5" day - Central Institute of Brackishwater Aquaculture
5" day - Central Institute of Brackishwater Aquaculture
5" day - Central Institute of Brackishwater Aquaculture
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2. IDENTIFICATION AND MANAGEMtKT OF ACID SULPEUTE SOILS IN<br />
SHRIMP FARMS<br />
Acid W sedimcmr known u rid sulphue soib (ASS) hve bun<br />
ikntifmd nsanly u a major sut+ <strong>of</strong> p r o m pmb*mc in Sourh<br />
AI*.SovmE.nA.4E.n~ML.mdAIumlLAoidrulphmBoibIrC<br />
cxtmrlvc on couul pbs in the bwpb buc am less oanmon in temprme Mom.<br />
Anempu to recl.bn aopiul nungrove swunpl fa 8quruh md rice poductions<br />
<strong>of</strong>ten haw mulled in the dcvelopmat <strong>of</strong> unpoductive wid sulphatc roils. It has<br />
been estimated that India hr ova 2 million ha <strong>of</strong> ASS that have the pamtial to csua<br />
long-term production pmblomr. if cxuvmtd. Oxidised AS% ware louted in shrimp<br />
h and along unrlr that umncst &imp padr to thc emury.<br />
Acld ~lph- mll ir cbc mmmon nmnc given to mil md adimant maining<br />
oxidiubb, a rlmdy oxidimd arlphida. Thc piacipl form <strong>of</strong> rulphii is iron<br />
pyrirc (cubic Feh) although ocher forms Nth u monaulphidm exin in smalkr<br />
concmmtions. If the roil m ins in a reduced condition so that no oxidation <strong>of</strong> the<br />
sulphide occun. the soil is ref4 u a poccntial uid sulphate soil PASS) or a<br />
rulphudic soil (oxidisable sulphur compounds). Where (he sulphiks arc exposed to<br />
air, lo that oxidation un ukc p b, the roil is dled an achul acid sulphatc sot1<br />
(AASS) or tul&uric mil (fleld VH <strong>of</strong> 3.8 md chloride to wldutc mio in soil<br />
solutlon < 2 m d), Oxidisin8 con&tionr frrquently overlie reducik conditions in the<br />
some pr<strong>of</strong>ile so that M SS and PASS appl) to different pans <strong>of</strong>the same pmfik.<br />
2.1 Nahrc <strong>of</strong> .dd r8lpb8tc mils<br />
When the sea level rox and inundate pond. sulphatc in he seawater m~xed u ith<br />
land sediments containing iron oxides and organic maner. The resulting chemical<br />
reactions pmduced large qwtitiu <strong>of</strong> iron sulphidcr in the waterlogged sediments.<br />
Under nrmnl condltlonr iron ~ lphih layen ur cowmi by warn and colonlzcd by<br />
nallve vrgotation.<br />
~~fl, (s) + 4 SO,'. + ~CHIO + YI + F ~ 6) I + 8HCOj + 4Hfi<br />
Sedimmt Seawater Orgmic m*tcr 4?ite<br />
fhe five conditions nauury for the formation <strong>of</strong> sulphides in codstal sediments are<br />
I. Supply <strong>of</strong> sulphte<br />
2. Supply <strong>of</strong> easily decomposed orplnic W.<br />
3. An depute <strong>of</strong> iron<br />
4. Aluerobic conditions together with chcmiully reducing microbes<br />
flushing to remow soluble d o n p.oducu.<br />
5. Tidal action<br />
T & n g u mdimwtts wnahrtag Pyma mu ru- ud ammhk they<br />
damduadmdcka(*IW.. Hanr.iftb.ymniaod.ndqxpodmtheair,<br />
oxldulon rsub ud ~lpburlc wid b M. Thr ummvy leutmns lor rulpbwk<br />
widtamuionfraninmpyrh.8n:
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