Groundwater seeps

The trace elements are introduced into seawater by river runoff, atmospheric transport, hydrothermal venting, groundwater seeps, diffusion from the sediments, and transport from outer space, usually as micro meteorites. The magnitudes of the first three of these fluxes, which are considered to be the major ones, are given in Table 11.1. Anthropogenic activities have significantly increased some of these fluxes, as discussed later. 

Trace elements are discharged into the ocean in particulate and dissolved form as a component of river runoff and groundwater seeps. They are introduced into these waters during the chemical and mechanical weathering of crustal rocks. Thus, the chemical composition of river water is dependent on the composition of the rocks in the... 

Shallow-water embayments provide a mechanism to isolate seawater so that evaporation can raise salt ion concentrations. Arid climates are required to ensure that the rate of water loss from evaporation exceeds the rate of water supply by rainfell, groundwater seeps, or river runoff. Seawater can be resupplied continuously via a type of antiestuar-ine circulation as illustrated in Figure 17.2 or episodically as a result of sea level change, plate tectonics, or very high tides and storm surges. 

Sabkhat also form inland, where river input and saline groundwater seeps contribute salt and water, forming an evaporitic pan. As illustrated in Figure 17.6, these continental sabkhat are fer more isolated from the ocean than a marine sabkha. They also contain far less biogenic detritus. 

Although the carbonates are not very soluble in water, they are bases thus, they dissolve readily in acidic solutions. As mildly acidic groundwater seeps through limestone beds, insoluble CaCOs is converted to soluble Ca(HC03)2-... 

Leachate tends to percolate downward through solid waste, continuing to extract dissolved or suspended materials. In most landfills, leachate seeps through the landfill from external sources, such as surface drainage, rainfall, groundwater, and water from underground springs, as well as from the liquid produced from the decomposition of the wastes, if any.3... 

A flow model, created with the Seep/W software, indicated that the trench influences groundwater movement within an area of approximately 25 m, with the fastest flows closest to the trench. Flow rates within the tailings increase towards the trench with maximum flow of 1.2x1 O 7 m/s across the tailings/trench interface. Over a 10 m section this flow rate relates to about 10"5 m3/s of groundwater, entering the trench. 

Tapped-out oil and gas fields are full of drill holes that could leak the carbon dioxide. The stored gas might also seep into groundwater pools. But the North Sea project seems to be working well. Seismic images under the ocean floor show that a thick layer of clay capping the sandstone is sealing in the millions of tons of carbon dioxide injected. 

Many refineries unintentionally release, or have released, liquid hydrocarbons to groundwater and surface waters. At some refineries contaminated groundwater has migrated off-site and resulted in continuous seeps to surface waters. Although the actual volume of hydrocarbons released in such a manner is relatively small, there is the potential to contaminate large volumes of groundwater and surface water, possibly posing a substantial risk to human health and the environment. 

This type of landhll solves some of the problems posed hy open dumps. For example, odors are less readily released into the air, and hres are less likely to break out. Infestation hy rodents, insects, and other animals is usually reduced also. But the most important problem posed hy open dumps—pollution of surface and groundwater-remains. It is still possible for rainwater to seep through layers of dirt and waste, leaching out noxious and toxic materials into nearby bodies of water. 

Groundwater can be contaminated by bacteria and other pathogens that seep from septic tanks, bro-... 

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