Rapid and precise measurement method for adsorbed

A new method has been developed for the determination of adsorbed

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on sediments. The method utilizes sediments directly in a closed loop counting system and measures the daughter

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. Because the recoil path length of

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is small compared to the sediment particle size, adsorbed

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is released to the gases circulating in the closed loop

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counting system and

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produced internally within the sediment particles is effectively excluded. The method has been calibrated against (1) multi-step Na⁺ displacement of

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and (2) multi-step Zn²⁺ replacement of

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. It has been found to accurately quantify the adsorbed component with a significant savings in laboratory time and with greater precision. Combined with dissolved

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measurements of the porewater, distribution coefficients can be accurately calculated. This method has potential for direct application to water column

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balances in estuaries, coastal water and salt marshes. When used to extract the reactive transport dynamics of

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in the sediment, the method may have applications to trace metal transport in sediments.