Sand Barrier Research Articles

Dynamics of production and accumulation of phytolith assemblages in the Restinga of Maricá, Rio De Janeiro, Brazil

Abstract The Marica “restinga”, located on the eastern part of Rio de Janeiro State (Brazil), corresponds to one of the few remaining preserved areas of the state's coastal plain. This coastline presents two sand barriers separated by a depression where there is a freshwater swamp and different plant communities distributed in areas of high ecological diversity accompanying the local topography and the range of marine spray. This paper is a study of the soil phytolith assemblages in the Marica restinga, with the intent of establishing reference collections for paleoenvironmental studies of this coastal area during the Quaternary. Phytoliths were chosen as proxies, but their use for reconstruction of this type of vegetation is pioneer research, so it was essential to characterize the phytolith assemblages for each plant community through the identification of the main morphotypes and whether or not they are preserved in coastal depositional environments under the effect of geomorphology and salinity. Eight plant communities, distributed almost parallel to the coastline over sandy barriers, lagoonal plain, lagoon margin and weathered basement were identified: Halophile-psamophile, near the beach; two Scrub communities, one over the Holocene barrier and the other over the Pleistocene barrier; two Herbaceous swamps, one between the two sand barriers, the other behind the Pleistocene barrier; Slack, in front of the Pleistocene barrier; Shrubby vegetation on the shore of Marica lagoon and Dry forest, over the weathered Pre-Cambrian basement. In general, it was found that this type of environment is not very favorable for the formation and accumulation of phytoliths. Restinga plants did not prove to be large producers of phytoliths, except those known as such, as in the case of Poaceae and Cyperaceae. It was also observed that the permanence of phytoliths in sediments is strongly influenced by its particle size and organic matter content. The largest stocks of phytoliths were found in swamp communities, due to the presence of organic matter and low energy dynamics, and in dry forests, where a process of pedogenesis already occurs. Despite the low phytolith stocks present in modern assemblages, they show a high degree of conservation, which enabled significant results for the study of this type of vegetation. The calculated phytolith indices (tree density and water stress) consistently expressed, in detail, the environment of each community analyzed from the point of view of the type of vegetation cover and the conditions of water availability to plants.

Depositional facies and sequence of the latest Pleistocene to Holocene incised valley fill in Kushiro Plain, Hokkaido, northern Japan

The development of the latest Pleistocene to Holocene incised valley fill in the Kushiro area, Hokkaido, Japan is investigated in this study. Nine boring core samples drilled in the Kushiro marsh were examined using depositional facies analysis, total sulfur content (TSC) measurement, and radiocarbon dating methods. Based on these methods, 12 depositional facies were recognized including marsh, subaqueous talus, bay-head delta, sand dune, beach, shoreface, barrier sand body, drowned valley-central basin, salt marsh, fluvial, pond, and pyroclastic deposits. The incised valley fill forms a depositional sequence primarily controlled by glacio-eustatic sea-level changes. The lowstand systems tract is composed of river deposits. The transgressive systems tract includes salt marsh, drowned-valley fill central basin, bay-head delta, barrier sand body, central basin, and subaqueous talus deposits. The highstand systems tract is composed of barrier sand body, shoreface, beach, sand dune, central basin bay-head delta, marsh, salt marsh, subaqueous talus, fluvial, and pond facies. Radiocarbon dating analysis indicates that the period of maximum marine flooding was around 7 ka cal. BP.

Wave runup and overwash on a prototype-scale sand barrier

Accurate methods to predict wave runup are of critical importance to coastal engineers. Extreme runup during storm conditions can present a danger to coastal infrastructure and lead to dune overtopping and erosion, overwash of barrier beaches and is an essential design parameter for certain coastal protection works.This paper uses data obtained during the unique BARDEX II prototype-scale laboratory experiment on a reflective sand barrier to investigate wave runup and overwash. Runup measurements were acquired using ultrasonic altimeters, 2D scanning Lidar and camera systems under controlled wave and water level conditions.It was found that extreme runup (R2%) scaled well with the deepwater Irribarren number where the beach slope was taken to be the beach face gradient. The lower limit of the swash zone, defined by the 2% wave rundown limit was also found to be a function of the Irribarren number and was consistently below the SWL in all tests.The high resolution free-surface measurements obtained using the ultrasonic altimeters and Lidar enabled an analysis of the dynamics of individual swash events. It was found that the vertical runup excursion of each swash correlated strongly with the height of the bore at collapse, and could be predicted based on the assumption of a conversion of potential to kinetic energy at bore collapse.

Groundwater fluxes and flow paths within coastal barriers: Observations from a large-scale laboratory experiment (BARDEX II)

The dynamics of groundwater at the beach face land–ocean boundary have important implications to the exchange of water, nutrients, and pollutants between the ocean and coastal aquifers, and more subtly, varying groundwater levels may induce differing morphological response at the beach face. As a component of the multi-institution Barrier Dynamics Experiment (BARDEX II), groundwater fluxes and flow paths within a prototype-scale sandy barrier are quantified and reported at the three fundamental spatio-temporal scales (individual waves, the beach face, and total barrier), under controlled wave and water level conditions. A particular feature of the experimental programme was the inclusion of a back-barrier ‘lagoon’, that via a pump system and an intermediate water reservoir enabled the forcing of contrasting hydraulic gradients across the barrier. It was observed that the groundwater level, flow paths, and fluxes within the beach face region of the sand barrier were predominantly controlled by the action of waves at the beach face, regardless of the overall seaward- or landward-directed barrier-scale hydraulic gradients. In the presence of waves, all tests undertaken to complete this study developed a seaward gradient in this zone under the influence of waves. As a further result of wave forcing at the beach face boundary, localised groundwater flow divides were observed to develop, further partitioning the circulation and flow paths of groundwater within the prototype-scale sand barrier.

Shoreline change and sea level rise at the Muni-Pomadze coastal wetland (Ramsar site), Ghana

Lagoon-wetland systems are common along low-lying coastlines. They provide rich species habitats, multiple ecosystem services and socio-economic activities. They are particularly susceptible to the impacts of sea level rise (SLR), especially in less developed countries (LDCs) where economic and development constraints limit adaptation. The Muni-Pomadze lagoon is one of five coastal Ramsar sites in Ghana and one of many along the country’s coastline. It is an intermittently closed lagoon with extreme seasonal hydrological and physico-chemical variation. Field observation, digital mapping and GIS analysis of the shoreline has enabled an understanding of coastal change and SLR at the lagoon. From 1972 to 2014 the high water mark has shifted landwards with an average retreat rate of 0.22 m/year. Evidence of erosion and sediment washover indicate loss of and a shift landward of the sand barrier separating the lagoon from the ocean. Creation of an inundation map for a one-meter rise of sea level reveals fragementation and breaching of the barrier and an increasingly permanent connection to the ocean. A more open lagoon system stabilises hydrological and physico-chemical conditions, leading to increases in biodiversity and aquatic productivity. The lagoon currently has no consideration of SLR in its management plan. The results of this analysis and the limited development of the Muni-Pomadze lagoon support a no intervention approach to coastal management that allows SLR to transform the closed lagoon to an open estuary. A similar approach at comparable coastal wetland systems in Ghana and in other LDCs could prove an effective management option.

La ocupación del litoral onubense en época romana y su relación con eventos marinos de alta energía.

Las investigaciones geomorfológicas y arqueológicas que actualmente se están desarrollando en el Paraje Natural Marismas del Odiel - reserva de la Biosfera por la UNESCO-, especialmente en el cordón arenoso de La Cascajera, han ofrecido interesantes resultados que permiten retomar los estudios sobre la ocupación del litoral onubense en época romana desde un punto de vista diacrónico en el tránsito del bajo imperio hacia la tardoantigüedad. A este respecto son numerosas las factorías pesqueras (cetariae) que jalonan la costa más occidental de la antigua Provincia Baetica y en las cuales, ahora tras un proceso de revisión, se pueden intuir o comprobar momentos de ruptura y recuperación en sus explotaciones que habría que poner en relación con eventos marinos catastróficos (EWE) que, de manera histórica, han afectado a estas costas.

Decadal evolution of a spit in the Baram river mouth in eastern Malaysia

We studied a newly formed spit in the Baram River mouth in Eastern Malaysia and evaluated the effects of climatic conditions and human interference over the last four decades (1974–2014). The development of a spit during a decade (1998–2008) and its maximum expansion over the period 2005–2010 is related to the erosion associated with deforestation and land use changes in the upstream region. The downstream transportation of the heavy sediment load occurred during the events of higher precipitation and flash floods. The recent spit was identified for the first time as a mud flat post the flash flooding of January 2005. It extended towards the south west of the river mouth till 2010 (six fold increase in area from 2005 to 0.29km2) and gradually disintegrated over the next 3 years. Depositional feature of coarse sediments and organic debris is clearly supported by the alternating thick layers in the top 25cm of the three core samples (C1–C3) collected from the region. The non-existence of finer particles clearly indicates the supremacy of long shore currents in the region carrying away the fines to deeper regions. Gradual disappearance of the sand barrier post 2011 is due to the reduction in the amount of sediment load as a result of reduction in recent rainfall activity, land use/land cover changes mainly as reforestation, strengthening of palm plantation (controlling soil erosion in the river banks) in the upstream region. The dominant NW wind direction during the major part of the year is also one of the factors for the shift in depositional sequence and it is helped by the long shore currents which lead to the spit being partially connected to the main land.

Multi-scale monitoring of landscape change after the 2011 tsunami

Abstract. The Great East Japan Earthquake (magnitude 9.0; occurred on 11th March 2011) and subsequent huge tsunami caused widespread damage along the Pacific Ocean coast of eastern Honshu, Japan. This research utilizes multi-resolution remote sensing images to clarify the impact on landscapes caused by this disaster, and also to monitor the subsequent survival and recovery process in the Sendai Bay region. The coastal landscape in the target area features a narrow strip of coastal sand barrier, historically stabilized by planted pine groves; backed by a low-lying plain that has traditionally been diked and converted to irrigated rice paddies. Farmsteads on the flat alluvial plain are surrounded by groves called “Igune”, consisting primarily of conifers. MODIS data (250 m resolution) were employed to map the overall extent of inundation and damage on the regional landscape scale. The major damage caused by the tsunami, destruction of coastal pine forests and inundation or rice paddies on the plain, was identified at this level. Progressively finer scale analysis were then implemented using SPOT/HRG-2 (10 m resolution) data; GeoEye-1 fine resolution data (0.5 m) and very fine resolution aerial photographs (10 cm) and LiDAR. These results demonstrated the minute details of the damage and recovery process. Some patches of pine forest, for example, were seen to have survived, and some coastal plant communities were already recovering only a year after the disaster. Continuous monitoring using field work and remote sensing is required for balanced regional strategies that provide for economic and social recovery and as well as restoration of vegetation, biodiversity and vital ecosystem services.

Attaining provenance proxies from OSL and TL sensitivities: Coupling with grain size and heavy minerals data from southern Brazilian coastal sediments

In the São Francisco do Sul (SFS) barrier in southern Brazil, the optically stimulated luminescence (OSL) and thermoluminescence (TL) sensitivities of coastal sands vary according to geomorphological units. Sands from older beach ridges (ages older than 2000 years ago) show higher OSL and TL sensitivities than younger units (ages younger than 2000 years). Geomorphological units in the SFS attest to changes in provenance as a result of a coastal climate shift evidenced through grain size and heavy mineral analysis. We argue that in the SFS barrier sands, OSL and TL sensitivity signals provide an additional proxy to climate events and can be used as an alternative method to assess changes in provenance and tracking source-to-sink systems to monitor past and future environmental changes.

Re-framing values for a World Heritage future: what type of icon will K'gari-Fraser Island become?

K’gari-Fraser Island, the world's largest barrier sand island, is at the crossroads of World Heritage status, due to destructive environmental use in concert with climate change. Will K’gari-Fraser Island exemplify innovative, adaptive management or become just another degraded recreational facility? We synthesize the likely impact of human pressures and predicted consequences on the values of this island. World-renown natural beauty and ongoing biological and geological processes in coastal, wetland, heathland and rainforest environments, all contribute to its World Heritage status. The impact of hundreds of thousands of annual visitors is increasing on the island's biodiversity, cultural connections, ecological functions and environmental values. Maintaining World Heritage values will necessitate the re-framing of values to integrate socioeconomic factors in management and reduce extractive forms of tourism. Environmentally sound, systematic conservation planning that achieves social equity is urgently needed to rectify historical mistakes and update current management practices. Characterizing and sustaining biological refugia will be important to retain biodiversity in areas that are less visited. The development of a coherent approach to interpretation concerning history, access and values is required to encourage a more sympathetic use of this World Heritage environment. Alternatively, ongoing attrition of the islands values by increased levels of destructive use is inevitable.

Discussion of “Physical and numerical study of lateral diversion by three-layer inclined capillary barrier covers under humid climatic conditions”

The authors investigated the performance of an inclined threelayer cover with capillary barrier effect (CCBE) system comprising silt, sand, and gravel, subjected to a continuous heavy rainfall (Zhan et al. 2014). They compared numerical results and analytical solutions with respect to effective length of lateral diversion of the inclined three-layer CCBE system. The comparison indicated that the analytical solution proposed by Stormont (1996) is relatively conservative. It should be noted that Stormont’s (1996) analytical solution is only applicable to a two-layer CCBE system. In the discussers’ opinion, this analytical solution should be modified to consider capillary effects contributed by both the upper two layers (i.e., silt–sand) and lower two layers (i.e., sand–gravel) in the three-layer CCBE system. The three-layer (silt—sand–gravel) CCBE system investigated by the authors can be simplified as the sum of silt–sand and sandgravel capillary barriers, as shown in Fig. D1. The infiltrated rainwater is first drained laterally along the silt–sand interface to the tip point at which the hydraulic conductivity of the sand layer is equal to that of the silt layer. Subsequently, rainwater flows into the sand layer and is drained laterally along the sand–gravel interface to the tip point at which the hydraulic conductivity of the gravel layer is equal to that of the sand layer. The lateral diversion length of the three-layer CCBE system, Lthree-layer, should be calculated as

Characteristics of erosion and deposition of straw checkerboard barriers in alpine sandy land

The morphology and stability of concave surface of the straw checkerboard barriers are the fundamental guiding principles of exploring the mechanism of erosion and deposition, evaluating effectiveness and life period, and optimizing the physical structures of the sand barriers. Especially, in alpine sandy land, characteristics of erosion (deposition) and capacity for anti-erosion and sand burial of straw checkerboard barriers are significantly different from the arid and semi-arid desert regions. Erosion (deposition) measurements and wind–sand observations for different specifications (1 m × 1 m, 1.5 m × 1.5 m and 2 m × 2 m) and slope positions (toe, middle and top of the windward areas) of wheat straw checkerboard barriers were adopted in the eastern shore of the Qinghai Lake study area. The different sizes of straw checkerboards at different windward areas have distinctly erosive and depositional stability and intensity. Including the checkerboards with 1.5 m × 1.5 m (medium) size at the middle and top, 1 m × 1 m (small) size at the top and 2 m × 2 m (large) size at the toe, all the erosion (deposition) coefficients are between 0.09 and 0.11, while their intensities of accumulation are relatively steady (70–90 kg m−2), which are the easiest to form stable concaves, and the heights of the barriers change least. Nevertheless, the concaves with small size at the toe are seriously buried, but eroded in the center of some checkerboards with large size at the top, which lead to a short protective period within 3 years and an unbalance between erosion and deposition. Moreover, the transects of erosion (deposition) dominated by southwesterly and northwesterly winds reflect the different intensities of erosion (deposition) at various orientations. On the transect of the NW–SE orientation, at the dune section, each square in the NW direction is strongly accumulated, and the center–SE azimuth is weakly eroded. Usually, deeper accumulation in the center of transects happen in those checkerboards with smaller size and lower terrain slope, which is mainly caused by an obviously positive correlation between the northwest and southwest wind velocity and the erosive depth, and the same is true with the wind frequency (all correlation coefficients are between 0.85 and 0.95). Taking the characteristics of erosion (deposition), sand protection benefits and costs of all types into account, large size at the toe and medium size at the middle of windward slope are the most practical combinations, while small size is suitable to play an emergency treatment role in some extremely serious hazard areas in alpine sandy land.

ANewMethod forZoning ofCoastalBarriersbased onHydro-geomorphological andClimateCriteria

This paper presents a new methodology for the zoning of littoral sand barriers on the basis oftheir groundwater dynamic responses to the local mean water level (MWL) climate. The method is based onthe comparison of the characteristic scales of the horizontal drainage and recharge processes. Using theBoussinesq equation and basic hydro-geomorphological parameters, this methodology identifies the climaticevents that markedly affect the groundwater dynamics across the barrier, along with the location of the mostaffected cross sections. The application of the methodology to the Mar Menor sand barrier shows that asignificant number of cross sections can be particularly vulnerable to the effects of local storm events typicalof the Mediterranean coast during the spring and winter seasons. The location of the affected cross sections isanalyzed as a function of both the local MWL forcing and hydrogeological parameters. This case studyhighlights the possible use of the proposed methodology for land use planning and the environmentalmanagementof coastal sand bars.

Water relations of wallum species in contrasting groundwater habitats of Pleistocene beach ridge barriers on the lower north coast of New South Wales, Australia

This study examined the water relations of sclerophyllous evergreen vegetation (wallum) on coastal sand barriers in eastern Australia. Many wallum species may be groundwater dependent, although the extent of this dependency is largely unknown. Twenty-six perennial tree, shrub and herb species were investigated in three groundwater habitats (ridge, open depression, closed depression). Pre-dawn and midday shoot xylem water potentials (ψx) were measured monthly between late autumn 2010 and late summer 2011. Pressure–volume curve traits were determined in mid- to late spring 2009, including the osmotic potential at full (π100) and zero (π0) turgor, and bulk modulus of elasticity (ε). Carbon isotope ratios (δ13C) were also determined in mid- to late spring 2009, to measure water-use efficiency (WUE). The species displayed a range of physiological strategies in response to water relations, and these strategies overlapped among contrasting growth forms and habitats. Linear relationships between osmotic and elastic adjustment were significant. A strong correlation between δ13C and distribution along the hydrological gradient was not apparent. Banksia ericifolia subsp. macrantha (A.S.George) A.S.George, Eucalyptus racemosa Cav. subsp. racemosa and Eucalyptus robusta Sm. displayed little seasonal variation in ψx and maintained a comparatively high pre-dawn ψx, and are therefore likely to be phreatophytic. Wetland vegetation in the lowest part of the landscape appeared to tolerate extreme fluctuations in water availability linked to a prevailing climatic pattern of variable and unreliable seasonal rainfall.

Volución morfológica de la espiga de Galerazamba, Caribe colombiano

In order to analyze the Galerazamba spit morphological evolution as well as its barrier systems classification; we analyzed us historical shoreline records and currents patterns according historical changes from 1948 until 2014. It was established that the first morphological shape corresponding the Magdalena river channeling in 1936 and the mud volcano eruption over the spit in 1938 is a Fly Spit. After the eruption, the lack of sediment in the system due to the river channeling was evident the sediment readjustment parallel to Galerazamba s shoreline, generating several sand barriers types over time due to littoral drift and local sediment supplies, moring towards its present morfology which corresponds to a closed sand bar called Bay-mouth Barrier.

Numerical study on the effect of semi-buried straw checkerboard sand barriers belt on the wind speed

Abstract In this paper, the spatial variation of wind speed along a straw checkerboard barriers belt and the effect of size and characteristic of the straw checkerboard on the wind speed were studied by computational fluid dynamics. Our results show that the spatial variation of wind speed along a straw checkerboard sand barriers belt can be divided into three stages, i.e., descent stage, stable stage and recovery stage, and the variation of wind speed with height satisfy three different log-linear functions, i.e., the log-linear function below the straw height, the log-linear function between the straw height and the critical height, and the log-linear function above the critical height. The straw height and the leaf area density have obvious influence on the spatial variation of wind speed. And we firstly gave formulas to describe the variation of near-surface wind velocity which had considered the influence of the size and the leaf area density of straw checkerboard barriers. Furthermore, the prediction formula of sand transport rate above straw checkerboard was given based on the ratio of near-surface wind speed and the incoming wind speed. According to these formulas, we can predict the lifetime of the straw checkerboard barriers belt and give optimal design on how to pave straw checkerboard.

TYPHOONS DRIVEN MORPHODYNAMICS OF THE WAN-TZU-LIAO SAND BARRIER (TAÏWAN)

This study focuses on the dynamics of the Wan-Tzu-Liao sand barrier when it is struck by one typhoon, a group of typhoons or the whole season of typhoons and monsoon. In the framework of the KUN-SHEN project, 7 months of monitoring (2011-2012) provided 20 topobathymetric surveys (within a 200 m long segment of the barrier from the subtidal zone to the back-barrier) and acquisitions of offshore, nearshore and shallow water hydrodynamics including velocity profiling, free surface measurement and absolute pressure. Offshore waves were extracted at Cigu buoy (18 m of water depth). Nearshore waves were acquired from the current profiler deployed 400 m off the coast in 4 m of water depth and water level on the subaerial beach were acquired from two pressure sensors deployed in the lower part of the subtidal zone and the dune crest. Morphologic changes of the emerged beach were monitored using D-GPS each week during winter monsoon season and just before and after each event during summer typhoons season. Amongst the eight studied typhoons, TALIM is the most energetic event observed. Offshore wave height reached H s = 10.34 m (T p = 14.6 s) at Cigu buoy and H s = 2.3 m (T p = 13.4 s) at the profiler. Surface waves dynamics throughout surf and swash zones are progressively dominated by infragravity motions. A part of the dune is surged at the storm apex. Morphological changes include 6.7 m of dunefoot retreat and a sand transfer from a dune breach to wash-over deposits in the lagoon. More surprisingly, the foreshore was nourished (2261 m3 +/- 268 m3 ) as well as the whole sand barrier (+1920 m3 +/- 1071 m3 ). The sand input is concomitant to the redistribution of sand from the intertidal sandbars interpreted as the ultimate stage of the subtidal bars landward migration. Although winter are erosive season (-4995 m3 +/- 1071 m3 ), the summer results in an accretion period (3556 m3 +/-1071 m3 ) with a shoreline seaward shift about 10.4 m. Over the annual time period, the sand barrier recorded 18.4 m of retreat coupled with a small sand loss (-1439 m3 +/- 1071 m3 ) without any significant abrasion of the dune-top.

REALISTIC SIMULATION OF INSTANTANEOUS NEARSHORE WATER LEVELS DURING TYPHOONS

3D hydrodynamic simulations were performed on an area extending 600 km off Taiwan island for the period running from September 2011 to December 2012. We covered a winter Monsoon season and a summer season with 17 typhoons recorded. By comparing simulations and measurements during the TALIM typhoon, our model reproduces correctly the storm surge observed along the Wan-Tzu-Liao sand barrier (South-West Taiwan). By a modelling approach, we analyzed the regional hydrodynamic mechanisms which control the sea surface elevation at the Chung-Chin harbour. Tide is the dominant forcing of the water level with more than 1 meter above the mean sea level. Global currents contribute up to 80 cm to the water level but during the SAOLA typhon, the elevation reached 1 meter. The contribution of atmospheric forcings is lower but it can generate 30 cm of elevation (e.g. during GUCHOL and TALIM typhoons)

Early Silurian paleogeography and source-reservoir-cap rocks of the Middle-Upper Yangtze region in South China

The lithofacies paleogeography for the three successive ages (Rhuddanian, Aeronian and Telychian) in the Middle-Upper Yangtze region of South China in the Early Silurian (Llandoverian Epoch) is reconstructed according to the concept that structures control a basin, a basin controls facies, which, in turn, control the basic geology of oil and gas. The time-space distribution and sedimentology of source-reservoir-cap rocks are summarized. In the Rhuddanian age, the study area inherited and developed a semi-confinement stagnant basin resulting from tectonic compression started on Late Ordovician. The widely-covered organic-rich muddy shales occurred on deep-water shelves in a global-scale transgression after the Hirnantian glaciation and subsequent relatively slow regression. The sagged areas, formed mainly by tectonic tilting and plugging effect of rigid continental nucleus, are sedimentary centers of favorable source rocks. At the intermittent stage of tectonic compression during the Aeronian age, a mix-sedimented “carbonate ramp” formed by global sea-level drop, warm-humid climate and slight clastic sources. The reef-bank type carbonate reservoir rocks within Shiniulan Formation occurred in subtidal high-energy environments within inner ramp. In the subsequent Telychian stage, tectonic compression intensified, resulting in regression and overall uplifting of the basin, terminated the development of carbonate depositional environments. The eastern region was then dominated by shoreface and tide-dominated deltas where sand barrier type reservoir rocks in the Xiaoheba Formation occurred. The widespread muddy sediments of the Hanjiadian Formation could be cap rocks for the underlying potential oil-bearing layers.

Experimental and Numerical Simulation on Hexavalent Chromium Migration Characteristics by Permeable Fine-Grained Sand Barrier Filters

AbstractThe presence of toxic hexavalent chromium poses a great challenge in the wastewater pretreatment of agricultural irrigation. The feasibility of using fine-grained sands as suitable filling materials in the permeable barrier filter was studied for the effective containment of hexavalent chromium. Based on the governing equations representing seepage-field coupled concentration-field, a physical model composed of the fine-grained sands ranging from 0.075–0.5 mm was tentatively designed to remove hexavalent chromium in the permeable barrier filters. The column physical model experiments of 0.5, 0.2, 0.1, and 0.075-mm sands were separately performed under low velocity of 14.92 cm day−1, moderate velocity of 29.84 cm day−1, and high velocity of 44.76 cm day−1. The results were verified by numerical simulations under the corresponding experimental condition. According to the removal efficiency and hydraulic retention time of each sand model, 0.5, 0.2, and 0.1-mm sands were chosen as ideal materials t...