Suitability of select micro-green, ornamental and legume plants for use in green walls: a novel brewery wastewater treatment option.

Green walls are increasingly popular in urban settings with demonstrated beneficial use as vertical gardens, building envelops, and uniquely orientated green space to improve urban biodiversity and air quality. This research evaluated the suitability of green wall plants for the preliminary treatment of wastewater generated by food and beverage makers, quantifying suitability with plant growth metrics. Edible micro-green, ornamental, and legume plants were planted in perlite filled pots and irrigated continuously with untreated brewery wastewater or a control of Hoaglands solution. Plants receiving wastewater had less growth than the control. Stem growth for microgreen and legume plants that were started from seed was 798% and 253% less, respectively, when irrigated with 100% brewery wastewater. The stem growth of established ornamental plants was 26% less when irrigated with the wastewater. Wastewater irrigated plants with the highest rates of growth and survivability included the mustard plant (Brassica juncea), and ornamental plants Epipremnum aureum (Golden Pothos) and Chlorophytum comosum (Spider Plant). Growth metrics for wastewater irrigated legumes were higher for plants inoculated with rhizobia, than plants without the inoculation, which suggests low available nitrogen concentrations, rather than toxicity of the wastewater, limited plant growth. The results suggest that ornamental plants such as Epipremnum aureum and Chlorophytum comosum can be sustained, without the addition of supplemental nutrients, in a green wall utilized to treat brewery wastewater.

Suitability of select media for use in a novel green wall system used to treat brewery wastewater.

Green walls are becoming increasingly popular as pleasing architectural installations and functional systems in sustainable urban building designs. However, utilization of green walls as an aqueous treatment option has been primarily limited to grey water. This study evaluates select media as appropriate support for plants and microorganisms in a novel green wall system used to treat wastewater from craft and micro-breweries. The media must have hydraulic capacity to treat large volumes of brewery wastewater, be lightweight and commercially available, and provide structure for plant roots and biofilm development. Two expanded recycled glass aggregates (Growstone® and Poraver®) and a lightweight expanded clay aggregate (Hydroton®) were evaluated, having a d50 range from 6 to 12 mm. To assess media performance, this study determined hydraulic characteristics and evaluated the growth of leafy green plants and microorganism populations irrigated with 100% raw brewery wastewater. It was determined that media with a particle d50 = 12 mm would facilitate a hydraulic loading rate of 1623 m3/m2/day media under unsaturated conditions and not result in interstitial velocities that shear away biofilm. No significant difference in plant growth metrics, microorganism type or cell density were observed between media. There were nearly three orders of magnitude more bacteria colonies than yeast CFU in biofilm. This innovative application of green walls has the potential to provide manufacturers of fermented beverages with a treatment option that has a low capital cost, simple to operate, and a small footprint, thereby avoiding traditional treatment processes and/or high sewer use fees.

Exposure of tomato (Lycopersicon esculentum) to silver nanoparticles and silver nitrate: physiological and molecular response.

Silver nanoparticles (AgNPs) are among the most widely used nanomaterials, with applications in sectors as diverse as communications, energy, medicine, and agriculture. This diverse application of AgNPs increases the risk of the release of these materials into the environment and raises the potential for transfer into plants and, subsequently, the human body. To better understand the effects of NPs in agricultural systems, this study investigates plant physiological and molecular responses upon exposure to AgNPs in comparison to silver nitrate (AgNO3). Tomato seedlings (Lycopersison esculentum) were exposed to 10, 20, or 30 mg/L silver (Ag), AgNO3, or AgNPs in hydroponic media for 7 days. A number of endpoints were measured, including plant growth, photosynthetic pigments, oxidative and antioxidant responses. The results showed 2-7 times lower growth rate in plants exposed to silver compared to the control. H2O2 and malondialdehyde as oxidative stress indicators were, respectively, 1.7 and 4 times higher in plants exposed to all forms of silver compared to the control. The antioxidative responses increased significantly in plants exposed to Ag and AgNPs compared to the control. However, plants exposed to AgNO3 showed up to 50% lower enzymatic antioxidant activity. At the molecular level, the expression of genes involved in defense responses, including ethylene-inducing xylanase (EIX), peroxidase 51 (POX), and phenylalanine ammonia lyase, were significantly upregulated upon exposure to silver. The molecular and physiological data showed exposure to all forms of silver resulted in oxidative stress and exposure to AgNPs induced antioxidative and defense responses. However, exposure to AgNO3 resulted in phytotoxicity and failure in antioxidative responses. It indicates the higher reactivity and phytotoxicity of the ionic form of silver compared to NPs. The findings of this study add important information to efforts in attempting to characterize the exposure and risk associated with the release of nanomaterials in the environment.

Leucanthemum vulgare lam. crude oil phytoremediation.

Sites with crude oil pollution have been successfully treated using phytoremediation, but expanding the range of plants that can be used and understanding how exposure impacts the plants are two areas of study that are important to continue. Leucanthemum vulgare has been shown to grow well under a variety of stressful conditions. To examine L. vulgare's ability to both survive crude oil exposure and to reduce crude oil concentrations in soil, plants were placed in soil containing 0, 2.5, 5, 7.5, or 10% w/w crude oil. Total petroleum hydrocarbons (TPH) concentration, peroxidase and catalase activity, proline and phenol content in roots and leaves were determined at the start of planting and every 2 months for 6 months. L. vulgare roots were successfully colonized with mycorrhizae under all conditions. Results showed positive correlation between antioxidant compound concentration and crude oil contamination. Also, a significant reduction occurred in TPH content of soil over time in planted pots as compared to controls. The lowest TPH content was recorded after 6 months under all treatments. Results showed L. vulgare could survive crude oil exposure and enhance reducing of crude oil from soil.

Terrestrial Trophic Transfer of Bulk and Nanoparticle La2O3 Does Not Depend on Particle Size.

The bioaccumulation and trophic transfer of bulk and nanoparticle (NP) La2O3 from soil through a terrestrial food chain was determined. To investigate the impact of growth conditions, lettuce (Lactuca sativa) was grown in 350 or 1200 g of bulk/NP amended soil. Leaf tissues were fed to crickets (Acheta domesticus) or darkling beetles (Tenebrionoidea); select crickets were fed to mantises. In the small pot (350 g), La2O3 exposure reduced plant biomass by 23-30% and La tissue content did not differ with particle size. In the large pot (1200 g), biomass was unaffected by exposure and La content in the tissues were significantly greater with bulk particle treatment. Darkling beetles exposed to bulk and NP La2O3-contaminated lettuce contained La at 0.18 and 0.08 mg/kg; respectively (significantly different, P < 0.05). Crickets fed bulk or NP La2O3-exposed lettuce contained 0.53 and 0.33 mg/kg, respectively (significantly different, P < 0.05) with 48 h of depuration. After 7 d of depuration, La content did not differ with particle size, indicating that 48 h may be insufficient to void the digestive system. Mantises that consumed crickets from bulk and NP-exposed treatments contained La at 0.05-0.060 mg/kg (statistically equivalent). These results demonstrate that although La does trophically transfer, biomagnification does not occur and NP levels are equivalent or less than the bulk metal.

Particle-size dependent accumulation and trophic transfer of cerium oxide through a terrestrial food chain.

The accumulation and trophic transfer of nanoparticle (NP) or bulk CeO2 through a terrestrial food chain was evaluated. Zucchini (Cucurbita pepo L.) was planted in soil with 0 or 1228 µg/g bulk or NP CeO2. After 28 d, zucchini tissue Ce content was determined by ICP-MS. Leaf tissue from each treatment was used to feed crickets (Acheta domesticus). After 14 d, crickets were analyzed for Ce content or were fed to wolf spiders (family Lycosidae). NP CeO2 significantly suppressed flower mass relative to control and bulk treatments. The Ce content of zucchini was significantly greater when exposure was in the NP form. The flowers, leaves, stems, and roots of zucchini exposed to bulk CeO2 contained 93.3, 707, 331, and 119,000 ng/g, respectively; NP-exposed plants contained 153, 1510, 479, and 567 000 ng/g, respectively. Crickets fed NP CeO2-exposed zucchini leaves contained significantly more Ce (33.6 ng/g) than did control or bulk-exposed insects (15.0-15.2 ng/g). Feces from control, bulk, and NP-exposed crickets contained Ce at 248, 393, and 1010 ng/g, respectively. Spiders that consumed crickets from control or bulk treatments contained nonquantifiable Ce; NP-exposed spiders contained Ce at 5.49 ng/g. These findings show that NP CeO2 accumulates in zucchini at greater levels than equivalent bulk materials and that this greater NP intake results in trophic transfer and possible food chain contamination.

Multiwalled carbon nanotubes and c60 fullerenes differentially impact the accumulation of weathered pesticides in four agricultural plants.

The effect of multiwalled carbon nanotubes (MWCNT) or C60 fullerenes on the uptake of weathered chlordane or DDx (DDT + metabolites) by Cucurbita pepo (zucchini), Zea mays (corn), Solanum lycopersicum (tomato), and Glycine max (soybean) was investigated. The plants were grown in 50 g of soil with weathered chlordane (2150 ng/g) and DDx (118 ng/g) that was amended with 0, 500, 1000, or 5000 mg/kg MWCNT or C60. After 28 d, the root and shoot content of chlordane components and DDx was determined by GC-MS. Zucchini and tomato growth were unaffected by carbon nanomaterial coexposure, although C60 at 500 mg/kg reduced corn and soybean biomass by 36.5-45.0%. Total chlordane content ranged from 1490 (tomato) to 4780 (zucchini) ng; DDx amounts ranged from 77.8 (corn) to 395 ng (zucchini). MWCNT coexposure decreased chlordane and DDx accumulation 21-80% across all crops, depending on species and nanotube concentration. Conversely, C60 had species- and contaminant-specific effects on pesticide uptake, ranging from complete suppression of DDx uptake (corn/tomato) to 34.9% increases in chlordane accumulation (tomato/soybean). The data show that pesticide accumulation varies greatly with crop species and carbon nanomaterial type/concentration. These findings have implications for food safety and for the use of engineered nanomaterials in agriculture.

Phytotechnologies--preventing exposures, improving public health.

Phytotechnologies have potential to reduce the amount or toxicity of deleterious chemicals and agents, and thereby, can reduce human exposures to hazardous substances. As such, phytotechnologies are tools for primary prevention in public health. Recent research demonstrates phytotechnologies can be uniquely tailored for effective exposure prevention in a variety of applications. In addition to exposure prevention, plants can be used as sensors to identify environmental contamination and potential exposures. In this paper, we have presented applications and research developments in a framework to illustrate how phytotechnologies can meet basic public health needs for access to clean water, air, and food. Because communities can often integrate plant-based technologies at minimal cost and with low infrastructure needs, the use of these technologies can be applied broadly to minimize potential contaminant exposure and improve environmental quality. These natural treatment systems also provide valuable ecosystem services to communities and society. In the future, integrating and coordinating phytotechnology activities with public health research will allow technology development focused on prevention of environmental exposures to toxic compounds. Hence, phytotechnologies may provide sustainable solutions to environmental exposure challenges, improving public health and potentially reducing the burden of disease.

Impact of Ag nanoparticle exposure on p,p'-DDE bioaccumulation by Cucurbita pepo (zucchini) and Glycine max (soybean).

The effect of nanoparticle (NP), bulk, or ionic Ag exposure on dichlorodiphenyldichloroethylene (p,p'-DDE; DDT metabolite) accumulation by Glycine max L. (soybean) and Cucurbita pepo L. (zucchini) was investigated. The plants were grown in 125-mL jars of vermiculite amended with 500 or 2000 mg/L of bulk or NP Ag; ion controls at 5 and 20 mg/L were established. During 19 d of growth, plants were amended with solution containing 100 ng/mL of p,p'-DDE. Total shoot p,p'-DDE levels in non-Ag exposed G. max and C. pepo were 500 and 970 ng, respectively; total root DDE content was 13,700 and 20,300 ng, respectively. Ag decreased the p,p'-DDE content of G. max tissues by up to 40%, with NP exposure resulting in less contaminant uptake than bulk Ag. Total Ag content of exposed G. max ranged from 50.5 to 373 µg; NP-exposed plants had 1.9-2.2 times greater overall Ag than corresponding bulk particle treatments and also significantly greater relative Ag transport to shoot tissues. Bulk and NP Ag at 500 mg/L suppressed DDE uptake by C. pepo by 21-29%, although Ag exposure at 2000 mg/L had no impact on contaminant uptake. Similar to G. max , C. pepo whole plant Ag content ranged from 50.5 to 182 µg, with tissue element content generally being greater for NP exposed plants. These findings show that the Ag may significantly alter the accumulation and translocation of cocontaminants in agricultural systems. Notably, the cocontaminant interactions vary both with Ag particle size (NP vs bulk) and plant species. Future investigations will be needed to clarify the mechanisms responsible for the cocontaminant interactions and assess the impact on overall exposure and risk.

Fullerene-enhanced accumulation of p,p'-DDE in agricultural crop species.

The effect of C(60) fullerene exposure on the accumulation of dichlorodiphenyldichloroethylene (p,p'-DDE; DDT metabolite) by Cucurbita pepo L. (zucchini), Glycine max L. (soybean), and Solanum lycopersicum L. (tomato) was determined. The plants were grown in 125 mL jars of vermiculite amended with 0 or 40 mg of C(60) fullerenes. Prior to planting, the jars were amended with 40 mL solution containing 100 ng/mL of p,p'-DDE with 0 or 100 mg/L humic acid. During three weeks of growth, plants were watered with the same p,p'-DDE containing solutions. Total shoot p,p'-DDE levels in nonfullerene exposed tomato, soybean, and zucchini were 26.9, 131, and 675 ng, respectively; total root DDE content for the three plants was 402, 5970, and 5830 ng, respectively. Fullerenes increased the shoot p,p'-DDE content of zucchini by 29%; contaminant levels in soybean shoots were decreased by 48% but tomato shoot content was unaffected. The root and total plant p,p'-DDE content of all three species was significantly increased by fullerene exposure; enhanced contaminant uptake ranged from 30 to 65%. Humic acid, regardless of fullerene presence or plant type, significantly decreased the p,p'-DDE uptake. Fullerenes were detected in the roots of all plants but were not detected in plant shoots in the initial study. In a follow up study with zucchini designed to maximize biomass for extraction, over half the analyzed stems contained fullerenes at 60.5 to 4490 ng/g. These findings show that the carbon-based nanomaterials may significantly alter the accumulation and potentially the toxicity of cocontaminants in agricultural systems.

Uptake, distribution and toxicity of gold nanoparticles in tobacco (Nicotiana xanthi) seedlings.

Understanding plant interactions with nanoparticles is of increasing importance for assessing their toxicity and trophic transport. The primary objective of this study was to assess uptake, biodistribution and toxicity associated with exposure of tobacco plants (Nicotiana xanthi) to gold nanoparticles (AuNPs). We employed synchrotron-based X-ray microanalysis with X-ray absorption near-edge microspectroscopy and high resolution electron microscopy to localize AuNPs within plants. Results from these experiments reveal that AuNPs entered plants through the roots and moved into the vasculature. Aggregate bodies were also detected within root cell cytoplasm. Furthermore, AuNP uptake was size selective as 3.5 nm AuNP spheres were detected in plants but 18 nm AuNPs remained agglomerated on the root outer surfaces. Finally, leaf necrosis was observed after 14 days of exposure to 3.5 nm AuNPs. Overall, results of this work show the potential for AuNPs to enter plants through size-dependent mechanisms, translocate to cells and tissues and cause biotoxicity.

Bacteria and phytoremediation: new uses for endophytic bacteria in plants.

The use of plants and bacterial to clean up environmental pollutants has gained momentum in past years. A limitation to phytoremediation of solvents has been toxicity of the compounds to plants, and the uncertainty as to the fate of many of the compounds. In a recent study, engineered endophytes have been shown to increase plant tolerance to toluene, and to decrease the transpiration of toluene to the atmosphere. This type of work has the potential to increase the use of phytoremediation by decreasing toxicity and increasing degradation of toxins.

Phytodegradation of organic compounds.

The phytodegradation of organic compounds can take place inside the plant or within the rhizosphere of the plant. Many different compounds and classes of compounds can be removed from the environment by this method, including solvents in groundwater, petroleum and aromatic compounds in soils, and volatile compounds in the air. Although still a relatively new area of research, there are many laboratories studying the underlying science necessary for a wide range of applications for plant-based remediation of organic contaminants.

Metabolism of the soil and groundwater contaminants, ethylene dibromide and trichloroethylene, by the tropical leguminous tree, Leuceana leucocephala.

Ethylene dibromide (EDB; dibromoethane) and trichloroethylene (TCE) are hazardous environmental pollutants. The use of plants to treat polluted sites and groundwater, termed phytoremediation, requires plants that can both effectively remove the pollutant as well as grow in the climatic region of the site. In this paper, we report that the tropical leguminous tree, Leuceana leucocephala var. K636, is able to take up and metabolize EDB and TCE. The plants were grown in sterile hydroponic solution without its symbiont, Rhizobium. EDB and TCE were both metabolized by the plant, as indicated by the formation of bromide ion from EDB and trichloroethanol from TCE. Each plant organ was independently capable of debromination of EDB. L. leucocephala is being used to treat perched groundwater as part of a remedial alternative to address an accidental EDB spill in Hawaii. Bromide levels of plant tissues from the trees grown in the phytoremediation treatment cells at the Hawaii Site were elevated, indicating uptake and degradation of brominated compounds in the trees. This report is the first evidence of a tropical tree effectively metabolizing these common organic pollutants.