Citizens, Gardens, and Soil

In recent years, citizens of East St. Louis have been active in establishing productive gardens on previously abandoned land. Although the city lies within an area traditionally and historically of productive farmland -- the American Bottoms -- the soil has undoubtedly been changed over the last 100 years by the urban processes of development, for homes and industry, and by the increased wastes encroaching on surrounding areas. In this area some of the industries have been directly responsible for the generation of atmospheric and water pollution, including smelting and refining industries. Although industrial effluents are now largely controlled, lead and other metal and chemical contamination may still affect the soil in areas within the city. Hence, in addition to the normal concerns for soil texture and productivity, an additional factor to be considered is soil contamination at potential garden sites.

Testing for such contamination was conducted by the Department of Nuclear Engineering at the University of Illinois. Samples were taken from a site near a lead smelter plant in St. Louis with the intent that similar studies on sites in East St. Louis would follow. Possible neurological damage is one of many environmental health hazards associated with lead exposure. Wavelength Dispersive X-Ray Flourescence (WDXRF) was used to determine the prescence of lead and other heavy metals from the smelter samples. (Esguerra and Landsberger, 1994)

Through cooperative efforts between the East St. Louis Horticultural Council, and the University of Illinois, the sites for some existing and proposed gardens, located throughout the city, have been tested for soil productivity and presence of contaminants. This report discusses the results of those experiments and their implications for city-wide horticultural production.

Historical origins of current soil conditions
Consequences for likely soil conditions
Determinations of levels of metal concentration in East St. Louis soils
Consequences of soil texture and organic content for heavy metal take-up
Amelioration and remediation of polluted soils
Implications of observed soil conditions in East St. Louis
LA 437/465 Studio Work Fall94: testing and observation
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References

The historical origins of current soil conditions

At the beginning of the 20th Century the location of East St. Louis on the Mississippi River, its close economic ties with St. Louis, and the availability of land were attractive for the settlement of industries. The arrival of the railroad facilitating west-bound commerce strengthened its importance as industrialized center. Different manufacturing, chemical and metallurgic industries were drawn to and housed in the city. In particular, metal-working corporations were clustered in or near the city. Examples of these industries were: Hammar Brothers White Lead Company which opened its lead smelter in the northwest of the city around 1911 and worked for about twenty years; American Zinc that opened in 1914 and produced brass and zinc oxide among other compounds; and Aluminum Ore Company of America, established in 1913. (Colten, 1988). Activities related to the use of the raw materials from these metals plants were also developed, ie. paint production using lead and zinc derivatives. Besides the metal industries, significant chemical companies (Monsanto, Pfitzer, Socony Mobil Oil Co.) also settled in the area, close to the river for delivery of materials, and producing fertilizers and other chemicals for regional consumption.

Consequences for likely soil conditions

Because of the type of metal industry developed in the area, lead, zinc and cadmium are the trace elements most probable to be found as surface contaminants, deposited from smokestacks at the surrounding plants.

A) Cadmium

A major hazard to human health where chronic accumulation in the kidneys can cause disfunction. The FAO recommends a maximum tolerable intake of Cadmium (Cd) of 70 ug/day. Cadmium is obtained as a by-product of the smelting of Zinc and other base metals. Sewage sludge is also a major source of Cadmium. Cadmium reaches variable concentrations in different plant-organs of different species. Species such as oats, soybeans, corn and tomato accumulate more Cd in roots than in the aerial parts of the plant. Conversely, lettuce, carrot and potato accumulate more in the leaves. Soybeans accumulate more in the seeds than in the leaves. (Kabata-Pendias, 1991, Sauebeck, 1991).

B) Lead

Alloway (1990) indicated that urban soils tend to shown varying degrees of lead contamination exhibiting values that may in some locations be of the same order of magnitude as those found in and around actual smelting sites. In the USA ranges of 44-5300 ug/g soil with a median of 480 ug/g have been reported for gardens in Washington DC. The highest accumulation of lead is reported to occur in leafy vegetables (Kabata-Pendias, 1990).

C) Zinc

Zinc belongs to the group of trace metals most hazardous to the biosphere. In most countries a maximum level of 3000 mg Zinc/kg soil is adopted. Availability of Zinc decreases at higher pH. Low solubility Zn minerals are increasing adsorbed by negatively charged colloidal soil particles. High levels of Phosphorous in the soil may also decrease Zinc availability and uptake by plants. Plants grown in contaminated soils accumulate a great proportion of Zn in the roots. Magnitude of 0.X % of Zn (DW) represents a real health risk.

Determinations of levels of metal concentration in East St. Louis soils

Twelve different sites within the city of East St. Louis were sampled to determine heavy metal content of urban soils. Sample locations were taken from overlaying a regular mile-square grid over the city and sampling at each intersection on the grid, on-site personnel making final choices on the basis of choosing adjacent open land sites when the point of intersection was paved or otherwise unsuitable. The sites occur in areas zoned for a variety of uses Five soil samples taken to a depth of 4 inches with a garden trowel were obtained at each site. The five samples for each site were combined then the composite samples were air-dried and sent to the Department of Nuclear Engineering, University of Illinois at Urbana-Champaign. The determination of heavy metals was performed utilizing Wavelength Dispersive X- Ray Fluorescence (Esguerrra and Landsberger, Department of Nuclear Engineering, 1994). The principal metals determined in this study are: Lead (Pb), Zinc (Zn), and Cadmium (Cd). These elements were selected due to their association with the type of metal industry developed in the area and their potential hazard for humans. Other elements also evaluated were: Cu, Sn, V, Cr, Sr, Zr, Rb, and Ba. The results of these analysis (Figure 1) were compared with the range of proposed maximum acceptable concentrations of trace elements in soils for agricultural activities (Figure 2) (Kabat-Pendias, 1991). The results indicate that there is considerable variability in the content of Pb, Zn and Cd in the 12 sampled sites. Nevertheless, the level of these heavy metals in the soil in many cases is close to or above the limits considered acceptable for agricultural soils.

Consequences of soil texture and organic content for heavy metal take-up

The mobility of heavy metals in soils, and consequently their bioavailability, is associated with soil characteristics as CEC (Cation Exchangeable Capacity) and percentage Organic Matter in the mineral soil. The CEC is highly correlated with the clay content and clay type in the soil (Sillanpa, 1972). For these reasons these two parameters (texture and organic matter) were determine for the 12 samples analyzed for heavy metal content. The results of the texture and Organic Matter determination are presented in Table 5. The soil texture in the 12 sites varies from 48 to 79% sand and the organic matter from 2 % to 6%.

Amelioration and remediation of polluted soils

Although intensive research has been done on heavy metal contaminated soil remediation, there are aspects of the problem that remain not completely understood. Moreover, while observed values of trace elements may be quite high, each trace element has its own response to specific soil-plant conditions, making it difficult to establish satisfactory generalizations (Sauerberk, 1991). Nevertheless, some recommendation can be made for sites contaminated by heavy metals. Some measures to reduce Cadmium (Cd) soil pollution that have been summarized by Alloway (1990) are also valid for Lead (Pb) and Zinc (Zn) contamination: 1. Removing the polluted soil or covering it with a thick layer of unpolluted material, can ensure that roots do not reach the underlying polluted soil and that capillarity and/or evaporation does not bring soluble metals such as Cd into the rooting zone. 2. Adding agricultural lime to achieve ph 7 can reduce bioavailability of metals and is the most widely used remedial treatment. 3. Increasing the adsorptive capacity of the soil by adding organic matter. The effectivenes of this practice is highly related to the specific trace element in excess. The addition of organic matter does not reduce mobility for all metals. It has been shown that some metals (e.g., Cd and Cu) are mobile as organic chelates. (Sillanpaa, 1972, Lo et.al, 1992) 4. Growing non-food crops , or in cases of slight contamination growing species or cultivars with a low potential to accumulate Cd. 5. Recently heap leaching has began to be investigated a a tehnique for remediation of heavy metal contaminated soils (Hanson et al., 1992)

Implications of observed soil conditions in East St. Louis

1. The area analyzed has shown variable but generally high values of Pb, and Cd. In general these values were close to or above the admissible limits for agricultural production. The variability in the type of predominant trace element ant soil characteristics indicate that each site may deserve a different consideration. 2. One important aspect related to the remediation of soils is their situation with respect to sewage flooding -- a common problem in East St. Louis where storm sewers are in a state of decay. Besides all the usual undesirable aspects of this problem, sewage can contain high concentration of heavy metals. Therefore the successful recuperation of a site will be highly dependent on its potential for flooding. The most outstanding characteristic of the East St. Louis soil samples is their variability. However, given that that variability is unavoidable, the concommitant lack of generalization of soil recuperation measures has led to statements such that "the literature does not reveal any generally adequate method for rapid reclamation of soils heavily contaminated by trace metals. The effects of each treatment will depend upon soil properties, mainly on CEC and on plant response. Therefore, the reclamation or improvement of arable land polluted with trace elements needs to be designed to a specific plant-soil system" (Kabata-Pendias, 1990).

LA 437/465 Studio Work Fall94: testing and observation

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Working Together

Soil Texture Triangle

Soil texture and productivity

Important to soil fertility, or health, are levels of ph, Potassium (K), Nitrogen (N), and Phosphoruous (P). Samples were tested for levels of these indicators. In addition, the texture of a soil influences its productivity, or health. Subsequently, soil health directly impacts plant health. Soil is a complex combination of minerals, air, water, nutrients, and organic matter. The mineral content is derived from the eroded particles of rock which helped to form the soil. The particles which make up this content can be separated according to size; sand particles are the largest, then silt, and clay particles are the smallest. The ratio of these particles within a sample of soil is called soil texture. Soil texture is important in plant growth. Coarse sand and silt particles aid the movement of air and the drainage of water through the soil. Clay particles are smaller and help in the transfer of water and nutrients to the roots of the plants, as well as retaining moisture. A soil which is composed of 40% sand, 40% silt, and 20 % clay is considered an ideal environment for plant growth. Such a soil is considered medium textured and is called a loam. The "soil-texture triangle" is used to plot the type of soil (i.e. sandy loam, silty clay, etc.) via percentages of textures (Esguerra and Landsberger, 1994).

As part of the work for the Urban Land Potential Studio, samples from selected locations around the city were chosen for testing. The intent was to get a feel for the general quality of soils in the area for gardening or other uses. This fall, the class took samples from an additional four sites chosen by Rufus Williams of the USDA Soil Conservation Service as potentially valuable sites for community gardens.

Five samples per site were taken using a common garden trowel to remove 4-6" of topsoil. The five samples on each site were taken one from each of four corners, and one in the center. This was done to account for any variability within a site. The samples were labeled and bagged for future testing. In addition to these four sites, samples from other sites previously sampledwere added, for a total of 26 sites in East St. Louis. Testing for productivity and heavy level metal levels was performed by the Dept. of Nuclear Engineering. Click here to return to that section In addition, the studio performed two separate soil texture tests in order to gain a better understanding of the soil conditions in East St. Louis. The first was a field test which can easily be done by a homeowner. The second method requires lab equipment and is more accurate.

Field test:

The field test involved two proceedures; a test for grittiness to determine sand composition, and a ribbon test to determine clay content. The grittiness test is performed by placing a small portion of soil into the palm of the hand. Water is added until the soil is oversaturated, that is, until the soil is suspended in a pool of water. By rubbing the soil particles between a finger and the palm of the hand, an estimate of the percentage of "grittiness", or sand can be determined by feel. The more "grit" felt with the finger, the more sand. The ribbon test involves wetting a sample of soil in the palm of the hand as well. However, instead of overwetting the soil, the soil is moistened just enough to be able to knead the soil into a dough-like consistency. The ball of soil is then extruded between the thumb and forefinger in a "pinching" motion so that the soil extends out above the hand in a sort of "ribbon". How quickly and easily the soil begins to crack, break, and fall off during the extrusion is the indicator to the amount of clay content in the sample. As a general rule, the longer the sample holds the ribbon form, the greater the percentage of clay. A good solid ribbon usually indicates 40% or more clay content. Practiced users can reliably predict percent composition of sand and clay by these means (Hassett, 1994).

Finally, a rough calculation of organic content was made for each sample using the United States Soil Conservation Service's soil color guide to organic matter content. A chart of painted squares of varying shades of brown were used to compare each sample's color to determine a rough % of organic matter. The results of the grit, ribbon and organic matter field tests were used to get a general idea of the soil properites of the samples. A more accurate lab test was conducted afterwards with the help of University of Illinois Soils Professor John Hassett.

Lab procedures:

The lab proceedures for texture analysis involved the use of a hydrometer a glass, bouy-like instrument which floats in a liquid sample. The hydrometer is a device calibrated to measure the % of a material in suspension in a liquid. The equipment needed are; a hydrometer, mixing cups, malt-mixer, de-ionized water, calgon (liquid form), electronic scales, and graduated glass measuring cylinders (manual mixing may be substituted for the mixer). The steps involved are as follows:

NOTE: samples should be dry before proceeding

1) measure out as close to a 50g. sample as possible on the scales (do not include rocks, pebbles, clinkers, or large organic material) Note: weight of cup should be subtracted from the reading either electronically or by hand.
2) record the weight of the sample
3) add 20mg of calgon to the sample of soil in the cup
4) add de-ionized water to get the level in the cup about 1/2 full (about 350ml)
5) mix in mixer for 10 minutes to break up loose particles
6) pour mixed sample into measuring cylinder - wash out the cup with de-ionized water and pour into beaker- add enough de-ionized water to get the sample level even with the 1000ml measuring line on the beaker.
7) put stopper on measuring cylinder and shake 4-5 times (about 20 or so seconds)
8) put in hydrometer and get intitial reading for reference (use a few drops of ethyl alcohol to eliminate any foam on top of sample). The graduated hydrometer will indicate the number of grams of material suspended per liter of water.
9) take reading at 40 seconds after allowing the cylinder to stand. Since this is the time required for heavier sandparticles to drop out of suspension, the hydrometer measure of suspended material will equal the grams of silt and clay still suspended in the solution after the sand has dropped out.
10) subtract this reading from the original sample weight to get the grams of sand.
11) take another reading in 2 hours (this is time required for silt to drop out of suspension). At this time the only particles left in suspension are clay, so the hydrometer reading will equal the remaining grams of clay.
12) add the clay and sand weights together and subtract their sum from the total sample weight to get the grams of silt.
13) by dividing the grams of each particle by the total sample weight, percentages of each particle size can be attained.

The results of the studio's soil testing was informative. The majority of the soil samples seemed to have a high percentage of sand, some approaching 80% or more. Relatively few samples appeared to have been "ideal" garden soils of 40%sand, 40%silt, and 20% clay. A few soils represented a high clay component of 20-30 %. The conclusion is that these reflect an extreme variability of soil condition in East St. Louis. Not only were the percentages of particle size variable, the frequency of non-soil particles in the samples was disturbing. Aside from rocks and grass roots, the most abundant of these non-soil particles were "clinkers". "Clinkers" are rock-like particles that have formed from the residue of coal-fired furnaces used throughout East St. Louis in the past. Such particles were present in over half of the samples.

The presence of clinkers, the high variability in texture results, and the high possiblity of contamination, all indicate the need for a comprehensive soils testing program for the city of East St. Louis. Although this variability is to be expected from a river flood plain, with a history of intense human and industrial use, it suggests that there are no simple rules of thumb that can be used for reliable site selection for growing either for home or industrial-scale food production. All projects, whether they be small-scale gardens or large scale agricultural production, rely on the quality of the soil. The city, therefore, should concentrate effort on a soils initiative in order to identify areas of contamination, areas of poor soil, and areas of productive soil.

References

1. Alloway, B. J. ed. 1990. Heavy Metals in Soils. Blackie and Son Ltd., London, 339 p.
2. Colten, C. E. 1988. Historical Assesment of Hazardous Waste Management in Madison and St. Clair Counties, Illinois, 1890-1980. HWRIC RR-030.
3. Editor Basics. Fine Gardening. April, 1994.
4. Esguerra,L and Landsberger, S. 1994. Report on Determination of lead and heavy metals in soil samples around a Lead Smelter Plant and Environs in East S. Louis by Wavelenght Dispersive X-Ray Fluorescence.
5. Hanson, A., Samani, Z., Dwyer, B., Jacquez, R. 1992. Heap leaching as a solvent- extraction technique for remediation of metal-contaminated soils. ACS-sym-ser (American Chemical Society) 491 pp 108-121.
6. Hassett, John. Interview, Professor of Soils. University of Illinois. November 1994.
7. Kabat-Pendias, A. and Pendias, H., 1992. Trace Elements in Soils and Plants. CRC Press, Boca Raton, FL, 2nd. ed.,365 pp.
8. Lo, K.S.L., Yang, W.F., Lin, Y. C. 1992. Effect of organic matter on the specific absorption of heavy metals by soil. Pp 139-153 in: Toxicol. Environ. Chem. V 34 (2/4) Gordon and Breach Publishers.
9. Sauerbeck, D. R. 1991. Plant, element and soil properties governing uptake and availability of heavy metals derived from sewage sludge. Water, Air, and Soil Pollution 57-58: 227-237.
10. Sillanpaa, M. 1972. Trace elements in soils and agriculture. FAO Soils Bulletin 17.

Document author(s) : LA 437/465 Fall 1995
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