Thallium uptake/tolerance in a model (hyper)accumulating plant: Effect of extreme contaminant loads

Thallium (Tl) is a toxic trace element with a highly negative effect on the environment. For phytoextraction purposes, it is important to know the limitations of plant growth. In this study, we conducted experiments with a model Tl-hyperaccumulating plant (Sinapis alba L., white mustard) to better understand the plant tolerance and/or associated detoxification mechanisms under extreme Tl doses (accumulative 0.7/1.4 mg Tl, in total). Both the hydroponic/semi-hydroponic (artificial soil) cultivation variants were studied in detail. The Tl bioaccumulation potential for the tested plant reached up to 1% of the total supplied Tl amount. Furthermore, it was revealed that the plants grown in the soil-like system did not tolerate Tl concentrations in nutrient solutions higher than ~1 mg/L, i.e., wilting symptoms were evident. Surprisingly, for the plants grown in hydroponic solutions, the tolerable Tl concentration was by contrast at least 2-times higher (≥ 2 mg Tl/L), presumably mimicking the K biochemistry. The obtained hydroponic/semi-hydroponic phytoextraction data can serve, in combination, as a model for plant-assisted remediation of soils or mining/processing wastes enriched in Tl, or possibly for environmental cycling of Tl in general.

Organochlorine and Metal Contaminants in the Blood Plasma of Green Sturgeon Caught in Washington Coastal Estuaries

Non-invasive monitoring was used to evaluate the concentrations of forty contaminants in the blood plasma of the North American Green Sturgeon Acipenser medirostris caught and released from three estuaries in Washington State. The highest contaminant loads were found in fish caught in the most urbanized sites. Few statistical differences were found when evaluating contaminant levels according to sex, maturation stage, or distinct population segments of Green Sturgeon. The results indicate that recent exposure to legacy contaminants was reflected in Green Sturgeon plasma. Aldrin, 4,4-DDE, a-BHC, copper, and selenium were the most frequently detected contaminants. This study also explored the challenges of assessing toxicity in threatened species using non-lethal approaches. There is currently a lack of environmental contaminant monitoring data in estuaries frequented by Green Sturgeon and limited plasma to tissue toxicity correlations.

Mitigating Source Water Risks with Improved Wildfire Containment

In many fire-prone watersheds, wildfire threatens surface drinking water sources with eroded contaminants. We evaluated the potential to mitigate the risk of degraded water quality by limiting fire sizes and contaminant loads with a containment network of manager-developed Potential fire Operational Delineations (PODs) using wildfire risk transmission methods to partition the effects of stochastically simulated wildfires to within and out of POD burning. We assessed water impacts with two metrics—total sediment load and frequency of exceeding turbidity limits for treatment—using a linked fire-erosion-sediment transport model. We found that improved fire containment could reduce wildfire risk to the water source by 13.0 to 55.3% depending on impact measure and post-fire rainfall. Containment based on PODs had greater potential in our study system to reduce total sediment load than it did to avoid degraded water quality. After containment, most turbidity exceedances originated from less than 20% of the PODs, suggesting strategic investments to further compartmentalize these areas could improve the effectiveness of the containment network. Similarly, risk transmission varied across the POD boundaries, indicating that efforts to increase containment probability with fuels reduction would have a disproportionate effect if prioritized along high transmission boundaries.