K.K. Turekian622551turekianeditor.jpg Radioactive, radiogenic and isotope measurements in Earth materials provide useful approaches to the study of terrestrial and cosmic processes. Our laboratory has used these tools to address problems as diverse as the circultion of Long Island Sound and the cosmic dust flux to our planet. A few of the projects are listed: 1. Air samples and atmospheric precipitation are analyzed for ²²²Rn(radon) daughters such as ²¹⁰Pb and ²¹⁴Pb as well as cosmogenically produced ⁷Be and ³⁵S to determine: (a) the residence times of aerosols in different layers of the troposphere via ²¹⁴Pb, ²¹⁰Pb and ⁷Be, (b) the sources of ozone found in the troposphere based on correlations with ⁷Be and ²¹⁰Pb, and (c) the oxidation and precipitation kinetics (including dry deposition) of SO2 based on cosmogenic ³⁵S measurements. 2. The radioactive decay of ¹⁸⁷Re (half-life ca. 4.6x10¹⁰ years) produces ¹⁸⁷Os. The ratio of ¹⁸⁷Os to non-radiogenic Os (nominally represented by 186Os) in rocks undergoing weathering is determined by the Re/Os of the rock and its age. The variation in the relative sources of weathered material (high ¹⁸⁷Os/¹⁸⁶Os from continental crust, low ¹⁸⁷Os/¹⁸⁶Os from mantle-derived rocks) is sensed by contemporary sea water osmium and ultimately recorded in accumulating marine sediments. The tectonic history of the past 100 million years is inferred from Os isotope measurements in deep-sea deposits. 3. The measurement of ²²²Rn(3.4 d), ²²⁶Ra(1620 y), ²²⁸Ra(5.7 y) and ²²⁴Ra(3.6 d) in Long Island Sound water profiles provides information on the mean residence time of water in the Sound as well as the flux of nutrient-rich water from the New York City area. The radium isotop Read More Read Less