A numerical model study on the spatial and temporal variabilities of dissolved oxygen in Qinzhou Bay of the northern Beibu Gulf

Oxygen facilitates the breakdown of the organic material to provide energy for life.The concentration of dissolved oxygen(DO) in the water must exceed a certain threshold to support the normal metabolism of marine organisms.Located in the northern B eibu Gulf,Qinzhou B ay receives abundant freshwater and nutrients from several rivers which significantly influence the level of the dissolved oxygen.However,the spatial-temporal variations of DO as well as the associated driving mechanisms have been rarely studied through field observations.In this study,a three-dimension al coupled physical-biogeochemical model is used to investigate the spatial and seasonal variations of the DO and the associated driving mechanisms in Qinzhou B ay.The validation against observations indicates that the model can capture the seasonal and inter-annual variability of the DO concentration with the range of 5-10 mg/L.Sensitivity experiments show that the river discharges,winds and tides play crucial roles in the seasonal variability of the DO by changing the vertical mixing and stratification of the water column and the circulation pattern.In winter,the tide and wind forces have strong effects on the DO distribution by enhancing the vertical mixing,especially near the bay mouth.In summer,the river discharges play a dominant role in the DO distribution by inhibiting the vertical water exchange and delivering more nutrients to the Bay,which increases the DO depletion and results in lower DO on the bottom of the estuary salt wedge.These findings can contribute to the preservation and management of the coastal environment in the northern Beibu Gulf.

Dramatic changes in the horizontal structure of mangrove forests in the largest delta of the northern Beibu Gulf, China

The horizontal structure of mangrove forests is an important characteristic that reflects a significant signal for coupling between mangroves and external drivers.While the loss and gain of mangroves has received much attention,little information about how the horizontal structure of mangrove forests develops from the seedling stage to maturity has been presented.Here,remote sensing images taken over approximately 15 years,UVA images,nutrient elements,sediments,and Aegiceras corniculatum vegetation parameters of the ecological quadrats along the Nanliu Delta,the largest delta of the northern Beibu Gulf in China,are analyzed to reveal changes in the horizontal structure of mangroves and their associated driving factors.The results show that both discrete structures and agglomerated structures can often be found in A.corniculatum seedlings and saplings.However,the combination of seedlings growing into maturity and new seedlings filling in available gaps causes the discrete structure of A.corniculatum to gradually vanish and the agglomerate structure to become stable.The aggregated structure of seedlings,compared to the discrete structure,can enhance the elevation beneath mangroves by trapping significantly more sediments,providing available spaces and conditions for seedlings to continue growing.Furthermore,by catching fine sediments with enriched nutrients,the survival rate of A.corniculatum seedlings in the agglomerated structure can be much higher than that in the discrete structure.Our results highlight the significance of the agglomeration of A.corniculatum,which can be beneficial to coastal mangrove restoration and management.

Dramatical hydro-sedimentary changes induced by bamboo fences over mangrove tidal flat of the largest delta in Beibu Gulf, southwestern China

Mangrove forest is one of the most important ecological and environmental resources by effectively promoting tidal flat deposition and preventing the coastal region from typhoon.However,there have been mass loss of mangrove forests due to anthropogenic activities.It is an urgent need to explore an effective way for mangrove restoration.Here,three rows of bamboo fences with hydro-sedimentary observation set over Aegiceras corniculatum mangrove tidal flat of the Nanliu Delta,the largest delta of Beibu Gulf,China,were conducted to analyze the hydro-sedimentary variations induced by bamboo fences.Results identified that the mean horizontal velocity Um per burst(20 min)decreased by as much as 71%and 40%in comparison with those without bamboo fences in March and November,respectively,when the tidal current entering the bamboo area during flood.The maximum of mean horizontal flow velocity Um-max at bamboo area was 50%–75%of that without bamboo fences during ebb tide.The suspended sediment concentration of bamboo area suggested a maximum reduction of 57%relative to bare flat during flood,and was 80%lower than bare flat at ebb peak.Moreover,the turbulent kinetic dissipationεat flood tide was significantly higher than that at ebb tide,while the bamboo fences greatly increased the turbulent kinetic dissipationεby 2 to 5 times relative to bare flat,resulting in an increase of the bed elevation by inhibiting the sediment incipient motion and intercepting suspended sediment.The siltation rate at the bamboo area was 140%and 29.3%higher than that at the bare flat and the region covered with A.corniculatum,respectively.These results highlight that bamboo fences can effectively attenuate tidal current and thus promote siltation over mangrove flat,which contribute great benefit to mangrove survival.

Spatiotemporal Distribution of Asian Horseshoe Crab Eggs Are Highly Intermingled with Anthropogenic Structures in Northern Beibu Gulf,China

Identification,protection and restoration of spawning habitats are vital for protecting the depleted species.Asian horseshoe crabs are ecologically important macroinvertebrates in coastal and estuarine ecosystems.However,their spawning habitat studies were limited to several reports in tropical regions,possibly due to the lack of modified survey methods,particularly in habitats with a lower density of spawning adults,and/or intermingled with anthropogenic structures.In this study,the year-round egg distribution and spawning habitat baselines of Carcinoscorpius rotundicauda and Tachypleus tridentatus were determined in the northern Beibu Gulf,China.Our findings demonstrated that the peak spawning occurred in June–July and ceased in November–January when the average water temperature dropped below 20℃.Egg aggregations were found<10 cm beneath the sediment surface with regular tidal inundation,regardless of seasonal changes,in the vicinity of natural and artificial structures with elevated,mildly sloping substratum within the high tide zones.The nests were characterized by medium-sized sediment grains(0.5–0.9 mm),high temperatures(31–34℃),low water contents(0.8%–0.9%),and total organic carbon contents(0.5%–0.7%),which might maximize the hatching success.The identified nesting beaches were close to nursery habitats for juveniles,and tidal creeks were present as the possible corridor connecting these two important habitats through the dominant mangrove forests.The findings provide valuable insights in the scope of spawning behavior and nest-site selection of Asian horseshoe crabs under a mixture of natural and artificial structures,which could benefit future management efforts for the exploited spawning populations.

Asian Horseshoe Crab Bycatch in Intertidal Zones of the Northern Beibu Gulf:Suggestions for Conservation Management

Bycatch poses a severe challenge to global fishery management.Although studies have focused on marine megafauna bycatch,research on relevant issues regarding invertebrates is limited,particularly for the threatened horseshoe crabs.In this study,the distribution of fishing gears and the bycatch intensity of Asian horseshoe crabs in the intertidal zones of the northern Beibu Gulf that harbors the most abundant juvenile Asian horseshoe crabs populations in China were evaluated.Seven intertidal nursery habitats for Tachypleus tridentatus and Carcinoscorpius rotundicauda were surveyed from May to July in 2021.A transect that crossed the tidal creeks and tidal flats between the high tide embankment/vegetation and low tide line of a given habitat was surveyed during the ebb tides.The type,number,and GPS of fishing gears were recorded when sighted,and the number and prosomal width of each horseshoe crab species were measured.Bycatch intensities differed among habitats,ranging from 0.3 to 18.4 and 1.2 to 22.7 individuals per kilometer of transect for T.tridentatus and C.rotundicauda,respectively.Among the three identified fishing gear types,ground cages and stick net sets caused a stronger bycatch pressure on these two species.Most T.tridentatus bycatch and C.rotundicauda bycatch were large individuals in late juvenile and adult stages.Therefore,the ground cages and stick net sets along/near the tidal creeks,mangrove fringe,and low tide line should be regulated and removed to ensure the functionality of the intertidal zone as the spawning corridor and nursery habitat of Asian horseshoe crabs.

Estimating submarine groundwater discharge at a subtropical river estuary along the Beibu Gulf,China

In certain regions,submarine groundwater discharge(SGD)into the ocean plays a significant role in coastal material fluxes and their biogeochemical cycle;therefore,the impact of SGD on the ecosystem cannot be ignored.In this study,SGD was estimated using naturally occurring radium isotopes(^(223)Ra and ^(224)Ra)in a subtropical estuary along the Beibu Gulf,China.The results showed that the Ra activities of submarine groundwater were approximately 10 times higher than those of surface water.By assuming a steady state and using an Ra mass balance model,the SGD flux in May 2018 was estimated to be 5.98×10^(6) m^(3)/d and 3.60×10^(6) m^(3)/d based on 224Ra and 223Ra,respectively.At the same time,the activities of Ra isotopes fluctuated within a tidal cycle;that is,a lower activity was observed at high tide and a higher activity was seen at low tide.Based on these variations,the average tidal pumping fluxes of SGD were 1.15×10^(6) m^(3)/d and 2.44×10^(6) m^(3)/d with 224Ra and 223Ra,respectively.Tidaldriven SGD accounts for 24%-51%of the total SGD.Therefore,tidal pumping is an important driving force of the SGD in the Dafengjiang River(DFJR)Estuary.Furthermore,the SGD of the DFJR Estuary in the coastal zone contributes significantly to the seawater composition of the Beibu Gulf and the material exchange between land and sea.

High Microplastic Contamination in Juvenile Tri-Spine Horseshoe Crabs:A Baseline Study of Nursery Habitats in Northern Beibu Gulf,China

Microplastics(MPs)are ubiquitous in marine sedimentary environments.Their occurrence in horseshoe crabs and interactions with the sedimentary environment has not been determined.In this study,MPs,mostly microfibers,were found in all extracted gastrointestinal tract(GIT)samples of the juvenile Tachypleus tridentatus from the northern Beibu Gulf,China.The MP concentrations(4–53 items ind-1)were higher than those in most marine benthic invertebrates(<15 items ind-1)reported in Chinese waters,despite their generally low level in habitat sediments(9–1818 items kg-1).The correlation between the juveniles and sediments was not evident,but the abundance in juvenile horseshoe crab GITs decreased with ages.The findings were relevant to the life-history characteristics of the species,typically with limited dispersal capability and their spending nine years or longer time living in mangrove wetlands during low tides,with apparent ontogenetic changes in their diets.These baseline data enable a better understanding of MP availability in benthic macroinvertebrates,and the ecological risks present in the ecosystems.

RNA interference reveals chloride channel 7 gene helps short-term hypersalinity stress resistance in Hong Kong oyster Crassostrea hongkongensis

The chloride channel 7 gene(CLC 7)of the Hong Kong oyster Crassostrea hongkongensis was cloned and named ChCLC 7.The cDNA was 2572 bp in length,with a 5′non-coding region containing 25 bp,a 3′non-coding region containing 327 bp,and an open reading frame of 2298 bp.ChCLC 7 has 96.8%and 92.1%homology with CLC 7 of Crassostrea gigas and Crassostrea virginica,respectively,and it was clustered with CLC 7 of C.gigas and C.virginica.QRT-PCR showed that ChCLC 7 was expressed in all eight tissues,with the highest in adductor muscle and second in gill.The ChCLC 7 expression pattern in gill was altered significantly under high salinity stress with an overall upward and then downward trend.After RNA interference,the expression of ChCLC 7 and survival rate of oyster under high salinity stress was reduced significantly,and so did the concentration of hemolymph chloride ion in 48-96 h after RNA interference.We believed that ChCLC 7 could play an important role in osmoregulation of C.hongkongensis by regulating Cl^(-)transport.This study provided data for the analysis of molecular mechanism against oyster salinity stress.

Synergy of heterogeneous Co/Ni dual atoms enabling selective C-O bond scission of lignin coupling with in-situ N-functionalization

Selective cleavage of Csp^(2)-OCH_(3)bond in lignin without breaking other types of C-O bonds followed by N-functionalization is fascinating for on-purpose valorization of biomass.Here,a Co/Ni-based dual-atom catalyst CoNiDA@NC prepared by in-situ evaporation and acid-etching of metal species from tailor-made metal–organic frameworks was efficient for reductive upgrading of various lignin-derived phenols to cyclohexanols(88.5%–99.9%yields),which had ca.4 times higher reaction rate than the single-atom catalyst and was superior to state-of-the-art heterogeneous catalysts.The synergistic catalysis of Co/Ni dual atoms facilitated both hydrogen dissociation and hydrogenolysis steps,and could optimize adsorption configuration of lignin-derived methoxylated phenols to further favor the Csp^(2)-OCH_(3)cleavage,as elaborated by theoretical calculations.Notably,the CoNi_(DA)@NC catalyst was highly recyclable,and exhibited excellent demethoxylation performance(77.1%yield)in real lignin monomer mixtures.Via in-situ cascade conversion processes assisted by dual-atom catalysis,various high-value N-containing chemicals,including caprolactams and cyclohexylamines,could be produced from lignin.

Multi-Strategy Assisted Multi-Objective Whale Optimization Algorithm for Feature Selection

In classification problems,datasets often contain a large amount of features,but not all of them are relevant for accurate classification.In fact,irrelevant features may even hinder classification accuracy.Feature selection aims to alleviate this issue by minimizing the number of features in the subset while simultaneously minimizing the classification error rate.Single-objective optimization approaches employ an evaluation function designed as an aggregate function with a parameter,but the results obtained depend on the value of the parameter.To eliminate this parameter’s influence,the problem can be reformulated as a multi-objective optimization problem.The Whale Optimization Algorithm(WOA)is widely used in optimization problems because of its simplicity and easy implementation.In this paper,we propose a multi-strategy assisted multi-objective WOA(MSMOWOA)to address feature selection.To enhance the algorithm’s search ability,we integrate multiple strategies such as Levy flight,Grey Wolf Optimizer,and adaptive mutation into it.Additionally,we utilize an external repository to store non-dominant solution sets and grid technology is used to maintain diversity.Results on fourteen University of California Irvine(UCI)datasets demonstrate that our proposed method effectively removes redundant features and improves classification performance.The source code can be accessed from the website:https://github.com/zc0315/MSMOWOA.

Rapid Prediction of Wastewater Index Using CNN Architecture and PLS Series Statistical Methods

Chemical oxygen demand (COD) is an important index to measure the degree of water pollution. In this paper, near-infrared technology is used to obtain 148 wastewater spectra to predict the COD value in wastewater. First, the partial least squares regression (PLS) model was used as the basic model. Monte Carlo cross-validation (MCCV) was used to select 25 samples out of 148 samples that did not conform to conventional statistics. Then, the interval partial least squares (iPLS) regression modeling was carried out on 123 samples, and the spectral bands were divided into 40 subintervals. The optimal subintervals are 20 and 26, and the optimal correlation coefficient of the test set (RT) is 0.58. Further, the waveband is divided into five intervals: 17, 19, 20, 22 and 26. When the number of joint intervals under each interval is three, the optimal RT is 0.71. When the number of joint subintervals is four, the optimal RT is 0.79. Finally, convolutional neural network (CNN) was used for quantitative prediction, and RT was 0.9. The results show that CNN can automatically screen the features inside the data, and the quantitative prediction effect is better than that of iPLS and synergy interval partial least squares model (SiPLS) with joint subinterval three and four, indicating that CNN can be used for quantitative analysis of water pollution degree.

Evaluation and Quantitative Attribution Analysis of Water Yield Services in the Peak-cluster Depression Basins in Southwest of Guangxi,China

Karst environmental issues have become one of the hot spots in contemporary international geological research. The same problem of water shortage is one of the hot spots of global concern. The peak-cluster depression basins in southwest of Guangxi is an important water connotation and ecological barrier areas in the Pearl River Basin of China. Thus, studying the spatial and temporal variations and the influencing factors of its water yield services is critical to achieve the sustainable development of water resources and ecological environmental protection in this region. As such, this paper uses the Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST) model to assess the spatial and temporal variabilities of water yield services and its trends in the peak-cluster depression basins in southwest of Guangxi from 2000 to 2020. This work also integrates precipitation(Pre), reference evapotranspiration(ET), temperature(Tem), digital elevation model(DEM), slope, normalized difference vegetation index(NDVI), land use/land cover(LULC) and soil type to reveal the main factors that influence water yield services with the help of Geodetector. Results show that: 1) in time scale,the total annual water yield in the study area show a fluctuating and increasing trend from 2000 to 2020, with a growth rate of 7.3753 × 10^(8)m^(3)/yr, and its multi-year average water yield was 538.07 mm;2) in spatial pattern, with high yield areas mainly distributed in the south of the study area(mainly including Shangsi County, Pingxiang City, Ningming County, Longzhou County and Jingxi County), and low yield areas mainly distributed in Baise City and Nanning City;3) the dominant factor of water yield within karst and non-karst landforms is not necessarily controlled by precipitation, and the explanation degree of DEM factors in karst areas is significantly higher than that in non-karst areas;4) amongst the climatic factors, Pre, ET and Tem are dominant in the spatial pattern of region water yield capacity. among which Pre has the highest explanatory power for the spatial heterogeneity of annual water production, with q values above0.8, and each driver showed a significant interaction on the spatial distribution of water yield, with Pre exhibiting the strongest interaction with LULC.

Distinguishing the main components of submarine groundwater and estimating the corresponding fluxes based on radium tracing method—taking the Maowei Sea for example

Submarine groundwater discharge(SGD)is an important part in the land-sea interactions,which mainly contains three components:submarine fresh groundwater discharge(SFGD),tidal flat recirculated saline groundwater discharge(tidal flat RSGD)and subtidal recirculated saline groundwater discharge(subtidal RSGD).In order to make a more accurate assessment of the impact of SGD on coastal ecological environment,it is necessary to distinguish the main components of SGD.In this study,the Maowei Sea,located in the northern part of the Beibu Gulf,was selected as the study area.Based on the radium(Ra)tracing method,we present a new analytical method for distinguishing the three main components of SGD in this area combined with field data.The average daily flow along the coastline of the Maowei Sea of tidal flat RSGD was slightly higher than that of SFGD,and both two were on the magnitude of 1×10^(5)m^(3)/d.The average daily flow for the subtidal RSGD of the entire subtidal zone of the Maowei Sea reached to the magnitude of 1×10^(6)-1×10^(7)m^(3)/d.The long-term variation trend of terrestrial SGD is a valuable information for the study of the influence of terrigenous material on the coastal ecological environment.Based on the results of four sampling periods,it is found that the fluxes of SFGD and tidal flat RSGD in the Maowei Sea had good linear correlation with the net precipitation.As an example,January 2015 to August 2022 were selected as the study periods,and the variation trends of SFGD and tidal flat RSGD were calculated by linear function with net precipitation as the independent variable.The results showed that the flux of tidal flat RSGD was slightly higher than that of SFGD,and the difference between the two is larger in flood season while smaller in dry season.In general,in the coastal range of China,the total SGD flux in the Maowei Sea area is at a high level,and the SFGD flux is at a medium level.

潮汐通道水动力和泥沙的湍参数化效应:南海北部崖门水道

In this study,we conducted numerical experiments to examine the effects of turbulence parameterization on temporal and spatial variations of suspended sediment dynamics.Then,we applied the numerical model to the Yamen Channel,one of the main eight outfalls in the Pearl River Delta.For the field application,we implemented the k−εscheme with a reasonable stability function using the continuous deposition formula during the erosion process near the water-sediment interface.We further validated and analyzed the temporal-spatial suspended sediment concentrations(SSCs).The experimental results show that under specified initial and boundary conditions,turbulence parameterization with stability functions can lead to different vertical profiles of the velocity and SSC.The k−εpredicts stronger mixing with a maximum value of approximately twice the k−kl.The k−kl results in smaller SSCs near the surface layer and a larger vertical gradient than the k−ε.In the Yamen Channel,though the turbulent dissipation,turbulent viscosity and turbulence kinetic energy exhibit similar trends,SSCs differ significantly between those at low water and high water due to the tidal asymmetry and settling lag mechanisms.The results can provide significant insights into environmental protection and estuarine management in the Pearl River Delta.

Effects of Variable Lighting Intensity on Growth Characteristics and Nutritional Quality of Hydroponically Grown Arugula(Eruca sativa Mill.)

Arugula(Eruca sativa Mill.),as an edible medicinal vegetable of peculiar flavor,is served as uncooked dish.The influence of variable lighting intensity(LI)on the growth characteristics and nutritional quality of hydroponically grown arugula was investigated by using light-emitting diodes(LEDs)to light the hydroponically grown arugula for a reference for industrialized arugula production.The dynamic demands of arugula for LI in the seedling stage,initial growth stage and vigorous growth stage were tested under two light quality conditions including a red/blue light ratio of 7:1 and a light/dark photoperiod of 12 h/12 h.Then,the curves of variable LI-induced changes in the growth indices of arugula in different development periods were drawn.Next,the influence of variable LI on the growth characteristics and nutritional quality of arugula was investigated by measuring the dry/fresh weight ratio,chlorophyll content,vitamin C content and soluble protein content.Variable LI significantly increased the height,stem diameter,leaf width,dry/fresh weight ratio,chlorophyll content and soluble protein content of arugula plant.Plant height,stem diameter,dry/fresh weight ratio,chlorophyll content and soluble protein content were the highest in the group exposed to LI of 200,300 and 300μmol•m^(-2)•s^(-1)during the seedling stage,initial growth stage and vigorous growth stage,respectively.The greatest leaf width was achieved at LI of 100,250 and 350μmol•m^(-2)•s^(-1),respectively.High intensity LI markedly repressed the synthesis of vitamin C.

Sedimentary nitrogen dynamics in a coastal reef area with relatively high nitrogen concentration

The migration and transformation of nitrogen(N)in sediments play an important role in regulating the N concentration and nutrient structures in shallow seas.However,studies of sedimentary N dynamics are rarely focused on carbonate sediments,although these account for about 40%of the continental shelf area.Thus,the regulation mechanisms of the N dynamics in the carbonate sands of coral reefs are not clear.Taking the coral reef area of Weizhou Island,which has a relatively high N concentration,as the research object,we conducted a series of flow-through reactor experiments to investigate the fluxes of different N forms at the interface of sediment and seawater and their regulation mechanism by environmental factors.The fluxes of dissolved inorganic and organic N(DIN and DON)at different stations were-0.39-0.12 mmol/(m^(2)·h) and-0.18-0.39 mmol/(m^(2)·h),respectively.Denitrification(0.11-0.25 mmol/(m^(2)·h) was closely coupled to nitrification,which was limited by the availability of organic matter and its degradation product(i.e.,NH_(4)^(+)).Thus,the excessive NO_(3)^(-) might be reduced to NH4+by dissimilatory nitrate reduction to ammonium,rather than to N_(2) by denitrification.NO_(3)^(-) reduction peaked at intermediate advection rates(96 L/(m^(2)·h)) and flow path lengths(10 cm),but the release of DON also peaked at the same condition.In addition,climate warming would significantly affect sedimentary N dynamics at Weizhou Island.These results may help address the broader issue of the N cycle in coral reef eco systems under the dual pressure of climate warming and anthropogenic activities,and these results are beneficial to coral reef protection and local ecological management.

Cooperative catalysis of Co single atoms and nanoparticles enables selective CAr-OCH_(3) cleavage for sustainable production of lignin-based cyclohexanols

In this work,a dual-size MOF-derived Co catalyst(0.2Co_(1-NPs)@NC)composed of single atoms(Co_(1))and highly dispersed nanoparticles(Co NPs)was prepared by in-situ Zn evaporation for the highperformance conversion of lignin-derived o-methoxyphenols(lignin oil)to cyclohexanols(up to 97%yield)via cascade demethoxylation and dearomatization.Theoretical calculations elaborated that the dual-size Co catalyst exhibited a cooperative effect in the selective demethoxylation process,in which the Co NPs could initially dissociate hydrogen at lower energies while Co1remarkably facilitated the cleavage of the C_(Ar)-OCH_(3)bond.Moreover,the intramolecular hydrogen bonds formed in the omethoxy-containing phenols were found to result in a decrease in the bond energy of the C_(Ar)-OCH_(3)bond,which was more prone to be activated by the dual-size Co sites.Notably,the pre-hydrogenated intermediate(e.g.,2-methoxycyclohexanol from guaiacol)is difficult to undergo demethoxylation,indicating that the selective C_(Ar)-OCH_(3)bond cleavage is a prerequisite for the synthesis of cyclohexanols.The 0.2Co_(1-NPs)@NC catalyst was highly recyclable with a neglect decline in activity during five consecutive cycles.This cooperative catalytic strategy based on the metal size effect opens new avenues for biomass upgrading via enhanced C-O bond cleavage of high selectivity.

Investigating the Long-Term Relationship between Aerosol Optical Thickness and Land Use/Cover Change in Guangxi Coastal Cities, China

Land Use/Cover Change (LUCC) has an impact on AOD to a certain extent. It is of great significance for ecological environment and public health to pay attention to and explore the response mechanism of AOD to LUCC. Based on remote sensing satellite technology, using landsat8 and MODIS data, this paper analyzes the correlation between different land use types and AOD in Beibu Gulf coastal urban belt under the background of wide-scale region and long time series, and further discusses the difference value and contribution level of each LUCC to AOD. The results show that: 1) there is a positive correlation between PM concentration and cultivated land, urban land, water area and other types of land, and the correlation coefficient increases in turn, R is 0.812, 0.685, 0.627, 0.416, respectively, which indicates that the increase of cultivated land and urban land increases PM concentration to a certain extent;2) there is a significant negative correlation between PM concentration and forest land, R is -0.924, The results show that the decrease of woodland is an important factor for the increase of atmospheric particulate matter concentration in the study area from 2015 to 2019;3) through the contribution analysis method, the contribution of cultivated land to AOD is the largest, followed by urban land, and the water area is the smallest in 2015-2019, which indicates that the land use mode is closely related to AOD. It can be helpful to reasonably plan land use types and scientifically optimize land use structure. It can effectively reduce the concentration of air pollution particles.

Preparation, Characteristics, and Formation Mechanism of Oyster Peptide-Zinc Nanoparticles

Oyster peptide zinc nanoparticles (OPZNPs)(28 108 nm) were prepared in the presence of 0.5% 0.9% zinc sulfate at pH 6.0 11.0. The obtained nanoparticles exhibited uniform size distribution and spherical shapes. Nanoparticle characteristics, such as size, surface charge, and hydrophobicity, could be adjusted by controlling zinc sulfate concentration and environmental pH. In- creasing pH value or decreasing zinc sulfate concentration tended to reduce nanoparticle size and increase nanoparticle surface charge and hydrophobicity. OPZNPs presented good stability at near-neutral pH and could be stored for at least 20 days at 4℃. The results of the peptide conformation study and nanoparticle dissociation test proved that zinc ions and carboxyl groups are the key factors that affect OPZNP formation. The intermolecular combinations of carboxyl groups via zinc bridging facilitated the aggrega- tion of oyster peptides. Nanoparticle formation was accompanied by aggregate association and conformational changes. These changes included increments in β-sheets, especially intermolecular β-sheets, at the expense of α-helixes. Overall, this work provided a green alternative route for the synthesis of OPZNPs.

A numerical study on salinity stratification at the Oujiang River Estuary, China

The Oujiang River Estuary(ORE)is a macrotidal estuary with drastic variation of river discharge and large tidal range.Numerical simulations based on the unstructured grid,Finite-Volume,primitive equation Community Ocean Model(FVCOM)are conducted to investigate the intratidal and intertidal variations of salinity with an extremely upstream river boundary and large computational domain.The dynamic equation of potential energy anomaly is adopted to evaluate the stratification and mixing processes from model results.Meanwhile,the stability of estuarine stratification on different timescales and its spatial variation are studied using estuarine Richardson number and stratification parameter.The critical values of tidal range and river discharge that determine the stratification state are obtained.The critical values exhibit distinct spatial difference.The north branch of the ORE exhibits well-mixed conditions when the tidal range exceeds 3.8,4.0 and 4.6m at upper inlet,middle segment and the river mouth,respectively.When river discharge is below 280 m^3/s or exceeds 510 m^3/s,the upper part of the north branch is well-mixed sustainably.Near the river mouth,river discharge of 280 m^3/s is a rough critical value that separates well-mixed and stratified states.It is also concluded that periodic stratification exists in the North Channel.The lower estuary appears to be partially stratified at early ebb or early flood tide,and well-mixed in other tidal stages.The stratification only develops during early ebb in the upper segment.The enhancement of stratification is mainly caused by longitudinal advection and lateral velocity shear,while turbulent mixing and longitudinal tidal strain are the main factors of stratification attenuation.