Study On Characteristics And Modelling Description Of Nitrate Transport In Soil Environment And The Application In Wu-Shan Soil Of Tai Lake Region

Leaching ofnitIae is a problem of great importanCe for soil Phyics StUdy but alsofOr studies of Watr POllUton in envirnmental science. The loss of nithegen mainlyin form of niot in the boland soils had been considered as the major cause foreutroPhication of the Tai Lake.By means of soil colufnn monitoring with hme doH reflectomtw (TDR)and soil wate phySics research both in field and at laboratory nitrate bosPOrtProcess and mechbosm in soil envirOrUnot as theced by soil mOStUtre Physics,was dealt with in this PapeL A arentiy deveIOPed medeI (CXThro was used tosirnulate the nihe transport phenomenon, eSPeCiaily in the case of Wu Shan soil ofTai Lake Region. Our objectives were to provide scientfic data fOr Undrstanding thebasic fetas of nitr8te boPOrt in soils and to offer some fundaInental infOrmationof the't, Wrs goveming the leaching loss of ulbe in Ihady soils. h is antiipatetha the resultS here could be uSeful for illustIating the POssibility of nitrogenlearhing POllution frOm bo fields to the Tai Lak. The Inain results were asfOllows:The UndiStUred soi1 colunms of sand loam soil in Lauvain, Belgha were usedtO study fastors involved in measuremnt of sohite transport by mR. mR seemedtO have lowe limit of the solute concentwiO4 being about 40 mg/L in case ofCguOa)z. TemPeratUre tUmd tO be another maor bor, fOr the imPedane ofTDR M as the tempsratUre increased. DiW W and COnCenthaonaffeCted balance tAne of solute tIanSPOrt. in additiOn, the theckness and length ofttiR Probe also had some effeCtS on the measurin multS. Therefore, the TDRprobes mus be talihated CareMiy before use.Whn the nitw mp intenSity was in close relation with the Water nux andsolute cowton in ds soil columns. The measured dsugh curvesW Wrt Pmss of niwt was cloedtO those by using CThIT medel. TheaPPlicatfon of the CXTFIT modl had anothr advantagn of obtainin the values ofdiWion coefficient and average POre water velocihes. The dispersion coefficientof nibe was closely related tO soil layeL The average POre Wator velocihesdecwt with dePth. The diWion coefficien was also related to Ne POreWate velocities.The sod hydraulic cotheivity of Wu Shan soil in the Tai hak Regionvaried in a wee of 0.72 x l04 c!n/s to 6.33 X 104 cInl, and decreased fiDm top soilto bottam in tbe soil profile. A negative linear relationship was found betweentwed Wic conduchvity and soil clay prtcles, strilar relation ship could bealso found for Wr clerterishc curve. The Wushan soil contained a lot of shellremaining, resulhng in decrease tCndency of be watr contCllt, field moiSt[lfcaPacity and wilting coefficien from top to bottOm in soil profile. The availablewater conten of thes soil is very loW which is about 44.2 ~ 74.9 g/kg. Theunnd hydraulic conduCtivity(UHC) of the experiInntal soil is haons of soilmatric potential, and aiso a negative relationship ekisted betwee (UHC) and soilnegative PreSsure head. The UHC tended tO be neglectable and stable When thenegallve presare is about 10 kPa.The UnSathed soil ditheion coefficien of studied soils mpd frOm 1.053 xl0G ~ l .886 x l0a cm3/Inin, which was in a SharP posihve relation with soil moiStUreconten. The conCentration of nibe in horizontal tIanSPOrt increased with thedecreasing diStance of the har source, with the intensity dopnding on the moiStUrconten. Therfore, the hOrizonul nibe soIute bosport was contrOlled both by theconcentIation gradient and soil Water POboal peienLThe nitw wt during whltalon process was different from the horizontaWrt' ffe Wugh curve of -- ProCess in wtted condition wasmore or less non-syIYUntrical. ms tended tO be caused by the diffend ProPOnionof mobile Water and immobile Wate and by soil Physicai Properties of the soil. Thevalue of cation combined with nitrate hardiy played a role in venical tranpe ofnitrate. Under UnSatUrad cochon, the tiIn of the tranSPO PrOcess of nitw wasobvious ProlWd, Peak vaiue of the bwtwi curv ndsed, while t...