Uptake and Transformation of Trichloroethylene by Hybrid Poplar: Laboratory Studies

Trichloroethylene (TCE) was widely used as an industrial solvent and degreasing agent for most of the twentieth century. It is now a widespread groundwater contaminant. Phytoremediation may be a cost-effective cleanup method for TCE-contaminated soils and groundwater. Studies of environmental TCE fate are complicated by its volatility. The literature reports both significant and insignificant plant uptake of TCE. Conflicting findings may be due to differences in exposure level, conditions, and duration of the studies, or to experimental artifacts from laboratory systems. This research quantified plant uptake and volatilization of TCE using a unique laboratory system. Hybrid poplar trees were exposed to 1 or 10 ppm TCE over a 43-d period. [14C]TCE was added to four high-flow, aerated, hydroponic plant growth chamber systems designed to provide high mass recoveries, an optimal plant environment and complete separation between foliar and root uptake. Transpiration stream concentration factors (TSCFs) for TCE, calculated from total [14C]TCE in shoot tissues plus phytovolatilized 14C, were 0.11 for two 1 ppm treatments and 0.15 for a 10 ppm treatment with roughly 25% attributed to phytovolatilization. Though extending study duration from 26 to 43 d resulted in accumulation of more mass of 14C in plant tissues, it had no effect on TSCF. These TSCF values are much lower than other published experimental values and values predicted by a theoretical relationship between TSCF and octanol-water partition coefficient. The TCE metabolites trichloroethanol (TCEt), trichloroacetic acid (TCAA), and dichloroacetic acid (DCAA)were identified in plant tissues of the 10-mg/L treatment. Hybrid poplar uptake ofTCAA and TCEt was quantified using a simpler aerated hydroponic system. TSCF values were calculated based on extractable parent compound in shoot tissues. TSCF for TCEt was \u3c 0.01. Presence of TCAA in hydroponic solution and in leaf and root tissues indicated transformation of TCEt to TCAA. TSCF for TCAA was \u3c 0.03 and decreased with increasing exposure concentration. TSCF also decreased under oxygen-limited root-zone conditions. Presence of DCAA in leaf and root tissues indicated transformation ofTCAA to DCAA. Transformation of parent compound, coupled with low extractability, may contribute to low TSCFs

Greenhouse Studies on Root Growth and Morphology

For studies of root growth and morphology, an ideal containerized plant culture system should provide: 1) adequate nutrients, water and oxygen; 2) appropriate mechanical impedance to root elongation; 3) adequate depth to prevent root binding; and 4) easy separation of roots from the root-zone substrate. Columnar containers are preferable to pots because they can support deep root growth while taking up less bench space. Many columns can be arranged within a small area, such as a gas-exchange chamber, thereby maximizing the number of treatments and replications in a given space. Standard potting substrates typically contain sphagnum peat mixed with perlite or vermiculite. These well-drained, organic-rich mixtures support an appropriate balance of water and oxygen while also providing exchange surfaces for plant nutrients. Separation of plant roots from the potting substrate, however, is impossible. We have developed a columnar plant culture system that supports healthy plant growth while also enabling complete separation of the roots from the growth substrate. Our substrate of choice is Turface®, a porous ceramic produced by baking clay at high temperatures (Figure 1). Turface® drains well, resists compaction, and retains nutrients well with a cation exchange capacity (CEC) of 33 meq/100 g. Our columns are constructed of 2” diameter PVC pipe. A bell-shaped reducer fitting secured to the bottom of the pipe stabilizes the column, and also holds in place a mesh screen. The mesh supports the Turface® substrate while also allowing water to drain by gravity. An automated watering system delivers a dilute nutrient solution to each column. The watering system is programmed to add small amounts of nutrient solution at the substrate surface 20 times per day. This high frequency keeps the tops of the columns moist and ensures delivery of nutrients throughout the column

Failure Analysis: Crop production on the Lunar surface

We have sought to optimize conditions for crop yield for many years, but optimal conditions will not always be cost effective. More importantly, environmental control systems routinely fail, and we need to learn how to gracefully recover from these failures. Failures of the power supply system are among the most common and most detrimental of all system failures. A battery back-up could supply a small amount of power during a power outage, but we need to know how to best utilize the back-up power. Early in this project, it became clear that the detrimental effects of a power loss could be mitigated by reducing temperature and adding low light. This was so effective that we began to investigate crop production using natural light on the lunar surface. This requires keeping plants alive and healthy during the 14.7 day-long interval on the dark side of the Moon

Failure Analysis Research Summary: Mitigating the Effects of Prolonged Darkness With Low Temperature and Low Light

Power loss is a common failure in controlled environments. The duration of power loss can be several days – and even weeks – in space environments. Long-duration power loss and the resulting darkness can cause plants to die unless remedial measures are taken during the power outage. Emergency back-up power from batteries could provide low light and reduced air temperature. Plant metabolism and growth are reduced in low temperature. As metabolism slows, energy requirements are reduced and less light is needed. The temperature should be maintained above the chilling temperature for the plant, which is species dependent. The addition of light will allow the plant to continue to expend energy on maintenance and some growth. Here we show that low light and cool temperatures can be used to maintain plants through the 14.7 days on the dark side of the Moon. Growth resumes immediately after the light is restored

Temporality, vulnerability, and energy justice in household low carbon innovations

Decarbonisation and innovation will change the affordability of different domestic energy services. This has the potential to alleviate vulnerability to fuel poverty, but it could create new injustices unless the risks are preempted and actively mitigated. In this paper, we ask: In what ways can emerging low-carbon innovations at the household scale complement, and complicate, achieving energy justice objectives? Drawing from four empirical case studies in the United Kingdom, the paper highlights different risks that come from different types of innovation required to tackle different decarbonisation challenges. More specifically, it assesses four particular household innovations—energy service contracts, electric vehicles, solar photovoltaic (PV) panels, and low carbon heating—selected for their fit with a typology of incremental vs. radical technology and modest vs. substantial changes in user practices. It shows how in each case, such innovations come with a collection of opportunities but also threats. In doing so, the paper seeks to unveil the “political economy” of low-carbon innovations, identifying particular tensions alongside who wins and who loses, as well as the scope and temporality of those consequences

Optimization of Soilless Media for Alkaline Irrigation Water

High root zone pH reduces nutrient availability and high alkalinity water is strongly buffered around an alkaline pH. Soilless media can be altered to improve nutrient availability. This study was conducted to optimize the composition of soilless media for use with high alkalinity water. Mixes of peat and/or perlite or vermiculite in 50/50 and 33/33/33 volumetric ratios were tested. In some studies, mixes were also amended with up to 2.4 g/L of dolomite limestone to neutralize the initial acidity of the peat. Mixes containing vermiculite settled more, had higher water holding capacity (WHC) and percent plant available water (%PAW), and similar air filled porosity (AFP), compared to mixes containing perlite. Dry mass was measured in corn, peas, tomatoes, and soybeans, and chlorophyll content was measured in corn. The addition of dolomite increased pH and decreased dry mass in corn, soybean, and tomato, but peas were unaffected. Chlorophyll content in corn also declined with increased amounts of dolomite. After a week of daily irrigation, pH 7.8 nutrient solution neutralized the acidity of the peat, without the need for addition of dolomite. Mixes containing vermiculite improved growth and chlorophyll concentration compared to mixes with perlite. The higher cation exchange capacity (CEC) of vermiculite-containing mixes may have improved nutrient availability. A soilless mix of only peat and vermiculite, in approximately equal volumes, resulted in the greatest growth and chlorophyll content when watered with high alkalinity nutrient solution