Table 1.

Summary of modeled and observed THg, DHg, and PHg fluxes for the 10 largest Arctic rivers generating 80% of the THg flux to the AO

River	Discharge,* km3 y−1	Area,* 103 km2	THg mod, Mg y−1	DHg mod, Mg y−1	PHg mod, Mg y−1	THg obs,† Mg y−1	DHg obs,† Mg y−1	PHg obs,† Mg y−1	THg obs/mod‡	DHg obs/mod‡	PHg obs/mod‡
Yenisei	606	2533	5.8	2.8	2.8	5.2	3.7	1.5	0.9	1.3	0.5
Lena	534	2453	4.8	2.3	2.4
Ob	411	2522	2.5	1.1	1.4
Mackenzie	285	1671	2.2	1.0	1.1	2.4	0.7	1.8	1.1	0.6	1.5
Pechora	143	324	1.7	0.9	0.8
Khatanga	139	437	1.6	0.8	0.8
S. Dvina	110	368	1.2	0.6	0.6	1.2	0.5	0.7	1.0	0.9	1.2
Kolyma	116	627	0.93	0.44	0.48
Taz	54.7	167	0.60	0.30	0.29
Indigirka	54.5	329	0.37	0.17	0.20
Mean									1.0	0.9	1.1
1σ§									0.1	0.3	0.5
Yukon¶	203	850	2.0	1.0	1.0	4.4	0.6	3.8	2.2	0.6	4.0

mod, modeled; obs, observed.

^*Discharge and watershed area at the river mouth are from Dai and Trenberth (24).

^†Observed fluxes are mean values for the years of observation.

^‡Mean observed/modeled ratios suggest the regression model (Eqs. 1–6) to be unbiased with respect to observations.

^§1σ SDs are suggested to represent multiannual model uncertainty.

^¶The Yukon River, running off into the Bering Sea, is shown separately to illustrate its anthropogenic observed/modeled PHg ratio of 4.