Algal blooms have severe impacts on the utilization of water resources. The discovery of allelopathy provides a new dimension to solving this problem due to its high efficiency, safety and economy. ...Allelopathy can suppress the growth of microalgae by impairing the structure, photosynthesis and enzyme activity of algal cells. In the current work, we first demonstrate the allelopathy and allelochemicals derived from both plants and algae. We then expound the potential mechanisms of allelopathy on microalgae. Next, the potential application of allelochemicals in water environment is proposed. Finally, the key challenge and future perspective are presented.
The initial behavior of colloidal fouling is governed by foulant-clean-membrane interaction (F-M), and its long-term behavior is determined by foulant-fouled-membrane interaction (F-F). Nevertheless, ...the transitional fouling behavior from F-M to F-F has not been fully understood. This study reports a novel collision attachment (CA)-Monte Carlo (MC) approach, with the stochastic colloid-membrane collision events modeled by MC and the probability of colloidal attachment to the membrane determined by the interplay of flux and the energy barrier arising from colloid-membrane interaction (
for F-M and
for F-F). The long-term membrane flux remains stable for large
, whereas severe fouling occurs when both
and
are small. Our study reveals the existence of a metastable flux behavior for the combination of large
but small
. The time evolution of flux behavior and colloidal deposition patterns shows a nearly constant flux for an extended period, with the high energy barrier
retarding initial colloidal deposition. However, accidental random deposition of a colloidal particle could reduce the local energy barrier (toward the smaller
), seeding for further colloidal deposition in its vicinity. This initiates an uneven patch-wise fouling and eventually leads to a complete transition to F-F-dominated behavior. The metastable period can be effectively extended by increasing the energy barrier (
or
) or lowering flux, which provides important implications to membrane design and operation.
Allelopathy by hydrophytes can be utilized to control algal blooms. This study was conducted to investigate the allelopathic effect (inhibition) of
Scenedesmus quadricauda
on
Microcystis flos-aquae
. ...When
M. flos-aquae
was co-cultured with
S. quadricauda
, the secretion of high-MW biopolymer by
M. flos-aquae
was inhibited by
S. quadricauda
. We further identified the allelochemicals and found that 4-tert-butylpyrocatechol (TBC) was the main active ingredient that could inhibit the growth of
M. flos-aquae
. When the dose of TBC was larger than 0.2 mg/L, almost all of the
M. flos-aquae
died. Additionally, TBC was found to suppress the growth of
M. flos-aquae
by disturbing the synthesis and secretion of proteins and polysaccharides and harming the chlorophyll to affect the light harvesting of algal cells. Therefore, TBC has the potential for use as a potential and promising algaecide to restrain the biomass of
M. flos-aquae
.
This paper examines the relationship between environmental violations and the cost of corporate bonds, and further analyzes whether refinancing constraints, the lending restrictions on penalized ...firms, are an important channel through which environmental violations affect the cost of corporate debt financing in China. Using the manually collected environmental violation events from 2008 to 2020, we find that the bond cost of firms violating environmental regulations increases significantly after being penalized. The finding is robust to potential sample selection bias and endogeneity problems. Furthermore, we find that the effect of environmental violations on the cost of corporate bonds is more profound in short‐term debt‐dependent firms and can be alleviated by the internal financing dependence. These results confirm that the refinancing risk arising from China's green loan policy on pollution‐intensive firms plays a key role in the relation between environmental violations and the cost of capital in the firms. In the context of the growing concerns of global society about climate change, our findings have great implications for pollution‐intensive firms, bond investors, and regulatory authorities in emerging economies to manage the increasing environmental risk.
The seasonal evolution of sea ice mass balance between the Central Arctic and Fram Strait, as well as the underlying driving forces, remain largely unknown because of a lack of observations. In this ...study, two and three buoys were deployed in the Central Arctic during the summers of 2010 and 2012, respectively. It was established that basal ice growth commenced between mid‐October and early December. Annual basal ice growth, ranging from 0.21 to 1.14 m, was determined mainly by initial ice thickness, air temperature, and oceanic heat flux during winter. An analytic thermodynamic model indicated that climate warming reduces the winter growth rate of thin ice more than for thick ice because of the weak thermal inertia of the former. Oceanic heat flux during the freezing season was 2–4 W m−2, which accounted for 18–31% of the basal ice energy balance. We identified two mechanisms that modified the oceanic heat flux, i.e., solar energy absorbed by the upper ocean during summer, and interaction with warm waters south of Fram Strait; the latter resulted in basal ice melt, even in winter. In summer 2010, ice loss in the Central Arctic was considerable, which led to increased oceanic heat flux into winter and delayed ice growth. The Transpolar Drift Stream was relatively weak in summer 2013. This reduced sea ice advection out of the Arctic Ocean, and it restrained ice melt because of the cool atmospheric conditions, weakened albedo feedback, and relatively small oceanic heat flux in the north.
Key Points
Summer 2010 sea ice loss in the Central Arctic enhanced mixed‐layer warming, and consequently increasing oceanic heat flux and delaying ice growth
Cool atmospheric conditions in summer 2013, driven by the large‐scale circulation, reduced sea ice melt in the Central Arctic
Oceanic heat flux during the freezing season in the Arctic outflow region was 2–4 W m−2, accounting for 18–31% of basal ice energy balance
KEY MESSAGE : MLNAC5 functions as a stress-responsive NAC transcription factor gene and enhances drought and cold stress tolerance in transgenic Arabidopsis via the ABA-dependent signaling pathway. ...NAC transcription factors (TFs) play crucial roles in plant responses to abiotic stress. Miscanthus lutarioriparius is one of Miscanthus species native to East Asia. It has attracted much attention as a bioenergy crop because of its superior biomass productivity as well as wide adaptability to different environments. However, the functions of stress-related NAC TFs remain to be elucidated in M. lutarioriparius. In this study, a detailed functional characterization of MlNAC5 was carried out. MlNAC5 was a member of ATAF subfamily and it showed the highest sequence identity to ATAF1. Subcellular localization of MlNAC5-YFP fusion protein in tobacco leaves indicated that MlNAC5 is a nuclear protein. Transactivation assay in yeast cells demonstrated that MlNAC5 functions as a transcription activator and its activation domain is located in the C-terminus. Overexpression of MlNAC5 in Arabidopsis had impacts on plant development including dwarfism, leaf senescence, leaf morphology, and late flowering under normal growth conditions. Furthermore, MlNAC5 overexpression lines in Arabidopsis exhibited hypersensitivity to abscisic acid (ABA) and NaCl. Moreover, overexpression of MlNAC5 in Arabidopsis significantly enhanced drought and cold tolerance by transcriptionally regulating some stress-responsive marker genes. Collectively, our results indicated that MlNAC5 functions as an important regulator during the process of plant development and responses to salinity, drought and cold stresses.
Sea ice leads promote mass and energy exchange between the atmosphere and the Arctic Ocean. The continuous thinning of sea ice and the enhanced sea ice mobility in the past decades can potentially ...change the seasonal cycle and interannual variability of lead distribution in the Arctic, especially during spring. However, the long-term trend in Arctic leads, associated with sea ice loss, remains inconclusive. Sequential lead distribution data from serial middle- or high- resolution satellite observations are needed to obtain realistic variation, trends, and lead characteristics on a regional or basin scale. This study proposed a modified algorithm to retrieve daily spring leads in the Beaufort Sea using temperature anomaly from Terra/MODIS thermal imagery. Our lead map was compared to existing lead datasets and validated by Landsat-8 images, showing that the modified method gave better results in identification of open water leads and refrozen leads covered by thin ice. The development and interannual trend for April leads were explored for the study period 2001–2020. We found a positive interannual trend in the April lead area of about 2612 ± 1245 km2/year (90% confidence). Higher increasing rate was identified in the early April, which would be 26.4– 29.2% lower if the influence from cloud variation was removed. Lead area presents a close correlation with the 11-day average of ice drift speed before lead detection, while the influence of regional pressure gradient and easterly wind on the lead area is limited to the synoptic scale and recedes within a week. In the years with anomalous large lead area, we found the detected lead area are closely related to enhanced ice motion driven by strengthening Beaufort High and persistent easterly wind.
Display omitted
•Using only Terra/ MODIS images for daily leads to reduce effect of ice motion.•Trend of April leads in April for two decades was obtained regardless of cloud.•Rising trend in April leads fraction in the Beaufort Sea since 2001 is observed.•Anomalies in detected leads distribution are related to meteorological parameters.
Ice loads are major environmental loads that are encountered during navigation in the polar regions and can affect the structural safety of a ship, thereby leading to severe structural or fatigue ...damage to the ship structure. To identify full-scale ice loads, an ice load measurement on XueLong was performed during an Arctic voyage in August 2017. The least square support vector machine (LS_SVM) algorithm was utilised in the ice load identification model, and an experimental application was performed to validate the feasibility of the identification model. Two typical ship–ice interaction cases were analysed via time–procedure analysis. During the trials, 306 cases were analysed, and 16,178 extreme values of ice loads were extracted via the extreme selection procedure. Three commonly used fitting models—the Weibull, exponential, and lognormal models—were adopted for analysing the distribution of extreme values, and the Weibull distribution model was selected via a goodness-of-fit test. Considering the main parameters that influence ice loads, a grey relational analysis was performed to determine the input variables of the parametric model of extremes. The parametric statistics can aid in the development of an early warning system for detecting ice loads.
•A full scale ice load measurement was performed on the icebreaker XueLong.•A trial application of load identification is done to validate the proposed ice load identification model.•The analysis of fitting functions and goodness-of-fit test of extreme values of ice loads were performed.•A parametric statistics of extreme values of ice loads was established by the grey relation analysis.
Accurate and high-resolution sea ice surface temperature (IST) data is of great importance for Arctic climate studies. However, the validation of high-resolution IST data using in situ measurements ...in polar sea ice regions is lacking. This study assesses the accuracy of three split-window (SW) and two single-channel (SC) methods, based on Landsat 8 thermal infrared imagery at 100 m resolution over Arctic sea ice regions. The SW methods are proposed by Jin et al. (2015) (SW-Jin), Jiménez-Muñoz et al. (2014) (SW-JM), and Du et al. (2015) (SW-Du). The SC methods are proposed by Jiménez-Muñoz et al. (2014) (SC-JM) and Barsi et al. (2003, 2005) (SC-Barsi). IST data derived from 58 scenes of the Landsat 8 images were compared with coincident in situ ice skin temperatures and near-surface air temperatures, as measured by a combination of Ice Mass Balance (IMB) buoys, Snow and Ice Mass Balance Array (SIMBA) buoys, and automatic weather stations. SW-Du offers the best accuracy when compared with the skin temperature (bias: −1.06 K; root mean square error (RMSE): 2.08 K) and near-surface air temperature (bias: -0.98 K; RMSE: 2.17 K). SC-Barsi ranks second, with a bias of −1.55 K and RMSE of 2.40 K for the skin temperature. As for precision, IST from the Moderate Resolution Imaging Spectrometer (MODIS) has best performance (standard deviation (STD): 1.69 K), followed by SW-Du, SW-JM, and SC-Barsi (STD: 1.80 K, 1.82 K, and 1.85 K, respectively). The Landsat IST outperforms the MODIS IST in narrow lead areas, owing to its better spatial resolution, and SW-JM and SC-Barsi methods agree best with the MODIS IST in leads and marginal ice zone scenes, respectively. As all three SW methods are constrained by banding effects with different degrees in a lead scene, they are not recommended to be applied on an image scene with severe banding artifacts. The small bias (1.26 K) and high correlation (0.99) between skin temperature and near-surface air temperature prove the capability of using near-surface air temperature as a substitute for validating a satellite IST data if skin temperature data are not available.
•IST from Landsat 8/TIRS images is accurate enough for sea ice related use.•Split window algorithm has better accuracy than single channel method.•Fine resolution IST images can capture small details on sea ice regions.•Banding artifacts in TIRS images still contaminate IST maps.
Spaceborne interferometric synthetic aperture radar (InSAR) techniques are important for landslide detection and monitoring; however, several limitations and uncertainties, such as the unique ...north–south flying direction and side-look radar observing geometry, currently limit the ability of InSAR to credibly detect landslides, especially those related to high and steep slopes. Here, we conducted experimental and statistical analysis on the feasibility of time-series InSAR monitoring for steep slopes using ascending and descending SAR images. First, the theoretical (TGNSS), practical (PGNSS), and terrain (Hterrain) (T-P-H) indices for sensitivity evaluations of the slope displacement monitoring results from time-series InSAR were proposed for slope monitoring. Subsequently, two experimental and statistical studies were conducted for the cases with and without Global Navigation Satellite System (GNSS) monitoring data. Our experimental results of two high and steep open-pit mines showed that the defined theoretical and practical sensitivity indices can quantitatively evaluate the feasibility of ascending and descending InSAR observations in steep-slope deformation monitoring with GNSS data, and the terrain sensitivity index can qualitatively evaluate the feasibility of landslide monitoring results from ascending and descending Sentinel-1 satellite data without GNSS data. We further demonstrate the generalizability of these proposed indices using four landslide cases with both public GNSS and InSAR monitoring data and 119 landslide cases with only InSAR monitoring data. The statistical results indicated that greater indices correlated with higher reliability of the monitoring results, suggesting that these novel indices have wide suitability and applicability. This study can help to improve the practice of slope deformation monitoring using spaceborne InSAR, especially for high and steep slopes.
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