Atmospheric nutrient inputs to the northern levantine basin from a long-term observation: sources and comparison with riverine inputs

[摘要] Aerosol and rainwater samples have been collected at a rural site located onthe coastline of the Eastern Mediterranean, Erdemli, Turkey between January1999 and December 2007. Riverine sampling was carried out at five Rivers(Ceyhan, Seyhan, Göksu, Berdan and Lamas) draining into the NortheasternLevantine Basin (NLB) between March 2002 and July 2007. Samples have beenanalyzed for macronutrients of phosphate, silicate, nitrate and ammonium(PO₄³⁻, Si_diss, NO₃⁻ and NH₄⁺). Phosphateand silicate in aerosol and rainwater showed higher and larger variationsduring the transitional period when air flows predominantly originate fromNorth Africa and Middle East/Arabian Peninsula. Deficiency of alkalinematerial have been found to be the main reason of the acidic rain eventswhilst high pH values (>7) have been associated with high Si_dissconcentrations due to sporadic dust events. In general, lowest nitrate andammonium concentrations in aerosol and rainwater have been associated withair flow from the Mediterranean Sea. Comparison of atmospheric with riverinefluxes demonstrated that DIN and PO₄³⁻ fluxes to NLB have beendominated by atmosphere (~90% and ~60% respectively)whereas the input of Si was mainly derived from riverine runoff (~90%).N/P ratios in the atmospheric deposition (233); riverine discharge(28) revealed that NLB receives excessive amounts of DIN and this unbalancedP and N inputs may provoke even more phosphorus deficiency. Observed molarSi/N ratio suggested Si limitation relative to nitrogen might cause a switchfrom diatom dominated communities to non-siliceous populations particularlyat coastal NLB.

[学科分类] 地球化学与岩石