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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》 Hits831Downloads295 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》 Hits746Downloads306 Comment 0

3. 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》 Hits2351Downloads371 Comment 0

4. chinaXiv:202011.00126 [pdf]

Morphological characteristics and dynamic changes of seif dunes in the eastern margin of the Kumtagh Desert, China

PANG,Yingjun; WU,Bo; LI,Yonghua; XIE,Shengbo
Subjects: Geosciences >> Geography

The seif dune field over the gravel desert surface in the eastern margin of the Kumtagh Desert is a valuable experimental site for the observation of dune formation and dynamics. We used high-resolution remote sensing and station observation approaches, combined with wind and grain size data, to study the characteristics of the aeolian environment and the morphologies of and dynamic changes in seif dunes. We observed the ratio of the resultant drift potential (RDP) to the drift potential (DP), which was 0.37, associated with an obtuse bimodal wind regime. The drift potentials in the west-northwest (WNW) and east-northeast (ENE) directions were dominant, and the angle between the two primary DP directions was 135.00°. The dune orientations ranged from 168.75°–213.75°, which were parallel to the resultant drift direction (186.15°). The dune lengths ranged from 51.68 to 1932.11 m with a mean value of 344.91 m. The spacings of the dunes ranged from 32.34 to 319.77 m with a mean value of 93.39 m. The mean grain size of the sediments became finer, and the sorting became better from upwind tail to downwind tip, which indicated that the sediment of the seif dunes in the study region may be transported from northward to southward. The rate of increase in the length, the mean longitudinal migration rate of the dune tail, and the mean longitudinal extension rate of the dune tip (also called elongation rate) were 4.93, 4.63, and 9.55 m/a, respectively. The mean lateral migration vector of the seif dunes was approximately 0.11 m/a towards the west (–0.11 m/a), while the mean amplitude of lateral migration was 0.53 m/a, ignoring the direction of lateral migration. We found that the seif dune field formed first beside seasonal rivers, which can provide sediment, and then expanded downwind.

submitted time 2020-11-25 From cooperative journals:《Journal of Arid Land》 Hits3530Downloads798 Comment 0

5. chinaXiv:201809.00174 [pdf]

Characteristics of daily extreme wind gusts on the Qinghai-Tibet Plateau, China

YAO, Zhengyi; LI, Xiaoying; XIAO, Jianhua
Subjects: Geosciences >> History of Geosciences

Severe wind is a major natural hazard and a main driver of desertification on the Qinghai-Tibet Plateau. Generally, studies of Qinghai-Tibet Plateau's wind climatology focus on mean wind speeds and its gust speeds have been seldom investigated. Here, we used observed daily maximum gust speeds from a 95-station network over a 5-year period (2008–2012) to analyze the characteristics of extreme wind speeds and directions by fitting Weibull and Gumbel distributions. The results indicated the spatial distribution of extreme wind speeds and their direction on the Qinghai-Tibet Plateau is highly variable, with its western portion prone to greater mean speeds of extreme wind gusts than its eastern portion. Maximum extreme wind speeds of 30.9, 33.0, and 32.2 m/s were recorded at three stations along the Qinghai Tibet Railway. Severe winds occurred mostly from November to April, caused primarily by the westerly jet stream. Terrain greatly enhances the wind speeds. Our spatial analysis of wind speed data showed that the wind speeds increased exponentially with an increasing altitude. We also assessed the local wind hazard by calculating the return periods of maximum wind gusts from the observational data based on the statistical extreme value distributions of these wind speeds. Further attention should be given to those stations where the yearly maximum daily extreme wind speed increased at a rate greater than that of mean value of daily extreme wind speeds. Severe extreme wind events in these regions of the plateau are likely to become more frequent. Consequently, building structural designers working in these areas should use updated extreme wind data rather than relying on past data alone.

submitted time 2018-09-17 From cooperative journals:《Journal of Arid Land》 Hits1989Downloads855 Comment 0

6. chinaXiv:201711.00366 [pdf]

Wind tunnel test on the effect of metal net fences on sand flux in a Gobi Desert, China

WANG Tao; QU Jianjun; LING Yuquan; XIE Shengbo; XIAO Jianhua
Subjects: Geosciences >> Geography

The Lanzhou-Xinjiang High-speed Railway runs through an expansive windy area in a Gobi Desert, and sand-blocking fences were built to protect the railway from destruction by wind-blown sand.

submitted time 2017-11-07 From cooperative journals:《Journal of Arid Land》 Hits2409Downloads1210 Comment 0

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