Effect of soil sterilization by mercuric chloride on herbicide sorption by soil

Microbial inhibitors such as mercuric chloride are frequently used to sterilize soil or soil-water slurries in experimental studies on the fate of xenobiotics in the environment. This study examined the influence of mercuric chloride additions to soil-water slurries on the sorptive behaviour of a phenoxy herbicide (2,4-D) in soil. The results demonstrated that mercuric chloride strongly decreased the capacity of the soil to retain herbicides, and that the interference of mercuric chloride with herbicide sorption increased with increasing soil organic carbon contents. Because of the competitive sorption between mercuric chloride and the phenoxy herbicide, we conclude that mercuric chloride may not be a good soil sterilization procedure for use in xenobiotic fate studies.     

Physical versus chemical effects on bacterial and bromide transport as determined from on site sediment column pulse experiments

Twenty-eight bacterial and Br transport experiments were performed in the field to determine the effects of physical and chemical heterogeneity of the aquifer sediment. The experiments were performed using groundwater from two field locations to examine the effects of groundwater chemistry on transport. Groundwater was extracted from multilevel samplers and pumped through 7-cm-long columns of intact sediment or repacked sieved and coated or uncoated sediment from the underlying aquifer. Two bacterial strains, Comamonas sp. DA001 and Paenibacillus polymyxa FER-02, were injected along with Br into the influent end of columns to examine the effect of cell morphology and cell surface properties on bacterial transport. The effects of column sediment grain size and mineral coatings coupled with groundwater geochemistry were also investigated. Significant irreversible attachment of DA001 was observed in the Fe oxyhydroxide-coated columns, but only in the suboxic groundwater where the concentrations of dissolved organic carbon (DOC) were ca. 1 ppm. In the oxic groundwater where DOC was ca. 8 ppm, little attachment of DA001 to the Fe oxyhydroxide-coated columns was observed. This indicates that DOC can significantly reduce bacterial attachment due electrostatic interactions. The larger and more negatively charged FER-02 displayed increasing attachment with decreasing grain size regardless of DOC concentration, and modeling of FER-02 attachment revealed that the presence of Fe and Al coatings on the sediment also promoted attachment. Finally, the presence of Al coatings and Al containing minerals appeared to significantly retard the Br tracer regardless of the concentration of DOC. These findings suggest that DOC in shallow oxic groundwater aquifers can significantly enhance the transport of bacteria by reducing attachment to Fe, Mn and Al oxyhydroxides. This effect appears to be profound for weakly and strongly charged hydrophilic bacteria and may contribute to differences in observations between laboratory experiments versus field-scale investigations particularly if the groundwater pH remains subneutral and Fe oxyhydroxide phases exist. These observation validate the novel approach taken in the experiments outlined here of performing laboratory-scale experiments on site to facilitate the use of fresh groundwater and thus be more representative of in situ groundwater conditions.     

Hydrodynamic and ecological assessment of nearshore restoration: A modeling study

Along the Pacific Northwest coast, much of the estuarine habitat has been lost over the last century to agricultural land use, residential and commercial development, and transportation corridors. As a result, many of the ecological processes and functions have been disrupted. To protect and improve these coastal habitats that are vital to aquatic species, many projects are currently underway to restore estuarine and coastal ecosystems through dike breaches, setbacks, and removals. Understanding site-specific information on physical processes is critical for improving the success of such restoration actions. In this study, a three-dimensional hydrodynamic model was developed to simulate estuarine processes in the Stillaguamish River estuary, where restoration of a 160-acre parcel through dike setback has been proposed. The model was calibrated to observed tide, current, and salinity data for existing conditions and applied to simulate the hydrodynamic responses to two restoration alternatives. Model results were then combined with biophysical data to predict habitat responses within the restoration footprint. Results showed that the proposed dike removal would result in desired tidal flushing and conditions that would support four habitat types on the restoration footprint. At the estuary scale, restoration would substantially increase the proportion of area flushed with freshwater (<5 ppt) at flood tide. Potential implications of predicted changes in salinity and flow dynamics are discussed relative to the distribution of tidal marsh habitat.     

Linking satellite and field survey data,through the use of gis,as implemented in Great Britain in the Countryside Survey 1990 project

The Institute of Terrestrial Ecology (ITE) has been studying land use and the effects of land use on ecology for two decades. A series of national field surveys have been undertaken by the Land Use Section of ITE since 1978, the most recent being Countryside Survey 1990 (CS1990). The three-year project brought together field survey and remote sensing data which were analyzed using Geographical Information Systems (GIS). National and regional land-cover patterns were described and changes estimated.The data collected by the field survey part of CS1990 recorded stratified samples based on a land classification. Thematic maps for surveyed 1-km squares covered physiography, agriculture and semi-natural vegetation, forestry, structures and boundaries. The same sites were surveyed in 1984 and 1990 with 14 000 digital maps produced describing both years. GIS was used to generate stock figures for each year, and overlay allowed change between survey dates to be estimated.GIS was used to compare data collected from both field survey and satellite imagery so that both sets of information could be qualified when expressed as national figures.This paper describes the historical development of the ITE Land Classification, examines the way in which data were collected for surveys, with particular reference to Countryside Survey 1990, and shows how satellite and field survey data can be linked through GIS.     

Setting conservation priorities for migratory networks under uncertainty

Conserving migratory species requires protecting connected habitat along the pathways they travel. Despite recent improvements in tracking animal movements, migratory connectivity remains poorly resolved at a population level for the vast majority of species, thus conservation prioritization is hampered. To address this data limitation, we developed a novel approach to spatial prioritization based on a model of potential connectivity derived from empirical data on species abundance and distance traveled between sites during migration. We applied the approach to migratory shorebirds of the East Asian‐Australasian Flyway. Conservation strategies that prioritized sites based on connectivity and abundance metrics together maintained larger populations of birds than strategies that prioritized sites based only on abundance metrics. The conservation value of a site therefore depended on both its capacity to support migratory animals and its position within the migratory pathway; the loss of crucial sites led to partial or total population collapse. We suggest that conservation approaches that prioritize sites supporting large populations of migrants should, where possible, also include data on the spatial arrangement of sites.     

Production, Purification and Activity of an Extracellular Depolymerase from Aspergillus fumigatus

A strain of Aspergillus fumigatus, which was observed to rapidly degrade poly-3-hydroxybutyrate (PHB) in a leaf compost, was found to secrete an extracellular hydrolase when grown on PHB as the sole carbon source. Isolation and characterization of the PHB hydrolase (depolymerase) from this fungus revealed that the enzyme had a molecular weight of 57 kDa, an isoelectric point of 7.2, and a PHB hydrolysis activity maxima which occurred at 70°C and pH 8.0. Affinity labeling experiments suggested that this fungal hydrolase is a type of serine esterase. The cyclic trimers of 3-hydroxybutyrate were found to reversibly inhibit the enzymes.     

Electrolytic oxidation studies of 2,2′-dichlorobiphenyl using ruthenium oxide electrodes, persulfate oxidizers, and UV irradiation

A three probe potentiostat was used to control the potential to a catalytic ruthenium oxide anode in oxidation studies of 2,2′-dichlorobiphenyl (2,2′). Voltages applied varied in one volt increments from 2.0 to 4.0 volts. Studies involved determination of the optimum voltage operating in conjunction with added sodium persulfate oxidizers (0.002 M and 0.018 M) and various exposure times (1 and 8 h) to ultra-violet (254.7 nm) provided by a General Electric BH-6 high pressure mercury arc lamp. The oxidation products of 2,2′ consisted of four compounds. The primary product was 2-chloro, 2′-hydroxyl biphenyl. Other products included: 2-acetoxy, 2′chlorobiphenyl (as previously observed by Laule et al, Journal of Electroanalytical Chemistry, 213: 329–332 (1986)), and dibenzofuran and 5,5′ dichlorodibenzofuran. All products were confirmed using a combination of GC and GC/MS. No reduction in 2,2′ concentration was observed in any of the control solutions in the absence of an applied voltage. Additionally, the presence of an oxidizer and UV irradiation aided the oxidation of 2,2′-dichlorobiphenyl. The oxidation percentage of the 2,2′ at 5 ppm was in the range of 70% under the optimum conditions of applied potential (3.0 volts), persulfate concentration (0.018 M), and UV exposure time (8 h). All reaction conditions and analysis procedures are described.     

Degradation of poly(β-hydroxyalkanoates) and polyolefin blends in a municipal wastewater treatment facility

Six types of plastics and plastic blends, the latter composed at least partially of biodegradable material, were exposed to aerobically treated wastewater (activated sludge) to ascertain their biodegradability. In one study, duplicate samples of 6% starch in polypropylene, 12% starch in linear low-density polyethylene, 30% polycaprolactone in linear low-density polyethylene, and poly(-hydroxybutyrate-co-hydroxyvalerate) (PHB/V), a microbially produced polyester, were exposed to activated sludge for 5 months, and changes in mass, molecular weight average, and tensile properties were measured. None of the blended material showed any sign of degradation. PHB/V, however, showed a considerable loss of mass and a significant loss of tensile strength. In a second study, PHB/V degraded rapidly, but another type of microbial polymer which forms a thermoplastic elastomer, poly(-hydroxyoctanoate), did not degrade. These results illustrate the potential for disposal and degradation of PHB/V in municipal wastewater.     

Development and validation of the volatile correction model for PM10 – An empirical method for adjusting TEOM measurements for their loss of volatile particulate matter

EU Directives stipulate that PM₁₀ should be measured using the gravimetric reference method as laid out in EN12341 [CEN, 1998. Air Quality – Determination of the PM₁₀ Fraction of Suspended Particulate Matter – Reference Method and Field Test Procedure to Demonstrate Reference Equivalence of Measurement Methods. European Committee for Standardisation], or an equivalent method as demonstrated using EC guidance [EC, 2005. Demonstration of Equivalence of Ambient Air Monitoring Methods. European Commission Working Group on Guidance for the Demonstration of Equivalence]. There is however a conflict between the requirement to measure PM₁₀ using the gravimetric reference method and the need for rapid public reporting, and many member states, including the UK, rely on non-gravimetric techniques to measure PM₁₀. In the UK the majority of PM₁₀ measurements are made using the Tapered Element Oscillating Microbalance (TEOM), which does not meet the equivalence criteria [Harrison, D., 2006. UK Equivalence Programme for Monitoring of Particulate Matter. Defra, London]. The implied need to upgrade or replace TEOMs with an equivalent automated measurement technique has significant cost implications. The model described in this paper was based on analysis of daily mean measurements of PM₁₀ by the Filter Dynamics Measurement System (FDMS) and the TEOM at UK sites. It uses the FDMS measurement of the volatile component of PM₁₀ (referred to here as FDMS purge) to correct for differences in the sensitivity to volatile PM₁₀ between the TEOM and the EU gravimetric reference method. The model equation for the correction of TEOM PM₁₀ measurements is: TEOM_VCM = TEOM ? 1.87 FDMS purge due to the regional homogeneity of volatile PM, the FDMS purge concentration may be measured at a site distant to the TEOM, allowing the possibility of using a single FDMS instrument to correct PM₁₀ measurements made by several TEOMs in a defined geographical area. The model was assessed against the criteria for the EC Working Group's Guidance for the Demonstration of Equivalence of Ambient Air Monitoring Methods [EC, 2005. Demonstration of Equivalence of Ambient Air Monitoring Methods. European Commission Working Group on Guidance for the Demonstration of Equivalence]. The model satisfies the equivalence criteria using remote FDMS purge measurements for distances up to 200 km (in 22 out of 23 data sets). These data provide strong evidence that the model is a viable tool for correcting measurements from TEOM instruments on the national and local government networks.     

Global protected-area coverage and human pressure on tidal flats

Tidal flats are a globally distributed coastal ecosystem important for supporting biodiversity and ecosystem services. Local to continental-scale studies have documented rapid loss of tidal habitat driven by human impacts, but assessments of progress in their conservation are lacking. With an internally consistent estimate of distribution and change, based on Landsat satellite imagery, now available for the world's tidal flats, we examined tidal flat representation in protected areas (PAs) and human pressure on tidal flats. We determined tidal flat representation and its net change in PAs by spatially overlaying tidal flat maps with the World Database of Protected Areas. Similarly, we overlaid the most recent distribution map of tidal flats (2014–2016) with the human modification map (HM_c) (range from 0, no human pressure, to 1, very high human pressure) to estimate the human pressure exerted on this ecosystem. Sixty-eight percent of the current extent of tidal flats is subject to moderate to very high human pressure (HM_c > 0.1), but 31% of tidal flat extent occurred in PAs, far exceeding PA coverage of the marine (6%) and terrestrial (13%) realms. Net change of tidal flat extent inside PAs was similar to tidal flat net change outside PAs from 1999 to 2016. Substantial shortfalls in protection of tidal flats occurred across Asia, where large intertidal extents coincided with high to very high human pressure (HM_c > 0.4–1.0) and net tidal flat losses up to 86.4 km² (95% CI 83.9–89.0) occurred inside individual PAs in the study period. Taken together, our results show substantial progress in PA designation for tidal flats globally, but that PA status alone does not prevent all habitat loss. Safeguarding the world's tidal flats will thus require deeper understanding of the factors that govern their dynamics and effective policy that promotes holistic coastal and catchment management strategies.