Application of a combined measurement and modeling method to quantify windblown dust emissions from the exposed playa at Mono Lake, California

Particulate matter < or =10 microm (PM10) emissions due to wind erosion can vary dramatically with changing surface conditions. Crust formation, mechanical disturbance, soil texture, moisture, and chemical content of the soil can affect the amount of dust emitted during a wind event. A refined method of quantifying windblown dust emissions was applied at Mono Lake, CA, to account for changing surface conditions. This method used a combination of real-time sand flux monitoring, ambient PM10 monitoring, and dispersion modeling to estimate dust emissions and their downwind impact. The method identified periods with high emissions and periods when the surface was stable (no sand flux), even though winds may have been high. A network of 25 Cox sand catchers (CSCs) was used to measure the mass of saltating particles to estimate sand flux rates across a 2-km2 area. Two electronic sensors (Sensits) were used to time-resolve the CSC sand mass to estimate hourly sand flux rates, and a perimeter tapered element oscillating microbalance (TEOM) monitor measured hourly PM10 concentrations. Hourly sand flux rates were related by dispersion modeling to hourly PM10 concentrations to back-calculate the ratio of vertical PM10 flux to horizontal sand flux (K-factors). Geometric mean K-factor values (K(f)) were found to change seasonally, ranging from 1.3 x 10(-5) to 5.1 x 10(-5) for sand flux measured at 15 cm above the surface (q15). Hourly PM10 emissions, F, were calculated by applying seasonal K-factors to sand flux measurements (F = K(f) x q15). The maximum hourly PM10 emission rate from the study area was 76 g/m2 x hr (10-m wind speed = 23.5 m/sec). Maximum daily PM10 emissions were estimated at 450 g/m2 x day, and annual emissions at 1095 g/m2 x yr. Hourly PM10 emissions were used by the U.S. Environmental Protection Agency (EPA) guideline AERMOD dispersion model to estimate downwind ambient impacts. Model predictions compared well with monitor concentrations, with hourly PM10 ranging from 16 to over 60,000 microg/m3 (slope = 0.89, R2 = 0.77).     

Correlation of low-volatile organic chlorine (LVOCl) and PCDD/Fs in various municipal waste incinerators (MWIs)

Medium- and low-volatile organic chlorine (M/LVOCl) and PCDD/Fs in flue gas from various municipal waste incinerators (MWIs) were monitored. The sample for M/LVOCl was collected in an adsorption tube which was thermally desorbed and the amount of chlorine was measured by atomic emission spectrometry (AES) detection using radiofrequency helium plasma. The helium plasma excited chlorine having an optical emission line of 837.6 nm was monitored. The MVOCl and LVOCl were organic chlorine groups whose boiling points (bp) ranged from 70-120 degrees C and 170-270 degrees C, respectively. The compounds having bp 120-170 degrees C were distributed in two tubes. LVOCl correlated well with PCDD/Fs (ng/Nm3, r=0.81) in a wide range of 0.01-100 ng/Nm3 of PCDD/Fs, while the correlation of LVOCl vs. TEQ was less related (r=0.69). These results agreed with the fact that LVOCl monitored the amount of organic chlorine without molecular structure information, which is critical to toxicity. Since the bp of LVOCl was not identical with that of PCDD/Fs, the regression was effected by the conditions of the gas treatment devices. Because most data of 2001 were collected just after the installation of PCDD/Fs in MWIs, the regression of 2001 was slightly different from that of 2002-2003. Eliminating these initial unsteady data, the regression of LVOCl vs. PCDD/Fs became better, giving r= 0.86. Besides having PCDD/Fs as surrogates, M/LVOCl is valuable as a versatile element-selective organic chlorine monitor to improve thermal process control.     

Glycosylation of bisphenol A by freshwater microalgae

The endocrine disruptor bisphenol A (BPA, 4,4'-isopropylidenediphenol) is used to manufacture polycarbonate plastic and epoxy resin linings of food and beverage cans, and the residues from these products are then sometimes discharged into rivers and lakes in waste leachates. However, the fate of BPA in the environment has not yet been thoroughly elucidated. Considering the effect of BPA on aquatic organisms, it is important that we estimate the concentration of BPA and its metabolites in the aquatic environment, but there are few data on the metabolites of BPA. Here, we focused on freshwater microalgae as organisms that contribute to the biodegradation or biotransformation of BPA in aquatic environments. When we added BPA to cultures of eight species of freshwater microalgae, a reduction in the concentration of BPA in the culture medium was observed in all cultures. BPA was metabolized to BPA glycosides by Pseudokirchneriella subcapitata, Scenedesmus acutus, Scenedesmus quadricauda, and Coelastrum reticulatum, and these metabolites were then released into the culture medium. The metabolite from P. subcapitata, S. acutus, and C. reticulatum was identified by FAB-MS and (1)H-NMR as bisphenol A-mono-O-beta-d-glucopyranoside (BPAGlc), and another metabolite, from S. quadricauda, was identified as bisphenol A-mono-O-beta-d-galactopyranoside (BPAGal). These results demonstrate that freshwater microalgae that inhabit universal environments can metabolize BPA to its glycosides. Because BPA glycosides accumulate in plants and algae, and may be digested to BPA by beta-glycosidase in animal intestines, more attention should be given to levels of BPA glycosides in the environment to estimate the ecological impact of discharged BPA.     

Leaching characteristics of stabilized/solidified fly ash generated from ash-melting plant

This study was designed to elucidate the leaching characteristics of stabilized/solidified (S/S) fly ash generated by ash-melting. For this study, pH-dependent leaching tests, sequential extraction procedures, and column leaching tests were carried out. The pH-dependent leaching test results for Pb, Cu, and Zn showed that the heavy metal concentrations in the high-pH range were lower than the predicted values for hydroxide and carbonate. During sequential extraction, Cu and Pb were principally distributed in the S/S ashes' organic matter fraction in the chelating agent, suggesting that metals bind to the chelating agent. The percentage of the water-soluble fraction for Pb and Cu was low (<0.2 %). The fly ashes treated with a chelating agent and cement had low leachability potential for metals in the high-pH range. Column tests for S/S fly ashes showed that two leaching stages were distinguishable: one for short time, corresponding to faster metal leaching, and another for the leaching rate. Kinetic speciation was then applied to data obtained from column leaching tests. The first-order reaction/diffusion model showed a better fit for Ca, Pb, and Cu, suggesting that the initial dissolution of soluble compounds, such as metal chloride, was controlled by the first-order reaction (surface wash off). Subsequently, insoluble compounds such as hydroxide or carbonate might penetrate into the porous matrix by diffusion.     

Investigation of 1,4-dioxane originating from incineration residues produced by incineration of municipal solid waste

As a groundwater contaminant, 1,4-dioxane is of considerable concern because of its toxicity, refractory nature to degradation, and rapid migration within an aquifer. Although landfill leachate has been reported to contain significant levels of 1,4-dioxane, the origin of 1,4-dioxane in leachate has not been clarified until now. In this study, the origins of 1,4-dioxane in landfill leachate were investigated at 38 landfill sites and three incineration plants in Japan. Extremely high levels of 1,4-dioxane 89 and 340 microg l(-1), were detected in leachate from two of the landfill sites sampled. Assessments of leachate and measurement of 1,4-dioxane in incineration residues revealed the most likely source of 1,4-dioxane in the leachate to be the fly ash produced by municipal solid waste incinerators. Effective removal of 1,4-dioxane in leachate from fly ash was achieved using heating dechlorination systems. Rapid leaching of 1,4-dioxane observed from fly ash in a sequential batch extraction indicated that the incorporation of a waste washing process could also be effective for the removal of 1,4-dioxane in fly ash.     

Occurrence of phenols in leachates from municipal solid waste landfill sites in Japan

The concentrations of 41 phenols in leachates from 38 municipal solid waste (MSW) landfill sites in Japan were measured. The main phenols detected in leachates were phenol, three cresols, 4-tert-butylphenol, 4-tertoctylphenol, 4-nonylphenol, bisphenol A, and some chlorophenols. The concentration levels of phenols were affected by the pH values of the leachates and the different types of landfill waste. The origins of phenol and p-cresol were considered to be incineration residues, and the major origin of 4-tert-butylphenol, bisphenol A, and 2,4,6-trichlorophenol was considered to be solidified fly ash. In contrast, the major origins of 4-tert-octylphenol and 4-nonylphenol were considered to be incombustibles. The discharge of leachates to the environment around MSW landfill sites without water treatment facilities can cause environmental pollution by phenols. In particular, the disposal of incineration residues including solidified fly ash and the codisposal of solidified fly ash and incombustibles might raise the possibility of environmental pollution. Moreover, the discharge of leachates at pH values of 9.8 or more could pollute the water environment with phenol. However, phenol, 4-nonylphenol, and bisphenol A can be removed to below the con centration levels that impact the environment around landfill sites by a series of conventional water treatment processes.     

Roadside Rhododendron pulchrum leaves as bioindicators of heavy metal pollution in traffic areas of Okayama, Japan

The leaves of roadside Rhododendron pulchrum Sweet were examined as a bioindicator of traffic-related heavy metal pollution in Okayama. Total contents of heavy metals in roadside soil and the R. pulchrum leaves were determined. Results of correlation analyses showed significant correlations among Pb, Ni, and Zn contents of roadside soil and leaf samples. These results suggest that R. pulchrum is a useful bioindicator of heavy metal pollution in traffic areas. To identify traffic-related heavy metal pollution sources, traffic-related materials such as tires, asphalt pavement, and road paint were collected and analyzed. The results of analyses of our data show that Zn is emitted mainly from the abrasion of tires; Cr is emitted mainly from wear of the asphalt pavement. Furthermore, the respective lead isotope ratios in R. pulchrum leaves, soil, roadside dust, and traffic-related materials were measured using inductively coupled plasma mass spectrometry. The isotopic compositions of lead in R. pulchrum leaves were 207Pb/206Pb = 0.861-0.871 and 208Pb/206Pb = 2.093-2.127, which agrees well with ratios in automobile wheel balance weights, suggesting that lead-containing products associated with automobiles, such as wheel balance weights, contribute to traffic-related lead pollution.     

The breeding cycles of two species of grapsid crabs (Crustacea: Decapoda) from the North Coast of Kyushu,Japan

The incidence of ovigerous females in populations of two grapsid crabs, Hemigrapsus penicillatus (de Haan, 1835) and Sesarma (Parasesarma) pictum (de Haan, 1835) were followed from August 1975 to November 1976. H. penicillatus, which inhabits the lower intertidal region near the mouth of Tatara-Umi Estuary, breeds from March to November. S. pictum, which inhibits crevices and abandoned holes of other species and is abundant at and above the upper intertidal region of the estuary, breeds from May to September. H. penicillatus matures when the female reaches 6 to 7 mm carapace width, whereas S. pictum becomes mature when the carapace width is 12 to 13 mm, although the maximum size attained by females of both species is almost the same. H. penicillatus produces 5 to 6 broods, S. pictum 2 to 3 broods, during a breeding season. The size of a newly laid egg of H. penicillatus is smaller than that of S. pictum. The number of eggs produced by a female H. penicillatus is greater than that of S. pictum during a breeding season. In both species the peak of the breeding season is during summer, at which time the ovarian activity is also apparently accelerated. The major environmental factor which controls the breeding in these crabs appears to be temperature. H. penicillatus is submerged at every high tide, and is relatively inactive from late November to February when the ambient water and air temperatures are rather low. S. pictum is dormant in crevices or understones of the splash zone from November to March. The length of the breeding season of these crabs appears to be inversely proportional to the period of their winter dormancy.     

Individual sex ratios and offspring emergence patterns in a parasitoid wasp, Melittobia australica (Eulophidae), with superparasitism and lethal combat among sons

Since the mating of the parasitoid wasp Melittobia australica occurs on their eclosed hosts, the sex ratio is predicted to follow the local mate competition (LMC) theory. However, while LMC models predict that the sex ratio will increase from female-biased toward a 1:1 ratio with an increase in the number of foundresses, the observed female-biased sex ratios (1–5% males) show little increase in response to an increased foundress number. Lethal combat among adult males may serve as an explanation for this observed phenomenon. Using a microsatellite DNA marker, we first examined the individual sex ratio of two foundresses who had sequentially parasitized the same host. Both foundresses produced an extremely female-biased clutch and the sex ratios of the second foundress were only slightly less biased than that of the first. A small number of sons from both foundresses emerged at a constantly low rate over a prolonged period, resulting in a temporal mixture of emerging males derived from both the foundresses. Second, we conducted a one-on-one arena experiment to examine the combat level in relation to the relatedness of the opponents. Almost all the later-emerging males were killed by previously eclosed males irrespective of whether they were sibs or non-sibs. These results suggest that each foundress should not produce males in a single burst, but continue to produce male eggs at a constantly low rate in order to avoid the high mortality of her own sons by lethal male-male combat. This combat may be one of factors in explaining the extremely female-biased sex ratio even with an increasing foundress number.Communicated by R.F.A. Moritz     

Improvement of permeability of waste sludge by mixing with slag or construction and demolition waste

To determine the allowable ratio of waste sludge required to ensure an aerobic zone in the landfill, we investigated sludge permeability, which involved mixing sludge, the major landfill waste in Japan, at different mixing ratios with other wastes (slag and construction and demolition waste (C&D)). We measured parameters of sample permeability and analyzed parameters that exert a large influence on oxygen penetration depth with a simulation model accounting for both diffusion and convection driven by temperature gradients. We also determined the critical volumetric contents in which gas and/or water permeability change significantly when sludge is mixed with sand or gravel. From the results of the simulations, gas permeability of the layer, the difference between inside and outside temperatures and the oxygen consumption rate exert a large influence on the resulting oxygen penetration depth. The allowable ratio of sludge required to ensure an aerobic zone in the landfill was determined by considering the balance of the above three parameters. By keeping volumetric sludge content to below 25%, air convection and oxygen penetration depth of several meters were achieved in the modeling.