Akhtar Iqbal

Anaerobic microbial fuel cell treating combined industrial wastewater: Correlation of electricity generation with pollutants.

Microbial fuel cell (MFC) is a new technology that not only generates energy but treats wastewater as well. A dual chamber MFC was operated under laboratory conditions. Wastewater samples from vegetable oil industries, metal works, glass and marble industries, chemical industries and combined industrial effluents were collected and each was treated for 98h in MFC. The treatment efficiency for COD in MFC was in range of 85-90% at hydraulic retention time (HRT) of 96h and had significant impact on wastewater treatment as well. The maximum voltage of 890mV was generated when vegetable oil industries discharge was treated with columbic efficiency of 5184.7C. The minimum voltage was produced by Glass House wastewater which was 520mV. There was positive significant co-relation between COD concentration and generated voltage. Further research should be focused on the organic contents of wastewater and various ionic species affecting voltage generation in MFC.

Effect of rainfall regimes and mulch decomposition on the dissipation and leaching of S‐metolachlor and glyphosate: a soil column experiment

BACKGROUND Interception by plant residues is a major process affecting pesticide persistence and leaching in conservation agriculture. Dissipation and leaching of S-metolachlor and glyphosate was studied in repacked soil columns covered with a mulch of maize and lablab residues. The columns were submitted to two contrasting simulated rainfall regimes: one with light but frequent rain (LF) and one with less frequent but more intense rain (HI). In both treatments, columns received the same amount of rainwater by the end of the experiment. RESULTS Decomposing crop residues on the soil surface retained more than 50% of the applied amount of pesticide. S-metolachlor dissipation in mulch residues was faster under the LF rainfall regime. This was attributed to more humid surface conditions, under which mulch decomposition was also faster. The formation of metabolites of both molecules was higher under the LF rainfall regime. However, leaching of S-metolachlor and its metabolites to deeper soil layers was greater under the HI rainfall regime, whereas they accumulated in the surface layer under the LF rainfall regime. Glyphosate remained in the surface soil layer because of its strong adsorption capacity, whereas aminomethylphosphonic acid leached down in small amounts without any difference between the two rainfall regimes. CONCLUSION The impact of mulch residues on herbicide dissipation was strongly dependent on molecule type and rainfall regime.

Novel P-Solubilizers from Calcium Bound Phosphate Rich Pine Forest of Lower Himalaya

ABSTRACT Phosphorus, an essential element for life, is continuously depleting from soils and thus demands sustainable management particularly in agriculture and forestry. Inorganic P constitutes the major proportion as tricalcium phosphate in soils of lower Himalayan region of Pakistan. We sampled these soils and screened for P-solubilizing microbes. A range of culturable microbial community (bacteria and fungi) was isolated and molecularly characterized which make the P available from mineral phosphates. There was an increase in abundance of phosphate solubilizing bacteria (PSB) at a 6-inch depth of the pine rhizosphere compared to the surface soil samples. Moreover, the isolates from lower Himalaya have higher abundance and better efficiency to solubilize the inorganic P than the ones from non-Himalaya. Most likely the P-solubilization done by our P-solubilizing microbes is via acidification as we observed the decrease in pH of the medium of microbial growth. Furthermore, the majority of isolated PSB belong to gammaproteobacterial class of Gram negative bacteria. Most interestingly, 13% of our isolated PSB were psychrotolerant (physiologically active at cold environment, i.e., 4°C) and able to solubilize inorganic P as efficiently as at ambient temperature. This study is unique in reporting the P-solubilizing microbes, particularly the psychrotolerant bacterial strains, of Lower Himalaya. Therefore the isolated bacterial and fungal strains have potential and may serve as biofertilizers in the region to increase the P availability in soils.

Transcriptomic responses of selected genes against chromium stress in Arundo donax L.

ABSTRACT Recently, giant reed (Arundo donax L.) has emerged as a useful bioresource capable of coping under harsh abiotic stress conditions produced by exposure to heavy metals, drought and salinity as evidenced by significant biomass production. The current study was undertaken to determine the expression of critical genes involved in resisting oxidative stress and maintaining normal cellular functions. The critical genes examined included glutathione reductase (GR) that prevents oxidative damage of membranes, carotenoid hydroxylase (CR), transcription factor (bHLH) and amidase involved in biosynthesis of indole-3-acetic acid following exposure to chromium (Cr) stress at concentrations of 0, 33.5, 67, 133 or 268 mg/L in giant reed. The S19 gene was used as internal control. It was not possible to extract RNA from severely stressed giant plant leaves at 133 and 268 mg/L Cr. Therefore, this investigation focused on gene expression in the presence of at 0, 33.5 or 67 mg/L Cr. Following Cr-mediated stress, gene expression of GR and CR was increased at 33.5 mg/L but reduced at 67 mg/L. The transcription factor, bHLH, gene expression remained unchanged. Amidase gene expression was elevated at 67 mg/L Cr. Data suggested that over expression of amidase and GR genes at high Cr exposure might increase growth and biomass of giant reed as well as enhance tolerance. These results indicated that giant reed tolerated the presence of Cr stress due to over expression of amidase and GR genes. It would appear that giant reed may serve a beneficial role for phytoremediation of Cr contaminated wastewater and soils at concentrations below 100 mg/kg.

Mulch of plant residues at the soil surface impact the leaching and persistence of pesticides: A modelling study from soil columns

Crop residues left on the soil surface as mulch greatly influence the fate of pesticides in conservation agricultural practices because most of the applied pesticide is intercepted by mulch before passing to the soil. Modelling of pesticide losses from wash-off and leaching will greatly improve our understanding of the environmental consequences of pesticides in these systems. The PASTIS model, which simulates water transfer, mulch decomposition, and pesticide dynamics, was adapted in this new version to model the interactions between pesticides and mulch in order to simulate the impact of mulch on pesticide dynamic. Parameters of mulch dynamics and pesticide degradation and retention processes were estimated using independent incubation experiments. The PASTIS model was tested with experimental laboratory data that were obtained from two pesticides (Glyphosate and s-metolachlor) applied to soil columns where mulch composed of maize and dolichos was placed at the soil surface impacted by two rain intensities (a high and infrequent intensity and a light and frequent intensity). Simulations indicated good agreement between simulated and experimental values. After 1 day, 45-46% of the pesticides leached from the mulch and 54-55% remained in the mulch for both pesticides and both rain intensities. During the experiment, pesticide wash-off was greater for the high and infrequent rain (56-57%) compare to light and frequent rain (39-45%) for both pesticides. A smaller amount of S-metolachlor washed off with the light and frequent rain intensity (39%) than glyphosate (45%) because of its lower desorption rate from mulch residues. Glyphosate was more degraded (37-45%) than s-metolachlor (17-37%), which agrees with preliminary incubation experiments that were used for parameter estimation. A sensitivity analysis indicated that the saturation index of mulch at which pesticides started their diffusion in the rainwater and the time of the first rainfall were the two parameters that influenced the most output variables of our model. This study suggests that the PASTIS model developed for pesticide dissipation in mulch is a useful tool to evaluate the potential risk of pesticide leaching to the groundwater in conservation agriculture systems.