Environ. Sci. Techno/. 1995, 29, 2217-2221
Off-Site Forensic Determination of Airborne Elemental Emissions by Muhi-Media Analysis: A Case Study at Two Secondary Lead Smelters D A V I D E U G E N E KIMBROUGH* Department of Toxic Substances Control, California Environmental Protection Agency, Southern California Laboratory, 1449 West Temple Street, Los Angeles, California 90026-5698
I. H. SUFFET School of Public Health, Environmental Science and Engineering Program, University of California, Los Angeles, Los Angeles, California 90095-1 772
A study is presented of multi-element multi-media airborne emissions via analysis of solids, soils, wipes, and glass fiber filters on and around two secondary lead smelters. Characteristic ratios of 1ead:antimony:arsenic were found in all of these media along with a correlated presence of cadmium and silver. The further the medium was from the plant, the less of all of these elements found while the ratio was maintained. Media downwind had higher concentrations than upwind in other directions. Conclusive forensic evidence was accumulated as to the origin and route of emission of the elements.
Introduction The exposure of people to airborne emissions of toxic elements, particularly lead, from industrial sites has been the subject of many studies (1-9). The approach in most studies has been to examine the concentrations of a single element in the air and in the blood of the local population. In many situations, this is sufficient as there may only be a single possible source that may emit a single airborne element. In urban industrialized settings, this approach may be simplistic. There can often be many sources of a particular element, and it may not be released alone. In order to fully characterize the elemental airborne concentrations that a population is exposed to or the emissions from a site, it is important to analyze all toxic elements in a variety of media. This is important for two reasons. First, in order to establish a full risk assessment, it is important to know all of the toxic agents. Second, it is important to distinguish the sources of airborne lead. A high volume air sampler can pickup lead from a variety of sources, such as from a smelter, automobiles, or even the soil. Airborne emissions can also deposit on the soil, which can be resuspended by the wind and collected in a sampler. By examining a wide range of elements, their sources can be distinguished.
0013-936X/95/0929-2217$09.00/0
@ 1995 American Chemical Society
Not only must all of the elements of interest be examined, they should be examined in a variety of media. Airborne emissions do not occur uniformly from industrial sites.They occur at specific points in the product process. They may be emitted during the transportation or storage of raw materials, during the processing of those materials, during the final manufacturing, or during the transportation of the final product. The elemental composition of materials can change through the industrial process. Thus, depending at which point in the process emissions are occurring, the elemental composition will change. Airborne emissions can be deposited on other materials, which can either be resuspended and inhaled, ingested, or inhaled directly. For this reason, the analysis of soils or other vectors must be analyzed in addition to glass fiber filters from high volume air samplers. Likewise, the solid materials used in production must also be analyzed. When the complete suite of toxic elements is determined for the source materials, air, soil, and other vector materials, a more definitive causal connection can be made between a site and a source. In t h i s paper, a study of airborne emissions from secondary lead smelters is presented as a case study to determine the usefulness of multi-element multi-media analysis. The approach used to examine the actual air concentrations of various toxic elements as well as the their concentrations in the soil, in solid materials, and in wipes compared the ratios of these elements in the various media and determined the nature and sources of the emissions. Such a determination would allow for a complete source assessment and identification of an air-emission source.
Secondary lead Smelters Lead-acid batteries consist of a plastic casing and cap that form a number of wells. In each well are two grids, one of lead and the other of lead oxide immersed in sulfuric acid. The lead is hardened by adding antimony. Arsenic is added to prevent the exchange of lead between the anode and the cathode during overcharging or excessive discharge. Cadmium is also present in low ppm concentrations as either an alloy or as a contaminant (10).The ratio of these elements is approximately 1000Pb:50 Sb:10As:l Cd,within the variation among several different types of lead-acid batteries. Antimony varies the most between batteries, ranging from 2% to 10% with 5% being very common. Additionally, some batteries use additional elements such as barium, chromium, nickel, selenium, silver, and zinc. Lead-acid battery recyclers crack the plastic cases, neutralizethe acid, wash the crushed batteries, and separate lead-based materials from the plastic parts. The pulverized scraps and the resulting particulate material are either transported to or stored at the secondary smelter. Storage may be in controlled buildings or simply outside. The scrap is placed in a furnace (e.g., blast, electric, reverbatory, or rotary reverbatory furnace) where any combustible materials are rapidly oxidized and volatilized and alloys are added or removed. Under these conditions, the lead and its alloys are all very volatile, and metallic and oxide fumes are formed. The fumes form very small mass median aerodynamic diameter particles that can travel significant distances. Once the ingots are formed, they can be sent to other manufacturers to be recast. While ingots
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for batteries are a common end product for recycled batteries, they are by no means the only product. Other alloys of lead may be produced in these smelters. The goal of this study was to examine a variety of media from on and around secondary lead smelters for the concentrations of target toxic elements in different environmental media mentioned above, namely, glass fiber filters from high volume air samplers, soils, solids, and paper wipes.
Experimental Section Two sites that were studied were designated as site 1 and site 2. Both are secondarylead smelters located in-between railroad tracks and a river within 1 mi of a major highway. Each of these sites has three to four fence-line high volume air samplers and two to three on-site samplers. Samples were taken August 5, 1993, from both the on-site and offsite samplers at both locations. At site 1, the winds generally blow from the west based on a 1958 study ( 1 1 ) . A 1991 study over a 3-month period showed that if calm winds (‘5 kph) are neglected, winds from the southwest constitute 75%of those measured. Only the northeast corner fence-line air samplers were operating on August 5. The off-site samplers are located 1 km due north and 2 km northeast of this plant. This means that there are three data points for this site on this day all from north and east of the plant. For comparison, the filters from the same off-site samplers were analyzed from October 9, 1991. At site 2, the winds are principallyfrom the south, ranging from west southwest to southeast based on a 1958 study (11). Three of the four fence-line air samplers were operating, north, northeast, southeast, and south of the plant. The off-site samplers are located 500 m due north, 800 m northeast, and 50 m due south of this plant. This means there are six data points for this site on this day. For comparison, the filters from all four fence-line and all three off-site samplers were analyzed from April 12, 1992, for a total of seven data points. The filters were prepared for sampling according to the Code of Federal Regulations (40 CFR, Part 50, Appendix B (12)).The filterswere equilibrated for 24 h before sampling. The filters were then placed in the high volume air samplers, and the samplers were operated for 24 h. The filters were collected and analyzed. The soil, solid, and wipe samples were collected over a period of 2 years as part of a law enforcement effort by the Toxic Substances Control Program of the California Department of Health Services (nowknown as the Department of Toxic Substances Control of the California Environmental Protection Agency). Soils and solids were collected from site 1both on and off-site from the ground. Solids included drosses, slags, and foundry wastes that were laying open on the ground. Distances and locations were not recorded. Only off-site soils were collected from site 2, but distance and locations were recorded. Part of this effort involved a simple deposition study. A car was parked outside of site 1, and a measured section of the hood was wiped with a cellulosewipe. After several hours, the same areawas wiped again. Both wipes were analyzed for the target elements. All of the materials were analyzed by U.S. EPA SW 846 Method 3050B aqua regia acid digestion procedure (1316) and analyzed by Method 6010, inductively coupled plasma atomic emission spectroscopy (ICP-AES)( 1 7). This combination of procedures has been shown to be effective 2218
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 29, NO. 9 , 1 9 9 5
TABLE 1
Solid Sample Results for Site la Pb
ID location 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 a
on-site on-site on-site on-site on-site on-site on-site on-site on-site on-site off-site off-site off-site off-site off-site
Sb
Cd
As
Cr
cu
Ni
110000 1500 300 39 320 320 40 65 10 25 750 58 19 000 520 47 21 110 17 110 000 530 110 30 7 150 14 130000 3600 150 27 130 3500 89 35 000 1300 220 100 000 13 000 1000 210
