The Influence of Natural and Manufactured Nanoparticles on Heavy Metal Behavior in Natural Waters

A rapid development of the application of manufactured nanoparticles in science, technology, medicine and every day life is anticipated. Currently, there is still little knowledge about the behavior of manufactured nanoparticles in natural waters, their influences on the transport of organic pollutants, their effect on the behavior of toxic and radiotoxic heavy metals etc. Manufactured NPs are not yet present in the nature in significant amounts, i.e. “field studies” are not yet possible. However, conclusions by analogy based on the behavior of natural nanoparticles (natural colloids) can already be drawn. First, a very short introduction into the field of the detection of natural nanoparticles is given. The transport-impeding and the transport-facilitating effects of natural nanoparticles on heavy metal transport are analyzed. Examples are the immobilization of uranium by ferrihydrite nanoparticles in near-neutral mine waters during the flooding of an abandoned uranium mine and the mobilization of lead and arsenic by schwertmannite/H-jarosite nanoparticles in acid mine water from an abandoned Zn-Pb-Ag mine. The use of manufactured nanoparticles for the immobilization of heavy metals in natural waters is discussed. The adsorption of Pb2+, Cd2+, Cu2+ and UO22+ onto modified carbon nanotubes, synthetic ferrihydrite nanoparticles and titanium dioxide nanoparticles are considered with the focus on the carbon nanotubes. It is shown that all the nanoparticles considered have a potential for removing the above-mentioned heavy metal ions. A different point might be the challenge of gaining regulatory and public acceptance for using nanomaterials in water purification because of their still unknown or little known toxicity and environmental impact. The questions of the mobility of manufactured nanoparticles in natural waters and of potential transport-facilitating effects of artificial nanoparticles on heavy metals in case of accidental nanomaterial release are also addressed.