: Agricultural and residential activities are key non‐point sources of nitrogen pollution in urban‐rural fringe areas. A GIS‐based watershed approach was used to compare land use indicators (septic system and animal unit densities), to streamwater nitrate‐N in the Salmon River near Vancouver, B.C., Canada. The density of septic systems was used as an indicator of residential development while animal unit density was used as an indicator of the intensity of agricultural activity. Nitrate‐nitrogen (nitrate‐N) concentrations as high as 7.1 mg·L−1 were found in the mid‐portion of the watershed during the summer months, when streamflow is low and groundwater comprises a large proportion of water in the stream. The major aquifer supplying water to the midsection of the watershed is contaminated with nitrate‐N. A comparison of the relationships between septic system and animal unit density and nitrate‐N in the upstream to downstream direction provided evidence that both residential and agricultural activities contribute to elevated nitrate‐N in the Salmon River mainstem. In contrast, only septic system density corresponded to the pattern of streamwater nitrate‐N in Coghlan Creek, the main tributary to the Salmon River.

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Sustaining soil fertility under agricultural intensification and expansion onto marginal lands is a significant challenge in the Nepalese Middle Mountains. In a detailed watershed study it was shown that the overall soil fertility is poor, forest soils display the poorest conditions as a result of biomass removal, and sustaining agriculture is questionable due to the transformation from traditional to multiple cropping systems. Parent material is a significant factor influencing low phosphorus status while insufficient inputs create deficiencies in total carbon, nitrogen and bases. A nutrient budget model was developed to assess inputs, redistribution and losses relative to soil fertility. Yield, input and management data obtained from farm interviews, and soil analysis data were used in the calculation of nutrient budgets. Results from modelling indicate declining soil fertility under rainfed agriculture, forest and rangelands, and marginal conditions under irrigated agriculture subject to intensive cultivation. Nutrient deficits were relatively low for irrigated rice-wheat systems, which benefit from nutrient inputs via sediments and irrigation waters, but the introduction of triple cropping showed greater deficits. Nutrient balances were most critical under rainfed maize production where 94% of the farms were in deficit. Current shortages of organic matter make elimination of nutrient deficits problematic but improvement of composting, biological N-fixation and fertilizer efficiency and reducing erosion were found to be potential options.

River loading rates are frequently determined from discharge and water chemistry relationships using regression techniques. Such methods were inadequate in a study of the Fraser River where hysteresis was present in most sampling stations. Over a 4‐year period the year‐by‐year fluctuations in hysteresis were relatively consistent but there were dramatic differences in its shape and direction between sampling stations in the same river basin. Events on two time scales were discerned: one forming minor loop relationships was related to individual storms, the other forming major loop relationships to seasonal changes. Conventional techniques are inadequate for dealing with this problem.

Asbestos‐rich serpentinitic sediments weather rapidly in acid environments and in the process trace metals are released and smectite clays are formed in the soils. A study was carried out in the Sumas River Basin in northwestern Washington State, where a landslide has exposed asbestos‐rich serpentinitic rocks. Between 1975 and 1985 the river draining the landslide has flooded several agricultural fields and on several occasions sediments that are rich in chrysotile asbestos were deposited. The analysis of soil samples from the inundated sites revealed that Ni, Cr, Co, Mn, and Mg were very high in the sediments and leached into the lower more acidic soil horizons. Laboratory extraction experiments were carried out in water and organic acid media. Under neutral and alkaline conditions little chemical breakdown was observed, but in the presence of citric and oxalic acid more than 50% of Ni and Cr is removed by artificial weathering at room temperature. At the same time Mg is removed from the asbestos fiber structure as shown by the energy dispersive x‐ray spectroscopy (EDX) analysis.