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Observations on the mobility of arsenic in the sediments in Lake Ohakuri

by O'Brien, Glennys Anne

Abstract (Summary)
Restricted Item. Print thesis available in the University of Auckland Library or available through Inter-Library Loan. The mobility of arsenic in the sediments in Lake Ohakuri has been investigated by monitoring seasonal changes in the concentration of arsenic in the sediment interstitial water, the sediment solid phase and the overlying lake water. The behaviour of iron has been similarly investigated because of the arsenic-iron association. Seasonal changes in the temperature and dissolved oxygen concentration of the lake water were also monitored. Stratification was found to occur in the lake over the summer periods of both 1980-1981 and 1981-1982. This was accompanied by oxygen depletion in the hypolimnion and the accumulation of arsenic and iron in the hypolimnion following release from the sediment. The turnover event appears to have resulted in the loss of this arsenic from the lake. The concentration of arsenic in the sediment solid phase was found to be high in the surficial oxidized sediment layer. This was considered to be the result of desorption of some arsenic from buried sediment as a result of the diagenetic reduction of iron followed by readsorption of this arsenic in the upper oxidized layer. The Whirinaki arm sediments appear to be somewhat different as a result of more reducing conditions. The accumulation of arsenic in the top layer of these sediments was found to be much less pronounced. The release of arsenic from these sediments appeared to occur more rapidly in response to oxygen depletion in the overlying water. Analytical method development studies on the speciation of arsenic were undertaken in association with the investigations into the arsenic mobility problem.
Bibliographical Information:

Advisor:

School:The University of Auckland / Te Whare Wananga o Tamaki Makaurau

School Location:New Zealand

Source Type:Master's Thesis

Keywords:

ISBN:

Date of Publication:01/01/1983

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