•Burned watersheds had similar turbidity to unburned watersheds during spring runoff.•Burned watersheds were more susceptible to precipitation driven sedimentation.Watersheds with more erodible soils ...had larger turbidity increases following precipitation events than other watersheds.
In this work we explore watershed characteristics associated with increased turbidity following the 2013 West Fork Complex Fire (WFC) in southwest Colorado, USA with the goal of understanding the hydrologic and geomorphic controls on turbidity. Turbidity, precipitation, and stream discharge were measured from May to September in 2015 and 2016 in seven watersheds, four burned and three unburned. Slope, slope aspect, soil type, vegetation, and burn severity—as well as precipitation and discharge—were characterized as independent variables for each of the seven watersheds. During snowmelt-driven runoff from May to June, no significant difference in turbidity between burned and unburned watersheds was found. However, in results from July to September of both 2015 and 2016, burned watersheds had larger spikes in turbidity following precipitation events than unburned watersheds. In the watersheds with higher burn severity and poor vegetation recovery, positive correlations between total storm volume and turbidity existed, though short-term trends in Enhanced Vegetation Index (EVI) were not consistently correlated with turbidity changes with precipitation, nor were watershed slope and aspect alone. These results indicate that other drivers of turbidity in these burned watersheds, for example erodible soils, were more susceptible to precipitation than snowmelt due in part to processes like rain splash. Results from this work provide insight on characteristics that influence stream turbidity after a wildfire and can help watershed managers predict future wildfire impacts on water quality, the health of aquatic organisms, and water treatment infrastructure.
Diversity of lunar basalt characteristics is partly a consequence of lunar mantle heterogeneity. Although the cumulate mantle overturn hypothesis is the current standard model invoked to explain ...mantle asymmetries of unknown length scale in both compositional and geometrical space, successful petrological modeling of this mixing event requires a specific set of parameters not currently agreed upon. In contrast, surface basalt patterns may yield clues to both localized and nearside lunar interior structure.
Using two multidimensional data analysis approaches – principal component analysis (PCA) and K-means cluster analysis (KCA) – we report the patterns produced from basalt characteristics over changing spatial scales, from intra-site to inter-site to nearside. The data are sourced from a newly developed, self-contained database of lunar basalt characteristics (ApolloBasaltDB), which includes major element oxides, mineral modes, ages, and textures for petrological and statistical modeling. Through the simultaneous considerations of multiple basalt characteristics contained in the database, we find that terrestrial-based basalt classifications cannot adequately describe the complex and overlapping distribution patterns of major element oxides and mineral modes that define multiple distinct basalt groupings over multidimensional space. These patterns provide opportunities for alternative lunar basalt classification schemes. Our analyses suggest that Al2O3 volumetric content is more diverse inside the Procellarum KREEP Terrane rift boundary versus content for older Apollo samples in close proximity to the eastern arm of the same rift boundary. Northernmost basalt samples show increased pyroxene diversity. Easternmost sites suggest anti-correlations in modal ilmenite and plagioclase, based on major element oxide PCA biplots, while nearside analyses of either major element oxides or mineral modes similarly suggest plagioclase (and Al2O3) diversity comes at the expense of ilmenite (and TiO2) diversity. There is evidence to suggest that approximate mineral content can be extracted from major element oxide data based on correlative patterns between major element oxide PCA biplots and mineral mode PCA biplots. These patterns have implications for remote sensing missions in that onboard data manipulation may provide lithologic basalt vectors of interest.
•Machine learning provides lithologic basalt vectors through PCA biplots.•Major element patterns suggest the potential for alternative classification schemes.•Al2O3 diversity varies based on position relative to the Procellarum region.•Northern basalt samples show greater pyroxene diversity than those to the south.•Nearside plagioclase/Al2O3 diversity anticorrelates with ilmenite/TiO2 diversity.
The critical zone (CZ)-from treetops to groundwater-is an increasingly studied part of the earth system, where scientists study interactions between water, air, rock, soil, and life. Groundwater is ...both a boundary and an essential store in this integrated system, but is often not well considered in part because of the difficulty in accessing it and its slow movement relative to other parts of the system. Here, we describe some fundamental areas where groundwater hydrology is of fundamental importance to CZ science, including sustaining streamflow and vegetation, reacting with minerals to produce dissolved solutes and regolith, and influencing energy fluxes across the land-atmosphere interface. As the timing and type of precipitation change with climate, groundwater may play an even more important role in CZ processes as a sustainable water source for plants and streamflow. Many open questions also exist about the role of CZ processes on groundwater. Many data streams are needed and important to quantifying the integrated response of the CZ to groundwater and vice versa, but long-term data records are often incomplete or discontinued due to limited funding. We argue that the long timescales of processes that involve groundwater necessitate data collection efforts beyond typical federal funding timespans. Sustaining monitoring networks and developing new ones aimed at testing hypotheses related to slow-moving, groundwater-controlled CZ processes should be a scientific priority, and here we outline some open questions that we hope will motivate groundwater scientists to get involved in CZ science.
The scales of heterogeneity present in geologic media make modeling solute transport extremely challenging, even in idealized laboratory settings. The spatial Markov model (SMM) is an anomalous ...transport model that has been shown to accurately capture solute transport in a broad range of highly complex and heterogeneous hydrogeologic settings. However, to date, its applications are almost entirely limited to synthetic, numerically simulated systems due to the dense data required to parameterize it, which are typically unobtainable in real experiments. Here we apply a novel SMM inverse model that required only breakthrough curve measurements from laboratory transport experiments in zeolite‐packed columns that are known to display anomalous transport. We introduce an experimental design that allows for simultaneous measurements of breakthrough curves at multiple sampling locations within a one‐dimensional column setup. For the first time, we apply a fully parameterized SMM to successfully predict downgradient breakthrough curves. Results show that breakthrough curve prediction accuracy significantly improves when accounting for correlation effects in these experiments, a feature that the SMM is specifically designed to capture but that most traditional anomalous transport frameworks ignore. We do so for two different Péclet numbers, providing a parsimonious framework that can potentially account for correlation statistics in different field‐scale studies.
Key Points
We apply a fully parameterized spatial Markov model to predict breakthrough curves in zeolite clinoptilolite‐packed column experiments
Our experimental setup allows measurements of three breakthrough curves: two for model parameterization and one for validation
Incorporating velocity correlation into the CTRW significantly improves BTC prediction for experiments run at Peclet numbers 121 and 1210
Abstract
The spatial Markov model (SMM) is an upscaled Lagrangian model that effectively captures anomalous transport across a diverse range of hydrologic systems. The distinct feature of the SMM ...relative to other random walk models is that successive steps are correlated. To date, with some notable exceptions, the model has primarily been applied to data from high‐resolution numerical simulations and correlation effects have been measured from simulated particle trajectories. In real systems such knowledge is practically unattainable and the best one might hope for is breakthrough curves (BTCs) at successive downstream locations. We introduce a novel methodology to quantify velocity correlation from BTC data alone. By discretizing two measured BTCs into a set of arrival times and developing an inverse model, we estimate velocity correlation, thereby enabling parameterization of the SMM in studies where detailed Lagrangian velocity statistics are unavailable. The proposed methodology is applied to two synthetic numerical problems, where we measure all details and thus test the veracity of the approach by comparison of estimated parameters with known simulated values. Our results suggest that our estimated transition probabilities agree with simulated values and using the SMM with this estimated parameterization accurately predicts BTCs downstream. Our methodology naturally allows for estimates of uncertainty by calculating lower and upper bounds of velocity correlation, enabling prediction of a range of BTCs. The measured BTCs fall within the range of predicted BTCs. This novel method to parameterize the SMM from BTC data alone is quite parsimonious, thereby widening the SMM's practical applicability.
Key Points
We introduce a novel method to parameterize the SMM from breakthrough curve measurements
Our methodology naturally allows us to calculate upper and lower bound matrices, allowing uncertainty quantification
The SMM, parameterized using our method, accurately predicts breakthrough curves at multiple downstream locations
The western U.S. is experiencing shifts in recharge due to climate change, and it is currently unclear how hydrologic shifts will impact geochemical weathering and stream concentration–discharge ...(C–Q) patterns. Hydrologists often use C–Q analyses to assess feedbacks between stream discharge and geochemistry, given abundant stream discharge and chemistry data. Chemostasis is commonly observed, indicating that geochemical controls, rather than changes in discharge, are shaping stream C–Q patterns. However, few C–Q studies investigate how geochemical reactions evolve along groundwater flowpaths before groundwater contributes to streamflow, resulting in potential omission of important C–Q controls such as coupled mineral dissolution and clay precipitation and subsequent cation exchange. Here, we use field observations—including groundwater age, stream discharge, and stream and groundwater chemistry—to analyse C–Q relations in the Manitou Experimental Forest in the Colorado Front Range, USA, a site where chemostasis is observed. We combine field data with laboratory analyses of whole rock and clay x‐ray diffraction and soil cation‐extraction experiments to investigate the role that clays play in influencing stream chemistry. We use Geochemist's Workbench to identify geochemical reactions driving stream chemistry and subsequently suggest how climate change will impact stream C–Q trends. We show that as groundwater age increases, C–Q slope and stream solute response are not impacted. Instead, primary mineral dissolution and subsequent clay precipitation drive strong chemostasis for silica and aluminium and enable cation exchange that buffers calcium and magnesium concentrations, leading to weak chemostatic behaviour for divalent cations. The influence of clays on stream C–Q highlights the importance of delineating geochemical controls along flowpaths, as upgradient mineral dissolution and clay precipitation enable downgradient cation exchange. Our results suggest that geochemical reactions will not be impacted by future decreasing flows, and thus where chemostasis currently exists, it will continue to persist despite changes in recharge.
Conceptual diagram illustrating geochemical fluxes and controls driving stream concentration‐discharge patterns at Manitou. White arrows indicate reactions involving the dissolution of primary granitic minerals and precipitation of secondary clays. Red arrows indicate cation‐exchange reactions between bedrock and clays, and clays and the stream. Yellow arrows indicate dissolution of K+ and Na+ from bedrock to streamflow. We note that K+ can also be taken up by vegetation, but do not discuss it in the water‐rock interaction context of this study.
Buruli ulcer, an emerging disease caused by Mycobacterium ulcerans, largely affects poor rural populations in tropical countries. The environmental niche that supports this necrotizing bacterium is ...unclear. Here, water samples were collected from five communities within Ghana in the rainy season in 2011: four in the southern part of Ghana (three disease-endemic communities: Pokukrom, Betenase, and Ayanfuri, and one control: Kedadwen) and one non-endemic community (Nangruma) in the north.
Past studies of Buruli ulcer conclude that water quality is, in some way, closely related to the transmission of this disease. This work serves as a first step to explore links between Buruli ulcer incidence and water quality. More broadly, this research works toward identifying the environmental niche for M. ulcerans, providing characterization of water bodies hazardous to human health in at-risk communities.
Trace metals, thought to aid in the preferential growth of M. ulcerans, are present in higher concentrations in mining pits and stagnant pools than in other tested water bodies. Arsenic in particular could serve as a double threat for BU incidence: it could support the growth of M. ulcerans while suppressing immune systems, making the population more susceptible to disease. Few other differences between endemic and non-endemic communities exist, implying other variables such as human behavior may also control the onset of Buruli ulcer.
Streams impacted by historic mining activity are characterized by acidic pH, unique microbial communities, and abundant metal-oxide precipitation, all of which can influence groundwater-surface water ...exchange. We investigate how metal-oxide precipitates and hyporheic mixing mediate the composition of microbial communities in two streams receiving acid-rock and mine drainage near Silverton, Colorado, USA. A large, neutral pH hyporheic zone facilitated the precipitation of metal particles/colloids in hyporheic porewaters. A small, low pH hyporheic zone, limited by the presence of a low-permeability, iron-oxyhydroxide layer known as ferricrete, led to the formation of steep geochemical gradients and high dissolved-metal concentrations. To determine how these two hyporheic systems influence microbiome composition, we installed well clusters and deployed
microcosms in each stream to sample porewaters and sediments for 16S rRNA gene sequencing. Results indicated that distinct hydrogeochemical conditions were present above and below the ferricrete in the low pH system. A positive feedback loop may be present in the low pH stream where microbially mediated precipitation of iron-oxides contributes to additional clogging of hyporheic pore spaces, separating abundant, iron-oxidizing bacteria (Gallionella spp.) above the ferricrete from rare, low-abundance bacteria below the ferricrete. Metal precipitates and colloids that formed in the neutral pH hyporheic zone were associated with a more diverse phylogenetic community of nonmotile, nutrient-cycling bacteria that may be transported through hyporheic pore spaces. In summary, biogeochemical conditions influence, and are influenced by, hyporheic mixing, which mediates the distribution of micro-organisms and, thus, the cycling of metals in streams receiving acid-rock and mine drainage.
In streams receiving acid-rock and mine drainage, the abundant precipitation of iron minerals can alter how groundwater and surface water mix along streams (in what is known as the "hyporheic zone") and may shape the distribution of microbial communities. The findings presented here suggest that neutral pH streams with large, well-mixed hyporheic zones may harbor and transport diverse microorganisms attached to particles/colloids through hyporheic pore spaces. In acidic streams where metal oxides clog pore spaces and limit hyporheic exchange, iron-oxidizing bacteria may dominate and phylogenetic diversity becomes low. The abundance of iron-oxidizing bacteria in acid mine drainage streams has the potential to contribute to additional clogging of hyporheic pore spaces and the accumulation of toxic metals in the hyporheic zone. This research highlights the dynamic interplay between hydrology, geochemistry, and microbiology at the groundwater-surface water interface of acid mine drainage streams.
TIPT: The Tracer Injection Planning Tool González-Pinzón, Ricardo; Dorley, Jancoba; Singley, Joel ...
Environmental modelling & software : with environment data news,
October 2022, 2022-10-00, 2022-10-01, Letnik:
156, Številka:
C
Journal Article
Recenzirano
Despite their frequent use, there are few simple and readily accessible tools to help guide the logistical planning of tracer injections in streams and rivers. We combined the widely used ...advection-dispersion-reaction equation, peak concentration estimates based on a meta-analysis of hundreds of tracer injections carried out in streams and rivers, and simple mass balances in a dynamic Excel Workbook to 1) help users decide how much tracer mass should be added to achieve a specific dynamic concentration range that reduces known issues associated with breakthrough curve tail truncation, and 2) generate tables and graphs that can be readily used to plan the deployment of resources. Our Tracer Injection Planning Tool, TIPT, handles instantaneous and continuous tracer injections and assumes steady-state and uniform flow conditions, as well as first-order decay or production. While those assumptions do not strictly apply to natural streams and rivers, they help simplify the planning of tracer injections with a predictive ability that is disproportionally favorable with respect to the few inputs required. TIPT is a versatile, user-friendly, and graphical tool that can help design tracer injections and solute transport experiments that are more easily replicated within and across sites. Thus, TIPT contributes directly to advancing Integrated, Coordinated, Open, and Networked (ICON) principles. Similarly, TIPT can help generate datasets that more closely follow Findable, Accessible, Interoperable, and Reusable (FAIR) principles. We demonstrate the use of TIPT through two case studies featuring 1) a continuous injection in a 2nd order stream and 2) an instantaneous injection in a 7th order stream.
•TIPT can be used to plan instantaneous and continuous tracer injections.•TIPT help users decide tracer masses, mixing volumes, and sampling distances.•TIPT can be readily used to plan the deployment of human resources and equipment.
Three‐dimensional, multiphase simulations are used to analyze migration of methane leakage from a hydrocarbon wellbore. The objective is to evaluate the relevance and importance of coupling fast, ...advective transport of methane through fractures with slower, diffusive transport in the shale matrix below a freshwater aquifer on water quality assuming dual‐domain mass transfer (DDMT) in the reservoir by using the multiple interacting continua (MINC) as implemented in TOUGH2. The conceptual model includes a methane gas‐phase leak from a wellbore 20–30 m below an aquifer; multiphase, buoyant transport through shale partially saturated with brine; and, after methane leakage reaches groundwater, multiphase transport under varying lateral groundwater flow gradients. Results suggest that DDMT affects the rate of methane reaching groundwater by (i) providing long‐time secondary storage in less‐mobile pore space and (ii) creating larger methane‐plume diameters than those predicted by a single‐domain advection‐diffusion equation. Compared to models without DDMT, these factors combine to increase methane flow rates by an order of magnitude across the base of the aquifer 100 years after leakage begins. In the simulated aquifer, dissolution of gas‐phase plumes leads to bimodal aqueous‐phase methane breakthrough curves in a simulated water well 100 m downstream from leakage, with peak concentrations appearing decades after a 1‐year pulse of leakage. The major implication is that DDMT in the reservoir can explain newly discovered methane concentrations in water wells attributable to older leakage events. Therefore, remediation of abandoned or legacy wells with wellbore integrity loss may be necessary to prevent future incidents of groundwater contamination.
Key Points
Dual‐domain storage of methane leakage below groundwater leads to greater methane flow rates through time at the base of an aquifer
Persistent gas‐phase methane plumes in groundwater result in long‐lasting, bimodal aqueous‐phase methane breakthrough in downstream wells
Neglecting DDMT leads to the potential to underestimate stored methane that can reach downstream water wells decades after leakage ends
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