Heavy metals phytofiltration potential of Hydrocotyle umbellata from Nullah Lai wastewater and its environmental risk.

This study aims to examine the heavy metal phytofiltration potential of Hydrocotyle umbellata from Nullah Lai wastewater and its environmental risk. Wastewater was initially analyzed for heavy metals and physicochemical parameters and compared with irrigation water standards. The phytofiltration potential of H. umbellata was determined by periodically monitoring heavy metal concentrations at time points T1 (day 05), T2 (day10), T3 (day 15), and T4 (day 20). This study shows that some water parameters reached the permissible limits after treatment with H. umbellata. Results of the risk analysis reveal a significant discharge (kg d-y) of heavy metals to arable land. Phytofiltration efficiency of H. umbellata for water quality parameters was in order of Ni (98.75%), Cr (98.11%), Cd (95.84%), Pb (94.90%), Cu (94.10%), Zn (85.34%), BOD (53.67%), TDS (29.28%), EC (27.31%), Cl (6.65%), and SAR (6.34%). The growth of H. umbellata in wastewater resulted in heavy metal bioaccumulation in both roots and shoots of the plant. Less than 01 translocation factor (TF) values for cadmium, copper, lead, chromium, and zinc showed the metal tolerance ability of the tested plant. These results demonstrated that treated water could be used in water-deficient peri-urban areas as supplementary irrigation.

This study evaluates the phytofiltration potential of Hydrocotyle umbellata for heavy metals (Cu, Cr, Cd, Pb, Ni, and Zn) from Nullah Lai wastewater by greenhouse experiments. The environmental risk associated with using Nullah Lai wastewater for irrigation purposes was estimated.

Floriculture: alternate non-edible plants for phyto-remediation of heavy metal contaminated soils.

Contamination of pre-urban arable land, by untreated municipal/industrial effluents derived heavy metals, is causing serious health hazards to human beings and abiotic components of the ecosystem. In this study, phytoremedial potential of four non-eatable floriculture plants, i.e. antirrhinum, pansy, calendula, and marigold, was explored by growing in heavy metal contaminated soil (collected from pre-urban area under untreated wastewater irrigation for more than 20 years) amended with bacterial inoculum and EDTA amended soils under greenhouse conditions for 75 days. Bacterial inoculation gave a maximum increase in the root (47.1%) and shoot (30.9%) biomass, while EDTA amendment gave 37.1 and 21.4%, respectively. However, EDTA application increases more metal concentrations in the root (65%) and shoot (36%) than that of bacterial inoculum, i.e. 37 and 27%, respectively. The values of bioconcentration factor (BCF) of all the plants for Cd, Cr, Ni and Pb were significantly increased by EDTA application and bacterial inoculum over control. The BCF values were either ≈1 or >1 in all the treatments in case of Cr. Ni and Pb. Contrarily, reduction in translocation factor (TF) values of all the flowering plants for all the metals were observed over control when the growth medium was treated with EDTA and bacterial inoculum.

Arsenic Contamination in Rice Grown Under Anaerobic Condition in Arid Agriculture: Assessment and Remediation.

Arsenic (As) concentrations in fine (2) and coarse (3) rice varieties belonging to Hafizabad, Gujranwala and Sheikhupura districts was assessed initially by means of field survey, followed by pot experiments. Bulk soil samples collected from same rice districts (Hafizabad and Gujtanwala) were spiked with As (0, 10, 20 mg kg-1) and each was amended with iron sulphate (0, 25, 50 g kg-1) to investigate their effect on plant growth and uptake under anaerobic conditions. Survey results revealed that mainly fine long grain (Super Basmati and KSK 515) and coarse long grain (Basmati 386 and Kainat) rice varieties were grown in the area. Overall, 16% rice grain samples were above the recommended permissible limit (RPL) of 300 mg kg-1. Among varieties, 24% grain samples of coarse and 12% of fine varieties had As concentration above the RPL. Results of pot experiments showed a significant decrease in straw and grain yield and increase in As concentration with increasing rates of As spiking. Paddy yield increased significantly when As spiked soils were amended with iron sulfate; and opposite was true for As concentration.

Phytoextraction of Ni, Pb and, Cd by duckweeds.

Heavy metals phytoextraction potential of swollen duckweed (Lemna gibba Linn.) and lesser duckweed (Lemna aequinoctialis Welw.) was determined under greenhouse conditions by exposing to untreated industrial/municipal effluent for a period of 21 days. The nickel (Ni), lead (Pb), and cadmium (Cd) concentrations in water samples were measured weekly and in plant biomass at the termination of experiments. Significant differences (p < 0.05) between initial and final physicochemical parameters and in heavy metal concentrations of plant and water samples were observed. Periodically measured metal concentrations in mediums revealed that removal percentage was dependent on initial Ni (2.15 mg L-1), Pb (1.51 mg L-1), and Cd (0.74 mg L-1) concentrations. The final metal removal percentages were in the sequence of Ni (97%) > Pb (94%) > Cd (90%) when treated with Lemna gibba L. as compared to control (9-12% reduction). High biomass production of Lemna gibba L. resulted in a large metal reduction in the growth medium and the total plant metal contents were in the sequence of Ni (427 µg) > Pb (293 µg) > Cd (105 µg). The lesser duckweed did not survive under experimental conditions. Based on these results, we concluded that Lemna gibba L. is a good candidate for phytoremediation of wastewater.

Biosorption of metal ions on lignocellulosic materials: batch and continuous-flow process studies.

Metal adsorption capacities of bioadsorbents, derived from low-cost agricultural waste, were assessed. Batch and column experiments were conducted for evaluation of lead (Pb), cadmium (Cd), and chromium (Cr) sorption kinetics on to modified (by treating with base and acid) and unmodified sugarcane bagasse and corn cob. Langmuir, Freundlich, and Redlich-Peterson equations were used to understand metal adsorption behavior and Elovich and Lagergren's pseudo-first-order and pseudo-second-order kinetics equations were used for estimation of adsorption kinetics parameter. The suitability of the models to experimental data was reflected by high r2 values. Among sorption models, Langmuir and Redlich-Peterson were proved equally good and Cd, Cr, and Pb adsorption process followed the Langmuir isotherm. Batch adsorption experiment showed that the metal adsorption ability of the treated materials was higher than that of untreated. The adsorption sequence was Pb > Cr > Cd. Pseudo-second-order kinetics model was found suitable in describing the obtained data. Result of the column adsorption experiments supplement the batch results and revealed the role of agricultural waste materials in remediation of heavy metal-polluted water.

Kinetics, isotherms, and thermodynamic studies of lead, chromium, and cadmium bio-adsorption from aqueous solution onto Picea smithiana sawdust.

Lead (Pb), chromium (Cr), and cadmium (Cd) removal capacity of sawdust (Picea smithiana) from aqueous solution was investigated by conducting batch experiments. Thermodynamic parameters, like change in standard free energy (ΔGΘ), enthalpy (ΔHΘ) and entropy (ΔSΘ) during bio-adsorption process were estimated using the Van't Hoff equation. The maximum metals adsorption was observed at pH 8, 20 g L-1 bio-adsorbent and at 60 min of contact time. The metal adsorption kinetics was examined by fitting the pseudo-first-order as well as four forms of pseudo-second-order kinetic models. Type 1 pseudo-second-order equation described adsorption kinetics better than others. Langmuir model and Freundlich equations were used for calculation of sorption parameters. The Langmuir maximum adsorption capacity of Pb, Cr, and Cd was 6.35, 3.37, and 2.87 mg g-1 at room temperature, respectively. The values of the separation factor (RL) were in between 0 and 1, indicating that bio-adsorption was favorable. Thermodynamics study revealed that the Pb, Cr, and Cd uptake reactions were endothermic and spontaneous. Results of the study asserted that the removal of heavy metal ions from aqueous solution is viable and the sawdust could be used in the treatment of effluents from industries, thereby reducing the level of water pollution.

Heavy metal phytoextraction-natural and EDTA-assisted remediation of contaminated calcareous soils by sorghum and oat.

The abilities of sorghum (Sorghum bicolor L.) and oat (Avena sativa L.) to take up heavy metals from soils amended with ethylenediaminetetraacetic acid (EDTA) were assessed under greenhouse conditions. Both plants were grown in two soils contaminated with heavy metals (Gujranwala-silty loam and Pacca-clay loam). The soils were treated with 0, 0.625, 1.25, and 2.5 mM EDTA kg-1 soil applied at both 45 and 60 days after sowing (DAS); the experiment was terminated at 75 DAS. Addition of EDTA significantly increased concentrations of Cd, Cr, and Pb in roots and shoots, and bio-concentration factors and phytoextraction rates were also increased. Post-harvest soil analysis showed that soluble fractions of metals were also increased significantly. The increase in Cd was ≈ 3-fold and Pb was ≈ 15-fold at the highest addition of EDTA in Gujranwala soil; in the Pacca soil, the increase was less. Similarly, other phytoremediation factors, such as metal translocation, bio-concentration factor, and phytoextraction, efficiency were also maximum when soils were treated with 2.5 mM EDTA kg-1 soil. The study demonstrated that sorghum was better than oat for phytoremediation.

Baseline water quality of municipal ponds and metal removal ability of Typha latifolia L. from sewage and industrial wastewaters.

Municipal effluent of three rural settings of Islamabad was assessed for physicochemical and microbiological parameters by collecting wastewater from inlet and center of ponds. Results showed that water quality was comparatively better at the center as Typha latifolia plants were growing toward the center of ponds. In another study, the wastewater treatment ability of T. latifolia was investigated by growing them in industrial and municipal effluent under greenhouse conditions. Water and plant samples were collected periodically (3rd, 10th, 17th, 24th, and 31st day after transplanting) for the measurement of Pb, Cu, and Cd concentrations. A decrease in heavy metal concentration of both effluents was observed as the experiment progressed and metal removal percentages ranged between 81% and 96%. Complementary the increase in metal concentration in plant tissues was observed over experimental period. Among plant tissues, metal concentration of Pb was highest i.e. 362 mg kg-1 in roots and 313 mg kg-1 in shoots at end of experiment. Pb, Cu, and Cd concentrations were higher in roots than shoots and hence translocation factors were less than 1.0. Metal removal efficiency was better from industrial wastewater and was in order of Pb > Cu > Cd. T. latifolia can be used for remediation of heavy metal-polluted wastewater.

The influences of Cr-tolerant rhizobacteria in phytoremediation and attenuation of Cr (VI) stress in agronomic sunflower (Helianthus annuus L.).

Chromium contamination of agronomic soil has to turn into a serious global problem. This research was pointed to assess the effects of three Cr-tolerant rhizobacteria (SS1, SS3, and SS6) on sunflower growth and heavy metal uptake under Cr smog i.e. 20, 30 and 40 ppm using K2Cr2O7. Root promotion assay and pot experiment were conducted to investigate and evaluate the effects of Cr tolerance rhizobacteria and Cr accumulation capacity of sunflower. From root promotion assay non-significant variation was observed in the root length between SS1 and SS3 compared with un-inoculated whereas SS6 enhanced the root length in the absence and presence of chromium. In addition, inoculation with rhizobacteria alleviated the Cr concentration and endorsed plant growth by enhancing Cr accumulation in sunflower. At different Cr levels, the Cr concentration in shoot was improved by each rhizobacterium though their difference was non-significant with each other, while the percentage increase was half as the Cr level doubled. Different rhizobacterium inoculation significantly (P < 0.05) affected the physiological and morphological characteristics of sunflower and increased the plant height, stem diameter, head diameter, grain yield, oil content of seeds, and total biomass, and among them, SS6 observed best followed by SS1 and SS3 comparing with un-inoculated. Our study illustrates an assessment about Cr-tolerant bacteria and their influences and recommends that these bacteria can effectively be used for crop improvement which provides a potential approach for Cr phytoremediation.

Phytoremediation potential of Lemna minor L. for heavy metals.

Phytoremediation potential of L. minor for cadmium (Cd), copper (Cu), lead (Pb), and nickel (Ni) from two different types of effluent in raw form was evaluated in a glass house experiment using hydroponic studies for a period of 31 days. Heavy metals concentration in water and plant sample was analyzed at 3, 10, 17, 24, and 31 day. Removal efficiency, metal uptake and bio-concentration factor were also calculated. Effluents were initially analyzed for physical, chemical and microbiological parameters and results indicated that municipal effluent (ME) was highly contaminated in terms of nutrient and organic load than sewage mixed industrial effluent (SMIE). Results confirmed the accumulation of heavy metals within plant and subsequent decrease in the effluents. Removal efficiency was greater than 80% for all metals and maximum removal was observed for nickel (99%) from SMIE. Accumulation and uptake of lead in dry biomass was significantly higher than other metals. Bio-concentration factors were less than 1000 and maximum BCFs were found for copper (558) and lead (523.1) indicated that plant is a moderate accumulator of both metals. Overall, L. minor showed better performance from SMIE and was more effective in extracting lead than other metals.

Removal of Cd, Cr, and Pb from aqueous solution by unmodified and modified agricultural wastes.

The adsorption of cadmium (Cd), chromium (Cr), and lead (Pb), widely detected in wastewater, by unmodified and modified banana stalks, corn cob, and sunflower achene was explored. The three agricultural wastes were chemically modified with sodium hydroxide (NaOH), in combination with nitric acid (HNO3) and sulfuric acid (H2SO4), in order to improve their adsorptive binding capacity. The experiments were conducted as a function of contact time and initial metal ion concentrations. Of the three waste materials, corn cob had the highest adsorptive capacity for Pb than Cr and Cd. The NaOH-modified substrates had higher adsorptive capacity than the acid modified samples. The chemical treatment invariably increased the adsorption capacity between 10 and 100 %. The Langmuir maximum sorption capacity (q m) of Pb was highest (21-60 mg g(-1) of banana, 30-57 mg g(-1) of corn cob, and 23-28 mg g(-1) of sunflower achene) and that of Cd was least (4-7 mg g(-1) of banana, 14-20 mg g(-1) of corn cob, and 11-16 mg g(-1) of sunflower achene). The q m was in the order of Pb > Cr > Cd for all the three adsorbents. The results demonstrate that the agricultural waste materials used in this study could be used to remediate water polluted with heavy metals.

EDTA-enhanced phytoremediation of contaminated calcareous soils: heavy metal bioavailability, extractability, and uptake by maize and sesbania.

Natural and chemically enhanced phytoextraction potentials of maize (Zea mays L.) and sesbania (Sesbania aculeata Willd.) were explored by growing them on two soils contaminated with heavy metals. The soils, Gujranwala (fine, loamy, mixed, hyperthermic Udic Haplustalf) and Pacca (fine, mixed, hyperthermic Ustollic Camborthid), were amended with varying amounts of ethylenediaminetetraacetic acid (EDTA) chelating agent, at 0, 1.25, 2.5, and 5.0 mM kg(-1) soil to enhance metal solubility. The EDTA was applied in two split applications at 46 and 60 days after sowing (DAS). The plants were harvested at 75 DAS. Addition of EDTA significantly increased the lead (Pb) and cadmium (Cd) concentrations in roots and shoots, uptake, bioconcentration factor, and phytoextraction rate over the control. Furthermore, addition of EDTA also significantly increased the soluble fractions of Pb and Cd in soil over the controls; the maximum increase of Pb and Cd was 13.1-fold and 3.1-fold, respectively, with addition of 5.0 mM EDTA kg(-1)soil. Similarly, the maximum Pb and Cd root and shoot concentrations, translocation, bioconcentration, and phytoextraction efficiency were observed at 5.0 mM EDTA kg(-1) soil. The results suggest that both crops can successfully be used for phytoremediation of metal-contaminated calcareous soils.