Saturday, 15 July 2006
163-42

Evaluation of Greenhouse Gases Emissions from Soils Amended with Sewage Sludge.

Paramasivam Sivapatham1, Kenneth Sajwan1, Gamola Fortenberry2, Eric Stidum3, LaShasta Robinson1, Adeniyi Moses1, Ashok Alva4, and Ali Fares5. (1) Savannah State Univ, 140 Drew Griffith Hall New Annex,, P.O. Box 20600, Savannah, GA 31404, (2) Florida Agricultural and Mechanical Univ, Tallahassee, FL 32307, (3) Rust College, 150 Rust Avenue, Holly Springs, MS 38635, (4) USDA-ARS, 24106 North Bunn Road, Prosser, WA 99350-9687, (5) Natural Resources and Environmental Management Dept, Univ of Hawaii at Manoa, 1910 East-west Road, Honolulu, HI 96822

Introduction: Increase in concentration of various greenhouse gases and their possible contributions to the hypothetical global warming is becoming a serious concern.  Agricultural practices, fossil fuel burning, deforestation, industrial emissions, and wetlands have contributed to atmospheric increases of carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons.  Some of these gases may contribute to “global warming”.  Significant amount of emission of methane and nitrous oxide are mainly coming from anthropogenic activities such as cultivation of wetland rice and application of various C and N rich soil amendments.  Organic soil amendments, including sewage sludge, are currently gaining increased attention for soil improving physical and chemical properties of agricultural soils for enhancing the yield and quality of various crops. Therefore, evaluation of flux of various greenhouse gases from soils amended with sewage sludge is essential to quantify the release of various greenhouse gases into the atmosphere. 

Materials and Methods:  Studies were initiated to evaluate the emission of greenhouse gases (CO2, CH 4 and N 2O) from two soils with contrasting properties (Candler fine sand from Florida [FS] and Ogeechee loamy sand from Georgia [GS]) amended with varying rates (0, 24.7, 49.4, 98.8, and 148.3 Mg ha-1) of two types of sewage sludge (industrial [ISS] and domestic [DS] origin). Domestic [DS] sewage sludge had 39.5 % C and 4.6 % N where as the industrial [ISS] sewage sludge used in this experiment had 27.8% C and 3.7% N.  Twenty grams of respective soil samples were amended with appropriate amount of sewage sludge, to attain the above per hectare rates, in 250 mL Qopak bottles and incubated, in static chambers, under anaerobic condition at field capacity soil water content for the respective soils.  Gas samples were extracted on a daily basis and injected to a gas chromatograph (GC 14) equipped with electron capture detector (ECD) and flame ionization detector (FID) to monitor CH4, CO2 and N2 O.  Effect of acetylene on the emission of N2O was also tested in this study.  Static chambers were flushed to remove all head space gases upon completion of each sampling event and the anaerobic condition was ensured for monitoring of gaseous emission for the next sampling event.  This procedure was adapted throughout the study period to facilitate the determination of emission rates at each sampling events.

Results and Discussion:   

Soil

Type of SS

Rates of SS

Mean cumulative emission per gram of soil with C2H2

Mean cumulative emission per gram of soil without  C2H2

   

Mg ha-1

CO2

CH4

N2O

CO2

CH4

N2O

mg

µg

µg

mg

µg

µg
                 

FS

DS

    0.0

  9.44

159.84

    6.27

12.08

59.42

   4.19

   

  24.7

25.19

168.96

  51.19

27.60

60.18

 39.20

   

  49.4

38.37

169.35

216.21

40.71

62.19

76.28

   

  98.8

57.49

175.70

244.72

58.15

62.75

227.42

   

148.3

72.74

191.25

349.57

71.77

65.18

280.51

                 
 

ISS

    0.0

12.72

110.17

27.40

11.59

56.94

11.08

   

  24.7

23.02

124.12

40.97

24.29

58.12

29.78

   

  49.4

32.92

127.40

44.62

32.10

58.62

34.76

   

  98.8

41.41

141.94

45.19

47.61

62.10

37.74

   

148.3

59.25

168.93

60.71

54.37

63.96

50.71

                 

GS

DS

    0.0

16.81

112.89

    8.67

18.30

55.59

    6.08

   

  24.7

31.58

115.04

  44.24

26.13

55.69

  29.60

   

  49.4

37.06

120.92

  66.52

33.48

60.12

47.50

   

  98.8

52.65

129.23

217.31

53.00

60.21

159.68

   

148.3

65.06

152.71

270.90

71.54

69.78

218.72

                 
 

ISS

    0.0

18.30

  86.69

29.20

20.49

54.58

  9.72

   

  24.7

25.84

  87.59

29.95

26.00

58.62

28.90

   

  49.4

27.30

102.05

31.52

30.43

59.13

31.36

   

  98.8

46.41

102.74

50.31

45.65

59.38

46.16

   

148.3

53.68

118.66

69.21

55.07

75.50

51.16

Results of this study showed a very clear trend of increasing emission of various greenhouse gases with rates of amendment irrespective of the type of soils and amendments. Emission of gases was greater in both soils amended with sewage sludge from domestic origin rather than from industrial origin suggesting that either lower C and N content or possible harmful chemicals present in industrial sludge may hinder the microbial activity. Furthermore, results of this study indicated a greater amount of gaseous emission from a sandy soil amended with sewage sludge than those from a loamy sand soil.  Results also clearly depicted the inhibitory effect of acetylene in both soils by producing more nitrous oxide emission compared to the soils not receiving acetylene. 

Conclusion:Results of this study suggest the need to consider the greenhouse gas emissions from soils when amended with organic soil amendments such as sewage sludge, especially at high rates. Results also indirectly imply the importance of this evaluation due to the potential emission of various greenhouse gases in the event of accidental spills of sewage into wetland ecosystem.


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