Diffuse Water Pollution (nutrient & pesticides) Flashcards
Release of potential pollutants
range of activities, no individual effect to water
Catchment scale
significant impact, water quality problems, wildlife
Cancers
agriculture practice, fertilizers & pesticides, urban surface run-off
Eutrophication (nutrient enrichment): Effects
issue with N and P, urban source, agricultural fertilizers
health impacts
nitrate controls, methaemoglobinaemia (blue baby) - rare, nitrite - stomach cancer “nitrosamines”, NO3- -> NO2- -> NH2
Natural succesion
water progress, oligotrophic -> eutrophic
Geomorphological (land/water resulting from chemical/physical processes)
in-fill, terrestrial succesion
Eutrophication discussion
cultural, accelerated, enhancement of process
Symptoms: Nutrient enrichment
not precise
Symptoms: Parameters
more subjective, less objective, weather, season, sample collection
Limiting Nutrient Concept: Law of minimum
Photosynthethic growth continues until one necessary contributing parameter falls below minimum requirement
CO2 + H2O -> CH2O + O2
needs light, trace metals Fe, Mn, Cu, others
N or P limiting
add supply - photosynthetic growth occurs
N or P addition
alter growth rate, certain plant/algae, balance affected
Assessment : N or P limitation? 2 parameters
N - as nitrate, nitrite & ammonium N>20microg/l, P - SRP in H2O >5microg/l. Check during normal growth period
N:P ratio measure
Red field ratio 16:1 (molar) or 7:1 (mass). If ratio >16, P limitation (excessive N)
N transport to rivers
soluble, mobile, transport from catchment effective, leaching
P transport to rivers
low mobility, high partition coefficient (Kd), adsorbed to particles (clay), bonded to Fe
Kd = [Mp]/[Md] stick to particles
[Md] -> [Mp]
Phosphorus Cycling: Large supply
particulate form, discharge/input in dissolved form (SRP)
Phosphorus Cycling: Re-solubilisation
local microenvironment, very rapid re-utilisation
Phosphorus Cycling: Redox <200 mV
Release Fe-bound P
Phosphorus Cycling: Increase pH
P binding by Al, Fe pH decrease, P binding by Ca pH increases
Phosphorus Cycling: Increase temperature
microbe activity increase temp, redox/pH reactions temp decreases
Nitrogen Cycling
NO3- NO2- NH4+ goes to N2 (lost from H20 to atm) goes to org-N (denitrfication) goes back (nitrification
N recycling
décaying matter 80%
Nitrfication
nitrogen fixation, cyanobacteria
Denitrification
anaerobic processes, even in small O2 amount due to O2 diffusion rate in sediment
Pesticide
Any substance, preparation or organism prepared or used for destroying any pest. E.g. herbicide, fungicide, insecticide
Agrochemicals
some inorganic (Cu, H2SO4), thousands of organic compounds
Insecticides
organochlorines (OC’s): persistent, DDT, dieldrin, lindane
Organophosphates (OP’s)
highly toxis to humans, parathion, carbomates
Concerns
toxicity (specific), persistence, bioaccumulation
Controls: Usage
quantity (episodes/products), practice (application rate/ timing), management (drainage control/ soil cultivation)
Controls: New developments
High octanol-water partition coefficient Kow >10, low persistence <20 mg/l
Controls: Formulation advances
Controlled release, container - sprayer connections
Controls: Waste control
tank/container washings, low-drift nozzles, buffer strips
Buffer Strips
1-2m wide, trap leached pollutants, bioreactor zones, efficiency?
