正A wetland with attractive plants hosting birds and other wildlife is an esthetically pleasing prospect that is gaining popularity as a way of stabilizing or remediating metalcontaminated soils and sediment(Weber and Gagnon,2014; 相似文献
Trace elements and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were analyzed in soils from rural and light-industrialized sites (n=168) of Province of Pavia (Northern Italy). Most of the trace element values fit in typical ranges of concentrations in soils and are similar to the ones reported for rural sites in Italy or sites with no direct anthropogenic impact. Total concentrations of 2,3,7,8 chlorine substituted PCDD/Fs in superficial soils ranged between 24.4 and 1287 pg g(-1) dw (0.5-28.9 pg WHO(98)-TEQ g(-1) dw). The North Eastern part of the Province presented significantly higher levels (p<0.001) than the rest of the Province for As, Cd, Hg, Pb, Zn and PCDD/Fs. While the existence of a defined heavy metal polluting source for this specific site has been suggested, in the case of PCDD/Fs, profiles were not linked to any specific emission source fingerprint. In the whole extension of Pavia Province, OCDD/F dominated the 2,3,7,8 chlorine substituted congener soil pattern, followed by the 1,2,3,4,6,7,8 hepta-CDD/F congener. Principal Component Analysis (PCA) showed that this profile could not be associated to any described PCDD/F emission source fingerprint and was relatively similar to the baseline deposition of sites with no direct impact of PCDD/F emission sources independently of land use. 相似文献
When metal alloys are used as mechanical equipment or tools in explosive atmospheres, the occurrence and incendivity of mechanically generated sparks as ignition sources should be taken into consideration. The formation of mechanically generated sparks was investigated for seven metals, including Q235 steel, 304 stainless steel, TC4 titanium alloy, 6061 aluminum alloy, H62 bronze alloy, AMAK3 zinc alloy, and AZ31B magnesium alloy. The relationship between the physical-chemical properties and generation and incendivity of friction sparks was evaluated. For 6061 aluminum alloy, H62 bronze alloy, AMAK3 zinc alloy, and AZ31B magnesium alloy, no bright friction sparks were observed in the maximum friction velocity of 12 m/s and maximum surface pressure of 3.75 N/mm2, because of low hardness, high thermal conductivity, low melting point, and the absence of carbon content. Ignition testing indicated that nano titanium dust layers with MIEL (minimum ignition energy of dust layer) of 1 mJ were not ignited by friction particles from the four metal alloys. However, bright particles were clearly observed for 304 stainless steel, Q235 steel, and TC4 titanium alloy. Friction sparks at the maximum power densities showed incendivity with micro titanium layers having an MIEL of 17.5–25 mJ but not with PMMA, corn starch, and wood dust having MIELs greater than 1 J. Two different particle burning behaviors with different fragmentation mechanisms during the friction process were determined, namely the micro explosion phenomenon for TC4 titanium alloy and particle burst for Q235 steel. Results indicate that the physical-chemical properties of friction metal rods are useful for preliminary evaluation of spark generation. Powder layers with known MIEL can be considered as indicator testing materials to evaluate spark incendivity. 相似文献
Samples from 18 short sediment cores were analyzed for major and trace metals (Al, Fe, Ca, K, Mg, Mn, Si, Ti, Pb, Zn, Cu, Ni, and Cr), 210Pb, 137Cs, total organic carbon, grain size, and mineralogical composition to find the record of major environmental changes, either natural or anthropogenic, and to establish their chronologies. Some sediments are characterized by nearly constant composition over time, but others clearly show signs of an increasing marine influence, as an increase of the carbonate contents, after the opening of the Malamocco-Marghera Canal in 1969. These changes sometimes obscure the real pattern of pollutants and tracers, which is revealed by normalization against Al. Zn is the most important contaminant, with concentration factors up to 9.3 times the background level, and the most contaminated sediments are those within a few kilometers from the industrial district of Porto Marghera. 210Pb activity-depth profiles were used to calculate apparent accumulation rates that provide a basis for the assessment of metal fluxes. The sediments of several sites show a significant increase in anthropogenic metal contamination starting from the second decade of last century, with maximum inputs from 1930 to 1970. The decrease of heavy metal concentrations observed in surficial sediments of some sampling sites could be related to a recent reduction of pollutant inputs. 相似文献
The interaction of metals present in tannery waste and their tolerance in the plants of sunflower (Helianthus annuus L.) was studied in the present paper under field conditions. Effects of 100% tannery sludge and various amendments of tannery sludge (10%, 25%, 35%, 50%, 75%) along with one set of control were studied on the physiological and biochemical parameters of the plant along with their metal accumulation potential after 30, 60 and 90 d after sowing. The plants of H. annuus were found effective in the accumulation of metals (Cr, Fe, Zn and Mn) in roots, shoots and leaves, however, the level of toxic metal, Cr was found below detection limit in the seeds of the plant. The oil was extracted from the seeds of the plant and the level of oil content was increased up to 35% tannery sludge as compared to control followed by decrease at higher tannery sludge ratio. An increase in the chlorophyll, protein, cysteine, non-protein thiol and sugar contents was observed at the lower amendment of tannery sludge at initial exposure periods followed by decrease than their respective controls. Malondialdehyde content in the roots and leaves was increased beyond 50% sludge amendments at all the exposure periods as compared to control. However, proline and ascorbic acid contents of the roots and leaves of the plant increased at all the exposure periods and sludge amendments, compared to their respective controls. 相似文献
Sea salts (seven brands from six commercially-available sources) were dissolved in water to develop 30 g/l solutions, and selected water quality characteristics were then monitored for 96 h. One or more water quality characteristics changed significantly during the 96 h period in six of the reconstituted sea salts. Measured characteristics of sea water diluted to 30 g/l demonstrated no changes during the observation period. The sea salts from different sources also demonstrated differences in absolute concentrations of some characteristics measured. Application of the Biotic Ligand Model to predict copper toxicity to the bivalve Mytilus edulis in solutions of the salts tested yielded 96-h median-lethal concentrations that ranged from 2 to 13 μg/l. Since water quality affects toxicity of many environmental pollutants, the source of the sea salt and equilibration time should be considered when planning toxicity tests. 相似文献
The purpose of this study was to evaluate photodegradabilities of the following new low-nitrogen chelating agents: N-bis[(carboxymethoxy)ethyl]glycine (compound 1), N-bis[(1,2-dicarboxyethoxy)ethyl]glycine (compound 2) and N-bis[(1,2-dicarboxyethoxy)ethyl]aspartic acid (compound 3). At first photodegradation of these chelating agents as uncomplexed Na-compound 1–3 and Cu(II) complexes were tested, both in lake and distilled water, by exposing them to near-UV region radiation at the range of 315–400 nm. Uncomplexed Na-compounds 2 and 3 were selected to sunlight exposure experiments carried out in lake and distilled water. Compound 3 was also tested in sunlight as Cu and Ca complexes in both solutions. Photodegradation of Na6-compound 3 in distilled water was studied by exposing it to radiation at the wavelength of 253.7 nm. Photodegradation products were analysed by means of GC-MS (gas chromatography with mass selective detector).
The results demonstrated that compound 1 was quite photostable even as Cu complex while compounds 2 and 3 were found to be photodegradable. Over 90% reduction of compound 3 was achieved during one week and 80% reduction of compound 2 in two weeks' time when they were added as Na salt to lake water and exposed to sunlight. Compound 3 as Cu complex degraded totally in the sunlight in less than one week. In the case of compound 3, the degradation rate decreased depending on the counter cation in the order Cu > Na Ca. The study demonstrated that photodegradation of Na6-compound 3 does not result in total mineralization of the compound. A photodegradation pathway for Na6-compound 3 is proposed. 相似文献
This study analyzed the evolution of metal levels in surface sediments from the Guadalquivir estuary between 1997 and 2002 and assessed the impact of the April 1998 Aznalcollar tailings dam failure and subsequent cleanup on metal concentrations in surface sediments. We also analyzed metal distribution with time in five chemical fractions of the surface sediments: exchangable, carbonate, reducible, oxidizable, and residual. This work showed that the April 1998 Aznalcollar tailings dam failure caused a considerable increase in the concentrations of Cd, Zn, Cu, and Pb in the surface sediments of the Guadalquivir estuary. It was also found there was a change in the distribution of Cd, Zn, Cu, and Pb between the chemical fractions of the sediment after the failure of the dam. There were increases in the percentages of Cd in the carbonate fraction, of Zn and Pb in the reducible fraction, and of Cu in the oxidizable fraction, whereas the percentages of these elements associated with the residual fraction decreased. In 1999, there was a decrease in the metal concentrations in the surface sediments from the Guadalquivir estuary, and by 2000 the chemical distribution and metal levels had returned to levels similar those before the dam failure. 相似文献