A remediation performance model for enhanced metabolic reductive dechlorination of chloroethenes in fractured clay till

A numerical model of metabolic reductive dechlorination is used to describe the performance of enhanced bioremediation in fractured clay till. The model is developed to simulate field observations of a full scale bioremediation scheme in a fractured clay till and thereby to assess remediation efficiency and timeframe. A relatively simple approach is used to link the fermentation of the electron donor soybean oil to the sequential dechlorination of trichloroethene (TCE) while considering redox conditions and the heterogeneous clay till system (clay till matrix, fractures and sand stringers). The model is tested on lab batch experiments and applied to describe sediment core samples from a TCE-contaminated site. Model simulations compare favorably to field observations and demonstrate that dechlorination may be limited to narrow bioactive zones in the clay matrix around fractures and sand stringers. Field scale simulations show that the injected donor is expected to be depleted after 5 years, and that without donor re-injection contaminant rebound will occur in the high permeability zones and the mass removal will stall at 18%. Long remediation timeframes, if dechlorination is limited to narrow bioactive zones, and the need for additional donor injections to maintain dechlorination activity may limit the efficiency of ERD in low-permeability media. Future work should address the dynamics of the bioactive zones, which is essential to understand for predictions of long term mass removal.     

Amazon dams and waterways: Brazil’s Tapajós Basin plans

Brazil plans to build 43 “large” dams (>30 MW) in the Tapajós Basin, ten of which are priorities for completion by 2022. Impacts include flooding indigenous lands and conservation units. The Tapajós River and two tributaries (the Juruena and Teles Pires Rivers) are also the focus of plans for waterways to transport soybeans from Mato Grosso to ports on the Amazon River. Dams would allow barges to pass rapids and waterfalls. The waterway plans require dams in a continuous chain, including the Chacorão Dam that would flood 18 700 ha of the Munduruku Indigenous Land. Protections in Brazil’s constitution and legislation and in international conventions are easily neutralized through application of “security suspensions,” as has already occurred during licensing of several dams currently under construction in the Tapajós Basin. Few are aware of “security suspensions,” resulting in little impetus to change these laws.     

Range contraction and loss of genetic variation of the Pyrenean endemic newt <Emphasis Type="Italic">Calotriton asper</Emphasis> due to climate change

Many studies have identified climate warming to be among the most important threats to biodiversity. Climate change is expected to have stronger effects on species with low genetic diversity, ectothermic physiology, small ranges, low effective populations sizes, specific habitat requirements and limited dispersal capabilities. Despite an ever-increasing number of studies reporting climate change-induced range shifts, few of these have incorporated species’ specific dispersal constraints into their models. Moreover, the impacts of climate change on genetic variation within populations and species have rarely been assessed, while this is a promising direction for future research. Here we explore the effects of climate change on the potential distribution and genetic variation of the endemic Pyrenean newt Calotriton asper over the period 2020–2080. We use species distribution modelling in combination with high-resolution gridded climate data while subsequently applying four different dispersal scenarios. We furthermore use published data on genetic variation of both mtDNA and AFLP loci to test whether populations with high genetic diversity (nucleotide diversity and expected heterozygosity) or evolutionary history (unique haplotypes and K clusters) have an increased extinction risk from climate change. The present study indicates that climate change drastically reduces the potential distribution range of C. asper and reveals dispersal possibilities to be minimal under the most realistic dispersal scenarios. Despite the major loss in suitable climate, the models highlight relatively large stable areas throughout the species core distribution area indicating persistence of populations over time. The results, however, show a major loss of genetic diversity and evolutionary history. This highlights the importance of accounting for intraspecific genetic variation in climate change impact studies. Likewise, the integration of species’ specific dispersal constraints into projections of species distribution models is an important step to fully explore the effects of climate change on species potential distributions.     

Development of a High Purity Filter for High Temperature Particulate Sampling and Analysis

This paper is directed to those interested in measuring trace metals in high-temperature particulate emissions. Particulate handsheet filters with satisfactory purity, efficiency, thermal stability, cost, strength (about 1 lb/in.), and flexibility for analysis of particulates in gases up to 800°C have been made with 99.2% Si0₂ Microquartzfibers. Almost all purity requirements for optimum atomic absorption and flame emission spectrophotometric analysis for trace metals have been achieved. The filters appear highly promising for X-ray fluorescence analysis but should be further evaluated. Suitability of the filters for neutron activation analysis is uncertain and should also be further evaluated. Dioctyl phthal-ate (DOP) aerosol efficiencies of 99 to 99.99% have been achieved by using fibers of various diameters. The filters are insensitive to humidity, insoluble In most acids and organic solvents. The handsheet filters have a slightly alkaline pH, but similar filters have been made on a papermaking machine with a pH of 6.4. Cost is estimated to be about $2.00/ft².     

Atmospheric Oxidation of Methyl Chloride Methylene Chloride,and Chloroform

Chlorinated atmospheric pollutants are presently receiving much attention because of expected chlorine-ozone interactions in the stratosphere.^1,2 The fully halogenated pollutants,such as CCI₃F, CCl₂F₂, and CCl₄, have no known removal processes that operate in the troposphere. These compounds are accumulating on a global scale, their atmospheric mixing ratios having reached about 2 X 10^-10 for CCl₂F₂,1.2 X 10^-10 for CCl₃F, and 9 X 10^-11 for CCl4.^3-5     

Sulfur Hexafluoride as a Surrogate for Monitoring Hazardous Waste Incinerator Performance

A viable chemical surrogate for monitoring the effectiveness of hazardous waste incinerators must include high thermal stability and low toxicity among its characteristics. The relationship between sulfur hexafluoride (SF₆) and hazardous constituent thermal stability for a mixture of chlorinated hydrocarbons indicates that SF6 has the potential to satisfy the basic requirements of a chemical surrogate for hazardous waste incineration.     

Air Levels and Mutagenicity of PM-10 in an Indoor Ice Arena

Abstract

Hazardous waste sites and industrial facilities contain area sources of fugitive emissions. Emission rate measurements or estimates are necessary for air pathway assessments for these sources. Emission rate data can be useful for the design of emission control and remediation strategies as well as for predictive modeling for population exposure assessments. This paper describes the use of a direct emission measurement approach – the enclosure approach using an emission isolation flux chamber – to measure emission rates of various volatile organic compounds (VOCs) from contaminated soil and water. A variety of flux chamber equipment designs and operating procedures have been employed by various researchers. This paper contains a review of the design and operational variables that affect the accuracy and precision of the method. Guidance is given as to the optimum flux chamber design and operating conditions for various types of emission sources. Also presented is a generic quality control program that gives the minimum number of duplicate, blank, background, and repeat samples that should be performed.     

Direct coupling of a genome-scale microbial in silico model and a groundwater reactive transport model

The activity of microorganisms often plays an important role in dynamic natural attenuation or engineered bioremediation of subsurface contaminants, such as chlorinated solvents, metals, and radionuclides. To evaluate and/or design bioremediated systems, quantitative reactive transport models are needed. State-of-the-art reactive transport models often ignore the microbial effects or simulate the microbial effects with static growth yield and constant reaction rate parameters over simulated conditions, while in reality microorganisms can dynamically modify their functionality (such as utilization of alternative respiratory pathways) in response to spatial and temporal variations in environmental conditions. Constraint-based genome-scale microbial in silico models, using genomic data and multiple-pathway reaction networks, have been shown to be able to simulate transient metabolism of some well studied microorganisms and identify growth rate, substrate uptake rates, and byproduct rates under different growth conditions. These rates can be identified and used to replace specific microbially-mediated reaction rates in a reactive transport model using local geochemical conditions as constraints. We previously demonstrated the potential utility of integrating a constraint-based microbial metabolism model with a reactive transport simulator as applied to bioremediation of uranium in groundwater. However, that work relied on an indirect coupling approach that was effective for initial demonstration but may not be extensible to more complex problems that are of significant interest (e.g., communities of microbial species and multiple constraining variables). Here, we extend that work by presenting and demonstrating a method of directly integrating a reactive transport model (FORTRAN code) with constraint-based in silico models solved with IBM ILOG CPLEX linear optimizer base system (C library). The models were integrated with BABEL, a language interoperability tool. The modeling system is designed in such a way that constraint-based models targeting different microorganisms or competing organism communities can be easily plugged into the system. Constraint-based modeling is very costly given the size of a genome-scale reaction network. To save computation time, a binary tree is traversed to examine the concentration and solution pool generated during the simulation in order to decide whether the constraint-based model should be called. We also show preliminary results from the integrated model including a comparison of the direct and indirect coupling approaches and evaluated the ability of the approach to simulate field experiment.     

Upstream Addicks–Barker reservoir damages during Hurricane Harvey: A case study of urban hydrology and policy failure in Houston,TX

Addicks and Barker reservoirs were built in the 1940s to protect downtown Houston from flooding and have generally worked very well until 2017 when Hurricane Harvey devastated much of Houston and surroundings with up to 40 inches (102 cm) of rainfall causing flooding of 154,000 homes in over 22 watersheds in Houston/Harris County alone. However, the story of how Addicks and Barker flooded upstream residential areas from a hydrologic standpoint is a harsh lesson in flood infrastructure policy and funding. This failure to protect both downstream properties in Buffalo Bayou and upstream areas behind the dams ended up with tens of thousands of flooded homes and properties, with many having flood waters for over 10 days. This paper explores the main causes for the flooding and addresses the hydrologic issues upstream in both reservoirs. The main causes of flooding were not just related to a massive rainfall event, but also explosive urban expansion of land use upstream of reservoirs, altered and updated reservoir design issues, and lack of governmental action in the years leading up to the disaster. Potential long-term solutions to the flooding and design problems are addressed in this article as well.