The effects of urea, (NH₄)₂SO₄, KNO₃, and NH₄NO₃ on nitrous oxide (N₂O) emission from soil at field capacity and submerged condition were studied during 120 days in the laboratory. Soils in both moisture regimes gave higher emissions in the beginning, which were reduced later. Total emission of N₂O was higher at submergence as compared to field capacity regardless of fertilizer type. At field capacity soil fertilized with ureaemitted the highest amount of N₂O (1903 μg N₂O-N kg⁻¹ soil) during 120 days while at submerged condition, soil with NH₄NO₃ gave the highest emission (4843 μg N₂O-N kg⁻¹ soil). In another study, the efficacy of seven nitrification inhibitors in reducing the emission of N₂O-N from soil fertilized with urea was tested in the laboratory. Nitrapyrin, 2-amino-4-chloro-6-methylpyrimidine (AM), and dicyandiamide (DCD) reduced the emission to 12, 24, and 63% that of urea, respectively, whereas sodium thiosulphate, sulphur, acetylene,and thiourea had no effect on emission of N₂O. In submerged conditions none of the inhibitors reduced the emission.

The maintenance of safe-drivingconditions in snow and ice-affected areas in thewintertime includes the use of sodium chloride (NaCl)as de-icing salts. In this study, the impact of NaClon soil-colloid mobilisation and exchangeablebase-cation leaching has been evaluated. The chemistryof groundwater samples below an infiltration trenchfor highway runoff and leachate from column studiessuggested that soil-colloid mobilisation had occurred,as the exchangeable sodium (Na) concentration and theelectrical conductivity (EC) in the groundwater/columnleachate reached the threshold values for colloiddispersion. Generally, samples with no dispersionproblems had high Na and calcium (Ca) concentrations,suggesting that the initial effect of the de-icingsalt was to stabilise the colloids. In the columnstudy there was a good agreement between the degree ofcolloid dipersion problems and lead (Pb) concentrationwhen the pH value was above 7.0. Significant negativecorrelations between Na/CEC (cation exchange capacity)and Ca/CEC in roadside soils from three sitesindicated that Na preferentially displaces Ca from theexchange sites. However, the groundwater dataindicated that Na ions also displace potassium (K) andmagnesium (Mg). A positive effect of NaCl seen at onesite was an increase in the K concentration, which ishighly likely an effect of Na ions displacing fixed Kbetween the layers of 2:1 type clay minerals. In soilslacking these types of clay minerals, severe Kshortage may result from a high plant demand combinedwith the low K concentration in the readily availablefractions in the original soil and a highsusceptibility to leaching. The most significantimpact on soil exchange processes was found to occurwithin 6 m from the road.

Rainwater samples (N = 51) were collected at Rampur, an areafree from anthropogenic activity during the monsoon of 1997 and1998. The concentration of ions follows a general pattern as Ca> NH₄ > Mg > SO₄ > Cl > F >Na > NO₃ > K > HCOO >CH₃ COO. The pH of precipitation ranges between 5.9 and 7.4. The levels of Ca and Mg at this site are higher than otherremote sites, probably dominated by particles of soil origin.Good correlation between Ca, NO₃, SO₄, HCOO and CH₃COO indicate that a fraction of NO₃, SO₄, HCOOand CH₃COO may be derived from soil or associated with Ca and Mg after neutralization. The order of neutralization factorCa (2.19) > NH₄ (1.26) = Mg (1.26) indicates that majorneutralization occurred by Ca. Factor analysis suggested thatCa, Mg, Na, K, NO₃, SO₄, HCOO and CH₃COO arecontributed by soil. NH₃ is known to exist as(NH₄)₂SO₄, NH₄NO₃ and NH₄Cl. Theymay be formed in the atmospheric water droplets by scavenging ofaerosols and reaction of gaseous species.

Mercury (Hg) methylation was studied in water,sediment and Eichhornia crassipesroots of a freshwater lake, in Rio de Janeiro(Brazil). Samples were incubated with²⁰³HgCl₂ and the Me²⁰³Hg producedwas measured by liquid scintillation.Methylmercury (MeHg) production was <10⁻³% in water, low in sediment (up to5.8%) and high in E. crassipesroots (21–27%). Higher MeHg formation wasfound in aerobic conditions for the roots and inanaerobic conditions for the sediment.Methylation increased with incubation time, upto 5 days. A 3-day incubation period was used inthe majority of the assays, to avoid large scalephysico-chemical changes inside the incubationflasks. Methylation was not detected inheat-sterilized root samples. Sodium sulphatestimulated Hg methylation while sodium molybdateinhibited the process in samples incubated for3, 6, 12, 24, 48 and 72 hr. This suggeststhat sulphidogenic bacteria are responsible forthe methylation process. Experiments with rootsstored at 5 and 25 °C fordifferent periods before incubation, indicatethat methylation is modified by storage time and temperature.