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GENERAL INFORMATION
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1. Title of Data set: Throughfall and litterfall micronutrient and trace element concentrations and fluxes at six temperate forest sites (VA, MD, PA, MA, VT, NH USA)

Current Author information:
Justin B. Richardson
University of Virginia
Justin.richardson@virginia.edu

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DATA & FILE OVERVIEW
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CSV files of:
Throughfall concentrations for micronutrient and trace elements
Throughfall fluxes for micronutrient and trace elements
Litterfall concentrations for micronutrient and trace elements
Litterfall fluxes for micronutrient and trace elements

Micronutrient and trace elements include Vanadium (V), Chromium (Cr), Cobalt (Co), Nickel (Ni), Copper (Cu), Zinc (Zn), Gallium (Ga), Arsenic (As), Strontium (Sr), Molybdenum (Mo), Cadmium (Cd), Barium (Ba), Tungsten (W), Lead (Pb), Thorium (Th), and Uranium (U).


Units are included in the second row

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METHODOLOGICAL INFORMATION
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Field study sites
Six field sites were created in 2018 to investigate element cycling along a 6 ° latitude gradient (38° N to 44° N) along the Appalachian mountains of the eastern US. 
Each site was 600 m2 plots in which trees, soils, and aboveground processes were studied. Sites are hardwood aboveground vegetation, with minimal modern management post 1960, and are at physiographic montane positioning. 
The sites are state or privately-owned forests and land-use history has determined their ages to be similar, 60 - 80 years of limited management following reforestation from clear-cutting or pasture land. 
Each site is at least 30 km from metropolitan areas and known point-source metal pollutant sources to limit surrounding anthropogenic disturbance to focus on non-point source pollution.

Site Name	 		Site #	Lat	Long	Soil Series
Mt. Moosilauke			Site 1	43.97	-71.81	Monadnock
Mt. Ascutney			Site 2	43.42	-72.46	Glover-Vershire complex
Macliesh Field Station		Site 3	42.45	-72.68	Chatfield-Hollis complex
Tobyhanna State Forest		Site 4	41.21	-75.39	Morris
Green Ridge state Forest	Site 5	39.63	-78.48	Berks
Lesesne State Forest 		Site 6	37.84	-78.96	Thurmont

Throughfall concentration and flux methodology
Four throughfall collectors were deployed at each site to capture atmospheric inputs of elements. 
An acid washed 20-liter vessel has secured to the ground and had a circular funnel (diameter = 10.2 cm) from the sealed lid at 50 cm height. 
Fiber glass mesh covers to top of the funnel, preventing debris > 1 mm from entering. 
The four throughfall collectors were emptied twice a year, once in April-May for winter throughfall and again in October and November for growing season throughfall. 
The total volume of throughfall collected was weighed in the field and one representative 1-L subsample is returned to laboratory to be filtered < 0.2 µm, oxidized with H2O2 to remove any organics, and acidified to pH 1 with 15.8 M HNO3. 
Due to their low concentrations, throughfall solutions were analyzed for trace elements (As, Cd, Cr, Co, Cu, Ni, Pb, W, Zn, and U) with an Agilent 7700x Inductively Coupled Plasma-Mass Spectrometer. TMMs in the preparation blank were < 0.01 ng/g and all duplicates were within 6 % CV.    

Litterfall concentration and flux methodology
Sites 1, 2, and 3 are predominantly northern hardwoods, predominantly American beech (Fagus grandifolia), birches (Betula nigra, Betula papyrifera), sugar maple (Acer sac-charum), red maple (Acer rubrum) and black cherry (Prunus serotina). 
Dominant tree species of the Sites 4, 5, and 6 are predominately red oaks (e.g. Quercus rubrus), white oaks (e.g. Quercus montana), hickory (Carya spp,) yellow poplar (Liriodendron tulipifera) and sassafras (Sassafras albidum). 
All trees within the 600 m2 site were identified and measured for DBH.
Four litterfall traps were deployed at each of the six study sites. 
Litterfall traps were 1.2 m tall and 0.9 m x 0.9 m PVC pipes with plastic mesh (1 cm mesh) to collect foliage and woody debris. 
Litterfall trap nets were serviced in May and June and emptied in October and November, with the varying timeframe due to differences in leaf out and fall senescence timing along the climate gradient. 
Litter collections were completed in 2018, 2019, 2020, 2021, and 2022. Litterfall were sorted by tree species or genera, dried to a constant weight, and then weighed to determine total litterfall fluxes as mass per unit area with the four collection traps. 
Foliage and woody debris subsamples were analyzed for micronutrient and pollutant metals using a modified EPA 3050B method. 
Leaves were ashed at 450 ºC for 6 hrs and then digested using 5 mL of reverse aqua regia (9:1 ratio of 15.7 M HNO3: 11.6 HCl) and digested at 80 °C for 1 hr then diluted to 50 mL using 18.2 M? DI water. 
Litterfall digest dilutions were analyzed for pollutant elements using an Agilent 5110 Inductively Coupled Plasma-Optical Emission Spectrometer (Agilent Technologies, Santa Clara, California, USA). 
Copper, Cd, Pb, and Zn concentrations in the preparation blank were < 0.001 mg/kg and all duplicates were within 6 % CV Recovery for TMMs in NIST 2709a and 2710a by pseudototal digestion was 80 to 105% of their certified values.