Biomass, Nutrient, and Trace Element Accumulation and Partitioning in Cattail ( L.) during Wetland Phytoremediation of Municipal Biosolids

Metal accumulation in cattails cultured in soils flooded with artificial wastewater of varying pH and different levels of metals (Cr, Cd and Zn)

Toxic metals cause risks to the ecological environment. Typha latifolia L. is a good candidate to clean potentially toxic metals contaminated water or soil. However, limited research investigated the impact of environmental factors (e.g., pH, soil substrate, flood duration) on metal accumulations in cattails. In this study, cattails were cultured in soils flooded with artificial wastewater with varying pH (5, 7 or 9) and different levels of Cr, Cd and Zn for four weeks to investigate the interactions between environmental conditions and metal uptake in cattails. The metal content in biomass were measured by an inductively coupled plasma-optical emission spectrometer.

More Zn (>10,000 mg/kg dry biomass) entered plants compared to Cd and Cr (<1,000 mg/kg dry biomass). Approximately 80% of Zn from solutions with 50 mg/L Cd, 25 mg/L Cr, 250 mg/L Zn were removed by cattails. Most Cd and Cr were sorbed onto soils. Cattails exhibited relatively consistent performance in removing metals from wastewater with initial pH of 5, 7 or 9. The pH of all the solutions ended close to neutral after 4 weeks. More research is needed to further understand the influence of environmental conditions on metal uptakes in plants to improve phytoremediation efficiency.

A critical analysis of sources, pollution, and remediation of selenium, an emerging contaminant

Selenium (Se) is an essential metalloid and is categorized as emerging anthropogenic contaminant released to the environment. The rise of Se release into the environment has raised concern about its bioaccumulation, toxicity, and potential to cause serious damages to aquatic and terrestrial ecosystem. Therefore, it is extremely important to monitor Se level in environment on a regular basis. Understanding Se release, anthropogenic sources, and environmental behavior is critical for developing an effective Se containment strategy. The ongoing efforts of Se remediation have mostly emphasized monitoring and remediation as an independent topics of research. However, our paper has integrated both by explaining the attributes of monitoring on effective scale followed by a candid review of widespread technological options available with specific focus on Se removal from environmental media. Another novel approach demonstrated in the article is the presentation of an overwhelming evidence of limitations that various researchers are confronted with to overcome achieving effective remediation. Furthermore, we followed a holistic approach to discuss ways to remediate Se for cleaner environment especially related to introducing weak magnetic field for ZVI reactivity enhancement. We linked this phenomenal process to electrokinetics and presented convincing facts in support of Se remediation, which has led to emerge 'membrane technology', as another viable option for remediation. Hence, an interesting, innovative and future oriented review is presented, which will undoubtedly seek attention from global researchers.

Review of Typha spp. (cattails) as toxicity test species for the risk assessment of environmental contaminants on emergent macrophytes

Macrophytes play an important role in aquatic ecosystems, and thus are often used in ecological risk assessments of potentially deleterious anthropogenic substances. Risk assessments for macrophyte populations or communities are commonly based on inferences drawn from standardized toxicity tests conducted on floating non-rooted Lemna species, or submerged-rooted Myriophyllum species. These tests follow strict guidelines to produce reliable and robust results with legal credibility for environmental regulations. However, results and inferences from these tests may not be transferrable to emergent macrophytes due to their different morphology and physiology. Emergent macrophytes of the genus Typha L. are increasingly used for assessing phytotoxic effects of environmental stressors, although standardized testing protocols have not yet been developed for this genus. In this review we present a synthesis of previous toxicity studies with Typha, based on which we evaluate the potential to develop standard toxicity tests for Typha spp. with seven selection criteria: ecological relevance to the ecosystem; suitability for different exposure pathways; availability of plant material; ease of cultivation; uniform growth; appropriate and easily measurable toxicity endpoints; and sensitivity toward contaminants. Typha meets criteria 1-3 fully, criteria 4 and 5 partly based on current limited data, and we identify knowledge gaps that limit evaluation of the remaining two criteria. We provide suggestions for addressing these gaps, and we summarize the experimental design of ecotoxicology studies that have used Typha. We conclude that Typha spp. can serve as future standard test species for ecological risk assessments of contaminants to emergent macrophytes.

Phytoextraction of ciprofloxacin and sulfamethoxaxole by cattail and switchgrass

Cattail (Typha latifolia L.) and switchgrass (Panicum virgatum L.) can effectively remove inorganic contaminants from soils and biosolids, but their role in the attenuation of organic contaminants, such as antimicrobials, is currently poorly understood. Uptake by plants is one of several mechanisms by which plant-assisted attenuation of antimicrobials can be achieved. The objectives of this growth room study were to evaluate the plant uptake of ciprofloxacin (CIP) and sulfamethoxazole (SMX) and examine their partitioning between plant roots and aboveground biomass (AGB). Plant uptake of the two ¹⁴C labeled antimicrobials was studied at two environmentally relevant concentrations (5 and 10 μg L^-1). Plants were destructively sampled every 3-4 d during the 21-d growth period. Accumulation of CIP and SMX in both plant species was greater in the roots than in the AGB. The percentage uptake values of the two antimicrobials were significantly greater for cattail (34% for CIP, 20% for SMX) than for switchgrass (10% for both CIP and SMX). Translocation factors of the two antimicrobials were <1 for both plants, indicating slow movement of the antimicrobials from the roots to the shoots. For cattail roots, the BCF for CIP (1.58 L g^-1) was significantly greater than that for SMX (0.8 L g^-1). By comparison, BCFs for switchgrass roots did not differ significantly between CIP (0.88 L g^-1) and SMX (1.13 L g^-1). These results indicate greater potential for cattail to phytoextract CIP and SMX and significantly contribute to the attenuation of these antimicrobials in systems designed for the phytoremediation of contaminated wastewater.

Cadmium-tolerant endophytic Pseudomonas rhodesiae strains isolated from Typha latifolia modify the root architecture of Arabidopsis thaliana Col-0 in presence and absence of Cd

In this work, we isolated four Cd-tolerant endophytic bacteria from Typha latifolia roots that grow at a Cd-contaminated site. Bacterial isolates GRC065, GRC066, GRC093, and GRC140 were identified as Pseudomonas rhodesiae. These bacterial isolates tolerate cadmium and have abilities for phosphate solubilization, siderophore production, indole acetic acid (IAA) synthesis, and ACC deaminase activity, suggesting that they are plant growth-promoting rhizobacteria. Bacterial inoculation in Arabidopsis thaliana seedlings showed that P. rhodesiae strains increase total fresh weight and number of lateral roots concerning non-inoculated plants. These results indicated that P. rhodesiae strains promote A. thaliana seedlings growth by modifying the root system. On the other hand, in A. thaliana seedlings exposed to 2.5 mg/l of Cd, P. rhodesiae strains increased the number and density of lateral roots concerning non-inoculated plants, indicating that they modify the root architecture of A. thaliana seedlings exposed to cadmium. The results showed that P. rhodesiae strains promote the development of lateral roots in A. thaliana seedlings cultivated in both conditions, with and without cadmium. These results suggest that P. rhodesiae strains could exert a similar role inside the roots of T. latifolia that grow in the Cd-contaminated environment.

Selenium Toxicity in Plants and Environment: Biogeochemistry and Remediation Possibilities

Selenium (Se) is a widely distributed trace element with dual (beneficial or toxic) effects for humans, animals, and plants. The availability of Se in the soil is reliant on the structure of the parental material and the procedures succeeding to soil formation. Anthropogenic activities affect the content of Se in the environment. Although plants are the core source of Se in animal and human diet, the role of Se in plants is still debatable. A low concentration of Se can be beneficial for plant growth, development, and ecophysiology both under optimum and unfavorable environmental conditions. However, excess Se results in toxic effects, especially in Se sensitive plants, due to changing structure and function of proteins and induce oxidative/nitrosative stress, which disrupts several metabolic processes. Contrary, Se hyperaccumulators absorb and tolerate exceedingly large amounts of Se, could be potentially used to remediate, i.e., remove, transfer, stabilize, and/or detoxify Se-contaminants in the soil and groundwater. Thereby, Se-hyperaccumulators can play a dynamic role in overcoming global problem Se-inadequacy and toxicity. However, the knowledge of Se uptake and metabolism is essential for the effective phytoremediation to remove this element. Moreover, selecting the most efficient species accumulating Se is crucial for successful phytoremediation of a particular Se-contaminated area. This review emphasizes Se toxicity in plants and the environment with regards to Se biogeochemistry and phytoremediation aspects. This review follows a critical approach and stimulates thought for future research avenues.

Selenium Toxicity in Plants and Environment: Biogeochemistry and Remediation Possibilities

Selenium (Se) is a widely distributed trace element with dual (beneficial or toxic) effects for humans, animals, and plants. The availability of Se in the soil is reliant on the structure of the parental material and the procedures succeeding to soil formation. Anthropogenic activities affect the content of Se in the environment. Although plants are the core source of Se in animal and human diet, the role of Se in plants is still debatable. A low concentration of Se can be beneficial for plant growth, development, and ecophysiology both under optimum and unfavorable environmental conditions. However, excess Se results in toxic effects, especially in Se sensitive plants, due to changing structure and function of proteins and induce oxidative/nitrosative stress, which disrupts several metabolic processes. Contrary, Se hyperaccumulators absorb and tolerate exceedingly large amounts of Se, could be potentially used to remediate, i.e., remove, transfer, stabilize, and/or detoxify Se-contaminants in the soil and groundwater. Thereby, Se-hyperaccumulators can play a dynamic role in overcoming global problem Se-inadequacy and toxicity. However, the knowledge of Se uptake and metabolism is essential for the effective phytoremediation to remove this element. Moreover, selecting the most efficient species accumulating Se is crucial for successful phytoremediation of a particular Se-contaminated area. This review emphasizes Se toxicity in plants and the environment with regards to Se biogeochemistry and phytoremediation aspects. This review follows a critical approach and stimulates thought for future research avenues.

Sulfamethoxazole sorption by cattail and switchgrass roots

Sorption to roots is one of several mechanisms by which plant-assisted attenuation of antibiotics can be achieved. The objectives of this study were to (1) evaluate the sorption of sulfamethoxazole (SMX) by cattail and switchgrass roots, (2) determine the kinetics of SMX sorption by cattail and switchgrass roots, and (3) characterize the temperature-dependency of SMX sorption. A batch sorption experiment was conducted to measure SMX sorption by roots of the two plant species using five initial antibiotic concentrations (2.5, 5, 10, 15, and 20 µg L^-1) and eight sampling times (0, 0.5, 1, 2, 4, 8, 12, and 24 h). Another batch experiment was conducted at three temperatures (5, 15, and 25 °C) to determine the effect of temperature on sorption kinetics. SMX sorption followed pseudo-second-order kinetics. The pseudo-second-order rate constant (k2) decreased with increasing temperature for both plant species. The rate constant followed the order: 5 °C = 15 °C > 25 °C for cattail and 5 °C > 15 °C = 25 °C for switchgrass. Results from this study show that switchgrass roots are more effective than cattail roots in the removal of SMX. Therefore, the use of switchgrass in systems designed for phytoremediation of contaminants might also provide an efficient removal of some antibiotics.

Phytoremediation and detoxification of xenobiotics in plants: herbicide-safeners as a tool to improve plant efficiency in the remediation of polluted environments. A mini-review

Phytoremediation is a widely studied and applied technology, based on the use of plants and their associated microorganisms to decontaminate polluted sites. In recent years, different strategies have been investigated to improve the phytoremediation efficiency of the selected plants. In this context, some studies have shown that herbicide-safeners, chemicals applied to crops to enhance their tolerance to herbicides, can increase the phytoremediation of soils and water polluted by organic and inorganic contaminants. Safeners, by inducing the xenobiotic detoxification and the antioxidant metabolism in plants, can enhance their removal potential in the cleaning process. In this review, after a short survey of phytoremediation technologies and the biochemical mechanisms activated by plants to tolerate and detoxify heavy metals and herbicides, the use of herbicide-safeners as a tool to increase the phytoremediation performance is reviewed and discussed.

Process Analysis of Anaerobic Fermentation Exposure to Metal Mixtures

Anaerobic fermentation is a cost-effective biowaste disposal approach. During fermentation, microorganisms require a trace amount of metals for optimal growth and performance. This study investigated the effects of metal mixtures on biogas properties, process stability, substrate degradation, enzyme activity, and microbial communities during anaerobic fermentation. The addition of iron (Fe), nickel (Ni), and zinc (Zn) into a copper (Cu)-stressed fermentation system resulted in higher cumulative biogas yields, ammonia nitrogen (NH₄⁺-N) concentrations and coenzyme F₄₂₀ activities. Ni and Zn addition enhanced process stability and acetate utilization. The addition of these metals also improved and brought forward the peak daily biogas yields as well as increased CH₄ content to 88.94 and 86.58%, respectively. Adding Zn into the Cu-stressed system improved the abundance of Defluviitoga, Fibrobacter and Methanothermobacter, the degradation of cellulose, and the transformation of CO₂ to CH₄. The bacterial and archaeal communities were responsible for the degradation of lignocelluloses and CH₄ production during the fermentation process. This study supports the reutilization of heavy metal-contaminated biowaste and provides references for further research on heavy metals impacted anaerobic fermentation.

Nitrogen and Phosphorus Phytoextraction by Cattail (Typha spp.) during Wetland-based Phytoremediation of an End-of-Life Municipal Lagoon

Spreading biosolids on farmland can be an effective and beneficial option for managing end-of-life municipal lagoons. Where the spreading of biosolids on farmland is restricted or unavailable, in situ phytoremediation could be a sustainable alternative. This study examined nitrogen (N) and phosphorus (P) phytoextraction by cattail ( spp.) from biosolids in a wetland constructed within a lagoon cell previously used for primary treatment of municipal wastewater. The effect of harvesting season as well as harvest frequency on N and P removal were evaluated. Forty-eight 4-m plots within the constructed wetland were used to determine the effect of cattail harvest frequency on plant N and P phytoextraction. Harvesting twice per season resulted in a 50 to 60% decrease in phytoextraction of N and P relative to a single harvest per season, which produced biomass yields of 0.58 to 0.6 kg m per year and accumulated 36.7 g N m and 5.6 g P m over the 4-yr period. Compared with August, harvesting cattails in November or April reduced N and P phytoextraction by 63 to 85%. These results demonstrate that phytoextraction of nutrients is more effective with a single harvest compared with two harvests per season. Additionally, we found that while harvesting in November and April is appealing logistically (since the wetland is frozen and provides easier access to harvest equipment), nutrient removal rates are significantly reduced.

A Field Bioassay of Nitrogen and Phosphorus Phytoextraction from Biosolids in a Seasonally Frozen End-of-Life Municipal Lagoon Vegetated with Cattail

Managing biosolids from end-of-life municipal lagoons is a major challenge for many small communities where landfilling or spreading of biosolids on farmland is restricted. Contaminant removal via phytoextraction may be a viable remediation option for end-of-life lagoons in such communities. This study examined the effect of harvest frequency (once or twice per season) on cattail ( L.) biomass yield and N and P removal under a terrestrial phytoremediation system designed to treat the dewatered secondary cell of a municipal lagoon in Manitoba, Canada. Cattail was harvested once or twice per season from eight vegetation transects, each divided into two plots (2.5 × 2.5 m) to accommodate the two harvest frequencies. Biomass yields were greater for the single harvest (5.7 t ha yr) than for two harvests per season (4.8 t ha yr). This was mirrored by N phytoextraction, which was also greater for the single harvest (71 kg ha yr) than the two-harvest frequency (58 kg ha yr). Phosphorus phytoextraction varied with year of harvest and ranged from 8 to 14 kg ha yr. Cumulative N and P phytoextraction amounts during the 5 yr were 330 kg N ha and 57 kg P ha. A greater fraction of N (51-91 kg ha yr) and P (23-40 kg ha yr) was sequestered in the belowground biomass (11-17 t ha yr) and therefore was not removed by harvesting. These results show that phytoremediation using cattail is a viable option for managing N and P in end-life lagoons.

Wetland-based phytoremediation of biosolids from an end-of-life municipal lagoon: A microcosm study

This study examined the effectiveness of a wetland system for phytoremediation of biosolids from an end-of-life municipal lagoon. The microcosm experiment tested the effects of one vs. two harvests of cattail per growth cycle in biosolids without (PB) or with (PBS) the addition of soil on phytoremediation. Cattail (Typha latifolia) seedlings were transplanted into pots containing 4.5 kg (dry wt.) of biosolids, above which a 10-cm deep water column was maintained. Results showed that two harvests per growth cycle significantly increased N and P phytoextraction relative to a single harvest. Overall, the three cycles of cattail removed ∼3.7% of N which was originally present in the biosolids and ∼2% of the total P content. Phytoextraction rates are expected to be higher under field conditions where biomass yields are much higher than those obtained under growth room conditions in this study. These results indicate that wetland-based phytoremediation can effectively clean up nutrients from biosolids, and therefore presents a potential alternative to the spreading of biosolids on agricultural land, which may not be readily available in some communities. Phytoextraction rates of trace elements, however, were much lower (0.02-0.17%). Nonetheless, trace element concentrations were not high enough to be of significant concern.

Phytoremediation of biosolids from an end-of-life municipal lagoon using cattail (Typha latifolia L.) and switchgrass (Panicum virgatum L.)

Land spreading of biosolids as a disposal option is expensive and can disperse pathogens and contaminants in the environment. This growth room study examined phytoremediation using switchgrass (Panicum virgatum L.) and cattail (Typha latifolia L.) as an alternative to land spreading of biosolids. Seedlings were transplanted into pots containing 3.9 kg of biosolids (dry wt.). Aboveground biomass (AGB) was harvested either once or twice during each 90-day growth period. Switchgrass AGB yield was greater with two harvests than with one harvest during the first 90-day growth period, whereas cattail yield was not affected by harvest frequency. In the second growth period, harvesting frequency did not affect the yield of either plant species. However, repeated harvesting significantly improved nitrogen (N) and phosphorus (P) uptake by both plants in the first period. Phytoextraction of P was significantly greater for switchgrass (3.9% of initial biosolids P content) than for cattail (2.8%), while plant species did not have a significant effect on N phytoextraction. The trace element accumulation in the AGB of both plant species was negligible. Phytoextraction rates attained in this study suggest that phytoremediation can effectively remove P from biosolids and offers a potentially viable alternative to the disposal of biosolids on agricultural land.

Accumulation and partitioning of biomass, nutrients, and trace elements in switchgrass for phytoremediation of municipal biosolids

In situ phytoremediation of municipal biosolids is a promising alternative to the land spreading and landfilling of biosolids from end-of-life municipal lagoons. Accumulation and partitioning of dry matter, nitrogen (N), phosphorus (P), and trace elements were determined in aboveground biomass (AGB) and belowground biomass (BGB) of switchgrass (Panicum virgatum L.) to determine the harvest stage that maximizes phytoextraction of contaminants from municipal biosolids. Seedlings were transplanted into 15-L plastic pails containing 3.9 kg (dry wt.) biosolids. Biomass yield components and contaminant concentrations were assessed every 14 days for up to 161 days. Logistic model fits to biomass yield data indicated no significant differences in asymptotic yield between AGB and BGB. Switchgrass partitioned significantly more N and P to AGB than to BGB. Maximum uptake occurred 86 days after transplanting (DAT) for N and 102 DAT for P. Harvesting at peak aboveground element accumulation removed 5% of N, 1.6% of P, 0.2% of Zn, 0.05% of Cd, and 0.1% of Cr initially present in the biosolids. These results will contribute toward identification of the harvest stage that will optimize contaminant uptake and enhance in situ phytoremediation of biosolids using switchgrass.

Moisture Effects on Nitrogen Availability in Municipal Biosolids from End-of-Life Municipal Lagoons

Nitrogen (N) availability affects plant biomass yield and, hence, phytoextraction of contaminants during phytoremediation of end-of-life municipal lagoons. End-of-life lagoons are characterized by fluctuating moisture conditions, but the effects on biosolid N dynamics have not been adequately characterized. This 130-d laboratory incubation investigated effects of three moisture levels (30, 60, and 90% water-filled pore space [WFPS]) on N mineralization (N) in biosolids from a primary (PB) and a secondary (SB) municipal lagoon cell. Results showed a net increase in N with time at 60% WFPS and a net decrease at 90% WFPS in PB, while N at 30% WFPS did not change significantly. Moisture level and incubation time had no significant effect on N in SB. Nitrogen mineralization rate in PB followed three-half-order kinetics. Potentially mineralizable N (N) in PB was significantly greater at 60% WFPS (222 mg kg) than at 30% WFPS (30 mg kg), but rate constants did not differ significantly between the moisture levels. Nitrogen mineralization in SB followed first-order kinetics, with N significantly greater at 60% WFPS (68.4 mg kg) and 90% WFPS (94.1 mg kg) than at 30% WFPS (32 mg kg). Low N in SB suggests high-N-demanding plants may eventually have limited effectiveness to remediate biosolids in the secondary cell. While high N in PB would provide sufficient N to support high biomass yield, phytoextraction potential is reduced under dry and near-saturated conditions. These results have important implications on the management of moisture during phytoextraction of contaminants in end-of-life municipal lagoons.