Mapping of Shahrekord Groundwater Nitrates and Phosphorous Based on an Integrated Index and its Usage for Assessing Contamination over a Time Interval

Document Type : Research Paper

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Abstract

Intensifying contamination of Shahrekord aquifer has been already understood and documented by periodic sampling, use of simple statistical indicators and established procedures. However, integrated management of aquifers requires improved methods. The main purpose of this study was to detect changes in both nitrate and phosphorus pollution of Shahrekord groundwater over a period of four years (2006-2010) by an integrated index. For this purpose, nitrate and phosphorus maps were normalized by WHO standards, converted to rank maps and then, integrated maps of nitrate and phosphorus were produced for both years of 2006 and 2010. Changes of integrated index over this 4-year period were obtained by differencing the two maps. Integrated map was strongly correlated with nitrate map (r=0.94) and with phosphorus map (r=0.87) indicating it properly reflected the distribution of both contaminants. Difference map showed a minimum of 2%, a maximum of 4% and on average 2.8% of increase in contamination. During this period, in approximately 5.3% of the aquifer, water quality deteriorated. Compared with phosphorus, nitratehas a greater share inShahrekord aquifer contamination but over this period the phosphorus’s share has increased. Applying the procedure used in the present study, enables the managers and planners to quantify trends in aquifer contamination more accurately. Also, with this method, the relative involvement of each contaminant in pollution, at the beginning and end of a time interval, can be estimated. An integrated map and its affiliated integrated index of nitrate and phosphate in groundwater appears to be useful for the assessment of algal growth and its consequences such as clogging of low-pressure irrigation pipes, water smell and taste deterioration and increased cost of treatment.

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History

  • Receive Date: 13 January 2013
  • Revise Date: 10 October 2015
  • Accept Date: 04 February 2014
  • Publish Date: 23 September 2015

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