Pamene milingo yayikulu ya trace element molybdenum (mah-LIB-den-um) idapezeka m'zitsime zamadzi akumwa kumwera chakum'mawa kwa Wisconsin, malo ambiri otayira phulusa la malasha akuwoneka kuti ndi omwe angayambitse vutoli.

Koma ntchito yofufuza bwino kwambiri yotsogozedwa ndi ofufuza ochokera ku Yunivesite ya Duke ndi The Ohio State University yawulula kuti maiwe, omwe ali ndi zotsalira za malasha omwe amawotchedwa m'mafakitale amagetsi, siwomwe adayambitsa kuipitsidwa.

Zimachokera ku magwero achilengedwe m'malo mwake.

"Kutengera mayeso ogwiritsira ntchito forensic isotopic 'fingerprinting' ndi njira zopezera zaka, zotsatira zathu zimapereka umboni wodziyimira pawokha kuti phulusa la malasha silinayambitse kuipitsidwa m'madzi," adatero Avner Vengosh, pulofesa wa geochemistry ndi mtundu wamadzi ku Duke's Nicholas School of chilengedwe.

"Madzi ochuluka a molybdenum akadachokera ku phulusa la malasha, akadakhala aang'ono, atalowetsedwanso m'madzi apansi a m'derali kuchokera ku phulusa la malasha zaka 20 kapena 30 zapitazo," adatero Vengosh. "M'malo mwake, mayeso athu akuwonetsa kuti amachokera pansi pansi ndipo ali ndi zaka zopitilira 300."

Mayesowa adawonetsanso kuti chala chamadzi oipitsidwa ndi isotopic - kuchuluka kwake kwa boron ndi strontium isotopes - sikunafanane ndi zala za isotopic za zotsalira za malasha.

Zomwe anapezazi "zimagwirizanitsa" molybdenum kuchokera kumalo otayira phulusa la malasha ndipo m'malo mwake zimasonyeza kuti ndi zotsatira za zochitika zachilengedwe zomwe zimachitika mu thanthwe la aquifer, adatero Jennifer S. Harkness, wofufuza za postdoctoral ku Ohio State yemwe adatsogolera kafukufukuyu monga gawo. za dissertation yake ya udokotala ku Duke.

Ofufuzawa adasindikiza pepala lowunikiridwa ndi anzawo mwezi uno m'magazini ya Environmental Science & Technology.

Molybdenum wochepa kwambiri ndi wofunikira kwa zinyama ndi zomera, koma anthu omwe amamwa kwambiri amatha kukhala ndi mavuto monga kuchepa kwa magazi m'thupi, kupweteka kwa mafupa ndi kunjenjemera.

Zina mwa zitsime zomwe zidayesedwa kum'mwera chakum'mawa kwa Wisconsin zinali ndi ma micrograms 149 a molybdenum pa lita, kupitilira pang'ono kuwirikiza kawiri muyezo wakumwa wotetezeka wa World Health Organisation, womwe ndi ma microgram 70 pa lita. Bungwe la US Environmental Protection Agency limaika malire otsika kwambiri pa ma microgram 40 pa lita imodzi.

Kuti achite kafukufuku watsopanoyu, Harkness ndi anzake adagwiritsa ntchito zowunikira kuti adziwe kuchuluka kwa boron ndi strontium isotopes m'madzi aliwonse. Anayezanso zitsanzo za tritium ndi helium radioactive isotopu, zomwe zimakhala ndi mitengo yowola nthawi zonse ndipo zitha kugwiritsidwa ntchito kuyesa zaka zachitsanzo, kapena "nthawi yokhala" m'madzi apansi. Mwa kuphatikiza magulu awiriwa a zomwe apeza, asayansi adatha kuphatikizira mwatsatanetsatane mbiri yamadzi apansi panthaka, kuphatikiza pomwe adalowa m'madzi, ndi mitundu ya miyala yomwe idalumikizana nayo pakapita nthawi.

"Kufufuza kumeneku kunawonetsa kuti madzi a molybdenum apamwamba sanachokere ku phulusa la malasha pamwamba pake, koma adachokera ku mchere wochuluka wa molybdenum mu matrix a aquifer ndi chikhalidwe cha chilengedwe m'madzi akuya omwe amalola kuti molybdenum iyi itulutsidwe m'madzi. madzi apansi,” anafotokoza motero Harkness.

"Chosiyana kwambiri ndi kafukufukuyu ndikuti chimaphatikiza njira ziwiri zosiyana - zolemba zala za isotopic ndi zaka - kukhala phunziro limodzi," adatero.

Ngakhale kuti kafukufukuyu adayang'ana pa zitsime zamadzi akumwa ku Wisconsin, zomwe adapeza zitha kugwiritsidwa ntchito kumadera ena omwe ali ndi ma geologies ofanana.

Thomas H. Darrah, pulofesa wothandizira wa sayansi ya dziko ku Ohio State, ndi mlangizi wa postdoctoral wa Harkness ku Ohio State ndipo anali wolemba nawo kafukufuku watsopano.