Terrestrial transport from

A representation of the stratospheric system that shields terrestrial life from excessive solar ultraviolet radiation is presented in Figure 4. Our primary concern is the decrease of stratospheric ozone, most striking in the Antarctic, which has been linked to increases in CFCs from the troposphere, and the possible increased transport of these compounds between the stratosphere and the troposphere by increased temperature driven circulation. 

These models are too simple to reflect realistic dynamic properties of the carbon budget. Even so, they depend on data that are poorly measured or lacking. Many potentially important compartments are missing or assumed to be unimportant. For example, no model considers carbon transported from terrestrial systems to the oceans through rivers and streams. While the amount is very small, it is continuous and cumulative (25)... 

The freshwater cycle is an important link in the carbon cycle as an agent of erosion and as a necessary condition for terrestrial life. Although the amount of carbon stored in freshwater systems is insignificant as a carbon reservoir (De Vooys, 1979 Kempe, 1979a), about 90% of the material transported from land to oceans is carried by streams and rivers. 

Atmospheric deposition is an important source of mercury for surface waters and terrestrial environments that can be categorized into two different types, wet and dry depositions. Wet deposition during rainfall is the primary mechanism by which mercury is transported from the atmosphere to surface waters and land. Whereas the predominant form of Hg in the atmosphere is Hg° (>95%), is oxidized in the upper atmosphere to water-soluble ionic mercury, which is returned to the earth s surface in rainwater. In addition to wet deposition of Hg in precipitation, there can also be dry deposition of Hg°, particulate (HgP), and reactive gaseous mercury (RGM) to watersheds [9-11]. In fact, about 90% of the total Hg input to the aquatic environment is recycled to the atmosphere and less than 10% reaches the sediments [12]. By current consensus, it is generally accepted that sulfate-reducing bacteria (SRB)... 

Catchment Contributions. The slope of the regression lines in Figure 9 is the rate at which Hg is transported from the terrestrial catchment to the lake sediments (in units of micrograms of Hg per square meter of catchment per year). If one assumes that all of the Hg in the catchment is derived from the atmosphere, then the slope divided by the atmospheric deposition rate (the intercept) is the proportion of terrestrial Hg deposition that is transported to the lake. The slope will equal the rate of atmospheric deposition if the entire flux to the catchment is transported to the lake. On the other hand, the slope will equal zero—as observed for Pb by Dillon and Evans (18)—if direct deposition to the lake surface is the only significant source. 

If whole-basin accumulation rates for a substance are produced for multiple lakes in a geographic region, it is possible to use a simple mass-balance model to estimate both the atmospheric deposition rate and transport from the terrestrial catchment. The model was applied to both modern and preindustrial Hg accumulation in seven undisturbed lakes in the upper midwest... 

Non-Marine Sulfur Sources. Non-marine sources of atmospheric sulfur to the remote atmosphere require long distance transport from continental areas. The following section summarizes the isotopic data from anthropogenic, volcanic, and terrestrial biogenic sulfur sources. 

Some margins receive their terrestrial inputs from estuarine line-sources (numerous estuaries) with very little direct effects from rivers, while others may receive large direct inputs from rivers, such as deltaic regions these differences will have serious consequences on the amount of terrestrial material recycling that has occurred before entering the coastal zone, as well as how these materials (particulate and dissolved) will be transported offshore. 

The dust showers which at various times have fallen in Italy and Sicily frequently contain grains of metallic iron. Similar grains are found in the sands of the Sahara desert, and it is not improbable that the dust showers referred to are terrestrial phenomena, the sand being transported from the desert by cyclones.1 In numerous other places small grains of iron have been found, and a terrestrial origin is ascribed to the metal in all of these cases. 

Another source of metallic contamination in the studied region comes from the residual oil combustion used for electric utilities and fluvial and terrestrial transportation. Using the selected emission factors (quantity of trace element released by quantity of material consumed) given by Nriagu and Pacyna (1988) and Nriagu (1989), the electric-power production installed in the Amazonian states and the fuel consumption used for transportation (Ministerio de Minas... 

The amount and quahty of the organic matter dehvered to the sediment surface will determine the amount and form of the N remineralized from the sediment (e.g., Lomstein et al., 1989). A number of studies have shown a positive correlation between increases in OM dehvery to the sediment and N regeneration (Enoksson, 1993 Jensen et al., 1990 Sloth et al., 1995 Therkildsen et al., 1996 Tyler et al., 2001). The quality of organic matter is also important. For example, phytoplankton detritus would be expected to have a much lower C N ratio than seagrass detritus or organic matter transported from the terrestrial environment (e.g., Enriquez et al., 1993), such that more N regeneration would hkely occur as a result of phytoplankton detrital deposition relative to deposition of seagrass detritus. 

The mining of phosphate rock (mostly from terrestrially emplaced marine phosphorite deposits) for use as agricultural fertilizer has increased dramatically in the latter half of this century (F72). In addition to fertilizer use, deforestation, increased cultivation, urban and industrial waste disposal all have enhanced phosphorus transport from terrestrial to aquatic systems, often with deleterious results. For example, elevated phosphorus concentrations in rivers resulting from these activities have resulted in eutrophication in some lakes and coastal areas, stimulating nuisance algal blooms and promoting hypoxic or anoxic conditions harmful or lethal to natural populations (e.g., Caraco, 1995 Fisher et al., 1995 Melack, 1995). 

The major source of zinc in the troposphere over the ocean is the microbial zinc methylation in marine water (Craig, 1980). Additionally, abont 1 x 10 tons/year is related to dust-borne zinc transported from the land areas. Intnrn, 0.26 x 10 tons of air-borne zinc is transported annually from the ocean troposphere to the troposphere over terrestrial ecosystems and deposited there. 

As the chemical composition of the water changes, the amount of light energy available and the reactants available also changes. For example, terrestrial CDOM transported from a river into an estuary encounters a distinct change in the ionic composition of water due to increased salinity. This change in ionic composition may alter the solubility or conformation of certain C moieties and... 

Photosynthesis takes place mainly in the green leaves of terrestrial plants, but it occurs also in marine plants. The plants take carbon dioxide from the air and water is transported from the root to the leaves. 

In the hypothetical terrestrial system depicted in Fig. 14-4, the P eroded from the land is eventually transported to the estuaries. As in lakes, soils, and rivers, many chemical and biological processes act to control the transport of P within and from the estuary (Lucotte and d Anglejan, 1988 Jonge and Villerius, 1989). Dissolved P may be removed from solution onto the particulate phase and deposited in the sediments. On the other hand, the change in the solution composition may cause P to be released from the particulate load. The P that is transported from the estuaries to the ocean in particulate form will rapidly settle to the sea floor and be incorporated into the sediments. The dissolved P will enter the surface ocean and participate in the biological cycles. Determining what proportion of P that is transported out of the estuary is reactive is a critical step in the elucidation of the marine P budget (Froelich et al., 1982). 

Strontium, present in crustal materials, is released by the weathering force of wind and water. Strontium leaves the oceans, the largest reservoir of dissolved strontium, by deposition in marine carbonate sediment. Some strontium is transported from oceans to the atmosphere in sea spray, returning to the terrestrial environment in the form of precipitation (Capo et al. 1998). 

By far the highest concentrations, especially of AHTN, were detected in sediments near the river mouth at sites 3 and 1. These are also the only sites where AHMI was detectable. In this area, the supply of polycyclic musks is relatively low because of a low population density (Fig. 2). Hence, particularly favourable conditions for the accumulation of suspended particulate matter from upstream areas must be the reason for this pattern. This could be due to three factors i) low flow velocity, ii) high input of terrestrial detritus and, thus, large supply of suspended particulate matter for adsorption of contaminants, and iii) input of highly contaminated particles which were transported from the upper reaches of the river. 

For incubation with air, the phosphate, DOP, and TDP fluxes varied from -0.043 to A).001, A).068 to 0.001, and -0.071 to -0.042 mmol/(m -d), respectively, which showed that phosphorus moved from water to sediment. In the incubation with N2, the fluxes of phosphate ranged from -0.003 to 0.063 mmol/(m d), indicating a transport from sediment to water. The fluxes of DOP and TDP varied from -0.036 to 0.087 and from -0.071 to 0.151 mmol/(m d), respectively, which indicated that they moved from sediment to water at stations A2 and E3, and in the opposite direction at stations El and G2 (Table 2.18). The sediments in the Bohai Sea are mainly terrestrial detritus, on average, composed of 71% clay, 23% silt, and 6% sand. Taking into account the sediment type, the geometric mean fluxes of phosphorus were calculated and shown in Table 2.18. The average fluxes of PO , DOP, and TDP... 

FYom the indicators, the dominant source of PAHs in the NYS was the incomplete combustion of fossil fuel. Perylene was identified from most surface sediments, which indicated that the substances from a terrestrial source were accumulating in the northern YS. The main source was the terrestrial substance transported from the Yalujiang River Estuary into the sea. 

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