@article{onwuka_scinto_price_melesse_2023, title={Dynamics of particles and phosphorus in canals of the Lower Everglades, Florida, USA}, url={http://dx.doi.org/10.1016/j.scitotenv.2023.166508}, DOI={10.1016/j.scitotenv.2023.166508}, abstractNote={Water flow (discharge) can affect water quality by influencing the concentration and transport of waterborne contaminants. The effects of discharge on phosphorus (P) and particle concentrations in managed canals, were described using concentration-discharge (C-Q) relationships, accumulation of suspended and settling particles, and the physicochemical characteristics of these particles and bed sediments. Piecewise regression analysis on C-Q relationships revealed slope inflections that denoted thresholds, where P-behavior changed from low to high discharge. The C-Q relationships generally showed higher concentrations at higher discharges. In three of the four Lower Everglades canals studied, long-term (1995-2019) lower temporal resolution data (daily to weekly) was adequate to describe the influence of discharge on P concentrations. However, in one site, the L-29 Canal, higher temporal resolution data (minutes to hours over weeks), derived from acoustic sensors, was necessary to produce C-Q relationships. In the L-29 Canal, discharge affected the transport, settling, and sediment accrual at distances from the S333 inflow structure. Sediment traps showed higher discharge led to a greater accumulation of suspended particles that were transported and settled farther downstream. Generally, downstream surface sediments in the L-29 Canal had greater organic matter, lower bulk density and higher TP than those of the upstream site, reflecting long-term effects of discharge. Understanding the effects of discharge on particles and associated nutrients, especially at discharge thresholds that lead to concentration increases, can inform the operation of managed canals to reduce contaminant loading to downstream sensitive ecosystems.}, journal={Science of The Total Environment}, author={Onwuka, Ikechukwu S. and Scinto, Leonard J. and Price, René M. and Melesse, Assefa M.}, year={2023}, month={Dec} }
 @article{onwuka_scinto_fugate_2023, title={High-Resolution Estimation of Suspended Solids and Particulate Phosphorus Using Acoustic Devices in a Hydrologically Managed Canal in South Florida, USA}, url={https://doi.org/10.3390/s23042281}, DOI={10.3390/s23042281}, abstractNote={Conventional methods of measuring total suspended sediments (TSS) and total particulate phosphorus (TPP) are typically low-resolution and miss critical processes that impact their exports in aquatic environments. To create high-resolution TSS and TPP estimates, echo intensity (EI), a biproduct of velocity measurements from acoustic devices, was utilized. An acoustic Doppler velocimeter (ADV) and an acoustic Doppler current profiler (ADCP) were deployed in three locations in the L-29 Canal in South Florida, USA, to obtain estimates near the canal bed and in the water column, respectively. Corrections for transmission losses from the ADCP proved unnecessary due to the low vertical variability in the measured EI. EI calibrations were performed using artificially created TSS obtained from bed sediments (ADV) and gravimetrically measured TSS from water samples that matched the depths and times of the ADCP deployments. The measured TSS values were then analyzed for total phosphorus and converted to TPP estimates. The results showed that high TSS and TPP were caused by the rapid discharge releases typical of managed canals. This work demonstrates that high-resolution estimates are imperative for assessing the effects of such swift hydrologic changes on the potential export of sediments and nutrients to delicate ecosystems downstream.}, journal={Sensors}, author={Onwuka, Ikechukwu S. and Scinto, Leonard J. and Fugate, David C.}, year={2023}, month={Feb} }
 @article{onwuka_scinto_mazdeh_2021, title={Comparative Use of Hydrologic Indicators to Determine the Effects of Flow Regimes on Water Quality in Three Channels across Southern Florida, USA}, url={https://doi.org/10.3390/w13162184}, DOI={10.3390/w13162184}, abstractNote={This study determines the relationships between water flow and water quality in three types of channels in southern Florida, USA: Shark River Slough, Peace River, and Hillsboro Canal. Peace River most resembles a natural channel with floodplain connectivity, sinuosity, and uninhibited flow. Shark River Slough has a natural, shallow channel with sheet flow, while the Hillsboro Canal is the most modified channel due to dredging, straightening, and regulated flow. Hydrologic indices for each channel were estimated to characterize flow regimes and flow variability, while concentration–discharge (C–Q) relationships were determined to quantify the impact of flow regime on water quality. The greatest variability in flow occurred at the Hillsboro Canal, followed by Peace River and Shark River Slough. Connectivity to floodplains and long durations of low and high flow pulses at Peace River and Shark River Slough contributed to the dilution of water quality constituent concentrations at higher flows. Conversely, the channelized characteristics of the Hillsboro Canal resulted in an enrichment of constituents, especially during high flows. This study suggests that C–Q relationships can be used in canal discharge management to prevent water quality degradation of sensitive downstream wetland and aquatic ecosystems.}, journal={Water}, author={Onwuka, Ikechukwu S. and Scinto, Leonard J. and Mazdeh, Ali Mahdavi}, year={2021}, month={Aug} }