Arsenic and copper stabilisation in a contaminated soil by coal fly ash and green waste compost

In situ metal stabilisation by amendments has been demonstrated as an appealing low-cost remediation strategy for contaminated soil. This study investigated the short-term leaching behaviour and long-term stability of As and Cu in soil amended with coal fly ash and/or green waste compost. Locally abundant inorganic (limestone and bentonite) and carbonaceous (lignite) resources were also studied for comparison. Column leaching experiments revealed that coal fly ash outperformed limestone and bentonite amendments for As stabilisation. It also maintained the As stability under continuous leaching of acidic solution, which was potentially attributed to high-affinity adsorption, co-precipitation, and pozzolanic reaction of coal fly ash. However, Cu leaching in the column experiments could not be mitigated by any of these inorganic amendments, suggesting the need for co-addition of carbonaceous materials that provides strong chelation with oxygen-containing functional groups for Cu stabilisation. Green waste compost suppressed the Cu leaching more effectively than lignite due to the difference in chemical composition and dissolved organic matter. After 9-month soil incubation, coal fly ash was able to minimise the concentrations of As and Cu in the soil solution without the addition of carbonaceous materials. Nevertheless, leachability tests suggested that the provision of green waste compost and lignite augmented the simultaneous reduction of As and Cu leachability in a fairly aggressive leaching environment. These results highlight the importance of assessing stability and remobilisation of sequestered metals under varying environmental conditions for ensuring a plausible and enduring soil stabilisation.     

Evaluation of a Soil‐Based System to Dissipate Multiple Pesticides

Pesticide contaminated wastewater resulting from leftover mixes, equipment cleaning, and container disposal are problems related to pesticide use. This study reports on the effectiveness of a soil‐based bioreactor (SBBR) to dissipate pesticides of differing concentrations and mixtures. In order to accomplish this study, soil columns were used to simulate the SBBR. A mixture of five herbicides and two insecticides from seven different chemical families (atrazine, dicamba, fluometuron, metolachlor, sulfentrazone, chlopyrifus, and λ‐cyhalothrin) were added to the SBBR‐simulated system as formulated products in three concentrations each: 0 part per million (control), 10 ppm, and 100 ppm. Additionally a 1,000 ppm treatment was added that included just the five herbicides to investigate how the system would respond to heavy loading. The system was run for 90 days with samples taken at day 4 (just prior to loading the columns), then at 30, 60, and 90 days. At low pesticide concentrations (10 and 100 ppm), there was significant dissipation (p < 0.05) of all pesticides in the columns except sulfentrazone. At 1,000 ppm, fluometuron, in addition to sulfentrazone, did not show significant dissipation. Overall, the system performed as expected and could be considered practical for use on farms or nurseries. ©2015 Wiley Periodicals, Inc.     

A case study characterizing animal fecal sources in surface water using a mitochondrial DNA marker

Water quality impairment by fecal waste in coastal watersheds is a public health issue. The present study provided evidence for the use of a mitochondrial (mtDNA) marker to detect animal fecal sources in surface water. The accurate identification of fecal pollution is based on the notion that fecal microorganisms preferentially inhabit a host animal’s gut environment. In contrast, mtDNA host-specific markers are inherent to eukaryotic host cells, which offers the advantage by detecting DNA from the host rather than its fecal bacteria. The present study focused on sampling water presumably from non-point sources (NPS), which can increase bacterial and nitrogen concentrations to receiving water bodies. Stream sampling sites located within the Piscataqua River Watershed (PRW), New Hampshire, USA, were sampled from a range of sites that experienced nitrogen inputs such as sewer and septic systems and suburban runoff. Three mitochondrial (mtDNA) gene marker assays (human, bovine, and canine) were tested from surface water. Nineteen sites were sampled during an 18-month period. Analyses of the combined single and multiplex assay results showed that the proportion of occurrence was highest for bovine (15.6%; n = 77) compared to canine (5.6%; n = 70) and human (5.7%; n = 107) mtDNA gene markers. For the human mtDNA marker, there was a statistically significant relationship between presence vs. absence and land use (Fisher’s test p = 0.0031). This result was evident particularly for rural suburban septic, which showed the highest proportion of presence (19.2%) compared to the urban sewered (3.3%), suburban sewered (0%), and agricultural (0%) as well as forested septic (0%) sites. Although further testing across varied land use is needed, our study provides evidence for using the mtDNA marker in large watersheds.     

Song-type sharing in song sparrows: implications for repertoire function and song learning

One hypothesis for the function of song repertoires is that males learn multiple song types so that they may share songs with neighbors, allowing them to match during territorial interactions. In at least one song sparrow population, in Washington, territorial males share a high proportion of song types with their neighbors and use these shared songs in matching. We recorded song sparrows in Pennsylvania and quantified sharing of whole songs and song segments. We found that song sharing is an order of magnitude less common in the Pennsylvania population. We found sharing of song segments to be significantly more common than the sharing of whole songs in three of the five fields we examined, while we found no significant differences between whole and partial song sharing in the remaining two fields. Finally, we found no evidence that sharing is greater between birds in the same field compared to birds in different fields. Taken with the data from Washington song sparrows, these results provide evidence for intraspecific geographic variation in the organization of song repertoires, and suggest that song sharing has not been a strong selective force in the evolution of song repertoires in song sparrows as a species. Furthermore, Washington and Pennsylvania song sparrows differ in how they learn song, in that Washington birds copy whole songs, while Pennsylvania birds appear to copy and recombine song segments, as has been found in laboratory studies of song learning. Thus both song learning and the function of song repertoires differ between populations of song sparrows. Such intraspecific geographic variation offers a unique opportunity to explore the ecological and historical factors which have influenced the evolution of song. Received: 30 June 1997 / Accepted after revision: 8 March 1998     

Immobilization of mercury by pyrite (FeS2)

Elemental mercury (Hg⁰) is a metal with a number of atypical properties, which has resulted in its use in myriad anthropogenic processes. However, these same properties have also led to severe local subsurface contamination at many places where it has been used. As such, we studied the influence of various parameters on Hg(II) sorption onto pyrite (pH, time, Hg(II) concentration), a potential subsurface reactive barrier. Batch sorption studies revealed that total Hg(II) removal increases with both pH and time. X-ray absorption spectroscopy analysis showed that a transformation in the coordination environment at low pH occurred during aging over 2 weeks, to form an ordered monolayer of monodentate Hg-Cl complexes on pyrite. In column studies packed with pure quartz sand, the transport of Hg(II) was significantly retarded by the presence of a thin pyrite-sand reactive barrier, although dissolved oxygen inhibited Hg(II) sorption onto pyrite in the column.     

Effect of in situ soil amendments on arsenic uptake in successive harvests of ryegrass (Lolium perenne cv Elka) grown in amended As-polluted soils

Several iron-bearing additives, selected for their potential ability to adsorb anions, were evaluated for their effectiveness in attenuation of arsenic (As) in three soils with different sources of contamination. Amendments used were lime, goethite (alpha-FeOOH) (crystallised iron oxide) and three iron-bearing additives, iron grit, Fe(II) and Fe(III) sulphates plus lime, applied at 1% w/w. Sequential extraction schemes conducted on amended soils determined As, Cu, Zn and Ni fractionation. Plant growth trials using perennial ryegrass (Lolium perenne var. Elka) assessed shoot As uptake. This was grown in the contaminated soils for 4 months, during which time grass shoots were successively harvested every 3 weeks. Goethite increased biomass yields, but clear differences were observed in As transfer rates with the various iron oxides. In conclusion, whilst Fe-oxides may be effective in situ amendments, reducing As bioavailability, their effects on plant growth require careful consideration. Soil-plant transfer of As was not completely halted by any amendment.     

Generation and characterization of diesel exhaust in a facility for controlled human exposures

An idling medium-duty diesel truck operated on ultralow sulfur diesel fuel was used as an emission source to generate diesel exhaust for controlled human exposure. Repeat tests were conducted on the Federal Test Procedure using a chassis dynamometer to demonstrate the reproducibility of this vehicle as a source of diesel emissions. Exhaust was supplied to a specially constructed exposure chamber at a target concentration of 100 microg x m(-3) diesel particulate matter (DPM). Spatial variability within the chamber was negligible, whereas emission concentrations were stable, reproducible, and similar to concentrations observed on the dynamometer. Measurements of nitric oxide, nitrogen dioxide, carbon monoxide, particulate matter (PM), elemental and organic carbon, carbonyls, trace elements, and polycyclic aromatic hydrocarbons were made during exposures of both healthy and asthmatic volunteers to DPM and control conditions. The effect of the so-called "personal cloud" on total PM mass concentrations was also observed and accounted for. Conventional lung function tests in 11 volunteer subjects (7 stable asthmatic) did not demonstrate a significant change after 2-hr exposures to diesel exhaust. In summary, we demonstrated that this facility can be effectively and safely used to evaluate acute responses to diesel exhaust exposure in human volunteers.     

Real-world in-use activity, fuel use, and emissions for nonroad construction vehicles: a case study for excavators

A study design was developed and demonstrated for deployment of a portable emission measurement system (PEMS) for excavators. Excavators are among the most commonly used vehicles in construction activities. The PEMS measured nitric oxide, carbon monoxide, hydrocarbons, carbon dioxide, and opacity-based particulate matter. Data collection, screening, processing, and analysis protocols were developed to assure data quality and to quantify variability in vehicle fuel consumption and emissions rates. The development of data collection procedures was based on securing the PEMS while avoiding disruption to normal vehicle operations. As a result of quality assurance, approximately 90% of the attempted measurements resulted in valid data. On the basis of field data collected for three excavators, an average of 50% of the total nitric oxide emissions was associated with 29% of the time of operation, during which the average engine speed and manifold absolute pressure were significantly higher than corresponding averages for all data. Mass per time emission rates during non-idle modes (i.e., moving and using bucket) were on average 7 times greater than for the idle mode. Differences in normalized average rates were influenced more by intercycle differences than intervehicle differences. This study demonstrates the importance of accounting for intercycle variability in real-world in-use emissions to develop more accurate emission inventories. The data collection and analysis methodology demonstrated here is recommended for application to more vehicles to better characterize real-world vehicle activity, fuel use, and emissions for nonroad construction equipment.     

Characterization of real-world activity, fuel use, and emissions for selected motor graders fueled with petroleum diesel and B20 biodiesel

Motor graders are a common type of nonroad vehicle used in many road construction and maintenance applications. In-use activity, fuel use, and emissions were measured for six selected motor graders using a portable emission measurement system. Each motor grader was tested with petroleum diesel and B20 biodiesel. Duty cycles were quantified in terms of the empirical cumulative distribution function of manifold absolute pressure (MAP), which is an indicator of engine load. The motor graders were operated under normal duty cycles for road maintenance and repair at various locations in Wake and Nash Counties in North Carolina. Approximately 3 hr of quality-assured, second-by-second data were obtained during each test. An empirical modal-based model of vehicle fuel use and emissions was developed, based on stratifying the data with respect to ranges of normalized MAP, to enable comparisons between duty cycles, motor graders, and fuels. Time-based emission factors were found to increase monotonically with MAP. Fuel-based emission factors were mainly sensitive to differences between idle and non-idle engine operation. Cycle average emission factors were estimated for road "resurfacing," "roading," and "shouldering" activities. On average, the use of B20 instead of petroleum diesel leads to a negligible decrease of 1.6% in nitric oxide emission rate, and decreases of 19-22% in emission rates of carbon monoxide, hydrocarbons, and particulate matter. Emission rates decrease significantly when comparing newer engine tier vehicles to older ones. Significant reductions in tailpipe emissions accrue especially from the use of B20 and adoption of newer vehicles.