Allochthonous

According to the autochthonous, in situ theory of coal formation, peat beds and subsequently coal were formed from the accumulation of plants and plant debris in place. According to the allochthonous theory, the coal-producing peat bogs or swamps were formed from plant debris that had been transported, usually by streams or coastal currents, to the observed burial sites. 

Allochthonous flora Organisms that are not indigenous to the soil but that enter soil by precipitation, diseased tissues, manure, and sewage. They may persist for some time but do not contribute in a significant way to ecologically significant transformations or interactions. 

Marce R, Moreno-Ostos E, Lopez P, Armengol J (2008) The role of allochthonous inputs of dissolved organic carbon on the hypolimnetic oxygen content of reservoirs. Ecosystems 11 1035-1053... 

Miyake, T. (1988) Geology and mineralization of the Shimokawa mine an allochthonous ridge-type massive sulfide ore deposit. Mining Geology, 38, 215-232. 

Data Structures. Inspection of the unit simulation equation (Equation 7) indicates the kinds of input data required by aquatic fate codes. These data can be classified as chemical, environmental, and loading data sets. The chemical data set , which are composed of the chemical reactivity and speciation data, can be developed from laboratory investigations. The environmental data, representing the driving forces that constrain the expression of chemical properties in real systems, can be obtained from site-specific limnological field investigations or as summary data sets developed from literature surveys. Allochthonous chemical loadings can be developed as worst-case estimates, via the outputs of terrestrial models, or, when appropriate, via direct field measurement. 

Since 1916 the sedimentation rate, Region III of Figure 3, has averaged 644 g m-2 yr-1 or 0.3 cm yr 1 or about 5 times the pre-cultural rate. The diversion of the Cedar River (average flow of 20 m3 s 1 into the lake in 1916 provided the water necessary to operate the ship and canal locks and contributes an estimated 4-5 x 107 kg-yr-1 of allochthonous material, Crecelius [7]. This riverine sediment input would contribute to the greater... 

The geology of Cyprus is dominated by four distinct terranes - the Troodos Ophiolite Complex composed of mafic and ultramafic rocks, the Circum-Troodos Sedimentary Sequence containing calcarenites, siltstones and carbonates, the Mamonia Complex composed of igneous, sedimentary and metamorphic rocks and the Kyrenia Terrain containing a series of allochthonous massive and recrystallised limestones dolomites and marbles. These terranes generate highly varied landscapes (Fig 1). 

Most of the organic matter in seawater was created in situ by marine processes and is, hence, classified as autochthonous. Organic matter of nonmarine origin is classified as allochthonous and is primarily terrestrial detritus, transported by rivers or winds. The input of organic matter from rivers is small (0.4 Pg C/y) compared to primary productivity (40 to 50 Pg C/y). The aeolian input is unknown but thought to be significant. 

Allochthonous Formed outside the ocean. Opposite of autochthonous. 

Recent investigations provide new insight on the structural chemistry of dissolved organic matter (DOM) in freshwater environments and the role of these structures in contaminant binding. Molecular models of DOM derived from allochthonous and autochthonous sources show that short-chain, branched, and alicyclic structures are terminated by carboxyl or methyl groups in DOM from both sources. Allochthonous DOM, however, had aromatic structures indicative of tannin and lignin residues, whereas the autochthonous DOM was characterized by aliphatic alicyclic structures indicative of lipid hydrocarbons as the source. DOM isolated from different morphoclimatic regions had minor structural differences. 

Figure 1. Allochthonous and autochthonous sources of dissolved organic carbon in natural waters. (Reproduced with permission from reference 1. Copyright 1985 Kluwer Academic Publishers.)...

Mixture complexity must be minimized before structural studies can begin. One approach is fractionation of the mixture to concentrate and isolate the property of interest (5-7). An alternative is to study DOM found in environmental end-member systems. End-member environments are water bodies for which inputs of organic matter (allochthonous versus autochthonous) and climate (polar versus tropic) are homogeneous compared to those of most water bodies. The following research presents a fractionation of DOM isolated from end-member systems moderately definitive molecular models were derived. 

Correlation of Structure with Source. Allochthonous-derived DOM (8) was isolated from the Suwannee River at its origin in the Okefe-nokee Swamp in southern Georgia. The fiilvic acid fraction, which is responsible for the black coloration of the water, was extensively characterized (9). Several average molecular models based on quantitative analytical data were presented in that report (10) to denote the mixture characteristics of fiilvic acid. One model, modified to depict biochemical sources and based on quantitative analytical data (10), is presented in Structure 1. Other models of Suwannee River fulvic acid (based on lignins, terpenoids, tannins, and flavonoid sources) were previously proposed (II). 

Variation among Sampling Sites. Dissolved humic substance samples from seven end-member environments were isolated for study. Autochthonous inputs to DOM were expected to dominate in Big Soda Lake and in Island Lake, which is a groundwater-sustained eutrophic lake in the sandhills of western Nebraska. Allochthonous inputs to DOM from a swamp environment predominate in the Suwannee River. They also dominate in the Calcasieu River in western Louisiana, but the proportion of swampland is much lower there. The Temi River is a tropical blackwater tributary of the Orinoco River in Venezuela, where allochthonous inputs dominate. The entire Sagavanirktok River basin is located north of the tree line on the North Slope of Alaska a mixture of allochthonous and autochthonous inputs was expected for the various rivers and lakes in this basin. Lastly, Hidden Lake Creek, which is the outlet of Hidden Lake on the Kenai Peninsula of Alaska, was sampled to determine if nutrient inputs from decaying salmon were contributing to primary production and autochthonous inputs to DOM. 

The Sagavanirktok River is intermediate in aromatic carbon content. This river drains the bogs on the Arctic tundra (allochthonous inputs) and several lakes (autochthonous inputs). Samples from the Suwannee and Calcasieu rivers are very similar in peak-height ratios with the exception of peak 2 1 ratio, which is much lower for the Calcasieu River sample. The data in Table II indicate that the Calcasieu River fulvic acid has a greater ring content... 

The clear differentiation of allochthonous from autochthonous sources of DOM in integrating freshwater environments is not presently possible. 

Assuming a bulk density of 1.05 g/cm3 and a dry weight fraction of 0.1 for the interface sediment, 0.38 mm of sediment would supply the observed 160-m water-column burden of resuspended phases, approximately half the basinwide average annual linear sedimentation. The corresponding amount of sediment was consistent with the mass of allochthonous components in the water column during the March-May spring mixing period (200-300 mg/m3). The quantity of resuspended P was calculated as the product of mass of resuspended sediment (g/m2) and phosphorus concentration in surface sediment (mg of P/g). For a 160-m water column, the amount was 48 mg of P/m2 (25 mg of P/m2 for the mean water-column depth of 85 m). The resuspended P flux (25 mg of P/m2) was also obtained from the product of resuspended Al (mg/m2) and the P Al ratio in bottom sediment. 

On the other hand, a permanent supply of ferric oxides to the sediments is provided by sedimentation of allochthonous material. It is unknown to what extent these oxides are reactive with respect to sulfide or whether a predigestion of ferric oxides by bacteria is needed. Various studies indicate that 50% of freshwater sediment iron exists as iron oxide and 20% of the iron is reactive (72). Future studies should be directed to a better understanding of the existence of reactive iron. 

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