Active Sand Research Articles

Cooperative biodegradation of geosmin by a consortium comprising three gram-negative bacteria isolated from the biofilm of a sand filter column

To isolate and identify bacteria from a sand filter column capable of degrading the taste and odour compound, geosmin. In doing so, to investigate if these organisms degrade geosmin either individually or if an alternative mechanism is utilized. Geosmin-degrading bacteria from a biologically active sand filter column were enriched by their growth in a minimal medium supplemented with geosmin as the sole carbon source. By day 51, 21.7 mg l(-1) of geosmin had been degraded as determined by solid-phase microextraction gas chromatography/mass spectrometry, and was accompanied by a 2.12 log(10) increase in active bacterial numbers as measured using the BacLight(TM) bacterial viability kit and flow cytometric enumeration. During the onset of geosmin degradation, the predominance of three bacteria, most similar to previously cultured species of Sphingopyxis alaskensis, Novosphingobium stygiae and Pseudomonas veronii based on 16S rRNA gene sequences was detected by denaturing gradient gel electrophoresis. Subsequent isolation of these organisms revealed that degradation of geosmin, when present as either the sole carbon source (ranging from 40 ng l(-1) to 20 mg l(-1)) or when spiked into sterile reservoir water (37 and 131 ng l(-1)), occurred only when all three isolates were present. None of the isolates was shown to be capable of degrading geosmin either individually or in any combination of two. This study has reported, for the first time, the cooperative degradation of geosmin by a consortium comprising three gram-negative bacteria isolated from a biologically active sand filter column. These results are important for researchers currently employing molecular-based approaches to further understand the biodegradation of geosmin by bacteria, as such studies may be complicated by the discovery of geosmin degradation occurring by a consortium. This study also advances the knowledge surrounding the types of bacteria capable of degrading the taste and odour compound, as investigations to date regarding this are limited.

A Conservation Evaluation of Smooth Goosefoot, Chenopodium subglabrum (Chenopodiaceae), in Canada

Smooth Goosefoot (Chenopodium subglabrum) is restricted to North America and reaches its northern distribution limit in Alberta, Saskatchewan and Manitoba. The habitat of Chenopodium subglabrum contains some element of active sand. It is commonly found on the stabilizing edges of active dunes as well as dune blowouts, and occasionally on bare or recently disturbed sand plains. Chenopodium subglabrum is a sexually reproducing annual species with seeds that may remain in the seed bank for several years, waiting for the conditions it favours for germination. Germination of this species is erratic, possibly in response to moisture, making the overall population trend difficult to determine. The estimated population in Canada is likely between 5000 and 10000 individuals. There has been considerable loss of habitat as dunes become vegetated. The processes of dune stabilization and fire control threaten survival of this species.

Fluvial Sand Sources for Barrier Island Restoration in Louisiana: Geotechnical Investigations in the Mississippi River

Abstract Coastal land loss in the Mississippi River delta region, related to degradation of wetlands and erosion of barrier islands, contributes to loss of valuable habitat, endangerment of infrastructure and socioeconomic systems, and coastal flooding hazards. Restoration of these ecosystems is thus a primary activity that requires large volumes of sand to rebuild beach–dune systems and restore wetland habitats. Sand sources have traditionally been sought offshore in the marine environment, but there are problems associated with setbacks from oil and gas infrastructure, presence of muddy overburden, and limited reserves of beach-quality sediments. Fluvial sand sources in channel and point-bar deposits become an attractive alternative for barrier island restoration because of large volumes of relict deposits and because active sand waves are renewable. Results of preliminary geophysical and geotechnical investigations in the lower Mississippi River (south of New Orleans) along a 32-km stretch of the river...

Wind Characteristics of Mesquite Streets in the Northern Chihuahuan Desert, New Mexico, USA

Past research has shown that the most important areas for active sand movement in the northern part of the Chihuahuan Desert are mesquite-dominated desert ecosystems possessing sandy soil texture. The most active sand movement in the mesquite-dominated ecosystems has been shown to take place on elongated bare soil patches referred to as “streets”. Aerodynamic properties of mesquite streets eroded by wind should be included in explaining how mesquite streets are more emissive sand sources than surrounding desert land. To understand the effects of wind properties, we measured them at two flat mesquite sites having highly similar soil textures but very different configurations of mesquite. The differences in wind properties at the two sites were caused by differences of size, orientation, and porosity of the mesquite, along with the presence of mesquite coppice dunes (sand dunes stabilized by mesquites growing in the dune and on its surface) found only at one of the two sites. Wind direction, u * (friction velocity), z 0 (aerodynamic roughness height) and D (zero plane displacement height) were estimated for 15-m tower and 3-m mast data. These aerodynamic data allowed us to distinguish five categories with differing potentials for sediment transport. Sediment transport for the five categories varied from unrestricted, free transport to virtually no transport caused by vegetation protection from wind forces. In addition, “steering” of winds below the level of the tops of mesquite bushes and coppice dunes allowed longer parallel wind durations and increased wind erosion for streets that aligned roughly SW–NE.

The Hot Tubb Folsom-Midland Site (41CR 10), Texas

The Hot Tubb site, located in the Monahans Dunes just off the southern High Plains of west Texas, has yielded Folsom and Midland projectile points, as well as badly fragmented and occasionally burned remains of Bison antiquus. Because these materials occur primarily on the surface of a deflation basin within an active sand dune, which also contains artifacts of later age, the Paleoindian component cannot be easily isolated, nor have attempts to determine its radiocarbon age been successful. Nonetheless, the distribution and density of the bone and diagnostic Folsom material indicate there is spatialandpossibly stratigraphic integrity to this component, which makes it possible to discern where and what Paleoindian activity may have occurred on site.We infer this was a small Folsom-age bison kill and processing locality of an estimated six animals. The lithic assemblage is marked by intensive reworking and even refluting of projectile points, suggesting that the supply of stone, originally acquired at sources at least 150 km distant, was low by the time of this occupation. That dearth of stone, the presence of Midland points, as well as a possible Midland point preform, may also shed some light on the longstanding ‘Folsom-Midland Problem.’

Bacterial degradation of microcystin toxins within a biologically active sand filter

Microcystin toxins are a problem for water authorities as they are recalcitrant to conventional water treatment. In this study, biological sand filtration was assessed in laboratory column experiments for its ability to remove two microcystin analogues, microcystin-LR and microcystin-LA. A lag period of 3 days was evident prior to the commencement of degradation. Contact times were varied during the experiment; however, no microcystin was detected in the effluent after 4 days, even under conditions similar to those of a rapid sand filter. Removals of microcystin through the sand filters were shown to be primarily through biological degradation processes. Using polymerase chain reaction (PCR), biofilm, extracted from one of the sand filters that had effectively removed the microcystins, was shown to contain bacteria with the mlrA gene. Detection of this gene provided additional evidence that biological degradation of microcystin was the primary removal mechanism.

RIVERBED VARIATION AND CHANGE OF BED MATERIAL IN THE BRANTAS RIVER AFTER AN ERUPTION OF MT. KELUD

So far huge sediment production due to the eruption of Mt.Kelud has given serious damage to the Brantas river basin. On the other hand the eruption has provided soil and sand for agricultural land and construction material. So, as a first step to establishing an advanced control system both of the sediment runoff and the sediment utilization, we have investigated the change of sediment transport properties after the eruption in 1990. The field survey result shows that the sever sediment deposition occurred immediately after the eruption, but 1 year after the eruption the bed aggradation changed into the bed degradation because of active sand mining. Also we obtained the sediment supply condition at the confluences with the tributaries after the eruption and presented a way to estimate the condition. Furthermore the field observation result on wash load indicates the wash load transport rate decreased rapidly after the eruption.

Seawall Impacts on Adjacent Beaches: Separating Fact from Fiction

The common perception in the US that seawalls ...increase erosion and destroy the is examined by summarizing available field data including our own research efforts at Sandbridge, Virginia, beginning in 1990. Sand trapped behind seawalls is remove from the system, but is a relatively small fraction of the active sand volume across the entire profile to closure depth. End-of-wall or flanking effects may not be due to sand trapping but other mechanisms such as interior drainage, rip current formation, groin effect, and the seawall/adjacent beach system acting as a rocky headland/parabolic-shaped beach system. Suggestions are made for when seawalls are appropriate and when they are not, including methods to mitigate downdrift impacts, if appropriate. Many misconceptions, false assumptions and misleading statements have been made in the US literature. This paper begins to separate fact from fiction.

Laboratory studies to characterize the efficacy of sand capping a coal tar-contaminated sediment

Placement of a microbial active sand cap on a coal tar-contaminated river sediment has been suggested as a cost effective remediation strategy. This approach assumes that the flux of contaminants from the sediment is sufficiently balanced by oxygen and nutrient fluxes into the sand layer such that microbial activity will reduce contaminant concentrations within the new benthic zone and reduce the contaminant flux to the water column. The dynamics of such a system were evaluated using batch and column studies with microbial communities from tar-contaminated sediment under different aeration and nutrient inputs. In a 30-d batch degradation study on aqueous extracts of coal tar sediment, oxygen and nutrient concentrations were found to be key parameters controlling the degradation rates of polycyclic aromatic hydrocarbons (PAHs). For the five PAHs monitored (naphthalene, fluorene, phenanthrene, anthracene, and pyrene), degradation rates were inversely proportional to molecular size. For the column studies, where three columns were packed with a 20-cm sand layer on the top of a 5 cm of sediment layer, flow was established to sand layers with (1) aerated water, (2) N 2 sparged water, or (3) HgCl 2-sterilized N 2 sparged water. After steady-state conditions, PAH concentrations in effluents were the lowest in the aerated column, except for pyrene, whose concentration was invariant with all effluents. These laboratory scale studies support that if sufficient aeration can be achieved in the field through either active and passive means, the resulting microbially active sand layer can improve the water quality of the benthic zone and reduce the flux of many, but not all, PAHs to the water column.

The Effect of Biological Soil Crusts on Throughput of Rainwater and N into Lake Michigan Sand Dune Soils

Biological soil crusts composed of cyanobacteria, green algae, bryophytes, and lichens colonize soils in arid and semiarid ecosystems worldwide and are responsible for significant N input to the soils of these ecosystems. Soil crusts also colonize active sand dunes in more humid regions, but studies of structure and function of such sand dune crusts are lacking. We identified the cyanobacterial, algal, and bryophytic constituents and N production and leachates of biological soil crusts that colonize beach dunes at the Indiana Dunes National Lakeshore along southern Lake Michigan in Indiana, USA. To determine the role of these crusts in this system, we conducted a greenhouse experiment in which intact soil cores with biological crusts were subjected to artificial rainfall over a full growing season. The volume and N content of leachate from the cores were quantified in relation to degree of crust development, taxonomic composition, rainfall volume and intensity, light intensity, and the presence of plant litter. Net N throughput significantly exceeded N inputs to cores in rainwater. Net N outputs from crusts to subsurface soil ranged from 0. 01 to 0.19 g NH 4 + -N m−2 yr−1 and 0.01 to 0.61 g NO 3 – N m−2 yr−1. Thus, total inorganic N inputs associated with biological soil crusts ranged from 0.02 g N m−2 yr−1 to 0.8 g N m−2 yr−1. High volume (≥2 cm) rainfall resulted in more N leaching than low volume events, and plant litter added over the surface of crusted soil cores significantly increased the amount of N in leachate. Exploratory path analysis revealed direct and indirect linkages among environmental factors, crust development, and crust composition in regulating the throughput of H2O and N from these intact soil cores. Biological soil crusts at this site, combined with other properties of the soil surface, substantially increase N inputs to this water- and nutrient-limited sand dune ecosystem.

Structure, Pattern and Mechanisms of Formation of Seed Banks in Sand Dune Systems in Northeastern Inner Mongolia, China

A comparison of structure and pattern of the soil seed bank was made between active and stabilized sand dunes in northeastern Inner Mongolia, China. The objective of this paper was to determine the significance of seed bank in vegetation restoration of sand dunes. The results showed that (1) average seed density decreased from stabilized sand dune to interdune lowland of stabilized sand dune, to interdune lowland of active sand dune, and to active sand dune; (2) horizontally, along the transect from interdune lowland to ecotone and to sand dune top, a ‘V’ shaped pattern was presented in the active dune system, and a reverse ‘V’ shaped pattern in the stabilized sand dune system; (3) vertically, the proportion (accounting for the total seeds) of seeds found in 0–20 mm soil profile decreased from stabilized sand dune to interdune lowland of stabilized sand dune, to interdune lowland of active sand dune, and to active sand dune. The same order was also found in 20–50 mm and 50–100 mm soil profiles; (4) the Sokal and Sneath similarity indices in the species-composition between soil seed bank and above-ground vegetation were ranked as: the stabilized sand dune (24%) > the interdune lowland of active sand dune (21%) > the interdune lowland of stabilized sand dune (18%) > the active sand dune (5%); and (5) vegetation restoration of active sand dunes depends on the dispersal of seeds from nearby plant communities on the interdune lowlands. Much effort must be made to preserve the lowlands, as lowlands are the most important seed reservoir in the active sand dune field.

On the sand surface stability in the southern part of Gurbantünggüt Desert

Longitudinal dunes are the most widespread dune types in the world sand seas but comprehensive study on the sand surface stability is scarce. The southern part of Gurbantunggut Desert is mainly covered by longitudinal dune in which fixed and semi-fixed dunes occupy over 80% of the total area. Systematic analysis on the climatic conditions, the soil moisture and vegetation distributions, and the sand surface activities showed that the fixed and semi-fixed dunes are in a comprehensive low-energy wind environment. Snow cover and frozen soil provide a good protection to the ground surface in winter. The temporal distribution of precipitation and corresponding variation of temperature create a favorable condition for the desert plants growth, especially for the ephemeral plants. The occurrence of effective winds for sand moving in April to June coincides with the stage of relatively wet sand surface and good vegetation cover, which effectively keep the sand surface stable at the interdune and the plinth of the dunes. Activity sand surface appears only at the crest and the upper part of the sand dunes.

Plant Responses to an Edaphic Gradient across an Active Sand Dune/Desert Boundary in the Great Basin Desert

In arid ecosystems, variation in precipitation causes broad‐scale spatial heterogeneity in soil moisture, but differences in soil texture, development, and plant cover can also create substantial local soil moisture heterogeneity. The boundary between inland desert sand dunes and adjacent desert habitats exhibits abrupt changes in soil and vegetation characteristics that may be associated with differences in plant‐available water and nutrients. We hypothesized that differences in plant water status between habitats would mirror changes in soil texture and vegetation cover. Because the dunes have higher water availability, we predicted that plants on dunes would have higher plant water potential (Ψ) and be less water use efficient than plants off dunes. We tested these predictions for three species—Psoralidium lanceolatum (a C3 perennial N‐fixing subshrub), Stipa hymenoides (a C3 perennial bunchgrass), and Salsola iberica (a C4 annual)—on actively moving desert dunes and adjacent stabilized dunes at Little...

Recent stabilization of active sand dunes on the Canadian prairies and relation to recent climate variations

The historical activity of sand dunes on the southern Canadian prairies was investigated in order to determine the relation with recent climate variations. Changes in dune activity were determined from historical aerial photographs at seven sites with active parabolic dunes in Saskatchewan and Manitoba. The methodology developed combines digital image processing and geographical information system (GIS) analysis to measure changes in dune activity from the aerial photographs, as well as correlation analysis to determine the relation between dune activity and climate variations. Overall, dune activity has been decreasing since the early to mid 1900s as evidenced by greater vegetation colonization than sand dune migration or reactivation. The decrease in dune activity is significantly correlated with decadal-scale variations in aridity and is coincident with a decrease in annual wind speed. Evidence suggests that this response is superimposed on a longer trend towards stabilization, possibly in place since the late 1700s. Taken together, the effect of this complex response is that dune recovery on the southern Canadian prairies is prolonged well after an initial disturbance and therefore gives the impression of anomalous levels of activity for extended periods thereafter. For this reason, dune mobility indices predicated on short-term climate variations (years to decades) do not fully describe the present level of dune activity on the southern Canadian prairies.

Biodegradation of gasoline compounds (BTEX) in a water works sand filter

Various chemical compounds including aromatic gasoline compounds frequently contaminate drinking water wells in urban areas. Because ground water treatment is simple, usually consisting of aeration/stripping and sand-filtration, it is of significant interest to know the ability of the conventional treatment to remove the chemical contaminants. The removal of gasoline compounds was investigated in a two-stage pilot scale sand filter, each with a filter depth of 0.8–1 m and with a filtration rate of 7.6 m/h. The concentrations of aromatic compounds were in the range 7–15 μg/L, which are realistically low concentrations. The experiments demonstrated a surprisingly high removal efficiency of the filter system. Most of the hydrocarbons were removed already in the primary filter (3 mm sand grains) and the concentrations were in the range 0.05–0.1 μg/L at the outlet from the secondary filter (1 mm sand grains). Influent iron concentrations in the range 0–4 mg/L and backwashing did not adversely affect the biodegradation of hydrocarbons. This study has shown that a conventional biological active sand filter can act as an efficient barrier against gasoline compounds, thereby saving the consumer capital costs and operational costs from installation of supplementary treatment.

Reconstitution of dune morphologies and palaeowind regimes in the Proto-Namib since the Miocene

Abstract In the Namib Desert, indurated fossil dunes are found between the active sands. Establishment of a biostratigraphic scale based on associated mammal faunas and ratite eggshells allows the study of palaeowind fluctuations that have controlled these palaeodunes since the Middle Miocene with a temporal resolution of between 1 and 3 Ma. In the southern Namib, the Proto-Namib aeolian systems consist of crescent dunes (barkhan type). In the eastern part of the Namib Desert, the aeolianite cross-bedding corresponds to longitudinal or pyramidal dunes. These aeolian structures are also controlled by local winds, resulting from high relief and the southern trade winds : this regime is identical to that which currently sweeps, through the Namib Desert, and is related to the presence of anticyclonic conditions in the Atlantic Ocean. A regime of seasonal winds from the northeastern sector is also recorded starting in the late Miocene.

Observations of scatterometer asymmetry over sand seas and derivation of wind ripple orientation

Over sand seas the ERS scatterometer has observed asymmetries similar to those found over open water. In this paper this asymmetric backscatter response is investigated using C-band VV data from the ERS scatterometer and the data are analysed using a simple empirical model combined with quick-look Synthetic Aperture Radar (SAR) data to provide information on dune type and orientation. The results suggest that the azimuthal response is sensitive to the orientation of small-scale (millimetres to metres) wind-induced sand ripples, rather than the larger scale dune orientation. Additionally, the study investigates the feasibility of using such observations to determine ripple orientation over areas of active sand.

Biological and Physical Attenuation of Endocrine Disruptors and Pharmaceuticals: Implications for Water Reuse

AbstractA select group of endocrine disrupters, pharmaceuticals, and personal care products was studied to determine the degree of biological attenuation in water reuse applications. Laboratory investigations involved both batch reactors using biologically active sand and continuous flow simulated aquifer storage and recovery experiments. All laboratory experiments were conducted using Colorado River water spiked with various target compounds at concentrations between 10 and 100 ng/L. Field studies were also conducted to determine the occurrence and attenuation of target compounds in water reuse applications. Two golf courses irrigated with reuse water were studied to determine if turf applications led to contamination of nearby ground water. A waste water treatment facility that uses rapid infiltration basins seasonally was also tested to determine the degree of attenuation of detectable target compounds along a subsurface flowpath. A qualitative structural activity relationship model was applied to the target compounds to predict the general rate of aerobic biological degradation. Significant attenuation of many target compounds was observed in both laboratory and field experiments. Conversely, several compounds displayed limited removal during these studies. Field experiments were limited to detectable compounds and various nonbiological removal or concentration effects that may impact data interpretations, which are discussed in this paper. The predictive model was found to be moderately accurate within the confines of the project scope.

Land cover characteristics in ne iceland with special reference to jökulhlaup geomorphology

ABSTRACT Subglacial eruptions in Vatnajbkull have accounted for several jökulhlaups (glacial outburst floods) in the Northern Volcanic Zone (NVZ). These events and aeolian processes have had a considerable impact on the landscape evolution of the area. Most of this area is occupied by barren land cover; the northern margin of the barren land cover is advancing northwards, burying vegetation under wind‐blown sediment. This paper presents a land‐cover classification based on a supervised Landsat TM image classification with pre‐processing and extensive field observations. Four land cover categories were identified: (a) lava cover (34.8%); (b) barren sediment cover (39.0%); (c) vegetation (25.1%); and (d) water and snow (1.1%). The mapping of sand transport routes demonstrates that a major aeolian sand transportation pathway is situated in the western part of the study area. The sedimentary formation elongated towards the northeast is evidence of active and continuous aeolian sand transportation towards the north. Interpretation of the satellite image suggests that four main areas are affected by jökulhlaups along the Jökulsáá Fjöllum: Ásbyrgi, Grímsstaðir, Herðubreið–Möðrudalur, and the Dyngjujökull sandur. In addition, jökulhlaup‐related sediment cover (8%) in the study area, together with erosional features, are evidence of a severe and extensive jökulhlaup‐induced process of land degradation.

Toxicity of heavy metals for microorganisms isolated from slow sand filter schmutzdecke

This paper describes the susceptibility of three species of environmental bacteria isolated from the schmutzdecke of biologically active slow sand filters to cadmium, chromium and lead. The microorganisms, all identified as members of the genus Pseudomonas, were grown in tryptic soy broth with various concentrations of the selected heavy metals. The mean generation times (MGT) of the bacteria were compared to evaluate the toxic effects of the heavy metals. All three species tolerated high doses of heavy metals and the MGTs increased exponentially as the heavy metal concentrations increased; 12 mg I‐1 was die highest dose tested and the bacteria continued to grow albeit at very slow rates. In dilute media, the toxic effects of heavy metals were enhanced, illustrating the protection effect of organic matter and heavy metal complex formation. Growth studies of the isolated microorganisms on half‐strength tryptic soy agar containing 6 mg I‐1 heavy metals also proved useful in determining toxidty.