Modelling long-term acidification trends of forested sandstone catchments in the Black Forest (SW Germany)

An extensive database from eight Triassic (Bunter) sandstone catchments in the Black Forest, SW Germany, was used to apply the MAGIC model and simulate long-term acidification trends. Using the ion ratio (Ca+Mg)/(SO₄+NO₃) as criterium (values< 1.5=" indicate=" an=" acidified=" state),=" hindcast=" simulations=" showed=" that=" the=" brooks=" of=" three=" catchments=" have=" reached=" values="><1.5, three=" catchments=" are=" approaching=" 1.5,=" and=" two=" catchments=" (carbonate=" bearing=" upper=" bunter)=" are=" still=" well=" above=" this=" limit.=" the=" different=" acidification=" state=" of=" the=" catchments=" is=" mainly=" caused=" by=" the=" amount=" of=" acidic=" deposition=" and=" bedrock=" geology.=" other=" differences=" (shallow=" or=" deep=" groundwater=" circulation,=" sulphate=" sorption=" and=" soil=" parameters)=" are=" less=" significant.=" to=" simulate=" the=" future=" evolution,=" three=" scenarios=" were=" tested:=" a=" pessimistic,=" an=" optimistic=" and=" a=" most=" probable=" case.=" the=" latter=" leads=" to=" a=" still=" progressing=" but=" decelerated=" acidifcation=" in=" the=" next=" 100=" years.=" in=" the=" pessimistic=" case,=" acidification=" rates=" will=" be=" accelerated=" in=" two=" of=" the=" catchments.=" even=" in=" the=" optimistic=" case,=" the=" initial=" state,=" prior=" to=" acidification,=" cannot=" be=" restored=" up=" to=" the=" year=" 2130.=" however,=" the=" forecasting=" of=" the=" future=" evolution=" is=" still=" markedly=" hampered=" by=" the=" significant=" uncertainty=" in=" the=" evaluation=" of=" nitrogen-driven=" acidification,=" a=" process=" which=" today=" already=" predominates=" in=" parts=" of=" the=" black=">