Chemical Characteristics of Surface Waters

1. Chemical Characteristics of Surface Waters

2. What’s In the Water? • Dissolved gases: CO2, O2, N2 • Major ions: Ca++, Mg++, Na++(hardness) • HCO3-, SO4-, Cl- (alkalinity) • usually in ppm range (mg/L) • conservative • Key Nutrients: PO4-3, NO3-, NH4+ • Usually in ppb range (ug/L) • Not conservative • Trace Elements: Cu, Zn, Fe, Al (ppb) • Particles: soil, organic matter Total Dissolved Solids (specific conduct.)

3. Atmospheric Inputs • Gases dissolve immediately (esp. CO2) • Most important of atmospheric gases • Adds to acidity of rainwater CO2 + H20 H2CO3 H+ + HCO3- **CO2 dissolution alone yields rainwater pH = 5.64 Carbonic acid Bicarbonate

4. Atmospheric Inputs (cont.) • Atmospheric pollutants (SO2, Nox)

5. Atmospheric Inputs (cont.) • Sea spray influence – % of several major ions in rainwater. From: Moss (1988)

6. Major Gases • O2 and CO2 usually saturated in small streams • > Turbulent mixing • < Biological activity • Large streams: O2 and CO2 influenced by: • Photosynthesis > oxygen • Respiration < oxygen (BOD) • Chemical Oxygen Demand (COD)

7. Oxygen Sources and Sinks

8. Annual Dissolved Oxygen Trends in Five Lake Monroe Inlet Streams

9. Dissolved Oxygen Solubility is Temperature-Dependent D.O. Temp.

10. Rock Weathering Rainfall and surface water wear down rocks and carry dissolved and particulate materials away. • Igneous rocks – 95% of Earth’s crust; very resistant • Metamorphic rocks – also resistant • Sedimentary rocks – 70% of continental crust surface; weathers easily; yields deep soils

11. Flowing water dissolves even resistant rock Turkey Run State Park

12. Highly soluble and porous limestone in Southern Indiana allows for underground rivers Cave Creek, Spring Mill State Park

13. Groundwater fed streams reflect the nature of the groundwater and its sometimes peculiar chemistry

15. Evaporation - Crystallization • 3rd major mechanism accounting for dissolved ions in surface water • e.g. Chemistry of streams in irrigated areas are much higher in dissolved salts • ex. Selenium in the Central California Fish & Wildlife Area

16. Source and fate of various elements in undisturbed forest of Hubbard Brook (%)

17. Total Dissolved Solids (TDS) • Def: sum of concentrations of major dissolved ions • Most rivers dominated by: HCO3-, Cl-, SO4-2 • Specific Conductance : appx. predictor of TDS TDS = K * specific conductance • K  0.55 – 0.75 • K determined empirically

18. VIRGIN RIVER MUDDY RIVER COLORADO RIVER Las Vegas Wash HOOVER DAM

20. LVB4.15 Colorado River Las Vegas Wash

21. Does TDS Vary With Discharge? TDS Discharge Discharge What would control this relationship??

22. Watershed Land Cover Controls These Relationships TDS Discharge Discharge Forested buffered • Less time for dissolution to occur Disturbed >dissolution of ions

23. With High Discharge, There is Little Time for Alkalinity Ions to Dissolve Data from Beanblossom Creek, Indiana

24. High Discharge Can Mobilize Particulates Beanblossom Creek Data

27. There may be little relationship in undisturbed or stable watersheds R2 = 0.0032

28. Supply and demand of various elements relative to phosphorus

29. Effects of Land Use on Stream Nutrient Concentration Source: Omernik (1977)

30. Nonpoint Source Suspended Solids Loss From Various Land Uses Source: Sonzogni et al. (1980)

31. Sediments and other stream materials are transported to downstream areas

32. Stream water quality changes following a forest clearcut Goshen Swamp (blackwater creek), NC

33. Changes in chemistry of stream water in two White Mt. Watersheds. Watershed 2 was completely deforested in 1966. **Why did sulphate decrease following deforestation?

35. Acidic Drainage Associated with Many Coal Mining Operations

36. Low pH Effects in Streams • <pH 5 • Oxidation of ammonia compounds ceases • Nitrification is reduced • Bacterial cell counts drop • < plankton due to low nutrient supplies • < salt uptake in crustacea and insects • < calcium carbonate availability for mollusks • > metal mobility

37. Toxic Compounds • Toxic Organic Compounds (TOC) • Synthetic compounds that contain carbon • e.g., PCBs, most pesticides and herbicides • Carbon has unique property to form a nearly infinite array of stable bonds with itself. • Chemical industry has used this to create many Synthetic Organic Compounds (SOC) that utilize the many arrays of carbon.

38. Toxic Compounds (cont) • Many are quite mobile in the environment: • with sediments (if high sorption coefficient) • dissolve in water (if high solubility) • Many TOCs persist in the environment • Many TOCs accumulate in the food web • WHY? • Don’t readily break down • Degradation products can be even more toxic (e.g., DDT DDE)

39. Pesticide movement in the hydrologic cycle.

40. National Water Quality Assessment Program (NAWQA) - USGS • 60 study units (river basins) studied • 3-5 years of intensive data collection

41. NAWQA Results • About 1 billion pounds of pesticides are used each year in the U.S. – 80% in agric. • Organochlorine pesticides such as DDT are still detected in many streams today - >20 years after their use was prohibited. • Nationally, levels of most organochlorine pesticides in fish have declined since 1960s. • Atrazine was detected in nearly every water sample collected in an agricultural watershed!

42. Relative Levels of Contamination in Streams (from NAWQA)

43. White River Basin National Water Quality Assessment Program (NAWQA)