Coastal ecosystems are plagued by high levels of microplastic pollution.Conducting baseline surveys is crucial to comprehend the distribution and influencing factors of this pollution.The present study investigates th...Coastal ecosystems are plagued by high levels of microplastic pollution.Conducting baseline surveys is crucial to comprehend the distribution and influencing factors of this pollution.The present study investigates the spatiotemporal variation and diversity of microplastic on the coastal beaches in Xiamen City,China,considering the combined effects of seasons,human activities,and physicochemical properties of sediments.It is detected that the abundance of microplastics in Xiamen beaches was 0.271±0.01 items/g.The abundance of microplastics in dry season was significantly higher than in rainy season.In terms of spatial variation,the beaches that attracted a larger number of tourists exhibited significantly higher microplastic abundance.The temporal pattern of microplastic distribution on different beaches varied greatly due to region-specific human activities(e.g.,mangrove restoration project)and sedimentary properties(e.g.,bulk density).When the assemblage of microplastics in the coastal area was viewed as a biological community,the Shannon-Wiener index and Pielou's index were higher in rainy season and in the beaches with high intensity of tourist activities,which suggests that the human activities and the surface runoff may contribute to the diversity of microplastics on coastal beaches.Future investigations are encouraged to combine controlled experiments and long-term monitoring at multiple scales to elucidate the underlying mechanisms and factors associated with microplastic pollution in coastal zone.展开更多
The paper is focused on the design of artificial sand beaches at sheltered and exposed sites.The methodology applied includes the study of the most essential design parameters and the application of numerical models t...The paper is focused on the design of artificial sand beaches at sheltered and exposed sites.The methodology applied includes the study of the most essential design parameters and the application of numerical models to compute the beach erosion and maintenance.The computed erosion volume decreases for coarser sand(0.5 mm sand instead of 0.3 mm).Beach erosion increases for more graded sand,but the effect is small(10%–15%).The slope of the artificial beach at sheltered sites is commonly between 1 to 15 and 1 to 30 in conditions with a micro tidal range and mild waves.Slopes between 1 to 30 and 1 to 50 are used for more open exposed sites.The effect of the upper and lower beach slope(1 to 15 or 1 to 20)on beach erosion is marginal for sand in the range of 0.3 to 0.5 mm.A break in slope is quickly adjusted by transport processes.The volume of beach sand required may be reduced by constructing a submerged sill at the toe of the beach.Analysis of costs shows that the construction costs including maintenance over a period of 50 years of a submerged sill are about the same as that of beach fill including maintenance.Hence,the beach fill volume can be twice as large for a solution without a sill.Beach erosion due to alongshore transport processes is minimum if the beach line of the planform is perpendicular to the main wave direction(equilibrium beach).展开更多
The Ba Lang sand beaches, located north of the Nha Trang Bay in Central Vietnam, are famous tourist attractions. However, they are experiencing shoreline and coastal erosion retreat, which is attributed to natural cau...The Ba Lang sand beaches, located north of the Nha Trang Bay in Central Vietnam, are famous tourist attractions. However, they are experiencing shoreline and coastal erosion retreat, which is attributed to natural causes (such as tropical depressions, storms, and monsoons) as well as human impacts (such as hydropower generation, sand dredging, and coastal works). According to the forecast of the Vietnam Ministry of Natural Resources and Environment, global climate change will cause the sea level to rise by 74 cm along the coast from the Dai Lanh Cape to the Ke Ga Cape (including the Ba Lang beaches) by the end of this century in the representative concentration pathway (RCP) 8.5 scenario. Sea level rise (SLR) due to global climate change is expected to aggravate the coastal erosion and shoreline retreat problems. In this study, coupled numerical models with the spectral wave module (MIKE 21 SW), hydrodynamic module (MIKE 21 HD), and sand transport module (MIKE 21 ST) in the MIKE 21 package were used to simulate waves, current fields, and sediment dynamics along the Ba Lang beaches considering the impact of SLR. These models were calibrated with the field data measured in December 2016. The results showed that SLR caused the wave height to increase and reduced the current speed and total sediment load in monsoon conditions. The increase in wave height was even intensified under the joint impact of SLR and extreme events.展开更多
Major differences in beach erosion between two neighboring artificial beaches Xiangluwan Beach(XL beach)and Meiliwan Beach(ML beach)in Zhuhai,China,were studied after Super Typhoon Hato.In this study,a fully nonlinear...Major differences in beach erosion between two neighboring artificial beaches Xiangluwan Beach(XL beach)and Meiliwan Beach(ML beach)in Zhuhai,China,were studied after Super Typhoon Hato.In this study,a fully nonlinear Boussinesq wave model(FUNWAVE)-Total Variation Diminishing(TVD)was used to distinguish the main impact factors,their relative contributions,and the hydrodynamic mechanisms underlying the different beach responses.Results show that compared to the ML beach,the main reason for the relatively weak erosion on Xiangluwan(XL)beach was the smaller beach berm height(accounting for approximately 75.9%of the erosion response).Regarding the beach with a higher berm,the stronger wave-induced undertow flow,along with the higher sediment concentration,led to a higher offshore sediment transport flux,resulting in more severe erosion relative to the beach with a smaller berm height.The second most important reason explaining the weak erosion on XL beach was the absence of seawalls(accounting for approximately 17.9%of the erosion response).Wave reflection induced by the seawall could cause higher suspended sediment concentration,resulting in a toe scouring near the seawall.The offshore submerged breakwater protected XL beach slightly(accounting for approximately 6.1%of the erosion response).Due to the higher water level induced by storm surge,most of the wave energy could penetrate through the submerged breakwater.The effect of the larger berm width of XL beach was negligible.Compared to the beach with a larger berm width,the erosion/deposition regions in the beach with a narrower berm width showed shoreward migration,without significant changes in the erosion/deposition extent.Despite of this,the larger berm width could reduce the wave energy reaching the shoreline.This study of the storm stability of artificial beaches may be applied to beach restoration design.展开更多
Through investigating ten recreational marine beaches in China, we aimed to detect the occurrence of human enteric viruses in coastal bathing beaches and find a correlationship, if any, between the presence of enteric...Through investigating ten recreational marine beaches in China, we aimed to detect the occurrence of human enteric viruses in coastal bathing beaches and find a correlationship, if any, between the presence of enteric viruses in surface seawater and the concentrations of fecal coliforms, the conventional indicator of fecal pollution. In this study, twenty seawater samples were assayed for fecal coliforms and human pathogenic enteric viruses （hepatitis A viruses, rotaviruses, polioviruses） analysis. Enteric viruses were detected by RT-PCR, in 20 sample sites, 5%, 40%, 40% were positive for the presence of human hepatitis A viruses, rotaviruses, polioviruses, respectively. Seven of 20 sites are suffering from severe fecal contamination, based on traditional plate counts of fecal coliform outnumbering the established thresholds for recreation. Additionally, statistical analysis presented that no correlation was found between bacterial indicators and viruses in surface seawaters. The data confirmed that indicator bacteria in water are not reflective of the presence of enteric viruses in marine waters. Thus, current recreational water quality standards of both bacterial and viral indices should be reevaluated.展开更多
This study aimed to determine variations in water quality index(WQI)and physicochemical properties of surface water and bottom sediments of selected coastal beaches of Niger Delta,Southern Nigeria.The water quality of...This study aimed to determine variations in water quality index(WQI)and physicochemical properties of surface water and bottom sediments of selected coastal beaches of Niger Delta,Southern Nigeria.The water quality of the river is categorized into five classes,which are classes I,II,III,IV and V based on the WQI(derived from the determination of DO,BOD,COD,TSS and ammonia and pH).Water and bottom sediment samples were analysed using standard procedures.During the wet season,physicochemical parameters such as potential hydrogen(pH),electrical conductivity(EC),dissolved oxygen(DO),total dissolved solids(TDS)and salinity showed significant difference(p<0.05)across all the locations.During the dry season,parameters like EC,EA,pH,sodium(Na),sulphate(SO4),chloride(Cl-),potassium(K),effective cation exchange capacity(ECEC)and calcium(Ca)showed significant difference(p<0.05)across all the six sampled beaches while phosphate(PO4)did not show any clear significant difference across all the sampled locations.The general trend in the levels of physicochemical parameters revealed that temperature and pH were within those recommended by World Health Organization(WHO)and United States Environmental Protection Agency(USEPA)for both wet and dry season but EC and TDS were above the WHO and USEPA limit.Twenty one(21)water quality parameters from six sampling locations were studied and by applying WQI,the state of the six beach water was very unsuitable for drinking,swimming and recreational activities as at the time of this study.The water is only suitable for irrigation purpose.展开更多
Horseshoe crab juveniles have been recorded from sand and sandy-mud nursery beaches at Pak Nai (western New Territories), San Tau and Shui Hau (Lantau Island), Hong Kong. In order to provide a better understanding of ...Horseshoe crab juveniles have been recorded from sand and sandy-mud nursery beaches at Pak Nai (western New Territories), San Tau and Shui Hau (Lantau Island), Hong Kong. In order to provide a better understanding of these beaches and to identify those plausible factors which have made them preferred by spawning horseshoe crabs, environmental parameters, including temperature, salinity, pH and dissolved oxygen content of the water, and particle size distribution and organic matter content of the sediments at the three sites, were determined and compared. The hydrographic and sediment data obtained for the three study sites have revealed some common environmental features. The three nursery beaches are relatively remote, and far (in Hong Kong terms) from urbanized and densely populated areas. The beaches are generally well sheltered from strong wave action and inundated regularly by estuarine waters. Horseshoe crab adults tend to select these beaches for spawning as their protected features ensures the laid eggs are less likely to be washed out of the sand, and hatched juveniles can feed on the meiofauna and grow. Sediments of the three beaches largely comprise medium-sized sand particles and are moderately sorted, suggesting medium porosity and good water permeability. Such a sand type, with the generally high oxygen levels in incursing waters, may help create a well-oxygenated micro-environment for the normal development of horseshoe crab eggs, larvae and juveniles. Lantau Island beaches at San Tau and Shui Hau are relatively free from organic pollution, as reflected in generally high dissolved oxygen level, and low BOD 5 and ammonia nitrogen values. Pak Nai is, however, more polluted.展开更多
In this study,the distribution pattern of meiofauna from nine sandy beaches at six latitudinal gradients along Chinese coast between 18 and 40?N was studied on their meiofauna abundance to examine the effect of latitu...In this study,the distribution pattern of meiofauna from nine sandy beaches at six latitudinal gradients along Chinese coast between 18 and 40?N was studied on their meiofauna abundance to examine the effect of latitudinal gradients.In general,meiofauna abundance was lower in four subtropical beaches in Xiamen(24?N) and Zhoushan(29?N) than that in other beaches.Meiofauna abundance differed little between tropical and temperate beaches.The taxonomic structure of meiofauna showed a dominance of nematode in colder area.The relative composition of turbellarians and polychaetes increased in warmer area.In addition to latitudinal gradient,salinity,oxygenation,sediment grain size affect also the meiofauna latitudinal distribution.As for horizontal distribution,the highest meiofauna abundance was found in low tidal zone at tropical beaches,and in middle tidal zone at temperate beaches.The horizontal distribution of meiofauna was controlled by both physical and biotic factors including feeding and anthropogenic activities.Although meiofauna abundance exhibited a horizontal difference,the composition of meiofaunal main taxa was unanimous horizontally at all beaches at the same sampling latitude.展开更多
Eight representative beach profiles on the eastern coast of the Shandong Peninsula are observed and measured in 2011 and 2012 to determine the coastal processes under the lower tropical wind speed condition and the be...Eight representative beach profiles on the eastern coast of the Shandong Peninsula are observed and measured in 2011 and 2012 to determine the coastal processes under the lower tropical wind speed condition and the beach response to and recovery from the tropical storm Meari in a rare typhoon region. The results show that it is the enhancement and directional change of cross-shore and longshore sediment transports caused by Meari that leads to the beach morphological changes, and most of the sediment transports occur during the pre-Meari landing phase. The erosional scarp formation and the berm or beach face erosion are the main geomorphological responses of the beaches to the storm. The storm characteristics are more important than the beach shapes in the storm response process of the beaches on Shandong Peninsula. The typhoon is a fortuitous strong dynamic event, and the effect on the dissipative beach is more obvious than it is on the reflective beach in the study region. Furthermore, the beach trend is the main factor that controlls the storm effect intensity, and it is also closely related to the recovery of the beach profiles.展开更多
This paper reviews and discusses the current research status, trends, and future needs in the field of beach morphodynamics under the influence of storm sequences.The paper reviews how the three main research methods,...This paper reviews and discusses the current research status, trends, and future needs in the field of beach morphodynamics under the influence of storm sequences.The paper reviews how the three main research methods, field investigations, numerical modelling, and physical modelling, have been used to study beach morphodynamics during storm sequences.Available quantitative definitions of storm sequences at different sites are presented and discussed.It is shown that the definition of storm sequences is site-specific and requires knowledge of the storm climate, beach characteristics, and the temporal scale of beach recovery.Subsequently, the paper brings together currently available approaches aimed at describing the effect of storm sequences on beach erosion in a general way.The importance of storm chronology and the effects of an extreme storm within a sequence of storms are highlighted.Following that, the more poorly studied aspect of beach recovery in between storms within a sequence is discussed.Three indicators for defining beach recovery, namely the shoreline location, sediment volumes, and the beach state, are identified and compared.Finally, important research needs, including the need for detailed physical modelling, are identified.展开更多
River training walls have been built at scores of locations along the NSW coast and their impacts on shoreline change are still not fully understood. In this study, the Brunswick River entrance and adjacent beaches ar...River training walls have been built at scores of locations along the NSW coast and their impacts on shoreline change are still not fully understood. In this study, the Brunswick River entrance and adjacent beaches are selected for examination of the impact of the construction of major training walls. Thirteen sets of aerial photographs taken between 1947 and 1994 are used in a GIS approach to accurately determine the shoreline position, beach contours and sand volumes, and their changes in both time and space, and then to assess the contribution of both the structures and natural hydrodynamic conditions to large scale (years-decades and kilometres) beach changes. The impact of the training walls can be divided into four stages: natural conditions prior to their construction (pre 1959), major downdrift erosion and updrift accretion during and following the construction of the walls in 1959～1962 and 1966, diminishing impact of the walls between 1966 and 1987, and finally no apparent impact between 1987～1994. The impact extends horizontally about 8 km updrift and 17 km downdrift, and temporally up to 25 years.展开更多
Studies on the erosion processes and protective measures at the downcoast of the Friendship Port in Mauritania have been successfully conducted by means of 3-D movable-bed model using light model-sand. The headland co...Studies on the erosion processes and protective measures at the downcoast of the Friendship Port in Mauritania have been successfully conducted by means of 3-D movable-bed model using light model-sand. The headland control was accepted for the stability of the beach. This paper mainly deals with the shape, orientation, size and erosion depth of the artificial headland. Various forms of headland projects, such as the normal groin, arch groins bending to upcoast ancj to downcoast, offshore breakwater, and T-shaped dike, have been experimentally investigated. Through a comparison of effects of these works on the beach processes, optimized headlands have been obtained, that is, unsymmetrical T-shaped dike or arch groin bending to the downcoast, which has been practically and successfully applied for the stability of beaches.展开更多
Shoreline change analysis frequently begins with feature identification through visual interpretation(proxy-based shoreline)or the intersection of a specific tidal zone(datum-based shoreline).Using proxy-based shoreli...Shoreline change analysis frequently begins with feature identification through visual interpretation(proxy-based shoreline)or the intersection of a specific tidal zone(datum-based shoreline).Using proxy-based shoreline information,this study quantifies the distance between proxy-based and datum-based shoreline data,which is defined as the proxydatum bias.The study was conducted at meso-tidal beaches in Kuala Nerus,Terengganu,Malaysia,with morphodynamic responses to northeast and southwest monsoons.The high-water line(HWL)shoreline(proxy-based)was determined using ortho-rectified aerial images captured by an unmanned aerial vehicle(UAV).By contrast,the mean high-water(MHW)shoreline(datum-based)was determined using measured beach profiles adjusted with the Peninsular Malaysia Geodetic Vertical Datum(DTGSM).The theoretical proxy-datum bias was approximated using the best estimate(median)for the beach slope,wave height,and wave period from the estimated total water level(TWL)model.Based on the study,the recorded horizontal proxy-datum bias for the research area was up to 32 m.This study also discovered that the theoretical assumption of the proxy-datum bias based on the TWL model yields values comparable to those of the measurements,with a narrower distinction in bias for steeper beach slopes than the obtained results.The determined proxydatum bias value can benefit future shoreline change studies as it could be incorporated to either proxy-based shorelines by shifting the shoreline seaward or to datum-based shorelines by shifting the shoreline landward in order of the bias value.The seasonal monsoon’s effect on beach profiles should be considered when calculating bias values and conducting potential shoreline change rate studies.展开更多
Bathing beaches are usually the first to suffer disasters when tsunamis occur,owing to their proximity to the sea.Several large seismic fault zones are located off the coast of China.The impact of each tsunami scenari...Bathing beaches are usually the first to suffer disasters when tsunamis occur,owing to their proximity to the sea.Several large seismic fault zones are located off the coast of China.The impact of each tsunami scenario on Chinese bathing beaches is different.In this study,numerical models of the worst tsunami scenarios associated with seismic fault zones were considered to assess the tsunami hazard of bathing beaches in China.Numerical results show that tsunami waves from the Pacific Ocean could affect the East China Sea coast through gaps between the Ryukyu Islands.The Zhejiang and Shanghai coasts would be threatened by a tsunami from Ryukyu Trench,and the coasts of Hainan and Guangdong provinces would be threatened by a tsunami from the Manila Trench.The tsunami hazard associated with the Philippine Trench scenario needs particular attention.Owing to China’s offshore topography,the sequential order of tsunami arrival times to coastal provinces in several tsunami scenarios is almost the same.According to the tsunami hazard analysis results,Yalongwan Beach and eight other bathing beaches are at the highest hazard level.A high-resolution numerical calculation model was established to analyze the tsunami physical characteristics for the high-risk bathing beaches.To explore mitigating effects of a tsunami disaster,this study simulated tsunami propagation with the addition of seawalls.The experimental results show that the tsunami prevention seawalls constructed in an appropriate shallow water location have some effect on reducing tsunami hazard.Seawalls separated by a certain distance work even better.The analysis results can provide a scientific reference for subsequent preventive measures such as facility construction and evacuation.展开更多
A numerical model of shoreline change of sand beaches based on long-term field wave data is proposed, the explicit and implicit finite difference forms of the model are described, and an application of the model is pr...A numerical model of shoreline change of sand beaches based on long-term field wave data is proposed, the explicit and implicit finite difference forms of the model are described, and an application of the model is presented. Results of the application indicate that the model is sensitive to the order of the input wave data, and that the effects of long-term wave series and the effects of the mean annual wave conditions on the model are different. Instead of a single wave condition, the wave series will make the calibration and the verification of the model more practical and the results of the model more reasonable.展开更多
The clay mineralogy of 28 sandy-muddy transitional beach(SMT-Beach)sediments and surrounding mountain river sediments along the coasts of southeastern China was systematically investigated to reveal the sediment sourc...The clay mineralogy of 28 sandy-muddy transitional beach(SMT-Beach)sediments and surrounding mountain river sediments along the coasts of southeastern China was systematically investigated to reveal the sediment source-to-sink process variations of such beaches and their morphological indications.The results show that the clay mineral assemblages of these SMT-Beaches mainly comprise of almost equal illite(~30%),kaolinite(~28%),chlorite(~22%),and smectite(~20%)contents.From the surrounding mountain rivers to the SMT-Beaches,clay mineral assemblages show distinct spatial changes characterized by a large decrease(~40%)in kaolinite,whereas the other three clay minerals present relative increases,especially clear for smectite.The muddy sediment sources of SMT-Beaches inferred from the clay mineralogy are mainly derived from nearby mountain rivers coupled with long-distance transport and penetration of the Changjiang River.The sandy sediments of these beaches are predominantly sourced from nearby mountain rivers,the weathering products of surrounding rocks in both mainland and island environments,and erosion of the“Old Red Sand”and“Red Soil Platform”.However,the sandy sediment sources of the SMT-Beaches are largely reduced because of the remarkable decrease in the river fluvial supply associated with intensive human activities such as dam construction and coastal reclamation.Subsequently,the sandy sections of SMT-Beaches present clear erosion and have revealed by both time series remote sensing images and a compilation of published literature.In contrast,the muddy sediment supply of SMT-Beaches is temporarily stable and relatively constant,resulting in the landward migration of the mudflats with relative transgression or accumulation.These findings highlight that the natural evolution processes of SMT-Beaches have been greatly reshaped by intensive human activities.展开更多
A straightforward conceptual method is proposed to quantitatively assess the seasonal-scale tendency of retreatment or advancement on microtidal beaches by using the backshore/foreshore length ratio. This method is ba...A straightforward conceptual method is proposed to quantitatively assess the seasonal-scale tendency of retreatment or advancement on microtidal beaches by using the backshore/foreshore length ratio. This method is based on measuring the cross-shore profile of a beach when it passes through the “transitional state” that separates the high-from the low-energy season, period during which the morphological characteristics of the beach tend to its equilibrium profile. In order to obtain real measurements of backshore (B) and foreshore (F), the definition of the limits bounding these two important components in subaerial beaches is reviewed and discussed. The approach based on the measurement of the?B/F?length ratio assumes that foreshore and backshore have equivalent lengths in beaches that approximate to their state of morphodynamic equilibrium (B/F?~ 1). A backshore length exceeding the foreshore length is indicative of a state of beach recession, with a?B/F?length ratio > 1. When the foreshore length is greater than the backshore length, the shoreline is advancing or, alternatively, it is developing in a state of morphological confinement,?i.e.?due to the presence of a sea cliff, with a?B/F?< 1. This practical method is then tested against 36 sand and gravel microtidal beach profiles measured along the coasts of Basilicata, in southern Italy. The various “beach states” are summarised into seven classes (I-VII), each identified from specific value intervals of the?B/F?length ratio.展开更多
The aim of this paper is to analyze volleyball practice in the beaches of Copacabana(Rio de Janeiro,Brazil)and Carcavelos and Cascais Bay(Cascais,Portugal)and to review the forms of appropriation of public space based...The aim of this paper is to analyze volleyball practice in the beaches of Copacabana(Rio de Janeiro,Brazil)and Carcavelos and Cascais Bay(Cascais,Portugal)and to review the forms of appropriation of public space based on public policies and rules of the sport in question.Our methodology rests on bibliographic review and ethnographic research to map and distinguish the results in two spatial and cultural contexts that are considerably diverse.Results show that even with greater extension of Copacabana beach in comparison with Cascais,volleyball has a relevant impact in both areas.The installation of the necessary equipment for volleyball practice is also a form of impact in the landscape and establishment of territoriality,which is mainly activated when the game happens.展开更多
In the paper, it is discussed reinforced coastal zones with resort-recreational functions, destructed in terms of anthropogenic pressure of the Black Sea, Georgia. Results of many years’ observations and researches p...In the paper, it is discussed reinforced coastal zones with resort-recreational functions, destructed in terms of anthropogenic pressure of the Black Sea, Georgia. Results of many years’ observations and researches prove low effectiveness of active methods of coastal protection, mostly causing and provoking intensive degradation of the beaches. Article highlights developing and constructing of free and unbounded beaches as an optimal coastal protection approach. Successful example of this approach was developing of coastal zone in 90s, in Gagra (West Georgia), Black Sea. Positive impact of this kind of artificial beach still survives. In the thesis, it is presented an attempt to scientifically prove extrapolation-traduction on the other similar coasts of the recovery of Gagra Zone beach. Based on morphodynamic analysis and comparison, according to the priorities of major features of reinforced coasts, it turned out that coast of three similar objects (Gagra, Ochamchire and Sokhumi) show homogenous aspects. Scientific expediency of providing extrapolation on other similar objects of etalon objects i.e. Gagra Beach recovered by successful coastal protection experiment. Thereby, for the purposes of creating free-artificial beach, choosing of wrecking zone of Ochamchire is based on coastal protection effectiveness and economical principals, including technical-economical effectiveness.展开更多
Using gamma-ray spectrometry, the activity concentration of naturally occurring radionuclides 226Ra, 212Pb, 214Pb, 232Th, and 40K was determined in sand beaches samples from different areas in Guarapari, Espírito...Using gamma-ray spectrometry, the activity concentration of naturally occurring radionuclides 226Ra, 212Pb, 214Pb, 232Th, and 40K was determined in sand beaches samples from different areas in Guarapari, Espírito Santo state, from Brazil. The absorbed dose rates and annual effective dose were calculated and the results were compared with the internationally accepted values as well as others high background radiation areas (HBRAs). The activity concentration of the 232Th in Areia Preta as well as the absorbed dose rates and annual effective dose were higher than the others regions compared. The results show that Areia Preta in Guarapari has higher background found in beaches in world. This work is part of a research project for the natural background determination of the Brazilian coast.展开更多
基金Supported by the Natural Science Foundation of Fujian Province(No.2022J05278)the Marine and Fishery Development Special Fund of Xiamen(No.23YYST064QCB36)。
文摘Coastal ecosystems are plagued by high levels of microplastic pollution.Conducting baseline surveys is crucial to comprehend the distribution and influencing factors of this pollution.The present study investigates the spatiotemporal variation and diversity of microplastic on the coastal beaches in Xiamen City,China,considering the combined effects of seasons,human activities,and physicochemical properties of sediments.It is detected that the abundance of microplastics in Xiamen beaches was 0.271±0.01 items/g.The abundance of microplastics in dry season was significantly higher than in rainy season.In terms of spatial variation,the beaches that attracted a larger number of tourists exhibited significantly higher microplastic abundance.The temporal pattern of microplastic distribution on different beaches varied greatly due to region-specific human activities(e.g.,mangrove restoration project)and sedimentary properties(e.g.,bulk density).When the assemblage of microplastics in the coastal area was viewed as a biological community,the Shannon-Wiener index and Pielou's index were higher in rainy season and in the beaches with high intensity of tourist activities,which suggests that the human activities and the surface runoff may contribute to the diversity of microplastics on coastal beaches.Future investigations are encouraged to combine controlled experiments and long-term monitoring at multiple scales to elucidate the underlying mechanisms and factors associated with microplastic pollution in coastal zone.
文摘The paper is focused on the design of artificial sand beaches at sheltered and exposed sites.The methodology applied includes the study of the most essential design parameters and the application of numerical models to compute the beach erosion and maintenance.The computed erosion volume decreases for coarser sand(0.5 mm sand instead of 0.3 mm).Beach erosion increases for more graded sand,but the effect is small(10%–15%).The slope of the artificial beach at sheltered sites is commonly between 1 to 15 and 1 to 30 in conditions with a micro tidal range and mild waves.Slopes between 1 to 30 and 1 to 50 are used for more open exposed sites.The effect of the upper and lower beach slope(1 to 15 or 1 to 20)on beach erosion is marginal for sand in the range of 0.3 to 0.5 mm.A break in slope is quickly adjusted by transport processes.The volume of beach sand required may be reduced by constructing a submerged sill at the toe of the beach.Analysis of costs shows that the construction costs including maintenance over a period of 50 years of a submerged sill are about the same as that of beach fill including maintenance.Hence,the beach fill volume can be twice as large for a solution without a sill.Beach erosion due to alongshore transport processes is minimum if the beach line of the planform is perpendicular to the main wave direction(equilibrium beach).
文摘The Ba Lang sand beaches, located north of the Nha Trang Bay in Central Vietnam, are famous tourist attractions. However, they are experiencing shoreline and coastal erosion retreat, which is attributed to natural causes (such as tropical depressions, storms, and monsoons) as well as human impacts (such as hydropower generation, sand dredging, and coastal works). According to the forecast of the Vietnam Ministry of Natural Resources and Environment, global climate change will cause the sea level to rise by 74 cm along the coast from the Dai Lanh Cape to the Ke Ga Cape (including the Ba Lang beaches) by the end of this century in the representative concentration pathway (RCP) 8.5 scenario. Sea level rise (SLR) due to global climate change is expected to aggravate the coastal erosion and shoreline retreat problems. In this study, coupled numerical models with the spectral wave module (MIKE 21 SW), hydrodynamic module (MIKE 21 HD), and sand transport module (MIKE 21 ST) in the MIKE 21 package were used to simulate waves, current fields, and sediment dynamics along the Ba Lang beaches considering the impact of SLR. These models were calibrated with the field data measured in December 2016. The results showed that SLR caused the wave height to increase and reduced the current speed and total sediment load in monsoon conditions. The increase in wave height was even intensified under the joint impact of SLR and extreme events.
基金Supported by the National Natural Science Foundation of China(Nos.42006176,42330406,U1706220,41901006)the Basic Research Project of the Science and Technology Innovation Development Program of in Yantai(No.2022JCYJ028)。
文摘Major differences in beach erosion between two neighboring artificial beaches Xiangluwan Beach(XL beach)and Meiliwan Beach(ML beach)in Zhuhai,China,were studied after Super Typhoon Hato.In this study,a fully nonlinear Boussinesq wave model(FUNWAVE)-Total Variation Diminishing(TVD)was used to distinguish the main impact factors,their relative contributions,and the hydrodynamic mechanisms underlying the different beach responses.Results show that compared to the ML beach,the main reason for the relatively weak erosion on Xiangluwan(XL)beach was the smaller beach berm height(accounting for approximately 75.9%of the erosion response).Regarding the beach with a higher berm,the stronger wave-induced undertow flow,along with the higher sediment concentration,led to a higher offshore sediment transport flux,resulting in more severe erosion relative to the beach with a smaller berm height.The second most important reason explaining the weak erosion on XL beach was the absence of seawalls(accounting for approximately 17.9%of the erosion response).Wave reflection induced by the seawall could cause higher suspended sediment concentration,resulting in a toe scouring near the seawall.The offshore submerged breakwater protected XL beach slightly(accounting for approximately 6.1%of the erosion response).Due to the higher water level induced by storm surge,most of the wave energy could penetrate through the submerged breakwater.The effect of the larger berm width of XL beach was negligible.Compared to the beach with a larger berm width,the erosion/deposition regions in the beach with a narrower berm width showed shoreward migration,without significant changes in the erosion/deposition extent.Despite of this,the larger berm width could reduce the wave energy reaching the shoreline.This study of the storm stability of artificial beaches may be applied to beach restoration design.
基金provided by the National High Technology Research and Development Program("863"Program)of China,grant no.2006AA09Z162the National Key Scientific and Technological Project,grant no.908-01-ZH3
文摘Through investigating ten recreational marine beaches in China, we aimed to detect the occurrence of human enteric viruses in coastal bathing beaches and find a correlationship, if any, between the presence of enteric viruses in surface seawater and the concentrations of fecal coliforms, the conventional indicator of fecal pollution. In this study, twenty seawater samples were assayed for fecal coliforms and human pathogenic enteric viruses （hepatitis A viruses, rotaviruses, polioviruses） analysis. Enteric viruses were detected by RT-PCR, in 20 sample sites, 5%, 40%, 40% were positive for the presence of human hepatitis A viruses, rotaviruses, polioviruses, respectively. Seven of 20 sites are suffering from severe fecal contamination, based on traditional plate counts of fecal coliform outnumbering the established thresholds for recreation. Additionally, statistical analysis presented that no correlation was found between bacterial indicators and viruses in surface seawaters. The data confirmed that indicator bacteria in water are not reflective of the presence of enteric viruses in marine waters. Thus, current recreational water quality standards of both bacterial and viral indices should be reevaluated.
文摘This study aimed to determine variations in water quality index(WQI)and physicochemical properties of surface water and bottom sediments of selected coastal beaches of Niger Delta,Southern Nigeria.The water quality of the river is categorized into five classes,which are classes I,II,III,IV and V based on the WQI(derived from the determination of DO,BOD,COD,TSS and ammonia and pH).Water and bottom sediment samples were analysed using standard procedures.During the wet season,physicochemical parameters such as potential hydrogen(pH),electrical conductivity(EC),dissolved oxygen(DO),total dissolved solids(TDS)and salinity showed significant difference(p<0.05)across all the locations.During the dry season,parameters like EC,EA,pH,sodium(Na),sulphate(SO4),chloride(Cl-),potassium(K),effective cation exchange capacity(ECEC)and calcium(Ca)showed significant difference(p<0.05)across all the six sampled beaches while phosphate(PO4)did not show any clear significant difference across all the sampled locations.The general trend in the levels of physicochemical parameters revealed that temperature and pH were within those recommended by World Health Organization(WHO)and United States Environmental Protection Agency(USEPA)for both wet and dry season but EC and TDS were above the WHO and USEPA limit.Twenty one(21)water quality parameters from six sampling locations were studied and by applying WQI,the state of the six beach water was very unsuitable for drinking,swimming and recreational activities as at the time of this study.The water is only suitable for irrigation purpose.
文摘Horseshoe crab juveniles have been recorded from sand and sandy-mud nursery beaches at Pak Nai (western New Territories), San Tau and Shui Hau (Lantau Island), Hong Kong. In order to provide a better understanding of these beaches and to identify those plausible factors which have made them preferred by spawning horseshoe crabs, environmental parameters, including temperature, salinity, pH and dissolved oxygen content of the water, and particle size distribution and organic matter content of the sediments at the three sites, were determined and compared. The hydrographic and sediment data obtained for the three study sites have revealed some common environmental features. The three nursery beaches are relatively remote, and far (in Hong Kong terms) from urbanized and densely populated areas. The beaches are generally well sheltered from strong wave action and inundated regularly by estuarine waters. Horseshoe crab adults tend to select these beaches for spawning as their protected features ensures the laid eggs are less likely to be washed out of the sand, and hatched juveniles can feed on the meiofauna and grow. Sediments of the three beaches largely comprise medium-sized sand particles and are moderately sorted, suggesting medium porosity and good water permeability. Such a sand type, with the generally high oxygen levels in incursing waters, may help create a well-oxygenated micro-environment for the normal development of horseshoe crab eggs, larvae and juveniles. Lantau Island beaches at San Tau and Shui Hau are relatively free from organic pollution, as reflected in generally high dissolved oxygen level, and low BOD 5 and ammonia nitrogen values. Pak Nai is, however, more polluted.
基金supported by the National Natural Science Foundation of China (Nos.40906063,40730847,41106122,and 41076090)
文摘In this study,the distribution pattern of meiofauna from nine sandy beaches at six latitudinal gradients along Chinese coast between 18 and 40?N was studied on their meiofauna abundance to examine the effect of latitudinal gradients.In general,meiofauna abundance was lower in four subtropical beaches in Xiamen(24?N) and Zhoushan(29?N) than that in other beaches.Meiofauna abundance differed little between tropical and temperate beaches.The taxonomic structure of meiofauna showed a dominance of nematode in colder area.The relative composition of turbellarians and polychaetes increased in warmer area.In addition to latitudinal gradient,salinity,oxygenation,sediment grain size affect also the meiofauna latitudinal distribution.As for horizontal distribution,the highest meiofauna abundance was found in low tidal zone at tropical beaches,and in middle tidal zone at temperate beaches.The horizontal distribution of meiofauna was controlled by both physical and biotic factors including feeding and anthropogenic activities.Although meiofauna abundance exhibited a horizontal difference,the composition of meiofaunal main taxa was unanimous horizontally at all beaches at the same sampling latitude.
基金The National Natural Science Foundation of China under contract No.41030856the Marine Specific Welfare Project of China under contract No.200905008-4the Project of Taishan Scholar
文摘Eight representative beach profiles on the eastern coast of the Shandong Peninsula are observed and measured in 2011 and 2012 to determine the coastal processes under the lower tropical wind speed condition and the beach response to and recovery from the tropical storm Meari in a rare typhoon region. The results show that it is the enhancement and directional change of cross-shore and longshore sediment transports caused by Meari that leads to the beach morphological changes, and most of the sediment transports occur during the pre-Meari landing phase. The erosional scarp formation and the berm or beach face erosion are the main geomorphological responses of the beaches to the storm. The storm characteristics are more important than the beach shapes in the storm response process of the beaches on Shandong Peninsula. The typhoon is a fortuitous strong dynamic event, and the effect on the dissipative beach is more obvious than it is on the reflective beach in the study region. Furthermore, the beach trend is the main factor that controlls the storm effect intensity, and it is also closely related to the recovery of the beach profiles.
基金supported by the EPSRC FloodMEMORY Project(Grant No.EP/K013513/1)the HYDRALAB~+ Integrated Infrastructure Initiative,RESIST(Contract No.654110)Horizon 2020,European Community
文摘This paper reviews and discusses the current research status, trends, and future needs in the field of beach morphodynamics under the influence of storm sequences.The paper reviews how the three main research methods, field investigations, numerical modelling, and physical modelling, have been used to study beach morphodynamics during storm sequences.Available quantitative definitions of storm sequences at different sites are presented and discussed.It is shown that the definition of storm sequences is site-specific and requires knowledge of the storm climate, beach characteristics, and the temporal scale of beach recovery.Subsequently, the paper brings together currently available approaches aimed at describing the effect of storm sequences on beach erosion in a general way.The importance of storm chronology and the effects of an extreme storm within a sequence of storms are highlighted.Following that, the more poorly studied aspect of beach recovery in between storms within a sequence is discussed.Three indicators for defining beach recovery, namely the shoreline location, sediment volumes, and the beach state, are identified and compared.Finally, important research needs, including the need for detailed physical modelling, are identified.
文摘River training walls have been built at scores of locations along the NSW coast and their impacts on shoreline change are still not fully understood. In this study, the Brunswick River entrance and adjacent beaches are selected for examination of the impact of the construction of major training walls. Thirteen sets of aerial photographs taken between 1947 and 1994 are used in a GIS approach to accurately determine the shoreline position, beach contours and sand volumes, and their changes in both time and space, and then to assess the contribution of both the structures and natural hydrodynamic conditions to large scale (years-decades and kilometres) beach changes. The impact of the training walls can be divided into four stages: natural conditions prior to their construction (pre 1959), major downdrift erosion and updrift accretion during and following the construction of the walls in 1959～1962 and 1966, diminishing impact of the walls between 1966 and 1987, and finally no apparent impact between 1987～1994. The impact extends horizontally about 8 km updrift and 17 km downdrift, and temporally up to 25 years.
文摘Studies on the erosion processes and protective measures at the downcoast of the Friendship Port in Mauritania have been successfully conducted by means of 3-D movable-bed model using light model-sand. The headland control was accepted for the stability of the beach. This paper mainly deals with the shape, orientation, size and erosion depth of the artificial headland. Various forms of headland projects, such as the normal groin, arch groins bending to upcoast ancj to downcoast, offshore breakwater, and T-shaped dike, have been experimentally investigated. Through a comparison of effects of these works on the beach processes, optimized headlands have been obtained, that is, unsymmetrical T-shaped dike or arch groin bending to the downcoast, which has been practically and successfully applied for the stability of beaches.
基金Supported by the Internal Grant of Universiti Malaysia Terengganu under the Translational Research Grant No.Vot 53464.
文摘Shoreline change analysis frequently begins with feature identification through visual interpretation(proxy-based shoreline)or the intersection of a specific tidal zone(datum-based shoreline).Using proxy-based shoreline information,this study quantifies the distance between proxy-based and datum-based shoreline data,which is defined as the proxydatum bias.The study was conducted at meso-tidal beaches in Kuala Nerus,Terengganu,Malaysia,with morphodynamic responses to northeast and southwest monsoons.The high-water line(HWL)shoreline(proxy-based)was determined using ortho-rectified aerial images captured by an unmanned aerial vehicle(UAV).By contrast,the mean high-water(MHW)shoreline(datum-based)was determined using measured beach profiles adjusted with the Peninsular Malaysia Geodetic Vertical Datum(DTGSM).The theoretical proxy-datum bias was approximated using the best estimate(median)for the beach slope,wave height,and wave period from the estimated total water level(TWL)model.Based on the study,the recorded horizontal proxy-datum bias for the research area was up to 32 m.This study also discovered that the theoretical assumption of the proxy-datum bias based on the TWL model yields values comparable to those of the measurements,with a narrower distinction in bias for steeper beach slopes than the obtained results.The determined proxydatum bias value can benefit future shoreline change studies as it could be incorporated to either proxy-based shorelines by shifting the shoreline seaward or to datum-based shorelines by shifting the shoreline landward in order of the bias value.The seasonal monsoon’s effect on beach profiles should be considered when calculating bias values and conducting potential shoreline change rate studies.
基金The China-Indonesia Marine and Climate Center Development under contract No.121152000000210003.
文摘Bathing beaches are usually the first to suffer disasters when tsunamis occur,owing to their proximity to the sea.Several large seismic fault zones are located off the coast of China.The impact of each tsunami scenario on Chinese bathing beaches is different.In this study,numerical models of the worst tsunami scenarios associated with seismic fault zones were considered to assess the tsunami hazard of bathing beaches in China.Numerical results show that tsunami waves from the Pacific Ocean could affect the East China Sea coast through gaps between the Ryukyu Islands.The Zhejiang and Shanghai coasts would be threatened by a tsunami from Ryukyu Trench,and the coasts of Hainan and Guangdong provinces would be threatened by a tsunami from the Manila Trench.The tsunami hazard associated with the Philippine Trench scenario needs particular attention.Owing to China’s offshore topography,the sequential order of tsunami arrival times to coastal provinces in several tsunami scenarios is almost the same.According to the tsunami hazard analysis results,Yalongwan Beach and eight other bathing beaches are at the highest hazard level.A high-resolution numerical calculation model was established to analyze the tsunami physical characteristics for the high-risk bathing beaches.To explore mitigating effects of a tsunami disaster,this study simulated tsunami propagation with the addition of seawalls.The experimental results show that the tsunami prevention seawalls constructed in an appropriate shallow water location have some effect on reducing tsunami hazard.Seawalls separated by a certain distance work even better.The analysis results can provide a scientific reference for subsequent preventive measures such as facility construction and evacuation.
基金This work is financially supported by the National Natural Science Foundation of China
文摘A numerical model of shoreline change of sand beaches based on long-term field wave data is proposed, the explicit and implicit finite difference forms of the model are described, and an application of the model is presented. Results of the application indicate that the model is sensitive to the order of the input wave data, and that the effects of long-term wave series and the effects of the mean annual wave conditions on the model are different. Instead of a single wave condition, the wave series will make the calibration and the verification of the model more practical and the results of the model more reasonable.
基金The National Natural Science Foundation of China under contract Nos 41930538,42076211 and 42076058the Scientific Research Foundation of the Third Institute of Oceanography,Ministry of Natural Resources under contract Nos 2022017 and 2019006the China Postdoctoral Science Foundation under contract No.2019M652248.
文摘The clay mineralogy of 28 sandy-muddy transitional beach(SMT-Beach)sediments and surrounding mountain river sediments along the coasts of southeastern China was systematically investigated to reveal the sediment source-to-sink process variations of such beaches and their morphological indications.The results show that the clay mineral assemblages of these SMT-Beaches mainly comprise of almost equal illite(~30%),kaolinite(~28%),chlorite(~22%),and smectite(~20%)contents.From the surrounding mountain rivers to the SMT-Beaches,clay mineral assemblages show distinct spatial changes characterized by a large decrease(~40%)in kaolinite,whereas the other three clay minerals present relative increases,especially clear for smectite.The muddy sediment sources of SMT-Beaches inferred from the clay mineralogy are mainly derived from nearby mountain rivers coupled with long-distance transport and penetration of the Changjiang River.The sandy sediments of these beaches are predominantly sourced from nearby mountain rivers,the weathering products of surrounding rocks in both mainland and island environments,and erosion of the“Old Red Sand”and“Red Soil Platform”.However,the sandy sediment sources of the SMT-Beaches are largely reduced because of the remarkable decrease in the river fluvial supply associated with intensive human activities such as dam construction and coastal reclamation.Subsequently,the sandy sections of SMT-Beaches present clear erosion and have revealed by both time series remote sensing images and a compilation of published literature.In contrast,the muddy sediment supply of SMT-Beaches is temporarily stable and relatively constant,resulting in the landward migration of the mudflats with relative transgression or accumulation.These findings highlight that the natural evolution processes of SMT-Beaches have been greatly reshaped by intensive human activities.
文摘A straightforward conceptual method is proposed to quantitatively assess the seasonal-scale tendency of retreatment or advancement on microtidal beaches by using the backshore/foreshore length ratio. This method is based on measuring the cross-shore profile of a beach when it passes through the “transitional state” that separates the high-from the low-energy season, period during which the morphological characteristics of the beach tend to its equilibrium profile. In order to obtain real measurements of backshore (B) and foreshore (F), the definition of the limits bounding these two important components in subaerial beaches is reviewed and discussed. The approach based on the measurement of the?B/F?length ratio assumes that foreshore and backshore have equivalent lengths in beaches that approximate to their state of morphodynamic equilibrium (B/F?~ 1). A backshore length exceeding the foreshore length is indicative of a state of beach recession, with a?B/F?length ratio > 1. When the foreshore length is greater than the backshore length, the shoreline is advancing or, alternatively, it is developing in a state of morphological confinement,?i.e.?due to the presence of a sea cliff, with a?B/F?< 1. This practical method is then tested against 36 sand and gravel microtidal beach profiles measured along the coasts of Basilicata, in southern Italy. The various “beach states” are summarised into seven classes (I-VII), each identified from specific value intervals of the?B/F?length ratio.
文摘The aim of this paper is to analyze volleyball practice in the beaches of Copacabana(Rio de Janeiro,Brazil)and Carcavelos and Cascais Bay(Cascais,Portugal)and to review the forms of appropriation of public space based on public policies and rules of the sport in question.Our methodology rests on bibliographic review and ethnographic research to map and distinguish the results in two spatial and cultural contexts that are considerably diverse.Results show that even with greater extension of Copacabana beach in comparison with Cascais,volleyball has a relevant impact in both areas.The installation of the necessary equipment for volleyball practice is also a form of impact in the landscape and establishment of territoriality,which is mainly activated when the game happens.
文摘In the paper, it is discussed reinforced coastal zones with resort-recreational functions, destructed in terms of anthropogenic pressure of the Black Sea, Georgia. Results of many years’ observations and researches prove low effectiveness of active methods of coastal protection, mostly causing and provoking intensive degradation of the beaches. Article highlights developing and constructing of free and unbounded beaches as an optimal coastal protection approach. Successful example of this approach was developing of coastal zone in 90s, in Gagra (West Georgia), Black Sea. Positive impact of this kind of artificial beach still survives. In the thesis, it is presented an attempt to scientifically prove extrapolation-traduction on the other similar coasts of the recovery of Gagra Zone beach. Based on morphodynamic analysis and comparison, according to the priorities of major features of reinforced coasts, it turned out that coast of three similar objects (Gagra, Ochamchire and Sokhumi) show homogenous aspects. Scientific expediency of providing extrapolation on other similar objects of etalon objects i.e. Gagra Beach recovered by successful coastal protection experiment. Thereby, for the purposes of creating free-artificial beach, choosing of wrecking zone of Ochamchire is based on coastal protection effectiveness and economical principals, including technical-economical effectiveness.
基金grateful to FAPEMIG,CNPq and CAPES for financial assistance.
文摘Using gamma-ray spectrometry, the activity concentration of naturally occurring radionuclides 226Ra, 212Pb, 214Pb, 232Th, and 40K was determined in sand beaches samples from different areas in Guarapari, Espírito Santo state, from Brazil. The absorbed dose rates and annual effective dose were calculated and the results were compared with the internationally accepted values as well as others high background radiation areas (HBRAs). The activity concentration of the 232Th in Areia Preta as well as the absorbed dose rates and annual effective dose were higher than the others regions compared. The results show that Areia Preta in Guarapari has higher background found in beaches in world. This work is part of a research project for the natural background determination of the Brazilian coast.
