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Literature Review -Micronutrient Copper as a Potential Pollutant I Background A listing of heavy metals typically includes Cadmium, Cobalt, Chromium, Copper, Iron, Mercury, Manganese, Molybdenum, Lead and Zinc Eighteen elements are considered essential to plant growth Macronutrients include Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg) and Sulfer (S) Nine elements are required in such small amounts that they are called micronutrients or trace elements Iron (Fe), Manganese (Mn), Zinc (Zn), Copper (Cu), Boron (B), Molybdenum (Mo), Nickel (Ni), Cobalt (Co), and Clorine (Cl) are commonly listed Many crops are fertilized with one or more trace elements to maximize yields Micronutrients are increasingly being considered as a pollutant In general, the levels of these elements is increasing in soil due to atmospheric deposition; land applications of sludge, manure, and smelter waste; and long term use of pesticides The determination of a phytotoxicity level for a specific crop is not a simple task Soil properties have a strong influence on crop uptake (5,29) II Federal Regulations The maximum cumulative loading rates for heavy metals allowed under the original EPA guidelines were relatively low and varied with the cation exchange of the soil (pH ≥6.5) The Cu loading rate was set at 560 kg/ha (1,2,24) Subsequent research demonstrated that higher rates of Cu could be applied with no adverse effect on plant growth (1,14,26) Consequently, the maximum loading rate was revised to 1500kg/ha Part 503 -STANDARDS FOR THE USE OR DISPOSAL OF SEWAGE SLUDGE (31) • • • • • • • • • Assessments made regarding bio-solid use/disposal practices including: Land application, surface disposal, and incineration Procedures established by National Academy of Sciences (Ch.1:2-5) Good discussion of plant uptake and response to metals and associated soil condition.(Ch.1:36-40) Criteria used to establish "pollutants of concern", assessment methodologies, and risk-based pollution limits Copper is included (Ch.2, pages 7-18) Public and peer review, proposals, and revisions made (Ch.2:20-29) Greater reliance on field studies and less on greenhouse studies (Ch.2:28) Issues regarding highly exposed vs most exposed individual assessments of potential hazard (Ch.3:33) Final rule: pot/salt studies "greatly overestimate" phytotoxicity and bioavailability of metal pollutants in biosolids References are sited Good plant uptake and plant response to metals discussion (Ch3:36-40) Additional considerations that reduce, or increase, the plants risk to metal toxicity Ch.3:43-44 Phytotoxicity criteria, thresholds (PT50, PT25), experimental procedures and results related Cu loading rates by "calculation approach" is 2500 kg/ha and by "probability approach" was 1500kg/ha so the conservative 1500 kg/ha was designated the appropriate rate for Cu loading Reference is made to a comprehensive review of plant metal concentration data and yields from bio-solids field studies including all data reflecting various soil types and bio-solid sources Excellent summary of multiple research studies (Ch.3:48-49) Risk assessment Algorithms for human adult/child and for animals for ingestion of crops grown on bio-solid amended soils Ch.4: 62-70 and land application pollutant limits by exposure pathways Ch 4:81-83 Pollutant limits for land application and types of land application are described Cu is included as a pollutant but is excluded from the surface disposal regulation for reasons explained (Ch.5:99-102) Copper is used as an example for derivation of pollutant concentration limits (Ch.5:101) Rationale for associating specific management practices with Part 503 Rule is listed in tabular format (Ch.5:105-106) III Literature Review A Soil Considerations • Copper Sources: Cu Lit Review J Davis 11/09/04 ♦ Inorganic sources of Cu Weathered minerals and resultant sulfides, hydroxyl carbonates, oxides, and commercial fertilizers (5,29) Some Cu Fertilizers Copper metal Copper nitrate Copper acetate Copper oxalate Copper oxychloride Copper ammonium phosphate Copper Sulfates (general formula) Copper sulfate (Chalcanthite) Copper sulfate (monohydrate) Formulas Cu Cu(NO3)2•3H2O Cu(C2H3O2)2•H2O CuC2O4•0.5H2O CuCl2•2CuO•4H2O Cu(NH4)PO4•H2O CuSO4•3Cu(OH)2 CuSO4•5H2O CuSO4•H2O Chelates Na2Cu EDTA NaCu HEDTA Elemental Cu % 100 32 40 52 32 13-53 25 35 13 Solubility (water) Insoluble Soluble Slightly Insoluble Insoluble Insoluble Insoluble Soluble Soluble Soluble Soluble Adapted from Gilkes (12) Trade and other names: Agritox, Basicap, BSC Copper Fungicide, CP Basic Sulfate and Tri-Basic Copper Sulfate The pentahydrate form (CuSO4•5H2O) is called bluestone, blue vitriol, Slazburg vitriol, Roman vitriol, and blue copperas Bordeaux mixture is a combination of hydrated lime and copper sulfate Copper sulfate is often found in combination with other pesticides (32) Regulatory status: Copper sulfate is classed as a General Use Pesticide (GUP) by the EPA Copper sulfate is toxicity class I-highly toxic The label bears the warning Danger-Poison because of its potentially harmful effects on some endangered aquatic species, surface water use may require a permit in some areas (32) Introduction: Copper sulfate is a fungicide used to control bacterial and fungal diseases of fruit, vegetable, nut and field crops These diseases include mildew, leaf spots, blights, and apple scab It is used as a protective fungicide (Bordeaux mixture) for leaf application and seed treatment It is also used as an algaecide and herbicide, and to kill slugs and snails in irrigation and municipal water treatment systems It has been used to control dutch elm disease It is available as a dust, wettable powder, or liquid concentrate (32) Cu Lit Review J Davis 11/09/04 ♦ Organic sources of Cu Manure Poultry (broiler) Poultry (layer)-no bedding Dairy cow Swine Sheep Horse Feed lot cattle Young rye green Spoiled legume hay Municipal waste compost Sewage sludge Wood wastes (g/Mg dry wgt) (g/Mg dry wgt) a 473f 155e 30h 150g 172 30a 150b 30a 25a 2c 5a 10a 280d 500a 50a a Brady and Weil (5) p.629 after (5) cited from Zublena, et al.(1993) c after (5) cited from Eghball and Power (1994) d after (5) cited from He, et al.(1995) e after Miller in (29) cited from Edwards and Daniel (1992) and Sims and Wolf (1994) f after Miller in (29) cited from Edwards and Daniel (19920 and Brady and Weil (1996) g after Miller in (29) cited from Choudhary et al (1996) and Brady and Weil (1996) h after Miller in (29) cited from Brady and Weil (1996) b Cu Lit Review J Davis 11/09/04 • Natural (Background) levels of Copper in Soils Holmgren et al (16) and Huang (17) evaluated previously published data for concentrations of heavy metals in soil samples collected from around the world Copper reported as geometric means for air dried soil samples [adapted from Holmgren et al., (16)] mg kg-1 3045 U.S samples 1218 U.S samples 2276 England samples 654 Wales samples World samples 18 17 18 16 59.8 (Holmgren et al., 1993) (Shacklette et al., 1984) (McGrath, 1986) (Davies et al., 1985) (Ure et.al., 1982) Copper reported as arithmetic means for air dried soil samples [Holmgren et.al., (16)] mg kg-1 Typical U.S soil 50 (Sposito et al., 1984) Minnesota soils 26 (Pierce et al., 1982) 237 Ohio soils 19 (Logan et.al., 1983 296 Ontario soils 25.4 (Frank et.al., 1976) Considering 3045 U.S soil samples LRR reported (geometric means) [Holmgren et.al., (16)] mg kg-1 Mineral Soils K -Northern Lake States L -Lake States N -East and Central Farming R -Northeastern Forage S -Northern Atlantic Slope All Mineral Soils 15.4 18.2 34 13.5 15.6 mg kg- Organic Soils K -Northern Lake States L -Lake States R -Northeastern Forage All Organic Soils 59.6 84.7 149 86.9 Considering 3045 U.S soil samples by: (geometric means) [Holmgren (16)] soil order Alfisol Aridisol Entisol Histosol Inceptisol Mollisol Spodisol Ultisol Vertisol all orders mg kg-1 10.9 25 21.1 183.2 28.4 19.1 48.3 6.2 48.5 18.3 surface texture Loamy Sand Sandy Loam Fine Sandy Loam Silt Loam Loam Silty Clay Loam Clay Clay Loam Silty Clay Organic muck Organic sapric All "textures" mg kg-1 10.8 10.3 18.1 18.6 28.7 37.6 22.7 33.6 75.8 97.9 18.3 State mg kg- (mineral soils) MD ME NJ NY PA 7.7 64.8 11.0 27.0 28.3 It has been observed that element concentrations in natural materials are distributed in a log normal pattern Therefore, the geometric mean gives a better estimate of the most probable value in large data sets (17) Geometric mean is the antilog of mean for log-transformed data (16) The arithmetic mean is used for smaller data sets or in cases where the soils are closely related (17) Cu Lit Review J Davis 11/09/04 Huang evaluates the Holmgren et al., (17) data plus an additional 5692 samples from England and Wales (McGrath and Loveland,1992) U.S Agricultural Soils Element Copper [adapted from Huang (17)] England and Wales Topsoils (0-15 cm) Geometric mean (µg g-1) Range Geometric mean (µg g-1) 18 < 0.6-495 23.1 Range 1.2-1,510 Huang sites earlier work relating mean concentrations of metals from mainland China by soil order (Chang et al., 1991) [adapted from Huang (17)] Soil order Lithosols Cold Highland Soils Mollisols Aridisols Inceptisols Alfisols Ultisols Oxisols Vertisols Entisols ã Geometric means Cu (àg g-1) 26.5 23.8 10 21.7 21.8 15.1 17.8 10.9 19.6 22.2 Excess Cu in soils reported Merry et al (21) surveyed the distribution of metals in 98 soils from orchards in Australia and Tasmania and found copper, lead, and arsenic concentrations 25-35 times greater than background levels Frank et al (11) studied apple, cherry, peach orchard and vineyard soils treated with Cu-salts over an 80 year period in Ontario, Canada The recommended use of 38 organic and inorganic pesticides used between 1892 and 1975 resulted in the elevation of copper levels over normal background in soils Crop management tactics, pesticides used, and duration of application influenced the accumulation of copper in the study area A high percentage of apple orchard soils tested had significantly elevated Cu levels from 21ppm to 63ppm over a 70 years period • Sludges Generally accepted concepts: Research utilizing sludges have established that they are extremely variable in composition and may contain high levels of Zn, Cd, Cu, Ni, and Pb Sludge composition, application rates, pH, and CEC are important factors in plant uptake of metals Immediately post application Cu uptake is enhanced then reduces as the organics stabilize This is probably due to acidifying consequence of organic decomposition and perhaps a "chelating effect" rendering Cu more available for uptake • Feed additives and Cu manure content Copper is added to poultry and swine diets to increase growth rate and promote feed efficiency On a dry matter basis: Kingery et al.(18) reported an average of 470 mg kg-1 Cu in poultry litter, and Anderson et al.(1) 1316 mg kg-1 Cu in swine manure when swine were supplemented with an average of 251 mg kg-1 Cu as CuSO4 µg g-1 and mg kg-1 are equivalent expressions Cu Lit Review J Davis 11/09/04 Soil Organic Matter and Chelation Generally accepted concepts: Soil organic matter Consists of a wide range of substances, including living organisms, remains of organisms, and organic compounds produced by metabolism in the soil The remains of plants, animals, and microorganisms are continuously broken down in the soil and new substances are synthesized by other microorganisms Organic matter comprises only a small fraction of the mass of a typical soil By weight, typical welldrained mineral surface soils contain from to percent organic matter Humus is a collection of organic compounds that accumulate because they are relatively resistant to decay The surface charges of humus attract and hold nutrient ions Small amounts of humus can dramatically increase the retention and exchange of nutrients in soils (5,29) Chelates Are organic compounds that are capable of bonding with positively charged micronutrients (like Cu2+ and Cu(OH)+ ) These compounds may be synthesized by plant roots and released into surrounding soil, may be present in soil humus, or may be synthetic compounds added to enhance micronutrient availability Many chelating compounds occur naturally in the soil and numerous synthetics are available The complexed form is protected from reaction with inorganic soil constituents If soluble the complex is available for plant uptake, if insoluble availability is decreased Two chelated metal uptake mechanisms are recognized: Dicots (cucumber, peanuts)-root tissue produces strong reducing agent (NADPH) that strips the chelate from the metal and allows the reduced metal entry into the root Monocots (corn, wheat) accept the entire chelate complex into the root and then remove the metal, reduce it, then expel the chelate to the soil (5) Soil metal studies often utilize chemical extractants such as EDTA, DTPA and CaCl2 to evaluate concentrations McBride (19) cites pertinent research and relates that "metals extracted by the chelating agents, EDTA and DTPA have been reported to correlate well with uptake of metals into plant tops of a number of crops Metals extracted by these agents, are largely in exchangeable, organically-complexed, and carbonate forms, and tend to correlate with metal uptake by plants It should not be assumed that these chelating agents actually measure availability" • Organic matter protection debate There are several schools of thought regarding the long-term binding, and release, of potentially dangerous metals by the organic fraction of soils "Time Bomb Theory" suggests that the organic matter portion of bio-solids binds metals thus reducing their bioavailability However, as soon as the organic matter degrades all accumulated metals are rendered available (8,19,31) The EPA response: "Bio-solids are typically about 50% organic and 50% inorganic Much of the binding that occurs is attributable to the inorganic part of bio-solids, namely the oxides if iron, aluminum, and manganese, and also phosphate compounds The binding effect persists even after the bio-solids have been applied to soils, except at very low pH situations Field data suggests that these compounds remain stable for hundreds of years if pH doesn't drop drastically The bio-solid has degraded long ago (Beckett et al., 1979; Johnson et al.,1983)" (31) Chaney and Ryan (8) concluded that "all evidence available indicates that the specific metal absorption capacity added with sludge will persist as long as the heavy metals of concern persist in the soil" They reject the "time bomb theory" McBride (19) evaluates the concept that sludge decomposition products can maintain low heavy metal solubilities for long, perhaps decades, periods of time He labels the concept the "sludge protection theory" McBride considers EPA 503 regulations too permissive for most metals because they permit 10 to >100 times the current background levels for metals in most soils He notes that while EPA loading limits have not been Cu Lit Review J Davis 11/09/04 reached in field experiments, except for a few cases and a few metals, it has yet to be proven that these EPA levels are safe Further, mineralization of organic matter in sludge could release metals in more soluble forms There is general agreement that a fraction of the organic matter resists decomposition and could protect against metal uptake for decades (4,8,19), but without additions of sludge the soil would eventually return to near original organic matter levels and residual metals would have to be rendered unavailable by the inorganic (mineral) fraction of the soil or be available for uptake McBride (19) evaluated long-term orchard studies where soils became increasingly polluted with Cu due to pesticide applications and concluded that "decades or even centuries of aging pollutants added in inorganic form to soils is insufficient to convert them to unavailable forms Consequently, the EPA heavy metal limits (1500 kg ha-1) can be considered safe only if materials in the sludge itself permanently immobilize most of the metals • Organic half-life ♦ The half-life of organic decomposition has been estimated at approximately 10 years (4), but may overestimate decomposition rate over a period of several decades (30) While some of the organic complexing ability is lost over several decades, a portion endures for an extended period of time.(4,30) Bell et al (4) reported that organic additions from sludge application may still be significant 10 years after application The study sites European data suggesting a one-half of the organics added with sludge or farmyard manure was still present in the soil after 10 years A similar rate of organic loss could be expected in the Mid-Atlantic states Organic matter may have significant impact on Cu availability and many studies have shown the greater ability of Cu to form complexes with organic matter than Zn or Mn • pH ♦ Generally accepted concepts: Micronutrients, including Cu, are most soluble and available under acid conditions In very acid conditions one or more trace elements may become toxic to common plants At higher pH the nutrients are changed to insoluble compounds that are "fixed" and unavailable for plant uptake The exact pH at which micronutrients become "fixed" varies with specific element and valent state In soils, Cu is found in more than one valent state Ion species Cu2+ dominates under acid conditions and Cu(OH)+ at higher pH In general, high pH values favor oxidation (higher valence), and lower pH the reduced species (lower valence) The changes in valence are usually associated with decomposition of organic matter by microorganisms Cu2+ is much less soluble than Cu(OH)+.(5,29) Most micronutrient toxicity problems can be avoided by maintaining a pH at neutral or above Draining a soil is also usually beneficial , since oxidized forms are usually less soluble and less available for plant uptake than are the reduced forms (Cr is an exception)(5) It is well established that pH is an important factor in the availability and uptake of Cu Merry et al (23) Using metal contaminated soils studied the effects of soil pH on uptake of Cu by radish and beet in a greenhouse study They noted that Cu concentrations in the plant decreased with increasing soil pH and that the effect was more marked in the more contaminated soils Further, soils behaved similarly no matter what the source of contaminants, but freshly applied Cu appeared to be more deleterious to plants, especially on poorly buffered soils, then are the same elements accumulated over a long period of time Cavallaro et al.(7) found that sorption and fixation of Cu increased rapidly above pH and respectively Concluded that acid soil clays show highly pH dependent sorption of Cu Microcrystalline oxides seem to be most important for Cu sorption • Soil texture, clay type and humus ♦ Generally accepted concepts: Plant nutrients are released from colloidal surfaces of clay and humus to the soil solution CEC (or ECEC) is a measure of the number of charged sites available for capture, or release of nutrients All soil particles, organic or inorganic, exhibit the surface charges associated with OH groups, charges that are largely pH Cu Lit Review J Davis 11/09/04 dependent Most of the charges associated with humus, 1:1 -type clays, oxides of iron and aluminum, and allophane are of this type In the case of 2:1-type clays a large number of charges are associated with isomorphic substitution These charges are not pH dependent and are generally termed permanent charges The CEC of most soils increases with pH To obtain a measure of maximum retentive capacity, the CEC is commonly determined at pH or above At neutral, or slightly alkaline pH, the CEC reflects most pH dependent and permanent charges (5,29) Soil texture is significant because of the relative amount surface area available for adsorption of charged particles including water The external surface of g of colloidal clay is at least 1000 time that of 1g of coarse sand In general, finer textured soils have a higher exchange capacity associated with the mineral fraction and are therefore less prone to radical changes in pH then are coarser textured soils (5) The resistance to pH change is referred to as "buffering" • Micronutrient balance: ♦ Generally accepted concepts: Plants vary in the amount and species of trace elements required for productive growth Some plant enzymatic and biochemical reactions require more than one micronutrient and some are poisoned by the presence of a second nutrient Some examples: Mn and Mo are needed for assimilation of nitrates by most plants, the use of Cu and K is dependent on a balance between the two, and Cu utilization is favored by adequate Mn which in some plants is assimilated only if Zn is present in sufficient amounts (5) "Antagonistic effects" - Some examples: Iron deficiency is encouraged by an excess of zinc, manganese, and copper; excess phosphate may encourage a deficiency in zinc, iron and copper; heavy N fertilization intensifies copper deficiency and excess copper or sulfate may adversely affect utilization of molybdenum Some antagonistic effects are utilized to reduce toxicities For example, copper toxicity of citrus groves caused by residual Cu from insecticide sprays may be reduced by adding Iron or phosphate fertilizers (5) "Synergistic effects" -Example: Boron at the root surface increases the uptake of Cu McBride (19)- "Because heavy metal toxicity to roots can be somewhat additive and even synergistic when several metals are present (Hassett et al 1976; Wallace and Berry, 1989), soils approaching the USEPA limits for several of the phytotoxic elements may show yield reductions at lower concentrations than expected if a single element is at an elevated concentration For this reason, there has been debate about the extent to which the phytotoxic effects of metals such as Zn, Cu, and Ni are additive and whether individual metal limits should be lowered to reflect this additivity (Saunders et al 1986, Davis and Carlton-Smith, 1984) Antagonism between metals such as Cd, Zn, Mn, and Cu can reduce root and tip growth as well as reduce micronutrient content in the plants (Jalil et al., 1993), Mn deficiency on old sludge sites (Trocme et al., 1950), and deficiencies in plants associated w/ high Zn and Cu (Leeper 1978)" • Organic soils - micronutrient contents depend on the amount and extent of washing and leaching into the bog area as the soil was formed The ability of organic matter to bind copper may lead to deficiencies In comparison to other trace elements, Cu is especially tightly bound to organic matter (humus) and thus less available for plant uptake Cu availability may be very low in organic soils (Histosols) If drained, the rapid mineralization of the organics and associated reduced pH may enhance Cu uptake (5) ♦ Soil erosion -removes organic matter and thus reduces the soils ability to bind copper in topsoil Exposed subsoil horizons may have lower pHs rendering Cu more available for plant uptake • Copper mobility Researchers have established that Cu accumulates mainly in the surface soils with much lower accumulations below 15 cm (11,21,24,28) Long-term management practices lead to deeper accumulations: 45 cm from broiler litter (18), 30 cm after fungicides on citrus (28), and 60 cm after sludge on cropland (24) Copper leaching is not considered an important process in the soil because Cu is strongly absorbed by oxide minerals and by organic matter (21,23), but movement of metals in soils has long been known to be associated with chelation with soluble organic compounds in a process sometimes referred to as cheluviation (18) Cu Lit Review J Davis 11/09/04 B Crop Response/plant uptake/phytotoxicity McBride (19) summarizes problems in quantifying organic protection and Cu uptake: "There may not be a strong correlation between metal solubility (or availability to roots) and the concentration in plant tops This depends on many factors affecting translocation, including species and cultivar of plant, environmental conditions, and competing ions Although the edible portion of the plant may contain acceptably low concentrations of toxic metals, the true extent of metal bioavailability and toxicity to roots and soil microbes could be underestimated" In other words, Cu loaded at high rates, and present in the soil in high concentrations, may not accumulate in aerial tissues due to factors like the plant's translocation efficiency Potentially toxic levels of soil Cu may, due to multiple factors, not have a detectable impact on growing plants In general, soil extractable Cu has not correlated well with the amount of Cu found in crop tissues (21,23,24,25) Levels of Cu thought to be toxic did not produce plant tissue toxicity symptoms (22) The amount of Cu in tissues necessary to cause toxicity symptoms in plants is independent of growing conditions (10) Soil temperature was found to be an important factor in uptake of Cu (22) Minnich et al (25) relate that "In studies where excess Cu is supplied and concentrations in both roots and shoots are determined, roots accumulate Cu and only a small fraction of the absorbed Cu is translocated to the shoots (Dragun et al, 1976; Jarvis and Whitehead, 1981; Struckmyer et al., 1969; Taylor and Fox, 1985)" Becket et al (3) reported that even after 12 months the fractions" available" Cu added in sludges were greater than those native in the soil, but their availabilities to young barley decreased over that period The ratio of available/total Cu added to sludge treated soils was 0.8 for Cu Clearly, then the amounts that can be taken up/amount present have diminished with time (no difference with sludge types) McBride (19) "Availability of sludge-borne metals to plants is generally the highest immediately following application of sludge to the soil, diminishing thereafter (Bidwell and Dowdy,1987; Chang et al., 1987a; Hinesly et al., 1997) The cause of the initial high bioavailability may be, at least in part, rapid organic matter decomposition that produces soluble organic carriers of metals (Alloway and Jackson, 1991; Chaney and Ryan, 1993; Minnich et al., 1987) Organic matter appears to have quite different roles in controlling trace metal uptake by plants, depending upon whether it is soluble (fluvic acid) or insoluble (humic acid) Insoluble organic matter very effectively inhibits uptake of metal cations such as Cu+2 which bind strongly to organic matter and are thereby prevented from diffusing to roots Conversely, soluble organics raise the carrying capacity of soil solutions for Cu+2 at any particular pH by forming soluble metal-organic complexes (McBride 1994) Because the plant is able to extract trace metals from these complexes once they diffuse to the root (Nor and Cheng, 1986), the high level of soluble organics found in soils recently amended with sludge would promote absorption of trace metals by roots With time, organic decomposition rates and levels of soluble organics diminish, total dissolved metals presumably stabilize at lower values, and bioavailability is reduced" Crops considered to have high Cu requirement or low uptake efficiency : Wheat, corn, onions, citrus, lettuce, carrots and crops considered to have low Cu requirement or high uptake efficiency: Beans, Potato, peas, pasture grasses, pines.(5) Numerous studies have focused on accumulations of copper, and other metals, in soils affected by longstone fruit orchards, vineyards, and on vegetables for about 100 years Cu Lit Review J Davis 11/09/04 In Australia, Merry et al (22) reported unusually high copper concentrations in plant tissues of sampled pasture species (20-60mg/kg) and was concerned about the risk to grazing ruminant animals Additionally, the study compared tissue concentrations of clover, beet and radish plants grown on Cu contaminated sites with the same plants grown on uncontaminated sites Plants grown on contaminated sites contained Cu levels that exceeded normal values and would likely have been in the toxic range for the plant However, no evidence of chlorosis, stunting or other symptoms of Cu toxicity were observed though they suspected that yield reductions did occur Mean Cu concentrations of 31±11mg/kg were recorded and literature was sited that established the plant toxic threshold at 20mg/kg Reuther and Smith (28) studied Florida citrus, chlorosis, stunting and yield reduction in orchards that traditionally yielded well High concentrations of copper in the 0-6 inches zone correlated well with the age orchards studied A 40 years old orchard with pH of 4.9 had 186ppm Cu compared to 0.9ppm Cu at pH 5.2 for a virgin soil The study concluded that the level of Cu in many mature orchards on acid, sandy soil was approaching a point where foliage chlorosis and damage to normal root development would negatively impact yield McBride (19) summarizes the collective experience with Cu-salts applied to orchards, vineyards, and other agricultural sites and suggests that total soil Cu in the range of several hundred mg kg-1 caused phytotoxicity in some crops (22, Lexmond, 1980), but not in all (Payne, ref 26) As the concentration of Cu in orchard soil increases with time from cumulative application, a larger fraction of the total Cu can be extracted by EDTA (Dickinson, 1988) suggesting increased conversion to soluble forms that are available for plant uptake The fact that EDTA, a chelating agent, has rendered adsorbed Cu available for extraction suggests increased availability for plant uptake Thus, increased soil-Cu is rendered soluble and thus readily bioavailable Davis et al (10) found that though the concentration of Cu in tissue of young barley varies with growing conditions, the minimum concentration of Cu in plant tissue necessary to cause plant toxic reactions are relatively independent on growing conditions (2,10) Increases in tissue concentration above critical (Tc) were considered toxic and dry matter yield reduction would be predicted [adapted from Davis (10)] Critical Concentrations for Cu (ppm dry matter) Barley To 11 Lettuce Tc To 14-25 10 median:19 Rape Tc To 17-21 median:21 Ryegrass Tc To 15-22 11 median:16 Wheat Tc To 21 11 Tc 18 Tc =critical content of plant tissue and To = normal concentration in plant tissue Minnich et al., (25) compared extracted soil solution Cu++ with copper accumulation in young snapbeans Sludge and Cu-salts were used to supply Cu, and the pH was maintained in the 5.0-5.5 range Sludge treatments resulted in non-linear relationships between soil-Cu and Cu-tissue accumulation Higher shoot Cu occurred with Cu-salt treatments, but sludge delivered higher root-Cu accumulations at lower Cu-concentrations in the soil "This probably reflects the superior ability of the sludge to replenish or maintain the Cu supply in soil solution" Root toxicity occurred at shoot-Cu levels of 30 mg kg-1 which equates to a salt addition of 300 mg kg-1 (or 600 kg ha-1) Significant conclusions: Sludge replenishes Cu faster than the Cu-salts; plants absorb chelated-Cu as well as free Cu++ ions; singularly, concentration measurements not define plant available Cu in soil; additional study is needed to understand replenishment and interaction factors before accurate predictions of Cu uptake can be made; Cu concentration in shoot tissue increased linearly with Cu concentration of sludge; root Cu content is influenced not only by sludge Cu content, but also by the proportion of sludge in the growth media; the increased root-Cu must reflect either a more labile Cu-Source was present in the composted sludge or a redistribution of Cu from the high-Cu sludge to more labile forms in presence of increased additions of sludge Cu Lit Review J Davis 10 11/09/04 McBride and Bouldin (20) studied long-term copper reactions on calcareous soils and noted that although the solubility and chemical extractability of metals in sewage sludge might be quite low initially, various reactions such as oxidation of metal sulfides and organic matter mineralization could serve to increase biological activity of metals in soils over long time periods Evidence suggests that there is a tendency for some heavy metals to transfer into an organically complexed form This is particularly true for Cu and Pb as indicated by the large fracton of the total Cu and Pb that can be extracted by EDTA and the accumulation of these metals in the surface organic rich layer of soils The long-term reaction of very high levels of Cu with a calcareous soil failed to convert the soluble metal into a form unavailable to plants, as evidenced by what appeared to be Cu toxicity in corn Chemical extraction revealed that much of the total Cu was present in a non-exchangeable form readily dissolved by the chelating agent Greater than 95% of the Cu in soil solution was complexed, probably by soluble organics Heckman et al., (14) concluded that sludge composition and soil pH can have a substantial influence on soybean uptake of metal uptake for at least years after the initial sludge application The rate of sludge application strongly influenced the metal content of soybean Plant tissue concentrations of Cu (and other metals) exhibited significant linear increases over the rates of sludge application Payne et al (26) reported similar findings post 20 years of applying CuSo4 on corn Excessive loading rates did not reduce grain or silage yields and Cu concentrations remained at normal levels in grain and leaf tissues across all treatments Anderson et al (1) evaluated corn yield response to high Cu levels from Cu-rich swine manure and CuSO4 applications over an eleven year period At loading rates of about 600 mg kg-1 Cu resulted in no reduction in yield from either Cu-manure or CuSO4 sources This loading rate did not increase Cu concentrations in corn ear leaves or in corn grain Additional findings: Application of Cu-manure and CuSO4 increased extractable Cu from on-site soils; Increases in extractable soil-Cu did not correlate with ear leaf concentrations; This may be due Cu uptake by roots with a low amount of Cu translocation from roots to shoots Cu Lit Review J Davis 11 11/09/04 C Soil flora and fauna Mycorrhizae appear to protect plants from excessive uptake of micronutrients Seedlings of birch, pine, and spruce are able to grow well on sites contaminated by Zn, Cu, Ni, and Al only if the roots are sheathed by ectomycorrhizae (5) Rhee (27) evaluated Cu-accumulation in earthworms after long-term applications of Cu-hog manure (10 years) to pasture Worms assessed included: A caliginosa, A chlorotica, A longa, and L rubellus No relationship was found between Cu-contents of the soil and worm numbers Nevertheless, there was an obvious relationship between Soil-Cu and Cu levels found in evaluated earthworms [adapted from Rhee (27)] Cu-Soil concentration 109.7 98.9 43.7 26.8 25.5 25.4 17.6 14.4 6.7 (ppm dry weight) Cu-Worms concentration 63 39 20 19 19 16 14 12 10 (ppm dry weight) Worms densities/m2 12 -239 45 15 64 76 17 84 _ Helmke et al (15) evaluated the suitability of using earthworms to monitor the bioavailability of metals in soils, and to determine the effects of land application of sewage sludge on the concentrations of metals in earthworms Worm-Cu and worm cast-Cu increased with increasing rates of sludge application Cu Concentrations in earthworms and their casts [adapted from Helmke et al., (ZA)] 0-metric tons/ha manure 15-metric tons/ha manure 1971 1971 1973 1971 1972 1973 worms | casts worms | casts worms | casts worms | casts worms | casts worms | casts 8.8 10.5 9.4 9.5 10.6 12 21.2 11.8 18.9 8.3 14.1 30-metric tons/ha manure 60-metric tons/ha manure 1971 1972 1973 1971 1972 1973 worms | casts worms | casts worms | casts worms | casts worms | casts worms | casts 10.0 18.4 13.7 26.3 21.7 36.1 13.3 44.0 12.0 36.9 8.0 9.0 All sludge treatments involved single applications of anaerobically digested liquid sewage sludge Hartenstein et al (13) reported that earthworms (Eisenia foetida) could feed on untreated activated sludges with up to 1500 ppm Cu for several months without harm The addition of 2,500 ppm Cu as CuSo4 to activated sludge resulted in 100% mortality within week Additional findings: passage of sludge through the gut did not result in increased extractable Cu (0.1N HCl); Cu may accumulate or concentrate in the earthworm Cu Lit Review J Davis 12 11/09/04 COPPER LITERATURE CITED Anderson, M.A., J.R McKenna, D.C Martens, S.J Donohue, E.T Kornegay, and M.D Lindemann 1991 Long-term effecs of copper rich swine manure application on corn production Commun Soil Sci Plant Anal 22 (9&10) p 993-1002 Beckett P.H.T., and R.D Davis.1977 Upper critical levels of toxic elements in plants New-Phytol 79 (1) : 95-106 [NAL-450-N42] Beckett, P.H.T., R.D Davis, A F Milward, and P Brindley 1977 A comparison of the effect of different sewage sludges on young barley Plant-Soil 48 (1) p 129-141 [NAL-450-P696] Bell, P.F., B.R James, and R L Chaney 1991 Heavy metal extractability in long-term sewage sludge and metal salt-amended soils J Envir Qual v 20 (2) p 481-486 [NAL-QH540.J6] Brady, N.C., and R.R Weil 1999 The Nature and Properties of Soils, 12th Ed Prentice Hall, Upper Saddle River, NJ General reference CAST (Council for Agricultural Science and Technology), Report no 64 1976 Application of sewage sludge to cropland: appraisal of potential hazards of the heavy metals to plants and animals EPA 430/9-76-013 [NAL s22.c6] Cavallaro, N., and M.B McBride.1984 Zinc and copper sorption and fixation by and acid soil clay: Effect of selective dissolutions Soil Sci Soc Am J v 48 (5) p 1050-1054 [NAL-56.9-SQ3] Chaney, Rufus L., and James A Ryan 1993 Heavy metals and toxic organic pollutants in MSW-composts: Research results in phytoavailability, bioavailability, fate, etc In Science and Engineering of Composting: Design, Environmental, Microbiological and Utilization Aspects A Hoitink and H Keener, eds., Worthington, OH Renaissance Publications p 451-506 Chang, A., T C Granato, and A Page 1992 A methodology for establishing phytotoxicity criteria for chromium, copper, nickel, and zinc in agricultural land application of municipal sewage sludges J Environ Qual 21:521-536 [NAL-QH540.J6] 10 Davis, R.D., and P.H.T Beckett 1978 Upper critical levels of toxic elements in plants II Critical levels of copper in young barley, wheat, rape, lettuce and ryegrass, and of nickel and zinc in young barley and ryegrass New-Phytol 80 (1) : 23-32 [NAL-450-N42] 11 Frank, R., H.E Braun, K Ishida, and P Suda.1976 Persistent organic and inorganic pesticide residues in orchard soils and vineyards of southern Ontario Can J Soil Sci 56:463-484 [NAL-56.8 C162] 12 Gilkes, R.J 1981.Behavior of Cu additives-Fertilizers p.97-115 In J.F Loneragan et al (ed.) Copper in soils and plants Academic Press, New York, New York [NAL-QD181.C9C6] 13 Hartenstein, R., E.F Neuhauser, and J Collier 1980 Accumulation of heavy metals in the earthworm Eisenia foetida J Environ Qual (1) p 23-26 [NAL-QH540.J6] 14 Heckman, J.R., J.S Angle, and R L Chaney 1987 Residual effects of sewage sludge on soybeans: I Accumulation of heavy metals J Environ Qual 16: (2) p.113-117 [NAL-QH540.J6] 15 Helmke, P.A., W.P Robarge, R.L Korotev, and P.J Schomberg.1979 Effects of soil-applied sewage sludge on concentrations of elements in earthworms J Environ Qual 8: (3) p 322-327 [NAL-QH540.J6] 16 Holmgren, G., M.Meyer, R.Chaney, and R.Daniels 1993 Cadmium, lead, zinc, copper, and nickel in agricultural soils of the United State of America J Environ Qual 22:335-348 [NAL-QH540.J6] 17 Huang, X 1999 Soil Chemistry p B14-B24 In Malcolm E Sumner (ed.) Handbook of Soil Science, CRC Press, Boca Raton, FL 2000 18 Kingery, W.L., C.W Wood, D.P Delaney, J.C Williams, and G.L Mullins 1992 Inpact of long-term application of broiler litter on environmentally related soil properties J Environ Qual 23: 139-147 [NALQH540.J6] 19 McBride, M.B., 1994 Toxic metal accumulation from agricultural use of sludge: Are USEPA regulations protective? J Environ Qual 24:5-18 [NAL-QH540.J6] 20 McBride, M.B., and D.R Bouldin 1984 Long-term reactions of copper (II) in a contaminated calcareous soil J Soil Sci Soc Am v 48 (1) p.56-59 [NAL-56.9-SQ3] 21 Merry, R.H., K.G Tiller, and A,M Alston 1986 Accumulation of copper, lead, and arsenic in some Australian orchard soils Aust J Soil Res v 21 (4) p 549-561 [NAL-56.8-AU7] 22 Merry, R.H., K.G Tiller, and A.M Alston 1986 The effects of contamination of soil with copper, lead and arsenic on the growth and composition of plants I Effects of season, genotype, soil temperature and fertilizers Plant-Soil v 91 (1) p 115-128 [NAL-450-P696] Cu Lit Review J Davis 13 11/09/04 23 Merry, R.H., K.G Tiller, and A.M Alston 1986 The effects of soil contamination with copper, lead and arsenic on the growth and composition of plants II Effects of source of contamination, varying soil pH, and prior waterlogging Plant-Soil v 95 (2) p 255-269 [NAL-450-P696] 24 Miner, G.S., R Gutierrez, and L.D King 1996 Soil factors affecting plant concentrations of cadmium, copper, and zinc on sludge-amended soils J Environ Qual 26:989-994 (1997) [NAL-QH540.J6] 25 Minnich, M.M., M.B McBride, and R.L Chaney 1987 Copper activity in soil solution II Relation to copper accumulation in young snapbeans J Soil Sci Soc Am v 51 (3) p 573-578 [NAL-56.9-SQ3] 26 Payne, G.G., D.C Martens, C Winarko, and N.G Perera.1988 Form and availability of copper and zinc following long-term copper sulfate and zinc sulfate applications J Environ Qual 17:707-711 (4) 198 [NALQH540.J6] 27 Rhee, J.A.,van 1977 Effects of soil pollution on earthworms Pedobiologia 17:201-208 [NAL-56.8-P343] 28 Reuther, W., and P F Smith 1952 Effects of high copper content on sandy soil on growth of citrus seedlings Soil Science 75: 219-224 [NAL 56.8 Q503] 29 Sumner, M E., 2000 Handbook of Soil Science CRC Press, Boca Raton, FL General reference [NAL-S591H23-2000] 30 Terry, R.E., D.W Nelson, and L.E Sommers 1979 Carbon cycling during sewage sludge decomposition in soils Soil Sci Soc Am J 43:494-499 [NAL-56.9-SQ3] 31 U.S EPA.1995 A Guide to the Biosolids Risk Assessments for the EPA Part 503 Rule Office of Wastewater Management, Washington DC EPA/832-8-93-005 [NAL-S22.C6] INTERNET REFERENCES 32 EXTOXNET (http://ace/orst.edu/info/extoxnet/pips/coppersu.htm) Cu Lit Review J Davis 14 11/09/04 ... (monohydrate) Formulas Cu Cu(NO3)2•3H2O Cu( C2H3O2)2•H2O CuC2O4•0.5H2O CuCl2•2CuO•4H2O Cu( NH4)PO4•H2O CuSO4• 3Cu( OH)2 CuSO4•5H2O CuSO4•H2O Chelates Na 2Cu EDTA NaCu HEDTA Elemental Cu % 100 32 40 52... relationships between soil -Cu and Cu- tissue accumulation Higher shoot Cu occurred with Cu- salt treatments, but sludge delivered higher root -Cu accumulations at lower Cu- concentrations in the soil... before accurate predictions of Cu uptake can be made; Cu concentration in shoot tissue increased linearly with Cu concentration of sludge; root Cu content is influenced not only by sludge Cu content,