Ratio Of Precipitation Research Articles

Comprehensive assessment of aquaculture potential of the southern and south-eastern waterbodies in the Rostov region

The paper presents materials on a comprehensive assessment of reservoirs for commercial aquaculture, exemplified by some waterbodies in the Rostov region. We have examined 24 waterbodies located in the southern and south-eastern Rostov region. The assessment of reservoirs was carried out based on hydrological and hydrochemical indicators, the point score of which was carried out in four sets of issues. Almost all the studied water bodies because of the lack of required water supply have been classified as reservoirs with risky fish farming. Most aquaculture reservoirs recommended for commercial farming are found in the zone of a very arid climate, characterized by annual precipitation ratio of 0.33-0.44. A brief hydrochemical description of each investigated waterbody can be used to form scientifically-based recommendations for the organization of commercial fish farms in Russia.

Subauroral Green STEVE Arcs: Evidence for Low‐Energy Excitation

AbstractSubauroral emissions known as STEVEs (Strong Thermal Emission Velocity Enhancements) are sometimes accompanied by green arcs containing magnetic field‐aligned “picket fence” structures. In a newly published spectrum of a green picket fence arc Gillies et al. (2019, https://doi.org/10.1029/2019GL083272) showed that the visible emission in such arcs is mostly OI 557.7 nm with minimal N2+ 1N. This finding is consistent with the color ratios found in digital camera photos (Mende & Turner, 2019, https://doi.org/10.1029/2019JA026851) and is distinct from the ratios in auroral precipitation. The spectrum also contains intense N2 first positive (1P) emission. The presence of OI 557.7 (~4.19 eV excitation energy) and N2 1P (~7.35 eV), combined with the lack of N2+ first negative (~18.75 eV) commonly seen in the aurora, suggests that the particles exciting the emission have energy <18.75 eV. This is strong evidence against the precipitation hypothesis recently put forth (Nishimura et al., 2019, https://doi.org/10.1029/2019GL082460; Gillies et al., 2019, https://doi.org/10.1029/2019GL083272).

Contrasting drought impacts on the start of phenological growing season in Northern China during 1982–2015

AbstractDrought is a widely occurring extreme climatic event that may have various effects on vegetation phenology and activity. The change of the start of the phenological growing season (SOS) is one key mechanism for ecosystem responses to droughts yet remain unknown at large scale. This study used abnormal changes in the ratio of reference evapotranspiration (ETO) and precipitation (P) to detect the pre‐season (defined as the 3 months before the growing season) monthly drought during 1982–2015. After that, the pre‐season drought impacts on SOS were analysed. Drought appeared frequently (>3.6 times/10 years) in the northern and southwest China, as well as the coastal area of south China during the last 34 years. The droughts generally accompany a higher temperature and a stronger radiation, but the drought effects on the SOS differ between humid/sub‐humid and semi‐arid zones in northern China. Specifically, in the temperate humid/sub‐humid zones, SOS under drought was 1.08–4.86 days earlier than during normal (no drought) years, and the response was greater to the droughts that appeared in the first two of the three pre‐season months. In addition, in the cold, mid‐, and warm temperate zones, the advance response was more concentrated in the SOS about DOY130‐140, DOY125‐150, and DOY80‐160, respectively. However, in the north semi‐arid zone, the SOS under drought was 0.66–3.45 days later than during normal years, and the response was greater to the droughts that appeared in the last two of the 3 months. These delay responses also concentrated in the SOS about DOY125‐150. The contrasting drought impacts on phenology suggest that we should move beyond the vegetation activity under droughts such as the growth, productivity, and mortality, and pay more attention to the timing of vegetation activity to better quantify the carbon budget at Northern Hemisphere.

Tailoring Strength and Ductility of a Cr-Containing High Carbon Steel by Cold-Working and Annealing.

SEM, TEM characterizations, in combination with tensile tests, provided an intriguing observation that ultra-high-strength and good ductility could be achieved simultaneously by changing the ratio of large and small precipitates in high-carbon steel (1.0C-1.5Cr-0.31Mn-0.20Si, wt %). The high yield strength of 670 MPa, tensile-stress of 740 MPa, and good ductility (elongation of 26%) were obtained by adopting spheroidization annealing, cold rolling, recrystallization annealing, and cold drawing. This led to nanosized precipitates with a large ratio of big size to the small size of 0.28, promoting high dislocation storage of 1.39 × 1014 m−2. In addition, the finite element (FE) method was used to simulate the cold-rolling process, and the largest stress and strain were 830 MPa and 0.6 at a depth of 3 mm after the fourth pass of the 0.10C-1.50Cr steel, respectively. The stress and strain accumulation in the top layer was potentially caused by severe plastic deformation, as well as attrition rendered by the rollers. This explained the emergence of dense low-angle grain boundaries in the region close to the surface of the cold rolled steel.

Climate variability, disasters and their impacts assessment in Manahari, rural municipality of Makwanpur, Nepal

Nepal is climatically very sensitive country because of long drought, heavy floods, landslides and soil erosion caused by changing pattern of rainfall and temperature. However, there are very limited studies related to these issues, thus this research was objectively carried out to analyze temperature and precipitation trend of study area, examine the climate pattern and assess the impacts of climate change hazards on different sectors. Ward number 7 and 8 Manahari Rural Municipality of Makwanpur district was selected as the study site. Total 40 households survey, 15 Key informants interview and two focus group discussions were conducted involving the affected local to collect the primary data. Moreover, secondary data specifically monthly maximum and minimum temperature and rainfall for thirty one years between 1985–2015 were gathered from nearest meteorological station i.e. NFI Hetauda Station (Station No. 906) and Manahari Station (Station No. 920). The drought trend was calculated using the ratio of Precipitation<2Temperatures. The theoretical distribution i.e. Gumbel, Log-Pearson and Log Normal models were applied to predict the flood peaks and maximum rainfalls. The mean annual temperature was increasing at the rate of 0.0226°C per year. The highest mean annual temperature was 24.1°C in 2015. It was found that, the number of days exceeding the maximum average temperature in the period of 31 years. However, the trend of total annual precipitation in Hetauda was decreasing at the rate of 5.6607 mm per year. The highest rainfall was recorded about 3323.1 mm in year 2002 and it was the least only 1626.2 mm in 2012. The January, February, March, November and December were the driest months. Flood frequency using Log Pearson showed the highest flood in 1000 years return period. The mean rank was the highest of drought having value 5 while it was the lowest only 1.4 of flood. The slope failure at the edges of the rural roads also causes landslides which also fills the agriculture land. The locals responded that the drainage systems were poor and there were no protection structure and/or biological component to reduce landslide risk during construction periods. Major five disasters were recorded in Manahari during from March to June whereas, wildlife attack throughout the year and so on.

A substantial rise in the area and population affected by dryness in South Asia under 1.5 °C, 2.0 °C and 2.5 °C warmer worlds

Millions of people in South Asia face water scarcity every year. Previous studies based on the multi-model ensemble mean reported a decline in dryness (the ratio of potential evapotranspiration and precipitation) in South Asia under the warming climate. However, using observations and simulations from skilful climate models (BEST-GCMs) that simulate the critical monsoon features and show less bias to simulate observed climate, we show that dryness has significantly increased over the Gangetic Plain and parts of Pakistan during 1951–2016. Moreover, a rise in global mean temperature of 1.5 °C from the pre-industrial level will result in an increased dryness over half of South Asia affecting more than 790(±336) million people. Population affected by dryness is projected to 890 (±485) and 1960 (±1033) million under 2.0° and 2.5° warming worlds, respectively. Previously reported reduced aridity under the warming climate based on multi-model ensemble is mainly due to the GCMs that have less skill to simulate monsoon features. The GCMs with less skill project a higher increase (∼25%) in the monsoon season precipitation, which is largely due to their higher sensitivity of convective precipitation to warming. We show that the risk of water scarcity and dryness in South Asia under warming climate is higher than previously reported.

Complexation separation for vanadium and chromium by dithiocarbamate and its application in treatment of chromium–vanadium-bearing slag

Abstract A novel method for the separation and reclamation of vanadium and chromium from acidic solution was proposed. The principle for the separation is based on selective complexation. In specific, V(V) can be complexated by dithiocarbamate to form VO(R1R2NCS2)3 precipitate, leaving Cr(III) remained in the acidic solution. Then the reclamation of V and Cr from VO(R1R2NCS2)3 precipitate and Cr(III)-bearing solution can be reached by decomplexation and neutralization, respectively. The kinetics of the complexation reaction was studied. In addition, the precipitation ratio of vanadium reached 97% and the loss of chromium was less than 4% after process optimization. The complexing agent could be regenerated with a high ratio of 99.5%. The method was successfully applied to treating chromium–vanadium-bearing slag produced in conventional vanadium production industry. Vanadium and chromium could be extracted from the slag in the form of calcium vanadate and Cr2O3 product with a purity of over 98%.

Shift in plankton diversity and structure: Influence of runoff composition in the Nagqu River on the Qinghai-Tibet Plateau

Abstract Understanding the response of runoff composition in the Qinghai-Tibet Plateau (QTP) is essential for the ecology and environment. However, precise measurements of runoff composition in the QTP, especially in remote areas with limited climatic records, are a challenge. In rivers and lakes, some plankton is highly sensitive to changes in runoff composition. Here, we demonstrated how plankton indicators could be used as an indicator of runoff composition in the QTP. The stable isotopes of runoff, precipitation, groundwater and snowmelt in 9 sampling sites were studies of the Nagqu River in the QTP. The multi-source mass balance model (IsoSource model) was used to calculate the range of runoff composition at each sampling site. We found that the change of plankton biodiversity was associated to the runoff composition, and groundwater ratio was negatively correlated with biodiversity, while precipitation ratio was positively correlated with biodiversity, but not with snowmelt. Therefore, plankton diversity is expected to be a simple indicator of runoff composition, which can be easily quantified in remote plateau areas.

Biomineralization of Monohydrocalcite Induced by the Halophile Halomonas Smyrnensis WMS-3

The halophilic bacterium Halomonas smyrnensis from a modern salt lake used in experiments to induce biomineralization has resulted in the precipitation of monohydrocalcite and other carbonate minerals. In this study, a Halomonas smyrnensis WMS-3 (GenBank:MH425323) strain was identified based on 16S rDNA homology comparison, and then cultured in mediums with 3% NaCl concentration to induce monohydrocalcite at different Mg/Ca molar ratios of 0, 2, 5, 7, and 9. The growth curve of WMS-3 bacteria, pH values, NH4+ concentration, HCO3− and CO32− concentration, carbonic anhydrase (CA) activity, and the changes in Ca2+ and Mg2+ ion concentration were determined to further explore the extracellular biomineralization mechanism. Moreover, the nucleation mechanism of monohydrocalcite on extracellular polymeric substances (EPS) was analyzed through studying ultrathin slices of the WMS-3 strain by High resolution transmission electron microscopy (HRTEM), Selected area election diffraction (SAED), Scanning transmission electron microscopy (STEM), and elemental mapping, besides this, amino acids in the EPS were also analyzed. The results show that pH increased to about 9.0 under the influence of ammonia and CA activity. The precipitation ratio (%, the ratio of the mass/volume concentration) of the Ca2+ ion was 64.32%, 62.20%, 60.22%, 59.57%, and 54.42% at Mg/Ca molar ratios of 0, 2, 5, 7, and 9, respectively, on the 21st day of the experiments, and 6.69%, 7.10%, 7.74%, 8.09% for the Mg2+ ion concentration at Mg/Ca molar ratios 2, 5, 7, and 9, respectively. The obtained minerals were calcite, Mg-rich calcite, aragonite, and hydromagnesite, in addition to the monohydrocalcite, as identified by X-ray diffraction (XRD) analyses. Monohydrocalcite had higher crystallinity when the Mg/Ca ratio increased from 7 to 9; thus, the stability of monohydrocalcite increased, also proven by the thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC) analyses. The C=O and C–O–C organic functional groups present in/on the minerals analyzed by Fourier transform infrared spectroscopy (FTIR), the various morphologies and the existence of P and S determined by scanning electron microscope-energy dispersive spectrometer (SEM-EDS), the relatively more negative stable carbon isotope values (−16.91‰ to −17.91‰) analyzed by a carbon isotope laser spectrometer, plus the typical surface chemistry by XPS, all support the biogenesis of these mineral precipitates. Moreover, Ca2+ ions were able to enter the bacterial cell to induce intracellular biomineralization. This study is useful to understand the mechanism of biomineralization further and may provide theoretical reference concerning the formation of monohydrocalcite in nature.

Changes in humus carbon fractions in paddy soil given different organic amendments and mineral fertilizers

The effects of 4 years of combined application of mineral fertilizer with a variety of organic materials on soil humus carbon fractions were evaluated in a low-fertility paddy soil. Five treatments were selected: (1) no fertilizer, (2) mineral fertilizer alone, (3) mineral fertilizer plus green manure at 3.6 Mg ha−1, (4) mineral fertilizer plus cattle manure at 4.7 Mg ha−1, and (5) mineral fertilizer plus rice straw at 3.0 Mg ha−1. The following properties were determined: water soluble substance carbon, water floating substance carbon, humic acid carbon, fulvic acid carbon, total alkali-extractable humic carbon, and humin carbon. The ratio of humic acid carbon / fulvic acid carbon and precipitation ratio (the percentage of humic acid in the sum of humic acid and fulvic acid) were calculated. The results indicated that application of mineral fertilizer with organic amendments respectively increased the concentrations of humic acid carbon and total alkali-extractable humic carbon by 18.3 − 31% and 11.7 − 21.3% in 0 − 5 cm, humin carbon by 14.9 − 22.5% in 5 − 10 cm, compared to mineral fertilizer alone. However, no differences in fulvic acid carbon concentration were recorded among the fertilization treatments in 0 − 5 cm. Furthermore, organic inputs exhibited minor influences on humus carbon fractions (−4.2 − 22% and 2.8 − 8% for humic acid carbon; −0.6 − 13% and 1.6 − 4.4% for total alkali-extractable humic carbon; 0.3 − 9.5% and −0.4 − 4.4% for humin carbon; −0.7 − 5.3% and 0.4 − 1.3% for fulvic acid carbon) in 10 − 20 cm and 20 − 30 cm, respectively. Among the three organic amendments, surface placement of cattle manure resulted in the highest concentrations of water soluble substance carbon (0.26 g kg−1, 0.22 g kg−1, and 0.21 g kg−1), humic acid carbon (4.6 g kg−1, 3.2 g kg−1, and 2.1 g kg−1), total alkali-extractable humic carbon (7.1 g kg−1, 5.6 g kg−1, and 4.2 g kg−1), and humin carbon (11.4 g kg−1, 11 g kg−1, and 7.8 g kg−1) in upper soil layer (0 − 5 cm, 5 − 10 cm, and 10 − 20 cm). In addition, the precipitation ratio value tended to be significantly higher (23.2% in 0 − 5 cm, 24.6% in 5 − 10 cm, and 16.5% in 10 − 20 cm, P < 0.05) in mineral fertilizer with cattle manure additions than mineral fertilizer alone. There were significant correlations between rice grain yield and total soil organic carbon (R2 = 0.72, n = 15, P < 0.01), humic acid carbon (R2 = 0.79, n = 15, P < 0.001), and humin carbon (R2 = 0.59, n = 15, P < 0.05) in the 0−5 cm soil depth. In summary, our results showed that combined application of mineral fertilizer with cattle manure was the most effective management practice to increase humus carbon pool, which could be regarded as a useful indicator of the carbon sequestration process in paddy soil.

Co2+ anchored on surface-functionalized PET non-woven fabric and used as high efficiency monoatom-like catalyst for activating Oxone in water

Fenton-like processes have emerged as most promising techniques for generating reactive oxygen-containing radicals to deal with increasing levels of environmental pollution. Developing novel catalysts with simple manufacturing requirements, excellent activity levels, and stability remains a long-term goal in terms of practical application. So herein, a new polyethylene terephthalate (PET) non-woven fabric based composite catalyst has been fabricated, using radiation-induced graft polymerization of a functionalized group to chelate Co2+ ions as heterogeneous catalysts in peroxymonosulfate (Oxone) activation. Several impact factors, including catalyst dosage, Oxone concentration, reaction temperature, pH value, Co2+ precipitation ratio (of Co@PET at different pH values), and highly concentrated NaCl have been investigated here. Notably, Co@PET has shown the lowest activation energy of any reported catalyst, for degrading RhB by activating Oxone. Interestingly, as experimental RhB and Oxone solutions were passed through single Co@PET sheets, the RhB was decomposed into a colorless solution in the penetration process. Based on radical trapping and quenching experiments, a channel was determined to dominate RhB degradation, and furthermore, Co@PET could be re-used for RhB degradation by activating Oxone. These results showed that Co@PET effectively provided improved Fenton-like catalytic performance and stability, and was suitable for practical applications.

Global sinusoidal seasonality in precipitation isotopes

Abstract. Quantifying seasonal variations in precipitation δ2H and δ18O is important for many stable isotope applications, including inferring plant water sources and streamflow ages. Our objective is to develop a data product that concisely quantifies the seasonality of stable isotope ratios in precipitation. We fit sine curves defined by amplitude, phase, and offset parameters to quantify annual precipitation isotope cycles at 653 meteorological stations on all seven continents. At most of these stations, including in tropical and subtropical regions, sine curves can represent the seasonal cycles in precipitation isotopes. Additionally, the amplitude, phase, and offset parameters of these sine curves correlate with site climatic and geographic characteristics. Multiple linear regression models based on these site characteristics capture most of the global variation in precipitation isotope amplitudes and offsets; while phase values were not well predicted by regression models globally, they were captured by zonal (0–30∘ and 30–90∘) regressions, which were then used to produce global maps. These global maps of sinusoidal seasonality in precipitation isotopes based on regression models were adjusted for the residual spatial variations that were not captured by the regression models. The resulting mean prediction errors were 0.49 ‰ for δ18O amplitude, 0.73 ‰ for δ18O offset (and 4.0 ‰ and 7.4 ‰ for δ2H amplitude and offset), 8 d for phase values at latitudes outside of 30∘, and 20 d for phase values at latitudes inside of 30∘. We make the gridded global maps of precipitation δ2H and δ18O seasonality publicly available. We also make tabulated site data and fitted sine curve parameters available to support the development of regionally calibrated models, which will often be more accurate than our global model for regionally specific studies.

Tree ring dating using oxygen isotopes: a master chronology for central England

ABSTRACTRing‐width dendrochronology, based on matching patterns of ring width variability, works best when trees are growing under significant environmental (climatic) stress. In the UK, and elsewhere in the temperate mid‐latitudes, trees generally experience low stress, so dating is more difficult and often fails. Oxygen isotopes in tree rings passively record changes in the isotopic ratios of summer precipitation, so they carry a strong common signal, which offers potential for cross‐dating. A master chronology covering the period 1200–2000 ce was constructed using the oxygen isotope ratios of the latewood cellulose of oak samples from central England. Two independent chronologies, developed to verify the isotopic signal, were combined (n = 10 trees) and the method was evaluated by dating timbers of known age and historical timbers that could not be dated by ring‐width dendrochronology, from both within and beyond the central England region. The agreement between samples and the master chronology is exceptionally strong, allowing the dating of timbers with far fewer rings than is normally the case for ring‐width dendrochronology. Tree‐ring oxygen isotope values are more suited to correlation analysis than tree‐ring widths, so it is possible to provide t‐values that conform to Student's t‐distribution and can be converted into probabilities of error. A protocol for assigning dates using ‘stable‐isotope dendrochronology’ is proposed, which has the potential to revolutionize the dating of wooden structures and artefacts, allowing the dating of short and invariant ring sequences from young, fast‐grown trees. Such samples are commonplace throughout the historical building and archaeological records and were, until now, considered impossible to date. © 2019 The Authors. Journal of Quaternary Science Published by John Wiley &amp; Sons Ltd

Spatial variation in oak (Quercus spp.) radial growth responses to drought stress in eastern North America

Dendroecology provides a means to evaluate how mature trees have responded to climate stresses in the recent past and provides one approach for projecting how existing forests will respond to future climate change. This study documented spatial variation in the strength of growth–climate associations for six oak (Quercus) species at 284 sites in eastern North America that span substantial gradients of temperature and site water balance. Radial growth of oaks was more strongly related to growing-season precipitation and the ratio of precipitation to potential evapotranspiration at sites in the western part of the study region where drought conditions occur more frequently. Growth was more strongly related to growing-season mean maximum temperature in the warmer, southern part of the study region. Growth of oaks was not strongly related to site water balance or temperature in the northeastern part of the study region. These results indicate that if climate change results in increased growing-season drought stress, this will adversely affect mature oak trees growing in the southern and western parts of eastern North America, but oaks growing in northeastern North America have more safe space for change before they will suffer reduced growth and vigor.

The Role of Hydrological Initial Conditions on Atmospheric River Floods in the Russian River Basin

Abstract A body of work over the last decade or so has demonstrated that most major floods along the U.S. West Coast are attributable to atmospheric rivers (ARs). Recent studies suggest that observed changes in extreme precipitation associated with a general warming of the western United States have not necessarily led to corresponding changes in floods, and changes in antecedent hydrological conditions could be a primary missing link. Here we examine the role of antecedent soil moisture (ASM) conditions on historical AR flooding on California’s Russian River basin, a coastal watershed whose winter precipitation extremes are dominated by ARs. We examined the effect of observed warming on ASM for the period 1950–2017. We first constructed an hourly precipitation product at 1/32° spatial resolution. We used the Distributed Hydrology Soil Vegetation Model (DHSVM) to estimate storm total runoff volumes and soil moisture. We found that up to 95% of peaks-over-threshold (POT) extreme discharge events were associated with ARs. The storm runoff–precipitation ratio generally increased with wetter prestorm conditions, and the relationship was stronger as drainage area increased. We found no trends in extreme precipitation but weak downward trends in extreme discharge. The latter were mostly consistent with weak downward trends in the first 2-day storm precipitation. We found no trends in ASM; however, ASM was significantly correlated with peak flow. The ASM was affected more by antecedent precipitation than evapotranspiration, and hence temperature increases had weak effects on ASM.

Biased estimates of the isotope ratios of steady‐state evaporation from the assumption of equilibrium between vapour and precipitation

AbstractStable water isotope ratios are measured as a tracer of environmental processes in materials such as leaves, soils, and lakes. Water in these archives may experience evaporation, which increases the abundance of heavy isotopologues proportionally to the gradients in humidity and isotope ratio between the evaporating water and the surrounding atmosphere. The isotope ratio of the atmosphere has been difficult to measure until recently, and measurements remain scarce. As a result, several assumptions have been adopted to estimate isotope ratios of atmospheric water vapour. Perhaps the most commonly employed assumption in terrestrial environments is that water vapour is in isotopic equilibrium with precipitation. We evaluate this assumption using an eight‐member ensemble of general circulation model (GCM) simulations that include explicit calculation of isotope ratios in precipitation and vapour. We find that across the model ensemble, water vapour is typically less depleted in heavy isotopologues than expected if it were in equilibrium with annual precipitation. Atmospheric vapour likely possesses higher‐than‐expected isotope ratios because precipitation isotope ratios are determined by atmospheric conditions that favour condensation, which do not reflect atmospheric mixing and advection processes outside of precipitation events. The effect of this deviation on theoretical estimates of isotope ratios of evaporating waters scales with relative humidity. As a result, the equilibrium assumption gives relatively accurate estimates of the isotope ratios of evaporating waters in low latitudes but performs increasingly poorly at increasing latitudes. Future studies of evaporative water pools should include measurements of atmospheric isotope ratios or constrain potential bias with isotope‐enabled GCM simulations.

Measurement of Spatial Variation of Rainfall in Cuddalore District using Ilwis

Rainfall is a one of the important phenomena of the hydrological cycle; its distribution time to time, varies from one place to another place; and it acts as a source of water to the earth. Indian agriculture and the cropping pattern, with good yield of production, depend on the rainfall during monsoon. According to the IMD, South peninsular region got 40% of rainfall from South-West monsoon and 60% from North-East monsoon. This study aims at understanding the spatial distribution of rainfall and its influences in the hydrological trend of precipitation over the area which is closely linked with flood and drought. For the purpose of evaluation, the rainfall data of 21 stations were collected from statistical department and PWD Ground water division of Cuddalore district during period of 1986 – 2016. After error correction and checking, the general methodology was applied for this study. The collected data and the real time data were matched for the mathematical analysis to find the Mean, Seasonal variation, Coefficient of Variation, Precipitation Ratio. The spatial distribution of rainfall convert as the non spatial data of an attribuutive information in the form of statistics, tabled list, graphs and finally, using the ILWIS software, to find the influence of rainfall over the area were identified and demarcated with maps. The long term rainfall analysis identifies the influence and pattern of spatial distribution of Cuddalore district.

Aridity change and its correlation with greening over drylands

A drying trend and an expansion of drylands through history, as well as an expectation to continue under the future climate, have been inferred by recent studies. However, this seems to conflict with observed greenness over drylands. In this study, the changes in aridity over drylands from 1982 to 2011 were examined using the aridity index (ratio of precipitation and potential evapotranspiration), precipitation minus actual evapotranspiration, and soil moisture derived from a combination of observation and modelling. In addition, corresponding changes in vegetative greenness and their relationships with aridity changes were explored. The results show that above three indicators all point to a little change in aridity of drylands over the past three decades, and their trends in spatial patterns agree well each other. Simultaneously, significant greening (p < 0.05) occurred in more than 36% of vegetated drylands, in contrast to the 7% with significant browning (p < 0.05). Drylands as a whole, vegetative greenness demonstrated a significant positive relationship (p < 0.05) with precipitation change. At the biome scale, significant relationships (p < 0.05) were observed for vegetative greenness and precipitation for all other vegetation types except forests, suggesting that the increasing precipitation was one of the main drivers of greening over drylands. In addition, the largest increase of greening was observed for croplands, implying a strong impact from agricultural activities particularly irrigation practices. Results from this study provide clues for understanding the greening of drylands and are also crucial for the understanding of environmental changes in the context of climate change.

Separation and recovery of lithium from Li3PO4 leaching liquor using solvent extraction with saponified D2EHPA

There is a dramatically increasing demand for lithium calls, which requires processing all viable resources. A solution with low Li+ concentration is often generated during the production process of lithium and its compounds. Recovery of these resources via Li3PO4 precipitation is a promising method, but there are few effective methods for the subsequent processing of the Li3PO4. In this work, a novel method for treating lithium phosphate is proposed. After dissolving Li3PO4 with acid, a high concentration of Li and P existed in the form of cations and anions respectively in the solution. The saponified di-2-ethylhexyl phosphoric acid (D2EHPA)-kerosene system was used to separate the Li and P. The Li was effectively extracted, while P remained in the raffinate. The extraction was a process of cation-exchange between Li+ and Na+. Under the optimized conditions, the concentrations of Li and entrained P in the stripping solution were 18.1 g/L and 0.08 g/L. The mass ratio of P/Li of the stripping solution was reduced to 0.0044 (336 times lower compared to the feed solution P/Li ratio of 1.48). The stripping solution was precipitated with sodium carbonate, and the Li2CO3 precipitation ratio reached 90% at 80 °C under the CO32–/Li+ molar ratio of 1.23:2. The final product of lithium carbonate was in accordance with the standard specification (Li2CO3-0, GB/T 11075-2013). The results of this study provide an efficient process for recovering low-concentration lithium resources.

Preparation of Sodium Pyroantimonate from Antimony Trioxide by Pressure Oxidation in NaOH Solution

A technical route for preparing sodium pyroantimonate by pressure oxidation in NaOH solution is proposed. The E-pH diagram of the Sb-H2O system shows that Sb(III) from antimony trioxide can be oxidized to Sb(V) to prepare sodium pyroantimonate under different alkaline concentrations. In the direct pressure oxidation technique, the product was doped with antimony trioxide due to the diffusion effect. By comparison, the technique of complex leaching-pressure oxidation could prepare an eligible product, which presented regular hexahedral morphology. Nevertheless, sodium pyroantimonate transformed to NaSbO3 at excessive temperature. The sodium antimonite solution prepared in the leaching process contained 18 g/L Sb. The antimony precipitation ratio in the pressure oxidation process increased with the stirring speed and oxygen partial pressure. Under the optimum conditions of temperature of 150°C, oxygen partial pressure of 2.0 MPa, stirring speed of 1000 rpm, and reaction time of 2 h, the antimony precipitation ratio was 97.70%.