Discrete data for trace elements for both the dissolved and acid available fractions for thirteen core sites in the Humber catchment over the period 1993 to 1997 and for three sites from the Tweed catchment over the period 1994 to 1997. Part of the Land Ocean Interaction Study project (LOIS). Trace elements measured were: Aluminium (Al), Antimony (Sb), Arsenic (As), Barium (Ba), Beryllium (Be), Boron (B), Cadmium (Cd), Cerium (Ce), Chromium (Cr), Cobalt (Co), Copper (Cu), Gadolinium (Gd), Iron (Fe), Lanthanum (La), Lead (Pb), Lithium (Li), Manganese (Mn), Molybdenum (Mo), Neodymium (Nd), Nickel (Ni), Rubidium (Rb), Samarium (Sm), Scandium (Sc), Strontium (Sr), Tin (Sn), Uranium (U), Yttrium (Y), Zinc (Zn). The Core sites were sampled at regular weekly intervals and more intermittently during high flows (on average an extra sampling once a month per site). The Swale sites were sampled during hydrological events and the Aire sites were sampled both weekly and during hydrological events. The majority of samples were obtained using a wide neck grab sampler. Those samples collected from the Aire during hydrological events were obtained using EPIC automatic samplers. Both dissolved and acid available trace element fractions were determined for all samples. The dissolved fraction was measured by filtering samples and acidifying the filtrates with concentrated aristar grade nitric acid (1%vv) on the same day of sampling. The acid available fraction was determined by acidifying an unfiltered sample as above and agitating for 24 hours, at room temperature, prior to filtration. Samples were then analysed by inductively coupled plasma optical emission spectrometry (ICP-OES: B, Ba, Fe, Mn, Sr) and mass spectrometry (ICP-MS: Al, As, Be, Cd, Ce, Co, Cr, Cu, Gd, La, Li, Mo, Nd, Ni, Pb, Rb, Sb, Sc, Sm, Sn, U, Y, Zn). Full details about this dataset can be found at https://doi.org/10.5285/69f62656-567c-42dd-bb65-8f0cbbeb1693