macro and micromorphological investigations were conducted on selected xerepts soils from southern iran to identify changes in soil characteristics with time. soil samples from similar pedons of four irrigated orchards ranging in age from 20 to 100 years were studied and compared with soil samples of a pedon of non-irrigated land. in addition to routine analyses, undisturbed blocks of soils...

Acidic mine drainage (AMD) containing elevated concentrations of dissolved iron and other metals can be neutralized to varying degrees by reactions with limestone in passive treatment systems. We evaluated the chemical and mineralogical characteristics and the effectiveness of calcitic and dolomitic limestone for the neutralization of net-acidic, oxic, iron-laden AMD from a flooded anthracite m...

The influence of mineral substrate composition and structure on bacterial calcium carbonate productivity and polymorph selection was studied. Bacterial calcium carbonate precipitation occurred on calcitic (Iceland spar single crystals, marble, and porous limestone) and silicate (glass coverslips, porous sintered glass, and quartz sandstone) substrates following culturing in liquid medium (M-3P)...

Externally shelled cephalopods were important elements in open marine habitats throughout Earth history. Paleotemperatures calculated on the basis of the oxygen isotope composition of their shells can provide insights into ancient marine systems as well as the ecology of this important group of organisms. In some sedimentary deposits, however, the aragonitic shell of the ammonite or nautilid is...

Excessive soil acidity is known to have potential negative impacts on crop production. The chemical and physical characteristics of a liming material determine its capacity to neutralize soil acidity. The material CaCO3 equivalent (CCE) and fineness effectiveness estimates are included in effective CCE (ECCE) assessments of a material’s liming value and to decide application rates. The objectiv...

Introduction Conclusions References

We describe a new type of composite skeletal tissues in which calcite and stabilized amorphous calcium carbonate (ACC) coexist in well-defined domains. The organisms that form such structures are widely separated in the animal kingdom phylogenetic tree: calcareous sponges and ascidians. This paper compares the microstructures of their composite skeletal elements: The triradiate spicules from th...

—Bivalve death assemblages from subtidal environments within the tropical Bocas del Toro embayment of Caribbean Panama permit a test of the extent to which levels of damage are determined by the intrinsic nature of shell supply (proportion of epifaunal species, thick shells, calcitic shells, low-organic microstructures), as opposed to the extrinsic postmortem environment that shells experience....

In the preceding paper, the author has discussed the very important differences between the spiral growths of the aragonitic and calcitic shells, and suggested that a definite diffusion of the mother fluid existed on inner shell surface is favored by moving of the mantle in the direction of its own elongation, where concentration gradients assume to occur. Furthermore the differences between ar...

Barium/Calcium profiles of bivalve shells are characterized by flat background signals periodically interrupted with sharp peaks, with the background signals correlated with water Ba/Ca. To test if the peaks are an environmental signal related to productivity, we analyzed high resolution Ba/Ca profiles in bivalve shells that grew adjacent to one another. Two aragonitic Saxidomus giganteus show ...