DTPA-extractable Pb Research Articles

TOXICITY EVALUATION OF WEATHERED COAL FLY ASH-AMENDED MANURE COMPOST

The general use of manure compost is limited by its residualtoxicity, and hence a study was performed to evaluate the use ofweathered coal fly ash (lagoon ash) to alleviate the toxicity ofmanure compost. Mature and immature manure compost were amendedwith lagoon ash at 0, 5, 10 and 20% (w/w dry weight basis), andtheir phyto-toxicity was evaluated by germination and root lengthgrowth of lettuce seed. The immature manure compost hadsignificantly higher contents of NH4-N, PO4-P, andacid- and water-extractable Cu and Zn contents than those of mature manure compost. Ash amendment caused asignificant increase in electrical conductivity (EC), but adecrease in NH4-N, PO4-P, and DTPA-, CaCl2- andwater-extractable Cd, Cu, Pb and Zn contents of both manurecompost. Addition of lagoon ash at a rate of 5% for immaturemanure compost and 10% for mature manure compost resulted in ahigher seed germination rate and root length growth. Thegermination index demonstrated significant negative correlationswith EC, NH4-N and DTPA extractable Cd, Cu, Pb and Zncontents. The present study supports the use of lagoon ash foramending manure compost to reduce the availability of traceelements and NH4-N.

Feasibility of Using Coal Ash Residues as CO-Composting Materials for Sewage Sludge

Alkaline coal ash residues produced from a coal-fired power plant were co-composted with sewage sludge to evaluate it's effect on heavy metal availability and the biological process of composting. Coal fly ash (FA) and lagoon ash (LA) were mixed with dewatered sludge at 0, 10 and 25% w/w, and the mixtures were composted for 100 days in laboratory batch reactors. The changes in pH, electrical conductivity (EC), CO2 production, microbial population, soluble and extractable heavy metal contents were measured during the composting period. Following an initial increase, pH started to decrease from day 7 onward till the end of the composting period for all treatments. Sludge with coal fly ash amendment had a higher pH and EC than those of the control and LA-sludge composts. Increasing fly ash amendment levels resulted in a significant reduction in DTPA-extractable Cd, Cu, Zn, Mn and Pb contents of the FA-sludge composts while the reduction was less obvious in the LA-sludge composts. No significant difference in CO2 production and the number of thermophilic bacteria were noted for all treatments except for 25% FA-sludge compost which had a reduced thermophilic bacterial growth and CO2 production. The inhibition which was possibly due to the high pH of coal fly ash, decreased with an increase in composting time. It can be concluded that the co-composting of coal ash residues with sewage sludge was able to reduce the availability of metals but did not exert a significant inhibition on the biological process of composting, except for 25% FA-sludge compost.

Extractability and availability of lead from calcareous Egyptian soils

Abstract The objective of this study was to compare seven soil testing solutions— 1 M NH 4 CH 3 0 2, 1 M HNO3 , 0.1 M HNO 3, 1 M KNO3, 0.005 M DTPA, 1 M NH 4 HCO3 + 0.005 M DTPA (ABDTPA), and 0.1 M EDTA—as extractants for Pb in 24 diverse calcareous soils and as predictors of plant Pb. The soils received 0 and 200 mg Pb kg‐1 as Pb(NO3)2 and are referred to as nontreated and treated soils, respectively. Of the seven soil extractants, 1 M HNO3 was the most effective extractant for Pb from nontreated and treated soils. However, 1 M HNO3, 0.005 M DTPA, 0.1 M EDTA, and ABDTPA were equally effective in their ability to extract Pb from treated soils. Wheat (Triticum aestivum L.) and beans (Vicia faba L.) were grown in the greenhouse in nontreated and treated soils. After 21 days, the plants were harvested and Pb concentration was measured. Regression analysis was used to develop models for predicting Pb uptake by wheat and beans as a function of extractable Pb. The regression models were successful in predicting Pb uptake by wheat and beans. In nontreated as well as in treated soils, 0.1 M HNO3 and 0.005 M DTPA extractable Pb explained 71% of the variability in Pb uptake by wheat, while 1 M NH 4 C 2 H 3 O 2 and 0.005 M DTPA extractable Pb accounted for 70% of the variability in Pb uptake by beans.

Long-term changes in soil and plant metal concentrations in an acidic dredge disposal site receiving sewage sludge

A long-term experiment was conducted to determine the distribution of sludge-borne metals applied to a revegetated acidic dredge spoil disposal site. The initial soil was infertile and highly acidic (pH 2.4). Sewage sludge and lime were applied in 1974 at the rates of 100 and 23 mt ha−1, respectively, and tilled into the soil to a depth of 20 cm. In 1974 an adjacent site was also revegetated with topsoil and lime but without sludge. Soil and plants were sampled 2, 4 and 16 yr following seeding. After 16 yr the total and DTPA-extractable Cu, Zn, Cr, Pb, Ni and Cd decreased in soils to nearly the levels of the control soils. Concentrations of metals in plants also decreased. Decreases in tissue concentrations ranged from 40 to 70% for Cu, Cr, Pb, Ni and Cd and up to 90% for Zn. The results showed that a single 100 mt ha−1 application of sewage sludge containing high concentrations of metals was a cost-effective method for improving plant growing conditions on highly acidic soils.