Marine sediments biodegradation

Table 3-1 Electron acceptors that are used in the biodegradation of organic material in marine sediments. More on the chemistry of these processes is presented in Chapters 8 and 16...

Surfactants such as LAS and NPEO have been found in compartments with low oxygen content, such as anaerobic sludge digesters or anaerobic continental and marine sediments [14,15,18-25]. One of the possible causes of this persistence is the inhibition of the anaerobic digestion [17,26,27]. Battersby and Wilson [27] observed inhibitory effects of NP at 50 mg CL-1 on methane formation in a survey of the anaerobic biodegradation potential of organic chemicals in digesting... 

However, as far as we know, the distribution of LAS biodegradation intermediates according to depth in the sediment column has been determined only in marine sediments [58]. This study was performed in a saltmarsh channel (Sancti Petri Channel, Cadiz Bay, Spain), receiving untreated urban wastewater effluents. In this zone the benthic organisms are very scarce [59], and the capacity for irrigation of... 

Roberts, D.J., Rabke, S. and Bernier, R. (2005) Evaluation of marine sediment qualities and their effect on the marine closed bottle test for testing biodegradability of synthetic drilling mud base fluids. SPE 94430 SPE/EPA//DOE Exploration and Production Environmental Conference 7-9 March 2005, Galveston, TX. Society of Petroleum Engineers, Richardson, TX, pp. 7. 

Melcher, R. J., Apitz, S. E. Hemmingsen, B. B. (2002). Impact of irradiation and polycyclic aromatic hydrocarbon spiking on microbial populations in marine sediment for future aging and biodegradability studies. Applied and Environmental Microbiology, 68, 2858-68. 

Monomers, plastics adhesives and resins are consequences of the production and use of polymers. They have a strong environmental impact in waters and soils due to their low biodegradability. It is very common to find plastic residues in marine sediments, soils, seashores, lakes, and rivers. Furthermore, some of the monomers used in their production are volatile and toxic (e.g., acrylamide, isocyanates, and vinyl chloride). 

The ohgomeric distribution of NPEO depends on the enviromnental compartment. In this respect, the dissolved phase of waters (seawater and wastewaters) contain higher ethoxamers, whereas river and marine sediments oidy contain nonylphenol and the lower oligomer derivatives (Fignre 4). Nonylphenol and its low-ethoxylated components have been identified in mechanical-biological sewage treated and in some biodegradation experiments", so that its preferential occurrence in the sediment may be due to these effects and/or to their preferent association to the particnlate material. 

Jones D.M., Douglas A.G., Parkes R.J., Taylor J., GigerW., Schaffner C. (1983) The recognition of biodegraded petroleum-derived aromatic hydrocarbons in recent marine sediments. Mar. Pollut. Bull. 14, 103-8. 

Rontani J.-F., Bonin P., Volkman J.K. (1999) Biodegradation of free phytol by bacterial communities isolated from marine sediments under aerobic and denitrifying conditions. Appl. Environ. Microbiol. 65, 5484—92. 

Unlike xenobiotic substrates, biopolymers such as cellulose have been in the eco-system for a very long time, allowing the evolution of efficient enzymatic pathways specific for the breakdown of these substrates. Common biopolymers therefore readily undergo biodegradation in a wide variety of environmental conditions ranging from aerobic compost heaps to anoxic deep-sea marine sediments. 

Chitin that occurs in the exoskeleton of invertebrates (such as mollusks and arthropods) is composed of N-acetyl-D-glucosamine residues linked by 1,4 /3-Iinkages. A partially deacetylated chitin also occurs naturally as chit-osan. Microbial species responsible for the breakdown of chitin and chitosan have not been comprehensively studied. Micro-organisms found in a variety of environments (for instance, in fresh water [29], marine sediment [30], garden soil [31], and even anaerobic environments [32]) are known to produce chitinases and/or chitosanases. Table 56.1 shows a listing of some reported species of bacteria and fungi that yield these enzymes and are therefore, able to biodegrade these polysaccharides. 

Summary This American specification establishes the performance requirements for biodegradation of plastic materials and products, including packaging, films, and coatings. The marine environment includes conditions of aerobic marine waters or anaerobic marine sediments, or both. This specification establishes the requirements for biodegradation of plastic materials that have rates that are similar to known compostable materials. The specification also specifies that the degradation of the plastic materials will not cause any harm to sea life or habitat. 

ASTM D7081 covers biodegradation of plastic materials (including packaging materials and coatings) in marine environments (aerobic sea water and/or anaerobic marine sediments. The standard allows for shallow and deep saltwater as well as brackwater as possible environments. Currently, there is no comparable ISO standard. 

Sediment desorption t,/2 = 42.4 d from sediment under conditions mimicking marine disposal (Zhang et al. 2000). Soil biodegradation rate constant k = 0.0024 d with t,/2 = 294 d for Kidman sandy loam soil, and k = 0.0033 d with t,/2 = 211 d for McLaurin sandy loam soil (Park et al. 1990) ... 

Although the marine environment can generally be considered the final destination of industrial and urban wastewater effluents, studies of biodegradation of linear alkylbenzene sulfonates (LAS) in this compartment have been scarce until recently [1—8]. The removal of LAS from the marine medium seems to be an efficient process, as shown by the low levels of LAS detected in samples of both water and sediment [9—11]. High values have only been found in zones close to the direct wastewater effluent discharge points of urban areas [11]. 

The presence of suspended solid materials increases the extent of LAS biodegradation [13,28], but the rate of the process remains invariable. The influence of the particulate material is due specifically to the increased density of the microbiota associated with sediments. However, suspended solids may also reduce the bioavailability of IAS as a result of its sorption onto preferential sites (e.g. clays, humic acids), although this is a secondary effect due to the reversibility of the sorption process. Salinity does not affect IAS degradation directly, but could also reduce LAS bioavailability by reducing the solubility of this molecule [5], Another relevant factor to be taken into account is that biodegradation processes in the marine environment could be limited by the concentration of nutrients, especially of phosphorus and nitrogen [34],... 

The presence of surfactants and their biodegradation products in different environmental compartments can invoke a negative effect on the biota. The ecotoxicity of surfactants to aquatic life has been summarised in the scientific literature [1—5]. Nevertheless, some information is still lacking in relation to the aquatic toxicity of surfactants, especially knowledge regarding the toxicity of the degradation products, the effect of surfactants on marine species, the ecotoxicity of mixtures of chemical compounds with surfactants, the relationship between toxicity and chemical residue and the effect of surfactant presence in specific environmental compartments (water, particulate matter, pore-water, sediment). 

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