractions nearly doubled in summer, possibly due to accelerated rates of organic matter mineralization or iron reduction beneath suboxic, stagnant surface waters. One site had chronically greater internal P concentrations by 25-75%, despite the implementation of best management practices such as grass buffers. The site also had more aquatic vegetation that restricted the flow, less dissolved oxygen in surface water, and greater organic matter in sediments during both seasons, suggesting that variations in hydrology, sediment composition, and vegetation influence hot spots of P retention throughout small agricultural streams.


Assuntos
Lagos , Rios , Agricultura , Monitoramento Ambiental , Sedimentos Geológicos , Fósforo
5.
J Environ Qual ; 49(6): 1585-1598, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33459397

RESUMO

Channelized agricultural headwater streams are common throughout agricultural watersheds in the midwestern United States. Understanding fish-habitat relationships within these streams will provide information that can assist with developing conservation and restoration strategies for these degraded streams. From spring 2006 to fall 2010, we collected fishes and measured riparian habitat, instream habitat, and water chemistry variables from seven sites in Cedar Creek, Indiana, and 14 sites in Upper Big Walnut Creek, Ohio. We found that fish community structure was more strongly correlated with instream habitat than riparian habitat or water chemistry in both watersheds. We also observed interrelationships among instream habitat, watershed size, and fish communities within both watersheds that suggest that the hydrological changes that occur with increasing watershed size are the underlying factor for fish community changes that occur with increasing watershed size. Our results suggest that conservation and restoration efforts within channelized agricultural headwater streams in the midwestern United States, where nutrients and herbicide concentrations are low, need to address physical habitat degradation to positively influence fish community structure.


Assuntos
Ecossistema , Rios , Animais , Peixes , Meio-Oeste dos Estados Unidos , Ohio
6.
J Neural Eng ; 17(1): 016014, 2019 12 23.
Artigo em Inglês | MEDLINE | ID: mdl-31648208

RESUMO

OBJECTIVE: We have demonstrated previously that microstimulation in the dorsal root ganglia (DRG) can selectively evoke activity in primary afferent neurons in anesthetized cats. This study describes the results of experiments focused on characterizing the postural effects of DRG microstimulation in awake cats during quiet standing. APPROACH: To understand the parameters of stimulation that can affect these postural shifts, we measured changes in ground reaction forces (GRF) while varying stimulation location and amplitude. Four animals were chronically implanted at the L6 and L7 DRG with penetrating multichannel microelectrode arrays. During each week of testing, we identified electrode channels that recruited primary afferent neurons with fast (80-120 m s-1) and medium (30-75 m s-1) conduction velocities, and selected one channel to deliver current-controlled biphasic stimulation trains during quiet standing. MAIN RESULTS: Postural responses were identified by changes in GRFs and were characterized based on their magnitude and latency. During DRG microstimulation, animals did not exhibit obvious signs of distress or discomfort, which could be indicative of pain or aversion to a noxious sensation. Across 56 total weeks, 13 electrode channels evoked behavioral responses, as detected by a significant change in GRF. Stimulation amplitude modulated the magnitude of the GRF responses for these 13 channels (p  < 0.001). It was not possible to predict whether or not an electrode would drive a behavioral response based on information including conduction velocity, recruitment threshold, or the DRG in which it resided. SIGNIFICANCE: The distinct and repeatable effects on the postural response to low amplitude (<40 µA) DRG microstimulation support that this technique may be an effective way to restore somatosensory feedback after neurological injuries such as amputation.


Assuntos
Gânglios Espinais/fisiologia , Equilíbrio Postural/fisiologia , Vigília/fisiologia , Animais , Gatos , Estimulação Elétrica/instrumentação , Estimulação Elétrica/métodos , Masculino , Microeletrodos
7.
J Environ Qual ; 46(2): 466-469, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28380548

RESUMO

The Western Lake Erie Basin (WLEB) was inundated with precipitation during June and July 2015 (two to three times greater than historical averages), which led to significant nutrient loading and the largest in-lake algal bloom on record. Using discharge and concentration data from three spatial scales (0.18-16,000 km), we contrast the patterns in nitrate (NO-N) and dissolved reactive phosphorus (DRP) concentration dynamics and discuss potential management implications. Across all scales, NO-N concentration steadily declined with each subsequent rainfall event as it was flushed from the system. In contrast, DRP concentration persisted, even on soils at or below agronomic P levels, suggesting that legacy P significantly contributes to nutrient loads in the WLEB. These findings highlight the need to revisit current P fertility recommendations and soil testing procedures to increase P fertilizer use efficiency and to more holistically account for legacy P.


Assuntos
Eutrofização , Fósforo/química , Monitoramento Ambiental , Fertilizantes , Lagos
8.
J Environ Qual ; 46(6): 1413-1423, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-29293822

RESUMO

The contribution of macropore flow to phosphorus (P) loadings in tile-drained agricultural landscapes remains poorly understood at the field scale, despite the recognized deleterious impacts of contaminant transport via macropore pathways. A new subroutine that couples existing matrix-excess and matrix-desiccation macropore flow theory and a modified P routine is implemented in the Agricultural Policy Environmental eXtender (APEX) model. The original and modified formulation were applied and evaluated for a case study in a poorly drained field in Western Ohio with 31 months of surface and subsurface monitoring data. Results highlighted that a macropore subroutine in APEX improved edge-of-field discharge calibration and validation for both tile and total discharge from satisfactory and good, respectively, to very good and improved dissolved reactive P load calibration and validation statistics for tile P loads from unsatisfactory to very good. Output from the calibrated macropore simulations suggested median annual matrix-desiccation macropore flow contributions of 48% and P load contributions of 43%, with the majority of loading occurring in winter and spring. While somewhat counterintuitive, the prominence of matrix-desiccation macropore flow during seasons with less cracking reflects the importance of coupled development of macropore pathways and adequate supply of the macropore flow source. The innovative features of the model allow for assessments of annual macropore P contributions to tile drainage and has the potential to inform P site assessment tools.


Assuntos
Agricultura , Modelos Teóricos , Fósforo/análise , Poluentes da Água/análise , Monitoramento Ambiental , Ohio , Movimentos da Água
9.
J Environ Qual ; 46(6): 1306-1313, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-29293845

RESUMO

The Phosphorus Index (PI) has been the cornerstone for phosphorus (P)-based management and planning over the past twenty years, yet field-scale evaluation of many state PIs has been limited. In this study, P loads measured in surface runoff and tile discharge from 40 agricultural fields in Ohio with prevailing management practices were used to evaluate the Ohio PI. Annual P loads were highly variable among fields (dissolved reactive P: 0.03-4.51 kg ha, total P: 0.03-6.88 kg ha). Both measured annual dissolved reactive P ( = 0.36, < 0.001) and total P ( = 0.25, < 0.001) loads were significantly related to Ohio PI score. The relationship between measured load and PI score substantially improved when averaged annual field values were used (dissolved reactive P: = 0.71, total P: = 0.73), indicating that the Ohio PI should be utilized to evaluate average annual risk of P loss, rather than as an annual risk tool. Comparison between the Ohio PI and other established local and national metrics resulted in large differences in potential P management recommendations for the monitored fields. In the near term, revision of Ohio PI risk categories and management recommendations using local P loading thresholds is needed. To meet the minimum criteria for state PI tools, future research efforts should focus on using measured field data (i) to incorporate new input factors (i.e., P application timing and leaching potential) into the Ohio PI, and (ii) to calibrate and validate the Ohio PI to provide better P risk assessments and management recommendations.


Assuntos
Fósforo/análise , Qualidade da Água , Agricultura , Monitoramento Ambiental , Ohio , Medição de Risco
10.
J Environ Qual ; 44(2): 467-85, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26023966

RESUMO

Phosphorus (P) loss from agricultural fields and watersheds has been an important water quality issue for decades because of the critical role P plays in eutrophication. Historically, most research has focused on P losses by surface runoff and erosion because subsurface P losses were often deemed to be negligible. Perceptions of subsurface P transport, however, have evolved, and considerable work has been conducted to better understand the magnitude and importance of subsurface P transport and to identify practices and treatments that decrease subsurface P loads to surface waters. The objectives of this paper were (i) to critically review research on P transport in subsurface drainage, (ii) to determine factors that control P losses, and (iii) to identify gaps in the current scientific understanding of the role of subsurface drainage in P transport. Factors that affect subsurface P transport are discussed within the framework of intensively drained agricultural settings. These factors include soil characteristics (e.g., preferential flow, P sorption capacity, and redox conditions), drainage design (e.g., tile spacing, tile depth, and the installation of surface inlets), prevailing conditions and management (e.g., soil-test P levels, tillage, cropping system, and the source, rate, placement, and timing of P application), and hydrologic and climatic variables (e.g., baseflow, event flow, and seasonal differences). Structural, treatment, and management approaches to mitigate subsurface P transport-such as practices that disconnect flow pathways between surface soils and tile drains, drainage water management, in-stream or end-of-tile treatments, and ditch design and management-are also discussed. The review concludes by identifying gaps in the current understanding of P transport in subsurface drains and suggesting areas where future research is needed.

11.
J Environ Qual ; 44(2): 495-502, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26023968

RESUMO

The midwestern United States offers some of the most productive agricultural soils in the world. Given the cool humid climate, much of the region would not be able to support agriculture without subsurface (tile) drainage because high water tables may damage crops and prevent machinery usage in fields at critical times. Although drainage is designed to remove excess soil water as quickly as possible, it can also rapidly transport agrochemicals, including phosphorus (P). This paper illustrates the potential importance of tile drainage for P transport throughout the midwestern United States. Surface runoff and tile drainage from fields in the St. Joseph River Watershed in northeastern Indiana have been monitored since 2008. Although the traditional concept of tile drainage has been that it slowly removes soil matrix flow, peak tile discharge occurred at the same time as peak surface runoff, which demonstrates a strong surface connection through macropore flow. On our research fields, 49% of soluble P and 48% of total P losses occurred via tile discharge. Edge-of-field soluble P and total P areal loads often exceeded watershed-scale areal loadings from the Maumee River, the primary source of nutrients to the western basin of Lake Erie, where algal blooms have been a pervasive problem for the last 10 yr. As farmers, researchers, and policymakers search for treatments to reduce P loading to surface waters, the present work demonstrates that treating only surface runoff may not be sufficient to reach the goal of 41% reduction in P loading for the Lake Erie Basin.

12.
J Environ Qual ; 44(2): 486-94, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26023967

RESUMO

Phosphorus (P) transport from agricultural fields continues to be a focal point for addressing harmful algal blooms and nuisance algae in freshwater systems throughout the world. In humid, poorly drained regions, attention has turned to P delivery through subsurface tile drainage. However, research on the contributions of tile drainage to watershed-scale P losses is limited. The objective of this study was to evaluate long-term P movement through tile drainage and its manifestation at the watershed outlet. Discharge data and associated P concentrations were collected for 8 yr (2005-2012) from six tile drains and from the watershed outlet of a headwater watershed within the Upper Big Walnut Creek watershed in central Ohio. Results showed that tile drainage accounted for 47% of the discharge, 48% of the dissolved P, and 40% of the total P exported from the watershed. Average annual total P loss from the watershed was 0.98 kg ha, and annual total P loss from the six tile drains was 0.48 kg ha. Phosphorus loads in tile and watershed discharge tended to be greater in the winter, spring, and fall, whereas P concentrations were greatest in the summer. Over the 8-yr study, P transported in tile drains represented <2% of typical application rates in this watershed, but >90% of all measured concentrations exceeded recommended levels (0.03 mg L) for minimizing harmful algal blooms and nuisance algae. Thus, the results of this study show that in systematically tile-drained headwater watersheds, the amount of P delivered to surface waters via tile drains cannot be dismissed. Given the amount of P loss relative to typical application rates, development and implementation of best management practices (BMPs) must jointly consider economic and environmental benefits. Specifically, implementation of BMPs should focus on late fall, winter, and early spring seasons when most P loading occurs.

13.
Environ Toxicol Chem ; 32(3): 684-91, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23233324

RESUMO

Chlorothalonil concentrations exceeding acute toxicity levels for certain organisms have been measured in surface water discharge events from managed turf watersheds. The duration of exceedence and the timing of these events related to precipitation/runoff and time since application, however, have not been explored. Chlorothalonil concentrations were measured from discharge waters draining a managed turf watershed in Duluth, Minnesota, USA, between 2003 and 2009. The median chlorothalonil concentration was 0.58 µg/L. Approximately 2% of all measured concentrations exceeded the 7.6 µg/L median lethal concentration (LC50) acute toxicity level for rainbow trout. One-twentieth the LC50 concentration, equivalent to the level of concern (0.38 µg/L) for endangered species, was exceeded 31% of the time during the present study. The concentrations that exceeded the LC50 threshold were associated with eight rainfall/runoff events. Low dose exposures are a more important biological concern than acute occurrences. Exceedence concentrations associated with acute effects were significantly (p < 0.05) correlated to time since application and were measured only in the fall following extensive application. A conflict exists between the transportability of chlorothalonil as suggested by its chemical properties and the data collected in the present study. With respect to course-wide golf course application, avoiding application until after the major autumn rainfall period but before the first snow coverage is recommended to reduce occurrence of chlorothalonil concentrations that exceed toxic levels associated with acute and chronic levels of concern.


Assuntos
Monitoramento Ambiental/métodos , Fungicidas Industriais/análise , Moluscocidas/análise , Nitrilos/análise , Poluentes Químicos da Água/análise , Animais , Fungicidas Industriais/toxicidade , Dose Letal Mediana , Minnesota , Moluscocidas/toxicidade , Nitrilos/toxicidade , Oncorhynchus mykiss , Medição de Risco , Poluentes Químicos da Água/toxicidade
14.
J Environ Qual ; 40(4): 1273-80, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21712597

RESUMO

Golf courses are vulnerable to phosphate (PO) and pesticide loss by infiltration of the sandy, porous grass rooting media used and through subsurface tile drainage. In this study, an effort was made to remove PO, chlorothalonil, mefenoxam, and propiconazole in a golf green's drainage water with a filter blend comprised of industrial byproducts, including granulated blast furnace slag, cement kiln dust, silica sand, coconut shell-activated carbon, and zeolite. To test this filter media, two 6-h storm events were simulated by repeat irrigation of the golf green after PO and pesticide application. Drainage flows ranged from 0.0034 to 0.6433 L s throughout the course of the simulations. A significant decrease in the chlorothalonil load for the experimental run (with filter media) was observed compared with the control (without filter media) ( < 0.05). In general, percent reductions in chlorothalonil were very high (>80%) near peak flows. In contrast, filter media was not effective in removing PO, mefenoxam, or propiconazole ( > 0.05). Instead, it appears that the filter blend added PO to the effluent above flow rates of 0.037 L s. Overall, flow rate, the amount of filter media used, and contaminant properties may have influenced the filter media's ability to remove contaminants. More research is needed to determine the optimal blend and configuration for the filter media to remove significant amounts of all contaminants investigated.


Assuntos
Recuperação e Remediação Ambiental/métodos , Filtração , Praguicidas/análise , Fósforo/análise , Alanina/análogos & derivados , Alanina/análise , Golfe , Resíduos Industriais , Nitrilos/análise , Fosfatos/análise , Poaceae , Chuva , Texas , Triazóis/análise , Poluição Química da Água/prevenção & controle
15.
J Water Health ; 8(3): 577-92, 2010 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-20375487

RESUMO

Headwater streams constitute the majority of watersheds in the United States and many in the midwest have been channelized for agricultural drainage. Public health implications of water chemistry and aquatic insects within channelized and unchannelized headwater streams have not been explored. We sampled water chemistry and aquatic insects in two channelized and two unchannelized headwater streams in central Ohio from December 2005 until November 2008. Maximum concentrations of ammonium, nitrate plus nitrite, and chlorothalonil were greater in channelized streams. Nitrate plus nitrite and atrazine also exceeded drinking water standards more often in channelized streams. Maximum concentrations of simazine and the percentage of times it exceeded the drinking water standards were greater in unchannelized streams. The predicted hazard potential of nutrient and pesticide mixtures was greater in channelized streams. Mosquito abundance did not differ between stream types. Chironomid abundance was greater in channelized streams. Biting dipterans did not exhibit consistent abundance trends and only differed between stream types in the summer and fall. Our results suggest that if whole stream uptake of nutrients and pesticides is minimal in channelized headwater streams then nutrient and pesticide inputs from these streams may impact downstream drinking water sources. Our results also suggest channelized and unchannelized headwater streams are not serving as a significant source of mosquitoes.


Assuntos
Água Doce/química , Água Doce/parasitologia , Insetos , Poluentes Químicos da Água/análise , Animais , Monitoramento Ambiental , Humanos , Ohio , Praguicidas/análise , Movimentos da Água
16.
J Environ Qual ; 38(6): 2402-11, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19875796

RESUMO

Pesticides applied to turf grass have been detected in surface waters raising concerns of their effect on water quality and interest in their source, hydrological transport and use of models to predict transport. TurfPQ, a pesticide runoff model for turf grass, predicts pesticide transport but has not been rigorously validated for larger storms. The objective of this study was to determine TurfPQ's ability to accurately predict the transport of pesticides with runoff following more intense precipitation. The study was conducted with creeping bentgrass [Agrostis palustris Huds.] turf managed as a golf course fairway. A pesticide mixture containing dicamba, 2,4-D, MCPP, flutolanil, and chlorpyrifos was applied to six adjacent 24.4 by 6.1 m plots. Controlled rainfall simulations were conducted using a rainfall simulator designed to deliver water droplets similar to natural rain. Runoff flow rates and volume were measured and water samples were collected for analysis of pesticide concentrations. Six simulations yielded 13 events with which to test TurfPQ. Measured mean percentage of applied pesticide recovered in the runoff for dicamba, 2,4-D, MCPP, flutolanil, and chlorpyrifos was 24.6, 20.7, 14.9, 5.9, and 0.8%, respectively. The predicted mean values produced by TurfPQ were 13.7, 15.6, 15.5, 2.5, and 0.2%, respectively. The model produced correlations of r=0.56 and 0.64 for curve number hydrology and measured hydrology, respectively. Comparisons of the model estimates with our field observations indicate that TurfPQ under predicted pesticide runoff during 69.5+/-11.4 mm, 1.9+/-0.2 h, simulated storms.


Assuntos
Modelos Químicos , Praguicidas/análise , Poluição Química da Água/análise , Carbono/análise , Simulação por Computador , Meia-Vida , Compostos Orgânicos/análise , Poaceae , Chuva
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