Composition and metal ion complexation behavour of humic fractions derived from corn tissue

被引:55
作者
Evangelou, VP [1 ]
Marsi, M [1 ]
机构
[1] Iowa State Univ, Dept Agron Crop Soil & Environm Sci, Ames, IA 50011 USA
关键词
carboxylic acid groups; compost; metal complexation constants; metal retention; organic matter; phenolic OH groups;
D O I
10.1023/A:1004862100925
中图分类号
S3 [农学(农艺学)];
学科分类号
0901 ;
摘要
Decomposition of fresh plant residues produces humic fractions with different molecular size and composition. It was hypothesized that the functional group-type and content of humic fractions depended on molecular size, which was expected to influence heavy-metal complexation behavior. In this study, corn (Zea mays L.) stalks and leaves were collected from the field and decomposed for an 8-month period to produce humic substances which were separated into three water soluble fractions, HF1, HF2 and HF3, from highest to lowest relative molecular size. Functional group determination showed that total, carboxylic and phenolic OH acidity increased as relative molecular size of humic fractions decreased. Furthermore, C/O ratios decreased, whereas N/C and H/C ratios remained relatively unaffected as relative molecular size of humic fractions decreased. Formation of Ca2+, Cd2+ and Cu2+ -humic fraction complexes and how these complexes were affected by pH and relative (humic fraction) molecular size were studied using potentiometric titration. Metal-humic complexes exhibited at least two types of sites with respect to Ca-2+, Cd-2+ and Cu-2+ complexation. Relative molecular size had a large significant influence on total metal-ion complexation, but it had a relatively small influence on complex stability at low levels of metal-ion complexation. Strength of metal-ion humic complexes followed the order Cu2+ > Cd2+ > Ca2+ and was affected by pH, especially for low affinity sites. Carboxylic and phenolic OH groups were most likely involved in complex formation. Magnitude of the metal-humic formation constants at the lowest equilibrium metal-ion concentration, under the various pH values tested, varied from 5.39 to 5.90 for Ca2+, from 5.36 to 6.01 for Cd2+ and from 6.93 to 7.71 for Cu2+. Furthermore, the formation constants appeared to be positively influenced by decreasing molecular size of water-soluble humic fraction, and increasing pH. These results inferred that soil management practices causing build-up of humic substances would affect mobility and bioavailability of metal-ions.
引用
收藏
页码:13 / 24
页数:12
相关论文
共 47 条
[1]  
Adams F, 1984, SOIL ACIDITY LIMING
[2]  
[Anonymous], 1994, HUMUS CHEM GENESIS C
[3]  
[Anonymous], [No title captured]
[4]   CHANGES IN SOIL PROPERTIES AFTER 10 YEARS CONTINUOUS NON-TILLED AND CONVENTIONALLY TILLED CORN [J].
BLEVINS, RL ;
THOMAS, GW ;
SMITH, MS ;
FRYE, WW ;
CORNELIUS, PL .
SOIL & TILLAGE RESEARCH, 1983, 3 (02) :135-146
[5]  
Bloomfield C., 1981, CHEM SOIL PROCESSES
[6]   INFRARED-SPECTRA OF SEWAGE SLUDGE FRACTIONS - EVIDENCE FOR AN AMIDE METAL-BINDING SITE [J].
BOYD, SA ;
SOMMERS, LE ;
NELSON, DW .
SOIL SCIENCE SOCIETY OF AMERICA JOURNAL, 1979, 43 (05) :893-899
[7]  
BRUGGENWERT MGM, 1982, SOIL CHEM B, P141
[8]   USE OF ULTRAFILTRATION FOR SEPARATION AND FRACTIONATION OF ORGANIC-LIGANDS IN FRESH WATERS [J].
BUFFLE, J ;
DELADOEY, P ;
HAERDI, W .
ANALYTICA CHIMICA ACTA, 1978, 101 (02) :339-357
[9]  
CHAPMAN HD, 1965, DIAGNOSTIC CRITERIA, P629
[10]   EFFECTS OF IONIC AND COMPLEXED METAL CONCENTRATIONS ON PLANT UPTAKE OF CADMIUM AND MICRONUTRIENT METALS FROM SOLUTION [J].
CHECKAI, RT ;
COREY, RB ;
HELMKE, PA .
PLANT AND SOIL, 1987, 99 (2-3) :335-345