More Like this

1. Insights on agricultural nitrate leaching from soil block mesocosms

   https://doi.org/10.1002/jeq2.20586  

   Loper, Holly; Tenesaca, Carlos; Pederson, Carl; Helmers, Matthew J; Crumpton, William G; Lemke, Dean; Hall, Steven J (July 2024, Journal of Environmental Quality)

   Abstract Quantifying nitrate leaching in agricultural fields is often complicated by inability to capture all water draining through a specific area. We designed and tested undisturbed soil monoliths (termed “soil block mesocosms”) to achieve complete collection of drainage. Each mesocosm measures 1.5 m × 1.5 m × 1.2 m and is enclosed by steel on the sides and bottom with a single outlet to collect drainage. We compared measurements from replicate mesocosms planted to corn (Zea maysL.) with a nearby field experiment with tile‐drained plots (“drainage plots”), and with drainage from nearby watersheds from 2020 through 2022 under drought conditions. Annual mesocosm drainage volumes were 6.5–24.6 cm greater than from the drainage plots, likely because the mesocosms were isolated from the subsoil and could not store groundwater below the drain depth, whereas the drainage plots accumulated infiltration as groundwater. Thus, we obtained consistent nitrate leaching measurements from the mesocosms even when some drainage plots yielded no water. Despite drainage volume differences, mean flow‐weighted nitrate concentrations were similar between mesocosms and drainage plots in 2 of 3 years. Mesocosm annual drainage volume was 8.7 cm lower to 16.7 cm higher than watershed drainage, likely due to lagged influences of groundwater. Corn yields were lower in mesocosms than drainage plots in 2020, but with irrigation, yields were similar in subsequent years. Mean 2020 surface soil moisture and temperature were similar between the mesocosms and nearby fields. Based on these comparisons, the mesocosms provide a robust method to measure nitrate leaching with lower variability than field plots. 

   more » « less
2. Long Short-Term Memory Based Subsurface Drainage Control for Rainfall-Induced Landslide Prevention

   https://doi.org/10.3390/geosciences12020064  

   Biniyaz, Aynaz; Azmoon, Behnam; Sun, Ye; Liu, Zhen (February 2022, Geosciences)

   Subsurface drainage has been widely accepted to mitigate the hazard of landslides in areas prone to flooding. Specifically, the use of drainage wells with pumping systems has been recognized as an effective short-term solution to lower the groundwater table. However, this method has not been well considered for long-term purposes due to potentially high labor costs. This study aims to investigate the idea of an autonomous pumping system for subsurface drainage by leveraging conventional geotechnical engineering solutions and a deep learning technique—Long-Short Term Memory (LSTM)—to establish a geotechnical cyber-physical system for rainfall-induced landslide prevention. For this purpose, a typical soil slope equipped with three pumps was considered in a computer simulation. Forty-eight cases of rainfall events with a wide range of varieties in duration, total rainfall depths, and different rainfall patterns were generated. For each rainfall event, transient seepage analysis was performed using newly proposed Python code to obtain the corresponding pump’s flow rate data. A policy of water pumping for maintaining groundwater at a desired level was assigned to the pumps to generate the data. The LSTM takes rainfall event data as the input and predicts the required pump’s flow rate. The results from the trained model were validated using evaluation metrics of root mean square error (RMSE), mean absolute error (MAE), and R2. The R2-scores of 0.958, 0.962, and 0.954 for the predicted flow rates of the three pumps exhibited high accuracy of the predictions using the trained LSTM model. This study is intended to make a pioneering step toward reaching an autonomous pumping system and lowering the operational costs in controlling geosystems. 

   more » « less
3. A Model Analysis of the Tidal Engine That Drives Nitrogen Cycling in Coastal Riparian Aquifers

   https://doi.org/10.1029/2019WR025662  

   Wallace, Corey D.; Sawyer, Audrey H.; Barnes, Rebecca T.; Soltanian, Mohamad Reza; Gabor, Rachel S.; Wilkins, Michael J.; Moore, Myles T. (April 2020, Water Resources Research)

   Abstract In coastal rivers, tides facilitate surface water‐groundwater exchange and strongly coupled nitrification‐denitrification near the fluctuating water table. We used numerical fluid flow and reactive transport models to explore hydrogeologic and biogeochemical controls on nitrogen transport along an idealized tidal freshwater zone based on field observations from White Clay Creek, Delaware, USA. The capacity of the riparian aquifer to remove nitrate depends largely on nitrate transport rates, which initially increase with increasing tidal range but then decline as sediments become muddier and permeability decreases. Over the entire model reach, local nitrification provides a similar amount of nitrate as surface and groundwater contributions combined. More than half (~66%) of nitrate removed via denitrification is produced in situ, while the vast majority of remaining nitrate removed comes from groundwater sources. In contrast, average nitrate removal from surface water due to tidal pumping amounts to only ~1% of the average daily in‐channel riverine nitrate load or 1.77 kg of nitrate along the reach each day. As a result, tidal bank storage zones may not be major sinks for nitrate in coastal rivers but can act as effective sinks for groundwater nitrate. By extension, tidal bank storage zones provide a critical ecosystem service, reducing contributions of groundwater nitrate, which is often derived from septic tanks and fertilizers, to coastal rivers. 

   more » « less
4. Modern groundwater reaches deeper depths in heavily pumped aquifer systems

   https://doi.org/10.1038/s41467-022-32954-1  

   Thaw, Melissa; GebreEgziabher, Merhawi; Villafañe-Pagán, Jobel Y.; Jasechko, Scott (December 2022, Nature Communications)

   Abstract Deep groundwater is an important source of drinking water, and can be preferable to shallower groundwaters where they are polluted by surface-borne contaminants. Surface-borne contaminants are disproportionately common in ‘modern’ groundwaters that are made up of precipitation that fell since the ~1950s. Some local-scale studies have suggested that groundwater pumping can draw modern groundwater downward and potentially pollute deep aquifers, but the prevalence of such pumping-induced downwelling at continental scale is not known. Here we analyse thousands of US groundwater tritium measurements to show that modern groundwater tends to reach deeper depths in heavily pumped aquifer systems. These findings imply that groundwater pumping can draw mobile surface-borne pollutants to deeper depths than they would reach in the absence of pumping. We conclude that intensive groundwater pumping can draw recently recharged groundwater deeper into aquifer systems, potentially endangering deep groundwater quality. 

   more » « less
5. Real-Time Control of Exogenous Carbon Dosing in a Denitrifying Woodchip Bioreactor Treating Agricultural Drainage

   https://doi.org/10.1021/acsestengg.4c00020  

   Zhang, Zihao; Echavarria, Sofia; Sang, Yi; Weidman, Gianna R; Napp, Nils; Reid, Matthew C (June 2024, ACS ES&T Engineering)

   NA (Ed.)

   Nature-based treatment technologies such as denitrifying woodchip bioreactors (WBRs) are employed to manage nitrogen (N) pollution from agricultural nonpoint sources. Due to variability in environmental conditions like temperature and discharge, it is challenging to achieve consistent treatment effectiveness with these passive systems. To improve nitrate (NO3–) load reductions in a field-scale WBR in New York State during cool spring weather, we designed a system for controlled exogenous carbon (C) dosing, allowing rates of C dosing to respond in real time to changing discharge and NO3– concentrations. Treatment efficiencies for NO3–, acetate mass balances, and other bioreactor properties were monitored from April 5 to June 10, 2023. Biostimulation with 7.5 mg C/L acetate (assuming complete mixing of injected acetate with bioreactor pore water) increased NO3– removal rates up to 5-fold compared to a model-based scenario of baseline bioreactor performance, and were as high as 0.4 mg NO3––N L–1 h–1 while water temperatures were <12 °C. Increasing acetate concentrations beyond 7.5 mg C/L did not confer a clear improvement in NO3– removal rates. Cumulative N load reductions increased from 11.3% under the baseline scenario without C dosing to 24.1% with C dosing. The mass ratio of metabolized C to additional N removal was 2.5:1, although the total dosed C/N mass ratio was 5.1:1 due to incomplete acetate utilization in the reactor. We found evidence that C dosing could enhance the future release of dissolved organic N (DON) and dissolved organic C related to biofilm sloughing. The expense of acetate, with a cost efficiency of 86 USD/kg N, was the main cost driver of the real-time control approach. Our results demonstrate the potential of real-time control of C dosing to meaningfully improve nonpoint source N removal during cool spring conditions but also highlight opportunities for methods to improve acetate utilization efficiencies in order to improve the overall cost-effectiveness of the approach. 

   more » « less