Month (I) Month (J) Mean Difference (I-J) Std. Error Sig. 95% Confidence Interval Lower Bound Upper Bound October December 1.0190* 0.24471 0.000 0.3692 1.6689 February 0.3496 0.24471 0.925 -0.3002 0.9995 April 0.8507* 0.24471 0.003 0.20085 1.5006 December October -1.0190* 0.24471 0.000 -1.6588 -0.3692 February -0.6694* 0.24471 0.040 -1.3192 -0.0195 April -0.1683 0.24471 1.000 -0.8182 0.4816 February October -0.3496 0.24471 0.925 -0.9995 0.3002 December 0.6694* 0.24471 0.040 0.0195 1.3192 April 0.5011 0.24471 0.249 -0.1488 1.1509 April October -0.8507* 0.24471 0.003 -1.5006 -0.2008 December 0.1683 0.24471 1.000 -0.4815 0.8182 February -0.5011 0.24471 0.249 -1.1509 0.1488 *The mean difference is significant at the 0.05 level

Table 1: Bonferroni multiple comparison test of means chromium concentration due to month.