長期施用污泥及堆肥對土壤中及作物體中微量元素累積之影響 -1
陳尊賢
台大農化系 soilchen@ccms.ntu.edu.tw
, tel: 2369-8349
Printed on Nov. 2, 2004
Introduction
 Short-term effect and long-term effects
 Long term accumulation and distribution of metals
 Crop yield response to metals input into the soils
 Plant metals uptake and long term changes in bioavailability of metals
Long-term experiments with sludge-borne metals
 At least 10 years
 23 selected sites in France, USA, UK, DK, Germany (book, p162-163, Table 1)
 maximum input of metals (book, p164, Table 2)
Long-term accumulation and distribution of metals in sludge-treated soils
 almost distributed in the surface 40 cm (p. 166, Table 3)
 higher metals conc. existed in the sludge, higher accumulation of metals in the surface soils
Heavy metals balance in the soils
 several hypotheses have been suggested to account the incomplete metal recovery.
 Uptake by crop, leaching to groundwater, lateral soil movement, others ?
 Metals recovery: 55-80%, 32-42% of metals inputs. (p. 167, Table 5)
 Metals lateral movement may different from one metal to another (P168, Fig. 1)
Heavy metals extractability by mild chemical reagents
 the most frequently employed reagents: HCl, EDTA, acetic acid, NTA, DTPA, CaCl2.
 EDTA extractable metals of soil decrease with time
 Ratio of extractable metals vs. total metal contents.
Response of crop yields to heavy metals in the experiments
 the application of sewage sludge exhibited a positive effects on plant growth in 65% of the case (in p 162-163, Table 1)
Grain crop yield
 Case study in Bx1 site (p. 170, Table 6). average grain yield was 8% above the control treatment.
 Case study in Bx2 site in Cd and Ni-contaminated site (P 171, Fig. 2)
Phytotoxicity of sludge-borne metals
 Phytotoxicity is rarely observed even though large amounts of metals are added in the sludge –amended soils
 Several hypotheses have been developed to account for the low phytotocxicity, eg.
Increase soil pH, sorption by Fe and Mn oxides, or OM, and antagonistic effects.
Metal accumulation by plants growing in sludge-amended soil
 Focused studies on Zn, Mn, Cu, Cd, Pb, Ni
 Rarely investigated on As, Be, Co, Hg, Mo, Se, and Tl.
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長期施用污泥及堆肥對土壤中及作物體中微量元素累積之影響 -1
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Metal accumulation in plants related to metals, plant species, and plant parts
 Nonlinear regression model: Y= a + b (1-e
–cx
) (Fig. 4, 5, 6, 7) (P175-176)
 Metal accumulation in crops resulting from annual and cumulative addition of sludge
(Fig 4, 7), (Fig 8 &9) (p. 178-179).
 Regression model for different metals (p. 178, Table 8)
 Ratio of metal removal to metal input: <1% (Table 10)
 Ratio of metal in grain vs. metal conc. in the leaf: <10% (Table 11).

Cd: case study
 Cereal grain always contained less Cd than their vegetable aerial parts (Table 12, 13).
 Total soil Cd of 5-45 mg/kg resulted in 3-18 mg/kg in sugar beet leaves (Table 14).
 Tobacco leaf is widely recognized as a Cd accumulator (table 15).
Cr: case study
 Cr translocation from soil to crops is generally insignificant (Table 12)
 Cr conc. in leaf of corn decreased with cumulative sludge application, due to a marked increase of soil pH (Table 16)
 Cr accumulation in dicotyledonous species ( 雙子葉 ) (Table 14)
 Cr in the sludge-treated soil does not pose any serious problem.
Cu: case study
 Cu availability was enhanced as the OM in Sewage sludge decayed or due to increasing conc. of Cu in the soil (Fig. 10)
 Cu in barley grain may reach values of >200 mg/kg
 Oats and corn grain may reach values of >20 mg/kg
 Sugar beet roots may contain equal or higher amount of Cu than the corresponding leaves, ranged from 5-30 mg/kg (Table 14).
 Cu conc. in tobacco is higher than that in soybean (Table 15)
Pb: case study
 P uptake by crops was generally slight and was not influenced by the metal level or pH of the soil (Table 12, 13, 14)
 Pb uptake by corn on sludge –amended soils was insignificant (Table 12)
Ni: case study
 Ni conc. in grain could reach 0.8 up to 5 mg/kg (Table 12)
 Ni accumulated in both sugar beet roots and leaves ranged from 5 to 30 mg/kg (table
14).
Zn: case study
 Zn conc. in corn 6 th leaf obtained from hogher rate of sludge plot was sharply higher than in the control (Fig. 4)
 600 mg/kg of Zn conc. in corn grain may nor exhibit the toxicity, compared with the threshold values of 300 mg/kg.
 braley grown on sludge=treated soils also accumulated Zn, and metal conc. in barley leaves and grains reached as high as 820 and 250 mg/kg (Table 12 and 13).
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