LIBRARY

Abstract
The acute toxicity of the dispersants Gold Crew, Nokomis-3, Atlantic-Pacific and Corexit 7664 on the Grass shrimp Palaemonetes pugio have been investigated, and the LC50 values have been determined using the Litchfield-Wilcoxon (1949) and Log concentration versus percent of survival methods. Experiments have been conducted at 17° C and 27° C for comparative purposes. Results have shown that there is a definite increase in toxicity with increasing temperature, that Corexit 7664 is of very low toxicity, that present dispersants are quite low in toxicity when compared with earlier ones and that the test animal P. pugio is quite resistant as supported by Welsh (1975)

Abstract
The effects of certain PHC derivates, dispersants and their combinations have been investigated on the mussel M. galloprovincialis Lamarck with the purpose of actually determining how PHC derivatives and certain dispersants react. The results have been presented as graphs

Abstract
An account is given of the Hamilton Trader oil spill off the NW coast of England, its movements, appearance of the oil at sea, biological effects and the action taken to disperse or remove the oil (Corexit 7664). As a result of the incident, the 1st in the area since the Ministry of Housing and Local Government and the Home Office issued their 1968 joint circular, initiating schemes for dealing with oil pollution, various recommendations are made for the future. Improvements are needed in early warning and communication, reconnaissance and slick tracking, liaison between local authorities and other organizations, in sampling and identification and in the allocation of responsibility for dispersal

Abstract
When oil spills onto coastal water of the United States or leaks reach the inland waters, an elaborate set of U.S. federal and state regulations comes into effect under the National Contingency Plan (NCP). Ironically, when an oil discharge is confined to land alone, very few regulations exist. Although spills on land are quite frequent, they do not arouse the news media or even local regulators, and the oil is often left in place. Dispersants, up to now not widely used, offer an economical and environmentally preferred option compared to other actions that might be taken. Although the use of dispersants for oil spills on land has never been regulated under the NCP, spillers have been reluctant to use them on land as a result of the possible rainfall runoff into controlled waters. Under the NCP (Subpart H) revised as of 20 Nov. 1985, however, the attributes of a dispersant on land can now be considered along with the existing techniques of burning, plowing under, or hauling away. Dispersants specifically formulated for use on contaminated soil have been on the market for over ten years. The first criterion for such a dispersant is that it must be compatible and effective with freshwater. Many of the most common dispersants on the market are for use on saltwater only. Other dispersant characteristics to be considered are emulsion stability and rapid biodegradability. Results of actual field experience on a wide variety of soil types, land uses, and topographies indicate that dispersant use on land can be effective

Abstract
A nearshore mesocosm experiment was set up to observe the fate of whole oil and chemically-dispersed oil. The dispersed treatment tank did not show signs of oil sorption, and little to no floating oil noted. Analysis of oil mass values between both tests indicated smaller amounts of oiled sediments in the dispersant test. The chemical dispersant was effective in reducing oil contamination in the nearshore environment

Abstract
An experiment was conducted at a wetland research facility, investigating the behavior of chemically dispersed oil (CDO) using an oil spill dispersant. The research site is located on the San Jacinto River near Houston, Texas. The experimental treatments included oiled control, “high dose” CDO (1:10 dispersant-to-oil ratio, DOR), “low-dose” CDO (1:20 DOR), as well as an unoiled control. Fourteen 5 m x 5 m plots were used for the experiment, four plots for each oiled treatment and two plots for the unoiled control. The treatments were assigned to plots using a randomized complete-block design. Twenty-one liters of Arabian medium crude oil was applied systematically to each plot. For the CDO treatments, the premixed dispersant-plus-oil solution was first added to containers of river water (either 1:10:200 or 0.5:10:200 dispersant-oil-water ratios), and the resulting solution was applied systematically to the respective plots. This method of CDO application was designed to simulate the movement of a dispersed-oil plume into a wetland environment. Sediment samples were taken over a 99-day period, using a 5-cm diameter-coring device. The GC-MS results for both target saturate and target aromatic hydrocarbons were normalized to 17α, 21ß-(H)hopane to separate biotic and abiotic removal mechanisms and to minimize spatial heterogeneity. Target compound analyses indicated no significant differences in the biodegradation rates for the three oil treatments. There were, however, significant differences in the amount of oil initially flushed (physical removal) from the plots of both CDO treatments as compared to the oiled-control treatments

Abstract
A dispersant effectiveness experiment was carried out at a wave-tank facility in Corpus Christi, TX. A known volume of weathered Arabian medium crude oil was applied to the water surface and the dispersant was systematically applied in an aerosolized form (1:10 dispersant/oil ratio). In a 24-hour period, samples were collected at 0, 0.5, 2, 4, and 24 h. A mass balance on the oil was used to quantify dispersant effectiveness. After 4 h, more than two-thirds of the oil was determined to be in the water column. After 24 h, a large portion of the dispersed oil had resurfaced

Abstract
An experiment was conducted at a wetland research facility, investigating the behavior and effects of chemically dispersed oil (CDO) using an oil-spill dispersant. The research site is located on the San Jacinto River near Houston, TX. The replicated treatments included oiled control, "high-dose" CDO (1:10 dispersant-to-oil ratio (DOR)), "low-dose" CDO (1:20 DOR), as well as an unoiled control. Known amounts of oil or dispersed oil were added to the respective plots. Sediment samples were taken over a 99-day period using a 5-cm-diameter coring device. The GC/MS results for both "total target saturate hydrocarbons" and "total target aromatic hydrocarbons" were plotted over time and data were modeled using nonlinear regression. The overall (including abiotic and biotic) petroleum loss rates for the dispersed-oil treatments were not statistically different when compared to the oiled control. However, the initial concentrations for the dispersed-oil treatments were statically lower (95% confidence) than for the oiled control. From this, it can be inferred that the dispersed oil was more prone to flush off the sediments, as was visually observed. Biodegradation rates were also determined for all treatments; it was concluded that there were no differences when comparing each dispersed-oil treatment to the oiled control. The sediments from each plot were also analyzed for microbial population numbers (most-probable-number) and acute toxicity (Microtox® 100% Test). Statistical analyses for both sets of data found no significant differences for the dispersed-oil treatments when compared to the oiled control

Abstract
To investigate the use of dispersants as an oil spill chemical countermeasure in the surf-zone, a simulated oil spill was conducted at the Shoreline Environmental Research Facility (SERF), formerly known as the Coastal OilSpill Simulation System (COSS), a wave tank facility in Corpus Christi, Texas. Sand was added to each tank to establish a beach with a prescribed slope of 10 degrees. Natural seawater flowed continually through the system to emulate alongshore currents. The replicated experimental treatments included pre-mixed oil plus dispersant (three tanks), oil only (three tanks), and unoiled controls (two tanks). Known amounts of either whole oil or dispersed oil were added to the respective tanks. Both the sediment and water column were periodically sampled during the 10-day experiment, and a materials balance on the oil was determined for both oil treatments. The environmental compartments where oil accumulated were sediments, water column, and non-aqueous-phase layer. The discharge from the tanks was presumed to be the primary sink, as water was drawn from the tanks at a known and constant flow rate. Tidal cycles were simulated by varying the computer-controlled influent rate. The oil mass (measured as total petroleum hydrocarbons) for each compartment/sink was calculated using data from four time points. At the experiment’s conclusion, approximately 49% of the applied oil for the oiled treatment remained in the tanks sorbed to sediments or other surfaces. The rest of the oil was removed via the effluent. In the chemically-dispersed oil treatment, all of the oil was flushed from the tanks; no oil (

Abstract
In 1981, an oil spill field experiment in Maine assessed the effects to the benthos of dispersant used in nearshore oil spills. Three test plots, each 60 by 100 m, were set up, each with an upper and a lower intertidal sampling area. There were also five subtidal sampling stations in water depths from 5 to 20 m. One plot was exposed to 945 L (250 gal) of Murban crude oil released on an ebbing tide within containment booms and cleaned up by conventional mechanical methods 24 h later. A second plot was exposed to 945 L of Murban crude oil premixed with 94 L (25 gal) of a widely available self-mix nonionic dispersant. The dispersant-treated oil was discharged over a 2-h period around high water slack tide. During discharge, mixing gates augmented natural energy to provide a worst-case scenario for exposure of the benthos to the complete dispersal of a nearshore oil spill. During and after discharge, dispersed oil in water was monitored fluorimetrically. Total integrated exposure of dispersed oil to the bottom at both upper and lower sampling areas was 30 to 40 ppm·h. Discrete water samples were also taken for other analyses. Dispersed oil in water reaching the bottom had lost most of the hydrocarbons more volatile than n-C17 compared with dispersed oil in water sampled at the same time near the surface. Petroleum retention by intertidal sediments and bivalves measured one week after the spill was less in areas exposed to dispersed oil than in areas exposed to untreated oil

Abstract
As part of the American Petroleum Institute sponsored tidal area dispersant project involving two test spills of Murban crude oil in Long Cove, Searsport, Maine in August, 1981, water samples were collected. This paper deals with the analytical results for the analyses of water samples collected for analysis of non-volatile hydrocarbons by: infrared spectrophotometric quantitation of total CCl4 extractables, and gravimetric analysis of aliphatic and aromatic hydrocarbon fractions followed by capillary gas chromatography. In the dispersant-treated oil discharge area, there were two primary water sampling locations during the discharge phase of the experiment: an upper intertidal area (maximum depth + 2 meters) and a lower intertidal area (maximum depth + 3.5 meters), the gas chromatographic data for the water samples were treated numerically to obtain parameters whose values reflect the extent of dispersed oil weathering. For the aliphatics, the peak area ratio for n C14/n C18 was calculated for each sample. For the aromatics, the ratio for the peak area sum of the mono, di, and trimethyl naphthalenes to that for the mono, di, tri, and tetramethyl dibenzothiophenes was determined for each sample. At both sampling locations, dispersed oil in water sampled 10 cm off the bottom consistently had a smaller fraction of lower boiling aliphatic and aromatic hydrocarbons than water sampled at the same place and the same time ½ meter below the surface. In addition, the data show that there is a 12-50 fold decrease in hydrocarbon concentration on going from near surface to near bottom at any given time, even in water as shallow as 2 meters. The data indicate that the primary mechanism for hydrocarbon loss involves volatilization of hydrocarbon fractions. Analysis of water samples taken from submerged plumes of dispersed oil outside the sampling areas demonstrated slower loss of low boiling components consistent with the importance of atmospheric exchange in the weathering process. In the chemical dispersal of an oil spill, it may be the most advantageous to use mixing methods that minimize vertical mixing in order to maintain a high concentration of emulsified oil in the upper ½ meter water layer. This will maximize the extent of loss of lower boiling hydrocarbon components into the atmosphere and thus minimize the toxicity of any dispersed oil fractions that diffuse downward and interact with benthic communities

Abstract
The fate and effects of two nearshore discharges of Murban crude oil at Long Cove, Searsport, Maine in August 1981 were studied following a one-year, pre-spill baseline study of the test areas. An upper and a lower intertidal sampling area within a 60 x 100 meter test plot were exposed to dispersed oil in water resulting from the discharge of 250 gallons of oil pre-mixed with 25 gallons of Corexit 9527 dispersant. Release of treated oil was around high-water slack tide on the surface of the water, with added mixing energy provided by mixing gates deployed by small boats. The maximum water depth over the test areas was 3.5 meters. Untreated crude oil (250 gallons) was released on an ebbing tide within a separate, boomed-off 60 x 100 meter test plot. A third test plot served as an oil-free reference plot. Water samples taken near the surface and near the bottom during and after discharge showed that chemically dispersed oil loses lower boiling hydrocarbons in both the aliphatic and aromatic fractions below n-C17 as the droplets diffuse downward. Data are given for sediment samples taken from the test plots 11 months pre-spill and 10 months post-spill. Hydrocarbon analyses of the sediment samples show little incorporation of dispersed oil into the sediments of the treated oil plot relative to the sediments exposed to undispersed oil

Abstract
The sublethal effect of dispersants, oil and mixtures of oil and dispersants on the shrimp P. serratus can be estimated at the level of the gill ATPase activity. The exposure of shrimps to sublethal concentration of pollutant results in an inhibition of the gill Na+ K+ Mg++ ATPase and a modification of the kinetic properties of the system. This result suggests that an alteration of the membrane binding of the enzyme induces a modification of the enzyme function. The sublethal test designed from the inhibition of the enzyme activity allows the estimation of the safe concentration

Abstract
The sublethal effect of dispersants and mixtures of oil and dispersants on the gills of P. serratus can be detected by light microscopy. The observation by light microscopy revealed cellular damage of gills: deterioration of the membrane and difficulties of blood circulation

Abstract
Three experimental ecosystems were employed to test the effect of Corexit 9527, with and without Prudhoe Bay crude oil, on the ecology of a temperate pelagic ecosystem. The results indicated that Corexit 9527 alone enhanced biological productivity without changing the structure of the ecosystem. The mixture of Corexit and crude oil caused a major change in the ecology of the ecosystem which resulted in large numbers of bacteria and zooflagellates, but a depression of all other zooplankton phyla

Abstract
Dispersant toxicity testing protocols from around the world were reviewed. The following sources were used to update published information on international testing requirements: 1) The 1989 international review by the National Research Council on dispersant toxicity testing programs; 2) Exxon oil spill response coordinators in various countries; 3) Other documents, protocols, and scientific papers dealing with dispersant toxicity testing requirements; 4) Pollution control agencies or related government entities in various countries

Abstract
Since 1978, dispersant use guidelines have been developed and implemented for regional response teams (RRTs) in standard federal Regions IX and X, to enhance the RRT 's ability to respond rapidly to requests to use dispersants. The guidelines define the data necessary to give approval. These data include physical, chemical, and biological parameters associated with spilled oil and dispersants. A decision to use dispersants is based on balancing the economic, social, and natural resource costs associated with oil spills. Damages expected from spills not treated with dispersants are compared to damages expected if the oil is treated. The objective of the guidelines is to help minimize the damage to natural resources. Specific criteria were developed by the RRTs as minimum standards for documentation of dispersant application, including the recording of dispersant type and application rates, visual observation of dispersant effectiveness, and monitoring environmental impacts. This paper summarizes the progress of two RRTs in responding to requests for dispersant use, developing dispersant guidelines, and recommending minimum standards for documentation. Physical, chemical, and biological factors used in the decision process are also reviewed. Finally, the paper discusses the importance of resource protection and monitoring

Abstract
Since the early 1970s both the effectiveness and efficiency of oil spill dispersants have been improved while the toxicity of these chemicals has been reduced. Although a large body of research has been published in the last five years which supports these claims, there has been little experience with the use of dispersants in the United States. The lack of experience has been created, in part, by a cumbersome dispersant approval process and the reluctance of spill responders to invest in dispersants and related application equipment. The Region IX Regional Response Team has identified four prerequisites for effective use of dispersants: informed decision-makers; a functional decision-making process; coordinated contingency plans; and effective, region-specific application capabilities. This paper explores the approach taken by government and industry to fulfill these prerequisites. The goal of these efforts, which include sponsoring workshops, implementing a dispersant application test program, and requiring specific dispersant contingency planning efforts, is to fully integrate dispersants into the oil spill control efforts of the region

Abstract
In reference to sublethal toxicity, one important criterion for the ecotoxicological assessment of any compound is its susceptibility to metabolism by target and non-target organisms. There is presently little information to indicate that aquatic organisms can degrade the active surfactant ingredients found in commercial oil dispersant formulations. A colorimetric method for the detection of free fatty acids was adapted to assay esterase activity with polyethoxylate fatty acid ester substrates. It was possible with this method to demonstrate that a representative teleost, crustacean and mollusc have the capacity for enzymatic hydrolysis of the complex fatty acid ester mixtures found as surfactants in the "new" generation oil spill dispersants

Abstract
The natural oil seeps off Coal Oil Point (Santa Barbara), California, release an estimated 100-150 bbl of oil per day to the marine environment. This project proposed to conduct a series of dispersant trials using these seeps to intercalibrate NOAA’s Scientific Monitoring of Advanced Response Technologies (SMART) UV/Fluorescence-based protocols with finite measurements of dissolved aromatics and dispersed oil droplets in the water column and to evaluate a unique oil-boom/dispersant-application technology (NeatSweep). Following an elaborate and lengthy permitting process including cooperation from multiple regulatory agencies and organizations, laboratory tests indicated that although fresh produced oil from nearby Platform Holly could be treated (>70% effectiveness) dispersing the weathered 11° API gravity seep oil was totally ineffective (0%). Limited field tests then verified the laboratory findings that the seep oil could not even be dispersed with Corexit 9500, a commonly used dispersant for heavily weathered and viscous oils. Lacking reasonable alternatives, (including the use of intentional spills), the project was halted before full-scale field implementation. This paper documents the development of the research plan, the steps required to obtain the necessary permits, and the results from the limited laboratory and field tests that were completed. The planning and permitting efforts for this project are provided so that others with similar needs or goals might benefit. A brief discussion is provided on the limitations of using natural seep oils for spill response research and on the difficulties with spill-of-opportunity research during actual spill events. The importance of controlled experimental discharges of oil is discussed along with the pros and cons of such deliberate spills

Abstract
Four commercially available oil dispersing agents, Corexit 9550, Finasol OSR-7, EC. O ATLANT'TOL AT-7, and OFC D-609, were evaluated for dispersion effectiveness under low temperature-low salinity conditions. Percent dispersion of an EPA-American Petroleum Institute standard reference oil (Prudhoe Bay crude oil) was measured under controlled conditions (temperatures: 1°C and 10°C; salinity: 0 parts per thousand [ppt], 18 ppt, and 33 ppt) using the revised standard EPA protocol. Mean initial (at 10 minutes) and final (at 2 hours) percent dispersion data are presented for each of the tested dispersants. Corexit 9550 was the most effective of the four dispersants tested at a salinity of 0 ppt; mean initial dispersion efficiencies exceeded 50 percent for dispersant: oil ratios of 0.25 at 1°C, but were slightly lower (42 percent) at 10°C. Mean initial percent dispersions of 48 percent and 34 percent were obtained at 0°C for dispersant:oil ratios of 0.1 and 0.03 respectively. OFC D-609 was relatively more effective than Corexit 9550 at 18 ppt, 1°C and 10°C, and at most of the measured dispersant:oil ratios, whereas D-609 and Corexit 9550 were equally effective under 33 ppt conditions. Dispersants AT-7 and OSR-7 were significantly less effective than either Corexit 9550 or D-609 for most of the laboratory test conditions

Abstract
The release of 3.9 million gallons of Angola Planca crude oil from the stricken tanker Mega Borg 57 miles offshore of Galveston, Texas in June 1990 provided a valuable opportunity to document dispersant effectiveness under field conditions. Aerial (C-130 transport) application of Corexit 9527 (968 gallons total in four adjacent passes) onto an identified test portion of the slick was evaluated by concurrent observations from a command-and-control aircraft and surface vessels (with videotape and 35-mm photographic documentation) and ground truth measurements, including continuous 4-meter-depth ultraviolet/fluorescence and a discrete water sampling program. Using the study plan outlined by Payne and colleagues, target and control areas were designated before dispersant application by deployment of smoke bombs and coded three-meter drogues. Postdispersant surface vessel placement and 30 liter water sampling activities from the Texas A&M research vessel HOS Citation were aided by the smoke bombs, the free-drifting drogues, and directions from the command-and-control aircraft. Subsequent FID GC and GC/MS analyses of water sample extracts allowed quantitation of the dispersed oil concentrations under both treated and control areas. Although the spilled oil was extremely light (API gravity 39.0) and subject to significant natural dispersion, the field observations, filmed documentation, and water column data clearly demonstrated an increase in dispersed oil concentrations beneath the treated slick. The distribution of dispersed oil droplets was very heterogeneous and reflected the patchy distribution of oil on the water surface before dispersant application. Maximum concentrations of dispersed hydrocarbons in the center of the treated zone were 22,000 µg/L (22 ppm) for total aliphatics and 5.6 µg/L (5.6 ppb) for total aromatics 60 to 90 minutes after dispersant application. Elevated levels were generally limited to the upper 1 to 3 meters of the water column. Concentrations in the upper 1 to 3 meters of the control zones (Stations 102-107 and 135) were significantly lower, at 1.2 to 3.9 ppm and at 0.8 to 1.7 ppb for total aliphatic and aromatic hydrocarbons, respectively. The 9-meter dispersed aliphatic hydrocarbon concentrations in both the treated and control areas appeared to very similar (2.5-2.7 ppm), suggesting a background, steady-state concentration of very fine, physically-dispersed oil droplets from six days of natural slick dispersion before the test. The data on ratios of aliphatic and aromatic concentrations (2,133:1 and 2,875:1 in the control and treated zones, respectively) showed no evidence significantly enhanced dissolution of lower-and intermediate-molecular-weight aromatics as a result of chemical dispersion. To the best of our knowledge, these water-column-concentration-based data represent the first documented evidence of dispersant effectiveness at a spill of opportunity in United States waters. As in previous dispersant trials under similar conditions, communications during the test applications (between the command-and-control helicopter, the U.S. Coast Guard H-3 helicopter deploying the smoke bombs, the spotter aircraft directing the C-130 for dispersant applications, and both surface sampling and observation vessels) were discontinuous and difficult at best. This is the one area which still requires the most improvement for coordinating future dispersant trials, should they be attempted. Furthermore, because of the significant lead time and logistics required to execute such trials successfully, we do not recommend that they be made a requirement for emergency-response-mode implementation of dispersant applications at oil spills in the future

Abstract
Fuel oil released from the sinking of the PAC Baroness off Point Conception, California, was used as a spill of opportunity to study dispersant application technology and evaluate remote sensing methods used to track the slick. Forty-one gallons of the dispersant Corexit 9527 were applied by helicopter to a l00-m-by–700-m portion of the slick on 29 September 1987. Photographic documentation of the spill’s behavior was completed from a U.S. Coast Guard H-3 helicopter and the U.S. Coast Guard AirEye Falcon Jet was used for side-looking airborne radar (SLAR) coverage from an altitude of 5,000 ft and IR/UV scans from 400 ft. Continuous subsurface UV fluorescence measurements and grab samples of water beneath the slick were obtained from a support vessel before and after dispersant application. The results of the tests were somewhat equivocal, owing to the limited area and very thin nature of the slick combined with 15-to-20 knot crosswinds, which caused breakup of both treated and control areas. Photographs showed a subtle difference between the head of the slick (original subsurface source) and the treated area 200 m downcurrent, but the breakup of the oil due to the crosswind as the slick moved downcurrent precluded differentiation between the treated area and the untreated control area 700 m from the source. The SLAR data were of limited value because of the resolution of technique and the extremely small area treated. The aerial UV scans did suggest a change in the slick behavior in the treated area; however, the ground-truth UV fluorescence measurements and subsequent chemical analyses did not indicated enhanced subsurface concentrations of dispersed oil. Attempts to complete another series of tests on 1 and 2 October 1987 were thwarted by adverse weather conditions and the continuing decline of the amount of oil surfacing from the vessel. Suggestions are presented for improving dispersant trials at future spills of opportunity

Abstract
The physiological effects of a single ingested dose of Prudhoe Bay crude oil (PBC), its aromatic fractions, and PBC/Clorexit (sic) emulsion were studied in nestling herring gulls (Larus argentatus). The data showed that the high-molecular-weight aromatic compounds were responsible for retardation of growth and increases in adrenal and nasal gland weight. Little difference was found between PBC and the PBC/Clorexit (sic) emulsion although the latter did have a somewhat more marked effect on plasma sodium levels

Abstract
The effects of dispersants on both the exposure to and toxicity of oil to seabirds are considered in order to assess the hazard. Ideally the dispersant mixes with oil and disperses it into the water column. This process is rapid but generally incomplete. The toxicology of one dispersant (Corexit 9527), for which data are available, shows that the toxicity of oil-Corexit mixtures is similar to that of oil alone. The effect of two feeding regimes, pursuit diving and surface diving, is considered. Calculations indicate that the amount of oil that is likely to be taken up by the bird while moving through the water column is small. It is concluded that there is little evidence of synergistic effects between oil and dispersant. The major oiling of birds occurs at the surface and thus dispersants must be highly effective to reduce the exposure of birds to oil

Abstract
Authors describe a new type of oil spill treatment formula, made by reacting polyoxyethylenic surfactants, alkyl alcohols, or carboxylic acids with alkylchlorosilanes. The compound reacts with water, causing the chemical to encapsulate and solidify oil slicks. The material can then be removed from the water surface with netting. The material can be re-used by washing the solid material with dichloromethane

Abstract
Effects of dispersants on crude oil in cold seawater were studied in a mesoscale simulator under ambient air conditions. Oil droplets were dispersed in the water column and were rapidly biodegraded during the cold weather conditions experiment. However, bacterial activity was decreased by at least one order of magnitude in experiments conducted below an ice cover. Undispersed oil formed water-in-oil emulsions that were resistant to weathering processes. During winter, mousses that were trapped in ice were recovered almost unaltered three to four months later