Identification of the Phytoremediation Potential of Indian mustard Genotypes for Copper,Evaluated from a Hydroponic Experiment

The effectiveness of 10 Indian mustard (Brassica juncea L.) genotypes (viz. Agrani, BTO, Kranti, Pusa Bahar, Pusa Basant, Pusa Bold, Pusa Jai Kisan, Vaibhav, Vardhan, and Varuna) were evaluated for their potential to phytoremediate copper from contaminated waters under laboratory controlled conditions. The genotypes were grown for 20 days in aqueous solutions containing various concentrations of copper sulfate (0–50 µM) in a hydroponic chamber. Throughout plant development, changes in growth variables, biomass accumulation, and total Cu content were evaluated. The results suggested that Indian mustard cv. Pusa Jai Kisan possesses the best capacities of Cu sequestration and tolerance amongst all the genotypes studied. Thus, Pusa Jai Kisan has the greatest potential to become a viable candidate in the development of practical phytoremediation technologies for Cu contaminated sites.     

Phytoremediation of heavy metal‐contaminated water and sediment by Eleocharis acicularis

Phytoremediation is an environmental remediation technique that takes advantage of plant physiology and metabolism. The unique property of heavy metal hyperaccumulation by the macrophyte Eleocharis acicularis is of great significance in the phytoremediation of water and sediments contaminated by heavy metals at mine sites. In this study, a field cultivation experiment was performed to examine the applicability of E. acicularis to the remediation of water contaminated by heavy metals. The highest concentrations of heavy metals in the shoots of E. acicularis were 20 200 mg Cu/kg, 14 200 mg Zn/kg, 1740 mg As/kg, 894 mg Pb/kg, and 239 mg Cd/kg. The concentrations of Cu, Zn, As, Cd, and Pb in the shoots correlate with their concentrations in the soil in a log‐linear fashion. The bioconcentration factor for these elements decreases log‐linearly with increasing concentration in the soil. The results indicate the ability of E. acicularis to hyperaccumulate Cu, Zn, As, and Cd under natural conditions, making it a good candidate species for the phytoremediation of water contaminated by heavy metals.     

Modelling of benzene distribution in the subsurface of an abandoned gas plant site after a long term of groundwater table fluctuation

The non‐aqueous phase liquid simulator was used to model and interpret the occurrence of a thin benzene‐contaminated soil layer 9.0 m below the groundwater table in an abandoned gas plant site. The simulator was first evaluated in column tests under similar conditions to the contaminated site. Saturation–capillary pressure (S–P) relationships were extended from the laboratory scale of the column tests to the field scale of the subsurface at the abandoned site. Dynamic boundary conditions were established in order to prevent the model from generating excessive vertical velocities. The modelled benzene layer formation process agreed well with the in situ observations. With falling and then rising of the water table, benzene release from the surface migrated downward and then upward and distributed itself below and above the water table. Biochemical degradation of benzene made the distribution discontinuous in the subsurface. These two factors resulted in the thin benzene‐contaminated layer below the groundwater table. Copyright © 2012 John Wiley & Sons, Ltd.     

A review of ecological risk assessment and associated health risks with heavy metals in sediment from India

Heavy metal (HM) pollution in sediment is a serious concern particularly in developing nations, warranting an extensive survey to understand the current situation and propose possible remedial measures. This paper compiles the data of HMs cadmium (Cd), iron (Fe), cobalt (Co), manganese (Mn), arsenic (As), lead (Pb), chromium (Cr), copper (Cu), zinc (Zn) and nickel (Ni) in aquatic sediment from India from 1979 to 2017. It was found that mean values of Cu, Co, Zn, Pb, As, and Cr in Indian sediment were high in comparison to the Australian Interim Sediment Quality Guidelines, World Surface Rock Average, and the Threshold Effect Level for freshwater ecosystems. Anthropogenic activities, lithogenic factors, and sand intrusion are the main factors associated with HM pollution as observed using cluster analysis and principal component analysis. The results of contamination indices indicate that HM contamination ranged from average to high, in the sediment. The ecological risk assessment results showed that 11% HMs present very high risk. The cancer risk, due to the high contents of Cd, As, and Cr the ingestion pathway, showed high risk of cancer through food/water contaminated with sediment. At source reduction of HMs in industrial effluents by effluent treatment plants, and plantation of phytoremediating rooted macrophytes in sediment may help in HM mitigation of the sediment.     

Field Treatment of MTBE‐Contaminated Groundwater Using Ozone/UV Oxidation

Methyl‐tertiary butyl ether (MTBE) is often found in groundwater as a result of gasoline spills and leaking underground storage tanks. An extrapolation of occurrence data in 2008 estimated at least one detection of MTBE in approximately 165 small and large public water systems serving 896,000 people nationally (United States Environmental Protection Agency [U.S. EPA] 2008). The objective of this collaborative field study was to evaluate a small groundwater treatment system to determine the effectiveness of ultraviolet (UV)/ozone treatment in removing MTBE from contaminated drinking water wells. A pilot‐scale advanced oxidation process (AOP) system was tested to evaluate the oxidation efficiency of MTBE and intermediates under field conditions. This system used ozone as an oxidizer in the presence of UV light at hydraulic retention times varying from 1 to 3 min. MTBE removal efficiencies approaching 97% were possible with this system, even with low retention times. The intermediate t‐butyl alcohol (TBA) was removed to a lesser extent (71%) under the same test conditions. The main intermediate formed in the oxidation process of the contaminated groundwater in these studies was acetone. The concentrations of the other anticipated intermediates t‐butyl formate (TBF), isopropyl alcohol (IPA), methyl acetate (MAc), and possible co‐occurring aromatics (BTEX) in the effluent were negligible.     

Phytoremediation of Sb,As, Cu,and Zn from Contaminated Water by the Aquatic Macrophyte Eleocharis acicularis

Sb, As, Cu, and Zn toxicity and contamination have become a growing concern in recent years. Phytoremediation, a plant based and cost effective technology, may be an effective approach in the cleanup of water contaminated by these metals. In this study, the aquatic macrophyte Eleocharis acicularis was used in laboratory and field experiments to assess its capability to accumulate Sb, As, Cu, and Zn, and thereby investigate its potential application in phytoremediation. The results showed that E. acicularis adapted well to water contaminated by these metals. The removal rates of Sb, As, Cu, and Zn in the laboratory experiment were 3.04, 2.75, 0.417, and 1.49 μg/L/day, respectively. The highest concentrations of these metals accumulated in E. acicularis after 10 days of the laboratory experiment were 6.29, 6.44, 20.5, and 73.5 mg/kg dry weight, respectively. Only 8% of As, 12% of Sb, 87% of Cu and 93% of Zn removed from the water were used by E. acicularis. The highest concentrations of Sb, As, Cu, and Zn accumulated in E. acicularis after 10 wk of the field experiment were 76.0, 22.4, 33.9, and 266 mg/kg dry weight, respectively. The results indicate that E. acicularis has the ability to accumulate Sb, As, Cu, and Zn from contaminated water.     

Improvement of a simplified process‐based model for estimating transpiration under water‐limited conditions

Plant transpiration depends on environmental conditions, and soil water availability is its primary control under water deficit conditions. In this study, we improve a simplified process‐based model (hereafter “BTA”) by including soil water potential (ψ_soil) to explicitly represent the dependence of plant transpiration on root‐zone moisture conditions. The improved model is denoted as the BTA‐ψ model. We assessed the performance of the BTA and BTA‐ψ models in a subtropical monsoon climate and a Mediterranean climate with different levels of water stress. The BTA model performed reasonably in estimating daily and hourly transpiration under sufficient water conditions, but it failed during dry periods. Overall, the BTA‐ψ model provided a significant improvement for estimating transpiration under a wide range of soil moisture conditions. Although both models could estimate transpiration (sap flow) at night, BTA‐ψ was superior to BTA in this regard. Species differences in the calibrated parameters of both models were consistent with leaf‐level photosynthetic measurements on each species, as expected given the physiological basis of these parameters. With a simplified representation of physiological regulation and reasonable performance across a range of soil moisture conditions, the BTA‐ψ model provides a useful alternative to purely empirical models for modelling transpiration.     

Numerical simulation of transport and sequential biodegradation of chlorinated aliphatic hydrocarbons using CHAIN_2D

Microbiological degradation of perchloroethylene (PCE) under anaerobic conditions follows a series of chain reactions, in which, sequentially, trichloroethylene (TCE), cis‐dichloroethylene (c‐DCE), vinylchloride (VC) and ethene are generated. First‐order degradation rate constants, partitioning coefficients and mass exchange rates for PCE, TCE, c‐DCE and VC were compiled from the literature. The parameters were used in a case study of pump‐and‐treat remediation of a PCE‐contaminated site near Tilburg, The Netherlands. Transport, non‐equilibrium sorption and biodegradation chain processes at the site were simulated using the CHAIN_2D code without further calibration. The modelled PCE compared reasonably well with observed PCE concentrations in the pumped water. We also performed a scenario analysis by applying several increased reductive dechlorination rates, reflecting different degradation conditions (e.g. addition of yeast extract and citrate). The scenario analysis predicted considerably higher concentrations of the degradation products as a result of enhanced reductive dechlorination of PCE. The predicted levels of the very toxic compound VC were now an order of magnitude above the maximum permissible concentration levels. Copyright © 1999 John Wiley & Sons, Ltd.     

Spatio‐temporal heterogeneity in soil water stable isotopic composition and its ecohydrologic implications in semiarid ecosystems

Spatio‐temporal heterogeneity in soil water content is recognized as a common phenomenon, but heterogeneity in the hydrogen and oxygen isotope composition of soil water, which can reveal processes of water cycling within soils, has not been well studied. New advances are being driven by measurement approaches allowing sampling with high density in both space and time. Using in situ soil water vapour probe techniques, combined with conventional soil and plant water vacuum distillation extraction, we monitored the hydrogen and oxygen stable isotopic composition of soil and plant waters at paired sites dominated by grasses and Gambel's oak (Quercus gambelii) within a semiarid montane ecosystem over the course of a growing season. We found that sites spaced only 20 m apart had profoundly different soil water isotopic and volumetric conditions. We document patterns of depth‐ and time‐explicit variation in soil water isotopic conditions at these sites and consider mechanisms for the observed heterogeneity. We found that soil water content and isotopic variability were damped under Q. gambelii, perhaps due in part to hydraulic redistribution of deep soil water or groundwater by Q. gambelii in these soils relative to the grass‐dominated site. We also found some support for H isotope discrimination effects during water uptake by Q. gambelii. In this ecosystem, the soil water content was higher than that at the neighbouring Grass site, and thus, 25% more water was available for transpiration by Q. gambelii compared with the Grass site. This work highlights the role of plants in governing soil water variation and demonstrates that they can also strongly influence the isotope ratios of soil water. The resulting fine‐scale heterogeneity has implications for the use of isotope tracers to study soil hydrology and evaporation and transpiration fluxes to improve understanding of water cycling through the soil–plant–atmosphere continuum.     

Rhizofiltration of a Heavy Metal (Lead) Containing Wastewater Using the Wetland Plant Carex pendula

Rhizofiltration is a subset technique of phytoremediation which refers to the approach of using plant biomass for removing contaminants, primarily toxic metals, from polluted water. The effective implementation of this in situ remediation technology requires experimental as well as conceptual insight of plant–water interactions that control the extraction of targeted metal from polluted water resources. Therefore, pot and simulation experiments are used in this study to investigate the rhizofiltration of a lead containing wastewater using plants of Carex pendula, a common wetland plant found in Europe. The metal contaminant extraction along with plant growth and water uptake rates from a wastewater having varying Pb concentration is studied experimentally for 2 wk. The temporal distribution of the metal concentration in the wastewater and the accumulated metal in different compartments of C. pendula at the end are analyzed using atomic absorption spectrometry. Parameters of the metal uptake kinetics are deduced experimentally for predicting the metal removal by root biomass. Further, mass balance equations coupled with the characterized metal uptake kinetics are used for simulating the metal partitioning from the wastewater to its accumulation in the plant biomass. The simulated metal content in wastewater and plant biomass is compared with the observed data showing a good agreement with the later. Results show that C. pendula accumulates considerable amounts of lead, particularly in root biomass, and can be considered for the cleanup of lead contaminated wastewaters in combination with proper biomass disposal alternatives. Also, the findings can be used for performing further non‐hydroponics experiment to mimic the real wetland conditions more closely.     

Requirements for the Catchment,Treatment, and Surveillance of Drinking Water To Avoid the Transmittance of Pathogenic Bacterial,Viral, and Parasitic Organisms

Measures devised for guaranteeing the supply of epidemiologically and hygienically sound drinking water are generally based on observations made during epidemics and the follow‐up scientific studies. Despite the high level standards that have been attained in the treatment of drinking water, the drinking water‐derived outbreaks still keep cropping up even in the industrialized countries. The outbreaks of the parasites Giardia lamblia and Cryptosporidium parvum, and the recent outbreak in Canada caused by Toxoplasma gondii, again focused our attention to the possible infection risk posed by pathogens in drinking water. The circumstances of the cryptosporidia outbreak in Milwaukee in 1993 can be considered as typical for such outbreaks in which parasites have caused human disease. There are generally two ways of avoiding the transmittance of pathogens by drinking water: (i) use of uncontaminated groundwater, or (ii) treatment of the potentially contaminated one. All surface waters have to be considered potentially contaminated, while the purity of the groundwater depends on the local conditions. Routine disinfection of drinking water should be used to minimize the residual risk posed by pathogens. For purification of fecally contaminated water it is utterly inadequate. Testing of water for pathogens followed by more extensive decontamination measures in the case of positive findings appears to be of little value.     

Phytoremediation of Cadmium‐Contaminated Soil by Two Jerusalem Artichoke (Helianthus tuberosus L.) Genotypes

Jerusalem artichoke (Helianthus tuberosus L.) can be used not just for bioethanol production, bur potentially also for soil phytoremediation via removal of heavy metal pollutants. An experiment was carried out to characterize the phytoextraction efficiency of two Jerusalem artichoke genotype (NY2 and NY5) in cadmium (Cd) contaminated soil. After 90 days of growth, NY5 had greater plant biomass and greater Cd accumulation in tissues than NY2. The chlorophyll content and chlorophyll a fluorescence parameters were slightly higher when plants were grown in Cd‐contaminated versus control soil. It implies that this examined NY2 and NY5 can extract more Cd than some hyperaccumulators, indicating that NY2 and NY5 can be applied to clean up Cd‐contaminated soils. Compared with NY2, NY5 had higher phytoextraction potential due to more biomass and higher concentrations of Cd in tissues, and may therefore be the better candidates for phytoremediation in Cd‐contaminated soil.     

Amending Soils with Hydrogels Increases the Biomass of Nine Tree Species under Non‐water Stress Conditions

The classical aim of the application of super absorbent polyacrylate (SAPs) hydrogels is the prolonging of plant survival under water stress. Their effect on plant growth during non‐water stress conditions is not known. This study examined the root and shoot biomass of seedlings of nine tree species; Eucalyptus grandis, Eucalyptus citriodora, Pinus caribaea, Araucaria cunninghamii, Melia volkensii, Grevillea robusta, Azadirachta indica, Maesopsis eminii and Terminalia superba. The seedlings were potted in five soil types; sand, sandy loam, loam, silt loam and clay. These were amended at two hydrogel levels: 0.2 and 0.4% w/w and grown under controlled conditions in a green house. Root and shoot growth responses of the seedlings were determined by measuring the dry weight of the roots, stems, leaves and twigs. The addition of either 0.2 or 0.4% hydrogel to the five soil types resulted in a significant increase of the root dry weight (p < 0.001) in eight tree species compared to the controls after 8 wk of routine watering. Also, the dry weight of stems and leaves and twigs were significantly (p < 0.001) higher in the nine tree species potted in hydrogel amended soil types than in the hydrogel free controls. These results suggested that hydrogel amendment enhances the efficiency of water uptake and utilization of photosynthates of plants grown in soils which have water contents close to field capacity.     

The effect of truck traffic and road water content on sediment delivery from unpaved forest roads

A study investigated the effect of truck‐traffic intensity and road water‐content on the quality of runoff water from unsealed forest roads. Three sections of a gravel‐surfaced forest road were instrumented and exposed to low and high levels of truck traffic during wet winter conditions and dry summer conditions between July 2001 and December 2002. Rainfall, runoff, road moisture, and traffic were measured continuously, and suspended and bedload sediments were integrated measurements over 2‐week site‐service intervals. The median suspended sediment concentration from the three road segments under low truck‐traffic conditions (less than nine return truck passes prior to a storm) was 269 mg l^?1, increasing 2·7‐fold to a median of 725 mg l^?1 under high truck‐traffic conditions (greater than or equal to nine return truck passes prior to a storm). These concentrations, and increases due to traffic, are substantially less than most previously reported values. When these data are expressed as modified universal soil loss equation (MUSLE) erodibility values K, accounting for differences in rainfall energy, site characteristics and runoff, high traffic resulted in a road surface that was four times more erodible than the same road under low traffic conditions. Using multiple regression, traffic explained 36% of the variation in MUSLE erodibility, whereas road water content was not significant in the model. There was little difference in the erodibility of the road when trafficked in low water‐content compared with high water‐content conditions (MUSLE K values of 0·0084 versus 0·0080 respectively). This study shows that, for a good quality well‐maintained gravel forest road, the level of truck traffic affects the sediment concentration of water discharging from the road, whereas the water content of the road at the time of that traffic does not (note that traffic is not allowed during runoff events in Victoria). These conclusions are conditional upon the road being adequately maintained so that trafficking does not compromise the lateral drainage of the road profile. Copyright © 2005 John Wiley & Sons, Ltd.     

Effects of Salinity and Mangrove Detritus on Desorption of Metals from Brackish Water Desorption of Metals from Brackish Water and Shrimp

Desorption and bioaccumulation of Cd, Zn, and Pb were studied using naturally contaminated sediment from a brackish water pond in the Sunderban Biosphere Reserve in India. Pattern of desorption of the metals from the sediment and bioaccumulation in fingerlings of the teleost Oreochromis mossambicusand postlarvae of the shrimp Penaeus monodon were studied as a function of salinity and loading of detritus of a mangrove plant. Effects of both salinity and loading of detritus on bioaccumulation of the metals were studied under two conditions: either the animals were allowed free access to the sediment or access was denied. Ninety‐six hour experiments showed that desorption of Cd and Pb from sediment into water increased with salinity of the medium while desorption of Zn decreased. Salinity of the medium also had a significant effect on the bioaccumulation of metals by fish; Cd and Pb accumulation decreased in saline medium while the accumulation of Zn increased. Conditions of access to sediment had no effect on the bioaccumulation of metals by fish; effect of interaction between salinity and access condition was also insignificant. The access conditions, however, significantly influenced accumulation of metal by the shrimp postlarvae. The effect of interaction between salinity and access condition was insignificant in influencing the bioaccumulation of all metals except Zn. The accumulation of Zn increased as a function of the salinity of the medium when shrimp postlarvae were allowed access to the sediment. Desorption of metals from sediment to water were below detection limits when detritus of a mangrove plant was added to the medium. Both the level of detritus and the conditions of access influenced accumulation of metals by fish, but the effect of interaction between the two factors were found to be insignificant. Shrimp postlarvae showed net accumulation only of Pb in the presence of detritus and the accumulation of Pb increased when the larvae were separated from the sediment. The results are important in understanding the mobility of metals between solid and aqueous phases in brackish water environments that experience periodic fluctuations in salinity and fluxes of organic load in the form of mangrove detritus.     

An integrated procedure to evaluate hydrological models

The growing concern for health‐related problems deriving from pollutants leaching is driving national and international administrations to support the development of tools for evaluating the effects of alternate management scenarios and identifying vulnerable areas. Cropping systems models are powerful tools for evaluating leachates under different environmental, social, and management conditions. As percolating water is the transport vehicle for pollutants transport in soil, a reliable evaluation of water balance models is a fundamental prerequisite for investigating pesticides and nitrate fate. As specific approaches for the evaluation of multi‐layer evolution of state variables are missing, we propose a fuzzy‐based, integrated indicator (I_SWC: 0, best; 1, worst) for a comprehensive evaluation of soil water content (SWC) simulations. We aggregated error metrics with others quantifying the homogeneity of errors across different soil layers, the capability of models to reproduce complex dynamics function of both time and soil depth, and model complexity. We tested I_SWC on a sample dataset where the models CropSyst and CERES‐Wheat were used to simulate SWC for winter wheat systems. I_SWC revealed that, in the explored conditions, the global assessment of the two models' performances allowed identification of CropSyst as the best (average I_SWC = 0·441, with a value of 0·537 obtained by CERES‐Wheat), although each model prevailed for some of the metrics. CropSyst presented the highest accuracy (average agreement module = 0·400), whereas CERES‐Wheat's accuracy was slightly worse, although achieved with a simplified modelling approach (average Akaike Information Criterion = − 230·44), thereby favouring large‐area applicability. The non‐univocal scores achieved by the models for the different metrics support the use of multi‐metric evaluation approaches for quantifying the different aspects of water balance model performances. Copyright © 2010 John Wiley & Sons, Ltd.     

Measurement of evapotranspiration in a winter wheat field

Daily evapotranspiration from a winter wheat field on the North China Plain measured by large‐scale weighing lysimeter was linearly related to that measured by the Bowen ratio energy balance (BREB) technique. Soil evaporation averaged about 23·6% of evapotranspiration from the post‐winter dormancy revival stage to the grain ripening stage in 1999. On clear days during winter dormancy, about half of the net radiation flux R_n was used to warm soil. During the revival stage, conductive heat flux G also used most of the incoming R_n, but the ratio of latent heat flux λE to R_n increased. During the stem‐extension stage, λE was about 50% of R_n; thereafter, λE/R_n increased continually, but G remained less than 10% of R_n. During the ripening stage, λE was almost 90% of R_n. Evaporative fraction (EF) can be expressed as a function of plant status and atmospheric boundary layer conditions. The relationship between EF and available energy under moderate air temperature and vapour pressure deficit conditions was examined for five combinations of aerodynamic and canopy conductance. Although the theoretical relationship indicates that EF should be highly correlated to soil water content, the correlation has been difficult to identify under field conditions. However, we observed that there exists a threshold value of R_n ? G, above which EF is less than 1·0, and that the threshold value is lower under soil‐water deficit conditions than under abundant soil‐water conditions. Copyright © 2002 John Wiley & Sons, Ltd.     

The Potential of Eleocharis acicularis for Phytoremediation: Case Study at an Abandoned Mine Site

Phytoremediation, a plant‐based and cost‐effective technology for the cleanup of contaminated soil and water, is receiving increasing attention. In this study, the aquatic macrophyte Eleocharis acicularis was examined for its ability to take up multiple heavy metals and its potential application for phytoremediation at an abandoned mining area in Hokkaido, Japan. Elemental concentrations were measured in samples of E. acicularis, water, and soil collected from areas of mine tailing and drainage. The results reveal that Pb, Fe, Cr, Cu, Ni, and Mn accumulation in the plants increased over the course of the experiment, exceeding their initial concentrations by factors of 930, 430, 60, 25, 10, and 6, respectively. The highest concentrations of Fe, Pb, Zn, Mn, Cr, Cu, and Ni within the plants were 59500, 1120, 964, 388, 265, 235, and 47.4 mg/kg dry wt., respectively, for plants growing in mine drainage after 11 months of the experiment. These results indicate that E. acicularis is a hyperaccumulator of Pb. We also found high Si concentrations in E. acicularis (2.08%). It is likely that heavy metals exist in opal‐A within cells of the plant. The bioconcentration factors (BCF: ratio of metal concentration in the plant shoots to that in the soil) obtained for Cr, Cu, Zn, Ni, Mn, and Pb were 3.27, 1.65, 1.29, 1.26, 1.11, and 0.82, respectively. The existence of heavy metals as sulphides is thought to have restricted the metal‐uptake efficiency of E. acicularis at the mine site. The results of this study indicate that E. acicularis shows great potential in the phytoremediation of mine tailing and drainage rich in heavy metals.     

Biodegradation by Co‐inoculated Bacteria and Fungi Alleviates Adverse Effects of Red‐S3B on Growth and Nitrogen Uptake of Wheat

Textile wastewater contains huge quantities of nitrogen (N)‐containing azo‐dyes. Irrigation of crops with such wastewater adds toxic dyes into our healthy soils. One of the ways to prevent their entry to soils could be these waters after the dyes' biodegradation. Therefore, the present study was conducted to evaluate the impact of textile dyes on wheat growth, dye degradation efficiency of bacteria‐fungi consortium, and alleviation of dye toxicity in wheat by treatment with microbial consortium. Among dyes, Red‐S3B (3.19% N) was found to be the most toxic to germination and growth of seven‐day‐old wheat seedlings. Shewanella sp. NIAB‐BM15 and Aspergillus terreus NIAB‐FM10 were found to be efficient degraders of Red‐S3B. Their consortium completely decolorized 500 mg L^?1 Red‐S3B within 4 h. Irrigation with Red‐S3B‐contaminated water after treatment with developed consortium increased root length, shoot length, root biomass, and shoot biomass of 30‐day‐old wheat seedlings by 47, 18, 6, and 25%, respectively, than untreated water. Moreover, irrigation after microbial treatment of dye‐contaminated water resulted in 20 and 51% increase in shoot N content and N uptake, respectively, than untreated water. Thus, co‐inoculation of bacteria and fungi could be a useful bioremediation strategy for the treatment of azo‐dye‐polluted water.     

MNA as a Remedy for Arsenic Mobilized by Anthropogenic Inputs of Organic Carbon

The potential application of monitored natural attenuation (MNA) as a remedy for ground water contaminated with arsenic (As) is examined for a subset of contaminated sites, specifically those where naturally occurring As has been mobilized due to localized anthropogenic organic carbon (OC) releases. This includes sites subject to petroleum releases, exposure to landfill leachates, and OC additions for biostimulation of reductive dechlorination of chlorinated solvents. The key characteristic of these sites is that, under conditions prevailing before the anthropogenic OC introduction, the naturally occurring As in the subsurface was not mobile and did not adversely affect ground water quality. This suggests that, in the far-field (where background conditions are (re) established), As may be sequestered upon contact of the contaminated ground water with either or both the (uncontaminated) ambient ground water and the background aquifer minerals. The observed extents of elevated concentrations (or "footprints") of As and other chemical species, such as dissolved OC and iron (Fe), and related parameters, such as redox potential ( E _h) and dissolved oxygen, and their evolution over time can be used to assess the mobilization and sequestration of As and the potential feasibility of MNA as a remedial option. Ultimately, the capacity for As sequestration must be assessed in the context of the OC loading to the site, which may require "active" measures for source control. Monitoring is needed to confirm the continuing effectiveness of the MNA remedy or to indicate if contingency measures must be implemented.