Relationships between Aerosol Extinction Coefficients Derived from Airport Visual Range Observations and Alternative Measures of Airborne Particle Mass

Epidemiological assessments of population exposures to airborne particles are often hampered by the scarcity of available fine particle mass measurements. In an attempt to overcome this serious problem, we analyze In this paper methods for predicting fine particle (M ₁) and Inhalable particle (IP) mass concentrations using relative humidity corrected light extinction coefficient (b _ext) estimated from airport visual range (V _r) observations. The analyses presented are based on theoretical determinations as well as statistical investigations utilizing EPA's NASN and Inhalable Particle Monitoring Network (IPMN) data bases and routine airport visual range observations In twelve large U.S. cities. Our results Indicate that, after controlling for certain limitations of airport visual range data, most of the regression models developed in this paper can be applied satisfactorily to predict M _t and IP. Furthermore, our findings Indicate that a more representative formula than the commonly used meteorological range formula to predict atmospheric b _ext values in urban areas may be b _ext = (1.8 ± 0.04)/V _r. Because of known local or regional influences, however, we do suggest calibration of any predictive model which utilizes airport visibility data against site-specific aerometric data on particle mass concentrations or scattering coefficient measurements.     

Summary of POHC Audit Results Using VOST and Bag Methods During RCRA Trial Burns

Audit materials containing Principal Organic Hazardous Constituents (POHCs) have been developed by EPA for use by Federal, State, and Local agencies or their contractors to assess the accuracy of measurement methods used during RCRA trial burn tests. Audit materials are currently available for 27 gaseous organics in five-, six-, seven-, and nine-component mixtures at ppb levels (7 to 10,000 ppb) in compressed gas cylinders in a balance gas of nitrogen. The logic used in selecting 27 gaseous organic compounds as audit materials and how these audit materials are successfully used in performance audits is described. Stability studies indicate that all of the organics tested (with the exception of ethylene oxide and propylene oxide below 10 ppb levels) are stable enough to be used as reliable audit materials. As of January 1990, 215 performance audits have been conducted to assess the accuracy of Volatile Organic Sampling Train (VOST) and bag measurement methods during or prior to RCRA trial burn tests. A summary of the audits conducted for each POHC, the measurement system audited, and the frequency of audits is described. The audit results obtained with audit gases are generally within ±50% of the audit concentrations.     

The Great Recession or progressive energy policies? Explaining the decline in US greenhouse gas emissions forecasts

This paper evaluates the causes of the 23% decline in 2030 US greenhouse gas emissions forecasts between 2007 and 2011. Dynamic regression modeling predicts that the Great Recession contributed to about 67% of the 2008–2009 emissions decline, but then fell to about an 18% share for the 2030 emissions forecast. An analysis of electricity generation forecasts show that switching from coal to gas contributed only 6% to the total 2030 decline. In contrast, regulatory impact assessments and policy analysis showed that state and federal policies were responsible for 46% of the 2030 decline in emissions.     

Contributions of humic substances to the dissolved organic carbon pool in wetlands from different climates

Wetlands are an important source of DOM. However, the quantity and quality of wetlands' DOM from various climatic regions have not been studied comprehensively. The relationship between the concentrations of DOM (DOC), humic substances (HS) and non-humic substances (NHS) in wetland associated sloughs, streams and rivers, in cool temperate (Hokkaido, Japan), sub-tropical (Florida, USA), and tropical (Sarawak, Malaysia) regions was investigated. The DOC ranged from 1.0 to 15.6 mg CL(-1) in Hokkaido, 6.0-24.4 mg CL(-1) in Florida, and 18.9-75.3 mg CL(-1) in Sarawak, respectively. The relationship between DOC and HS concentrations for the whole sample set was regressed to a primary function with y-intercept of zero (P<0.005) and a slope value of 0.841. A similar correlation was observed between DOC and NHS concentrations, with a smaller slope value of 0.159. However, the correlation coefficient of the latter was much larger when the data was regressed to a logarithmic curve. These observations suggest the presence of a general tendency that the increased DOC in the river waters was mainly due to the increased supply of HS from wetland soils, whereas the rate of the increase in the NHS supply has an upper limit which may be controlled by primary productivity.     

Dioxine in Lagerstätten-Tonen

In dominantly kaolinite-type, natural clay minerals, we found PCDDs at considerable levels (TEQ-values up to several hundred ng/kg). Contrary to expectations, PCDFs were not detected at all. The PCDD-contamination is most likely “natural” and not of anthropogenic origin.     

Experiences from phasing out the use of mercury in Sweden

The Swedish parliament has decided that the use of mercury (Hg) in society should be phased out by the target year 2000 and substituted with alternative, less harmful elements or compounds. This is to reduce exposure to the toxic heavy metal, levels of which have increased two to seven times in the Swedish environment during the last century. Mercury in products and goods in use in Sweden has been estimated at 100 tonnes Hg, which will slowly be released into the environment if no preventative measures are taken. To avoid handing over unsolved environmental problems and connected costs to future generations, the Swedish government commissioned the Swedish Environmental Protection Agency (EPA) to improve the efficiency of Hg collection and to find a solution for terminal storage of the waste. The result is that the Swedish EPA considers deep storage in rock, accompanied by technical measures to further reduce the risk of future Hg emissions to be the safest method. It has funded approximately 50 projects with the goal of spreading information about the Hg problem and removing Hg from society. The projects have focused on areas where there is a great risk of Hg in products and goods entering the environment. About 6 tonnes Hg has so far been collected in these projects – end of 1999 – and the cost of the Hg collected has varied between 70 and 1300 US$ kg^–1 Hg. The projects were more cost-effective than traditional inspection by an official due to local participation, use of Hg-tracker dogs, and employment of professional electricians in the search for Hg. The involvement of school children and the public has resulted in an increased awareness of environmental matters, and, together with the emptying of water seals, reduced Hg levels in municipal sewage sludge. Electronic Publication     

Biogeochemical patterns in a river network along a land use gradient

The Bode catchment (Germany) shows strong land use gradients from forested parts of the National Park (23 % of total land cover) to agricultural (70 %) and urbanised areas (7 %). It is part of the Terrestrial Environmental Observatories of the German Helmholtz association. We performed a biogeochemical analysis of the entire river network. Surface water was sampled at 21 headwaters and at ten downstream sites, before (in early spring) and during the growing season (in late summer). Many parameters showed lower concentrations in headwaters than in downstream reaches, among them nutrients (ammonium, nitrate and phosphorus), dissolved copper and seston dry mass. Nitrate and phosphorus concentrations were positively related to the proportion of agricultural area within the catchment. Punctual anthropogenic loads affected some parameters such as chloride and arsenic. Chlorophyll a concentration and total phosphorus in surface waters were positively related. The concentration of dissolved organic carbon (DOC) was higher in summer than in spring, whereas the molecular size of DOC was lower in summer. The specific UV absorption at 254 nm, indicating the content of humic substances, was higher in headwaters than in downstream reaches and was positively related to the proportion of forest within the catchment. CO₂ oversaturation of the water was higher downstream compared with headwaters and was higher in summer than in spring. It was correlated negatively with oxygen saturation and positively with DOC concentration but negatively with DOC quality (molecular size and humic content). A principle component analysis clearly separated the effects of site (44 %) and season (15 %), demonstrating the strong effect of land use on biogeochemical parameters.     

Phosphorus recovery from wastewater--expert survey on present use and future potential

Today, a variety of different approaches to the recovery of phosphorus from wastewater, sludge, and sludge ash exist. These approaches differ basically by the origin of the used matter (wastewater, sludge liquor, fermented or nonfermented sludge ash) and the process (precipitation, wet-chemical extraction, and thermal treatment). To rate them according to their characteristics, the latter were phrased as hypotheses and subjected to an international expert survey. The survey showed that phosphorus recovery is expected to become an established process over the next 20 years in industrialized countries for economic reasons. A decisive aspect in this regard will be the quality of the produced fertilizer. Simple technologies such as the recovery from sludge liquor seem to be preferred. If sludge is incinerated, phosphorus recycling from ash then becomes more interesting and has to be considered. Phosphorus recovery and source-separating sanitation technologies are more appropriate for industrialized countries than for developing countries. Because the growing awareness of environmental issues will prevent sludge from being used agriculturally in an increasing number of countries in the next decade, the market potential for nutrient recovery technologies will increase in the immediate future.