Soil amendments

It will also be important to understand the rhizosphere ecology around the roots of metal accumulating plants fully. Maximizing the bioavailabihty of the contaminant metals in this zone may require the optimization of the microbial communities, or perhaps the addition of soil amendments. There are early indications that such intervention may be beneficial (88), but research in this area is at a very early stage. 

Calcium. Calcium is the fifth most abundant element in the earth s cmst. There is no foreseeable lack of this resource as it is virtually unlimited. Primary sources of calcium are lime materials and gypsum, generally classified as soil amendments (see Calcium compounds). Among the more important calcium amendments are blast furnace slag, calcitic limestone, gypsum, hydrated lime, and precipitated lime. Fertilizers that carry calcium are calcium cyanamide, calcium nitrate, phosphate rock, and superphosphates. In addition, there are several organic carriers of calcium. Calcium is widely distributed in nature as calcium carbonate, chalk, marble, gypsum, fluorspar, phosphate rock, and other rocks and minerals. 

Small tire chips have also been utilized as a soil amendment to improve athletic playing fields (see Recreational surfaces). A patented process marketed under the trade name Rebound (fai Tire) combines cmmb mbber from scrap tires with composted organic material to reduce soil compaction, resulting in better athletic playing surfaces (52). Installations have been made in Florida, California, Colorado, Hawaii, Maryland, Michigan, Missouri, Nevada, Virginia, and Wisconsin. 

GCSAA - GCM July 2000 - Soil amendments affect turf... five days (9). To improve water-holding properties, another team recommended the use of diatomaceous earth as an amendment to sand (8). However, another report.., http //WWW. gcsaa. org/gcm/2000/july00/07soil. html... 

No TCDD could be detected in soil with a detection limit of less than 1 ppb. Gas chromatographic (GC) traces at the left of Figure 1 represent a soil which would have contained 5 ppb of TCDD traces at the right are the unamended soil extracts. Arrows indicate the position where TCDD would occur. At the bottom right is a trace of the extract from a soil amended at the 1 ppb TCDD level. 

TABLE V. Recoveries of N-Nitrosobutralin from Incubation of C-Butralin in Matapeake Loam Soil Amended with Sodium Nitrite ... 

C. E. Heijnen, C. H. Hok-a-Hin, and J. D. Van Elsas, Root colonisation by Pseudomonas fluorescens introduced into soil amended with betonite. Soil Biology and Biochemistry 25 239 (1993). 

E. S. Jensen, Mineralization-immobilization of nitrogen in. soil amended with low C N ratio plant residues with different particle sizes. Soil Biol. Biochem. 26 519 (1994). 

Aliphatic acids such as butyric acid have been previously implicated as being allelopathic compounds (46, 47, 23). Chou and Patrick (23) isolated butyric acid from soil amended with rye and showed that it was phytotoxic. Hydroxy acids have also been shown to possess phytotoxic properties (48) but have not been implicated in any allelopathic associations. Since SHBA is a stereo isomer, and the enantiomer was not identified because of impurity, all bioassays were run using a racemic mixture. The D-(-) stereo isomer of SHBA has been isolated from both microorganisms and root nodules of legumes and is suspected to be a metabolic intermediate in these systems (49). It is likely that only one enantiomer was present in the extract therefore, the true phytotoxic potential of this compound awaits clarification of the phytotoxicity of the individual enantiomers. 

For compacted, low-permeability soil liners, the U.S. EPA draft guidance recommends natural soil materials, such as clays and silts. However, soils amended or blended with different additives (e.g., lime, cement, bentonite clays, and borrow clays) may also meet the current selection criteria of low hydraulic conductivity, or permeability, and sufficient thickness to prevent hazardous constituent migration out of the landfill unit. Therefore, U.S. EPA does not exclude compacted soil liners that contain these amendments. Additional factors affecting the design and construction of CCLs include plasticity index (PI), Atterburg limits, grain sizes, clay mineralogy, and attenuation properties. 

Wang Z, DeLaune RD, Lindau CW, Patrick WH. Methane production from anaerobic soil amended with rice straw and nitrogen fertilisers. Fert. Res. 1992 33 115-121. 

Surfactants Soil amended with PLE (MeOH/H20 90 10, v/v) and SPE (RP-Clg) LC-MS/MS Marine sediments Soil amended with sludge [33]... 

Emmerich et al. (1982) reported that in soil solution of arid soils amended with sewage sludge, free Ni2+ ion accounted for 60-70% of the total Ni in soil solution. Sposito and Page (1984) indicated NiHC03+ and NiC03° were also important Ni speciations in alkaline and calcareous soils. 

In Californian soils amended with sewage sludge for seven years, Ni is mostly present in the residual (64%), the organically bound (12%) and the carbonate fractions (18%) (Chang et al., 1984). Nickel in the carbonate fraction is found to increase with time in arid zone soils amended with sludge (Knudtsen and O Connor, 1987). In the sludge-amended calcareous soils of Southeast Spain, the residual and the carbonate bound Ni fractions are the major solid-phase (Moral et al., 2005). 

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