Combined Effect Of Water Research Articles

Low‐Velocity Structure of Subducted Oceanic Crust in the Upper Mantle: Insights From High Pressure and Temperature Elasticity Measurements of Aragonite

AbstractThis study examines the effects of water and carbon on the velocity profiles of subducted oceanic crust in the upper mantle. High pressure and temperature Brillouin measurements were conducted to determine the single‐crystal elasticity of aragonite (CaCO3) up to 20 GPa and 600 K, respectively. Using the finite‐strain method, we determined the elastic parameters: KS0 = 70.7 GPa, G0 = 36.1(3) GPa with KS′ = 5.0(1), G′ = 1.3(1), ∂KS/∂T = −0.020(2) GPa/K, and ∂G/∂T = −0.015(1) GPa/K. When combined with literature results, our findings reveal that neither hydrous minerals nor carbonate alone can explain the observed 3%–4% and 3%–7% low velocity anomalies in the compressional (VP) and shear‐wave (VS) velocities of subducted oceanic crust in the circum‐Pacific region at 150–250 km depth. Considering the combined effect of water and carbonate, the addition of 5.9–6.9 vol.% aragonite together with 10 vol.% lawsonite in the oceanic crust can produce a 3%–4% and 6.1%–8.1% low velocity anomalies in the VP and VS at 150–250 km depth, respectively, consistent with the seismic observations in the region. Complete dehydration of lawsonite accompanied by the gradual decarbonization of the subducted oceanic crust explains the absence of low‐velocity anomalies below 300‐km depth. Our findings help for a better understanding of the possible influence of carbon and water on seismic velocities of the mantle. As a result, the circulation of carbon and water may be better understood while taking the complex velocity structure of subduction zones and mineral physics findings into account.

Experimental and numerical evaluation of hydro-thermal ageing's effects on adhesive connections in offshore structures

In offshore structures, the need to replace or strengthen existing metal components arises over time. One possible solution is the use of bonded connections. Nevertheless, the durability of the adhesive connections is highly compromised by the prolonged contact with water.In this paper, an experimental and numerical evaluation of hydro-thermal ageing's effects on polyurethane adhesive connections has been analysed. An efficient semi-analytical procedure is developed for the design or verification of existing structures reinforced by bonded steel elements. The model can evaluate the interfacial shear stress at all loading stages up to the failure of bonded joints exposed to the marine environment. The model is based on Bernoulli beam theory and satisfies the requirements of equilibrium and strain compatibility, allowing for interfacial deformations.Furthermore, the mechanical behaviour of bonded connections subject to accelerated ageing has been experimentally investigated. More in detail, an experimental program including double lap shear and end-notch flexure tests was performed to evaluate the cohesive behaviour in Mode II of a polyurethane structural adhesive under the combined effects of water and temperature during 150 days of exposure. The experimental and numerical investigation shows how the performance of the adhesive joints is influenced by the ageing conditions.

The pretreatment of hydrous pyrolysis on the synthetic graphitization of coal: Insights into temperature, pressure, and water

Unlike natural graphitization, synthetic graphitization, which is a fast heating process, lacks pressure and fluids. To understand the importance of water and pressure, a hydrous pyrolysis pretreatment was designed. The temperature, pressure, and water can all be controlled as variables. Natural coal with a degree of metamorphism similar to that of the pretreated coal was also prepared. The yield, degree of graphitization, stacking height, lateral size, and defect degree of the aromatic rings for the corresponding products after synthetic graphitization were evaluated using 13C NMR, FT-IR spectroscopy, XRD, and Raman spectroscopy.Higher temperatures and pressures in the hydrous pyrolysis pretreatment are beneficial for the yield and structure of the graphitized products. The role of hydrous pyrolysis is similar to that of natural thermal evolution; however, the yield and structure of the graphitized products from the pretreated coal are slightly worse. The presence of water during pretreatment is important. As a hydrogen donor, water increases the fluidity of the thermoplastic stage. Water pressure can break the microporous structure and render the aromatic layer more orderly. Therefore, hydrous pyrolysis pretreatment proves that the combined effect of water and pressure can improve the synthetic graphitization ability of coal, even under low-temperature conditions. A combination of hydrous pyrolysis and synthetic graphitization was found to be suitable.

Thermo-aqueous coupling behaviors for shape memory hydrogels: A statistical–mechanical model and simulations faced with experiments

The shape memory behavior of hydrogels endows themselves with the capacities of shape programming and shape recovering, which have great potential in many fields, such as drug release and soft robotics. In thermally responsive hydrogel, particularly, there are two critical factors, temperature and water, that can induce the shape memory effect(SME). Temperature-induced SME has been extensively studied, while water-induced SME has been rarely investigated. In our work, the combined effect of water and temperature on shape memory behavior of hydrogels is experimentally studied and deeply analyzed from a physical perspective. We found that the shape fixed ratio of shape memory hydrogels (SMHs) increases monotonically with temperature, but first increases and then decreases with water content. Moreover, it exits a nonlinear coupling between the water and temperature effects on the SME. On the basis of these findings, a constitutive model is developed to capture this thermo-aqueous coupling using the statistical theory of transient networks, from which we obtain an explicit evolution equation of deformation gradient. In the proposed theory, the temperature-induced SME is investigated through the temperature-water responsive association and dissociation of dynamic bonds while the water-induced SME is explained by the variation of the glass transition temperature according to the Fox–Flory model. Finally, and to provide a final test of the theoretical work, it is implemented into a user element (UEL) subroutine which provide simulations in agreement with our experiments. Our work is expected to provide guidance for future application of SMHs.

Lag response of groundwater to changes in water and sediment characteristics in the lower Yellow River, China

• XLD operation decreased groundwater level along the lower Yellow River. • The highest groundwater level was delayed after XLD operation. • Inter-annual changes in groundwater were mainly determined by WL, SSC, and ISC. • Response of groundwater to changes in water–sediment lagged by 2–5 months. The process of water exchange between rivers and groundwater is critical for the circulation of material and energy; however, this process is strongly affected by dam-regulated water and sediment. The lower Yellow River seeps downward throughout its coarse and suspended (perched) riverbed and feeds the surrounding floodplain groundwater. The Xiaolangdi Dam (XLD) and water–sediment regulation scheme (WSRS) have altered the exchange processes between river and groundwater along the lower Yellow River. However, few researchers have examined the response of this river-fed groundwater system to the operation of the XLD and implementation of the WSRS. As such, in this study, we analyzed the responses of groundwater to changes in flow and sediment characteristics based on statistical analysis using historical data, extremely randomized tree models, and distributed lag non-linear models. We found that, since the XLD began operating in 2002, the groundwater level near the lower Yellow River substantially decreased, and the groundwater level in June significantly decreased (at the 0.05 level). The highest groundwater level in the pre-dam period occurred in August, whereas the highest level in the post-dam period occurred in October. Changes in the annual groundwater level and in the mid- and post-WSRS seasons along the lower Yellow River were mainly determined by the water level and incoming sediment coefficient in the river, whereas those in the pre-WSRS season were mainly determined by the water level and suspended sediment concentration. Regarding the changes in groundwater level between the mid- and post-WSRS seasons, we found that suspended sediment concentration was the dominant factor in the pre-dam period, whereas the combined effect of water and sediment was the dominant factor in post-dam period. The response of the monthly groundwater level to changes in water and sediment characteristics lagged by 2–5 months. These results are essential to understanding the interaction between river water and groundwater.

Interacting water, nutrients, and shrub age control steppe grass‐on‐shrub competition: Implications for restoration

AbstractUnderstanding the factors that control grass–shrub interactions and coexistence is critical to the design of dryland management and restoration strategies. Using Stipa tenacissima tussocks as adult neighbor and Olea europaea var. sylvestris as target woody species, we performed a 5‐year‐long, large‐scale manipulative experiment to investigate the independent and combined effects of water and nutrient availability, and the modulating effects of O. europaea ontogeny on the net outcome of grass–shrub interaction. At two contrasting dryland sites, we conducted experimental plantings of Olea seedlings on two microsites: contiguous to a Stipa tussock (Stipa microsite) and on the intertussock bare‐soil areas (Open microsite), and manipulated resource availability by combining nutrient and water addition. The experiment followed a full factorial design, with all treatment combinations applied at each site. We monitored survival, height, and stem basal diameter of Olea individuals over a study period of 5 years. All across the wide range of conditions considered, negative effects of Stipa on Olea largely prevailed during the first 2 years after the plantation. We found that competition was stronger in the drier steppe, where extra inputs of water favored neutral interactions. Conversely, nutrient addition increased competition strength, particularly when combined with water inputs, pointing to the contrasting role of different resources and the importance of interactions between them in the control of plant–plant interaction outcome. The competition effects of Stipa faded with time and gradually shifted to neutral interaction as Olea individuals aged. Our results are particularly relevant to guide restoration efforts in formerly wooded xeric grasslands and rangelands.

Thermally Enhanced Water Weakening of the Solnhofen Limestone

AbstractWe report the strength and deformation behavior of Solnhofen limestone across its brittle (localized) to ductile (distributed) transition. We conducted conventional triaxial compression tests on water‐saturated and nominally dry cores of Solnhofen at temperatures up to 200°C and effective confining pressures up to 350 MPa to evaluate the roles of pore water and temperature on the deformation mechanisms of low‐porosity limestone at conditions of the upper crust. The combined effects of water and temperature on deformation and strength of the limestone are complex and reflect the concurrent operation of microfracturing, which is enhanced by both pore water and temperature, crystal plasticity, which is enhanced by temperature but not pore water, and likely also dissolution which is enhanced by water but inhibited by temperature. At ambient temperature, water causes a small reduction in the yield strength and the strength in the ductile field, but has no measurable effect of the brittle peak strength or the effective pressure of the brittle to ductile transition. At elevated temperatures, water‐saturated Solnhofen exhibits weakening in both the brittle and ductile fields up to 200 MPa effective pressure. In addition, the combined effects of pore water and temperature reduce the pressure of the brittle to ductile transition dramatically. We propose that under dry conditions temperature reduces the pressure of the brittle to ductile transition by enhancing crystal plasticity and under water‐saturated conditions enhanced microcracking is responsible. At effective pressures greater than 200 MPa, ductile deformation becomes temperature strengthening indicating the onset of dissolution mediated deformation.

Sources of Nitrogen in Combination with Systems of Irrigation Influence the Productivity of Modern Rice (Oryza sativa L.) Cultivars during Dry Season in Sub-Tropical Environment

In irrigated agricultural systems, nitrogen (N) and water are the vital resources for sustainability of the crop production in the modern era of climate change. The current study aimed to assess the impact of water and N management on the productivity of irrigated rice cultivars. In the context, a field observation was done at the research farm of Bangladesh Agricultural University, Mymensingh, during dry seasons in consecutive two years (2018–2019 and 2019–2020). The experiments were set up following split-plot design assigning water management in the main plots, nitrogen management in the sub-plots, and the cultivars were approved in the split-split plot with three replications. After two years observation, it was revealed that rice cultivar Binadhan-8 gave the maximum value of leaf area index, number effective tillers hill-1 and grains panicle-1 which lead to the higher grain yield (GY). Substantial relationships were observed among the concentration of N, growth, total dry matter (TDM) and N content, N uptake, N utilization effectiveness, and GY. However, with little exception, the Combined effect of water and N, cultivars and water management were varied significantly for all parameters. Finally, the results of the current study concluded that application of irrigation at 8 days after the disappearance of ponded water and source of 105 kg N ha-1 from PU + Poultry manure are the best management approach for the excellent performance of rice cultivar Binadhan-8.

Estimating and partitioning maize evapotranspiration as affected by salinity using weighing lysimeters and the SIMDualKc model

Water scarcity and saline stress are primary threats for water use and agricultural production in arid and semi-arid regions, such as the Hetao Irrigation District, China. The current study, using irrigation with saline water, developed through three seasons (2017–2019) of field experimental surveillance of mulched maize water use in two cropped weighing lysimeters. Measurements included crop characteristics (height, LAI, dates of development stages), soil and water salinity, and daily actual crop evapotranspiration (ETc act). Deficit surface irrigation was scheduled in 2017 and 2018 seasons, while in 2019 drip irrigation was used aimed at satisfying crop water requirements. Both approaches aimed at improving irrigation management while controlling impacts of salinity. The collected information was used to parameterize and calibrate the soil water balance model SIMDualKc. The model uses the FAO56 dual crop coefficient approach and considers the combined effect of water and salinity stresses due to salinity of both soil and irrigation water. Results show that the SIMDualKc model adequately simulates the dynamics of the observed ETc act throughout the three growing seasons. The goodness-of-fit indicators show highly appropriate model fitting of observed ETc act with low RMSE of 0.42 mm d-1 for the calibration and 0.53 mm d-1 for validation. The calibrated standard basal crop coefficients (Kcb) of maize for the initial, mid, and end stages were respectively 0.15, 1.15 and 0.25, which agree with those recently proposed by Pereira et al. (2021). Due to the impacts of both water and salt stress in 2017 and 2018, ETc act was much below the potential value ETc, ranging 64–83%, while in 2019 that percentage increased to 92% due to avoiding water stress by then. The average Kcb mid act range 0.58–1.06, therefore lower than Kcb mid, with the lower values occuring in the lysimeter that was irrigated with a large deficit. The irrigation scheduling practiced was assessed using water use and productivity indicators, which have shown the advantage in using drip irrigation with small time intervals between irrigations. Moreover, the current study and the calibrated model provide for adopting irrigation management practices that may save water and control salinity.

Can smart nutrient applications optimize the plant's hidden half to improve drought resistance?

Global agriculture is challenged with achieving sustainable food security while the climate changes and the threat of drought increases. Much of the research attention has focused on above-ground plant responses with an aim to improve drought resistance. The hidden half, that is, the root system belowground, is receiving increasing attention as the interface of the plant with the soil. Because roots are a sensing organ for nutrients and moisture, we speculate that crop root system traits can be managed using smart nutrient application in order to increase drought resistance. Roots are known to be influenced both by their underlying genetics and also by responses to the environment, termed root plasticity. Though very little is known about the combined effect of water and nutrients on root plasticity, we explore the possibilities of root system manipulation by nutrient application. We compare the effects of different water or nutrient levels on root plasticity and its genetic regulation, with a focus on how this may affect drought resistance. We propose four primary mechanisms through which smart nutrient management can optimize root traits for drought resistance: (1) overall plant vigor, (2) increased root allocation, (3) influence specific root traits, and (4) use smart placement and timing to encourage deep rooting. In the longer term, we envision that beneficial root traits, including plasticity, could be bred into efficient varieties and combined with advanced precision management of water and nutrients to achieve agricultural sustainability.

Experiment of Ship Maneuvering Motion in Muddy Navigation Area

In order to make full use of natural resources and ensure the safety of the ship navigation, based on the self-designed ship trajectory tracking system, the self-propelled model test of ship maneuverability which include cycle test and zig-zag test under the combined effects of water and fluid mud was completed in the test pool. And then based on the results of the tests, the influences of under-keel clearance on ship resistance, heading stability and turning radius were analyzed, and the maneuverability of the ship’s navigation in the fluid mud was comprehensively evaluated. The results show that as the under-keel clearance decreases, the linear stability of the ship increases, but its maneuverability deteriorates. In order to ensure safety, the depth of ship dragging into the fluid mud must be less than 10% of ship’s draft.

Mixed Cropping as Affected by Phosphorus and Water Supply

In a future exposed to threats of climate change, sustainable biomass production will be crucial. Maize (Zea mays) and sorghum (Sorghum sp.) are important crops for human and animal nutrition, as well as for bioenergy. The aim of this study was to investigate maize and sorghum in mixed cropping with soybean (Glycine max) and faba bean (Vicia faba) regarding biomass yield, drought tolerance, phosphorus (P) availability, and enzyme activity in soil as affected by the single and combined effects of water and P supply in two outdoor pot trials with rainout shelters. Maize had the highest biomass under sufficient water supply (80% water holding capacity, WHC), but a sharp decrease of its biomass of about 60% was measured when water was limited (30% WHC). In the mixtures, drought induced reduction of biomass was less than 40%. For mixed cropping usually higher contents of labile P fractions in soil than for sole cropped monocots were found. This was especially true for the combined stress of water and P deficit and can be partly explained by a higher activity of the acid phosphatase in the soil of the mixtures. A higher yield stability of the crop mixtures makes them a suitable agronomic alternative to sole cropped maize or sorghum under suboptimal conditions of water and P shortage.

Additive effects of temperature and water availability on pregnancy in a viviparous lizard.

One of the greatest current threats to biodiversity is climate change. However, understanding of organismal responses to fluctuations in temperature and water availability is currently lacking, especially during fundamental life-history stages such as reproduction. To further explore how temperature and water availability impact maternal physiology and reproductive output, we used the viviparous form of the European common lizard (Zootoca vivipara) in a two-by-two factorial design manipulating both hydric and thermal conditions, for the first time. We collected blood samples and morphological measurements during early pregnancy and post-parturition to investigate how water availability, temperature and a combination of the two influence maternal phenology, morphology, physiology and reproductive output. We observed that dehydration during gestation negatively affects maternal physiological condition (lower mass gain, higher tail reserve mobilization) but has little effect on reproductive output. These effects are mainly additive to temperature regimes, with a proportional increase in maternal costs in warmer environments. Our study demonstrates the importance of considering combined effects of water and temperature when investigating organismal responses to climate changes, especially during periods crucial for species survival such as reproduction.

Effects of water application uniformity using a center pivot on winter wheat yield, water and nitrogen use efficiency in the North China Plain

In recent years, the use of fertigation technology with center pivot irrigation systems has increased rapidly in the North China Plain (NCP). The combined effects of water and nitrogen application uniformity on the grain yield, water use efficiency (WUE) and nitrogen use efficiency (NUE) have become a research hotspot. In this study, a two-year field experiment was conducted during the winter wheat growing season in 2016–2018 to evaluate the water application uniformity of a center pivot with two low pressure sprinklers (the R3000 sprinklers were installed in the first span, the corresponding treatment was RS; the D3000 sprinklers were installed in the second span, the corresponding treatment was DS) and a P85A impact sprinkler as the end gun (the corresponding treatment was EG), and to analyze its effects on grain yield, WUE and NUE. The results showed that the water application uniformity coefficients of R3000, D3000 and P85A along the radial direction of the pivot (CUH) were 87.5, 79.5 and 65%, respectively. While the uniformity coefficients along the traveling direction of the pivot (CUC) were all higher than 85%. The effects of water application uniformity of the R3000 and D3000 sprinklers on grain yield were not significant (P>0.05); however, the average grain yield of EG was significantly lower (P<0.05) than those of RS and DS, by 9.4 and 11.1% during two growing seasons, respectively. The coefficients of variation (CV) of the grain yield had a negative correlation with the uniformity coefficient. The CV of WUE was more strongly affected by the water application uniformity, compared with the WUE value, among the three treatments. The NUE of RS was higher than those of DS and EG by about 6.1 and 4.8%, respectively, but there were no significant differences in NUE among the three treatments during the two growing seasons. Although the CUH of the D3000 sprinklers was lower than that of the R3000, it had only limited effects on the grain yield, WUE and NUE. However, the cost of D3000 sprinklers is lower than that of R3000 sprinklers. Therefore, the D3000 sprinklers are recommended for winter wheat irrigation and fertigation in the NCP.

Substantial and sustained reduction in under-5 mortality, diarrhea, and pneumonia in Oshikhandass, Pakistan: evidence from two longitudinal cohort studies 15 years apart

BackgroundOshikhandass is a rural village in northern Pakistan where a 1989–1991 verbal autopsy study showed that diarrhea and pneumonia were the top causes of under-5 mortality. Intensive surveillance, active community health education and child health interventions were delivered in 1989–1996; here we assess improvements in under-5 mortality, diarrhea, and pneumonia over this period and 15 years later.MethodsTwo prospective open-cohort studies in Oshikhandass from 1989 to 1996 (Study 1) and 2011–2014 (Study 2) enrolled all children under age 60 months. Study staff trained using WHO guidelines, conducted weekly household surveillance and promoted knowledge on causes and management of diarrhea and pneumonia. Information about household characteristics and socioeconomic status was collected. Hurdle models were constructed to examine putative risk factors for diarrhea and pneumonia.ResultsAgainst a backdrop of considerable change in the socioeconomic status of the community, under-5 mortality, which declined over the course of Study 1 (from 114.3 to 79.5 deaths/1000 live births (LB) between 1989 and 1996), exceeded Sustainable Development Goal 3 by Study 2 (19.8 deaths/ 1000 LB). Reductions in diarrhea prevalence (20.3 to 2.2 days/ Child Year [CY]), incidence (2.1 to 0.5 episodes/ CY), and number of bloody diarrhea episodes (18.6 to 5.2%) seen during Study 1, were sustained in Study 2. Pneumonia incidence was 0.5 episodes /CY in Study 1 and 0.2/CY in Study 2; only 5% of episodes were categorized as severe or very severe in both studies. While no individual factors predicted a statistically significant difference in diarrhea or pneumonia episodes, the combined effect of water, toilet and housing materials was associated with a significant decrease in diarrhea; higher household income was the most protective factor for pneumonia in Study 1.ConclusionsWe report a 4-fold decrease in overall childhood mortality, and a 2-fold decrease in childhood morbidity from diarrhea and pneumonia in a remote rural village in Pakistan between 1989 and 2014. We conclude that significant, sustainable improvements in child health may be achieved through improved socioeconomic status and promoting interactions between locally engaged health workers and the community, but that continued efforts are needed to improve health worker training, supervision, and the rational use of medications.Trial registrationNot Applicable.

Long term ageing of polyamide 6 and polyamide 6 reinforced with 30% of glass fibers: temperature effect

Because the prediction of the durability of polyamide materials is a very important issue for designers and users, the effect of environment conditions on their mechanical properties is an active field of research. For this reason this experimental investigation was conducted in order to study the effect of temperature on long term ageing of polyamide 6 (PA6) and polyamide 6 reinforced with 30 wt% of glass fibers (PA6GF30). Ageing was realized in distilled water (pH ≈ 6; 100% RH) at 30 °C, 50 °C, 70 °C and 90 °C for up to 80 days. Results highlighted the impact of ageing temperature on both conditioned materials. Thus, several surface damages such as crazing and yellowness were recorded especially at high temperatures indicating the materials degradation. These structure changes were induced by the combined effects of water and temperature. As the water diffuses within the polymer, the glass transition temperature Tg drops progressively with ageing temperature to reach the lowest value for samples aged at 90 °C for both tested materials. This tendency was also observed for Young’s modulus, tensile strength and the elongation at break. Thus, a significant loss in stiffness and strength of both materials was recorded as a function of conditioning temperature. This loss of mechanical properties is mainly caused by hydrolysis process and/or interfacial debonding. The appearance of this irreversible phenomenon rises with ageing temperature. Moreover, contrarily to PA6GF30, the temperature effect was also pointed out on SEM observations of PA6 samples. Thus, the hygrothermal ageing induces a change in the mode of fracture from ductile to moderate brittle one according to the ageing temperature. Accordingly, it seems that the ageing temperature has a great effect on the severity of damage of tested materials after long term immersion.

Combined effect of water and sustained compressive loading on chloride penetration into concrete

This paper presents the results of an experimental investigation on the water and chloride transport properties of unsaturated concrete under combined short-term sustained compressive loading and chloride attack. Aiming for the coupled effect of sustained compressive loading and chloride penetration, an improved test apparatus, which is compared with the traditional gravimetric measurement, was designed to real-timely and continuously measure the amount of water solution absorbed by the cylindrical hollow concrete specimen under sustained loading. A series of chloride transport experiments on water/chloride diffusivity and penetration profiles of chloride were conducted on the saturated, half-saturated and fully dried concrete respectively subjected to several compressive stress levels (ranging in 0–50% of the corresponding compression loading capacity). The experimental results showed that the saturation level and sustained compressive loadings have significant influences on water and chloride transport properties of the unsaturated concrete. The quantitative relationship between water/chloride diffusivity and compressive stress level was developed by fitting the obtained experimental data. Finally, on the basis of convection-diffusion equation, the prediction model of chloride transport in unsaturated concrete under sustained compressive loading was proposed and validated by the experimental results. The comparison of chloride profiles indicates that the numerical results were in good agreement with the experimental measurements.

Biotic interactions modify multiple-stressor effects on juvenile brown trout in an experimental stream food web.

Agricultural land use results in multiple stressors affecting stream ecosystems. Flow reduction due to water abstraction, elevated levels of nutrients and chemical contaminants are common agricultural stressors worldwide. Concurrently, stream ecosystems are also increasingly affected by climate change. Interactions among multiple co-occurring stressors result in biological responses that cannot be predicted from single-stressor effects (i.e. synergisms and antagonisms). At the ecosystem level, multiple-stressor effects can be further modified by biotic interactions (e.g. trophic interactions). We conducted a field experiment using 128 flow-through stream mesocosms to examine the individual and combined effects of water abstraction, nutrient enrichment and elevated levels of the nitrification inhibitor dicyandiamide (DCD) on survival, condition and gut content of juvenile brown trout and on benthic abundance of their invertebrate prey. Flow velocity reduction decreased fish survival (-12% compared to controls) and condition (-8% compared to initial condition), whereas effects of nutrient and DCD additions and interactions among these stressors were not significant. Negative effects of flow velocity reduction on fish survival and condition were consistent with effects on fish gut content (-25% compared to controls) and abundance of dominant invertebrate prey (-30% compared to controls), suggesting a negative metabolic balance driving fish mortality and condition decline, which was confirmed by structural equationmodelling. Fish mortality under reduced flow velocity increased as maximal daily water temperatures approached the upper limit of their tolerance range, reflecting synergistic interactions between these stressors. Our study highlights the importance of indirect stressor effects such as those transferred through trophic interactions, which need to be considered when assessing and managing fish populations and stream food webs in multiple-stressor situations. However, in real streams, compensatory mechanisms and behavioural responses, as well as seasonal and spatial variation, may alter the intensity of stressor effects and the sensitivity of trout populations.

Corrosion rate of API 5L Gr. X60 multipurpose steel pipeline under combined effect of water and crude oil

Multipurpose pipeline is often seriously corroded during its service life, and the phenomenon is more prominent once the transportation medium is changed. Electrochemical polarization curves and impedance spectroscopy of the API 5L Gr. X60 steel pipeline’s corrosion process in sedimentary water with different ion types and their concentrations have been studied in this work. The results showed that the corrosion rates were found to be 0.00418 and 0.00232 mm/a for pure water and crude oil, respectively. However, for the mixtures of water and crude oil (with water content increased from 0.2 vol% to 10 vol%), the corrosion rate increased consistently and reached a maximum value of 0.15557 mm/a for 10 vol% water in crude oil. The effect of the concentration of various ions, namely, chloride, bicarbonate and sulfate in (oil/water) mixtures on the corrosion rate was characterized by weight-loss method. The results showed that with increasing the ions’ concentrations, the corresponding exchange current density increased significantly. The results were further supported by the observations of corrosion morphology using scanning electron microscopy and are helpful in devising guidelines which would help in reducing corrosion in multipurpose transport pipelines involving a change of transported medium during their service life.

Corrosion Failure Analysis of a New L360 Pipeline

In this paper, the optical microscope, scanning electron microscope (SEM), X-ray Diffraction (XRD) and simulation test were utilized to study the corrosion failure of L360 pipeline. The results show that the corrosion pits distributed around the pipe inner surface. The pipe mechanical properties, chemical constituents and inclusions grade satisfied the requirements of the technical conditions. Inclusions were composed of Ca, S, Al and O. Corrosion products consisted of the Fe3O4, Fe2O3 and FeO (OH). The compositions of corrosion products within and around the pits were similar to the inclusions. Due to the combined effects of water and high pressure air sealed in the pipeline, the pits formed around inclusions, and developed into occluded cells which accelerating the corrosion and leading to the failure finally.