Sand Depth Research Articles

Transport of Dissolved Organic Matter through a Sandy Forest Soil

AbstractWe assessed the transport of dissolved organic matter (DOM) through a sandy, Ultisol forest soil on the southeastern U.S. Coastal Plain, and contrasted the results with similar studies from other forest regions, to test the hypothesis that DOM transport is greater through sandy Ultisols than finer textured Ultisols and Spodosols. Within a small headwater catchment, concentrations of dissolved organic carbon (DOC), a measure of DOM, were measured in soil solution at three depths (10, 30, and 90 cm) in sand A and E horizons of soil profiles, and in sand along the valley bottom at 198‐ to 264‐cm depth in shallow groundwater. Water samples were collected after every rainfall event for 21 mo using zero‐tension lysimeters, suction samplers, and piezometers. Mean concentration of DOC in soil water decreased from 25.5 mg C L‐1 at 10‐cm depth to 13.7 mg C L‐1 at 30 cm, and to 1.8 mg C L‐1 at 76 to 99 cm, before contacting clayenriched horizons. All valley bottom stations consistently averaged between 0.3 and 2.1 mg C L‐1. We did not find significant seasonal patterns, nor a correlation between DOC concentration and magnitude of rainfall events. We estimate that the flux of DOC decreased more sharply with soil depth than concentration due to attenuation of water transport through the soil profile. Compared with literature data from other forest regions, our results do not support the hypothesis that there is greater DOM transport through sandy upland soils on the Coastal Plain. Our results suggest that this is due to strong DOM retention within deep sand E horizons of these soils. Thus, strong DOM retention in forest soils appears to occur across a broader range of soil types than those exhibiting podzolization or having high clay content.

Unusual capabilities for surface movement in a normally deep-burrowed Antarctic bivalve

Many infaunal marine bivalve molluscs have the capacity to move over the sediment surface by 'creeping' or 'leaping' movements, either spontaneously or in response to predators or physical disturbance.1 The evolution of a deep-burrowing habit in some bivalve families has been accompanied by loss of the capacity for surface movement and for reburial,2-3 since burrowing to greater depths provides effective protection from both natural disturbance and most predators. It is unusual, therefore, to discover that one normally deeply burrowing species, living in the cold waters of Antarctica, has a capacity for surface movement and by a different method to any previously described for an infaunal bivalve. Laternula elliptica (King and Broderip) (Anomalodesmata, Laternulidae) is among the most abundant and ubiquitous infaunal bivalves in shallow waters around the Antarctic continent, reaching population densities of up to 86 m2 in a variety of soft sediment types.4 Adult individuals of up to 90 mm shell length may be 12-13 years old.5 L. elliptica show many features in common with other deepburrowing genera such as Mya, Lutraria or Xirfaea including long, muscular, fused and periostracumcovered siphons that are capable of considerable extension; extensively-fused mantle edges that firmly seal the mantle cavity except for siphonal and pedal apertures; a relatively small foot; and a shell that is emarginated posteriorly and cannot contain all of the soft tissues. Unlike such well-studied temperate bivalves and other species of Laternula from lower latitudes,*-7 L. elliptica retain throughout their life the ability to re-burrow if uncovered from the sediment, and also exhibit a hitherto undescribed mode of movement on the sediment surface, following dislodgement, powered by contractions of the muscles of the siphons and mantle. The observations reported here were made at the Dunstaffnage Marine Laboratory (DML) on a group of 14 L. elliptica (shell lengths ranging 44.6-78.0 mm). These were the survivors of a larger group collected near the British Antarctic Survey (BAS) base at Signy Island, Antarctica by one of us (MCR) during the austral summer of 1994-95, and subsequently retained at c 0°C, without sediment, in the marine aquarium of BAS, Cambridge for observations on their energy metabolism. At DML, small groups (<6) of the bivalves were placed in a glasssided aquarium containing c 16 cm depth of sand, with recirculating seawater at -1 to 0°C and their activity recorded for c 24 h by time-lapse video. For logistical reasons the period available for observation was limited, but over a 6-day period of recording 10 individuals (71.4%) reburied at least once and 2 (14.3%) (shell lengths 65.2 and 71.0 mm) showed surface movement as described here, before subsequently reburrowing.

An Experimental Investigation of the Resistance of Model Root Systems to Uprooting

The architecture of a tree root system may influence its ability to withstand uprooting by wind loading. To determine how the root branching pattern may alter the anchorage efficiency of a tree, artificial model root systems with different topologies and branching angles were built. The root systems were embedded at various depths in wet sand and the pull-out resistance measured. A model to predict the uprooting resistance from the data collected was designed, allowing predictions of anchorage strength with regards to architecture. The dominant factors influencing pull-out resistance were the depth and length of roots in the soil. The most efficient type of branching pattern predicted by the program was one with an increased number of roots deep in the soil. The optimum branching angle most likely to resist pull-out is a vertical angle of 90° between a lateral and the main axis. The predicted mechanically optimal radial angle between a lateral branch and its daughter is between 0 and 20°. Values of branching angle are compared with those measured in real woody root systems of European larch and Sitka spruce.

Evaluation of a wetland system designed to meet stringent phosphorus discharge requirements

In this study, a wetland system was created and managed to increase plant removal of influent phosphorus (P). This was accomplished by making P the most limiting nutrient, by enhancing mass transfer of P to the root surface and by harvesting the shoot biomass to regenerate the nutrient removal capacity of the wetland. A mixture of grass species that are tolerant of wet conditions (66% Reed canary grass) was grown in long (3.66-m) and narrow (0.l-m) troughs containing silica sand. Four replicates of three depths of sand (1.3, 2.5, and 5.1 cm) were investigated at a hydraulic loading rate between 1 500 and 1 800 m3/ha · d. Removal of P was greater than 90% in all treatments, and P was reduced from 0.480 mg/L to less than 0.001 mg/L in the 5.1-cm-deep sand treatment. The treatments removed approximately 40% of the influent nitrate (22 mg/L in; 13 mg/L out). Nutrient removal occurred 24 hours a day with small diurnal fluctuations. Grass was harvested biweekly by cutting to a uniform 7.6-cm height. Comparison of the actual amount of nutrients removed in the harvested biomass with that calculated from differences between influent and effluent concentrations showed that approximately 50% of the N and approximately 80% of the P were removed from the effluent in the biweekly grass clippings.

Disinfection of secondary effluents by infiltration-percolation

Irrigation reuse is an adequate strategy to dispose of the effluents of conventional wastewater treatment plants everywhere a chronic shortage of water resources is experienced. The most attractive usages of reclaimed water are irrigation of public parks, sports fields, golf courses an edible crops. These uses require disinfection of wastewater so as to comply with relevant regulations. Conventional disinfection procedures are fairly effective; but, in Mediteranean countries, low technology techniques, such as lagooning and infiltration-percolation, are often more reliable. The cost of drained infiltration-percolation facilities is highly dependant on the volume of their filtrating sand bed. Therefore, relationship among hydraulic load, sand depth and disinfection efficiency are of great importance. A circular drained dune sand infiltration percolation filter, 1.5 m sand deep, with a surface of 565 m2, was constructed in Vall-Llobrega, Catalonia, Spain. The filter was fed with activated sludge effluent using a pivot irrigation system equipped with low-pressure bubbles. The plant worked for two years, the hydraulic load ranging from 0.165 to 0.35 m per day of infiltrating surface. Physico-chemical parameters, total and faecal coliforms contents were monitored. A pivot irrigation system can be considered a major technological improvement.

Adaptation of forage Kochia accessions across an environmental gradient in rush valley, Utah

Forage kochia (Kochia prostrata) is native to Eurasia. It is a useful plant for reclamation in semiarid and arid regions with mineral soils. Fourteen accessions representing both forage kochia subspecies and all known polyploid levels (2x‐6x) were tested for adaptation over an environmental gradient represented by three study sites differing in native plant composition, average annual precipitation, and soil type. Plants were established by transplanting in 1988 and 1989 and evaluated for growth (height, crown diameter, biomass) parameters and for stand establishment, growth habit, uniformity of growth, vigor, cover, seed production, survival, and recruitment from 1990 to 1992. Soil characteristics (pH, SAR, salinity, sand, clay, silt, organic matter, NO3‐N, Ca, Na, Mg, P, K, CaCO3, and effective rooting depth) were measured at each study site. Two hypotheses were addressed. First, it was confirmed that forage kochia accessions in general perform better in lighter textured soils and at higher precipitatio...

Disinfection of secondary effluents by infiltration-percolation

Irrigation reuse is an adequate strategy to dispose of the effluents of conventional wastewater treatment plants everywhere a chronic shortage of water resources is experienced. The most attractive usages of reclaimed water are irrigation of public parks, sports fields, golf courses an edible crops. These uses require disinfection of wastewater so as to comply with relevant regulations. Conventional disinfection procedures are fairly effective; but, in Mediteranean countries, low technology techniques, such as lagooning and infiltration-percolation, are often more reliable. The cost of drained infiltration-percolation facilities is highly dependant on the volume of their filtrating sand bed. Therefore, relationship among hydraulic load, sand depth and disinfection efficiency are of great importance. A circular drained dune sand infiltration percolation filter, 1.5 m sand deep, with a surface of 565 m2, was constructed in Vall-Llobrega, Catalonia, Spain. The filter was fed with activated sludge effluent using a pivot irrigation system equipped with low-pressure bubbles. The plant worked for two years, the hydraulic load ranging from 0.165 to 0.35 m per day of infiltrating surface. Physico-chemical parameters, total and faecal coliforms contents were monitored. A pivot irrigation system can be considered a major technological improvement.

Effect of sowing depth and water potential on seedling emergence of Lupinus species

Large differences in responses of germination and seedling emergence to water potential and sowing depth were detected among Lupinus species varying substantially in seed size. Seeds of 7 species (L. pilosus, L. atlanticus, L. albus, L. cosentinii, L. luteus, L. angustifolius and L. hispanicus) germinated rapidly in moist sand (-0.05 MPa). Germination of all these species was reduced when seeds were raised in sand in which water potential was increased from -1.0 to -0.5 MPa at 4 days after sowing, and then to -0.2 MPa at 18 days after sowing. Percentage germination after 20 days was much higher in small-seeded species (L. hispanicus, L. angustifolius, L. luteus) than in large-seeded species (L. albus, L. atlarzticus, L. pilosus). Germination responses were related to rate of water uptake by seeds from sand at 0.5 MPa. Seedling emergence of pre-germinated seeds sown at different depths in moist (-0.05 MPa) and dry (-0.3 MPa) sand varied greatly among 6 species. An increase in sowing depth from 4 to 8 cm retarded seedling emergence to a greater extent than a decrease in water in L. piosus, L. luteus, L. cosentinii and L. atlanticus. L. angustifolius seedling emergence was less affected by variation in sowing depth and water potential than other species, although a decrease in water potential had a relatively large effect on seedling emergence from 4 cm. A decrease in water potential also decreased seedling emergence of L. albus more than deeper sowing. Seedling emergence responses of 4 species (L. angustifolius, L. luteus, L. albus, L. atlanticus) were compared in an experiment where dry seeds were sown in dry sand (-0.3 MPa) at different distances above a moist sand (-0.05 MPa) zone in specially constructed trays. Small-seeded species (L. angustifolius and L. luteus) emerged most rapidly from the shallowest sowing (3 cm below the surface, 9 cm above the moist zone), whereas the large-seeded species L. albus and L. atlanticus emerged most rapidly from sowings at intermediate depths (6 and 9 cm). L. albus and L. angustifolius seedlings emerged far more rapidly when sown on the surface of the moist sand (12 cm) than did L. luteus and L. atlanticus, and were far more tolerant of variation in sowing depth. The implications of these findings are discussed with particular reference to improving lupin crop establishment following early dry sowing in the West Australian wheatbelt.

Hydrolysis of urea in two sandy soils under citrus production as influenced by rate and depth of placement

Abstract The use of urea as a nitrogen (N) source is increasing in citrus production on sandy soils in Florida. Entisol and Spodosol are the two major soil orders used for citrus production. This study was conducted to examine the difference in rate of urea hydrolysis as influenced by depth of placement in a Candler fine sand (Typic Quartzipsamment) and a Wabasso sand (Alfic Haplaquod). These two soils represent the contrasting soils typically found in the citrus growing region of central, southern, and east coast regions of Florida. The rate of urea hydrolysis was faster in a Candler fine sand than that in a Wabasso sand and was greater for the low (0.25 g N/kg) than that for the increased (0.50 or 1.00 g/kg) rates of urea applications in both soils. In a parallel experiment, the rate of urea hydrolysis was examined at various depths (0 to 15‐, 15 to 30‐, 30 to 45‐, and 45 to 60‐cm) in the Candler fine sand using in situ and laboratory incubation studies. The rate of urea hydrolysis decreased with an increase in depth of placement of urea. Increased content of organic matter and higher soil temperature in the surface soil may contribute to increase in urease activity thus resulting in increased rate of urea hydrolysis than that in the lower depth soil.

Does Sand Application to Soil Surface Benefit Cranberry Production?

The effect of sand application to `Stevens' cranberry (Vaccinium macrocarpon Ait.) was studied for 3 years in a 24-year-old (site 1) and an 8-year-old (site 2) commercial planting. Treatments in Apr. 1991 consisted of a onetime sand application of 1.3 or 2.5 cm on the surface of the cranberry bed and a nonsanded control. Yield component data were collected in Fall 1991 through 1993. In 1991, 2.5 cm of sand reduced yield 50% at site 2 compared to the nonsanded control. At site 1, the 2.5-cm sand depth did not reduce yield, while the 1.3-cm-deep application improved yield 18% compared to the control. The year after sanding (1992), yields equalized across all treatments at both sites. In 1993, there was no significant difference in yield for treatments at site 1. At site 2, however, heavy sanding reduced yield 63% compared to 1.3 cm of sand. Our work suggests that heavy sanding is not recommended for `Stevens' cranberry beds in Oregon.

Uplift Resistance of Buried Pipelines in Sand

A centrifugal model study into the influence of pipe diameter, depth of burial and backfill density on the resistance to uplift of pipes in sand is reported. No significant differences between the behaviour of buried pipes and that of strip anchors is found, justifying the application of anchor uplift theory to buried pipeline behaviour. Several anchor-based theories overestimate the stability of the model pipes tested, although predictions from the theories of Rowe and Davis (1982), Vermeer and Sutjiadi (1985) and Vesic (1971) yield reasonable agreement for models in dense sand, while the simple Vertical Slip Surface Model is alone in providing sensible predictions for pipes in loose sand. The influence of pipe surface roughness, although significant for pipes at shallow depth in dense sand, is minimal at deeper embedments.

Acoustic backscatter analysis from a smooth sand surface

A multiscattering theory to describe backscatter behavior in water-filled sands has been developed for smooth sand surfaces. The theory is based on a two-dimensional solution of the diffusion equation and a Biot propagation theory for porous materials. Experiments were conducted at high frequencies (80–120 kHz) to measure backscatter at shallow grazing angles from smooth sand surfaces at varied sand depths. In addition, reflection measurements were made at normal incidence to verify the smoothness of the sand surface. Comparisons of theoretical model backscatter results to experimental measurements were then made. [Work supported by ONR, Ocean Acoustics Program, Code 11250A.]

Acidification rates in the central wheatbelt of Western Australia. 2. On a sandy duplex soil

The rate and mechanisms of acidification were determined on a sandy duplex soil (depth of sand 30-45 cm) under a cereal-annual pasture rotation in Western Australia. We also evaluated the effect of rotation (intensity of cropping) on relative acidification of a sandy duplex soil. Rate of acidification was based on a linear regression analysis between soil pH and years since clearing. Sites were sampled to a depth of 50 cm in 10-cm increments and measurements included soil pH, pH buffering capacity, and bulk density. The effect of different rotations on the acidification rate was determined by soil sampling a rotation experiment which had been established for 25 years. Sampling and measurements were similar to the regression analysis. From regression, the rate of acidification for the profile was 0.15 kmol H+/ha.year, requiring 7.7 kg CaCO3 to neutralise. Most of the acidification could be accounted for by removal of alkaline products. Acidification was occurring to a depth of 30 cm, the acidification rate decreasing with depth. In the surface 20 cm the pH decline was 0.005-0.006 units/year. In the rotation experiment, the rate of acidification relative to continuous wheat without fertiliser nitrogen (N) ranged from 0.35 kmol H+/ha .year (17.5 kg CaCO3) for continuous wheat with fertiliser N to 0.92 kmol H+/ha. year (45.8 kg CaCO3) for continuous pasture. Between these rates was 1 year pasture-1 year cereal (0.41 kmol H+/ha. year, 20.5 kg CaCO3) and 2 years pasture-1 year cereal (0.82 kmol H+/ha . year, 41.2 kg CaCO3). Acidification was occurring to 60 cm depth in all rotations, mostly due to nitrate leaching, removal of alkaline products, and build-up of organic matter.

Tertiary treatment of sewage effluent via pilot scale slow sand filtration

Abstract In view of limited information available about the performance of actual size slow sand filtration as a tertiary process in sewage treatment a pilot scale study was conducted over a period of one year using the secondary treated effluent from North Aramco Wastewater Treatment Plant, Dhahran, at a flow rate of 0.16 m hr‐1 (2L min‐1) to determine the process efficiency. Two sizes of local sand, i.e., effective size (ES) = 0.31, uniformity coefficient (UC) = 2.00; and ES = 0.56, UC = 1.64, were evaluated in terms of removal of major pollution parameters such as organic matter, micro‐organisms and nutrients. Effective range of the filter depth was also investigated by conducting the experiments at three different depths of the sand bed, i.e., 135, 105, and 55 cm for each size of the sand. It was found that removals of BOD, COD, standard plate counts, nitrate, phosphate and sulphate vary from 79–92%, 40–60%, 88–93%, 17–30%, 8.3–84%, and 5–10%, respectively, at various sand depths for two different sizes of the sand.

Rate Effect on Lateral Soil Restraint of Pipelines

The purpose of this study was to determine the pipeline lateral soil restraint due to relative movement between the pipeline and the dry sand. A large scale drag device with dimensions of 6' × 6' × 4' (1.8 m × 1.8 m × 1.2 m) had been fabricated to study the primary variables such as sand density, pipe diameter, pipe burial depth and relative velocity on the pipe lateral soil restraint. All 120 test results indicated that the dimensionless maximum soil restraints and the corresponding displacements exhibited the power law relationship with the pipe velocity, V/D. In dense sand, the pipe velocity exponents, n, were found constant and be irrespective of pipe burial depth, however, values of n increased with burial depth in loose sand and emerged with the dense sand constant exponent at the burial depth of 10.5 times of pipe diameter. Also, the generalized maximum soil restraints increased with depth of burial, until the burial depths with H/D of 10.5 in loose sand and of 12.5 in dense sand were reached, at which points, the soil restraints became constant. Force-displacement relationship of pipe-soil interaction could be represented by a two- constant hyperbolic equation. These two constant values of a and b were found to have the power law relationship with the pipe velocity, V/D.

Wastewater Treatment over Sand Columns – Treatment Yields, Localisation of the Biomass and Gas Renewal

Domestic wastewater treatment by infiltration-percolation is a process that is becoming common in France. The aim of this study is to find the depth of biologically active substrate in an infiltration basin by determining the depth of the media colonised by the biomass and by studying oxygen renewal mechanisms. The study using sand columns has allowed simultaneous comparison, on the same profile, of biomass content (ATP), gaseous composition (chromatography) and the variations of the effluent quality (carbon, nitrogen, phosphorus). Down to a depth of 30 cm, removal rates achieved in terms of conventional treatment parameters are very high (COD and SS &amp;gt; 90%, NH4+ ≈ 95%, total phosphorus ≈ 50%). Beyond a depth of 15 cm, the biomass content (expressed in ATP) is ten times less than at the surface, and virtually ceases to develop. Monitoring of O2 levels points to the need for drying periods in order to ensure natural ventilation of the basins. The primary settling stage must be effective in order to avoid any risk of clogging which would prevent the air from being renewed by diffusion.The length of the drying period must be almost double that of the flooding period to allow the media to recover as much of its treatment capacity as possible. This study pinpointed the depth of the biologically active substrate at arround 30 cm. The data obtained from this trial project point to the following design criteria: 1.5 m2/p.e. spread over three basins, and a drying period twice as long as the flooding period. The sand depth will depend on the plant's overall water quality objectives: around 0.50 m for the removal of carbonaceous pollution and nitrification of Kjeldahl nitrogen, a greater depth for disinfection purposes.

Infiltration Percolation in France: 10 Years Experience

A survey was carried out during the late '80s over 7 infiltration percolation plants, serving populations ranging between 400 and 1700. With sand depths, hydraulic loads, influent COD and NTK concentrations respectively ranging from 0.6 to 0.2 m, 0.07 to 0.77m/day, 820 to 75 and 70 to 10 mg/l, and with different operating schedules, this set of plants displays a wide spectrum of infiltration percolation in use. When plants are suitably designed, sized and operated, primary effluents oxidation is very effective and current EEC quality standards for wastewater treatment plant effluents are matched. Disinfection is poor, below the level expected from laboratory and pilot plant data. This is due to non-uniform spreading of the influents on the infiltration areas and exceedingly short circuits and short water detention times in the sand beds. Based on a theoretical approach and on data obtained from these and many other plants, a sizing methodology is provided. Recommended improvements in the spreading technology, as well as in the plant design and management, should lead to more reliable oxidation and disinfection performance

Slow Sand Filtration of Secondary Effluent

This pilot-scale study comprises a one-year field evaluation of slow sand filtration as a tertiary treatment of secondary wastewater effluents using two different effective sizes of local sand, i.e. 0.31 and 0.56 mm, to find a simple advanced wastewater treatment method. The filter was operated at sand depths of 135, 105, and 55 cm, respectively, for each size of the sand, to determine the operational range of the sand depth. Secondary effluent from North Aramco Wastewater Treatment Plant (NAWTP) was applied at a hydraulic loading of 0.16 m/h. The filter consistently gave over 90% removal of turbidity for both sizes of the sand at various depths of the filter bed along with over 93% removal of total coliform bacteria. It was observed that the use of coarse sand resulted in longer duration of filter operation as compared to the fine sand for similar removal of turbidity and coliform, i.e., 84 days in the case of coarse sand compared to a maximum of 26 days for the finer sand. The development of the head loss in the sand media was extremely small during the initial period of the operation, which later increased exponentially with most of the head loss occurring in the top dirty surface of the filter, known as \Ischumtzdecke\N in German.

Survival ofRhizoctonia solaniAG-4 in Residual Peanut Shells in Soil

The survival of Rhizoctonia solani AG-4 in residual peanut (Arachis hypogaea) shells was studied for 2 yr. Surface sterilized mature peanut pods colonized by R. solani AG-4 and untreated pods were placed separately in fiberglass-mesh bags and buried at 0, 7.6, and 25.4 cm depths in Tifton loamy sand in field microplots. Shells of pods were sampled at 6-mo intervals and assayed on tannic acid-benomyl agar for the recovery of R. solani AG-4 and other soilborne fungi. Recovery of R. solani AG-4 after 6 mo was greater (P≤0.05) from shells of treated pods placed on the soil surface than on those buried in the soil. Survival of R. solani AG-4 from shells at 12 mo was not different (P≤0.05) from those at 6 mo. R. solani AG-4 was isolated from less than 1% of the total shells after 18 and 24 mo

Desorption and Extraction of Selected Heavy Metals from Soils

AbstractThe need for proper disposal of industrial wastes and for remediation methods for soils contaminated with heavy metals necessitates a better understanding of the processes involved in mobilizing, transporting, and retaining elements in surface soils. The objective of this study was to investigate the desorption in water and efficacy of several traditional extraction agents in removing Tc, Np, Mo, U, Cr, Pb, Cs, and Th. Selected slices were taken with depth in acidic sand (Dystrochrept) soil cores that were spiked for 4 yr. Similarly, Tc, Np, and U were desorbed and extracted from the clay subsoil of reed/sedge peat cores following a one‐season migration study. Technetium and Mo behaved as anions, and the small amount of Tc retained was attributed to insoluble organic complexes and oxides in the sandy soil and carbonates in the clay subsoil. The retention of Mo was attributed to colloidal Fe(III) oxides and organic colloids or complexes. Neptunium sorption appears to be dependent on the variable charge of the soil, making organic matter and pH important factors. Uranium and Pb were associated with the oxides. Cesium and Cr took part in inorganic reactions that fixed them rigorously to the soil solids or formed precipitates; Th formed organic complexes. Results suggest that remediation techniques for soils contaminated with Tc, Mo, and Np could be quite successful using intense leaching with acidified water. Soils containing U, Pb, and Th may be partially reclaimed by manipulation of the organic matter or leaching with organic acids; however, soils contaminated with Cs and Cr would require extensive chemical treatment.