Metal releases from a municipal solid waste incineration air pollution control residue mixed with compost

Genotoxic effects of PM10 and PM2.5 bound metals: metal bioaccessibility, free radical generation, and role of iron

The present study was undertaken to examine the possible genotoxicity of ambient particulate matter (PM₁₀ and PM_2.5) in Pune city. In both size fractions of PM, Fe was found to be the dominant metal by concentration, contributing 22% and 30% to the total mass of metals in PM₁₀ and PM_2.5, respectively. The speciation of soluble Fe in PM₁₀ and PM_2.5 was investigated. The average fraction of Fe³⁺ and Fe²⁺ concentrations in PM_2.5 was 80.6% and 19.3%, respectively, while in PM_2.5 this fraction was 71.1% and 29.9%, respectively. The dominance of Fe(III) state in both PM fractions facilitates the generation of hydroxyl radicals (^·OH), which can damage deoxyribose nucleic acid (DNA), as was evident from the gel electrophoresis study. The DNA damage by ^·OH was supported through the in silico density functional theory (DFT) method. DFT results showed that C8 site of guanine (G)/adenine (A) and C6 site of thymine (T)/cytosine (C) would be energetically more favorable for the attack of hydroxyl radicals, when compared with the C4 and C5 sites. The non-standard Watson-Crick base pairing models of oxidative products of G, A, T and C yield lower-energy conformations than canonical dA:dT and dG:dC base pairing. This study may pave the way to understand the structural consequences of base-mediated oxidative lesions in DNA and its role in human diseases.

Electrodialytic remediation of municipal solid waste incineration residues using different membranes

In the present work, three different commercial membrane brands were used in an identical electrodialytic cell setup and operating conditions, in order to reduce the leaching of metals and salt anions of two types of municipal solid waste incineration residues: air pollution control residues of a semi-dry flue-gas cleaning system and fly ashes from a plant with wet flue-gas cleaning system. The results showed a general reduction of the leaching in both residues after ED remediation. For the following elements, the leaching was found to be different after ED treatment depending on the membrane used, with statistical significance: • Air pollution control residues of the semi-dry flue-gas cleaning system: Cr, Cu, Ni, Pb, Zn; • Fly ashes from a plant with wet flue-gas cleaning system: Al, Ba, Cu, Ni, Zn, Cl, SO₄. Final leaching values for some elements and membranes, but not the majority, were below than those of certified coal fly ash (e.g. Al or Cr), a material which is commonly used in construction materials; at the same time, some of these values were reduced to below the Danish law thresholds on the use of contaminated soil in constructions. These results show the potential of ED as a technology to upgrade municipal solid waste incineration residues.

Competitive adsorption and transport of Cd, Cu, Ni and Zn in a mine soil amended with mussel shell

Batch type and column experiments were used to study competitive adsorption-desorption and transport for Cd, Cu, Ni and Zn in a mine soil, both un-amended and amended with mussel shell. Batch type experiments showed that adsorption was affected by the added concentration of the metals, generally following the sequence Cu>Zn>Cd≈Ni. Metal desorbed was a function of the dose of metal added, as well as of the dose of shell amendment, being relevant that even when the highest dose of metal (2300 μM) was added, the 24 g kg(-1) shell amendment caused a drastic diminution in the amount of metal desorbed. Column experiments showed that even the lowest dose of the shell amendment (6 g kg(-1)) caused a strong retention of the 4 heavy metals assayed, whereas using the 24 g kg(-1) shell amendment no metal was detected in the effluent during the time of the experiment. The mass of metal retained in the un-amended soil was very different for the various metals assayed, but the amendment with 6 g kg(-1) shell increased this retention in all cases, and the 24 g kg(-1) amendment caused almost 100% retention for all 4 metals. The retardation factor (R) suffered an overall increase as a function of the shell dose; the profile distribution of the 4 heavy metals was homogeneous through the un-amended soil into the column, but the shell amendment clearly decreased the solute transport affecting these metals, causing its concentration in the first centimeters of the soil profile.

Heavy metal retention in copper mine soil treated with mussel shells: batch and column experiments

Batch and column experiments are used to study the effects of ground mussel shell amendment on the retention of heavy metals in acidic mine soil. The soil pH increases proportionally with the mussel shell concentration employed. Mussel shell amendment increases Cu, Cd, Ni and Zn retention in mine soil when compared with unamended soil. In fact, Cu retention was 6480μmolkg(-1) (43% of the total added) when the maximum metal concentration (1570μM) was added to the unamended soil, whereas retention reached 15,039μmolkg(-1) (99.9% of the total Cu added) when soil was amended with 24gkg(-1) mussel shell; in the case of Cd, adsorption increases from 3257μmolkg(-1) (15% of the total added) for the unamended soil, to 13,200μmolkg(-1) (87% of the total added) for the shell-amended soil; Ni retention increased from 3767μmolkg(-1) (25% of the total added) corresponding to unamended soil, to 11,854μmolkg(-1) (77% of the total added) for the shell-amended soil; and finally, Zn retention increased from 4684μmolkg(-1) (31% of the total added), for unamended soil, to 14,952μmolkg(-1) (98% of the total added) for shell-amended soil. The results of the constant flow transport experiments show that the addition of the 24gkg(-1) mussel shells can retain Cu, Cd, Ni and Zn within the first few centimetres of the column length, indicating the usefulness of ground mussel shells to drastically decrease the mobility and availability of these pollutants and to facilitate soil remediation.

Metal concentration of PM(2.5) and PM(10) particles and seasonal variations in urban and rural environment of Agra, India

Three monthly 24-hour samples of airborne aerosols (PM(10) and PM(2.5)) were collected at an urban and a rural site of the North central, semi-arid part of India during May 2006 to March 2008. Seven trace metals (Pb, Zn, Ni, Fe, Mn, Cr and Cu) were determined for both sizes. The annual mean concentration for PM(10) was 154.2 microg/m(3) and 148.4 microg/m(3) at urban and rural sites whereas PM(2.5) mean concentration was 104.9 microg/m(3) and 91.1 microg/m(3) at urban and rural sites, respectively. Concentrations of PM(10) and PM(2.5) have been compared with prescribed WHO standards and NAAQS given by CPCB India and were found to be higher. Weekday/weekend variations of PM(10) and PM(2.5) have been studied at both monitoring sites. Lower particulate pollutant levels were found during weekends, which suggested that anthropogenic activities are major contributor of higher ambient particulate concentration during weekdays. Significant seasonal variations of particulate pollutants were obtained using the daily average concentration of PM(10) and PM(2.5) during the study period. PM(2.5)/PM(10) ratios at urban and rural sites were also determined during the study period, which also showed variation between the seasons. Three factors have been identified using Principal Component Analysis at the sampling sites comprising resuspension of road dust due to vehicular activities, solid waste incineration, and industrial emission at urban site whereas resuspension of soil dust due to vehicular emission, construction activities and wind blown dust carrying industrial emission, were common sources at rural site.