Soil pH effect on phosphate induced cadmium precipitation in Arable soil.

The objective of this study was to determine soil pH conditions that allow cadmium (Cd) to precipitate as Cd minerals in phosphate (P) amended soil. Cadmium immobilization could be attributed primarily to Cd adsorption due to increase in pH and negative charge. Soil pH might not affect Cd precipitation as Cd3(PO4)2 by direct reaction of Cd and P in the studied soil, even when soil pH increased up to 9.0. However, Cd might precipitate as CdCO3 with increasing pH up to 9.0 in P untreated soil and up to 8.0 in P treated soil depending on CO2 level.

Biochemical responses and phytoremediation potential of Azolla imbricata (Roxb.) Nakai in water and nutrient media exposed to waste metal cutting fluid along with temperature and humidity stress.

Phytoremediation of metals from water (WM) and nutrient (NM) media exposed to waste metal cutting fluid (WMCF) along with temperature (T) and humidity (H) stress was tested using Azolla imbricata (Roxb.) Nakai. In the absence of WMCF, biomass was higher in NM than in WM during all tests. Surprisingly, opposite results were noted in the presence of WMCF, with growth failing at exposure to > 0.1% and > 0.5% in NM and WM, respectively. Further, correlation analysis of the growth data following WM exposure revealed that biomass was affected positively by T and negatively by H and metal accumulation. Simultaneously, metal accumulation was affected negatively by T and positively by H. The average accumulations of Al, Cd, Cr, Fe, Pb, and Zn across all T/H tests were 540, 282, 71, 1645, 2494 and 1110 mg·kg-1, respectively. The observed bioconcentration factor indicated that A. imbricata acts as a hyperaccumulator or accumulator of Zn (>10) and as either accumulator (>1) or excluder (<1) of the other metals. Overall, the phytoremediation performance of A. imbricata in multi-metal-contaminated WMCF was high in WM under all environmental conditions. Therefore, the use of WM is an economically feasible approach for the removal of metals from WMCF.

Assessment of foliar dust deposition and elemental concentrations in foliar dust and long rows of grand tamarind leaves along two major roads of Coimbatore, India.

In this study, the concentration of foliar dust and 23 elemental concentrations in foliar dust and foliar tissues were studied using long rows of grand tamarind trees grown in two major roads in Coimbatore, India. Twenty-four sampling sites were chosen and categorized as urban (n = 5), suburban (n = 14), and rural (n = 5) areas based on the local population. In the case of foliar dust concentration, a significant difference was noted between the sites of urban (range between 3.06 and 6.68 µ/cm2) and suburban areas (range between 0.56 and 5.75 µ/cm2) but not for rural areas (range between 0.40 and 0.47 µ/cm2). When comparing the urban, suburban, and rural, either significantly or insignificantly, 17 elements (Al, Ba, Bi, Ca, Cd, Co, Cu, Fe, Ga, In, K, Mg, Mn, Ni, Sr, and Zn) in urban and five elements (Ag, B, Cr, Na, and Pb) in suburban were higher. However, in the case of elements in tamarind laves, almost all elements except Na and K were higher in the urban area. Furthermore, the study results suggest that the elements in both foliage dust and in tamarind leaves are not evenly distributed between the sites of urban, suburban, and rural areas. This uneven distribution might be due to the construction being performed on a stretch of a four-lane highway during sampling, heavy transportation in three small junctions of suburban sites, and a rail over-bridge construction in one suburban site. However, comprehensive studies are needed to confirm this conclusion.

Influence of sawdust addition on the toxic effects of cadmium and copper oxide nanoparticles on Vigna radiata seeds.

Studies in the literature concern the toxicity of nanoparticles either in a Petri dish or in agar media-based tests. Therefore, for environmental relevance, individual and binary mixtures of metal oxide nanoparticles (M-NPs) cadmium oxide (CdO-NP) and copper oxide (CuO-NP) were tested in this study for their effect on Vigna radiata in soil with and without the addition of sawdust. Seed germination was 67% in 100 mg CuO-NP in soil without sawdust. Seeds failed to germinate in 100 mg CdO +100 mg CuO-NPs in soil without the addition of sawdust and germination was 83% at the same concentration in soil with sawdust. In sawdust added to soil, when compared with control (soil without M-NPs), the maximum reduction in shoot (82%) and root (80%) length and wet (61%) and dry (54%) weight of plant was recorded in CdO-NP treated soil. Similarly, compared with control (soil without sawdust and M-NPs), the percent reduction in shoot (61%) and root (70%) length and wet (44%) and dry (48%) weight was highest in CdO-NP treated soil not supplemented with sawdust. In a binary mixture test (CdO-NP + CuO-NP), the addition of sawdust promoted the above plant growth parameters compared with individual CdO-NP and CuO-NP tests. Cadmium (511 mg kg-1 for individual and 303 mg kg-1 for binary mixture tests) and Cu (953 mg kg-1 for individual and 2954 mg kg-1 for binary mixture tests) accumulation was higher in plants grown in soil without sawdust. The beneficial effect of sawdust addition was observed in seed germination, plant growth, and metal accumulation. With or without sawdust, the binary mixture of CdO and CuO was antagonistic. These results indicate that sawdust can prevent M-NP-induced toxicity and reduce metal accumulation in plant tissues.

Mn(2+)-Ion Site Distribution of Zeolite Y (FAU, Si/Al = 1.56) Depending on the Ion-Exchange Ratio.

To investigate the tendency of Mn(2+)-ion exchange into zeolite Y, four single crystals of fully dehydrated Mn2+, Na(+)-exchanged zeolite Y (Si/Al = 1.56) were prepared by the exchange of Na75-Y (INa75I[Si117Al75,O384]-FAU) with aqueous of various concentrations by Mn2+ and Na+ in a total 0.05 M for molar ratios of 1:1 (crystal 1), 1:25 (crystal 2), 1:50 (crystal 3), and 1:100 (crystal 4), respectively, followed by vacuum dehydration at 400 degrees C. Their single-crystal structures were determined by synchrotron X-ray diffraction techniques in the cubic space group Fd3(-)m and were refined to the final error indices R1/wR2 = 0.0440/0.1545, 0.0369/0.1153, 0.0373/0.1091, and 0.0506/0.1667, respectively. Their unit-cell formulas are approximately LMn33.5Na8I[Si117Al75O384]-FAU, IMn20.5Na34I[Si117Al75O384]-FAU, IMn20.5Na34I[Si117Al75O384]-FAU, and IMn16.5Na42I[Si117Al75O384]-FAU, respectively. The degree of Mn2+-ion exchange increases from 44.3% to 89.1% with increasing the initial Mn2+ concentrations as Na+ content and the unit cell constant of the zeolite framework decrease.