Retraction to: Environ Monit Assess (2012) 184:7323–7328

DOI 10.1007/s10661-011-2501-0

The authors voluntarily retract their article from Environmental Monitoring and Assessment on the grounds that certain parts/portions of the article have been published elsewhere and were not appropriately referenced. The situation is due to honest error and the authors would like to apologize for any inconvenience this may have caused to the readers.