Comparison of Two PARAFAC Models of Dissolved Organic Matter Fluorescence for a Mid-Atlantic Forested Watershed in the USA

Table 1

Descriptions of the six PARAFAC identified components for the EEM dataset of Fair Hill site and their comparison with previously reported studies.

Components; (Ex/Em in nm)	Designated peaks/components in previous studies*	Descriptions	Sources/environments reported in previous studies
FH1 (<250 [330]/460)	C2^1, A peak^3, C1^4, C1^5, C1^6, C1^7, C3^8, C1^9	Humic-like/unknown/UVC-humic-like/fulvic-like	Both terrestrial and marine [34]; both oxidized and reduced [17]; river, estuarine, and near-shore marine ecosystems; common to wetlands/forest streams [35]; terrestrial humic origin [36]; terrestrially derived OM, highest concentration in forest streams and wetlands [19]; observed in bay coastal areas in surface waters, low at the bottom [3]
FH2 (<250 [310]/400)	C6^1, Q3^4, C4^5, C3^6, C4^7, C4^8, C3^9	Unknown-nonhumic/quinone-like (lawsone)/humic-like	Microbial origin, aliphatic C; oxidized environment [17]; river, estuarine, and near-shore marine ecosystems; aliphatic C [35]; labile matter; biological production in the water column [36]; combination of N and T peaks, autochthonous and biologically labile component [3]; microbial origin [37]
FH3 (<250 [410]/512)	C5^1, D region^2, SQ1^4, C3^5, C4^6, C2^8, C2^9	Soil-fulvic-like/semi-quinone-like/humic-like	Black Sea [10]; aromatic C; reducing conditions; higher plant matter [17]; river, estuarine, and near-shore marine ecosystems; higher aromatic content [35]; derived from agricultural catchments and exists in fresh water environments [36]; terrestrial origin, biogeochemical processing of terrestrial POM [3]
FH4 (<250 [370]/460)	C1^1, C peak^3, SQ2^4, C2^5, C2^6, C3^7, C5^8, C4^9	Humic-like/semi-quinone-like/; Humic-like	Both terrestrial and marine [34]; microbial origin; reducing conditions [17]; river, estuarine, and near-shore marine ecosystems; high molecular weight/aromatic [35]; terrestrial humic origin, related to terrestrial particulate organic matter [36]; high molecular weight fraction of terrestrially derived humic matter, common to wide range of fresh water environments [19]; terrestrial origin [3]; microbial humic [37]
FH5 (280/328)	C7^1, T peak^3, C8^4, C7^5, C5^7, C7^8, C5^9	Protein-like (tryptophan)/UVB protein-like (tryptophan)	Both terrestrial and marine [34]; microbial origin [17]; river, estuarine and near-shore marine ecosystems; free-tryptophan-like [35]; combination of N and T peaks, labile matter, autochthonous DOM [19]; tryptophan-like, blue shifted from authentic tryptophan, autochthonous, biologically labile [3]; freshly produced tryptophan-like DOM [37]
FH6 (270/312)	B peak^3, C13^4, C8^5, C8^8	Protein-like (tyrosine)	Both terrestrial and marine [34]; River, estuarine, and near-shore marine ecosystems; free-tyrosine-like [35]; tyrosine like, degradation processes important for the dynamics of this component [3]

∗[38]¹, [10]², [34]³, [17]⁴, [35]⁵, [36]⁶, [19]⁷, [3]⁸, [37]⁹.