Figure 4.4: Summary data for oxidised-N and ammoniacal-N from the NRWQN over a 17-year period (1989-2005)

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This figure shows nitrates-nitrites (NOx-N) and ammoniacal-N trends. There has been a steady increase in concentrations of NOx-N in rivers where this important plant nutrient was already high (ie, 95th percentile). In contrast, rivers with very low levels of nitrate have shown a decreasing trend during 1989–2005 (ie, nitrate levels are declining). Levels of ammoniacal nitrogen have shown strong downward trends in most of our rivers, but rivers with high NH4-N concentrations (ie, 95th percentile) have not shown this decreasing trend.