Assessment Of Temporal Variability Research Articles

Activity Budget and Sociality of the Northern Lesser Galago, Galago senegalensis

AbstractComplex sociality in primates often is argued to have evolved after the appearance of diurnal activity. Studying the behaviour of nocturnal primates is fundamental to understanding the evolutionary origins of primate behaviour and ecology, yet much less is known about the nature of sociality in nocturnal primate species than their diurnal counterparts. We investigated group size, communication, and social interactions in free-ranging, Northern lesser galagos (Galago senegalensis) and present an activity budget and assessment of temporal variation in their behaviour. We collected continuous behavioural data using focal follows at three different stages of the night from individuals at Kwakuchinja, Northern Tanzania. We also collected group size data from Northern lesser galagos at Fongoli, Southeastern Senegal, and Lolldaiga Hills Ranch, Central Kenya. We categorised behaviours and, where sample sizes permitted, used Kruskal–Wallis tests to compare the durations of observed behaviours between the morning (pre-dawn), evening (from dusk), and later in the night. We analysed 140 focal follows (31.4 h of continuous behavioural data) and found that the proportion of time spent foraging, inactive, in locomotion, in self-maintenance, and vigilant, varied across the three stages of the night; galagos spent a great deal of their time inactive in the morning and foraging was more prevalent in the evening. Group size at Kwakuchinja was significantly larger than at Fongoli or LHR. Galagos were in groups of two or more in the majority of encounters at Kwakuchinja (55%; N = 76), rather than alone, but spent most of their nighttime activity alone at Fongoli (79%; N = 185) and LHR (80%; N = 142). Overall vocalisation rates were higher in the morning than other times throughout the night, although contact calls were relatively more frequent in the evening than other times. We recorded both affiliative and agonistic social interactions, but these contributed almost nothing to the overall activity budget. Our preliminary investigation into the social structure of Northern lesser galagos suggests that there are population differences in sociality and that overall, they connect more through vocalisations than through direct social interactions, thereby avoiding some of the potential costs associated with group-living. This variation in social organization suggests that we have more to learn about the drivers of sociality in nocturnal primates and the nature of their social structure.

Diversity and Quantitative Detection of Clade I Type nosZ Denitrifiers in the Arabian Sea Oxygen Minimum Zone.

A significant amount of nitrous oxide (N2O) is effluxed into the atmosphere as a result of marine denitrification in the Arabian Sea (AS) oxygen minimum zone (OMZ). An assessment of temporal variations in the diversity and abundance of nosZ denitrifiers was performed to establish the relative importance of these bacteria in denitrification. Sampling was conducted at the Arabian Sea Time Series (ASTS) location and a quantitative PCR (qPCR) ana-lysis was performed. We detected a high abundance of the nosZ gene at core OMZ depths (250‍ ‍m and 500 m), indicating the occurrence of denitrification in the AS-OMZ. The maximum abundance of the nosZ gene was observed during the Spring Intermonsoon (SIM) at 250‍ ‍m (1.32×106 copies L-1) and 500‍ ‍m (1.50×106 copies L-1). Sequencing ana-lysis showed that nosZ denitrifiers belonged to the classes Alpha-, Beta-, and Gammaproteobacteria. Taxonomic ana-lysis revealed that most OTUs were affiliated with Pseudomonas, Rhodopseudomonas, and Bradyrhizobium. Diversity indices and richness estimators confirmed a higher diversity of nosZ denitrifiers at 250‍ ‍m than at 500‍ ‍m during all three seasons. The present results also indicated that dissolved oxygen (DO) and total organic carbon (TOC) are critical factors influencing the diversity and abundance of the nosZ-denitrifying bacterial community.

Assessment of Temporal Variation in Hydrogeochemical Facies of River Water in the Central Himalayan Region

The water quality of a region is greatly influenced by the environment and its quality is a function of rock-water interaction and anthropogenic processes. 90% of the rural population of Uttarakhand depends on rivers and springs sources for their daily uses. Therefore, water characterisation and monitoring over time is important for human health and aquatic life. The basic understanding of hydrochemistry can be extracted by a trilinear piper diagram. The study also intends to develop hydro-chemical analysis for water quality at various locations in Uttarakhand to represent four major river catchments. The study attempted over 50 locations from 2010 to 2019 during pre and post-monsoon seasons. Four anions and four cations were used to understand hydrogeochemical facies. Result reveals that the most dominant hydrogeochemical facies were Ca-Mg-HCO3 in the entire region followed by Ca-Mg-Cl or Ca-Mg-SO4 facies due to limestone-dominant geology. Na-Cl or Na-SO4 facies enhanced due to agriculture activities while NaHCO3 facies due to the rapid weathering processes along the river course over the period. The study recommended for the area where the water type is either Na-Cl or Na-SO4 or Na-HCO3, intensive water resource planning should be implemented. These areas are highly vulnerable to human health costs.

Black carbon and particulate matter mass concentrations in the Metropolitan District of Caracas, Venezuela: An assessment of temporal variation and contributing sources

Atmospheric aerosols play an important role in atmospheric processes and human health. Characterizing atmospheric aerosols and identifying their sources in large cities is relevant to propose site-specific air pollution mitigation strategies. In this study, we measured the mass concentration of atmospheric aerosols with an aerodynamic diameter smaller than 2.5 µm (PM2.5) in the city of Caracas (urban) and in a tropical montane cloud forest (suburban site, located in a mountainous area 11 km far from Caracas) between June 2018 and October 2019. We also measured equivalent black carbon (eBC) mass concentration in PM2.5 in Caracas during the same period. Our goal is to assess PM2.5 and eBC temporal variation and identify their major sources in the area. eBC showed a pronounced diurnal cycle in the urban site, mainly modulated by traffic circulation and the diurnal changes of the mixing layer height. In contrast, PM2.5 showed stable median values during the day with slight variations like that of eBC. In the forest site, PM2.5 values were higher in the afternoons due to the convective transport of aerosols from Caracas and other surrounding urban areas located in adjacent valleys. The annual median for eBC and PM2.5 was 1.6 and 9.2 µg m–3, respectively, in the urban site, while PM2.5 in the forest site was 6.6 µg m–3. To our knowledge, these are the first measurements of this type in the northernmost area of South America. eBC and PM2.5 sources identification during wet and dry seasons was obtained by percentiles of the conditional bivariate probability function (CBPF). CBPF showed seasonal variations of eBC and PM2.5 sources and that their contributions are higher during the dry season. Biomass burning events are a relevant contributing source of aerosols for both sites of measurements inferred by fire pixels from satellite data, the national fire department’s statistics data, and backward trajectories. Our results indicate that biomass burning might affect the atmosphere on a regional scale, contribute to regional warming, and have implications for local and regional air quality and, therefore, human health.

An assessment of temporal variability in mast seeding of North American Pinaceae.

Our overall objective is to synthesize mast-seeding data on North American Pinaceae to detect characteristic features of reproduction (i.e. development cycle length, serotiny, dispersal agents), and test for patterns in temporal variation based on weather variables. We use a large dataset (n = 286 time series; mean length = 18.9 years) on crop sizes in four conifer genera (Abies, Picea, Pinus, Tsuga) collected between 1960 and 2014. Temporal variability in mast seeding (CVp) for 2 year genera (Abies, Picea, Tsuga) was higher than for Pinus (3 year), and serotinous species had lower CVp than non-serotinous species; there were no relationships of CVp with elevation or latitude. There was no difference in family-wide CVp across four tree regions of North America. Across all genera, July temperature differences between bud initiation and the prior year (ΔT) was more strongly associated with reproduction than absolute temperature. Both CVp and ΔT remained steady over time, while absolute temperature increased by 0.09°C per decade. Our use of the ΔT model included a modification for Pinus, which initiates cone primordia 2 years before seedfall, as opposed to 1 year. These findings have implications for how mast-seeding patterns may change with future increases in temperature, and the adaptive benefits of mast seeding. This article is part of the theme issue 'The ecology and evolution of synchronized seed production in plants'.

Assessment of Temporal Variation of Water Quality Parameters and the Trophic State Index in a Subtropical Water Reservoir of Bangladesh

This study was conducted to determine the suitability of water quality for fisheries management in Kaptai Lake from February 2019 to January 2020. Results showed that the temperature, transparency, TDS, pH, DO, EC, alkalinity and hardness were 20.9 to 31.8°C, 17 to 303 cm, 40 to 105 mg/L, 6.82 to 7.96, 6.1 to 7.65 mg/L, 75.33 to 172.33 µS/cm, 37 to 83 mg/L and 35 to 190 mg/L, respectively. However, nutrients as NH3, NO3-, NO2-, PO43- and SO42- were 0.01 to 0.05, 0.03 to 2.21, 36 to 96, 0.01 to 0.04 and 0.3 to 1.9 mg/L, respectively. Chlorophyll a and trophic state index (TSI) were 0.70 to 2.12 µg/L and 27.43 to 37.79, respectively. Study revealed that SO42-, DO and TDS were higher than the standard of ECR. On the other hand, NH3, NO3-, NO2-, PO43-, temperature, transparency, pH, EC, total hardness, total alkalinity, Chlorophyll a and TSI were within the standard levels. Concentrations of NO3-, NO2-, PO43-, Chlorophyll a and TSI (CHL) showed no significant variation with seasons. Conversely, TDS, transparency, EC, alkalinity, hardness, and SO42- were lower in monsoon compared to pre-monsoon and post-monsoon seasons. Besides, temperature, NH3, DO and TSI (SD) were higher in monsoon season. Results concluded that the Kaptai Lake is in mesotrophic condition with TSI (CHL) less than 40, and prominently there was a positive relationship between Chlorophyll a and Trophic State Index (TSI). In this regard, major nutrients and Chlorophyll a concentration in the Kaptai Lake may have an impact on the aquatic environment.

Assessment of temporal variations in adherence to NRP using video recording in the delivery room

IntroductionVideo recording and video evaluation tools have been successfully used to evaluate neonatal resuscitation performance. The objective of our study was to evaluate differences in Neonatal Resuscitation Program (NRP) adherence at time of birth between three temporal resuscitative periods using scored video recordings. MethodsThis is a retrospective review of in-situ resuscitation video recordings from a level 3 perinatal center between 2017 and 2018. The modified Neonatal Resuscitation Assessment (mNRA) scoring tool was used as a surrogate marker to assess NRP adherence during daytime, evening, and nighttime hours. ResultsA total of 260 resuscitations, of which 258 were births via Cesarean section, were assessed. mNRA composite scores were 86.2% during daytime hours, 87% during evening hours, and 86.6% during nighttime hours. There were no significant differences in mNRA composite scores between any of the three time periods. Differences remained statistically similar after controlling for complexity of resuscitations with administration of positive pressure ventilation (PPV), intubation, or chest compressions. ConclusionOverall adherence to NRP, as measured by composite mNRA scores as a surrogate marker, was high across all three daily resuscitative periods without significant differences between daytime, evening, and nighttime hours.

Genetic signatures of population bottlenecks, relatedness, and inbreeding highlight recent and novel conservation concerns in the Egyptian vulture.

The assessment of temporal variation in genetic features can be particularly informative on the factors behind demography and viability of wildlife populations and species. We used molecular methods to evaluate neutral genetic variation, relatedness, bottlenecks, and inbreeding in a declining population of Egyptian vulture (Neophron percnopterus) in central Spain. The results show that the genetic diversity remained relatively stable over a period of twelve years despite the decline in census and effective population sizes in the last decades. A relatively high proportion of nestlings from different and distant territories showed high relatedness in each study year. We also found support for an increasing impact of severe recent (contemporary) rather than distant (historical) past demographic bottlenecks, and the first evidence of inbred mating between full siblings coinciding with lethal malformations in offspring. The inbred nestling with feather malformations was positive to beak and feather disease virus recorded for the first time in this species. These results alert on recent and novel threats potentially affecting health and reducing the adaptive potential of individuals in this threatened species.

A Simple Time-Varying Sensitivity Analysis (TVSA) for Assessment of Temporal Variability of Hydrological Processes

Time-varying sensitivity analysis (TVSA) allows sensitivity in a moving window to be estimated and the time periods in which the specific components of a model can affect its performance to be identified. However, one of the disadvantages of TVSA is its high computational cost, as it estimates sensitivity in a moving window within an analyzed series, performing a series of repetitive calculations. In this article a function to implement a simple TVSA with a low computational cost using regional sensitivity analysis is presented. As an example of its application, an analysis of hydrological model results in daily, monthly, and annual time windows is carried out. The results show that the model allows the time sensitivity of a model with respect to its parameters to be detected, making it a suitable tool for the assessment of temporal variability of processes in models that include time series analysis. In addition, it is observed that the size of the moving window can influence the estimated sensitivity; therefore, analysis of different time windows is recommended.

Determining Soil Hydraulic Properties Using Infiltrometer Techniques: An Assessment of Temporal Variability in a Long-Term Experiment under Minimum- and No-Tillage Soil Management

Conservation agriculture is increasingly accepted by farmers, but the modeling studies on agro-environmental processes that characterize these agricultural systems require accurate information on the temporal variability of the soil’s main physical and hydraulic properties. Therefore, specific investigations carried out in long-term experiments can increase our knowledge on the pros and cons of different measurement techniques. In this work, the simplified falling head (SFH) technique and the Beerkan Estimation of Soil Transfer (BEST) procedure were applied to investigate the temporal variability of some main soil physical and hydraulic properties, including bulk density (BD), field saturated hydraulic conductivity (Kfs), macroporosity (Pmac), air capacity (AC), plant available water capacity (PAWC), and relative field capacity (RFC). For this purpose, a long-term experiment was selected, and the experimental information obtained was used to verify the long-term impact (fifteen years) determined by two alternative forms of soil management, minimum tillage (MT) and no tillage (NT), for the cultivation of durum wheat. The main results of the comparison between MT and NT showed: (i) A comparable temporal variability in Kfs values when SFH was considered, given that in 75% of considered cases, the same result (i.e., significant or not significant) was obtained; (ii) a comparable temporal variability in Kfs values under MT (but not under NT) when both SFH and BEST were used, as a result of a possible Kfs,SFH overestimation under NT; (iii) differences in Kfs estimations by a factor of 6 or 7 (Kfs,SFH > Kfs,BEST) when comparable soil conditions (moisture and soil density) were considered; (iv) a comparable temporal variability when other soil indicators (BD, Pmac, AC, PAWC, and RFC) were simultaneously considered. After about fifteen years of field experiments characterized by continuous soil management and conducted with the methodological rigor typical of experimental farms, the SFH- and BEST-derived experimental information showed a substantial equivalence between MT and NT for the fine-textured soil investigated.

Hazardous trace elements in thoracic fraction of airborne particulate matter: Assessment of temporal variations, sources, and health risks in a megacity

The deleterious health effects of thoracic fractions seem to be more related to the chemical composition of the particles than to their mass concentration. The presence of hazardous materials in PM10 (e.g., heavy metals and metalloids) causes risks to human health. In this study, twelve trace elements (Cd, Cr, Pb, Zn, Cu, Ni, Sn, Ba, Co, As, V, and Sb) in 315 samples of ambient PM10 were analyzed. The samples were collected at an urban background site in a Latin American megacity (Bogota, Colombia) for one year. The concentrations and temporal variabilities of these elements were examined. According to the results, Cu (52 ng/m3), Zn (44 ng/m3), Pb (25 ng/m3), and Ba (20 ng/m3) were the traces with the highest concentrations, particularly during the dry season (January to March), which was characterized by barbecue (BBQ) charcoal combustion and forest fires. In addition, the differences between the results of weekdays and weekends were identified. The determined enrichment factor (EF) indicated that Zn, Pb, Sn, Cu, Cd, and Sb mainly originated from anthropogenic sources. Moreover, a speciation analysis of inorganic Sb (EF > 300) was conducted, which revealed that Sb(V) was the main Sb species in the PM10 samples (>80%). Six causes for the hazardous elements were identified based on the positive matrix factorization (PMF) model: fossil fuel combustion and forest fires (60%), road dust (19%), traffic-related emissions (9%), copper smelting (8%), the iron and steel industry (2%), and an unidentified industrial sector (2%). Furthermore, a health risk assessment of the carcinogenic elements was performed. Accordingly, the cancer risk of inhalation exposure to Co, Ni, As, Cd, Sb(III), and Pb was negligible for children and adults at the sampling site. For adults, the adjusted Cr(VI) level was slightly higher than the minimal acceptable risk level during the study period (1.4 × 10−6).

Muddying the Picture? Forecasting Particulate Sources and Dispersal Patterns in Managed Catchments

Satellite imagery and climate change projections improve our ability to map and forecast sediment sources and transport pathways at high resolution, which is vital for catchment management. Detailed assessment of temporal and spatial changes in erosion risk are key to forecasting pollutant dispersal, which affects water treatment costs and ecology. Outputs from scenario modeling of the River Derwent catchment, Yorkshire, indicate clear spatial and temporal trends in erosion risk. These trends are not picked up by using traditional methods, which rely on static land use maps. Using satellite-derived maps show that lower resolution traditional land-use maps relatively underestimate erosion risk in terms of location of source areas and seasonal variation in erosion risk. Seasonal variation in agricultural practices can be assessed by incorporating bare land variation into models, which show that erosion risk is relatively overestimated if all agricultural land is assumed to have the same character. Producing seasonal land use maps also allows the assessment of temporal variation in rainfall, which in combination with climate change projections allows for adaptable management plans. The bias in gradient in modeling, which assumes that high gradients result in greater sediment erosion risk, show that traditional models underestimate the contribution of erosion risk in lowland areas. This is compounded by the absence of artificial drainages in topographic rasters, which increases connectivity in lowland areas. By producing end member scenarios, model outputs help to inform where catchment management should be targeted, and whether seasonal interventions should be implemented. This information is vital to communicate with landowners when they implement catchment management practices, such as sediment traps and earth bunds. Adaption of erosion risk modeling practices is urgently needed in order to quantify the impact of artificial interference in which human activity disrupts ‘natural’ sediment source-to sink configurations, such as integrating new pathways and stores due to land use change and management. Furthermore, integrating higher resolution catchment modeling and improved seasonal forecasts of pollutant flux to oceans will permit more effective interventions. This paper highlights single output erosion risk maps are not effective to inform catchment management.

Organic micropollutants in groundwater of India-A review.

Groundwater pollution due to organic micropollutants is a major cause of concern, especially in parts of the world where available water resources are on the decline. India is the largest user of groundwater where the presence of micropollutants in the subsurface environment has been the focus of many researchers. The objective of this study was to provide a detailed review of studies on micropollutants in Indian groundwater and to provide strategies for further work. It is found that the presence of pharmaceuticals, endocrine disrupting compounds, surfactants, phthalates, per- and poly-fluoroalkyl substances, personal care products, artificial sweeteners, and pesticides in groundwater from different parts of India is reported. Pesticides and phthalate concentrations reported exceed the standard guideline values. This review points out the regions where the groundwater is prone to contamination due to micropollutants. An assessment of temporal variation in the concentration of micropollutants in groundwater has been done only by a few researchers. This study highlighted the need for more research on the possible presence of micropollutants in groundwater, especially in the major polluted rivers in cities where more pharmaceuticals, pesticides, and plastic industries are located. PRACTITIONER POINTS: Organic micropollutants were not new contaminants into the environment but the one entered even decades ago which has threatening effect. The number of studies on organic micropollutants in groundwater is lesser than surface water or wastewater. Scarcity on the studies of micropollutants was a result of definite technical lack in its analysis and complexity in sample preparation. Most of the studies done were related to contamination sites and point sources.

Assessments of Temporal Variations in Haplotypes of 'Candidatus Liberibacter solanacearum' and Its Vector, the Potato Psyllid, in Potato Fields and Native Vegetation.

The potato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), had been known for nearly a century to cause psyllid yellows of solanaceous crops. However, it has only been a decade since the insect was discovered to transmit the bacterium 'Candidatus Liberibacter solanacearum' (Lso), which putatively causes potato zebra chip disease. This project was initiated to quantify temporal incidences of haplotypes of the psyllid (Central, Southwestern, and Western) and Lso (A, B) in potato fields and in native vegetation. Psyllids were collected from native vegetation in Texas (2011-2014), and from potato fields in Texas and New Mexico (2014-2017). Psyllids were tested for Lso and haplotypes of both psyllid and Lso. In Texas, the Central psyllid haplotype was overwhelmingly dominant both in potato fields and in native vegetation regardless of location and time of collection. However, in New Mexico potato fields, although the Southwestern haplotype was overall dominant, the ratios of individual haplotypes varied among years and within a season. The Southwestern psyllid haplotype was greater in incidence than the Central early but declined later in the season in each of the 4 yr, while the Central haplotype was low in incidence early but increased over time. Lso was detected in all three psyllid haplotypes representing the first report in Southwestern psyllid haplotype. In Texas, Lso haplotype A was more frequently detected than B, but in New Mexico the incidence of positive psyllids was not high enough to make definitive conclusions regarding predominant Lso haplotype.

Long-term assessment of temporal variability in spatial patterns of early life stages of fishes to facilitate estuarine conservation

ABSTRACTEstuaries are among the most productive coastal ecosystems, supporting a wide variety of marine fishes and their early stages. High spatial and temporal variability in estuaries implies that management strategies must incorporate dynamic features to be efficient. In our study, we analysed 13 years of data on ichthyoplankton from the Patos Lagoon estuary (Brazil) to assess whether temporal variability can show distinct spatial patterns of fish eggs and larval distribution and to discuss how these results can be helpful to conservation planning. Spatial patterns of fish egg and larval assemblages were evaluated using cluster analysis. Indicator taxa for each group were also calculated as a product of the relative frequency and relative average abundance in each group. In addition, we used generalized linear models to analyse fish egg and larval abundance in relation to environmental variables. Results showed that fish eggs and larvae exhibit high variability among months, years and sampling stations in the time series. Temporal occurrence and spatial distribution were mainly associated with salinity. We found distinct spatial patterns for fish eggs and larvae in the Patos Lagoon estuary. Groups identified were different among years and indicated by a distinct genus. Our results can be considered as a first exploratory step to help managers to decide which species and temporal scale should be studied in detail and incorporated in management plans. Spatial conservation planning incorporating fluctuations in abundance and assemblage structure over time may help to ensure conservation for biodiversity persistence in highly dynamic ecosystems such as the Patos Lagoon estuary.

Intercomparison of dissolved iron isotope profiles from reoccupation of three GEOTRACES stations in the Atlantic Ocean

Intercomparison of trace metal data is a key aspect of the International GEOTRACES program, allowing data from multiple laboratories and countries to be combined to produce high-resolution datasets for the oceans. The use of crossover stations by the GEOTRACES program provides the opportunity both for comparison of analytical techniques and assessment of temporal variability in the cycling of trace metals such as iron (Fe). Here, we present the first comparison of dissolved Fe stable isotope ratio (δ56Fe; relative to IRMM-014) profiles in the oceans, from reoccupations of three locations in the Atlantic Ocean; (1) the Bermuda Atlantic Time Series station (31.75°N 64.17°W) during the US GEOTRACES IC1 cruise (June 2008) and the US GEOTRACES GA03 cruise (Nov. 2011); (2) the Tenatso Time Series station near Cape Verde (17.4°N 24.5°W) during the U.S GEOTRACES GA03 cruises (2010; 2011), and (3) a station in the Cape Basin close to South West Africa (31.1–31.4°S 36.5°W) during the French GEOTRACES GIPY4 Bonus Good Hope Cruise (Feb. 2008) and the UK GEOTRACES GA10 D357 cruise (Oct. 2010). These datasets provided us with the opportunity not only to compare sampling and analysis techniques by two different laboratories (USC and LEGOS), but also the temporal variability of δ56Fe at these locations on a 1–3year timescale. We found that a good agreement between data and profiles generated by different laboratories does allow assessment of temporal variation of δ56Fe in the water column, as well as spatial variability and synthesis of datasets from different regions of the ocean. In fact, comparison of δ56Fe at the three locations in this study demonstrates a remarkable consistency between the shapes of ocean δ56Fe profiles measured 1–3years apart, pointing to the overall stability of Fe cycling at all three locations on these timescales, despite the expected dynamic nature of the Fe cycle. This consistency is highlighted by strong agreement in δ56Fe throughout the whole water-column at Bermuda, and in waters deeper than 500m in the Cape Basin, which suggests that different water masses may carry distinct δ56Fe signatures. In contrast to these stable δ56Fe, we did observe apparent temporal variability in δ56Fe between cruises at other locations and in surface waters, both throughout the water column at Cape Verde, and in Agulhas-leakage influenced surface waters in the Cape Basin. Such temporal variability may thus provide information about changes in internal Fe cycling or external Fe sources on these timescales. Overall, this study highlights the usefulness of repeat δ56Fe measurements to provide information on the variability of Fe cycling throughout the oceans.

Temporal Variations in Dissolved Oxygen Concentrations Observed in a Shallow Floodplain Aquifer

AbstractDissolved oxygen (DO) concentrations play an important role in many groundwater biogeochemial processes, yet assessments of temporal variations are lacking. In this study, we examined daily DO concentrations using a continuously‐reading optical DO probe in a shallow floodplain setting in Iowa to (i) quantify fluctuations across two growing seasons; (ii) examine hydrologic controls on DO values; and (iii) model daily DO concentrations using easily measured variables. DO concentrations exhibited both rapid and long‐term changes in concentrations over time, rapidly increasing and decreasing more than 1 mg/l in response to precipitation recharge and stream stage increase over the span of several hours and days. On 40% of the monitoring days in this study, DO concentrations increased, on average, 0.2–0.4 mg/l from one day to the next. DO concentrations decreased approximately 5–6 mg/l from spring through late summer and fall, likely owing to microbial and root respiration. Daily DO concentrations were successfully modelled using a combination of hydrologic (groundwater level and river stage) and temperature variables (r2 > 0.7). Improved understanding of temporal controls on groundwater DO patterns is needed to help clarify the dynamics of many biogeochemical processes. Copyright © 2014 John Wiley & Sons, Ltd.

Nitrate source apportionment in a subtropical watershed using Bayesian model

Nitrate (NO3−) pollution in aquatic system is a worldwide problem. The temporal distribution pattern and sources of nitrate are of great concern for water quality. The nitrogen (N) cycling processes in a subtropical watershed located in Changxing County, Zhejiang Province, China were greatly influenced by the temporal variations of precipitation and temperature during the study period (September 2011 to July 2012). The highest NO3− concentration in water was in May (wet season, mean±SD=17.45±9.50mgL−1) and the lowest concentration occurred in December (dry season, mean±SD=10.54±6.28mgL−1). Nevertheless, no water sample in the study area exceeds the WHO drinking water limit of 50mgL−1 NO3−. Four sources of NO3− (atmospheric deposition, AD; soil N, SN; synthetic fertilizer, SF; manure & sewage, M&S) were identified using both hydrochemical characteristics [Cl−, NO3−, HCO3−, SO42−, Ca2+, K+, Mg2+, Na+, dissolved oxygen (DO)] and dual isotope approach (δ15N–NO3− and δ18O–NO3−). Both chemical and isotopic characteristics indicated that denitrification was not the main N cycling process in the study area. Using a Bayesian model (stable isotope analysis in R, SIAR), the contribution of each source was apportioned. Source apportionment results showed that source contributions differed significantly between the dry and wet season, AD and M&S contributed more in December than in May. In contrast, SN and SF contributed more NO3− to water in May than that in December. M&S and SF were the major contributors in December and May, respectively. Moreover, the shortcomings and uncertainties of SIAR were discussed to provide implications for future works. With the assessment of temporal variation and sources of NO3−, better agricultural management practices and sewage disposal programs can be implemented to sustain water quality in subtropical watersheds.

An assessment of temporal variations in physicochemical and microbiological properties of barmouths and lagoons in Chennai (Southeast coast of India)

Two estuary and two coastal lagoon stations along Chennai, Southeast coast of India were monitored for 1year to study both physicochemical and microbiological properties of the water. Influence of the marine environment over the systems was evident by elevated salinity levels. Considerable concentrations of total heterotrophic bacterial count and fecal bacteria such as total coliforms, fecal coliforms and fecal streptococci were observed throughout the study period which evinced a pattern of anthropogenic activities. Principle component analysis was employed for assessing the overall pattern of variation within the data sets. Climatic variation was highly correlated with changes in water quality, i.e. the Northeast monsoon and Summer had influenced considerably the microbial occurrence as well as the physicochemical parameters such as total suspended solids, chloride, sulphate and salinity. However, the effect of the Southwest monsoon was less prominent than the Northeast monsoon with its heavy rains. As both estuaries revealed elevated concentrations of polluted water, these stations can be used as indicators or alerts for the water quality along the coastal zone of Chennai.

Novel Assessment of Temporal Variation in Fractionated Electrograms Using Histogram Analysis of Local Fractionation Interval in Patients With Persistent Atrial Fibrillation

Background— The characteristics of atrial electrograms associated with atrial fibrillation (AF) termination are controversial. We investigated the electrogram characteristics that indicate procedural AF termination during continuous complex fractionated electrogram ablation. Methods and Results— Fifty-two consecutive patients with persistent AF (47 men; aged 54±9 years), who underwent electrogram-based catheter ablation in the left atrium and coronary sinus after pulmonary vein isolation, were enrolled. The intracardiac bipolar atrial electrogram recordings were characterized by (1) fractionation interval (FI) analysis (>6 seconds), (2) kurtosis (shape of the FI histogram), and (3) skewness (asymmetry of the FI histogram). Sites showing complex, fractionated electrograms (mean FI ≤60 ms) were targeted, and AF was terminated in 20 patients (38%) after the pulmonary vein isolation. The conventional complex fractionated electrogram sites (mean ≤120 ms) in patients with AF termination exhibited higher median kurtosis (2.69 [interquartile range, 2.03–3.46] versus 2.35 [interquartile range, 1.79–2.48]; P =0.024) and higher complex fractionated electrogram-mean interval (102.7±19.8 versus 87.7±15.0; P =0.008) than patients without AF termination. Furthermore, AF termination sites had higher median kurtosis than targeted sites without AF termination (5.13 [interquartile range, 3.51–6.47] versus 4.18 [interquartile range, 2.91–5.34]; P <0.01) in patients with procedural termination. In addition, patients with AF termination had a higher sinus rhythm maintenance rate after a single procedure than patients without AF termination (log-rank test, P =0.007). Conclusions— A kurtosis analysis using the FI histogram may be a useful tool in identifying the critical substrate for persistent AF and potential responders to catheter ablation.