Burial Experiment Research Articles

Preparation and biodegradation of copolyesters based on poly(ethylene terephthalate) and poly(ethylene glycol)/oligo(lactic acid) by transesterification

AbstractThe poly(ethylene terephthalate‐co‐ethyleneoxide‐co‐DL‐lactide) copolymers were successfully prepared by the melt reaction between poly(ethylene terephthalate), poly(ethylene glycol), and DL‐oligo(lactic acid) without any catalysts. The transesterification between ethylene terephthalate, ethyleneoxide, and lactide segments during the reaction was confirmed by the 1H NMR analysis. The effect of reaction temperatures and the starting feed ratios on the molecular microstructures, molecular weights, solubility, thermal properties, and degradability of the copolyesters was extensively studied. The values of crystallization temperature, melting temperature, crystallization, and melting enthalpy of the copolyesters were found to be influenced by the reaction temperatures, starting feed ratios, etc. The copolyesters showed good tensile properties and were found to degrade in the soil burial experiments during the period of 3 months. The morphology of the copolyester films were also investigated by scanning electron microscopy during soil burial degradation. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers

The seed bank longevity index revisited: limited reliability evident from a burial experiment and database analyses.

Seed survival in the soil contributes to population persistence and community diversity, creating a need for reliable measures of soil seed bank persistence. Several methods estimate soil seed bank persistence, most of which count seedlings emerging from soil samples. Seasonality, depth distribution and presence (or absence) in vegetation are then used to classify a species' soil seed bank into persistent or transient, often synthesized into a longevity index. This study aims to determine if counts of seedlings from soil samples yield reliable seed bank persistence estimates and if this is correlated to seed production. Seeds of 38 annual weeds taken from arable fields were buried in the field and their viability tested by germination and tetrazolium tests at 6 month intervals for 2.5 years. This direct measure of soil seed survival was compared with indirect estimates from the literature, which use seedling emergence from soil samples to determine seed bank persistence. Published databases were used to explore the generality of the influence of reproductive capacity on seed bank persistence estimates from seedling emergence data. There was no relationship between a species' soil seed survival in the burial experiment and its seed bank persistence estimate from published data using seedling emergence from soil samples. The analysis of complementary data from published databases revealed that while seed bank persistence estimates based on seedling emergence from soil samples are generally correlated with seed production, estimates of seed banks from burial experiments are not. The results can be explained in terms of the seed size-seed number trade-off, which suggests that the higher number of smaller seeds is compensated after germination. Soil seed bank persistence estimates correlated to seed production are therefore not useful for studies on population persistence or community diversity. Confusion of soil seed survival and seed production can be avoided by separate use of soil seed abundance and experimental soil seed survival.

On the use of fungicides in ecological seed burial studies

AbstractEvidence for effects of saprophytic fungi on buried seed demography is usually obtained from studies involving the simultaneous burial of fungicide-treated seeds and of untreated seeds. However, any potential influence of fungicide treatment on seed dormancy levels is generally ignored in these studies. Also, some studies assume that a combination of several fungicidal compounds provides better protection against a broader range of fungi, ignoring chemical interactions that may potentially occur between different compounds. To investigate these issues, we carried out a 6-month burial experiment using seeds ofAnthriscus sylvestris(L.) Hoffm.,Centaurea nigraL. andDaucus carotaL., and three substrates differing in organic matter content. Three fungicidal compounds, captan, iprodione and mancozeb, were applied alone and in combination, including an untreated control. All fungicidal compounds and combinations thereof provided protection against fungal-induced seed mortality and, except for a low efficacy of iprodione in protecting seeds ofAnthriscus, there were no pronounced differences in seed mortality between different fungicide treatments. Captan temporarily inhibited germination inCentaurea, whereas a similar inhibition inDaucusseeds caused by mancozeb was more long lasting, suggesting an induction of secondary dormancy. Organic matter content had only a negligible influence on these results. Our results suggest that the basic conclusions from most seed burial studies are robust with respect to their choice of fungicide. We conclude by discussing further implications of our findings for the design and interpretation of seed burial studies.

Mechanical, moisture absorption, and biodegradation behaviours of bacterial cellulose fibre-reinforced starch biocomposites

In this work, bacterial cellulose (BC) nanofibres were used as the biodegradable reinforcement. The BC nanofibres were incorporated in the starch plasticised with glycerol via a solution impregnation method. Tensile properties of the BC/starch biocomposites were tested and compared with those of the unreinforced starch. Moisture absorption of the biocomposites under 75% RH at 25 °C was analysed. The kinetics of sorption–diffusion process was investigated and typical kinetic parameters D, k, and M ∞ were determined. Additionally, the BC/starch biocomposite (15.1 wt.% BC) and starch were submitted to biodegradation by soil burial experiments in perforated boxes. Tensile strength after exposure to moisture and microorganism attacks was measured. It is found that the moisture sorption mechanism in the BC/starch biocomposites follows a Fickan diffusion mode. The presence of BC nanofibres improves the tensile properties and the resistance to moisture and microorganism attacks. The mechanisms behind these phenomena are discussed in this paper.

Different requirements for physical dormancy release in two populations of Sophora alopecuroides relation to burial depth

AbstractMost species of Fabaceae produce seeds with physical dormancy which was broken by some environmental factors in the field, yet for the mechanism of physical dormancy release in the natural condition is still poorly understood. In present study, seeds of Sophora alopecuroides from two populations were placed on the soil surface or buried at depths of 2 and 7 cm in the field and were exhumed at time intervals to assess the changes of dormancy. Also, microenvironments were simulated in the laboratory to determine the possible components (temperature, temperature fluctuation, and moisture) involved in physical dormancy release. The laboratory work indicated that wet heat is an important dormancy release mechanism for both populations; and dry heat for one of them, but showed no effects on the other one. Consistent with that, burial experiment showed seeds of two populations had two contrasting‐dormancy release patterns in the field. Most seeds of the dry heat sensitive population released dormancy but the other one remained dormant when seeds placed on the soil surface for 11 months (where seeds were exposed to dry heat but not wet heat). The difference of physical dormancy release pattern response to burial depth and simulated condition may attribute to seed coat color and hilum thickness which showed significantly different between two populations. This conclusion may improve understanding of physical dormancy release mechanism among populations and have a practical use for grassland management and weed control.

Inoculum potential of Rhizopogon spores increases with time over the first 4 yr of a 99‐yr spore burial experiment

In disturbed or pioneer settings, spores and sclerotia of ectomycorrhizal fungi serve as the necessary inoculum for establishment of ectomycorrhizal-dependent trees. Yet, little is known about the persistence of these propagules through time. Here, live field soil was inoculated with known quantities of basidiospores from four pine-associated species of Rhizopogon; these samples were then buried in retrievable containers, and pine seedling bioassays of serially diluted spore samples were used to measure spore viability. In the first 4 yr, no evidence of loss of spore viability was found in the four Rhizopogon species tested, but all four species exhibited dormancy in which a maximum of 1-8% of their spores were initially receptive to pine roots. There were some differences between species in overall inoculum potential of their spores, but all species broke dormancy at a statistically similar rate. This result provides evidence for spore dormancy in a common ectomycorrhizal genus, but it also precludes our ability to estimate the longevity of the spores accurately. Nevertheless these results, coupled with the observed patterns of Rhizopogon spore banks, suggest that at least decade-long durations are likely. As this experiment progresses, the true longevity of the spores will eventually be revealed.

Mine Impact Burial Prediction From One to Three Dimensions

The Navy’s mine impact burial prediction model creates a time history of a cylindrical or a noncylindrical mine as it falls through air, water, and sediment. The output of the model is the predicted mine trajectory in air and water columns, burial depth/orientation in sediment, as well as height, area, and volume protruding. Model inputs consist of parameters of environment, mine characteristics, and initial release. This paper reviews near three decades’ effort on model development from one to three dimensions: (1) one-dimensional models predict the vertical position of the mine’s center of mass (COM) with the assumption of constant falling angle, (2) two-dimensional models predict the COM position in the (x,z) plane and the rotation around the y-axis, and (3) three-dimensional models predict the COM position in the (x,y,z) space and the rotation around the x-, y-, and z-axes. These models are verified using the data collected from mine impact burial experiments. The one-dimensional model only solves one momentum equation (in the z-direction). It cannot predict the mine trajectory and burial depth well. The two-dimensional model restricts the mine motion in the (x,z) plane (which requires motionless for the environmental fluids) and uses incorrect drag coefficients and inaccurate sediment dynamics. The prediction errors are large in the mine trajectory and burial depth prediction (six to ten times larger than the observed depth in sand bottom of the Monterey Bay). The three-dimensional model predicts the trajectory and burial depth relatively well for cylindrical, near-cylindrical mines, and operational mines such as Manta and Rockan mines.

Short- and Long-Term Olivine Weathering in Svalbard: Implications for Mars

Liquid water is essential to life as we know it on Earth; therefore, the search for water on Mars is a critical component of the search for life. Olivine, a mineral identified as present on Mars, has been proposed as an indicator of the duration and characteristics of water because it dissolves quickly, particularly under low-pH conditions. The duration of olivine persistence relative to glass under conditions of aqueous alteration reflects the pH and temperature of the reacting fluids. In this paper, we investigate the utility of 3 methodologies to detect silicate weathering in a Mars analog environment (Sverrefjell volcano, Svalbard). CheMin, a miniature X-ray diffraction instrument developed for flight on NASA's upcoming Mars Science Laboratory, was deployed on Svalbard and was successful in detecting olivine and weathering products. The persistence of olivine and glass in Svalbard rocks was also investigated via laboratory observations of weathered hand samples as well as an in situ burial experiment. Observations of hand samples are consistent with the inference that olivine persists longer than glass at near-zero temperatures in the presence of solutions at pH approximately 7-9 on Svalbard, whereas in hydrothermally altered zones, glass has persisted longer than olivine in the presence of fluids at similar pH at approximately 50 degrees C. Analysis of the surfaces of olivine and glass samples, which were buried on Sverrefjell for 1 year and then retrieved, documented only minor incipient weathering, though these results suggest the importance of biological impacts. The 3 types of observations (CheMin, laboratory observations of hand samples, burial experiments) of weathering of olivine and glass at Svalbard show promise for interpretation of weathering on Mars. Furthermore, the weathering relationships observed on Svalbard are consistent with laboratory-measured dissolution rates, which suggests that relative mineral dissolution rates in the laboratory, in concert with field observations, can be used to yield valuable information regarding the pH and temperature of reacting martian fluids.

Experiments on the survival of six brackish macro-invertebrates from the Baltic Sea after dredged spoil coverage and its implications for the field

Physical disturbance by disposal of dredged materials in estuarine and coastal waters may result in burial of benthic fauna. Survival rates depend on a variety of factors including the type and amount of disposed materials and the lifestyle of the organisms. Laboratory burial experiments using six common macrobenthic invertebrates from a brackish habitat of the western Baltic Sea were performed to test the organisms' escape reaction to dredged material disposal. Experimental lab-results were then extrapolated to a field situation with corresponding bottom topography and covering layer thicknesses at experimental field disposal study sites. Resulted survival rates were then verified by comparison with results of an earlier field study at the same disposal sites. Our experimental design in the lab included the disposal of two types of dredged material (i.e. ‘till’ and ‘sand/till mixture’) and two covering layer depths (i.e. 10–20 cm and 14–40 cm). All three bivalves Arctica islandica (Linnaeus), Macoma balthica (Linnaeus), Mya arenaria (Linnaeus) and the polychaete Nephtys hombergii (Savigny) successfully burrowed to the surface of a 32–41 cm deposited sediment layer of till or sand/till mixture and restored contact with the overlying water. These high escape potentials could partly be explained by the heterogeneous texture of the till and sand/till mixture with ‘voids’. The polychaete Bylgides ( Harmothoe) sarsi (Malmgren) successfully burrowed through a 16 cm covering layer whereas the polychaete Lagis koreni (Malmgren) showed almost no escaping reaction. No general differences in escape behaviour after burial were detected between our test species from the brackish habitat and those reported in the literature for the same species in marine environments. However, a size-dependence in mobility of motile polychaetes and M. arenaria was apparent within our study. In comparison to a thick coverage, thin covering layers (i.e. 15–16 cm and 20 cm) increased the chance of the organisms ( N. hombergii and M. arenaria) to reach the sediment surface after burial. This was not observed for the other test species. While crawling upward to the new sediment surfaces burrowing velocities of up to 8 cm d − 1 were observed for the bivalves and up to 20 cm d − 1 for N. hombergii. Between 17 and 79% of the test organisms showed burrowing activity after experimental burial. The survival rate (defined as the ability to regained contact with the sediment surface) ranged from 0 to 33%, depending on species and on burial depth. The organisms reached the sediment surface by burrowing (polychaetes and bivalves) and/or by extending their siphons to the new sediment surface (bivalves). The extrapolation of laboratory survival rates to the two disposal sites was obtained based on the in situ thicknesses of the dredged spoil layers measured by multi-beam echo sounder. This resulted in total average survival rate estimates for the test species of 45 and 43% for the two disposal sites. The results obtained during the laboratory tests and the following extrapolation to the field were verified by the range of results from a previous field study, using grab sampling shortly before and after a disposal event in June 2001. The effect of dredged material disposal on the tested Baltic Sea benthic macrofauna was assessed by extrapolating the verified laboratory results to the field.

Hybrid composite based on poly(vinyl alcohol) and fillers from renewable resources

AbstractHybrid composite laminates consisting of polyvinyl alcohol (PVA) as continuous phase (33% by weight) and lignocellulosic fillers, derived from sugarcane bagasse, apple and orange waste (22% by weight) were molded in a carver press in the presence of water and glycerol such as platicizers agents. Corn starch was introduced as a biodegradation promoter and gluing component of the natural filler and synthetic polymeric matrix in the composite (22% by weight). The prepared laminates were characterized for their mechanical properties and degradative behavior in simulated soil burial experiments. The fibers type and content in composite impacted mechanical properties. Materials based on PVA and starch with apple wastes and sugarcane bagasse fillers were much harder (Young's Modulus respectively, 57, 171 MPa) than materials prepared with orange wastes (17 Mpa). Respirometric test revealed that soil microbes preferentially used natural polymers and low molecular weight additive as a carbon source compared to biodegradable synthetic polymer. The presence of PVA in formulations had no negative effect on the degradation of lignocellulosic fibers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Occurrence of physical dormancy in seeds of Australian Sapindaceae: a survey of 14 species in nine genera.

Sapindaceae is one of 16 angiosperm families whose seeds have physical dormancy (PY). However, the extent and nature of PY within this family is poorly known. The primary aims of this study were: (1) to evaluate seed characteristics and determine presence (or not) of PY within nine genera of Australian Sapindaceae; and (2) to compare the frequency of PY across the phylogenetic tree within Australian Sapindaceae. Viability, imbibition and seed characteristics were assessed for 14 taxa from nine genera of Sapindaceae. For five species of Dodonaea, optimal conditions for germination and dormancy break were evaluated. An in situ burial experiment was performed on D. hackettiana seeds to identify the factor(s) responsible for overcoming PY. Classes of dormancy and of non-dormancy for 26 genera of Sapindaceae were mapped onto a phylogenetic tree for the family. Mean seed viability across all taxa was 69.7 %. Embryos were fully developed and folded (seven genera) or bent (two genera); no endosperm was present. Seeds of all five Dodonaea spp. and of Distichostemon hispidulus had PY. Hot-water treatment released PY in these six species. Optimal germination temperature for seeds of the four Dodonaea spp. that germinated was 15-20 degrees C. Following 5 months burial in soil, 36.4 % of D. hackettiana seeds had lost PY and germinated by the beginning of the winter wet season (May). Laboratory and field data indicate that dormancy was broken by warm, moist temperatures (> or =50 degrees C) during summer. PY occurs infrequently in genera of Sapindaceae native to Australia. Seeds of Dodonaea and Distichostemon had PY, whereas those of the other seven genera did not. Seeds of these two genera and of Diplopeltis (a previous study) are the only three of the 20 native Australian genera of Sapindaceae for which germination has been studied that have PY; all three belong to subfamily Dodonaeoideae.

Seed longevity of eight species common during early postfire regeneration in south‐eastern Spain: A 3‐year burial experiment

AbstractSpecies that frequently regenerate sexually after fire were not found in soil seed banks of previous studies in south‐eastern Spain (Province of Murcia) and this led to the idea of studying seed longevity in the species concerned. A seed burial field experiment was carried out over a period of 30 months to examine the seed longevity of eight species that mainly reproduce sexually during early postfire succession. In addition, longevity was determined for seeds stored at room temperature and the results were compared to those obtained for buried seeds. Seeds of the study species showed very different patterns of persistence. Water‐impermeable seeds of Cistus albidus, Cistus clusii, Fumana laevipes, Convolvulus lanuginosus and Calicotome intermedia survived at least 1 year of burial in high numbers. However, seeds of Calicotome intermedia did not survive a second year, and only approximately 20% of the Fumana laevipes and Convolvulus lanuginosus seeds were alive after 30 months of burial. The longevity of buried water‐permeable seeds of Asterolinum linum‐stellatum, Teucrium pseudochamaepitys and Stipa tenacissima did not exceed 2 years. When buried for 30 months in a coastal and a mountain population site, the number of viable seeds of Convolvulus lanuginosus and Stipa tenacissima did not differ significantly between the two sites. Seeds of most species showed better survival under room temperature than under burial conditions. We concluded that the seed longevity of some species in soil might have previously been overestimated.

Laboratory investigation of biodegradability of a polyurethane foam under anaerobic conditions

Polyurethane (PU) foams can be used in many remediation applications as an isolation material to prevent the release of hazardous materials into the environment. The integrity of a PU foam was investigated in this study using short-term accelerated laboratory experiments including bioavailability assays, soil burial experiments, and accelerated bioreactors to determine the fate of PU foam in the soil where anaerobic processes are dominant. The experimental results have shown that the studied PU foam is likely not biodegradable under anaerobic conditions. Neither weight loss nor a change in the tensile strength of the PU material after biological exposure was observed. The FT-IR chemical signature of the PU foams was also nearly identical before and after biological exposure. The composition of the PU material (aromatic polyester and polyether PU) used in this study could have played a significant role in its resistance to microbial attack during the short-term accelerated experiments.

Effects of sand burial disturbance on seedling growth of Nitraria sphaerocarpa

Nitraria sphaerocarpa Maxim. (Zygophyllaceae) is a desert shrub, emerged seedlings may easily be covered by sand, thus the influence of sand burial on seedling survival and growth was studied. The experiment was conducted under controlled greenhouse conditions. Seeds were sorted into three size-classes and buried at 2 cm depths in plastic pots filled with sand. Two weeks after seedling emergence, seedlings were buried in sand to various depths of 0, 33, 67, 100 and 133% of their mean height. Seedling survivorship, height, mass, relative height growth rate, absolute height growth rate, biomass allocation to root, biomass allocation to belowground stem and biomass allocation to aboveground stem were significantly affected by burial depth, however, seedling survivorship, mass, relative height growth rate were not significantly affected by seed size. In the unburied and partial burial treatments, individual seedlings exhibited high survivorship of approximately 85-100% for all size-classes seeds. However, only about 60, 39 and 43% seedlings survived when the burial depth reached 100% of their height, for large, medium and small sized seeds, respectively. When the burial depth increased to 133% of seedling height, no seedlings survived. Seedling height, mass and absolute height growth rate in partial burial treatments, were higher than those of the unburied and completely buried treatments. In each seed size class, with increasing burial depth, or in each burial depth, with decreasing seed size, there was a tendency that both biomass allocation to root and biomass allocation to belowground stem increased, while biomass allocation to aboveground stem decreased. The burial experiment of N. sphaerocarpa showed that partial burial at depth of 33 and 67% of seedling height increased seedling vigor, however, when burial depth reached the whole height of seedlings, it reduced the seedling vigor, and the burial at depth of 133% of their height, led to death of all seedlings.

Full-Scale Mine Burial Experiments in Wave and Current Environments and Comparison With Models

A mine burial field experiment was carried out on two sandy seafloors between January and April 2004 in the Bay of Brest, France. Burial recording mines (BRMs) were used to measure burial and mine orientation at 15-min intervals. Sonar and bottom photographs were also used to characterize sediment morphology and mine burial. These observations are compared with the predictions of mine burial using the following three models: a momentary liquefaction model, a current-induced scour model, and a wave-induced scour model. Analysis combines mine burial data, sediment data, seabed observations, and hydrodynamic measurements. At the first site, ldquoRascas,rdquo the seabed dynamics are dominated by tides and river runoff. Almost no mine burial was measured during the experiment which is in agreement with predictions of mine burial models (current-induced scour and liquefaction). Dynamics at the second site, ldquoBertheaume,rdquo are driven by tides and ocean waves. A long storm (one week) and several swell events were experienced and significant mine burial was observed in conjunction with high significant waveheights. Mine burial models suggest that burial at ldquoBertheaumerdquo was dominated by wave-induced scour rather than current-induced scour or momentary liquefaction.

The Revival of Prehistoric Burial Practices: Three Archaeological Experiments

The article presents the results of three burial experiments, carried out in 2005, the aim of which was to attempt to understand what exactly hap- pens to a physical body after death in different environments. The experiments were simulations of an open air burial, a stone cist burial and a cremation, for which the dead bodies of a calf and pigs were used. Next to technical documen- tation, the emotions and impressions of the experiment participants during the observations of body decomposition and the cremation process were recorded. The authors suggest that a cognitive approach to burial experiments could offer us an alternative view to understanding rituals and interpreting prehistoric burials. Bystanders often find it amazing how archaeologists constantly aspire to re- construct societies consisting of complex human relationships and versatile behavioural patterns on the basis of mute artefacts. The nature of funerary practices, ritual systems, Weltanschauung and religion is surmised on the ba- sis of the structure of burial places, extant skeletons and grave goods. In addi- tion to analysing the funerary rituals and religion, burial material has been employed in researching the clothing, weaponry, and other mundane problems of the everyday life. In fact, archaeology has few means of its own for making interpretations. It is impossible to observe objects in the process of creation or use and there is nobody to ask from how, why and for which reason have cer- tain objects been created or used. This is why archaeologists have relied on theories posed by anthropologists, sociologists, theologians, and other schol- ars of various fields which study modern living societies. The ambiguity of selection criteria, however, renders the popularity of certain theories and the adaptation of theories rather arbitrary. In scholarly research of prehistory, authors are increasingly favouring ex- perimental archaeology as a method for defining ways of interpretations. Ex- perimental archaeology enables scholars to arrive at an understanding through

Mine Burial Experiments at the Martha's Vineyard Coastal Observatory

Several experiments to measure postimpact burial of seafloor mines by scour and fill have been conducted near the Woods Hole Oceanographic Institution's Martha's Vineyard Coastal Observatory (MVCO, Edgartown, MA). The sedimentary environment at MVCO consists of a series of rippled scour depressions (RSDs), which are large scale bedforms with alternating areas of coarse and fine sand. This allows simultaneous mine burial experiments in both coarse and fine sand under almost identical hydrodynamic forcing conditions. Two preliminary sets of mine scour burial experiments were conducted during winters 2001-2002 in fine sand and 2002-2003 in coarse sand with a single optically instrumented mine in the field of view of a rotary sidescan sonar. From October 2003 to April of 2004, ten instrumented mines were deployed along with several sonar systems to image mine behavior and to characterize bedform and oceanographic processes. In fine sand, the sonar imagery of the mines revealed that large scour pits form around the mines during energetic wave events. Mines fell into their own scour pits, aligned with the dominant wave crests and became level with the ambient seafloor after several energetic wave events. In quiescent periods, after the energetic wave events, the scour pits episodically infilled with mud. After several scour and infilling events, the scour pits were completely filled and a layer of fine sand covered both the mines and the scour pits, leaving no visible evidence of the mines. In the coarse sand, mines were observed to bury until the exposed height above the ripple crests was approximately the same as the large wave orbital ripple height (wavelengths of 50-125 cm and heights of 10-20 cm). A hypothesis for the physical mechanism responsible for this partial burial in the presence of large bedforms is that the mines bury until they present roughly the same hydrodynamic roughness as the orbital-scale bedforms present in coarse sand.

Mine-Impact Burial Model (IMPACT35) Verification and Improvement Using Sediment Bearing Factor Method

Recently, a 3-D model (IMPACT35) was developed to predict a falling cylindrical mine's location and orientation in air-water-sediment columns. The model contains the following three components: 1) triple coordinate transform, 2) hydrodynamics of falling rigid object in a single medium (air, water, or sediment) and in multiple media (air-water and water-sediment interfaces), and 3) delta method for sediment resistance with the transient pore pressure. Two mine-impact burial experiments were conducted to detect the mine trajectory in water column [Carderock Division, Naval Surface Warfare Center (NSWC), West Bethesda, MD, on September 10-14, 2001], and to measure the mine burial volume in sediment (Baltic Sea in June 2003). The existing IMPACT35 predicts a mine's location and orientation in the water column, but not in the sediment column. Since sediment resistance largely affects the mine burial depth and orientation in sediment, a new method (bearing factor) is proposed to compute the sediment resistant force and torque. The improvement of IMPACT35 with the bearing factor method is verified using the data collected from the Baltic Sea mine-impact burial experiment. The prediction error satisfies near-Gaussian distribution. The bias of the burial volume (in percent) prediction reduces from 11% using the delta method (old) to 0.1% using the bearing factor method (new). Correspondingly, the root-mean-square error (rmse) reduces from 26.8% to 15.8%.

High-Resolution Mapping of Mines and Ripples at the Martha's Vineyard Coastal Observatory

High-resolution multibeam sonar and state-of-the-art data processing and visualization techniques have been used to quantify the evolution of seafloor morphology and the degree of burial of instrumented mines and mine-shapes as part of the U.S. Office of Naval Research (ONR, Arlington, VA) mine burial experiment at the Martha's Vineyard Coastal Observatory (MVCO, Edgartown, MA). Four surveys were conducted over two years at the experiment site with a 455-kHz, Reson 8125 dynamically focused multibeam sonar. The region is characterized by shore-perpendicular alternating zones of coarse-grained sand with 5-25-cm-high, wave orbital-scale ripples, and zones of finer grained sands with smaller (2-5-cm-high) anorbital ripples and, on occasion, medium scale 10-20-cm-high, chaotic or hummocky bedforms. The boundaries between the zones appear to respond over periods of days to months to the predominant wave direction and energy. Smoothing and small shifts of the boundaries to the northeast take place during fair-weather wave conditions while erosion (scalloping of the boundary) and shifts to the north-northwest occur during storm conditions. The multibeam sonar was also able to resolve changes in the orientation and height of fields of ripples that were directly related to the differences in the prevailing wave direction and energy. The alignment of the small scale bedforms with the prevailing wave conditions appears to occur rapidly (on the order of hours or days) when the wave conditions exceed the threshold of sediment motion (most of the time for the fine sands) and particularly during moderate storm conditions. During storm events, erosional ldquowindowsrdquo to the coarse layer below appear in the fine-grained sands. These ldquowindowrdquo features are oriented parallel to the prevailing wave direction and reveal orbital-scale ripples that are oriented perpendicular to the prevailing wave direction. The resolution of the multibeam sonar combined with 3-D visualization techniques provided realistic looking images of both instrumented and noninstrumented mines and mine-like objects (including bomb, Manta, and Rockan shapes) that were dimensionally correct and enabled unambiguous identification of the mine type. In two of the surveys (October and December 2004), the mines in the fine-grained sands scoured into local pits but were still perfectly visible and identifiable with the multibeam sonar. In the April 2004 survey, the mines were not visible and apparently were completely buried. In the coarse-grained sand zone, the mines were extremely difficult to detect after initial scour burial as the mines bury until they present the same hydrodynamic roughness as the orbital-scale bedforms and thus blend into the ambient ripple field. Given the relatively large, 3-D, spatial coverage of the multibeam sonar along with its ability to measure the depth of the seafloor and the depth and dimensions of the mine, it is possible to measure directly, the burial by depth and burial by surface area of the mines. The 3-D nature of the multibeam sonar data also allows the direct determination of the volume of material removed from a scour pit.

Exercising a Deterministic Mine Burial Prediction System for Impact and Scour Burial Using Operational Data Sets

This paper presents results and analysis from exercising an aquatic mine burial prediction (MBP) system based on deterministic models to simulate impact and scour burial experiments using operational or operational-like inputs. Based on nonparametric hypothesis testing of simulation results with empirical data, the statistics generated from simulations of impact burial appear to provide useful predictions and uncertainty estimates when the simulations account for geotechnical variations. For scour burial, the use of the simulating waves nearshore model to drive a scour model is examined. Model predictions qualitatively followed empirical burial trends, with variations in waveheight prediction appearing to be a more significant factor in determining the accuracy of the scour burial prediction than uncertainty in grain size. Overall, the tests provide encouragement for the use of new MBP models to provide reasonable predictions of burial from operational input data.