Ecoregion Total nitrogen, mg L-1 Total phosphorus, μg L-1 USEPA suggested 25th percentiles 75th percentiles USEPA suggested 25th percentiles 75th percentiles I 0.31 - 0.18-0.21 47 - 20 II 0.12 0.07-0.08 0.13-0.21 10 3-13 9-20 III 0.38 0.78 0.05-0.29 22 10 30-40 IV 0.56 0.44-0.61 0.12-1.30 23 19-20 70-170 V 0.88 0.60-0.99 0.37-1.19 67 20-70 70-140 VI 2.18 1.86 0.44-2.50 76 66-70 60-181 VII 0.54 0.48-1.56 0.17-0.33 33 17-60 30 VIII 0.38 0.27-0.40 0.18-0.39 10 7-24 10-20 IX 0.69 0.33-2.01 0.17-0.68 37 20-90 50-60 X 0.76 0.92 0.55-0.67 128 147 60 XI 0.31 0.16-0.29 0.17-0.38 10 4-20 18-20 XII 0.90 - 0.61-0.71 40 - 30 XIII - - 0.65-0.79 - - 40 XIV 0.71 0.62-1.85 0.63-0.76 31 23-82 20

Table 1: Stream total nitrogen and total phosphorus criteria suggested by USEPA for the fourteen aggregate eco regions [8] and the 25th and 75th percentiles reported in the literature [7].

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