Geographical | TP | NO3-N | NH4-N | DO | ||
---|---|---|---|---|---|---|
Rationale | Area | (mg/l) | (mg/l) | (mg/l) | % | Reference |
Median of reference data | USA (all states) | 0.013–0.048 | na | na | na | [76] |
75th percentile of reference data | USA (Montana) | 0.003–0.170 | 0.01–0.25 | 0.004–0.09 | na | [78] |
80th of least disturbed condition | Canada | 0.011–0.062 | na | na | na | [81] |
75th percentile of reference data | Northeast China | 0.046 | na | na | na | [82] |
Thresholds for environmental Class I quality standards for surface water | China | 0.020 | na | 0.15 | na | [83] |
Rough values at 4 least disturbed sites | Australia (New South Wales) | 0.033–0.077 | na | na | 94.5–97.8 | [84] |
Mean reference data | Europe (Central- Baltic) | 0.020–0.040* | 2–6 | 0.05–0.10 | 95–105 | [20] |
90th percentile of reference data | Europe (Mediterranean) | 0.070 | 1.15 | 0.09 | 73.7–127.9 | [19] |
75th percentile of reference data | Europe (IT, UK, FR, CY) | 0.050 | 2.82 | 0.04 | 100 | [18] |
90th percentile of reference data | Finland | 0.015–0.020 (0.040**) | na | na | na | [47] |
Reference thresholds based on predictive models | Sweden | 0.025 (0.030**) | na | na | na | [47] |
Natural and semi-pristine conditions derived from expected output rates from the catchment (mean values) | UK | 0.006–0.493 | na | na | na | [10] |
High-quality thresholds (very low anthropogenic influence) | UK | 0.020* | 1.1 | na | na | [85] |
75th percentile of reference data | Cyprus | 0.005 | 0.1 | na | 105 | [86] |
75th percentile of reference data | Greece | 0.0865 | 0.18 | 0.016 | na | [87] |
75th percentile of reference data | Spain | 0.082* | 0.672 | 0.038 | 98.9–116.4 | [88] |
Reference thresholds values | Portugal (Mondego basin) | 0.060 | 0.67 | 0.1 | [89] | |
75th percentile of reference data (90th for TP) | Italy (state wide, all river types) | 0.050 | 0.60 | 0.03 | 90 | [27] |
75th percentile of reference data | Italy (state wide) | 0.049 | 0.88 | 0.03 | 100 | This paper |
90th percentile of reference data | Italy (state wide) | 0.060 | 1.39 | 0.05 | 104 | This paper |