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All DOC is not the same : DOC classified by functional properties and their environmental significance Andy Baker University of Birmingham

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1 All DOC is not the same : DOC classified by functional properties and their environmental significance Andy Baker University of Birmingham

2 The microbial loop. Fenchel, doi: /j.jembe Battin et al. doi: /ngeo618

3 (In predominantly natural systems) Evidence of DOC processing within rivers. DOC becomes increasingly ‘young’ in 14 C age and hydrophilic with distance from source. Rivers evade CO 2. Photodegradation and biodegradation occurs, arguably of all DOM fractions. Seasonal variations in riverine DOM character, typically a hydrophobic / aromatic ‘flush’. Differences in DOM character between catchments, depending on soil type, land cover and human impact. Evidence of greater variability in DOC characteristics in headwaters and low order streams with ‘fresh’ DOM. Downstream DOC might be 14 C ‘young’, but it is more homogenous and biogeochemically ‘aged’. Anthropogenic inputs typically introduce hydrophilic, relatively colourless, DOC. Clear links between DOC character and function. Aromatic DOC has greater chemical and ecological function (metal binding, contaminant binding, UV screening), and is easy to treat. Hydrophilic DOC difficult to remove during drinking water treatment.

4 Variable and high fluorescence / g C in bog waters Less variable and less fluorescent / g C river waters IHSS standards have atypically low fluorescence Time / Processing Peak C fluorescence

5 Mean and standard deviation colour/DOC CB weir 10.7 (1.4) P weir 10.0 (1.2) PG weir 8.4 (2.5) MEME 10.8 (3.7) MCMC 9.5 (0.8) FEFE 12.4 (3.7) FCFC 11.5 (2.0) ‘fresh’ DOC is more coloured Different DOC character between sub-catchments ‘fresh’ DOC is more fluorescent per unit absorbance

6 Photodegradation of lignin over two months Lignin phenol concentration and relationship with optical characteristics through the ‘wet’

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9 Summary River microbial ecosystem processes DOC. Aromatic bonds in DOC relatively easier to break. DOC therefore less aromatic with residence /travel time. Easily measured ‘in-situ’ using UV absorbance or fluorescence. River experience seasonal variations in riverine DOC character. Typically with ‘flush’ of relatively fresh (therefore aromatic) DOC. Groundwater rivers will have a groundwater hydrophilic DOC source. Catchment mean DOC character depending on soil type, land cover and human impact. Evidence of greater variability in DOC characteristics in headwaters and low order streams with ‘fresh’ DOM; variability decreases downstream as this is processed. Anthropogenic inputs typically introduce relatively hydrophilic, colourless, DOC. Aromatic DOC has greater chemical and ecological function (metal binding, contaminant binding, UV screening), and is easy to treat. Hydrophilic DOC difficult to remove during drinking water treatment.

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