Low Flow Periods Research Articles

Assessment of the water quality of the Niger River in Bamako, Mali, based on the Water Quality Index

Abstract The Niger River, threatened by human activities, is the main drinking water source for the population of Bamako city. This study assesses the trend of Niger River pollution in Bamako using the Water Quality Index (WQI). Fourteen parameters, namely Turbidity, Potential of Hydrogen (pH), Electrical Conductivity, Dissolved Oxygen, Total Dissolved Solids, Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), Nitrate, Nitrite, Ammonium, Phosphate, Sulphate, Chloride and Copper, were employed to characterise the Niger River water quality during the period from 2016 to 2020. Parameters were measured at 15 sampling locations. High values of Turbidity, pH and high concentrations of BOD5, COD, Nitrite, Ammonium and Phosphates were recorded. The results showed that the Niger River water quality was good for 4 months and poor for 5 months during the dry season in a low flow period. Moreover, the water quality was poor during the 3 months of the wet season in the high flow period. The calculated WQI average values ranged from 75 to 100, indicating very poor water quality from upstream to downstream of Bamako city. Therefore, the Niger River water is polluted and cannot be used for drinking or industrial uses without any treatment.

Hydrochemical Characteristics and Quality Assessment of Surface Water in Sidakan-Balakyan River, Kurdistan Region, NE, Iraq

The hydrochemical characteristics of surface water are studied to understand their source, type of water, and evolution. This study aims to determine the hydrochemical characteristics and controlling factors, by evaluating the water quality of the Sidakan-Balakyan River. The samples were collected along the Sidakan-Balakyan River to the junction point of the Sidakan-Rwanduz Rivers, for each sample, physical (pH, EC, Temperature, Turbidity, TDS and T.H) and chemical parameters (Mg2+, Ca2+, K+, Na+, HCO3-, Cl-, SO42- and NO3-) were analyzed. The results showed that all water samples were within the acceptable range. The results obtained from the Piper and Chadha diagram indicate that the studied water samples during High Flow Period is Mg- Bicarbonate type as well as Ca+2 and SO4-2, whereas during Low Flow Period in Sidakan river is Mg2+- Bicarbonate, But in Balakyan and Rwanduz rivers are Ca2+- Bicarbonate. Moreover, based on Gibbs Diagram, water samples were distributed in the rock weathering dominance section. Based on TDS and T.H of water samples were found to be moderately hard fresh water. Additionally, the river water can not be used for drinking directly. Most samples have a good to excellent water quality index except for some samples which are unsuitable during High Flow Period.

Assessment of the spatiotemporal water quality variations in the Middle Route of China's South-to-North Water Diversion Project by multivariate analysis.

As an important drinking water source for North China, the Middle Route of China's South-to-North Water Diversion Project (MRP) must provide high-quality water to maintain the health and safety of more than 60 million people. However, different water transfer operation modes may affect the water quality status, and the spatiotemporal characteristics of water quality in the MRP, with high water transfer volumes, remain poorly understood. In this study, the differences in water quality in the MRP between the initial stage (Nov. 2015 to Oct. 2017, low transfer volumes) and the current stage (Nov. 2017 to Oct. 2020, high transfer volumes) were compared, and the spatiotemporal water quality variations in the current stage were evaluated using multivariate statistical methods. For this purpose, approximately 12,528 observations, including the datasets of 12 water quality parameters collected from 29 monitoring sites, were used. The results showed that the water quality status improved significantly during the current stage. Based on principal component analysis (PCA), physical parameters (natural), nutrients, organic matter and microbes (anthropogenic), and heavy metals (natural and anthropogenic) were the key factors influencing water quality variations. Based on hierarchical cluster analysis, 12months were classified into two groups: the high-flow period (HFP, Jun.-Oct.) and the low-flow period (LFP, Nov.-May). Additionally, 29 sampling sites were grouped into three sections: the Henan section (HN; S1-S16), Hebei section (HB; S17-S24), and Tianjin-Beijing section (TB; S25-S29). From the perspective of water quality regulation, the total nitrogen concentration and permanganate index in the HB and TB sections of the MRP should be considered throughout the year, and the faecal coliform concentrations in these two sections should also be considered during the HFP. The results of this study could be helpful for local administrations to understand and control pollution and better protect the quality of water in the MRP.

Estimation of Lacustrine Groundwater Discharge (LGD) to an urban Himalayan lake using environmental tracers (222Rn, δ18O, EC)

Lacustrine Groundwater Discharge (LGD) is a complex process that controls lake characteristics and plays a dominant role in modifying the hydrological and chemical budget of a lake. The current study was carried out with the aim to assess the groundwater discharge component of the hydrological budget of an urban Himalayan lake. We used natural tracers including radioisotope of radon (222Rn), stable water isotopes (δ2H and δ18O), electrical conductivity and water temperature to identify the potential groundwater discharge zones in a lake. The obtained LGD results, based on radon mass balance model (RMB) and end member mixing analysis (EMMA) of stable water isotopes in combination with physical parameters, show temporal as well as spatial variation. The total LGD to the Dal Lake, estimated from RMB, was 62.25 ± 9 × 104 m3/d (24 ± 3 %) and 33 ± 6 × 104 m3/d (36 ± 4 %) during high and low flow periods, respectively. The results suggested that the stream water is the dominant contributor accounting for 75 % (±7) and 55 % (±8), followed by groundwater as 22 % (±5) and 40 % (±4), during high and low flow periods, respectively. However, the contribution from direct precipitation is very little (3–4 %). High groundwater flux towards northeastern side of the lake is substantiated by more aquifer thickness and high hydraulic gradient. The current study offers first in-depth understanding about LGD of an urban Himalayan lake and could be applicable for lake ecosystem protection policies and water resource management plans in the region and elsewhere.

Mercury migration to surface water from remediated mine waste and impacts of rainfall in a karst area – Evidence from Hg isotopes

Mine waste (MW) in historical mercury (Hg) mining areas continuously emits Hg into local environment, including aquatic ecosystems. Tracing Hg migration process from MW and determining its relative contribution to Hg pollution is critical for understanding the environmental impact of MW remediation. In this study, we combined data of Hg concentration, speciation, and isotope to address this issue in the Wanshan Hg mining area in southwest China. We found that rainfall can elevate Hg concentrations in river water and control the partitioning and transport of Hg in karst fissure zones through changing the hydrological conditions. A consistently large offset of δ202Hg (1.24‰) was observed between dissolved Hg (DHg) and particulate Hg (PHg) in surface water during the low-flow period (LFP), which may have been related to the relatively stable hydrologic conditions and unique geological background (karst fissure zones) of the karst region (KR). Results from the ternary Hg isotopic mixing model showed that, despite an order of magnitude reduction in Hg concentration and flux in river water after remediation, the remediated MW is still a significant source of Hg pollution to local aquatic ecosystems, accounting for 49.3 ± 11.9% and 37.8 ± 11.8% of river DHg in high flow period (HFP) and LFP, respectively. This study provides new insights into Hg migration and transportation in aquatic ecosystem and pollution source apportionment in Hg polluted area, which can be used for making polices for future remediation actions.

A conditional copula model to identify the response of runoff probability to climatic factors

Understanding the response of runoff to climate drivers is important to ensure rational water allocation and address the risk of drought. Many models that assess the effect of climate factors on the response of runoff volume have been developed and widely used. However, models that assess the response of the probability of runoff occurrence (runoff probability) are lacking. In this study, we developed a model by integrating a conditional probability distribution (CPD) and a copula function model to assess the effect of climate conditions on variation of the probability of runoff occurrence. The developed model was applied to the basin of Poyang Lake, the largest freshwater lake in China. The study showed that Frank copula was the copula that had the best-fitted effect to identify the impact of climate factors (except for precipitation and air temperature [AT] in low flow period [LFP]) on the probability of runoff occurrence. The copulas with the best-fitted effect of precipitation and AT is the Gumbel copula and Clayton copula during LFP, respectively. Precipitation, relative humidity (RH), and water vapor pressure (WP) were positive with streamflow variation, while wind speed (WS), potential evapotranspiration (ET0), and sunshine duration (SD) were negative with runoff, but AT had an inverse relation with the streamflow during high flow period (HFP) and LFP. Sensitivity analysis indicated that precipitation has a weaker effect on the likelihood of extreme hydrological events than many other climate factors (such as RH and SD). Moreover, the sensitivity of runoff probability to climatic factors tended to be relatively stable during HFP, which was in contrast to that during LFP. This research highlights the significance of considering change conditions when evaluating runoff response to climate drivers, which is consistent with the objective of achieving more accurate runoff predictions to combat climate change and extreme weather conditions.

Addressing inadequate blood flow during normothermic regional perfusion for in-situ donation after circulatory death grafts preservation.

Donation after circulatory death (DCD) has emerged as attainable strategy to tackle the issue of organ shortage, expanding the donor pool. The DCD concept has been applied to the multiple declinations of circulatory arrest, as per the Modified Maastricht Classification. Notwithstanding, whichever the scenario, DCD donors experience a variable warm ischemia time whose correlation with graft dysfunction is ascertained. This applies to both "controlled" (cDCD) donors (i.e., the timespan from the withdrawal of life-sustaining therapies to the onset of in-situ perfusion), and "uncontrolled" DCD (uDCD) (i.e., the low-flow period during cardiopulmonary resuscitation - CPR). This sums up to the no-flow time from cardiac arrest to the start of CPR for uDCD donors, and to the no-touch period for both uDCDs and cDCDs. Static and hypothermic storage may not be appropriate for DCD grafts. In order to overcome this ischemic insult, extracorporeal membrane oxygenation devices are adopted to guarantee the in-situ grafts preservation by means of techniques such as the normothermic regional perfusion (NRP) which consists in a selective abdominal perfusion obtained via the endovascular or surgical occlusion of the thoracic aorta. The maintenance of an adequate pump flood throughout NRP is therefore a sine qua non to accomplish the DCD donation. The issue of insufficient pump flow during NRP is prevalent and clinically significant but its management remains technically challenging and not standardized. Hereby we propose a systematic algorithmic approach to address this relevant occurrence.

Algal recolonization following an extraordinary drought in permanent lowland streams

Droughts reduce habitat and fragment the continuity of running water systems producing lasting effects on sediment biota and affecting density and biomass of algae. When droughts occur, the survival of algae and cyanobacteria of the biofilm depends on different alternatives to overcome the stress. In Pampean streams, periods of low flow causing desiccation stress in the biofilm may be linked to El Niño/Southern Oscillation phenomenon, and to water management practices (irrigation and extraction), that can reduce stream base flows for prolonged periods, reducing wetted area and dewatering the stream bed. The aim of this study was to determine the response of epipelic algae (analyzed by greater algal groups Cyanobacteria, Euglenophyta, Dinoflagellates, Green Algae, Diatoms) to desiccation as a disturbance, in streams without frequent periods of drought. First, we studied the in situ vertical distribution of epipelic algae in stream sediment during the drought period as a refuge strategy, along with the vertical distribution of sediment humidity in 10 cm sediment corers divided in 6 segments at depths 0-1 cm (uppermost layer), 1-2 cm, 2-3 cm, 3-4 cm, 4-5 cm and 5-10 cm. Secondly, we analyzed the recolonization patterns of the epipelic algal assemblage after the drought by studying the succession of autotrophic organisms, in order to better understand the role of sediments as a source of algae populations. For this, 2 cm deep corers were placed with water in microcosms and monitored during 2 weeks. Our results indicate that when the streams are affected by a severe drought, algae and cyanobacteria survive; this could be related with the moisture content of the sediment. Besides, after hydratation of the sediment, the community rapidly increased its density. Cyanobacteria were the most resistant group to desiccation and the one who had the faster reaction to hydratation.

Body size dictates physiological and behavioural responses to hypoxia and elevated water temperatures in Murray cod (Maccullochella peelii).

Increasing drought frequency and duration pose a significant threat to fish species in dryland river systems. As ectotherms, fish thermal and hypoxia tolerances directly determine the capacity of species to persist in these environments during low flow periods when water temperatures are high and waterbodies become highly stratified. Chronic thermal stress can compound the impacts of acute hypoxic events on fish resulting in significant fish mortality; however, it is not known if all size classes are equally susceptible, or if the allometric scaling of physiological processes means some size classes are disproportionately affected. We investigated the physiological responses of Murray cod (Maccullochella peelii) over a four-fold body size range (0.2-3000g) to acute changes in water temperature and oxygen concentration following 4 weeks of acclimation to representative spring (20°C) and summer (28°C) water temperatures. We recorded maximum thermal tolerance (CT max), oxygen limited thermal tolerance (PCTmax ), lowest tolerable oxygen level (as the oxygen level at which lose equilibrium; O2,LOE), gill ventilation rates and aerial surface respiration threshold, blood oxygen transport capacity and lactate accumulation. Acclimation to elevated water temperatures improved thermal and hypoxia tolerance metrics across all size classes. However, body size significantly affected thermal and hypoxia responses. Small M. peelii were significantly less hypoxia tolerant than larger individuals, while larger fish were significantly less thermal tolerant than smaller fish. Hypoxia constrained thermal tolerance in M. peelii, with both small and large fish disproportionally compromised relative to mid-sized fish. Our findings indicate that both very small/young (larvae, fry, fingerlings) and very large/older M. peelii in dryland rivers are at significant risk from the combined impacts of a warming and drying climate and water extraction. These data will inform policy decisions that serve to balance competing demands on precious freshwater resources.

An alarming picture of larval fish assemblages entrained into the cooling system of the Kozienice Power Plant (Poland) revealed by DNA metabarcoding

The annual entrainment of early life history stages of fishes (ELH) into the cooling system of the largest power plant in the Vistula River basin was assessed using passive capture techniques and DNA metabarcoding. Hydrological and thermal conditions during the 2022 breeding season were also analyzed. A total of 5,011 ELH individuals identified to four families and 23 species were recorded. ELH densities upstream of the power plant were an order of magnitude higher than they were downstream. Along with the phenology of occurrence and species composition of drift, this indicated very high (probably close to 100%) ELH mortality during passage through the cooling system. Taking into account low water discharge at constantly high water intake during the season, the absolute estimate of ELH individuals entrained into the cooling system was > 103 × 106. The power plant entrains a notable proportion of one-quarter to one-half of the total ELH drifting by, especially during low-flow periods. Together with the very high abundance of two invasive Ponto-Caspian gobies, the magnitude of the entrainment of ELH into the Kozienice Power Plant presents a truly alarming picture.

Water Balance Uncertainty of a Hydrologic Model to Lengthy Drought and Storm Events in Managed Forest Catchments, Eastern Australia

Interest has grown in applying hydrologic models in managed catchments despite uncertainties around model inputs and empirical relationships to simulate complex geo-hydrological processes of streamflow and sediment variations. Unquantified interactions between geophysical, climate and management indices can also increase simulation uncertainties. Calibration of model outputs against observed values allows identification of the most influential variables and their optimised ranges by which model performance can be enhanced. A rainfall-runoff Soil and Water Assessment Tool (SWAT) model was utilised for four catchments in northern New South Wales, Australia to simulate time series of streamflow across varying rainfall regimes, from dry seasons from 2002 towards rainy 2009. Parameters causing a substantial change on model streamflow outputs were first identified using a sensitivity analysis which indicated that hydrologic factors governing the sources of water supply were critical parameters. These sensitive variables were substantially derived from groundwater modules, basic flow in the main channel, and management practices. Statistical tests of between-catchment differences showed that model simulations performed better in a catchment where the sole rain gauge was installed, while also having the narrowest variations in simulated values (r-index = 0.02). In contrast, the highest uncertainty of model simulations was found in the furthest catchment from the rain gauge where there was not a satisfactory agreement with observed data. Yearly differences between 2002 and 2009 indicated an overestimation of streamflow during low flow periods. However, the calibration process performed well in most peak flows where estimations followed the respective observed values. Long-term dry periods between 2002 and 2007 resulted in an overestimated baseflow by predicting an unrealistic recharge infiltrating aquifers.

Augmenting environmental flow information with water temperature: case study in Eastern Canada

The increasing global water demand and climate change put freshwater resources and riverine ecosystems at risk of increasing scarcity and conflict in water usage. Stream biota may be confronted with increasing stressful aquatic habitat conditions due in part to increasing water temperatures. In response to these issues, environmental flows play a crucial role in flow assessment, water resource management and the protection of aquatic biota. Environmental flows (eflows), also known as instream flow requirements, refer to the amount of water needed in rivers to maintain a balanced aquatic ecosystem. Recently, the inclusion of river temperature in the assessment of eflows has raised interest, especially in the context of climate change and dam operations, which are altering the river thermal regimes and affecting aquatic habitat. This study focuses on hydrological metrics that can be used to prescribe eflows in Atlantic Canada and Quebec (Eastern Canada). Eflow analyses were conducted jointly with the analyses of river temperatures at 61 sites. The results show that summer environmental flow metrics can be associated with relatively high water temperatures during a period when water withdrawals may be important. Classifying rivers according to their thermal regime during summer low flow periods prior to prescribing an eflow target is therefore recommended.

Nitrogen and phosphorus spatio-temporal distribution and fluxes intensifying eutrophication in three tropical rivers of Côte d'Ivoire (West Africa)

Nutrient contamination assessments in the three West African tropical Comoé, Bandama, and Bia Rivers (Côte d'Ivoire) were performed from March 2016 to March 2018. Five stations per river were sampled. Nutrients spatio-temporal distributions were mapped and showed nitrogen concentrations (nitrite 0.001 to 0.025 mg/L NO2−-N, and nitrate 0.26 to 3.60 mg/L NO3−-N) increased significantly with rainfall contrary to phosphorus (0.01 to 0.12 mg/L P). The Chl-a and TSItsr data revealed the hypereutrophic status of rivers. Moreover, N:P mass ratio suggests nitrogen as the main limiting factor of primary production during the low (March) and high flow periods (October–November), while phosphorus is the limiting factor in June, at the high flow beginning. The land uses around watersheds were the main sources of phosphorus and nitrogen enhancing the rivers' eutrophication. Phosphorus and nitrogen fluxes were related to leaching river catchments and were significant sources of nutrients to the Atlantic Ocean.

Comparing paleo reconstructions of warm and cool season streamflow (1400–2018) for the North and South Saskatchewan River sub-basins, Western Canada

The North and South Saskatchewan River sub-basins comprise the Saskatchewan River Basin (SRB), which originates in the eastern slopes of the Rocky Mountains of Alberta (Canada) and Montana (USA), extending across the vast landscape of three Canadian Provinces. The SRB is the most populated region of the Northern Great Plains, where water demands from agriculture, industry, and municipalities can be a substantial proportion of supply during periods of low flow and hydrological drought. Changing climatic conditions and shifts between periods of extreme wet and dry weather emphasize the need for a better understanding of past and future seasonal variability of the surface water balance within and between the sub-basins. Climate extremes, such as hydrological drought and excessive moisture conditions occurring simultaneously can create detrimental effects. Using a multi-species network of over 80 tree-ring chronologies, warm (May through August) and cool (December through April) season streamflow (1400–2018) were independently reconstructed for the North and South Saskatchewan River sub-basins. Departures from seasonal flow and spectral and wavelet analyses of the reconstructions indicate significant variability at inter-annual and multi-decadal scales.

Seasonal Variation in the Water Quality and Eutrophication of Lake Xingyun in Southwestern China

It is crucial to understand the spatial-temporal variation of water quality for the water safety and eutrophication migration in plateau lakes. To identify the variation property and the main causes of eutrophication and continuous water quality deterioration, the water quality, including the water temperature (WT), dissolved oxygen (DO), pH, Chl-a, turbidity, total nitrogen (TN) and total phosphorus (TP), of Lake Xingyun was monitored from 2016 to 2021, and their spatial and temporal distribution characteristics were analyzed. The results show that there is no obvious thermal stratification in the vertical direction; pH and DO decrease with depth, which is caused by both physical and biochemical processes, especially at the bottom of Lake Xingyun, which has an anaerobic environment. The chlorophyll content was higher during the high-flow periods and varied significantly in the vertical direction; the spatial variation of water quality in Lake Xingyun was more obvious in the low-flow period and alkaline throughout the year. The average content of total phosphorus (TP) ranged between 0.33 and 0.53 mg/L during the high-flow periods and between 0.22 and 0.51 mg/L during the low-flow periods, while the average content of total nitrogen (TN) ranged between 1.92 and 2.62 mg/L and 1.36 and 2.53 mg/L during the high- and low-flow periods, respectively. The analysis of the inflow samples shows that exogenous nitrogen and phosphorus is the main pollution source affecting the nitrogen and phosphorus content of Lake Xingyun. The trophic level index (TLI) shows that Lake Xingyun is in eutrophication all year round, and even in areas less affected by the exogenous nutrient, there are still conditions for cyanobacterial blooms. This study shed new light on the water quality, eutrophication status and changes in Lake Xingyun, providing suggestions for controlling lake pollution and eutrophication mitigation.

Zooplankton distribution and community structure as a function of environmental variables in the Niger River and its tributaries in Niger

The Niger River and its main tributaries (Sirba, Tapoa and Mékrou) in Niger were sampled during high and low water flow with the objectives of (1) comparing the taxonomic structure, diversity and abundance of the zooplankton community (rotifers, copepods, crustaceans) along the river and (2) determining which environmental or biological factors influence the distribution of the zooplankton communities most strongly. The impact of the tributaries at high-flow was also evaluated. Rotifers (32 taxa) were the most abundant and diverse followed by Cladocerans (13 taxa) and Copepods (three taxa). The mean number of taxa (16.5 and 17.6, respectively), the Shannon-Weaver diversity index (2.7 and 2.8, respectively) and the evenness (0.7 and 0.7, respectively) did not vary significantly between the high- or low-flow periods, or along the length of the Niger River and its tributaries. The mean zooplankton abundance was highest during low-flow periods (40 × 103 ± 45 × 103 ind. m−3) but showed no specific spatial pattern. During high-flow sampling, the mean zooplankton abundance (3 × 103 ± 2 × 103 ind. m–3) increased progressively downstream. RDA analysis showed that rotifers are associated with high conductivity and NO2 − concentrations, copepods with chlorophyll a, while cladocerans were abundant when conductivity, chlorophyll a and NO2 − concentrations were low.

Abstract 154: Limitation of Troponin T In Identifying the Cause of Out-of-hospital Cardiac Arrest

Introduction: High Sense-Troponin T (HS-TnT) is a key determinant for presence or absence of acute MI in chest pain patients (pts). Its value for acute MI diagnosis in pts with out-of-hospital cardiac arrest (OHCA) needs assessment because myocardial ischemia may be the cause but also a consequence of cardiac arrest causing global ischemia during no and low flow periods. Methods: Data were prospectively collected. From pts included in the ARREST registry who survived OHCA to discharge with VF as initial rhythm, the cause of OHCA and peak HS-TnT were analyzed. Cause of OHCA was determined independently by researchers, from history, admission and serial ECG, coronary angiography (CAG), cardiac imaging and genetics as available and indicated, without using HS-TnT information. MI diagnosis was made according to the 4 th universal definition of MI: type 1 MI (thrombotic STEMI/NSTEMI), type 2 MI (supply/demand imbalance) and no MI (short transient ECG changes and all non-ischemic causes). Results: From 2012 till 2018 in the study region 373 OHCA pts met the inclusion criteria and had a known peak HS-TnT. Of these, Type 1 MI was present in 109 STEMI and 39 NSTEMI pts, type 2 MI in 116 pts and no MI in 109 pts. No significant coronary stenosis or normal CAG was present in 81 pts: 11/106 (10%) with type 2 MI and 70/109 (64%) without MI. HS-TnT exceeded the conventional diagnostic threshold of 4 times upper limit of normal (4x14ng/L = 56 ng/L) in 99%, 95%, 95% and 89% of pts, respectively. Median peak HS-TnT levels in STEMI, NSTEMI, Type 2 and no AMI pts was 1890 ng/L, 480 ng/L, 300 ng/L and 261 ng/L, respectively. (Figure) Area Under the ROC-Curve of HS-TnT values to differentiate between type 1 NSTEMI and type 2 AMI was 0.649, between type 1 NSTEMI and no MI 0.684 and between type 2 MI and no AMI 0.555. Conclusion: Exclusion of diagnosis of MI in OHCA pts cannot be made with HS-TnT, nor a distinction between NSTEMI, type 2 MI and no AMI. Based on HS-TnT many OHCA pts without ischemic cause would classify as NSTEMI.

Noninvasive and Invasive Renal Hypoxia Monitoring in a Porcine Model of Hemorrhagic Shock.

Up to 50% of patients with trauma develop acute kidney injury (AKI), in part due to poor renal perfusion after severe blood loss. AKI is currently diagnosed based on a change in serum creatinine concentration from baseline or prolonged periods of decreased urine output. Unfortunately, baseline serum creatinine concentration data is unavailable in most patients with trauma, and current estimation methods are inaccurate. In addition, serum creatinine concentration may not change until 24-48 h after the injury. Lastly, oliguria must persist for a minimum of 6 h to diagnose AKI, making it impractical for early diagnosis. AKI diagnostic approaches available today are not useful for predicting risk during the resuscitation of patients with trauma. Studies suggest that urinary partial pressure of oxygen (PuO2) may be useful for assessing renal hypoxia. A monitor that connects the urinary catheter and the urine collection bag was developed to measure PuO2 noninvasively. The device incorporates an optical oxygen sensor that estimates PuO2 based on luminescence quenching principles. In addition, the device measures urinary flow and temperature, the latter to adjust for confounding effects of temperature changes. Urinary flow is measured to compensate for the effects of oxygen ingress during periods of low urine flow. This article describes a porcine model of hemorrhagic shock to study the relationship between noninvasive PuO2, renal hypoxia, and AKI development. A key element of the model is the ultrasound-guided surgical placement in the renal medulla of an oxygen probe, which is based on an unsheathed optical microfiber. PuO2 will also be measured in the bladder and compared to the kidney and noninvasive PuO2 measurements. This model can be used to test PuO2 as an early marker of AKI and assess PuO2 as a resuscitative endpoint after hemorrhage that is indicative of end-organ rather than systemic oxygenation.

Spatiotemporal characteristics of microplastics in a university wastewater treatment plant: Influence of sudden on-campus population swings

We studied the occurrence and characteristics (sizes, shapes, and polymer compositions) of microplastics (MPs) in a secondary wastewater treatment plant (WWTP) at the University of Mississippi both spatially and temporally. Putative MPs were isolated by sieving, matrix digestion, and density separation, and quantified using stereomicroscopy, with a subset of samples analyzed by Focal Plane Array (FPA) µ-FTIR imaging. In the influent, the highest MP concentration (particles/L ± 1 SD, n = 3) occurred after a football game on campus (62.3 ± 7.6) and the lowest (19.7 ± 2.1) during the summer with little activity on campus. Over 90% of the MPs were removed in the primary treatment. Downstream, MPs were most abundant in the closed loop reactor with concentrations as high as 1962 particles/L. Concentrations in secondary clarifier and final treated effluent were both < 4 particles/L during both normal flow (∼2000 m3/d) and high-flow (>2500 m3/d) periods, and between 16 and 39 particles/L during a low-flow (<1500 m3/d) period. This difference likely stems from changes in plant operations during the low-flow period to support the activated sludge, including longer process times. MPs were mainly composed of polyester, polyethylene, acrylates, polypropylene, polyurethane, polyvinyl chloride, and polystyrene. Fibers were most abundant throughout the system, averaging 61%, followed by fragments (21%), films (13%), and beads and foams (∼5%). Overall, we show that flow rates and treatment times can profoundly influence MPs concentrations in the treated effluent, and that the optimal wastewater treatment conditions also yield the best MP removal efficiency.

A structured framework to interpret hydro-climatic and water quality trends in Mediterranean climate zones

Many regions of the world have experienced rapid hydro-climatic changes in recent decades. Mediterranean areas have especially experienced prolonged droughts, changes to runoff, and low-flow periods. Many methods and assumptions for assessing trends in rainfall and runoff are available, however, a comprehensive framework is required that can consider variations at large temporal and spatial scales, long-term persistence (LTP), seasonal patterns, and multiple change points. An analysis framework has been developed in R and applied to a network of 107 rainfall gauges (with about 100 yrs data) and 90 streamflow-water quality gauges (30 – 50 yrs data) across South-west Western Australia, a region with a typical Mediterranean climate. Trends were estimated using the Original Mann–Kendall (OMK) family of tests including using the Mann-Kendall Test under the Scaling Hypothesis (MKLTP) and Seasonal Mann–Kendall (SMK). Single and multiple change points were calculated by the non-parametric Lanzante’s test (LAT), E-Agglomerative algorithm (ECP), and Energy Divisive (EDP). Trend tests show annual rainfall has decreased by 2.6 mm/yr in the Western areas and increased by 0.9 mm/yr in the Eastern areas with corresponding change points in the 1940 s-1960 s and from 1995 to 2000 although 30 % of the annual rainfall and 100 % of the standardized precipitation index (SPI) time series were found to be under LTP. A regional flow trend analysis shows catchments are yielding much less runoff in more than 90 % of gauged stations. The runoff in perennial and ephemeral streams has shown a decline with the rate of 6 (54 %) and 2 (50 %) mm/yr, respectively. Runoff and baseflow decline occurred as step changes lagged after rainfall, and the rate of decline in baseflow was more than for runoff, suggesting that groundwater connectivity with stream inverts has fallen substantially. Stream salinities increased by 64 mg/L/yr (or 15 %) overall which was highly significant. The framework provides a structured approach to analyse changes in rainfall, runoff and stream salinity for a Mediterranean climate that is projected to become even warmer and drier.