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Saray bagyon dabok so seryoson peligro ed dakel a bansa ed interon mundo lapud makaderal ya epekto ra ed agrikultura, bunigas na too, transportasyon tan imprastraktura. Lapud saya, say erosion na dagem et ipapasen ya sankamundoan ya problema. Sakey ed saray paraan ya makaderal ed kaliberliber pian naprebentaan so erosion na dagem et say pangusar na microbial induced carbonate precipitation (MICP). Balet, saray by-product na urea-degradation-based MICP, singa say ammonia, et aliwan maabig no dakel so nagawa. Sayan impanaral et mangipaparungtal na duaran pormulasyon na calcium formate bacteria parad pakaderal na MICP ya ag makapawala na urea tan komprehensibon ikompara so performance da ed duaran pormulasyon na aliwan mamapawala na ammonia ya calcium acetate bacteria. Saray bakterya ya ikonsidera et Bacillus subtilis tan Bacillus amyloliquefaciens. Unona, nadetermina so sankaabigan iran balor na saray bengatla ya mangokontrol ed inkaporma na CaCO3. Saray wind tunnel test et ginawa ed saray sample na sand dune ya inikdan na saray optimized ya pormulasyon, tan sinukat so resistensya na dagem, stripping threshold velocity, tan resistensya na sand bombardment. Saray calcium carbonate (CaCO3) allomorphs et inebalwar ya inusar so optical microscopy, scanning electron microscopy (SEM), tan X-ray diffraction analysis. Saray pormulasyon ya based calcium formate et mas maong so performance da nen saray pormulasyon ya based acetate no nipaakar ed panagporma na calcium carbonate. Niarum ni, say B. subtilis et mas dakel so napapawala ton calcium carbonate nen say B. amyloliquefaciens. Malinew ya impanengneng na SEM micrographs so pankakasakey tan pan-imprinta na aktibo tan ag-aktibo iran bakterya ed calcium carbonate ya sengegan na sedimentation. Amin ya pormulasyon et makabawas na maong ed erosion na dagem.
Say erosion na dagem et abayag lan bibidbiren bilang manunan problema ed saray amagan tan semi-arid a rehyon a singa say abalaten-sagur na Estados Unidos, mamasagur a Tsina, Saharan Africa, tan maslak a parte na Pegley Bukig1. Say abeban uran ed amagan tan sobran amagan klima so amasimbalo ed baleg a parte na sarayan rehyon ya nagmaliw a desierto, buer, tan agnatanem iran dalin. Say tuloytuloy ya erosion na dagem et mangiter na peligro ed kaliberliber ed saray imprastraktura a singa saray transportasyon, dalin a panag-uma, tan dalin na industriya, a pansengegan na makapuy a kipapasen na panagbilay tan atagey a gastos ed panagpaalagey na syudad ed sarayan rehyon2,3,4. Say importante, say wind erosion et aglabat makaapekto ed pasen ya nagagawaan to, noagta pansengegan met na problema ed bunigas tan ekonomya ed saray ararawin komunidad lapud iyaakar to ray partikulo panamegley na dagem ed saray lugar ya arawi ed lapuan to5,6.
Say panangontrol ed erosion na dagem et mansiansian sankamundoan a problema. Nanduruman paraan na panagpabiskeg na dalin so uusaren pian nakontrol so erosion na dagem. Kaiba ed sarayan paraan iray materyales a singa say pangiyan na danum7, oil mulches8, biopolymers5, microbial induced carbonate precipitation (MICP)9,10,11,12 tan enzyme induced carbonate precipitation (EICP)1. Say panagbasa na dalin et sakey ya estandarten paraan na panag-ekal na dabok ed uma. Balet, say maples ya itatagey to et manggagawa ed sayan paraan ya limitado so inkaepektibo to ed saray amagan tan semi-arid a rehyon1. Say pangiyaplika na oil mulching compounds et mamaaligwas ed pankakasakey na buer tan panlalaban na saray partikulo. Say pankakasakey na kablian da so mangisisiglaot ed saray bukel na buer; balet, saray oil mulches et walaan met na arum nin problema; say maimpis a kolor da et mamarakep ed pansepsep na petang tan pansengegan na ipatey na tanaman tan mikroorganismo. Say angob tan asewek da et nayarin pansengegan na problema ed panag-ingas, tan say sankaimportantian et say atagey a gastos da so sananey nin babeng. Saray biopolymer et sakey ed saray agano nin niproponin eco-friendly ya paraan pian nabawasan so erosion na dagem; naala iratan ed natural iran lapuan a singa saray tanaman, ayayep tan bakterya. Say xanthan gum, guar gum, chitosan tan gellan gum so sankabaloan ya uusaren ya biopolymers ed saray aplikasyon na inhenyeriya5. Balet, saray water-soluble biopolymers et nayarin naandiay biskeg tan ontaynan ed dalin no naeksperiensya ra ed danum13,14. Say EICP et napatnagan ya epektibon paraan na panag-ekal na dabok parad nanduruman aplikasyon kaiba lay ag-asemento iran karsada, saray tailings pond tan saray pasen ya pangipapaalageyan. Anggaman makapaseseg iray resulta to, kaukolan ya ikonsidera so pigaran posiblin disbentaha, a singa say gastos tan say kakulangan na nucleation sites (ya mamapeles ed pakaporma tan pan-precipitate na CaCO3 crystals15,16).
Say MICP et inmunan indeskribe nen bandad sampot na koma-19 siglo nen Murray tan Irwin (1890) tan Steinmann (1901) diad impanaral da ed inkaderal na urea na saray mikroorganismo ed dayat17. Say MICP et sakey a natural ya proseso na biolohiya ya mangilalanor na nanduruman aktibidad na mikrobyo tan proseso na kemikal ya say calcium carbonate et onlelereg lapud reaksion na saray ion na carbonate manlapud saray metabolite na mikrobyo ed saray ion na calcium ed kaliberliber18,19. Say MICP ya mangilalanor ed urea-degrading nitrogen cycle (urea-degrading MICP) so sankabaloan ya klase na microbial-induced carbonate precipitation, ya say urease ya ginawa na bakterya so mamapawala na hydrolysis na urea20,21,22,23,24,25,26,27 unong ed onggendan:
Diad MICP ya mangilalanor ed carbon cycle na organic salt oxidation (MICP ya anggapoy urea degradation type), saray heterotrophic bacteria et manguusar na organic salts a singa say acetate, lactate, citrate, succinate, oxalate, malate tan glyoxylate bilang lapuan na enerhiya pian makapawala na carbonate minerals28. No walay calcium lactate bilang lapuan na carbon tan calcium ions, say kemikal ya reaksion na calcium carbonate formation et nanengneng ed equation (5).
Diad proseso na MICP, saray selula na bakterya so mangiiter na nucleation sites ya importantin tuloy parad panag-uran na calcium carbonate; say tapew na selula na bakterya et negatibo so karga to tan nayarin onkiwas bilang adsorbent parad divalent cations a singa say calcium ions. Diad pangi-adsorb na calcium ions ed saray selula na bakterya, no magenap so konsentrasyon na carbonate ion, onreak iray calcium cations tan carbonate anions tan say calcium carbonate et onlelereg ed tapew na bakterya29,30. Say proseso et nayarin isumaryo ed onggendan31,32:
Saray biogenerated calcium carbonate crystals et nayarin naapag ed taloran klase: calcite, vaterite, tan aragonite. Diad saratan, say calcite tan vaterite so sankabaloan ya calcium carbonate allomorphs ya nanlapud bakterya33,34. Say calcite so sanka-thermodynamically stable ya calcium carbonate allomorph35. Anggaman say vaterite et nireport ya metastable, diad kaunoran et magmaliw ya calcite36,37. Say vaterite so sankapal ed sarayan kristal. Saya so hexagonal crystal ya mas maong so pore filling to nen say arum ya calcium carbonate crystals lapud mas baleg so kabaleg to38. Parehon say urea-degraded tan urea-undegraded MICP et nayarin pansengegan na itatagey na vaterite13,39,40,41.
Anggaman say MICP et angipatnag na maabig a potensyal ed pamasiansia ed saray probleman dalin tan dalin ya mainomay ya naapektoan na dagem42,43,44,45,46,47,48, sakey ed saray resulta na urea hydrolysis et say ammonia, ya nayarin pansengegan na daiset anggad graben problema ed bunigas depende ed karakel na pakapatnagan49. Sayan epekto so manggagawa ed pangusar ed sayan partikular a teknolohiya a kontrobersyal, lalo la no kaukolan a tambalen so angkakabaleg iran lugar, a singa say pangekal na dabok. Niarum ni, say angob na ammonia et ag naanosan no say proseso et gagawaen ed atagey a karakel na pangiyaplika tan baleg a karakel, ya nayarin mangapekta ed praktikal ya pangiyaplika to. Anggaman impanengneng na saray agano nin impanaral ya saray ammonium ions et nayarin nabawasan no gawaen iratan ya arum a produkto a singa say struvite, sarayan paraan et agsigpot ya naekal iray ammonium ions50. Kanian, kaukolan nin siansia so mansukimat na alternatibon solusyon ya ag makapawala na ammonium ions. Say pangusar na non-urea degradation pathways parad MICP et nayarin mangiter na posiblin solusyon ya ag ni tanton naeksplor ed konteksto na wind erosion mitigation. Fattahi et al. inimbestigaan so urea-free MICP degradation ya inusar so calcium acetate tan Bacillus megaterium41, bangta si Mohebbi et al. inusar so calcium acetate tan Bacillus amyloliquefaciens9. Balet, say impanaral da et ag-inkompara ed arum ya lapuan na calcium tan heterotrophic bacteria ya nayarin mamaaligwas ed resistensya na dagem. Wala met so kakulangan na literatura ya mangikokompara ed saray urea-free degradation pathways tan urea degradation pathways diad pamalemew ed erosion na dagem.
Niarum ni, maslak ed saray impanaral ed wind erosion tan dust control et ginawa ed saray sample na dalin ya patatdang so tapew to.1,51,52,53 Balet, saray patatdang a tapew et mas daiset so kaslakan ed kalikasan nen saray pukdol tan depresyon. Saya so rason no akin ya saray buer so sankabaloan ya nanengneng ed saray desierto.
Pian natalonaan iray abitlan kakulangan, say gagala na sayan impanaral et mangiparungtal na balon set na saray bakterya ya ag-ontutubo ed ammonia. Parad sayan gagala, inkonsidera mi ray aliwan urea degrading MICP pathways. Inimbestigaan so inkaepektibo na duaran lapuan na calcium (calcium formate tan calcium acetate). Diad sankaabigan ya pikakabat na saray autor, say carbonate precipitation ya uusaren so duaran kombinasyon na calcium source tan bacteria (salanti, calcium formate-Bacillus subtilis tan calcium formate-Bacillus amyloliquefaciens) et agni naimbestigaan ed saray akaunan impanaral. Say impamili ed sarayan bakterya et base ed saray enzyme ya papawalaen da ya mamapakiwas ed oxidation na calcium formate tan calcium acetate pian nawalaan na microbial carbonate precipitation. Nandesinyo kami na sigpot ya eksperimenton panagaral pian naromog iray sankaabigan a bengatla a singa say pH, klase na bakterya tan saray lapuan na calcium tan saray konsentrasyon da, say ratio na bakterya ed solusyon na lapuan na calcium tan say panaon na panag-ayos. Diad kaunoran, say inkaepektibo na sayan set na bacterial agents ed pangisebel ed erosion na dagem panamegley na calcium carbonate precipitation et inimbestigaan diad panggawa na serye na wind tunnel tests ed saray sand dunes pian naamtaan so kabaleg na wind erosion magnitude, threshold breakaway velocity tan say resistensya na dagem ed buer, tan saray sukat na penetrometer tan microstructural (alimbawa ya X-ray-scanning) tan dictional analysis ginawa met so electron microscopy (SEM)).
Say produksyon na calcium carbonate et mankaukolan na calcium ions tan carbonate ions. Saray calcium ions et nayarin naala ed nanduruman lapuan na calcium a singa say calcium chloride, calcium hydroxide, tan skim milk powder54,55. Saray carbonate ions et nayarin nagawa panamegley na nanduruman paraan na mikrobyo a singa say urea hydrolysis tan aerobic o anaerobic oxidation na organic matter56. Diad sayan impanaral, saray carbonate ions et naala manlapud oxidation reaction na formate tan acetate. Niarum ni, angusar kami na calcium salts na formate tan acetate pian makagawa na puron calcium carbonate, kanian CO2 tan H2O labat so naala ya by-products. Diad sayan proseso, sakey labat a substansia so manserbin lapuan na calcium tan lapuan na carbonate, tan anggapoy napapawala ya ammonia. Sarayan katangian so manggagawa ed calcium source tan paraan na panaggawa na carbonate ya ipapasen min makapanpromisa.
Saray mipetekan a reaksion na calcium formate tan calcium acetate pian manporma na calcium carbonate et nanengneng ed pormula (7)-(14). Ipapanengneng na pormula (7)-(11) ya say calcium formate et ontunaw ed danum pian manporma na formic acid o formate. Say solusyon et lapuan na libren calcium tan hydroxide ions (formula 8 tan 9). Lapud say oxidation na formic acid, saray carbon atoms ed formic acid et magmaliw ya carbon dioxide (formula 10). Say calcium carbonate so naporma (formula 11 tan 12).
Ontan met, say calcium carbonate et naporma manlapud calcium acetate (equations 13-15), likud no say acetic acid odino acetate so naporma imbes ya formic acid.
No anggapoy enzymes, say acetate tan formate et ag nayarin na-oxidize ed temperatura na kuarto. Say FDH (formate dehydrogenase) tan CoA (coenzyme A) so mamapasyar ed oxidation na formate tan acetate pian manporma na carbon dioxide, 57, 58, 59. Saray nanduruman bakterya so makayarin mamawala ed sarayan enzyme, tan saray heterotrophic a bakterya, salanti, saray subtilis Bactilus Bactilus #PT (PT Typesian Typesian (2014) Say Culture Collection), ya kabkabat met bilang NCIMB #13061 (International Collection of Bacteria, Yeast, Phage, Plasmids, Plant Seeds and Plant Cell Tissue Cultures)) tan Bacillus amyloliquefaciens (PTCC #1732, NCIMB #12077), so inusar ed sayan impanaral. Sarayan bakterya et inkultura ed medium ya walay meat peptone (5 g/L) tan meat extract (3 g/L), ya tatawagen ya nutrient broth (NBR) (105443 Merck).
Kanian, apatiran pormulasyon so imparaan pian na-induce so calcium carbonate precipitation ya inusar so duaran lapuan na calcium tan duaran bakterya: calcium formate tan Bacillus subtilis (FS), calcium formate tan Bacillus amyloliquefaciens (FA), calcium acetate tan Bacillus subtilis (AS), tan calcium acetate tan Bacillus acetate (AAA).
Diad inmunan parte na eksperimenton desinyo, ginawa iray test pian naamtaan so sankaabigan ya kombinasyon ya makadampot na sankatageyan ya produksyon na calcium carbonate. Lapud saray sample na dalin et walaan na calcium carbonate, sakey a set na preliminary evaluation tests so ginawa pian suston nasukat so CaCO3 ya napapawala na nanduruman kombinasyon, tan saray mixture na culture medium tan calcium source solutions so inebalwar. Parad kada kombinasyon na calcium source tan bacteria solution ya adeskribe ed tagey (FS, FA, AS, tan AA), saray optimization factors (concentration na calcium source, curing time, bacteria solution concentration ya nasukat ed optical density na solution (OD), calcium source to bacteria solution ratio, tan pH) so naala tan inusar ed sand dune treatment wind tunnel tests ya adeskribe ed ontumbok iran deksion.
Parad kada kombinasyon, 150 ya eksperimento so ginawa pian aralen so epekto na CaCO3 ya uran tan nasuri so nanduruman bengatla, singa say konsentrasyon na panlalapuan na calcium, panaon na panagtambal, balor na OD na bakterya, ratio na panlalapuan na calcium ed solusyon na bakterya tan pH legan na aerobic oxidation na organic matter (Table 1). Say pH range parad optimized ya proseso et pinili base ed saray kurba na idakel na Bacillus subtilis tan Bacillus amyloliquefaciens pian mas maples so idakel da. Saya so mas detalyadon nipaliwawa ed seksion na Resulta.
Saray onggendan a kundang so inusar pian niparaan iray sample parad yugtan na panag-optimize. Say MICP ya solusyon et inmuna ya imparaan diad pangi-adjust ed inmunan pH na culture medium insan in-autoclave ed 121 °C ed loob na 15 min. Say strain et in-inoculate ed laminar air flow tan in-maintain ed shaking incubator ed 30 °C tan 180 rpm. No akasabi lay OD na bakterya ed labay ya lebel, inlaok itan ed solusyon na calcium source ed labay ya proporsyon (Figure 1a). Say solusyon na MICP et inabuloyan ya onkiwas tan onlewet ed sakey ya incubator ya onkuyegyeg ed 220 rpm tan 30 °C ed loob na panaon ya akasabi ed target ya balor. Say napelag ya CaCO3 et insian kayari na centrifugation ed 6000 g ed loob na 5 min insan pinamaga ed 40 °C pian niparaan iray sample parad calcimeter test (Figure 1b). Say uran na CaCO3 et sinukat ya inusar so Bernard calcimeter, ya say CaCO3 powder et onreak ed 1.0 N HCl (ASTM-D4373-02) pian makagawa na CO2, tan say karakel na sayan gas et sukat na CaCO3 content (Figure 1c). Pian nauman so karakel na CO2 ed CaCO3 ya laman, sakey a kurba na kalibrasyon so ginawa diad panguras ed puron CaCO3 powder ya walay 1 N HCl tan in-plot itan sumpad inmaligwas ya CO2. Say morpolohiya tan inkapuro na CaCO3 powder ya pinaltog et inimbestigaan ya inusar so SEM imaging tan XRD analysis. Say optical microscope ya walay magnification ton 1000 so inusar pian aralen so inkaporma na calcium carbonate ed kaliberliber na bakterya, say yugtan na aporma na calcium carbonate, tan say aktibidad na bakterya.
Say Dejegh Basin et kabkabat a rehyon ya aderal ed abalaten-bukig na Fars Province na Iran, tan saray researcher et nankolekta na saray sample na dalin ya aderal lapud dagem ed satan a lugar. Saray sample et inala ed tapew na dalin parad panaral. Saray indicator test ed saray sample na dalin so angipatnag ya say dalin et aliwan maong so inka-sort to na buer ya dalin ya walay silt to tan niklasipika bilang SP-SM unong ed Unified Soil Classification System (USC) (Figure 2a). Impanengneng na XRD analysis ya say dalin na Dejegh et manunan tugyopen na calcite tan quartz (Figure 2b). Niarum ni, say EDX analysis et angipatnag ya arum ya elemento a singa say Al, K, tan Fe et wala met ed mas melag iran proporsyon.
Pian niparaan iray laboratory dunes parad wind erosion testing, say dalin et pinuter manlapud 170 mm ya kaatagey panamegley na 10 mm ya diametro ya funnel ya anggad malet ya tapew, kanian walay tipikal ya dune ya 60 mm so kaatagey to tan 210 mm so diametro to. Diad kalikasan, saray sankaabebaan ya densidad na sand dunes et nabubuo lapud saray proseso na aeolian. Ontan met, say sample ya imparaan ya inusar so abitlan paraan et walaan na sankaabebaan ya relatibon densidad, γ = 14.14 kN/m3, ya manporma na sand cone ya indeposito ed pabitay ya tapew ya walay anggulo na repose ya ngalngalin 29.7°.
Say sankaabigan ya solusyon na MICP ya naala ed akaunan seksion et in-spray ed dune slope diad application rates ya 1, 2 tan 3 lm-2 insan saray sample et insimpen ed incubator ed 30 °C (Fig. 3) ed loob na 9 ya agew (salanti, say sankaabigan ya panaon na panag-ayos) insan inala parad wind tunnel testing.
Parad kada panagtambal, apatiran specimen so imparaan, sakey parad panukat na calcium carbonate content tan biskeg na tapew ya uusaren so penetrometer, tan say nakekeraan ya taloran specimen et inusar parad erosion tests ed taloran nanduruman kapeles. Diad saray wind tunnel tests, say karakel na erosion et nadetermina ed nanduruman kapeles na dagem, insan say threshold breakaway velocity parad kada treatment specimen et nadetermina ya inusar so plot na karakel na erosion kumpara ed kapeles na dagem. Nilikud ed saray wind erosion tests, saray tinambal ya specimen et inpaarap ed sand bombardment (salanti, saray eksperimento ed panaglukso). Duaran kaaruman ya specimen so imparaan parad sayan gagala diad application rate ya 2 tan 3 L m−2. Say sand bombardment test et nanbayag na 15 min ya walay flux ya 120 gm−1, ya walad loob na saray balor ya pinili ed saray akaunan impanaral60,61,62. Say horizontal ya distansya na abrasive nozzle tan say dune base et 800 mm, ya walad 100 mm ed tagey na tunnel bottom. Sayan posisyon et inletneg pian ngalngalin amin ya onlukso iran partikulo na buer et napelag ed pukdol.
Say wind tunnel test et ginawa ed sakey ya open wind tunnel ya 8 m so karukey to, 0.4 m so kalapar to tan 1 m so katagey to (Figure 4a). Say wind tunnel et gawad galvanized steel sheets tan makapawala na kapeles na dagem ya anggad 25 m/s. Niarum ni, walay frequency converter ya uusaren pian na-adjust so frequency na bentilador tan kalkalnan napalaknab so frequency pian naala so target ya kapeles na dagem. Ipapanengneng na Figure 4b so schematic diagram na saray sand dunes ya aderal na dagem tan say kapeles na dagem ya asukat ed wind tunnel.
Diad kaunoran, pian ikompara so resulta na non-urealytic MICP formulation ya inproponin sayan impanaral ed resulta na urealytic MICP control test, saray sample na dune so imparaan met tan inikdan na biological solution ya walay urea, calcium chloride tan Sporosarcina pasteurii (lapud say Sporosarcina pasteurii et walaan na signipikantin abilidad ya mamawala na urease63). Say optical density na solusyon na bakterya et 1.5, tan say konsentrasyon na urea tan calcium chloride et 1 M (pinili base ed saray balor ya inrekomenda ed akaunan impanaral36,64,65). Say culture medium et tugyopen na nutrient broth (8 g/L) tan urea (20 g/L). Say solusyon na bakterya et in-spray ed tapew na bunton tan tinaynan ed loob na 24 oras pian makapeket so bakterya. Kayari na 24 oras ya inkapeket, sakey a solusyon na semento (calcium chloride tan urea) so in-spray. Say urealytic MICP control test et tatawagen ya UMC. Say calcium carbonate content na urealytically tan non-urealytically ya intrato ed saray sample na dalin et naala diad panamegley na panag-uras unong ed paraan ya inproponin Choi et al.66
Ipapanengneng na Figure 5 so kurba na idakel na Bacillus amyloliquefaciens tan Bacillus subtilis ed culture medium (solusyon na sustansya) ya walay inmunan pH range ya 5 anggad 10. Singa nanengneng ed figure, say Bacillus amyloliquefaciens tan Bacillus subtilis et mas maples ya binmaleg ed pH 6-8 tan 7-9, unong ed inkauksoy da. Kanian, sayan pH range so inadapta ed yugtan na panag-optimize.
Saray kurba na idakel na (a) Bacillus amyloliquefaciens tan (b) Bacillus subtilis ed nanduruman inmunan pH na nutrient medium.
Ipapanengneng na Figure 6 so karakel na carbon dioxide ya napapawala ed Bernard limemeter, ya mangirerepresenta ed precipitated calcium carbonate (CaCO3). Lapud sakey a factor so akapeket ed kada kombinasyon tan saray arum a factor et nanduruma, kada punto ed sarayan graph et mipetekan ed sankarakelan a karakel na carbon dioxide ed satan a set na eksperimento. Unong ed nanengneng ed pigura, legan ya ondarakel so calcium source concentration, ondarakel met so produksyon na calcium carbonate. Kanian, say konsentrasyon na lapuan na calcium et direktan mangaapekta ed produksyon na calcium carbonate. Lapud pareho so lapuan na calcium tan say lapuan na carbon (salanti, say calcium formate tan calcium acetate), no mas dakel so calcium ions ya ompaway, mas dakel so calcium carbonate ya naporma (Figure 6a). Diad AS tan AA ya pormulasyon, say produksyon na calcium carbonate et nantultuloy ya inmaligwas legan ya ondarakel so panaon na panag-ayos anggad say karakel na precipitate et ngalngali ag-anguman kayari na 9 ya agew. Diad FA formulation, say rate na calcium carbonate formation et dinmaak no say panaon na panagtambal et linmampas ed 6 ya agew. No ikompara ed arum ya pormulasyon, say pormulasyon FS et angipatnag na medyo abeban calcium carbonate formation rate kayari na 3 agew (Figure 6b). Diad saray pormulasyon ya FA tan FS, 70% tan 87% na dagup ya produksyon na calcium carbonate so naala kayari na taloy agew, bangbalet diad saray pormulasyon ya AA tan AS, sayan proporsyon et manga 46% tan 45% labat, unong ed inkauksoy da. Ipapanengneng na saya ya say formic acid-based ya pormulasyon et walaan na mas atagey ya CaCO3 formation rate diad gapo no ikompara ed acetate-based ya pormulasyon. Balet, say peles na inkaporma et onkepa no ondarakel so panaon na panagtambal. Nayarin konklusyonan manlapud Figure 6c ya anggan diad konsentrasyon na bakterya ya mas atagey nen say OD1, anggapoy signipikantin kontribusyon to ed inkaporma na calcium carbonate.
Say panguman na CO2 volume (tan say CaCO3 content) ya sinukat na Bernard calcimeter bilang function na (a) konsentrasyon na nanlapuan na calcium, (b) panaon na pangiletneg, (c) OD, (d) inmunan pH, (e) ratio na nanlapuan na calcium ed solusyon na bakterya (parad kada pormulasyon); tan (f) sankatageyan ya karakel na calcium carbonate ya napapawala parad kada kombinasyon na lapuan na calcium tan bakterya.
Nipaakar ed epekto na inmunan pH na medium, ipapanengneng na Figure 6d ya parad FA tan FS, say produksyon na CaCO3 et akasabi ed sankatageyan ya balor ed pH 7. Sayan obserbasyon et mipara ed saray akaunan impanaral ya saray FDH enzymes et sanka-stable ed pH 7-6.7. Balet, parad AA tan AS, say CaCO3 ya uran et dinmaak no say pH et onlampas ed 7. Impanengneng met na saray akaunan impanaral ya say sankaabigan ya pH range parad aktibidad na CoA enzyme et manlapud 8 anggad 9.2-6.8. No isipen ya say sankaabigan ya pH ranges parad CoA enzyme activity tan B. amyloliquefaciens growth et (8-9.2) tan (6-8), unong ed inkauksoy da (Figure 5a), say sankaabigan ya pH na AA formulation et iilaloan ya 8, tan mansasalet so duaran pH ranges. Sayan katuaan et akumpirma na saray eksperimento, a singa nanengneng ed Figure 6d. Lapud say sankaabigan ya pH parad idakel na B. subtilis et 7-9 (Figure 5b) tan say sankaabigan ya pH parad aktibidad na CoA enzyme et 8-9.2, say sankatageyan ya CaCO3 precipitation yield et iilaloan ya walad pH range ya 8-9, ya akumpirma na Figure 6d (salanti, say sankaabigan ya pH et 99). Say resulta ya nanengneng ed Figure 6e et mangipapanengneng ya say sankaabigan ya ratio na solusyon ya nanlapuan na calcium ed solusyon na bakterya et 1 parad parehon solusyon na acetate tan formate. Parad panangikompara, say performance na nanduruman pormulasyon (salanti, AA, AS, FA, tan FS) et inebalwar base ed sankatageyan ya produksyon na CaCO3 ed nanduruman kondisyon (salanti, konsentrasyon na nanlapuan na calcium, panaon na panagtambal, OD, ratio na nanlapuan na calcium ed solusyon na bakterya, tan inmunan pH). Diad saray pormulasyon ya inaral, say pormulasyon FS so walaan na sankatageyan ya produksyon na CaCO3, ya ngalngalin taloran danay nen say pormulasyon AA (Figure 6f). Apatiran eksperimento ya anggapoy bakterya so ginawa parad parehon lapuan na calcium tan anggapoy anengneng ya CaCO3 ya uran kayari na 30 ya agew.
Say optical microscopy images na amin ya pormulasyon so angipatnag ya say vaterite so manunan parte na calcium carbonate (Figure 7). Saray kristal na vaterite et malimpek so kurti ra69,70,71. Nalmoan ya say calcium carbonate et onlelereg ed saray selula na bakterya lapud say tapew na selula na bakterya et negatibo so karga to tan nayarin onkiwas bilang adsorbent parad divalent cations. No alaen so formulation FS bilang alimbawa ed sayan impanaral, kayari 24 oras, ginmapon naporma so calcium carbonate ed pigaran selula na bakterya (Figure 7a), tan kayari 48 oras, say bilang na selula na bakterya ya akapeket na calcium carbonate et dinmaak a maong. Niarum ni, singa nanengneng ed Figure 7b, saray partikulo na vaterite et nayarin nanengneng met. Diad kaunoran, kayari na 72 oras, singa baleg so bilang na bakterya ya akapeket ed saray kristal na vaterite, tan say bilang na saray partikulo na vaterite et dinmaak a maong (Figure 7c).
Saray obserbasyon ed optical microscopy na CaCO3 ya uran ed saray komposisyon na FS legay panaon: (a) 24, (b) 48 tan (c) 72 h.
Pian lalon naimbestigaan so morpolohiya na precipitated phase, ginawa so X-ray diffraction (XRD) tan SEM ya panagsukimat ed saray pulbos. Say XRD spectra (Fig. 8a) tan SEM micrographs (Fig. 8b, c) so angikumpirma na kiwawala na vaterite crystals, lapud singa lettuce so kurti ra tan anengneng so pantutunosan na saray vaterite peaks tan saray precipitate peaks.
(a) Panangikompara na X-ray diffraction spectra na naporman CaCO3 tan vaterite. SEM micrographs na vaterite ed (b) 1 kHz tan (c) 5.27 kHz ya panagpabaleg, unong ed inkauksoy da.
Saray resulta na wind tunnel tests et nanengneng ed Figure 9a, b. Nanengneng ed Figure 9a ya say threshold erosion velocity (TDV) na ag-atambalan ya buer et manga 4.32 m/s. Diad application rate ya 1 l/m2 (Figure 9a), saray slope na soil loss rate lines parad saray fraction ya FA, FS, AA tan UMC et ngalngalin pareho ed ag-atambalan ya dune. Ipapanengneng na saya ya say panagtambal ed sayan kapeles na aplikasyon et aliwan epektibo tan no onlampas so kapeles na dagem ed TDV, naandi so manipis ya crust na dalin tan say kapeles na erosion na dune et pareho ed ag-atambalan ya dune. Say erosion slope na fraction AS et abeba met nen say arum ya fraction ya walaan na abeban abscissas (salanti, TDV) (Figure 9a). Ipapanengneng na saray pana ed Figure 9b ya diad sankapelesan ya kapeles na dagem ya 25 m/s, anggapoy agawan erosion ed saray tinambalan a bunton diad 2 tan 3 l/m2 ya kapeles na dagem. Diad arum a salita, parad FS, FA, AS tan UMC, saray dunes et mas makaresisti ed erosion na dagem ya sengegan na CaCO3 deposition diad application rates ya 2 tan 3 l/m2 nen say sankatageyan ya kapeles na dagem (salanti, 25 m/s). Kanian, say TDV value ya 25 m/s ya naala ed sarayan test et say abeban limitasyon parad saray application rates ya nanengneng ed Figure 9b, likud ed kaso na AA, ya say TDV et ngalngalin mipara ed sankatageyan ya kapeles na wind tunnel.
Wind erosion test (a) Say pakawalaan na belat kumpara ed kapeles na dagem (application rate 1 l/m2), (b) Threshold tear-off speed kumpara ed application rate tan pormulasyon (CA parad calcium acetate, CF parad calcium formate).
Ipapanengneng na Figure 10 so surface erosion na saray sand dunes ya inikdan na nanduruman pormulasyon tan application rates kayari na sand bombardment test tan saray quantitative results et nanengneng ed Figure 11. Say ag-intreat ya kaso et ag-ipapanengneng lapud anggapoy resistensya to tan sigpot ya naandi (total mass loss) legan na sand bombardment test. Malinew ed Figure 11 ya say sample ya inikdan na biocomposition AA et abalang na 83.5% na belat to diad application rate ya 2 l/m2 bangbalet amin ya arum ya sample et walaan na kulang ya 30% ya erosion legan na proseso na sand bombardment. Nen say application rate et inmatagey ed 3 l/m2, amin ya sample ya atambalan et naandi na kulang ya 25% na belat da. Diad parehon rate na aplikasyon, say compound FS so angipatnag na sankaabigan ya resistensya ed panagbomba na buer. Say sankatageyan tan sankaabebaan ya resistensya ed panagbomba ed saray sample ya inikdan na FS tan AA et nayarin ipasen ed sankatageyan tan sankaabebaan ya CaCO3 precipitation da (Figure 6f).
Resulta na panagbomba ed saray sand dunes ya nanduruman komposisyon ed flow rates ya 2 tan 3 l/m2 (saray arrow et mangipapanengneng na direksion na dagem, saray krus et mangipapanengneng na direksion na dagem ya akapeket ed plano na drowing).
Unong ed nanengneng ed Figure 12, say calcium carbonate content na amin ya pormula et dinmaak legan ya inmaligwas so application rate manlapud 1 L/m2 ya anggad 3 L/m2. Niarum ni, diad amin ya aplikasyon, say pormula ya walaan na sankatageyan ya calcium carbonate et say FS, ya tumbokan na FA tan UMC. Ipapanengneng na saya ya sarayan pormula et nayarin walaan na mas atagey ya resistensya ed tapew.
Ipapanengneng na Figure 13a so panguman na resistensya na tapew na ag-atambalan, kontrol tan atambalan iran sample na dalin ya sinukat panamegley na permeameter test. Manlapud sayan pigura, mapatnag ya say surface resistance na UMC, AS, FA tan FS ya pormulasyon et dinmaak a maong legan ya ondarakel so aplikasyon. Balet, say indakel na biskeg na tapew et medyo melag ed AA ya pormulasyon. Unong ed nanengneng ed pigura, saray FA tan FS ya pormulasyon na aliwan urea-degraded MICP et mas maong so surface permeability no ikompara ed urea-degraded MICP. Ipapanengneng na Figure 13b so pananguman na TDV ed resistensya na tapew na dalin. Manlapud sayan pigura, malinew ya napatnagan ya parad saray bunton ya walay surface resistance ya mas atagey nen say 100 kPa, say threshold stripping velocity et onlampas ed 25 m/s. Lapud say in situ surface resistance et mainomay ya nasukat panamegley na permeameter, sayan pikakabat et makatulong pian nakalkula so TDV no anggapoy wind tunnel testing, kanian manserbin indicator na kalidad na kontrol parad saray aplikasyon ed uma.
Say resulta na SEM et nanengneng ed Figure 14. Ipapanengneng na Figure 14a-b so binmaleg iran partikulo na ag-atambalan ya sample na dalin, ya malinew ya mangipapanengneng ya mankakasakey itan tan anggapoy natural ya pankakasakey odino inkasemento to. Ipapanengneng na Figure 14c so SEM micrograph na control sample ya inikdan na urea-degraded MICP. Ipapanengneng na sayan imahen so kiwawala na CaCO3 precipitates bilang calcite polymorphs. Unong ed nanengneng ed Figures 14d-o, say CaCO3 ya atumba et mankakasakey ed saray partikulo; saray spherical vaterite crystals et nayarin nabirbir met ed saray SEM micrographs. Say resulta na sayan impanaral tan saray akaunan impanaral et mangipapanengneng ya saray CaCO3 bonds ya naporma bilang vaterite polymorphs et makapangiter met na makatunongan ya biskeg na mekanikal; ipapanengneng na saray resulta mi ya say resistensya na tapew et ondarakel ed 350 kPa tan say kapeles na pansiansia na threshold et ondarakel manlapud 4.32 ya anggad masulok ya 25 m/s. Sayan resulta et mipara ed resulta na saray akaunan impanaral ya say matrix na MICP-precipitated CaCO3 et vaterite, ya walaan na makatunongan ya biskeg na mekanikal tan resistensya ed erosion na dagem13,40 tan makapansiansia na makatunongan ya resistensya ed erosion na dagem anggan kayari na 180 ya agew ya pakawalaan na kaliberliber ed uma13.
(a, b) SEM micrographs na ag-atambalan a dalin, (c) MICP urea degradation control, (df) AA-treated samples, (gi) AS-treated samples, (jl) FA-treated samples, tan (mo) FS-treated samples diad application rate ya 3 L/m2 ed nanduruman magnification.
Ipapanengneng na Figure 14d-f ya kayari na panagtambal na AA compounds, say calcium carbonate so inmepas ed tapew tan diad baetan na saray bukel na buer, bangbalet wala met so anengneng ya ag-aka-coat ya bukel na buer. Parad saray AS components, anggaman say karakel na CaCO3 ya aporma et ag-inmatagey a maong (Fig. 6f), say karakel na saray kontak ed baetan na saray sand grains ya sengegan na CaCO3 et inmatagey a maong no ikompara ed saray AA compound (Fig. 14g-i).
Manlapud Figures 14j-l tan 14m-o et malinew ya say pangusar na calcium formate bilang panlapuan na calcium et mangitonton ed lalon idakel na CaCO3 precipitation no ikompara ed AS compound, ya mipara ed saray sukat na calcium meter ed Figure 6f. Sayan kaaruman ya CaCO3 et ompatnag ya manunan nadeposito ed saray partikulo na buer tan agmet seguradon mamaaligwas ed kalidad na pidedeneng. Saya so mamepekder ed akauna lan naobserbaan ya ugali: anggaman ed pandumaan na karakel na CaCO3 ya uran (Figure 6f), say taloran pormulasyon (AS, FA tan FS) et ag mandumaan a maong no nipaakar ed anti-eolian (dagem) ya performance (Figure 11) tan surface resistance (Figure 13a).
Pian mas nanengneng so CaCO3 coated bacterial cells tan say bacterial imprint ed saray precipitated crystals, angala na high magnification SEM micrographs tan saray resulta et nanengneng ed Figure 15. Singa nipanengneng, say calcium carbonate et onlelereg ed saray bacterial cells tan mangiter na nuclei ya nakaukolan parad precipitation diman. Ipapanengneng met na pigura so aktibo tan inaktibo iran siglaotan ya sengegan na CaCO3. Nayarin konklusyonan ya antokaman ya idarakel na saray ag-onkikiwas a siglaotan et agsigpot a manresulta ed lalon iyaligwas na mekanikal a kalareker. Kanian, say idarakel na CaCO3 ya uran et agsigpot ya manresulta ed mas atagey ya biskeg na makina tan say pattern na uran et walay importantin betang to. Sayan punto et inaral met ed saray kimey nen Terzis tan Laloui72 tan Soghi tan Al-Kabani45,73. Pian lalon nausisa so siglaotan na pattern na uran tan say biskeg na makina, nirekomenda so MICP ya panaral ya manguusar na μCT imaging, ya ag la nasarag na sayan panaral (salanti, say pangiloob na nanduruman kombinasyon na lapuan na calcium tan bakterya parad MICP ya anggapoy ammonia).
Say CaCO3 so amalesa na aktibo tan ag aktibo iran bedber ed saray sample ya inikdan na (a) AS a komposisyon tan (b) FS a komposisyon tan angitilak na imprint na saray selula na bakterya ed sediment.
Unong ed nanengneng ed Figures 14j-o tan 15b, walay CaCO film (unong ed EDX analysis, say porsiento na komposisyon na kada elemento ed pelikula et carbon 11%, oxygen 46.62% tan calcium 42.39%, ya asingger a tuloy ed porsiento na CaCO ed Figure 16). Sayan pelikula et mansakbong ed saray kristal na vaterite tan saray partikulo na dalin, ya ontutulong pian napansiansia so integridad na sistema na dalin-sediment. Say kiwawala na sayan pelikula et naobserbaan labat ed saray sample ya inikdan na formate-based formulation.
Ikokompara na Table 2 so biskeg na tapew, kapeles na itatatken na dalin, tan say bioinduced CaCO3 ya laman na dalin ya inikdan na urea-degrading tan non-urea-degrading MICP pathways diad saray akaunan impanaral tan sayan impanaral. Limitado so impanaral ed resistensya na dagem ed saray sample na dune ya inikdan na MICP. Meng et al. inimbestigaan so wind erosion resistance na MICP-treated urea-degrading dune samples ya inusar so leaf blower,13 bangbalet diad sayan impanaral, saray non-urea-degrading dune samples (ontan met ed urea-degrading controls) so sinubok ed sakey a wind tunnel tan inikdan na apatiran nanduruman kombinasyon na bakterya tan substansia.
Singa nanengneng, wala ray akaunan impanaral ya angikonsidera na atagey ya aplikasyon ya onlampas ed 4 L/m213,41,74. Nepeg ya imanoen ya say atagey ya bilang na aplikasyon et nayarin aliwan mainomay ya iyaplika ed lawak manlapud punto de bista na ekonomya lapud saray gastos ya misiglaotan ed suplay na danum, transportasyon tan aplikasyon na baleg a danum. Say abeban rate na aplikasyon a singa say 1.62-2 L/m2 so akagamor met na medyo maabig iran biskeg na tapew ya anggad 190 kPa tan TDV ya onlampas ed 25 m/s. Diad sayan impanaral, saray bunton ya inikdan na formate-based MICP ya anggapoy urea degradation et akagamor na atagey a biskeg na tapew ya mipara ed saramay naala ed urea degradation pathway diad parehon range na application rates (salanti, saray sample ya inikdan na formate-based MICP ya anggapoy urea degradation et akagamor met na parehon range na surface strength ya inreport nen Mereng et al. 13, Figure 13a) ed mas atagey ya bilang na aplikasyon. Nanengneng met ya diad application rate ya 2 L/m2, say yield na calcium carbonate parad wind erosion mitigation ed kapeles na dagem ya 25 m/s et 2.25% parad formate-based MICP ya anggapoy urea degradation, ya asingger a tuloy ed nakaukolan ya karakel na CaCO3 (salanti, 2.41%) no ikompara ed saray dunes ya inikdan na control MICP ed parehon urea degradation say kapeles na aplikasyon tan parehon kapeles na dagem (25 m/s).
Kanian, nayarin konklusyonan manlapud sayan table ya parehon say urea degradation pathway tan say urea-free degradation pathway et makapangiter na naabobonan ya performance no nipaakar ed surface resistance tan TDV. Say manunan pandumaan et say urea-free degradation pathway et anggapoy ammonia to kanian mas abeba so epekto tod kaliberliber. Niarum ni, say formate-based MICP ya paraan ya anggapoy urea degradation ya iproproponin sayan impanaral et singa mas maong so performance to nen say acetate-based MICP ya anggapoy urea degradation. Anggaman si Mohebbi et al. inaral da so acetate-based MICP ya paraan ya anggapoy urea degradation, say impanaral da et inlaktip iray sample ed patatdang iran tapew9. Lapud mas atagey so grado na erosion ya sengegan na eddy formation ed kaliberliber na saray sample na dune tan say resulta na shear, ya manresulta ed abeban TDV, say erosion na dagem ed saray sample na dune et iilaloan ya mas mapatnag nen say saray patatdang a tapew ed parehon kapeles.