Airborne emissions of mercury from municipal solid waste. I: new measurements from six operating landfills in Florida

Mercury-bearing material enters municipal landfills from a wide array of sources, including fluorescent lights, batteries, electrical switches, thermometers, and general waste; however, the fate of mercury (Hg) in landfills has not been widely studied. Using automated flux chambers and downwind atmospheric sampling, we quantified the primary pathways of Hg vapor releases to the atmosphere at six municipal landfill operations in Florida. These pathways included landfill gas (LFG) releases from active vent systems, passive emissions from landfill surface covers, and emissions from daily activities at each working face (WF). We spiked the WF at two sites with known Hg sources; these were readily detected downwind, and were used to test our emission modeling approaches. Gaseous elemental mercury (Hg(O)) was released to the atmosphere at readily detectable rates from all sources measured; rates ranged from approximately 1-10 ng m(-2) hr(-1) over aged landfill cover, from approximately 8-20 mg/hr from LFG flares (LFG included Hg(O) at microg/m3 concentrations), and from approximately 200-400 mg/hr at the WF. These fluxes exceed our earlier published estimates. Attempts to identify specific Hg sources in excavated and sorted waste indicated few readily identifiable sources; because of effective mixing and diffusion of Hg(O), the entire waste mass acts as a source. We estimate that atmospheric Hg releases from municipal landfill operations in the state of Florida are on the order of 10-50 kg/yr, substantially larger than our original estimates, but still a small fraction of current overall anthropogenic losses.     

Simultaneous nitrification-denitrification and clarification in a pseudoliquified activated sludge system.

This paper describes results from a pilot study of a novel wastewater treatment technology, which incorporates nutrient removal and solids separation to a single step. The pseudoliquified activated sludge process pilot system was tested on grit removal effluent at flowrates of 29.4 to 54.7 m3/d, three different solid residence times (SRT) (15, 37, and 57 days), and over a temperature range of 12 to 28 degrees C. Despite wide fluctuations in the influent characteristics, the system performed reliably and consistently with respect to organics and total suspended solids (TSS) removals, achieving biochemical oxygen demand (BOD) and TSS reductions of > 96% and approximately 90%, respectively, with BOD5 and TSS concentrations as low as 3 mg/L. Although the system achieved average effluent ammonia concentrations of 2.7 to 3.2 mg/L, nitrification efficiency appeared to be hampered at low temperatures (< 15 degrees C). The system achieved tertiary effluent quality with denitrification efficiencies of 90 and 91% total nitrogen removal efficiency at a total hydraulic retention time of 4.8 hours and an SRT of 12 to 17 days. With ferric chloride addition, effluent phosphorous concentrations of 0.5 to 0.8 mg/L were achieved. Furthermore, because of operation at high biomass concentrations and relatively long biological SRTs, sludge yields were over 50% below typical values for activated sludge plants. The process was modeled using activated sludge model No. 2, as a two-stage system comprised an aerobic activated sludge system followed by an anoxic system. Model predictions for soluble BOD, ammonia, nitrates, and orthophosphates agreed well with experimental data.     

Analysis of air quality observations with the aid of the source-receptor relationship approach

In this study, an attempt was made to analyze time series of air quality measurements (O3, SO2, SO4(2-), NOx) conducted at a remote place in the eastern Mediterranean (Finokalia at Crete Island in 1999) to obtain concrete information on potential contributions from emission sources. For the definition of a source-receptor relationship, advanced meteorological and dispersion models appropriate to identify "areas of influence" have been used. The model tools used are the Regional Atmospheric Modeling System and the Lagrangian-type particle dispersion model (forward and backward in time), with capabilities to derive influence functions and definition of "areas of influence." When high levels of pollutants have been measured at the remote location of Finokalia, particles are released from this location (receptor) and traced backward in time. The influence function derived from particle distributions characterizes dispersion conditions in the atmosphere and also provides information on potential contributions from emission sources within the modeling domain to this high concentration. As was shown in the simulation results, the experimental site of Finokalia in Crete is influenced during the selected case studies, primarily by pollutants emitted from the urban conglomerate of Athens. Secondarily, it is influenced by polluted air masses arriving from Italy and/or the Black Sea Region. For some specific cases, air pollutants monitored at Finokalia were possibly related to war activities in the West Balkan Region (Kosovo).     

Airborne emissions of mercury from municipal solid waste. II: potential losses of airborne mercury before landfill

Waste distribution and compaction at the working face of municipal waste landfills releases mercury vapor (Hg(o)) to the atmosphere, as does the flaring of landfill gas. Waste storage and processing before its addition to the landfill also has the potential to release Hg(o) to the air if it is initially present or formed by chemical reduction of Hg(II) to Hg(o) within collected waste. We measured the release of Hg vapor to the atmosphere during dumpster and transfer station activities and waste storage before landfilling at a municipal landfill operation in central Florida. We also quantified the potential contribution of specific Hg-bearing wastes, including mercury (Hg) thermometers and fluorescent bulbs, and searched for primary Hg sources in sorted wastes at three different landfills. Surprisingly large fluxes were estimated for Hg losses at transfer facilities (approximately 100 mg/hr) and from dumpsters in the field (approximately 30 mg/hr for 1000 dumpsters), suggesting that Hg emissions occurring before landfilling may constitute a significant fraction of the total emission from the disposal/landfill cycle and a need for more measurements on these sources. Reducing conditions of landfill burial were obviously not needed to generate strong Hg(o) signals, indicating that much of the Hg was already present in a metallic (Hg(o)) form. Attempts to identify specific Hg sources in excavated and sorted waste indicated few readily identifiable sources; because of effective mixing and diffusion of Hg(o), the entire waste mass acts as a source. Broken fluorescent bulbs and thermometers in dumpsters emitted Hg(o) at 10 to >100 microg/hr and continued to act as near constant sources for several days.     

On purpose in science,conservation and government. The functional integrity of the earth is at issue not biodiversity

The objectives of conservation have been focused ever more intensively for two decades on the preservation of "biodiversity." Emphasis has been on the losses of species through extinction. The cure has been the establishment of parks and reserves to protect "hot spots," especially in the tropics, where the diversity of species is high. The efforts in preservation have often extended to the development of connecting links among reserves to allow movements among them. The approach has been codified in law in the form of the Endangered Species Act in the United States and the Biodiversity Treaty, both of which address the issue species by species and each of which has obvious weaknesses. Such efforts may be appropriate but they are totally inadequate as the sum of activities in conservation in a world of 6 billion people with exploding technologies for exploiting virtually all of the earth for immediate human benefit. The biosphere is decaying rapidly as a habitat for all life, including people, not because of the extinction of species, but because of the progressive impoverishment of natural communities through human-induced chronic disruption that is now global and ubiquitous. The improverishment leads to progressive environmental dysfunction that is cumulative, but only in its later stages leads to extinction of species. Long before extinction becomes important, genetically distinct, local ecotypes are lost and the natural communities in which they were developed become improverished and dysfunctional. The most conspicuous disruption is that of climate, a global change in the environment of every ecosystem. The most elaborate and carefully interlinked array of natural reserves will succumb as climate is moved out from under them... and biodiversity will suffer the very extinctions the parks were established to avoid. But long before that, the human environment will suffer conspicuous and progressive impoverishment. The objective of conservation is the preservation of the integrity of function of landscapes (and waterbodies). Emphasis falls on forests in the normally naturally forested parts of the earth because forests are so large in area globally and have such a large influence on virtually every aspect of environment. Functional integrity requires structural integrity over 85% or more of the naturally forested zone in most areas. It also requires objective measurement and definition by the scientific community. Suddenly, conservation has become, not the preservation of biodiversity, honorable as that may be, but the preservation of the functional integrity of the human environment. That purpose is the central purpose that we assign to the governments that we establish in democracies to define and defend the public interest. It is past time for the scientific and conservation communities to recognize the urgency of this transition, join in defining competent new objectives for conservation, and to convey to the public the urgency of the need for governmental responsibility in protecting the public interest in a habitable biosphere.     

Residues and half-lives of pyrethrins on field-grown pepper and tomato

The dried flower heads of Tanacetum cinerariifolium Trev. (Family: Compositae) contain insecticidal compounds collectively called "pyrethrins." Pyrethrins are the subject of intense interest for use in crop protection because their toxicological properties permit control of certain insect species at application rates as low as 5-10 g AI acre(-1). Seedlings of sweet pepper, Capsicum annuum L. cv. Bell Boy Hybrid and tomato, Lycopersicon esculentum Mill. cv. Mountain Spring F1 Hybrid were planted and sprayed with a Multi-Purpose Insecticide formulation that contains 0.2% pyrethrins, 1.0% piperonyl butoxide (PBO), 88% diatomaceous earth, and 10.8% inert ingredients. The formulation was sprayed on pepper and tomato foliage when tomato fruits became red ripe and pepper became mature green at the rate of 6 lbs of formulated product per acre (5.4 and 27.2 g AI of pyrethrins and PBO, respectively). Following spraying, pepper and tomato leaves and fruits were collected at different time intervals for residue analysis using a high performance liquid chromatograph (HPLC) equipped with a UV detector. Residues of pyrethrins and PBO were generally higher on the leaves than fruits. Initial deposits (1 h following spraying) of pyrethrins were significantly higher on pepper than tomato fruits. Half-life (T1/2) values on pepper and tomato fruits did not exceed 2 h. Where concern exists over synthetic pesticide residues on treated crops and in the environment, pyrethrins are suitable alternatives that can be used to reduce the risk of exposure to synthetic pesticide residues.     

新型循环流化床硝化-反硝化启动试验研究

利用新型循环流化床进行清水实验及硝化、反硝化启动试验研究,考察了系统对有机物和氮的去除效果,并分析了曝气量对系统启动的影响.结果表明,将输送床和传统流化床工艺进行有机结合,技术上可行,可以在系统内不同区建立缺氧、好氧条件,通过硝化和反硝化作用完成脱氮.     

Making chlorine greener: performance of alternative dechlorination agents in wastewater

The residual chlorine in chlorine-disinfected and dechlorinated wastewater was characterized using a liquid chromatograph that was switched between reversed-phase separation and flow injection analysis modes, permitting measurement of fractionated and total residual chlorine, respectively. Residuals were detected in the effluent of an operating wastewater treatment plant employing chlorine disinfection and sulfite dechlorination. Despite dechlorination, an estimated total residual chlorine of 3 microM (0.2 ppm as Cl2) was detected in the effluent. To improve dechlorination effectiveness, four alternative agents (ascorbic acid, iron, sulfite plus iodide mediator, thiosulfate) were compared to sulfite on laboratory-chlorinated wastewater. Listed in order of decreasing relative effectiveness, we found: iron metal > sulfite plus iodide approximately = thiosulfate > sulfite > ascorbic acid. Only the iron metal column was completely effective at rapidly removing all traces of residual chlorine.     

Treatment of food industry waste by bench-scale upflow anaerobic sludge blanket-anoxic-aerobic system.

An upflow anaerobic sludge blanket (UASB)-anoxicaerobic system was used for treatment of tomato and bean processing wastewater. At various hydraulic retention times, ranging from 0.7 to 5 days, excellent removal of chemical oxygen demand (COD), biochemical oxygen demand (BOD), total suspended solids (TSS), ammonia-nitrogen (NH4-N), and total Kjeldahl nitrogen was achieved with final effluent BOD/TSS/NH4N concentrations of less than 15/15/1 mg/L. Biogas yield in the UASB reactor varied from 0.33 to 0.44 m3/kgCODremoved. The kinetics of anaerobic treatment were investigated. The yield coefficient was 0.03 gVSS/gCOD; maximum specific growth rate was 0.24 day(-1); Monod half velocity constant was 135 mgCOD/L; and specific substrate utilization rate was 3.25 gCOD/gVSS x d. Nitrification and denitrification kinetics were studied in batch experiments, and the rates were comparable with those in the continuous flow system.