The following is a brief description of the columns in the irvineetaldata.cvs file

STRM.ID 	The ID number for each sampled stream
SO4		sulfate concentration measured at each sample location
STATE   	state where stream located
COUNTY		county where stream located
LAT.DD		latitude in decimal degrees
LON.DD		Longitude in decimal degrees
RUNOFF.M	Mean runoff for each contributing watershed
PRECIP.M	mean precipitation for each contributing watershed
ASPCTDEG	aspect in degrees
WSAREA		area of the contributing watershed 
ELEV.X		elevation
SLOPEMAX	maximum slope for each watershed
SLOPMEAN	mean slope for each watershed
URB.NLCD	Percent urban for each contributing watershed
AG.NLCD		Percent agriculture for each contributing watershed
FOR.NLCD	Percent forest for each contributing watershed
MINENLCD	Percent mining for each contributing watershed
PCT.SO4AD	Percent located within ecoregions with high sulfate adsorption soils
lnSO4		ln sulfate concentration
X.coor		transformed coordinate see Irvine et al 
Y.coor		transformed coordinate see Irvine et al 
Elevation	Elevation for each stream location
SO4wetdep	predicted wet sulfate deposition