University of FloridaSolutions for Your Life

Download PDF
Publication #SL 152

Arsenic Contamination from Cattle-Dipping Vats1

J.E. Thomas, R.D. Rhue, and A.G. Hornsby2

Why are there vats in Florida?

From the period 1906 to 1962, approximately 3400 cattle-dipping vats were constructed throughout Florida for the purpose of eradicating the tick responsible for transmitting a disease called "southern cattle fever" (Graham and Hourrigan 1977). Vats, which were constructed with concrete, became the preferred method of tick eradication in Florida due to their thoroughness, speed, and relative simplicity. Additionally, pasture rotation was not a viable alternative since Florida was an open range state until about 1947. Typically, the vats were 25 to 30 feet long, 7 feet deep, and 2.5 to 3 feet wide (Figure 1). Each vat held 1500 to 2000 gallons of dipping solution which contained 0.14 to 0.22 percent arsenic by weight (Ellenberger and Chapin 1919). Ideally, vats were to be emptied yearly, generally in the early spring. Disposal of the old dip solution was done by one of two ways: 1) running it into a nearby pit where it eventually seeped into the ground, or 2) precipitating the arsenic out of the solution with iron sulfate plus quicklime, then burying the resulting sludge in a pit (Dawson 1913). These practices have resulted in many small areas around the state with localized arsenic pollution of soil and, in some cases, groundwater as well. Around the mid-1940s, experimentation with chlorinated pesticides as a replacement for arsenic was prevalent. This resulted in the soil around many dip vats being contaminated with chemicals such as DDT, DDE, toxaphene, and BHC in addition to the arsenic contamination (Graham and Hourrigan 1977).

Figure 1. 

Schematic of Cattle-Dipping Vat.


[Click thumbnail to enlarge.]

How toxic is arsenic?

Virtually everyone is aware that arsenic can be toxic. It has been featured in many murder mysteries, plays, and films, such as "Arsenic and Old Lace." One underappreciated facet of arsenic toxicology is that the lethal dose of arsenic varies with its speciation. In general, methylated and other organo-arsenicals are less toxic than inorganic arsenic. As illustrated in Table 1, arsenic can be classified as highly toxic when in the inorganic form, and as innocuous to humans when present as certain organo-arsenicals. Such is the case for seafood, where arsenic is present as arsenobetaine, which is relatively nontoxic (Yamauchi and Fowler 1994; Cullen and Reimer 1989; Irgolic 1991; Freeze and Cherry 1979). LD 50 is defined as the amount of arsenic compound that when ingested at the rates specified below would kill 50% of the test species. Rats and mice are commonly used to evaluate the mammalian toxicity of compounds. The larger the LD 50 , the lower the toxicity to mammals.

What are the regulatory limits for arsenic?

Regulatory agencies set the allowable arsenic limits based on "total concentration" rather than "species concentration." It is simply not economical to quantify the multitude of arsenic species. Although regulatory decisions on allowable concentrations do not vary by species, there are variations based on the background matrix and its intended purpose.

The USEPA (United States Environmental Protection Agency) limits for water are presented in Table 2 (Irgolic 1991; Freeze and Cherry 1979). However, there is no limit set for arsenic in soil, except as an upper limit of 5 mg/L for the USEPA Toxicity Characteristic Leaching Procedure (TCLP) (USEPA 1992). The TCLP yields a number that could correlate with how much of the arsenic would wash out of the soil. Other factors, such as the influence of biota, are not taken into account with this procedure.

How far will arsenic move?

A study of cattle-dipping vat sites has concluded that several factors influence the movement of arsenic (Thomas 1998). Among the findings are:

  • the extent of the arsenic contaminant plume is determined by the hydrology of the site;

  • arsenic tends to associate with aluminum and iron oxides/hydroxides found in soil clay layers;

  • if the hydraulic conductivity of the soil is low, then the transport of arsenic is restricted, although high clay content alone does not necessarily stop the downward movement of arsenic.

It was also found that the topography of the upper surface layer of the clay would influence the shape of the contaminant plume. If a high organic layer, such as a spodic horizon is present, then it can adsorb an appreciable amount of arsenic, in comparison to the lighter-colored sand surrounding it. At cattle-dipping vat sites that contain only uncoated sand, without clay or organics, the arsenic will be very mobile, and the arsenic plume may be exceedingly difficult to locate. It is often presumed that the arsenic has been washed out of these sites during the last thirty years since these vats were last used.

If soil surveys and topography maps are consulted and on-site verification has been completed, then soil sampling for arsenic can be planned with a fair amount of accuracy. For example, if there is an argillic horizon present, it will contain the highest concentration of arsenic. If iron-bearing (red) nodules with a clay coating are present in the contaminant plume, then arsenic will concentrate in this coating. A similar concentration effect will be found in any red redoximorphic features (mottles) found in the soil, assuming that contact with the arsenic plume has occurred sometime in the past. If a spodic horizon is present, then the plume will migrate a considerable distance laterally from the vat. As mentioned previously, the arsenic will leave a trail within these spodic horizons. If the soil is an uncoated quartzipsamment, the arsenic may leave little trace of its passage. However, if it is a coated quartzipsamment, the plume trail will be detectable, although in low concentrations.

The direction of plume migration will be in the direction of water flow. Equally obvious is the observation that if you were to empty a vat then the direction you would toss the dip solution would be downhill from the vat. A topographical map can give insight into the direction of groundwater flow. However, only on-site sampling and inspection can confirm the soil series and groundwater flow.

How can soil and water be tested for arsenic?

If you suspect that your soil and/or water has been contaminated with arsenic, the only way to know for sure is to have it tested. A colorimetric test kit for water is available commercially. This test kit can be modified for soil (Thomas 1998). The arsenic colorimetric test involves converting the arsenic in the soil or water into a volatile gas that reacts with a color strip. The color strip changes from original white to light yellow, to orange-tan, to dark chocolate brown, depending on the amount of arsenical gas generated.

Arsenic testing can be done by commercial laboratories as well. Commercial labs typically do not use colorimetric methods for trace metal analysis. Instead, the analytical techniques involve atomic absorption spectrometry, neutron activation or inductively coupled argon plasma spectrometry. These methods require sophisticated laboratory equipment.

If you wish to submit your samples to a commercial laboratory, the first step is to contact the lab and receive specific instructions on how to collect and submit a sample; often the laboratory may want to collect the sample. In all cases, the collection of a representative sample is essential.

Taking a good soil or water sample involves the following:

  • The sampling bottle should be clean and acid-rinsed.

  • Nothing except the soil or water sample should come in contact with the inside or the cap of the bottle.

  • Soil samples should be taken with clean equipment and refrigerated after collection.

  • Water samples should come from a clean faucet with no leaks around the handle. A good technique is to let the water run for a few minutes before taking the sample.

  • Best results will be obtained if the samples are analyzed within 24 hours. Storage should never exceed three months.

For more information:

• Contact your local or state health department.

• Contact you local or state environmental protection department.

• Contact the Cooperative Extension Service in your county.

• Locate the cattle-dipping vat evaluation packet in the Farm*A*Syst materials which are available on CD-ROM #11 from the UF/IFAS Florida Information Retrieval Service (FAIRS).

References

Graham, O.H. and J. L. Hourrigan, "Eradication Programs for the Arthropod Parasites of Livestock," Journal of Medical Entomology, 1977, Vol. 13, No. 6, pp. 629-658.

Ellenberger, W.P. and R.M. Chapin, "Cattle Fever Ticks and Methods or Eradication," U. S. Department of Agriculture, 1919, Farmer's Bulletin #1057, pp. 1-32.

Dawson, C.F. "Cattle Tick Eradication", State Board of Health of Florida, Publication #103, March 1913, pp. 162-214.

Yamauchi, H. and B.A. Fowler, "Toxicity and Metabolism of Inorganic and Methylated Arsenicals," In: Arsenic in the Environment, Part II: Human Health and Ecosystem Effects, Nriagu, J.O. (ed.), John Wiley and Sons, Ltd., New York, 1994, pp. 35-53.

Cullen, W.R. and K.J. Reimer, "Arsenic Speciation in the Environment," Chemical Reviews, 1989, Vol. 89, pp. 713-764.

Irgolic, K. J., "Determination of Organometallic Compounds in Environmental Samples with Element- Specific Detectors," In: Trace Metal Analysis and Speciation, I.S. Krull, (ed.), 1991, Vol. 47, pp. 21-48.

Freeze, R.A. and J.A. Cherry, "Groundwater," Prentice-Hall, Inc., New Jersey, 1979, Chap. 9, pp. 388-413.

USEPA, "Chemical-specific parameters for toxicity characteristic contaminants," Document 600/S, 3-91/004, 1992.

Thomas, J.E., "Distribution, Movement, and Extraction of Arsenic in Selected Florida Soils," Ph.D. dissertation, University of Florida, 1998, pp. 47-148.

Tables

Table 1. 

Toxicity of selected arsenic compounds to mice and rats.

Arsenic Compound

LD50 (mg/kg) (species)

Arsenite

(arsenic trioxide)

34.5

(mouse)

Arsenite

(sodium arsenite)

4.5

(rat)

Arsenate

(sodium arsenate)

14-18

(rat)

Monomethylarsonic Acid

(MA)

1,800

(mouse)

Dimethylarsinic Acid

(DMA)

1,200

(mouse)

Trimethylarsine

(TMA)

8,000

(mouse)

Trimethylarsine Oxide

(TMAO)

10,600

(mouse)

Arsenobetaine

10,000

(mouse)

Table 2. 

USEPA allowable aqueous limits.

Matrix Usage

Allowable Concentration (µg/l)

Human Drinking Water 50
Livestock Drinking Water 200
Irrigation Water for Crops 100

Footnotes

1.

This document is SL152, one of a series of the Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First published: March 1999. Reviewed: September 2003, August 2009 and August 2012. Please visit the EDIS website at http://edis.ifas.ufl.edu.

2.

J.E. Thomas, senior chemist; R.D. Rhue, professor, and A.G. Hornsby, professor emeritus, Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.