Biostimulation and Bioaugmentation to Enhance Reductive Dechlorination of TCE in a Long‐Term Flow Through Column Study

Large laboratory columns (15.2 cm diameter, 183 cm long) were fed with groundwater containing trichloroethylene (TCE), were biostimulated and bioaugmented, and were monitored for over 7.5 years. The objective of the study was to observe how the selection of the carbon and energy source, i.e., whey, Newman Zone^® standard surfactant emulsified oil and Newman Zone nonionic surfactant emulsified oil, affected the rate and extent of dechlorination. Column effluent was monitored for TCE and its degradation products, redox indicators (nitrate‐N, Fe(II), sulfate), and changes in iron mineralogy. Total bacteria and Dehalococcoides mccartyi strains were quantified using q‐PCR. Complete dechlorination was only observed in the whey treated columns, occurring 1 year after bioaugmentation with addition of a culture known to dechlorinate TCE to ethene, and 3 years later in the non‐bioaugmented column. The addition of the emulsified oils with or without bioaugmentation resulted in dechlorination only through cis‐DCE and vinyl chloride. While Dehalococcoides mccartyi strains are the only known bacteria that can fully dechlorinate TCE, their presence, either natural or augmented, was not the sole determiner of complete dechlorination. The establishment of a supporting microbial community and biogeochemistry that developed with continuous feeding of whey, in addition to the presence of D. mccartyi, were necessary to support complete reductive dechlorination. Results confirm that careful selection of a biostimulant is critical to the success of TCE dechlorination in complex soil environments.     

Holocene aridity and storm phases, Gulf and Atlantic coasts, USA

A bottomland flora that prevailed between 9900 and 6000 cal yr B.P. in a North Carolina stream valley may not reflect a regionally much wetter Atlantic climate, coeval with record drought in the Great Plains region and assumed dry Gulf coastal conditions. Such conditions were inferred for 6000 ± 1000 yr ago when the Bermuda High may have consistently occupied summer positions far to the NE. Arid episodes coeval with the Little River local wet interval are known from eolian sediments and pollen spectra in the Atlantic and the Gulf coastal plain. For multiple reasons, the regional extent, intensity, and duration of coastal aridity and alternating wet phases and the Bermuda High positions are not yet adequately constrained. The climate and edaphic causes for the steadily growing predominance of southern pines over hardwoods, achieved between 8900 and 4200 cal yr B.P. at different sites at different times are similarly still unresolved. New data from Shelby Lake, AL, reconfirms that no credible field or other proxy evidence exists for a previously postulated “catastrophic Gulf hurricane phase” in the late Holocene.     

Evaluation of a global ensemble flood prediction system in Peru

ABSTRACT

Flood early warning systems play a more substantial role in risk mitigation than ever before. Hydrological forecasts, which are an essential part of these systems, are used to trigger action against floods around the world. This research presents an evaluation framework, where the skills of the Global Flood Awareness System (GloFAS) are assessed in Peru for the years 2009–2015. Simulated GloFAS discharges are compared against observed ones for 10 river gauges. Forecasts skills are assessed from two perspectives: (i) by calculating verification scores at every river section against simulated discharges and (ii) by comparing the flood signals against reported events. On average, river sections with higher discharges and larger upstream areas perform better. Raw forecasts provide correct flood signals for 82% of the reported floods, but exhibit low verification scores. Post-processing of raw forecasts improves most verification scores, but reduces the percentage of the correctly forecasted reported events to 65%.     

An evaluation of various data pre-processing techniques with machine learning models for water level prediction

Natural Hazards - Floods are the most frequent type of natural disaster. It destroys wildlife habitat, damages bridges, railways, roads, properties, and puts millions of people at risk. As such,...     

Age of Tunica Hills (Louisiana-Mississippi) Quaternary fossiliferous creek deposits; Problems of radiocarbon dates and intermediate valley terraces in coastal plains

Among numerous stream-valley terrace deposits of the Gulf and Atlantic coastal plains that occupy chronologically and spatially intermediate positions between the youngest coastwise (coast-parallel) Pleistocene surface and the present, active floodplain, those of the Tunica Hills seem to provide by far the best opportunity for radiometric dating. Earlier views on the age of the Little Bayou Sara creek alluvium, represented by a single, 8 to 10-m-thick unit, ranged between the last interglaciation and middle Holocene. Reexamination of these deposits in the Little Bayou Sara and adjacent valleys clearly suggests their Late Pleistocene (apparently Farmdalian Interstade) age. The majority of the 14 available dates from the Little Bayou Sara and Tunica Bayou valleys proved to be too young, due to postdepositinal contamination. Dates ranging between 33,720 and 25,965 yr B.P. came from samples thought to be uncontaminated. Plant and faunal elements with boreal affinities in the unique fossil assemblage appear to be relicts of a preceding, full-glacial period, as regarded by Brown (1938). The absence of colder climate taxa from the Wilcox Bluff flora on Bayou Sara is insufficient evidence for a suggested Sangamon Interglacial age of the flora, and the terrace stratigraphy holds no proof for that view either. Only a single, loess-mantled, constructional, Quaternary, valley-terrace surface is present in the area. A narrow, low, actively developing floodplain terrace along Little Bayou Sara, cut into the Pleistocene alluvial unit, is primarily erosional in origin and has no bearing on the age of that unit. The age of the Tunica Hills terrace unit may provide comparison for dating intermediate valley-terrace deposits in favorable coastal settings elsewhere.