Comparative terrestrial transport

Economic Aspects. To be useful the raw materials must be recoverable at a cost not greater than the cost of similar terrestrial materials. These costs must include transportation to the point of sale. Comparative costs of recovery are strongly influenced by secondary environmental or imputed costs, such as legal costs or compensatory levies. 

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. 

Some component of the terrestrial POM must be extremely nonreactive to enable a higher burial efficiency as compared to autochthonous POM. A possible candidate for this nonreactive terrestrial POM is black carbon. This material is a carbon-rich residue produced by biomass burning and fossil fuel combustion. Some black carbon also appears to be derived from graphite weathered from rocks. It is widely distributed in marine sediments and possibly carried to the open ocean via aeolian transport. 

Petroleum is an extremely complex mixture of hydrocarbons, which can be separated into liquid (oil) and gas fractions. Compared to coal, petroleum being a liquid is easier to transport. It probably originated in marine sediments, in contrast to the terrestrial origins of coal. 

Evidence from 6 C studies (Sackett, 1964 Nissenbaum and Kaplan, 1972) and studies of the offshore decrease of terrestrially derived lignin material (Gardner and Menzel, 1974 Hedges and Parker, 1976) have led investigators to conclude that only a minor fraction of terrestrial humic substances are transported beyond the estuaries. The approach these investigators took was to compare sediment ratios with lignin oxidation... 

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