![]() ![]() ![]() ![]() Water quality investigations have clearly been a stimulus for measurement of toxic heavy metals in order to understand their behavior in natural systems.From a more fundamental point of view, it is crucial to understand the behavior of trace elements in geological processes, in particular during chemical weathering and transport by waters. For example, it is generally accepted that rare earth elements (REEs) in waters behave as good analogues for the actinides, whose natural levels are quite low and rarely measured. Pollution impact studies require knowledge of the natural background concentrations and knowledge of pollutant behavior. Trace elements are therefore highly sensitive indexes of human impact from local to global scale. Many trace elements have been exploited from natural accumulation sites and used over thousands of years by human activities. This is particularly evident for toxic elements such as aluminum, whose concentrations are related to the abundance of fish in rivers. Although rare, trace elements in natural systems can play a major role in hydrosystems. ICP-MS provides the capability of determining trace elements having isotopes of interest for geochemical dating or tracing, even where their dissolved concentrations are extremely low.The determination of trace elements in natural waters is motivated by a number of issues. In particular, the development of inductively coupled plasma mass spectrometry (ICP-MS) has considerably improved our knowledge of trace-element levels in waters since the early 1990s. This growing interest is clearly triggered by the technical advances made in the determination of concentrations at lower levels in water. Conversely, trace elements in rocks such as chlorine and carbon are major elements in waters.The geochemistry of trace elements in river waters, like that of groundwater and seawater, is receiving increasing attention. For example, aluminum, iron, and titanium are major elements in rocks, but they occur as trace elements in waters, due to their low mobility at the Earth's surface. Being trace elements in natural waters does not necessarily qualify them as trace elements in rocks. Therefore, most of the elements, except about ten of them, occur at trace levels in natural waters. This means that trace elements are not considered when "total dissolved solids" are calculated in rivers, lakes, or groundwaters, because their combined mass is not significant compared to the sum of Na+, K+, Ca2+, Mg2+, H4SiO4, HCO3-, CO32-, SO42-, Cl-, and NO3. Trace elements are characterized by concentrations lower than 1 mg L-1 in natural waters. ![]()
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