Cumulative Frequency Distribution Curves Research Articles

Estuarine environmental flow assessment based on the flow-ecological health index relation model: a case study in Yangtze River Estuary, China.

Environmental flow (e-flow) is the water demand of one given ecosystem, which can become the flow regulation target for protection and restoration of river or estuarine ecosystems. In this study, an e-flow assessment based on the flow-ecological health index (EHI) relation model was conducted to improve ecosystem health of the Yangtze River Estuary (YRE). Monitoring data of hydrology, biology, and water environment in the last decades were used for the model establishment. For the description of the YRE ecosystem, an EHI system was developed by cumulative frequency distribution curves and adaption of national standards. After preprocessing original flow values into proportional flow values, the generalized additive model and Monte Carlo random sampling were used for the establishment of the flow-EHI relation model. From the model calculation, the e-flow assessment results were that, in proportional flow values, the suitable flow range was 1.05-1.35, and the optimum flow range was 1.15-1.25 (flows in Yangtze River Datong Station). For flow regulation in two crucial periods, flows of 42,630-65,545 m3/s or over 14,675 m3/s are needed for the suitable flow of YRE in summer (June-August) or January, respectively. An adaptive management framework of ecological health-based estuarine e-flow assessment for YRE was contrived due to the limitation of current established model when facing the extreme drought in summer, 2022. The methodology and framework in this study are expected to provide valuable management and data support for the sustainable development of estuarine ecosystems and to bring inspiration for further studies at even continental or global levels.

Evaluation of succulent plants Echeveria elegans as a biomonitor of heavy metals and radionuclides

This work evaluates the use of Echeveria elegans as a biomonitor of metals and radionuclides, using semi-urban soils as a study area. The study area is exposed to various trace elements of concern for various social groups in nearby localities. The quantification of metals and radionuclides was performed by X-ray fluorescence spectrometry and gamma spectrometry, respectively. Cumulative frequency distribution curves, descriptive statistics, and multivariate analysis were used to estimate the local geochemical baseline and identify geochemical and anthropogenic patterns of metals and radionuclides from topsoil and E. elegans. The evaluation of contaminants and the contribution of possible exposure routes (topsoil and atmospheric deposition) was performed with the enrichment factor (EF) and the relative concentration factor (CFR). The results suggest that the plant does not present significant physical stress due to the environmental conditions to which it was exposed. Likewise, it can bioaccumulate heavy metals from natural and anthropogenic sources. The quantification of radionuclides in the plant is below the detection limits, indicating a low bioavailability and transfer factor. The CFR and EF results showed that the plant accumulates metals from the topsoil and atmospheric deposition. The bioaccumulation mechanism would be related to the functioning of Crassulaceae Acid Metabolism (CAM). In topsoil, the organic acids of the plant would modify the solubility of the metals present in an insoluble form in the soil, acting as ligands and, subsequently, following the transport route of these metabolites. In atmospheric deposition, the metals deposited in the leaves would be incorporated into the plant through the opening of the stomata because of the capture of CO2 (at night, day, or during environmental stress) by the CAM. Overall, the evidence showed that the succulent can be used as a biomonitor of heavy metals. However, additional studies are required to determine its usefulness as a radionuclide biomonitor.

Age estimation and boulder population analysis of the West crater at Apollo 11 landing site using Orbiter High Resolution Camera on board Chandrayaan-2 mission

Orbiter High Resolution Camera (OHRC) on-board Chandrayaan-2 had acquired a high-resolution image (∼0.26 m) covering Apollo 11 landing site, showing the Lander Module (LM) along with other small-scale features, such as boulders, etc. In the east of Apollo 11 LM lies the West crater, which has a rich population of boulders spread around it. We studied this boulder distribution around the West crater to estimate the age of the West crater and to understand the aspects related to the impact cratering and space weathering through the analysis of boulder distribution. For this, we identified and mapped >8500 boulders around the West crater using the OHRC image, out of which 6466 boulders (>∼1 m in size) lying within 1–5 crater radius were used for further analysis. For estimating the age of the West crater, we applied various methods based on crater morphology, boulder distributions and Diviner Rock Abundance. The age was estimated to be in the range of 80 Ma to 120 Ma with the most probable age close to 100 Ma, the same as that expected from the cosmic ray exposure dating. Boulder distribution around the West crater was found to be highly anisotropic with majority of boulders lying in the eastern to north-eastern direction, suggesting an impact at very low angle. Relationship between crater size and largest boulder size also pointed towards primary origin of the West crater. The Height (H) to Diameter (D) ratio is estimated to be ∼0.25 considering all the boulders with diameter ≤ 4m, going up to 0.38 with comparatively poor correlation for boulders with diameter > 4m. The H/D ratio from Apollo mission photos for boulders around Apollo 11 LM is found to be approximately double that of the corresponding measurements from the OHRC image. We also fit a Power law and the Weibull distribution to the cumulative Boulder Size Frequency Distribution (BSFD) curve with Maximum Likelihood (ML) method and Kolmogrov-Smirnoff (KS) statistics. Both fit well with R2 of 0.999, but varying minimum diameter (dKS) of 1.85 m and 1.64 m, respectively. The good fit by Power-law with high slope value (b = 4.61) describes the fragmentation due to the West crater forming impact as complex. However, the higher diameter tail was better explained by the Weibull fit implying sequential fragmentation of boulders with time.

Coastal sediment heavy metal(loid) pollution under multifaceted anthropogenic stress: Insights based on geochemical baselines and source-related risks

Contamination and risk assessments generally ignore the potential bias in results caused by the variation of background values at different spatial scales due to the spatial heterogeneity of sediments. This study aims to perform quantitative source-ecological risk assessment via establishing geochemical baselines values (GBVs) of heavy metal(loid)s (HMs) in Daya Bay, China. Cumulative frequency distribution (CFD) curves determined the GBVs of 12.44 (Cu), 30.88 (Pb), 69.89 (Zn), 0.06 (Cd), 47.85 (Cr), 6.80 (As), and 0.056 mg kg−1 (Hg), which were comparable to the background values of Guangdong Province surface soils, and implied a potential terrestrial origin of the coastal sediments. Principal component analysis (PCA) and positive matrix factorization (PMF) identified three sources (F1: natural processes; F2: anthropogenic impacts; F3: specific sources) with contributions of 51.7%, 29.2%, and 19.1%, respectively. The source-specific risk assessment revealed an ecological risk contribution potential of 73.8% for the mixed anthropogenic sources (F2 + F3) and only 26.2% for natural processes. Cd and Hg were the priority management of metallic elements, occupying 63.5% and 72.5% of the contribution weights of F2 and F3, respectively, which showed multi-level pollution potentials and ecological risk levels. The spatial distribution patterns demonstrated the hotspot features of HM pollution, and priority concerns should be given to the management of marine traffic and industrial point source pollution in Daya Bay. The results of the study provide a scientific approach and perspective for pollution treatment and risk management in the coastal environment.

Geographic distribution of arsenic contamination in the Himalayan Rivers flowing through Pakistan: Implications for its natural source and effects of anthropogenic activities

Arsenic (As) in natural hydrological systems is known as a worldwide major environmental concern. A geochemical and sedimentological study was done to ascertain the origin and geographical distribution of As in surface water and fluvial sediment collected from the floodplains/basins of the River Indus and its four major tributaries that drain through the northern Pakistan. The hydrogeochemical compositions of all five rivers were similar with calcium (Ca2+) and bicarbonate (HCO3−) being the dominating ions. The concentration of As ranged from 0.62–24.05 μg/L (average 3.7 ± 3.5 μg/L, n = 61) in river water, 2.3–23.4 mg/kg (average 5.7 ± 3.9 mg/kg) in suspended sediment, and 2.0–13 mg/kg (average 4.13 ± 2.3 mg/kg) in fluvial sediment. Various approaches were used, including mineralogical, sequential extraction, geochemical, and statistical analyses to investigate the distribution, behavior, and potential sources of As in the sediment. The effect of geological factors on the distribution of As was also studied. No noticeable changes in the relative abundance of minerals were observed in the sediment at different locations along the river. Both mineralogical and statistical analyses showed that silicate minerals like muscovite, biotite, and chloride are the main As reservoir while oxides minerals like hematite and magnetite, which are minor components in the sediment are second largest As carrier. A geochemical baseline, using the normalization and cumulative frequency distribution curves was constructed for As. The estimated mean human contribution of As was 3.4% in the Indus River, 1.9% in the Jhelum River, 13.7% in the Chenab River, 17.5% in the Ravi River and 5.4% in the Sutlej River, indicating relatively higher effects of anthropogenic activity along the Chenab River and Ravi River. The almost negligible effects of anthropogenic activities were additionally confirmed through the pollution assessment parameters estimated from the geo-enrichment, contamination factors, and accumulation index analyses. The current data suggest that As transported by the Indus River and its major tributaries is accumulated in the sediment and is potentially incorporated in the sedimentary aquifers situated along the Indus Basin and surrounding areas. Based on the current study, it is concluded that the source of As is dominantly geogenic whereas the role of anthropogenic activities is considered negligible except along the Ravi River which showed relatively a higher percentage (17.5%) of human or industrial contribution.

Enrichment of High Arsenic Groundwater Controlled by Hydrogeochemical and Physical Processes in the Hetao Basin, China.

Based on 447 samples collected from a shallow aquifer (depths from 0 to 150 m) in the Hetao Basin, Northern China, an integrated hydrogeochemical approach was used in this study to conceptualize the enrichment of high arsenic groundwater in the Hetao Basin. An unconventional method of distinguishing hydrogeochemical and physical processes from a dataset was tested by investigating the cumulative frequency distribution of ionic ratios expressed on a probability scale. By applying cumulative frequency distribution curves to characterize the distribution of ionic ratios throughout the Hetao Basin, hydrogeochemical indicators were obtained that distinguish the series of hydrogeochemical processes that govern groundwater composition. All hydrogeochemical processes can basically be classified as recharge intensity of groundwater, evaporation concentration intensity, and reductive degree controlling the spatial distribution of arsenic. By considering the three processes, we found that the concentration of arsenic was more than 10 μg/L when the (HCO3-+CO32-)/SO42- ratio was over 4.1 (strong reductive area). As the evaporation concentration intensity increased, the median value of arsenic increased from 10.74 to 382.7 μg/L in the median reductive area and rapidly increased from 89.11 to 461.45 μg/L in the strong reductive area. As the river recharge intensity increased (with the intensity index increasing from 0 to 5), the median value of arsenic dropped from 40.2 to 6.8 μg/L in the median reductive area and decreased more markedly from 219.85 to 23.73 μg/L in the strong reductive area. The results provide a new insight into the mechanism of As enrichment in groundwater.

662 Physiological and angiographic outcomes of PCI in calcified lesions after rotational atherectomy or intravascular lithotripsy

Abstract Aims Percutaneous coronary interventions (PCI) in calcified coronary artery lesions are associated with impaired stent expansion, higher rate of periprocedural complications and cardiac mortality. Lesion preparation using calcium modifying techniques such as Rotational Atherectomy (RA) or Intravascular Lithotripsy (IVL) has been advocated. Studies comparing these technologies are lacking. We aimed to compare the in-stent pressure gradient, evaluated by virtual fractional flow-reserve, in calcific lesions treated using either RA or IVL. Methods and results Patients undergoing either RA- or IVL-assisted PCI from two European centres were included. Propensity score matching (1:2) was performed to control for potential bias. Primary outcome was post-PCI in-stent pressure gradient calculated by virtual fractional flow reserve (vFFRgrad). Secondary outcomes included the proportion of patients with complete functional revascularization defined as of distal vFFR post PCI (vFFRpost) ≥0.90. From a cohort of 210 patients, 105 matched patients (70 RA and 35 IVL) were included. Pre-PCI vFFR did not differ between groups (0.65 ± 0.13 RA and 0.67 ± 0.11 IVL). After PCI, in-stent pressure gradients was significantly lower in the IVL group (0.032 ± 0.026 vs. 0.043 ± 0.026 in the RA group, P = 0.024). The proportion of vessels with functional complete revascularization was similar between the two groups (32.9% vs. 37.1% in the RA and IVL group, respectively; P = 0.669). Conclusions Calcific lesions preparation with IVL is effective and resulted in improved in-stent pressure gradient compared to RA. Approximately one third of the patients undergoing PCI for a severely calcified lesion achieved functional revascularization with no difference between rotational RA and IVL. 662 FigureIn stent gradients after RA and IVL. (A) Box plot depicting the distribution of the in-stent pressure gradient vFFRgrad between the two groups. (B) Cumulative frequency distribution curves demonstrating lower vFFRgrad after intravascular lithotripsy compared to rotational atherectomy. RA, rotational atherectomy; IVL, intravascular lithotripsy; vFFRgrad, in-stent pressure gradient.

Threshold value estimation of journey-distance using generalized polynomial function

The present work demonstrates an experience in estimating the threshold value of journey distances travelled by transit passengers using generalized polynomial function. The threshold value of journey distances may be defined as that distance beyond which passengers might no more be interested to travel by their reported mode. A knowledge on this threshold value is realized to be useful to limit the upper-most slab of transit fare, while preparing of a length-based fare matrix table. Theoretically, the threshold value can be obtained at that point on the cumulative frequency distribution (CFD) curve of journey distances at which the maximum rate of change of the slope of curve occurs. In this work, the CFD curve of the journey distance values is empirically modelled using Newton’s Polynomial Interpolation method, which helps to overcome various challenges usually encountered while an assumption of a theoretical probability distribution is considered a priori for the CFD.

An integrated exploration on health risk assessment quantification of potentially hazardous elements in soils from the perspective of sources

To make pollution evaluation of potentially hazardous elements in the soil more accurately, the regional geochemical baseline concentrations of eight potentially hazardous elements (Cr, Ni, Cu, Zn, As, Cd, Hg, and Pb) were established in Huilai County using cumulative frequency distribution curves. Then, the pollution load index and enrichment factor were applied to estimate the contamination levels, based on these geochemical baseline concentrations. The results suggested that topsoil was moderately polluted by potentially hazardous elements, while Cd pollution in the construction land and As pollution in the farmland was relatively severe. The possible sources of eight potentially hazardous elements were analyzed by correlation analysis, geostatistics and positive matrix factorization. Four sources have been determined and apportioned, namely industrial activities, natural sources, agricultural practices, and traffic emissions. Combining the health risk assessment with the source profiles, the health risks quantified from four sources were estimated under farmland, construction land, and woodland. The results showed that agricultural practices were the most main source of non-cancer and cancer risks under woodland and farmland for adults; industrial activities were the most main source of non-cancer and cancer risks under construction land for adults. Children's health risks, both carcinogenic risk and non-carcinogenic risk, were greater than adults, and the health risk trends of adults and children showed similarities. Therefore, agricultural practices under woodland and farmland should be controlled and managed as a priority, while industrial activities should be given priority to control and management under construction land.

Analysis of global positioning system based bus travel time data and its use for advanced public transportation system applications

The rapid advancements in sensor technologies has resulted in the increased use of Automatic Vehicle Location (AVL) systems for traffic data collection. Global Position System (GPS) sensors are the most commonly used AVL system, majorly because of it being a time-tested technology and being relatively cheap. Also, many of the transportation agencies have their vehicles equipped with GPS sensors. One of the interesting challenges in the field of Intelligent Transportation Systems (ITS) is to effectively mine useful information from such large-scale database accumulated over time. The current study analyses travel time data obtained from buses fitted with GPS devices in Chennai, India to understand its variation over time and space to find the spatial and temporal points of criticality. For this, Cumulative Frequency Distribution (CFD) curves, bar charts and boxplots were used. Inter-Quartile Range (IQR) was used as a measure to quantify the variations in travel time. Analysis showed that both travel time and its variation increased approximately 10% and 40%, respectively, from 2014 to 2016. This increase was observed to be primarily concentrated in six critical intersections during morning and evening peak hours. The findings from the study were further used in demonstrating possible user applications that can improve the efficiency of public transportation systems. As part of this, a real-time bus travel time prediction method was developed using a deep learning approach, Long and Short-Term Memory (LSTM) networks. Along with this, a robust fleet management system was also developed to check the adequacy of buses along the study corridor for different time of the day.

Characterizing pollution and source identification of heavy metals in soils using geochemical baseline and PMF approach

It is necessary to establish local geochemical baseline concentrations (GBCs) due to the lack or the inapplicability of regional background values in the study area. The establishment of GBCs of heavy metal (HM) in soil helps in making the accurate assessment of pollution, and then provides a basis for pollution control. Based on this, a case study was undertaken to study the GBCs of the Jiedong District, Guangdong Province, China. In this research, cumulative frequency distribution curves were utilized to determine the local GBCs in the subsoils. The determined GBCs of Cr, Hg, As, Pb, Ni, Cd, Cu, Zn, Co and V were 39.91, 0.072, 11.48, 47.62, 12.70, 0.17, 14.22, 64.54, 6.31, and 68.14 mg/kg, respectively. The average concentrations of Hg, As, Pb, Cd, Cu and Zn in the topsoils exceeded the corresponding baseline concentrations. In particular, the contents of Cd and Hg were 1.53 and 2.22 times higher than GBCs. According to this baseline criterion, enrichment factor (EF), pollution load index (PLI) and ecological risk index (RI) were applied to assessing HM pollution. EF and PLI suggested that most areas were under moderate contamination, while Hg and Cd pollution was more serious. And the RI values presented that the potential ecological risks were low in most parts of the study area. The possible origins of HMs were identified by combining positive matrix factorization with EF and geostatistics. Comprehensive analysis indicated that Hg and Cd were related to industrial activities, such as textile and garment processing, plastic and rubber production and metal manufacturing. Arsenic and part of Cu mainly came from agricultural activities, namely the use of pesticides, fertilizers and livestock manures. Lead and Zn were mainly attributed to traffic emissions. Chromium, Ni, V, Co, and part of Cu were originated from natural source controlled by parent materials. The corresponding contributions of these sources were 20.61%, 24.20%, 19.22% and 35.97%, respectively. This work provides information to prevent and control the soil HM pollution by proposing the efficient management of anthropogenic sources.

Effects of Compound Sand Barrier for Habitat Restoration on Sediment Grain-size Distribution in Ulan Buh Desert

Wind erosion is a huge challenge for ecologists to stabilize sand dunes and to change them into stable productive ecosystems. In order to better understand its role in the process of ecological restoration, the sediment grain-size characteristics of compound sand barrier were evaluated through field experimental observation. The results indicated that the compound sand barrier was mainly composed of extremely fine sand and fine sand, and the fine sand and extremely fine sand in the inner side were higher than the east and west sides of the compound sand barrier. Due to the blocking effect of compound sand barrier, the Sorting Coefficient became better, the Skewness belonged to the positive deviation and the Kurtosis presented leptokurtosis distribution. Moreover, while the cumulative frequency distribution curve in the inner side became steeper, the slope increased and reached the top of the curve ahead of time. The effect of wind environment and vegetation coverage on the surface sediments showed that the average annual wind velocity and vegetation coverage was negatively correlated with the average grain-size, but positively correlated with the Sorting Coefficient. There was a significant correlation among the annual wind speed, vegetation coverage, average grain-size and Sorting Coefficient, which indicated that vegetation coverage and wind environment was the key factor leading to the difference of surface sediments in this area. Collectively, the establishment of compound sand barrier is one of the most effective methods of sand-fixing with engineering measure in the arid desert regions. Therefore, given the complexities of agricultural systems, stubble retention and black film covered during harvesting and incorporation of the stubble into soil in the next spring appears to be the best choice in the dry northern China where farmlands suffer serious wind erosion.

Formula omitted] concentrations in a multifamily building in Porto, Portugal: Occupants' exposure and differential performance of mechanical ventilation control strategies

Adequate supply of fresh outdoor air is important to create healthy and comfortable indoor building environments. Currently, most of the residential buildings in mild climate European countries, such as Portugal or Spain, remain naturally ventilated. Distinct concerns have emerged in the building community regarding the indoor air quality (IAQ) in these buildings since several studies have shown that they are often poorly ventilated. The main cause has been identified as occupants' different window opening behavior, which can vary notably from one apartment to the next. This work presents a comparative method for evaluating occupants' exposure to CO2 concentration levels in existing buildings based on the comparison of cumulative frequency distribution curves. Indoor CO2 concentration levels recorded over 17 months in the bedrooms and living rooms of eight apartments of a naturally ventilated residential building located in Porto (Portugal) were used as experimental input data for developing the method and to calibrate the IAQ performance of an EnergyPlus building model. The calibrated building model exhibited a good agreement with the recorded data on the apartments, reporting maximum Root Mean Square Errors (RMSE) for the majority of the apartments below 5% and 10% for the living rooms and bedrooms, respectively.

Characterization of contamination levels of heavy metals in agricultural soils using geochemical baseline concentrations

It is currently very difficult to accurately evaluate the soil contamination by heavy metals (HMs) attributed to the unavailability of local geochemical background values (LGBVs). This study was performed to establish the geochemical baseline concentrations (GBCs), as an alternative for LGBVs to use for HM pollution assessment of agricultural soil. GBCs of the HMs selected were determined using the cumulative frequency distribution curves (CFDCs). GBCs were then used to pursue the HM soil pollution and associated ecological risks, via calculation of geo-accumulation indices (Igeo), pollution load indices (PLI), as well as potential ecological risk indices (RI). As to the soil investigated, the GBCs of Ni, Zn, Pb, and Cr were 29.34 mg/kg, 45.54 mg/kg, 21.81 mg/kg, and 33.65 mg/kg, respectively. Igeo values ranged from − 4.58 to 0.33 (Ni), from − 2.46 to 2.14 (Zn), from − 5.32 to 0.77 (Pb), and from − 3.83 to 0.96 (Cr), suggesting that the region was not polluted by these HMs. PLI values ranged from 0.08 to 2.45 with an average of 1.02. 49.6% of soil samples had the PLI values > 1.0, indicating that some of the soil may be moderately contaminated by HMs. The RI values of selected HMs were < 150, indicating a low potential ecological risk. Principal component analysis (PCA) implied Zn, Pb, and Cr were mainly sourced from parent (geological) materials, as well as agricultural activities, atmospheric deposition, etc., depending on the element. The present study illustrates the necessity of the characterization of GBCs at a regional scale, allowing for more accurate assessment of soil contamination by HMs. We hope that this will eventually lead to further development of better environmental management practices for agricultural soil polluted by HMs.

Arsenic pollution of sediments in China: An assessment by geochemical baseline

Arsenic (As) contamination in sediments has been reported worldwide. However, few studies have investigated As contamination on a national scale in China. This study aims to address this gap by analyzing the existing literature on As contamination and sediment samples collected from ten main river basins: the Songhua River Basin (SRB), Liao River Basin (LRB), Hai River Basin (HRB), Yellow River Basin (YRB), Huai River Basin (HuRB), Yangtze River Basin (YtRB), Pearl River Basin (PRB), Southeastern River Basin (SeRB), Southwestern River Basin (SwRB), and Northwestern River Basin (NwRB). Regional geochemical baseline (RGB) values of As in the sediments of river basins were calculated to estimate human contributions of As using normalization and cumulative frequency distribution curves. The established RGB values in the SRB, YtRB, and PRB were higher than the corresponding regional soil background (RSB), possibly because of the high intensity of human activities in the SRB, YtRB, and PRB. Taking RGB and RSB values as the background references, contamination assessment yielded important information on As contamination in China. With high As contributions from Yunnan province, the PRB suffered from the highest level of contamination, and the mean human contribution of As in the PRB was 64.4%. The contamination levels in the less developed southwestern regions were even higher than in some river basins in economically developed regions (e.g., YRB). In addition, As in the PRB and YtRB was found to be partially contributed by industrial wastewater discharge, and the response of As contamination in sediments to industrial wastewater discharge was analyzed. The temporal change (2004–2016) of As in sediments from the PRB, YtRB, and YRB corresponded well with that of As discharged in wastewater within the corresponding river basins. This study thus serves as a valuable foundation for policies focused on ameliorating As contamination in China.

River flow availability for environmental flow allocation downstream of hydropower facilities in the Kafue Basin of Zambia

The Government of the Republic Zambia (GRZ) will install a new hydropower station Kafue Gorge Lower downstream of the existing Kafue Gorge Station (KGS) and plans to start operating the Itezhi-Tezhi (ITT) hydropower facility in the Kafue Basin. The Basin has significant biodiversity hot spots such as the Luangwa National park and Kafue Flats. It is described as a Man-Biosphere reserve and the National Park is a designated World Heritage Site hosting a variety of wildlife species. All these natural reserves demand special protection, and environmental flow requirements (e-flows) have been identified as a necessary need to preserve these ecosystems. Implementation of e-flows is therefore a priority as Zambia considers to install more hydropower facilities. However before allocation of e-flows, it is necessary to first assess the river flow available for allocation at existing hydropower stations in the Kafue Basin. The river flow availability in the basin was checked by assessing the variability in low and high flows since the timing, frequency and duration of extreme droughts and floods (caused by low and high flows) are all important hydrological characteristics of a flow regime that affects e-flows. The river flows for a 41 year monthly time series data (1973–2014) were used to extract independent low and high flows using the Water Engineering Time Series Processing Tool (WETSPRO). The low and high flows were used to construct cumulative frequency distribution curves that were compared and analysed to show their variation over a long period. A water balance of each hydropower station was used to check the river flow allocation aspect by comparing the calculated water balance outflow (river flow) with the observed river flow, the hydropower and consumptive water rights downstream of each hydropower station. In drought periods about 50–100 m3/s of riverflow is available or discharged at both ITT and KGS stations while as in extreme flood events about 1300–1500 m3/s of riverflow is available. There is river flow available in the wet and dry seasons for e-flow allocation at ITT. On average per month 25 m3/s is allocated for e-flows at ITT for downstream purposes. On the other hand, it may be impossible to implement e-flows at KGS with the limited available outflow (river flow). The available river flow from ITT plays a very vital role in satisfying the current hydropower generating capacity at KGS. Therefore, the operations of KGS heavily depends on the available outflow (river flow) from ITT.

Geochemical baseline establishment and ecological risk evaluation of heavy metals in greenhouse soils from Dongtai, China

Currently, heavy metal (HM) contamination in greenhouse soils is a significant concern due to the rapid expansion of greenhouse agriculture. However, it is difficult to accurately assess HM pollution in greenhouse soils in China due to the lack of local geochemical baseline concentrations (GBCs) or corresponding background values. In the present study, the GBCs of HMs in Dongtai, a representative greenhouse area of China, were established from subsoils using cumulative frequency distribution (CFD) curves. The pollution levels of HMs and potential ecological risks were investigated using different quantitative indices, such as geo-accumulation index (Igeo), pollution index (PI), pollution load index (PLI) and ecological risk index (RI), based on these regional GBCs. The total concentrations of six metals (Cd, Cr, Cu, Ni, Pb and Zn) in surface soils were determined and shown to be lower than the concentrations reported in other greenhouse regions of China. The GBCs of Cd, Cr, Cu, Ni, Pb and Zn were 0.059–0.092, 39.20–54.50, 12.52–15.57, 20.63–23.26, 13.43–16.62 and 43.02–52.65mgkg−1, respectively. Based on this baseline criterion, Cd, Pb and Zn accumulated in the surface soils because they were present at concentrations higher than their baseline values. The soils were moderately polluted by Cd according to the Igeo values, and the PI results indicated that moderate Cd contamination was present in this area. The large variation of Igeo value of Cd revealed that Cd in this area was likely influenced by agricultural activities. The PLI showed that most of the study area was moderately polluted. However, an analysis of the RI showed that the investigated HMs had low ecological risks. Correlation analysis and principle component analysis suggested that the Cd, Pb and Zn in the greenhouse soils mainly originated from anthropogenic sources (agricultural activities, atmospheric deposition etc.), while Cr, Cu, and Ni originated from natural sources. The findings of this study illustrated the necessity of GBC establishment at the local scale to facilitate more accurate HM evaluation of greenhouse soils. It is advisable to pay more attention to Cd, which could cause environmental problems in the greenhouse system.

Prognostic values of blood pH and lactate levels in patients resuscitated from out-of-hospital cardiac arrest.

AimEarly prediction of prognosis after out‐of‐hospital cardiac arrest (OHCA) remains difficult. High blood lactate or low pH levels may be associated with poor prognosis in OHCA patients, but these associations remain controversial. We compared blood lactate and pH levels in OHCA patients transferred to our hospital to measure their prognostic performance.MethodsWe investigated the associations between blood lactate and pH levels on admission and neurological outcomes in 372 OHCA patients who had a return of spontaneous circulation.ResultsOf the 372 OHCA patients, 31 had a favorable neurological outcome. Blood lactate levels were lower in patients with a favorable outcome than in those with an unfavorable outcome, but this difference did not reach statistical significance (82 ± 49 vs. 96 ± 41 mg/dL). However, pH levels were significantly higher in patients with a favorable outcome than in those with an unfavorable outcome (7.26 ± 0.16 vs. 6.93 ± 0.19, P < 0.001). The relative cumulative frequency distribution curve analysis showed the optimal cut‐off points of lactate and pH to be approximately 80 mg/dL and 7.05, respectively. Sensitivity and specificity to predict a favorable outcome were 61% and 64% for lactate <80 mg/dL and 84% and 80% for pH >7.05, respectively. Areas under receiver–operating characteristic curves were significantly larger for pH than for lactate levels (P < 0.001). In multivariate analysis, pH >7.05 was an independent predictor for a favorable outcome.ConclusionAfter OHCA, patients with a favorable outcome had lower lactate and higher pH levels than those with an unfavorable outcome, but pH level was a much better predictor for neurological outcome than lactate levels.

Experimental study of the fragmentation characteristics of brittle rocks by the effect of a freefall round hammer

The dynamic fragmentation of brittle rocks (slate, granite, marble and limestone) under low-velocity impact was investigated using freefall round hammer experiments. A three-parameter generalized extreme value distribution was used to characterize the fragment sizes, and the finest particles were neglected. A $$\hbox {log}_{10}$$ transformation of fragment size was adopted to overcome the problem that the interval of adjacent fragments size increases as the fragment size grows. The results reveal that the frequency distributions and num-based cumulative frequency distributions based on number have a certain change law with variations in impact energy and hammer size; the frequency distribution curve became narrower, and the cumulative frequency distribution curve moved toward the left as the impact energy increased, and the hammer size decreased. Marble was most easily broken followed by granite, limestone and slate, which was proved by scanning electron microscope images of the fracture surfaces of the four rocks. Because fragmentation is a stochastic process, the equivalent diameters of the fragments always had a more obvious regularity than the major and minor axes in the histograms. Therefore, the mean value of the equivalent diameter was used as the experimental average fragment size. Comparing the experimental results with the theoretical results of average fragment sizes that were predicted by four normalized models, it was determined that Levy and Molinari’s model and Zhou et al.’s model better forecasted the fragment sizes.

Size distribution, morphology and fractal characteristics of brittle rock fragmentations by the impact loading effect

The dynamic fragmentation of three types of brittle rock is examined in this paper by impact experiments using the split Hopkinson pressure bar system. The generalized extreme value distribution is used to characterize the size distribution of the fragments. The results indicate that the slate particles are shaped as a sheet, sandstone fragments appear as irregular prisms, and granite is shaped as a fine grain. Granite is the specimen most easily broken followed by sandstone and slate. The NUM-based cumulative frequency distribution curve moves toward the left as the impact stress increases. Fitted curves of the size distribution of the granite fragments are more intensive at the section of relatively small particle size and become sparser when the particle sizes increase, contrary to the sandstone and slate. Moreover, the aspect ratio of the granite fragments is smaller and more intensive than the other two specimens, even under simple impact conditions. Peak values in the probability density function curves of the fragment size are consistent with the theoretical results. Fractal theory is further used to study the fragmentation features. The results show that the fractal dimension value increases with increased specimen stress, and the fragments of slate and sandstone have smaller values than the granite within a certain range. Additionally, the value is also limited by the fragment size distribution, and the fractal dimension value increases as the dominant fragment size decreases.