John J. Sloan

Rivers are major pathways for microplastic transport, yet controls on microplastic storage across different riverine environments remain poorly constrained, particularly in managed systems. Here, we quantify microplastic abundance and characteristics in water and sediments from the Kaskaskia River (Illinois), a regulated tributary of the Mississippi River, with a specific focus on differences between main channel and backwater environments. Water and sediment samples were collected from three locations downstream of Carlyle Lake and analyzed for microplastic concentration, morphology, size, and color. Microplastic (MP) concentrations averaged 2.9 MP/L in the water column and 34.4 MP/kg in sediments, with clear fibers dominating both matrices. Contrary to expectations that low‐energy backwaters would act as preferential sinks, sediment microplastic concentrations were significantly ( p < 0.05) higher in main channel environments in comparison to adjacent backwaters. In contrast, microplastic concentrations in water did not vary by site, riverine environment, or depth, and were not correlated with total suspended solids ( p > 0.05), indicating a decoupling between microplastic and suspended sediment transport. Microplastics in backwater sediments were larger than those in the main channel ( p < 0.05), suggesting enhanced fragmentation in high‐energy main channel environments. These results demonstrate that in regulated, low‐gradient rivers, main channels can function as microplastic storage zones, rather than solely as transport pathways, and backwaters may consistently serve as ecological refuges. Our findings emphasize the importance of cross‐sectional sampling and environment‐specific assessments to accurately characterize fluvial microplastic dynamics and inform freshwater monitoring and management strategies across all riverine environments.

Reservoirs are vital tools for managing riverine water resources but also influence water quality through in‐lake nutrient (i.e., nitrogen [N] and phosphorus [P]) dynamics that affect downstream ecosystems. This study presents a multiscale spatiotemporal characterization of water quality in Carlyle Lake, an agriculturally impacted reservoir in Illinois, United States. We combined manual spatial surveys (2016–2017) with high frequency buoy data (2016–2019) to reveal the distinct biogeochemical processes within the reservoir. The upper subbasin had large subdaily fluctuations and high levels of turbidity and nitrate (NO ₃ ⁻ ‐N) relative to the lower subbasin, reflecting longitudinal sedimentation and denitrification. In contrast, the lower subbasin exhibited high phosphate (PO ₄ ³⁻ ‐P) that often exceeded the 0.05 mg/L guideline, consistent with sediment‐driven P release under low dissolved oxygen (DO) and warm conditions. Vertical sampling profiles demonstrated occasional hypoxia near the sediment–water interface in the lower subbasin that coincided with elevated PO ₄ ³⁻ ‐P levels, while homogeneous temperature and NO ₃ ⁻ ‐N profiles with depth indicated limited stratification. Nutrient flux estimates showed that Carlyle Lake acted as a N sink (i.e., 43%–77% NO ₃ ⁻ ‐N reduction) and P source (i.e., 40%–50% PO ₄ ³⁻ ‐P release). Our high frequency monitoring data identified a 27–32‐day NO ₃ ⁻ ‐N transit time across the reservoir, highlighting the value of continuous data for capturing nutrient dynamics to inform water management strategies for systems that are under increasing pressure from agricultural practices and climate variability.

Dijkstra ML, Corcoran MJ, Sloan JJ, and Lutz BL. 2020. Assessing phosphorus distribution and bioavailability in Lake Decatur, IL. Lake Reserv Manage. XX:XXX–XXX. In freshwater systems phosphorus is generally considered to be the limiting nutrient for algal growth, but not all phosphorus species are equally bioavailable to algae. Furthermore, the ratio of bioavailable to nonavailable phosphorus, impacted by in-lake processes and tributary loadings, is known to vary. Limited information, however, is available regarding this variation. Here we present the results from our investigation into spatial patterns in phosphorus concentration and bioavailability for 12 sites on Lake Decatur, a eutrophic 6-basin reservoir in central Illinois. We found that soluble phosphorus was distributed fairly homogeneously among basins, but the particulate fraction varied significantly (representing ∼11% and ∼89%, of phosphorus present in the system, respectively). Bioavailable phosphorus was also not evenly distributed throughout the reservoir. The highest concentration of bioavailable phosphorus (0.063 mg/L) was found in a basin that receives return flow of supernatant water from the dredged sediments dewatering pond. The reservoir’s outflow basin, which has more tributaries and coastline than the other 5 basins, had a similar concentration (0.061 mg/L). Bioavailable phosphorus concentrations in the other basins had a mean of 0.024 mg/L, making these less susceptible to algal blooms and subsequent water quality degradation. Current monitoring and reduction efforts regarding nitrogen (to remediate blooms in the Gulf of Mexico) need to (more fully) include phosphorus. Site-specific kinetics, presented in this work, will support model (re)development to improve the selection and prioritization of effective strategies to remove/control the limiting nutrient in Lake Decatur.

Monitoring of inland water quality is of significant importance due to the increase in water quality related issues, especially within the Midwestern United States. Traditional monitoring techniques, although highly accurate, are vastly insufficient in terms of spatial and temporal coverage. Using a virtual constellation by harmonizing Landsat-8 and Sentinel-2 data a high temporal frequency dataset can be created at a relatively fine spatial scale. In this study, we apply a novel deep learning method for the estimation of blue-green algae (BGA), chlorophyll-α (Chl), fluorescent dissolved organic matter (fDOM), dissolved oxygen (DO), specific conductance (SC), and turbidity. The developed model is evaluated against previously studied machine learning methods and found to outperform multiple linear regression (MLR), support vector machine regression (SVR), and extreme learning machine regression (ELR) generating R² of 0.91 for BGA, 0.88, 0.89, 0.93, 0.87, and 0.84 for Chl, DO, SC, and turbidity respectfully. This model is then applied to all available data ranging from 2013–2018 and time series for each variable were generated for four selected waterbodies. We then use the Empirical Data Analytics (EDA) anomaly detection method on the time series to identify abnormal data points. Upon further analysis, the EDA method successfully identifies abnormal events in water quality. Our results also demonstrate strong correlation between non-optically active variables such as SC with Chl and fDOM. The framework developed in this study represents an efficient and accurate empirical method for inland water quality monitoring at the regional scale.

Clinoptilolite zeolite coated with hydrous ferric oxide (FeZeo) may improve nutrient retention when blended into sand-based root zones. The objective of this study was to evaluate the effects of nutrient-charged FeZeo on nitrogen (N) and phosphorus (P) leaching and on growth of creeping bentgrass (Agrostis palustris Huds.). FeZeo was pre-loaded with 255 mg kg⁻¹ N and 224 mg kg⁻¹ P using a water-soluble fertilizer. Then, root zone mixes (RZM) containing 0, 5, 10, and 20% fertilizer-loaded FeZeo were packed into lysimeters and seeded with creeping bentgrass at a rate of 49 kg ha⁻¹. RZMs with 20% FeZeo received no additional fertilization whereas those containing 0, 5, and 10% FeZeo received four additional fertilizer applications during the next 8 months so that the cumulative N and P rates for every lysimeter were equivalent to 149 kg ha⁻¹ and 131 kg ha⁻¹, respectively. Lysimeters were irrigated every 2 to 3 days and leachate was collected and analyzed. Compared to putting green sand, the 5, 10 and 20% FeZeo treatments reduced the quantity of leached P by 96.2%, 91.3%, and 90.3%, and the quantity of leached N by 88.6%, 82.7% and 76.7%, respectively. Results suggest that pre-fertilized FeZeo applied to sand-based root zone mixes at 5 to 10% can significantly reduce nutrient leaching while maintaining acceptable plant growth, but higher rates of FeZeo can reduce plant growth. An alternative use for higher rates of FeZeo might include a filtering material for agricultural tile drainage. Abbreviations: cation exchange capacity (CEC), electrical conductivity (EC), iron-oxide coated clinoptilolite zeolite FeZeo, nitrogen (N), RZM, root zone mix

Reservoirs along rivers have the potential to act as nutrient sinks (e.g., denitrification and sedimentation) or sources (e.g., decomposition and redox changes), potentially reducing or enhancing nutrient loads downstream. This study investigated the spatial and temporal variability of water and lakebed sediment chemistry for an agricultural reservoir, Carlyle Lake (Illinois, U.S.), to assess the role of sediments as nutrient sinks or sources. Samples were collected across the reservoir over a 2‐year period. We measured N‐ and P‐species in water at the sediment‐water interface, in sediment porewaters, and loosely bound to sediment exchange sites. Total N, total P, total C, organic matter, Fe, Mn, and grain size were measured in bulk sediments. We observed a strong gradient in sedimentary total N, total P, total C, organic matter, and metals along the reservoir, with the lowest concentrations at the river mouth and the highest concentrations near the dam. Additionally, we did a long‐term nutrient mass balance using historical water quality data for streams entering and exiting the reservoir and the reservoir itself. Mass balance calculations showed that Carlyle Lake, on average, removed 2,738 Mg N/year and released 121 Mg P/year over the multidecadal observation period. While N was consistently removed from the system over time, P was initially stored in, but later released from, the reservoir. The subsequent release of legacy P from the reservoir led to higher outgoing, compared with incoming, P loads. Thus, reservoirs in intensively managed landscapes can act as sinks for N but sources for P over decadal timescales.

Disturbed soils might be improved by increasing organic matter content. The objective of this study was to determine if a large application of drying-bed biosolids would improve soil productivity and promote bermudagrass (Cynodon dactylon) and establishment on the Trinity clay soil. Anaerobically digested, air-dried biosolids were applied to Trinity clay (very-fine, montmorillonitic, thermic, typic, pelludert) at rates of 0, 112, 560, and 1120 Mg ha⁻¹. The biosolids were incorporated into the top 15 cm of the soil and bermudagrass sprigs were planted. Biosolids significantly reduced soil bulk density and soil resistance to penetration when measured during the second and third years after the application. Biosolids increased soil concentrations of organic carbon, nutrients (nitrogen, phosphorus, copper, zinc, iron) and heavy metals (cadmium, chromium, nickel, lead). Bermudagrass biomass production and nutrient uptake were increased due to biosolids, but heavy metals were not significantly transferred from soil to above-ground plant tissue.