RIVERS: Major Components 1) water 2) suspended inorganic matter - major elements are Al, Fe, Si, Ca, K, Mg, Na and P 3) dissolved major spp. - HCO 3 -, Ca 2+, SO 4 2-, H 4 SiO 4, Cl -, Na +, Mg 2+,K + a) no gaseous phase - Ca 2+, Cl -, H 4 SiO 4, Na +, Mg 2+,K + b) with gaseous phase - HCO 3 -, SO ) dissolved nutrient elements - N, P - Si 5) suspended and dissolved organic matter 6) trace metals

Runoff ratio - avg. river runoff / avg. rainfall World average Thus, 50% of rainwater returned to atmosphere by evaporation

Major dissolved components: CHLORIDE in rocks very soluble - not reactive with other ions - good tracer of water mass 1) main source to river - sea salt - rain - dry fallout 2) dissolved during weathering of halite (NaCl) evaporites 3) thermal and mineral springs in volcanic areas 4) saline crusts in desert basins (not primary) 5) pollution - oil well brines, road salt, sewage

SODIUM - seawater input to atmosphere; Na in halites - sedimentary rock - brine, road salts, etc. POTASSIUM 1) 90% weathering of silicate minerals - feldspar, orthoclase, mica (biotite) 2) 3/4 sedimentary rocks 3) 1/4 igneous and metamorphic (also fertilizer)

CALCIUM & MAGNESIUM - rock weathering 1) Ca - carbonate rocks: calcite(CaCO 3 ), dolomite(CaMg(CO 3 ) 2 ) 2) 65% of Ca 2+ in river water -- dolomite is main source of Mg

HCO rock weathering 1) soils: CO 2 + H 2 O + CaCO 3 ---> Ca HCO 3 - 2) soils: 2CO H 2 O + 2NaAlSi 3 O 8 ---> 2Na + + 2HCO Al 2 Si 2 O 5 (OH) 4 + 4H 4 SiO 4 3) some weathering by sulfuric acid formed by oxidation of pyrite: H 2 SO 4 + 2CaCO 3 ---> 2Ca HCO SO 4 2- H 2 SO 4 + 9H 2 O + NaAlSi 3 O 8 ---> 2Na + + SO Al 2 Si 2 O 5 (OH) 4 + 4H 4 SiO 4

SILICA - silicate weathering 1) 20% Si relative to HCO 3 - (carbonate weathering dominant) 2) 8% chert in carbonate rocks 3) more dissolved silica in tropics -- 4) Si minerals weather to kaolinite times dissolved Si versus smectite in temperate systems; gibbsite even more in tropics 5) biogenic source not important as in oceans

SULFATE - 1) 2% from salt, 33% weathering, 54% pollution, 8% volcanic, 3% biological 2) pyrite FeS 2, gypsum CuSO 4 · H 2 O, anhydrite CuSO 4 3) FeS 2 weathers to H 2 SO 4 which then reacts with Si and Ca minerals 4) pyrite - derived SO 4 2- in river water

Organic Carbon: Average river dissolved organic carbon (DOC) mg/l; global is 200Tg DOC/yr (avg. global DOC/total dissolved substances (TDS) - 1:19) POC Tg/yr; on average 1% of TSS is CARBON TOC = POC + DOC

Black Water River - pH is 4.3 due to dissociation of humic carboxyl groups (R-COOH)--->(R-COO) - + H + DOC 24 mg/l -- DOC (humics and fulvics) / TDS -- 1:1 HCO 3 - is low HCO H + ---> H 2 O + CO 2 (R-COOH) + HCO > (R-COO) - + H 2 O + CO 2 High DOC rivers also have high Fe and Al Using total concentration of dissolved ions in river water one can calculate the chemical denudation rate of a drainage basin, continent - even the whole world.

Nutrients Atmospheric Nutrients: C, N, P, S, S, K, Mg, Na, Ca, Fe, Mn, Zn, Cu, Mo, Co, B macronutrients, micronutrients NITROGEN - oxid-states - NO 3 -, (+5 state) (of N) to NH 4 +, (-3 state) (of N) organic N highly reduced; urea, amino acids PHOSPHORUS - PO 4 3- (+5 state) (of P) 3 structural configurations - ortho, para, meta. However, can occur in (+4 state) = PO 4 2-

SILICON detrital quartz - crystalline silica, aluminosilicate clays, dissolved silicon oceans > opal - biogenic silica - amorphous silica polymer silicic acid - H 4 SiO 4 SiO 4 2- (+4 state)

There is significant competition for nutrients between bacteria and algae Uptake kinetics - organisms with a half- saturation coefficient (k s ) for a given nutrient will have greater affinity for that nutrient Organisms with large k s can take greater advantage of large pools

Plant Redfield Ratio (1934) - C:N:P - 106:16:1 Redfield uptake of N, P - 16:1 ratio Phytoplankton organic matter 106 CO H 2 O + 16 HNO 3 + H 3 PO 4 ---> C(H 2 O) (NH 3 ) 16 + H 3 PO O 2

Nutrient regeneration via decomposition will return N 2 fixation - 78% of atmospheric N 2 bacteria and cyanobacteria “fixing” N 2 into the inorganic salt ammonium N 2 + 3H 2 ---> 2NH 3 Nitrogenase inhibited by oxygen Heterocysts - maintain anoxic conditions

Clostridium, Azobacter, Pseudomonas Heterocystic cyanobacteria - Trichodesmium, Oscillatoria, Calothrix P enhances N 2 fixation, inhibited by NH 4 + can use acetylene reduction 15 N - labelled N 2 Nitrogen fixation - high in lakes, not in estuaries 1) NH 4 + inhibited, or: 2) SO 4 may inhibit uptake of molybdate - needed to make nitrogenase Important in marshes, ~5% of NH 4 + needed for Spartina growth

Nitrification and Denitrification: Nitrification - oxidation of NH 4 + to NO 3 - under aerobic conditions Nitrifying bacteria use NH 4 + as energy source to fix CO 2 into organic matter

Nitrification - 2 steps: Nitrosomonas, Nitrocystis NH 4 + 3/2 O 2 ---> HNO 2 + H 2 O Nitrobacter - HNO 2 + 1/2 O 2 ---> HNO 3 can measure with 15 N - labeled NH 4 + substrate sewage outfalls - high nitrification rates -- due to NH 4 + concentrations

Denitrification - bacteria use NO 3 - as e - acceptor to oxidize organic matter anaerobically, releasing N 2 gas 5C 6 H 12 O HNO 3 ---> 30CO H 2 O + 12N 2 Pseudomonas - also, N O produced in reaction C 6 H 12 O 6 + 6HNO 3 ---> 6CO 2 + 9H 2 O + 3N 2 O denitrification - limited by NO 3 -