Ecotoxic metals

Because of the elevated concentrations of potentially ecotoxic metals and acid in mine water, and because of the potential for precipitation of benthos-smothering Fe, Al, Mn-oxyhydroxides (and other phases) in downstream recipient watercourses, water draining from mines is often regarded as a major environmental problem. Considerable effort and expense are incurred by treating... 

Midpoint indicatois Climate change. Ozone depletion. Photochemical oxidant formation. Particulate matter formation. Ionising radiation. Terrestrial acidification. Human toxicity. Terrestrial ecotoxicity. Freshwater ecotoxicity. Marine ecotoxicity. Metal depletion. Fossil depletion. Water depletion. Freshwater eutrophication. Marine eutrophication. Agricultural land occupation. Urban land occupation and Natural land transformation. Endpoint indicators Human health. Ecosystem diversity and Resource availability. 

Applications and Potentialities of Voltammetry in Environmental Chemistry of Ecotoxic Metals H, W, Niirnberg... 

APPLICATIONS AND POTENTIALITIES OF VOLTAMMETRY IN ENVIRONMENTAL CHEMISTRY OF ECOTOXIC METALS... 

It is obvious, that the environmental burden caused by hazardous metals, particularly with respect to the per se toxic metals, requires surveillance of the emissions and immissions for the introduction of appropriate environmental protection regulations as well as intensive ecochemical and ecotoxicological research to deepen and expand the knowledge on the fate, behavior and effects of ecotoxic metals in the various environmental compartments (atmosphere, hydrosphere, terrestrial eco-... 

Within the last decade it has been established, that voltammetry is one of the few instrumental trace methods which fulfill in a comprehensive manner the requirements in environmental trace chemistry of the ecotoxic metals mentioned afore. Therefore, suitable voltammetric methods, in the first place differential pulse voltammetry, have become one of the preferred approaches in environmental trace analysis and ecochemical research of ecotoxic metals and metalloids[7-10]. 

As a rule the ecotoxic metals exist at trace or even ultra-trace levels in the environment. This leads to analysis with concentrations of those metals usually below 1000 jJg/1 or 10 M. Consequently the application of conventional polarography is impossible and advanced modes have to... 

The area where voltammetry offers most particular potentialities and is frequently the most superior method of determination and investigation is the chemistry of ecotoxic metals in all types of natural waters[15]. 

For the Tyrrhenian estuaries, which belong the the practically non-tidal Mediterranean Sea, it has been shown, that the overwhelming part of the fluvial heavy metal freight is sedimentated in the estuarine zone and consequently the fluvial heavy metal input to the Mediterranean Sea by Arno, Tiber and the smaller rivers remains insignificant[45]. An example from this study is shown in Figure 7. When present studies in progress for the Rhone and Ehro[46] estuaries have been completed, a relevant basis will exist to assess the relative significance of fluvial and aeolian input of ecotoxic metals into the western Mediterranean Sea. 

Substantial emissions of ecotoxic metals into the atmosphere occur in the heavily industrialized and highly populated regions of the world. To a large extent the ecotoxic metals are bound to fine aerosol particles and therefore, undergo mesoscalic transport and distribution with the wind or, after advection to the upper troposphere, even hemispherical transfer. 

Usually weekly samples are collected and after filtrations, acidification and UV-irradiation of the rain or molten snow, Cu, Pb, Cd, Zn are determined simultaneously by DPASV at the HMDE and subsequently Se(IV) by DPCSV. This German Wet Deposition Program[26,76,77] carried out since 1980 by the institute, have revealed the main contours of the deposition burden with ecotoxic metals in the various regions of the country (Table 4). This also refers to the deposition of acid rain which is monitored via electrometric pH-measurements as well. From the wet deposition data an approximate assessment of the annual burden of the FRG by deposition of ecotoxic metals from the atmosphere has been possible (Table 5)[26]. 

Table 4. Average Daily Wet Deposition (in jjg/m /d) of Ecotoxic Metals with Rain and Snow in the Federal Republic of Germany...

Table 5. Approximate Annual Ecotoxic Metals of Wet Deposition Burden (in t/y) by Federal Republic of Germany ... 

The research on vet deposition of ecotoxic metals has also established several findings of general significance. Over 90% of the wet deposited metals are dissolved in the rain water. Consequently, they reach the vegetation in a form most favorable for uptake. In this context, it has to be realized further that wet deposition only constitutes a lower limit for metal uptake by the vegetation, because the rain leaches and dissolves further metal amounts from the dust particles deposited in dry periods onto the leaves[16,26]. 

Municipal and industrial waste waters, discharged treated or even still untreated, into rivers and coastal waters are the further important source of ecotoxic metals particularly with respect to the burden of aquatic ecosystems. Voltammetry offers an efficient and convenient way for control of the levels of ecotoxic metals[80,81]. The necessary pretreatment is simple and consists in filtration (0,45 pm) and subsequent treatment of the filtrate either by rapid UV-irradiation in a photodigestion device[82] equipped with high intensity mercury lamps (1200 W) with addition of some H2O2 or by a fast wet digestion procedure (see Figure 4). Then follows the simultaneous determination of Cu, Pb, Cd, Zn by DPASV at... 

Fig. 10. Typical time pattern of ecotoxic metal concentrations in rain during precipitation period of about 8 h.

Studies on the efficiency of ecotoxic heavy metal elimination by the usually applied biological waste water treatment plants[80] have revealed, that the elimination of those metals is rather limited. Moreover, although the total metal content is decreased compared with the untreated waste water, the apparently purified water leaving the treatment plant has a relatively higher or unaltered content of ecotoxic metals in the dissolved phase as consequence of solubilization from suspended material by organic complexators in the biological treatment plant. 

The procedure presented with the universal wet digestion can also be applied to all types of biological materials from the environment and extensive use of this feature is made in the analysis of samples to be stored in the German Environmental Specimen Bank[98-100], a new tool in environmental assessment and protection operated by the institute for the government. Other important applications to environmental biological materials deal with studies on the uptake of ecotoxic metals deposited with rain by certain types of common plants and by the needles and leaves of forest trees. 

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