Mapping of Nitrate Reduction Capacities on a Small Scale: Lundgårds Bæk Catchment Area

Voutchkova, Denitza

4. term

Water and Environmental Engineering , Master

2011

2011-06-07

113

Dette speciale undersøger og udvikler en praktisk måde at estimere nitratreduktionskapaciteten i et lille, landbrugsdomineret opland med et først‑andet ordens vandløb (Lundgårds bæk). Til arealforvaltning kan mere detaljerede, lokale kort være økonomisk mere effektive end det eksisterende nationale, grove kort over nitratreduktionspotentiale. Specialets mål er at: forstå, hvordan nitrat bevæger sig og omdannes i Lundgårds bæk‑oplandet; udvikle en metode til at estimere nitratreduktionskapacitet på deloplandsniveau; og identificere og kortlægge kritiske zoner, der bidrager til vandløbets nitratforurening. Resultaterne viser, at høje NO3- koncentrationer i Lundgårds bæk primært skyldes NO3- forurenet grundvand, og at koncentrationerne varierer markant langs forskellige dele af vandløbet. Det nye kort over nitratreduktionskapacitet indikerer, at kun omkring 30% af oplandet har mindre end 80% NO3- reduktionskapacitet, mens det nationale kort klassificerer hele oplandet i zonen med 50–75% reduktionspotentiale. Kortlægningen af kritiske zoner viser desuden, at udvaskning fra cirka 80% af oplandet ikke påvirker vandkvaliteten i vandløbet.

This thesis explores and develops a practical way to estimate the nitrate reduction capacity of a small, agriculture‑dominated catchment with a first–second order stream (Lundgårds bæk). For land‑use management, more detailed local maps can be more cost‑efficient than the existing nationwide, coarse map of nitrate reduction potential. The thesis aims to: understand how nitrate moves and is transformed within the Lundgårds bæk catchment; develop a method to estimate nitrate reduction capacity at sub‑catchment scale; and identify and map critical zones that contribute to nitrate pollution of the stream. Results show that high NO3- concentrations in Lundgårds bæk are mainly caused by NO3- contaminated groundwater, and that concentrations vary markedly along different parts of the stream. The new nitrate reduction capacity map indicates that only about 30% of the catchment has less than 80% NO3- reduction capacity, whereas the national map classifies the entire catchment within a 50–75% reduction potential zone. Mapping of critical zones further shows that leaching from roughly 80% of the catchment does not affect the stream’s water quality.

[This abstract was generated with the help of AI]

Nitrate Reduction ; GSI

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