Városi szennyvíziszap-terhelés hatásának vizsgálata tenyészedény-kísérletben. II

Translated title of the contribution: Study on the effect of urban sewage sludge application in a pot experiment. II

Imre Kádár, Balázs Morvai

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

In the 3rd year of a pot experiment the effect of urban sewage sludge application was studied on the mineral composition of spring barley and on the total (estimated after digestion with cc. HNO3+cc. H 2O2) and NH4-acetate+EDTA-soluble Zn, Cu, Cr, Cd and Hg contents of the experimental soils (acidic and calcareous sand, acidic and calcareous clay). For each soil, sludge application levels of 0, 7.5, 15, 30 and 60 g/kg/3 years were applied, in terms of air-dry matter. In the field the maximum 60 g/kg rate would be equivalent to ploughing in 180 t/ha air-dry matter, giving a mass ratio of 6% in the ploughed layer. The 5 sludge rates x 4 soils = 20 treatments x 4 replications gave a total of 80 pots each year. The pots were 10-litre plastic buckets with perforated bases. The main conclusions were as follows: - Despite the fact that the maximum application rates exceeded the permitted limit by 10-14 times for Zn, Cu, Cr and Cd over a period of three years, the mean grain yield of spring barley was 5 times greater and the straw yield 3.5 times greater than the control in the 3rd year. No yield depression was observed, as reported earlier (KÁDÁR & MORVAI, 2007). The sludge had a pH of 6.1, with 35% organic matter content and 4.6% Ca. On acidic soils there was an increase in the pH, while on calcareous soils it declined, together with the Scheibler CaCO3%. There was an increase in the calcium content of the soils and a reduction in the carbonate content. The maximum addition of 2% organic matter was detectable in the soil; the organic matter was not decomposed. In the sandy soils the organic matter content was quadrupled. The total salt content of the soils rose by 0.7 g/kg at the maximum application rate. - Approximately 100% of the zinc, copper, chromium and cadmium and 80% of the mercury added with the sludge could still be detected in the soil at the end of the 3rd year. After the 1st year of the experiment only approx. 60% of the added Zn, Cu, Cr and Cd quantities could be detected after digestion with cc. HNO3+cc. H 2O2, while the Hg content was below the detection limit. In the 1st year of the experiment 30-40% of the Zn, Cu and Cd and less than 1% of the Cr could be detected in the NH4-acetate+EDTA- soluble fraction, while after the 3rd year 70-80% of the Zn, Cu and Cd and 2-10% of the Cr was detected, while the Hg was still below the detection limit. - The Zn, Cu and Cr contents of the by-products of spring barley were 2-4 times higher and that of Cd 11 times higher at the maximum application rate. In the seed yield the Zn and Cu concentrations were again 2-3 times higher, while the Cd increased by an order of magnitude. No Hg accumulation could be detected in either the by-products or the seed yield. There was also no accumulation of Cr in the seed. Despite the fact that the application limits were exceeded, the spring barley was still suitable for fodder purposes, and the seed yield was even fit for human consumption in the Cr, Cd and Hg treatments. Table 1. Authorised rates of contamination for the application of sewage sludge to arable land, the composition of the urban sewage sludge applied in the pot experiment, and the resulting soil contamination levels. 1. Authorised rate. (1) Element symbol. (2) Maximum in sludge dry matter, mg/kg. (3) Authorised application rate, kg/ha/year. (4) Maximum in the soil, mg/kg. (5) In uncontaminated soil (background), mg/kg. 2. Rate applied in the pot experiment (urban sewage sludge). (6) Measured in the sludge dry matter, mg/kg. (7) Application rate, kg/ha/year. (8) In control soils (background), mg/kg. Table 2. Effect of urban sewage sludge on the parameters of the soils used in the pot experiment in 2001, at the end of the 3rd year. (1) Soil code. (2) When the experiment was set up in 1999. (3) At the end of the 3rd year of the experiment in 2001. (4) Sludge application rate, g dry matter/kg soil over 3 years. (5) LSD5%. (6) Mean. A. Total salts, g/kg. Note: Sewage sludge properties: pH 6.1; ash 45%, organic matter 35%, Ca 4.6%. Table 3. Effect of urban sewage sludge on the Zn content of the experimental soils and of spring barley in 2001. (1) Site of origin of the soil. a) Mean. (2) Sludge application rate, g dry matter/kg soil over 3 years. (3) LSD5%. (4) Mean. A. Application rate, mg/kg soil. B. Total cc. HNO3+cc. H 2O2-soluble content of the soil, mg/kg. C. NH 4-acetate+EDTA-soluble content of the soil, mg/kg. D. Zn content in the straw + husks of spring barley E. Zn content in spring barley seed, mg/kg. Note: Phytosanitary maximum in grain fodder and roughage: sheep: 300, cattle: 500, pigs and poultry: 1000 mg Zn/kg (CHANEY, 1982). Authorised limit in flour or ground cereal for human consumption: 30 mg Zn/kg. The sludge contained 0.62% Zn. Table 4. Effect of urban sewage sludge on the Cu content of the experimental soils and of spring barley in 2001. (1)-(4), A-E: see Table 3. Note: Phytosanitary maximum in grain fodder and roughage: sheep: 25, cattle: 100, pigs: 250, poultry: 300 mg Cu/kg (CHANEY, 1982). Authorised limit in flour or ground cereal for human consumption: 5 mg Cu/kg. The sludge contained 0.19% Cu. Table 5. Effect of urban sewage sludge on the Cr content of the experimental soils and of spring barley in 2001. (1)-(4), A-E: see Table 3. Note: Phytosanitary maximum in grain fodder and roughage estimated to be 3000 mg/kg in the form of Cr(III)-oxide (CHANEY, 1982). Hungarian regulations contain no authorised Cr levels. The sludge contained 0.18% Cr. Table 6. Effect of urban sewage sludge on the Cd content of the experimental soils and of spring barley in 2001. (1)-(4), A-E: see Table 3. Note: Authorised quantity in grain fodder and roughage in Hungary: 2 mg Cd/kg. Authorised limit in flour or ground cereal for human consumption: 0.1 mg Cd/kg. The sludge contained 35 mg/kg Cd. Table 7. Effect of urban sewage sludge on the Hg content of the experimental soils and of spring barley in 2001. (1)-(4), A-E: see Table 3. Note: The NH 4-acetate+EDTAsoluble content of Hg was below the 0.05 mg/kg detection limit, while in the plants Hg was below the 0.12 mg/kg detection limit, irrespective of the treatment. The sludge contained 16 mg/kg Hg.

Original languageHungarian
Pages (from-to)97-112
Number of pages16
JournalAgrokemia es Talajtan
Volume57
Issue number1
DOIs
Publication statusPublished - Jun 1 2008

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ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Soil Science

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