{'fraction_non_alphanumeric': 0.028, 'fraction_numerical': 0.066, 'mean_word_length': 4.9563492063492065, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Analysis and interpretation of water-quality trends in major U.S. rivers, 1974-81

1 Introduction 1 Methods and scope 2 Trend analysis and interpretation 5 Chloride 5 Sulfate 8 Nitrate 9 Alkalinity and base cations 10 pH 12 Suspended sediment 13 Total phosphorus 13 Dissolved-oxygen deficit 14 Fecal coliform and fecal streptococcus bacteria 16 Lead 17 Arsenic 19 Cadmium 20 Other trace metals 20 Conclusions 21 References cited 22 FIGURES 1-7. Maps showing: 1. Locations of sampling stations in the National Stream Quality Accounting Network and the National Water Quality Surveillance System in the conterminous United States 3 2. Change in surface-coal production in NASQAN drainage basins, 1974-81 7 3. Trends in flow-adjusted concentrations of chloride at NASQAN stations, 1974-81 8 4. Trends in flow-adjusted concentrations of sulfate at NASQAN stations, 1974-81 9 5. Trends in flow-adjusted concentrations of nitrate at NASQAN and NWQSS stations, 1974-81 10 6. Trends in flow-adjusted concentrations of alkalinity at NASQAN stations, 1974-81 11 7. Trends in flow-adjusted concentrations of suspended sediment at NASQAN stations, 1974-81 12 8. Graph showing comparison of the distribution of point-source biochemical oxygen demand loads for river reaches in cataloging units containing combined network stations with the similar distribution for all cataloging units 16 9, 10. Maps showing: 9. Trends in flow-adjusted concentrations of fecal streptococcus bacteria at NASQAN and NWQSS stations,