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1. chinaXiv:202107.00021 [pdf]

Assessment of organic compost and biochar in promoting phytoremediation of crude-oil contaminated soil using Calendula officinalis in the Loess Plateau, China

WANG Jincheng; JING Mingbo; ZHANG Wei; ZHANG Gaosen; ZHANG Binglin; LIU Guangxiu; CHEN Tuo; ZHAO Zhiguang
Subjects: Geosciences >> Geography

The Loess Plateau, located in Gansu Province, is an important energy base in China because most of the oil and gas resources are distributed in Gansu Province. In the last 40 a, ecological environment in this region has been extremely destroyed due to the over-exploitation of crude-oil resources. Remediation of crude-oil contaminated soil in this area remains to be a challenging task. In this study, in order to elucidate the effects of organic compost and biochar on phytoremediation of crude-oil contaminated soil (20 g/kg) by Calendula officinalis, we designed five treatments, i.e., natural attenuation (CK), planted C. officinalis only (P), planted C. officinalis with biochar amendment (PB), planted C. officinalis with organic compost amendment (PC), and planted C. officinalis with co-amendment of biochar and organic compost (PBC). After 152 d of cultivation, total petroleum hydrocarbons (TPH) removal rates of CK, P, PB, PC and PBC were 6.36%, 50.08%, 39.58%, 73.10% and 59.87%, respectively. Shoot and root dry weights of C. officinalis significantly increased by 172.31% and 80.96% under PC and 311.61% and 145.43% under PBC, respectively as compared with P (P<0.05). Total chlorophyll contents in leaves of C. officinalis under P, PC and PBC significantly increased by 77.36%, 125.50% and 79.80%, respectively (P<0.05) as compared with PB. Physical-chemical characteristics and enzymatic activity of soil in different treatments were also assessed. The highest total N, total P, available N, available P and SOM (soil organic matter) occurred in PC, followed by PBC (P<0.05). C. officinalis rhizospheric soil dehydrogenase (DHA) and polyphenol oxidase (PPO) activities in PB were lower than those of other treatments (P<0.05). The values of ACE (abundance-based coverage estimators) and Chao 1 indices for rhizospheric bacteria were the highest under PC followed by PBC, P, PB and CK (P<0.05). However, the Shannon index for bacteria was the highest under PC and PBC, followed by P, PB and CK (P<0.05). In terms of soil microbial community composition, Proteiniphilum, Immundisolibacteraceae and Solimonadaceae were relatively more abundant under PC and PBC. Relative abundances of Pseudallescheria, Ochroconis, Fusarium, Sarocladium, Podospora, Apodus, Pyrenochaetopsis and Schizothecium under PC and PBC were higher, while relative abundances of Gliomastix, Aspergillus and Alternaria were lower under PC and PBC. As per the nonmetric multidimensional scaling (NMDS) analysis, application of organic compost significantly promoted soil N and P contents, shoot length, root vitality, chlorophyll ratio, total chlorophyll, abundance and diversity of rhizospheric soil microbial community in C. officinalis. A high pH value and lower soil N and P contents induced by biochar, altered C. officinalis rhizospheric soil microbial community composition, which might have restrained its phytoremediation efficiency. The results suggest that organic compost-assisted C. officinalis phytoremediation for crude-oil contaminated soil was highly effective in the Loess Plateau, China.

submitted time 2021-07-23 From cooperative journals:《Journal of Arid Land》 Hits93Downloads41 Comment 0

2. chinaXiv:202107.00022 [pdf]

Large scale sand saltation over hard surface: a controlled experiment in still air

LIU Benli; WANG Zhaoyun; NIU Baicheng; QU Jianjun
Subjects: Geosciences >> Geography

Saltation is the major particle movement type in wind erosion process. Saltating sand grains can rebound up to tens of times larger in length and height over hard surface (such as gravel surface) than over loose sand surface. Gravels usually have different faces, causing distinct response of the impacting grains, but the effects of the grain and gravel-surface contact angle on grain rebound are not yet well quantified. We performed full-range controlled experiments of grain saltation using different contact angles, grain sizes and impact speeds in still air, to show that contact angle increases the height of representative saltation path but decreases particle travel length. The results were compared with outputs from the COMprehensive numerical model of SALTation (COMSALT). Large saltation height of 4.8 m and length of 9.0 m were recorded. The maximum and representative saltation height over the gravel surface were found to be about 4.9 times and 12.8 times those over the loose sandy surface, respectively. The maximum saltation length may be reduced by 58% and the representative saltation height may be increased by 77% as contact angle increases from 20° to 40°. We further showed that the collision inertia contributes 60% of the saltation length, and wind contributes to the other 40%. These quantitative findings have important implications for modeling saltation trajectory over gravel surface.

submitted time 2021-07-23 From cooperative journals:《Journal of Arid Land》 Hits116Downloads58 Comment 0

3. chinaXiv:202107.00025 [pdf]

Adaptability of machine learning methods and hydrological models to discharge simulations in data-sparse glaciated watersheds

JI Huiping; CHEN Yaning; FANG Gonghuan; LI Zhi; DUAN Weili; ZHANG Qifei
Subjects: Geosciences >> Geography

The accurate simulation and prediction of runoff in alpine glaciated watersheds is of increasing importance for the comprehensive management and utilization of water resources. In this study, long short-term memory (LSTM), a state-of-the-art artificial neural network algorithm, is applied to simulate the daily discharge of two data-sparse glaciated watersheds in the Tianshan Mountains in Central Asia. Two other classic machine learning methods, namely extreme gradient boosting (XGBoost) and support vector regression (SVR), along with a distributed hydrological model (Soil and Water Assessment Tool (SWAT) and an extended SWAT model (SWAT_Glacier) are also employed for comparison. This paper aims to provide an efficient and reliable method for simulating discharge in glaciated alpine regions that have insufficient observed meteorological data. The two typical basins in this study are the main tributaries (the Kumaric and Toxkan rivers) of the Aksu River in the south Tianshan Mountains, which are dominated by snow and glacier meltwater and precipitation. Our comparative analysis indicates that simulations from the LSTM shows the best agreement with the observations. The performance metrics Nash-Sutcliffe efficiency coefficient (NS) and correlation coefficient (R2) of LSTM are higher than 0.90 in both the training and testing periods in the Kumaric River Basin, and NS and R2 are also higher than 0.70 in the Toxkan River Basin. Compared to classic machine learning algorithms, LSTM shows significant advantages over most evaluating indices. XGBoost also has high NS value in the training period, but is prone to overfitting the discharge. Compared with the widely used hydrological models, LSTM has advantages in predicting accuracy, despite having fewer data inputs. Moreover, LSTM only requires meteorological data rather than physical characteristics of underlying data. As an extension of SWAT, the SWAT_Glacier model shows good adaptability in discharge simulation, outperforming the original SWAT model, but at the cost of increasing the complexity of the model. Compared with the oftentimes complex semi-distributed physical hydrological models, the LSTM method not only eliminates the tedious calibration process of hydrological parameters, but also significantly reduces the calculation time and costs. Overall, LSTM shows immense promise in dealing with scarce meteorological data in glaciated catchments.

submitted time 2021-07-23 From cooperative journals:《Journal of Arid Land》 Hits107Downloads54 Comment 0

4. chinaXiv:201907.00003 [pdf]

Sub-parallel ridge-trench interaction and an alternative model for the Silurian-Devonian archipelago in Western Junggar and North-Central Tianshan in NW China

Zhang, Ji'en; Chen, Yichao; Xiao, Wenjiao; Wakabayashi, John; Windley, Brian F.; Yin, Jiyuan
Subjects: Geosciences >> Geology

Plate boundary evolution and interpreted paleogeography commonly involve the interaction between oceanic ridges and trenches. Western Junggar and Central-North Tianshan, NW China, have previously been regarded as independent orogens, but this model was challenged by the discovery of their similar tropic-subtropic coral assemblages and of Precambrian and Early Paleozoic clasts transmitted from the Central Tianshan in Early to Middle Paleozoic sediments in SW Junggar, suggesting they had been in contact by then. The presence of Late Silurian-Early Devonian adakitic rocks in northern SW Junggar was explained by slab roll-back, which required an active subducting slab in SW Junggar. However, this model is inconsistent with the cessation of arc magmatism immediately after the adakitic magmatism indicating there was no subduction in SW Junggar at those times. By re-evaluating the relevance of four diagnostic features of modern Californian ridge subduction, we propose a new model to explain the Late Silurian-Early Devonian orogenic framework of NW China in terms of sub-parallel ridge-trench interaction. The transmitted clasts from Central Tianshan in Early Paleozoic sediments in SW Junggar, at the same time as the Late Ordovician and Middle Silurian coral assemblages, and the complementary accretionary complex in SW Junggar and magmatic arc in Central Tianshan, are all contributary evidence for an Early Paleozoic subduction system. This subduction zone was intruded by two 446-380 Ma double magmatic belts: 1. A ridge subduction-generated adakitic gabbro-basalt-andesite-diorite-granite-rhyolite suite that intruded a 504-446 Ma accretionary complex in SW Junggar, and 2. a magmatic arc in Central Tianshan. A buoyant subducting ridge rifted and separated these magmatic belts resulting in the opening of a new 414-325 Ma ocean, which is preserved in OIB- and MORB-type ophiolites in SW Junggar and North Tianshan. These geological and geochemical relationships resemble those generated by oceanic spreading in the modern Gulf of California, which led to separation of magmatic belts in Baja California and mainland Mexico. The new ocean split the Central Tianshan magmatic arc from the Early Paleozoic Mt. Xiemisitai-Barleik-Mayile accretionary complex in SW Junggar, which changed to a new passive continental margin that led to deposition of Devonian shallow marine-terrestrial sediments, and to cessation of magmatism at 379-349 Ma. These features, including the Middle Paleozoic orogenic architecture and the geochemical properties of specific magmatic rocks, indicate the development of a Late Silurian-Early Devonian sub-parallel-to-trench ridge subduction. This model not only interprets phenomena mentioned in the above earlier models, but also reconciles unresolved spatial relationships between Western Junggar and the Tianshan. Subsequent closure of the new ocean and subduction of its ridge in the Late Paleozoic gave rise to the archipelagic framework that we see today in NW China. An analysis of worldwide examples of sub-parallel ridge-trench interaction demonstrates that a ridge can undergo multiple episodes of subduction before a terminal ocean closure. In this context our new tectonic model for the western Junggar and Tianshan regions may provide an improved understanding of the structure and evolution of ridge-subduction events in ancient orogenic belts.

submitted time 2021-06-22 Hits7079Downloads1213 Comment 0

5. chinaXiv:202106.00103 [pdf]

A juvenile skull of the longirostrine choristodere (Diapsida:Choristodera), Mengshanosaurus minimus gen. et sp. nov.,with comments on neochoristodere ontogeny

YUAN Meng; LI Da-Qing; Daniel T. KSEPKA; YI Hong-Yu
Subjects: Biology >> Zoology

Choristoderes were an important clade of semi-aquatic predators that occupied Laurasian freshwater ecosystems from the Middle Jurassic to the Miocene. During the Early Cretaceous, the neochoristodere lineage evolved large size and long snouts, converging on the body plan of modern crocodilians. Here, we describe a new longirostrine choristodere, Mengshanosaurus minimus gen. et sp. nov. from the Lower Cretaceous Mengyin Formation of Shandong Province, China. The holotype is the smallest reported neochoristodere individual, with a skull length of only 35 mm. The poorly ossified braincase, along with retention of a fontanel at the frontal-parietal suture, indicates this individual was a juvenile. Phylogenetic analyses recovered Mengshanosaurus as a neochoristodere, a placement supported by the presence of a single narial opening, fusion of the nasals, and expansion of the temporal fenestrae. In the Neochoristodera, Mengshanosaurus is sister to a clade consisting of Ikechosaurus, Tchoiria, Simoedosaurus, and Champsosaurus. It differs from other neochoristoderes in having the lacrimal foramen between the prefrontal and lacrimal, in addition to having large vomerine teeth (exceeding one-third the width of corresponding maxillary teeth). The closely arranged marginal teeth and large vomerine teeth suggest juvenile choristoderes may have fed on invertebrates and insects, similar to juveniles of modern crocodilians. However, the observation that very young neochoristoderes had similar skull proportions and marginal tooth shapes to adults, along with features suggesting a more fully aquatic ecology, suggest that neochoristoderes exhibited less pronounced ontogenetic niche shifts than modern crocodilians.

submitted time 2021-06-21 From cooperative journals:《古脊椎动物学报》 Hits3044Downloads227 Comment 0

6. chinaXiv:202106.00010 [pdf]

Potential responses of vegetation to atmospheric aerosols in arid and semi-arid regions of Asia

JIAO Linlin; WANG Xunming; CAI Diwen; HUA Ting
Subjects: Geosciences >> Geography

Changes in atmospheric aerosols have profound effects on ecosystem productivity, vegetation growth and activity by directly and indirectly influencing climate and environment conditions. However, few studies have focused on the effects of atmospheric aerosols on vegetation growth and activity in the vulnerable arid and semi-arid regions, which are also the source areas of aerosols. Using the datasets of aerosol optical depth (AOD), normalized difference vegetation index (NDVI) and multiple climatic variables including photosynthetically active radiation (PAR), surface solar radiation (SSR), surface air temperature (TEM) and total precipitation (PRE), we analyzed the potential responses of vegetation activity to atmospheric aerosols and their associated climatic factors in arid and semi-arid regions of Asia from 2005 to 2015. Our results suggested that areas with decreasing growing-season NDVI were mainly observed in regions with relatively sparse vegetation coverage, while AOD tended to increase as NDVI decreased in these regions. Upon further analysis, we found that aerosols might exert a negative influence on vegetation activity by reducing SSR, PAR and TEM, as well as suppressing PRE in most arid and semi-arid regions of Asia. Moreover, the responses of atmospheric aerosols on vegetation activity varied among different growing stages. At the early growing stage, higher concentration of aerosol was accompanied with suppressed vegetation growth by enhancing cooling effects and reducing SSR and PAR. At the middle growing stage, aerosols tended to alter microphysical properties of clouds with suppressed PRE, thereby restricting vegetation growth. At the late growing stage, aerosols exerted significantly positive influences on vegetation activity by increasing SSR, PAR and TEM in regions with high anthropogenic aerosols. Overall, at different growing stages, aerosols could influence vegetation activity by changing different climatic factors including SSR, PAR, TEM and PRE in arid and semi-arid regions of Asia. This study not only clarifies the impacts of aerosols on vegetation activity in source areas, but also explains the roles of aerosols in climate.

submitted time 2021-06-04 From cooperative journals:《Journal of Arid Land》 Hits5261Downloads574 Comment 0

7. chinaXiv:202106.00015 [pdf]

Spatiotemporal analysis of drought variability based on the standardized precipitation evapotranspiration index in the Koshi River Basin, Nepal

Nirmal M DAHAL; XIONG Donghong; Nilhari NEUPANE; Belayneh YIGEZ; ZHANG Baojun; YUAN Yong; Saroj KOIRALA; LIU Lin; FANG Yiping
Subjects: Geosciences >> Geography

Drought is an inevitable condition with negative impacts in the agricultural and climatic sectors, especially in developing countries. This study attempts to examine the spatial and temporal characteristics of drought and its trends in the Koshi River Basin (KRB) in Nepal, using the standardized precipitation evapotranspiration index (SPEI) over the period from 1987 to 2017. The Mann-Kendall test was used to explore the trends of the SPEI values. The study illustrated the increasing annual and seasonal drought trends in the KRB over the study period. Spatially, the hill region of the KRB showed substantial increasing drought trends at the annual and seasonal scales, especially in summer and winter. The mountain region also showed a significant increasing drought trend in winter. The drought characteristic analysis indicated that the maximum duration, intensity, and severity of drought events were observed in the KRB after 2000. The Terai region presented the highest drought frequency and intensity, while the hill region presented the longest maximum drought duration. Moreover, the spatial extent of drought showed a significant increasing trend in the hill region at the monthly (drought station proportion of 7.6%/10a in August), seasonal (drought station proportion of 7.2%/10a in summer), and annual (drought station proportion of 6.7%/10a) scales. The findings of this study can assist local governments, planners, and project implementers in understanding drought and developing appropriate mitigation strategies to cope with its impacts.

submitted time 2021-06-04 From cooperative journals:《Journal of Arid Land》 Hits2615Downloads288 Comment 0

8. chinaXiv:202105.00010 [pdf]

Characteristics and hazards of different snow avalanche types in a continental snow climate region in the Central Tianshan Mountains

HAO Jiansheng; Richard MIND'JE; LIU Yang; HUANG Farong; ZHOU Hao; LI Lanhai
Subjects: Geosciences >> Geography

Snow avalanches are a common natural hazard in many countries with seasonally snow-covered mountains. The avalanche hazard varies with snow avalanche type in different snow climate regions and at different times. The ability to understand the characteristics of avalanche activity and hazards of different snow avalanche types is a prerequisite for improving avalanche disaster management in the mid-altitude region of the Central Tianshan Mountains. In this study, we collected data related to avalanche, snowpack, and meteorology during four snow seasons (from 2015 to 2019), and analysed the characteristics and hazards of different types of avalanches. The snow climate of the mid-altitude region of the Central Tianshan Mountains was examined using a snow climate classification scheme, and the results showed that the mountain range has a continental snow climate. To quantify the hazards of different types of avalanches and describe their situation over time in the continental snow climate region, this study used the avalanche hazard degree to assess the hazards of four types of avalanches, i.e., full-depth dry snow avalanches, full-depth wet snow avalanches, surface-layer dry snow avalanches, and surface-layer wet snow avalanches. The results indicated that surface-layer dry snow avalanches were characterized by large sizes and high release frequencies, which made them having the highest avalanche hazard degree in the Central Tianshan Mountains with a continental snow climate. The overall avalanche hazard showed a single peak pattern over time during the snow season, and the greatest hazard occurred in the second half of February when the snowpack was deep and the temperature increased. This study can help the disaster and emergency management departments rationally arrange avalanche relief resources and develop avalanche prevention strategies.

submitted time 2021-04-30 From cooperative journals:《Journal of Arid Land》 Hits2279Downloads267 Comment 0

9. chinaXiv:202104.00093 [pdf]

Soil bacterial characteristics between surface and subsurface soils along a precipitation gradient in the Alxa Desert, China

TENG, Zeyu; XIAO, Shengchun; CHEN, Xiaohong; HAN, Chao
Subjects: Geosciences >> Geography

Bacteria in desert soil have unique phylogeny and important ecological functions, and their responses to changes in precipitation need further attention. However, relevant studies have mainly focused on the surface soil, and studies on the responses of bacteria at different soil depths to variations in precipitation are rare. Thus, we used 16S rDNA high-throughput sequencing to investigate the changes in soil bacterial distribution along a mean annual precipitation gradient (50–150 mm) in the Alxa Desert, China, and compared the variation characteristics in the surface soil layer (0–10 cm) and subsurface soil layer (10–20 cm). Results showed that soil bacterial communities significantly changed along the precipitation gradient in both soil layers. However, the subsurface soil layer could support bacterial communities with higher diversity and closer internal relationships but more internal competition than the surface soil layer. Additionally, compared with the surface soil layer, variations in diversity and co-occurrence patterns in the subsurface soil layer were more in line with the changes in the mean annual precipitation, while bacterial community structure was less variable in the subsurface soil layer. Compared with the mean annual precipitation, soil moisture had little influence on the structure and diversity of soil bacterial community but had a high correlation with intercommunity connectivity. Therefore, soil moisture might play a complex role in mediating environmental conditions and soil bacterial community characteristics. Due to the different responses of surface and subsurface soil bacteria to the changes in precipitation, it is necessary to distinguish different soil layers when predicting the trends in desert soil bacterial conditions associated with precipitation, and prediction of subsurface soil bacteria may be more accurate.

submitted time 2021-04-22 From cooperative journals:《Journal of Arid Land》 Hits2137Downloads240 Comment 0

10. chinaXiv:202104.00095 [pdf]

Glacier mass balance in High Mountain Asia inferred from a GRACE release-6 gravity solution for the period 2002–2016

XIANG, Longwei; WANG, Hansheng; JIANG, Liming; SHEN, Qiang; STEFFEN, Holger ; LI, Zhen
Subjects: Geosciences >> Geography

We provide estimates of glacier mass changes in the High Mountain Asia (HMA) area from April 2002 to August 2016 by employing a new version of gravity solutions of the Gravity Recovery and Climate Experiment (GRACE) twin-satellite mission. We found a total mass loss trend of the HMA glaciers at a rate of –22.17 (±1.96) Gt/a. The largest mass loss rates of –7.02 (±0.94) and –6.73 (±0.78) Gt/a are found for the glaciers in Nyainqentanglha Mountains and Eastern Himalayas, respectively. Although most glaciers in the HMA area show a mass loss, we find a small glacier mass gain of 1.19 (±0.55) and 0.77 (±0.37) Gt/a in Karakoram Mountains and West Kunlun Mountains, respectively. There is also a nearly zero mass balance in Pamirs. Our estimates of glacier mass change trends confirm previous results from the analysis of altimetry data of the ICESat (Ice, Cloud and Land Elevation) and ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) DEM (Digital Elevation Model) satellites in most of the selected glacier areas. However, they largely differ to previous GRACE-based studies which we attribute to our different post-processing techniques of the newer GRACE data. In addition, we explicitly show regional mass change features for both the interannual glacier mass changes and the 14-a averaged seasonal glacier mass changes. These changes can be explained in parts by total net precipitation (net snowfall and net rainfall) and net snowfall, but mostly by total net radiation energy when compared to data from the ERA5-Land meteorological reanalysis. Moreover, nearly all the non-trend interannual mass changes and most seasonal mass changes can be explained by the total net radiation energy data. The mass loss trends could be partly related to a heat effect due to increased net rainfall in Tianshan Mountains, Qilian Mountains, Nyainqentanglha Mountains and Eastern Himalayas. Our new results for the glacier mass change in this study could help improve the understanding of glacier variation in the HMA area and contribute to the study of global change. They could also serve the utilization of water resources there and in neighboring areas.

submitted time 2021-04-22 From cooperative journals:《Journal of Arid Land》 Hits1388Downloads302 Comment 0

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