Bioconcentration Of Zn Research Articles

Impact of organic amendments on the bioavailability of heavy metals in mudflat soil and their uptake by maize.

Organic amendments (OAs) can be a sustainable and effective method for mudflat soil improvement. A field experiment was conducted to investigate the potential of OA application to mudflat soil improvement. We measured the pH, soil organic matter (SOM), salinity, maize growth, and heavy metal (HM) accumulation in OA-applied soils, and maize tissues after three OAs, sewage sludge (SS), Chinese medical residue (CMR), and cattle manure (CM), were applied at the application rates of 0, 30, 75, 150, and 300 t ha-1. OA application significantly increased the SOM and decreased the pH and salinity of mudflat soils. The maize biomass and HM contents in soil and maize increased after OA application. The bioavailability and bioconcentration of HMs were generally in the sequence of SS > CMR > CM. The average bioavailability ratios of HMs were in the order of Cd > Zn > Cu > Mn > Ni. The bioconcentration of Zn and Cd by maize was highest, followed by Mn, Cu, and Ni. SOM, pH, and salinity were the important factors regulating soil available HMs and, subsequently, HM accumulation in maize. Among the three OAs, SS is most effective in decreasing soil salinity, and increasing the SOM, bioavailability, and bioconcentration of HMs. On the other hand, CM was the best OA because it promoted significant maize growth yet maintained low HM contamination risk.

Acute toxicity of some heavy metals to the fresh water snail, Theodoxus niloticus (Reeve, 1856)

Three toxicity experiments were carried out separately to study the toxicity effects of Zn, Fe and Pb on adult freshwater snail Theodoxus niloticus (Gastropod, Prosobranchia, Nertidae). The LC50 values for the 96 hr exposures of Zn, Fe and Pb on Theodoxus niloticus were 12.199, 8.6 and 18 mg/l respectively. These values increased by decreasing the time of exposure. Fe was more toxic followed by Zn and Pb to Theodoxus niloticus. The rate of mortality increased by increasing the exposure period and concentration of metals in solution. Moreover, bioconcentration of Zn, Fe and Pb in soft parts and shell increased gradually by increasing the concentrations of each metal in solutions. After 96 hr of exposure, the bioaccumulation factors for each metal were decreased from highest values in the control to the lowest one with the highest concentration of the metal. It is difficult to compare LC50 values for metals for this species with those for other gastropod species due to different abilities of closely related taxa or the species belonging to the same genus, which live in the same habitats, to accumulate metals.

Uptake of hazardous elements by spring onion (Allium fistulosum L.) from soil irrigated with different types of water and possible health risk

Bio-concentration of elements such as Mo, As, Se, Fe, Cu, Zn, Ni and Pb was analyzed in spring onion (Allium fistulosum L.) in three different locations of central Punjab, Pakistan. At location GW, relatively low level of hazardous elements was found in spring onion, suggesting that groundwater is a safe source of water for irrigating food crops. The pH of soil at wastewater irrigation was found less acidic (pH 7.4) than the other sites. The range of concentration in the different samples of spring onion was as follows: 6.15–8.16 mg kg−1 for Mo, 2.77–4.28 mg kg−1 for As, 0.395–0.705 mg kg−1 for Se, 36.73–48.17 mg kg−1 for Fe, 10.58–16.26 mg kg−1 for Cu, 28.87–39.79 mg kg−1 for Zn, 6.66–8.75 mg kg−1 for Ni and 4.33–6.09 mg kg−1 for Pb, respectively. High bio-concentration of Zn (15.37) from soil to spring onion was found at canal water irrigated location. The estimated daily intake of metal for spring onion was less, but the health risk index was higher than 1 for Mo, As, Cu, Pb and Ni, respectively. This was due to higher proportion of spring onion in diet, which consequently increased the health risk index for metals. Therefore, it is recommended to avoid growing vegetables in untreated urban and rural wastewater containing elevated amounts of metals.

Suitability of Urban Wastes for Crop Production in Zaria, Northern Nigeria: Bioavailability, Phytotoxicity, and Fractions of Micronutrients

The suitability of two composted solid urban wastes for crop production was evaluated in a pot experiment with sorghum (Sorghum bicolor) that focused on the geochemical fractions, bioavailability, and phytotoxicity of copper (Cu), manganese (Mn), and zinc (Zn). Total concentrations of Cu, Mn, and Zn in soil increased with increasing waste application, ranging from 1.6 to 48.2 mg kg−1 for Cu, 84 to 474 mg kg−1 for Mn, and 13.8 to 597 mg kg−1 for Zn. Waste application significantly increased pH and electrical conductivity (EC) of the soil. Copper, Mn, and Zn in the waste-amended soil were speciated into mobile (F1), easily mobilizable (F2), occluded in Mn oxides (F3), organically bound (F4), occluded in amorphous Fe oxides (F5), occluded in crystalline Fe oxides (F6), and residual (F7) fractions to assess the lability of the metals. On the average, the F4 was the most dominant Cu and Zn fraction, accounting for between 37 and 60% of total Cu and from 14 to 40% of total Zn concentrations, whereas F3 was the dominant Mn fraction closely followed by F4. The concentrations of Cu, Mn, and Zn in sorghum dry matter (DM) decreased with increasing waste application, probably induced by osmotic stress and ionic toxicity. Tissue Zn (Y-Zn) and Mn (Y-Mn) correlated significantly with the F1 and F2 fractions, but pH was an overriding factor in predicting Cu and Zn bioconcentration. Used as soil amendments, the application rate for these Zaria urban wastes should be limited to ≤10% (w/w basis), as Zn in the sorghum tissue reached the toxic limit just from one application of the waste to soil.