Changes in land-use or management practices may affect water outflow, sediment, nutrients and pesticides loads. Thus, there is an increasing demand for quantitative information at the watershed scale that would help decision makers or planners to take appropriate decisions. This paper evaluates by a modeling approach the impact of farming practices and land-use changes on water discharge, sediment and NO3-N loads at the outlet of a 51.29 km2 watershed of central Iowa (Walnut Creek watershed). This intensively farmed (corn-soybean rotation) watershed is characterized by a flat topography with tiles and potholes. Nine scenarios of management practices (nitrogen application rates: increase of current rate by 20, 40%, decrease of current rate by 20, 40 and 60%; no tillage) and land-use changes (from corn-soybean rotation to winter wheat and pasture) were tested over a 30 yr simulated period. The selected model (Soil and Water Assessment Tool, SWAT) was first validated using observed flow, sediment and nutrient loads from 1991 to 1998. Scenarios of N application rates did not affect water and sediment annual budgets but did so for NO3-N loads. Lessening the N rate by 20, 40 and 60% in corn-soybean fields decreased mean NO3-N annual loads by 22, 50 and 95%, respectively, with greatest differences during late spring. On the other hand, increasing input N by 20 and 40% enhanced NO3-N loads by 25 and 49%, respectively. When replacing corn-soybean rotation by winter wheat, NO3-N loads increased in early fall, immediately after harvest. Pasture installation with or without fertilization lessened flow discharge, NO3-N and sediment delivery by 58, 97 and 50%, respectively. No-tillage practices did not significantly affect the water resource and sediment loads. Finally, such realistic predictions of the impact of farming systems scenarios over a long period are discussed regarding environmental processes involved.

Nutrient-rich, highly acidic leachate draining from a coastalphosphogypsum storage site located at a phosphate fertilizer manufacturing company posed potentially harmful environmental effects to the coastal ecosystem. This study evaluated the chemical characteristics of the phosphogypsum and the hydrogeological characteristics of the surroundings. Hydraulic and chemical properties of the leachate draining from the site were also evaluated. The leachate is nutrient-rich and very acidic and discharges into the sea. The leachate and seawater are hydraulically connected through highly-permeable riprap placed at the toe of the stack. The chemical quality of the leachate and its drainage rate showed large variations depending on the location of the well, indicating heterogeneous hydraulic conditions. A vertical barrier system consisting of horizontal drainage wells and vertical leachate-collecting wells is suggested, in order to contain and collect the leachate. A back-up system of soil-bentonite cut-off walls is suggested to control leachate discharge to the sea.

A statewide total gaseous mercury (TGM) monitoring campaign was conducted from January 1997 to December 1999 in the State of Connecticut, U.S.A. Eight monitoring sites with different characteristics of geographical location (coastal vs. interior) and land use (rural vs. urban) were included in the monitoring program. Statistical procedures were utilized to evaluate the temporal trend and spatial distribution of the TGM concentration in the State, and the influence of long-range transport from non-local sources. The statewide mean TGM concentration was 2.08 ng m⁻³. The annual mean concentration had no significant differences among the three years of measurements for all the sites. Weak seasonal variations were detected in the State with higher ambient TGM concentration found in warmer seasons. Urban areas in general had higher TGM concentrations than rural areas. The effect of site location of the monitoring sites on TGM concentration was interacted with land use characteristics. Waterbury site with extremely high concentration measurements was the major cause for this interaction. The long-range transport of TGM from remote sources showed an important influence on local ambient concentrations, by explaining over 45% of the total variance of the ambient TGM concentration for most sites. Local sources were responsible for the extremely high TGM concentration in the Waterbury site. The TGM concentrations at Voluntown, Hammonasset and Avery Point in southeast Connecticut were likely to be affected by some local sources.

The results of spatial and temporal distribution of acidic and basic air pollutants in ambient air around Hsinchu Science-Based Industrial Park (SBIP), Taiwan during August 2000 to October 2001 are presented. The sampling was performed on 13 different sites around the SBIP for 12 hrs each every month, and a total of 195 samples were collected. The effect of geographical and meteorologicalconditions, and production volume of the SBIP on the variation of pollutant's concentration was investigated. The spatial distribution shows that comparatively higher concentration of pollutants was found on the sites, which are either low in altitude such as the WS (west-southern) part of SBIP, in the downwind location or close to the factories. In case the wind velocity was low, i.e. below 2 m s⁻¹, the concentration of pollutant tended to increase and became uniformly distributed around the science park. The temporal distribution shows a decrease in ambient concentration of pollutants from February to June 2001, mainly due to the decline in the production volume of the SBIP in this period. During the whole period of investigation, the concentration of most of the species (except HF) was found to be lower than the factory-surrounding air quality standard of Taiwan, but in some cases it was higher than the AALG.

Eighty soil cores were collected from a residential area adjacent to an automobile battery manufacturing facility to determine the level and variability of lead concentrations in the soil. Results of ICP-MS on HNO₃ digestions showed lead concentrations in the residential soil as high as 2760 mg kg⁻¹. High variability of lead concentrations of two to three times over short distances, less than a meter, indicated the necessity of remediating the entire soil area based on a clean-up level of 400 mg kg⁻¹. To delineate areas of soil requiring no remediation at a high level of confidence would have required a more extensive soil sampling survey. High lead concentrations in the residential soil to a depth of approximately 15 cm indicated remediationof residential soil to at least this depth may be necessary. Overall, the high variability of lead concentrations in the residential soil was consistent with a soil having been disturbed by residential activity and illustrated the difficulty in using a single sample per residentialyard for making correct remediation decisions.

Precipitation samples were collected at two coastal sites on the Korean Peninsula, Kangwha on the western coast and Yangyang on the eastern coast, from September 1991 to February 1997. The samples were analyzed for concentrations of major ions, in addition to pH and electrical conductivity. The annual volume-weighted mean pH values were 4.89 and 5.05 at Kangwha and Yangyang, respectively. The pH was generally lower at Kangwha than that at Yangyang, especially during the winter, because of reduced neutralizing inputs and greater acid inputs in winter. Dominant ions were different with NH₄ ⁺ and SO₄ ²⁻ most important at Kangwha and Na⁺ and Cl⁻ at Yangyang. Neglecting sea salt components, nss-SO₄ ²⁻ and NO₃ ⁻ were important anions and nss-Ca²⁺ and NH₄ ⁺ were important cations at both sites. Concentrations of these ions were 1.2–1.6 times higher at Kangwha than at Yangyang. Annual mean concentrations of these ions varied little during the study, while larger seasonal variations were observed. Annual mean nss-SO₄ ²⁻/NO₃ ⁻ ratios at Kangwha and Yangyang were 2.8 and 2.6. The 5 yr annual mean values of nss-SO₄ ²⁻/NO₃ ⁻ showed no trend at Kangwha but a decreasing tendency at Yangyang. The decreasing trend is similar to the decreasing trend in emissions of SO₂/NOₓ in South Korea. Regional differences in chemical composition between Kangwha and Yangyang appear to be associated with long-range transport of acidic gases and alkaline dust originated from other regions.

Passive capillary samplers, which sample water from the vadose zone via a hanging water column in a fiberglass wick, have shown potential to provide better estimates of actual soil percolation fluxes than alternative field methods. Unsaturated and saturated flows (water and solutes) are extracted continuously and without external vacuum generator from a nondisturbed soil volume, through a significant area (typically 600cm2). In order to achieve a minimal disturbance of the native flow regime, the wick type (hydraulic conductivity and section), length and number and the contact area have to be dimensioned to match as close as possible the expected soil pressure/flow conditions. First, the Hydrus 2D code (Simunek et al., 1999) solving the Richards equation for simulating two dimensional unsaturated flow was used to evaluate the uncertainties in flux estimation by such passive capillary samplers. Two sources of uncertainties were examined. Those associated with the theoretical assumptions of the dimensioning of the wick and those associated to experimental uncertainties. A numerical experimentation was conducted on two reference soils submitted to a 11 days actual hyetograph. Results showed that an analytical dimensioning method proposed in the literature is relevant. But significant errors on the observed fluxes occur when the soil and wick properties do not exactly match, which is the common case since the range of available characteristics of fiberglass wicks is limited. Also, uncertainties in the hydraulic conductivity properties of the soil, in wick length appear to have an important influence on the representativity of the wick fluxes against the actual soil drainage fluxes. Elsewhere, eight such samplers have been installed for an in situ long term experimentation ,initiated this year in the Ardière Watershed (France). The objective is to measure water and pesticides percolation fluxes, at a 50cm depth under a grassed strip receiving contaminated runoff. Flow rate and pesticide concentration in surface runoff water are also measured so as to determine the soil boundary condition above each sampler. Soil water content and soil matric potential are measured at three different depth very close to each instrumented profile in order to explain the volumes extracted by each sampler. We present here the experimental methodology and first results obtained with simulated runoff events.

On s'interroge sur la qualité physico-chimique et biologique de l'eau des rivières en étudiant les zones actives, les flux et biodisponibilité du phosphore (région du lac Léman), les zones actives et production de matières en suspension (Basse-Normandie) et les zones tampons et teneurs en nitrate dans les cours d'eau (Basse-Normandie). | Wonders about the physicochemical and biological quality of the water of the rivers by studying the active zones, flows and biodisponibility of phosphorus (area of the lake Léman), the active zones and production of suspended matter (Low-Normandy) and the buffer zones and nitrate contents in the rivers (Low-Normandy).

On étudie le phénomène de la diminution de la population des salmonidés, dû à la modification de la gestion de l'espace agricole et l'intensification des pratiques culturales, associées à des conditions climatiques et pédologiques particulières.

Background, Aims and Scope: Current dredged material disposal alternatives have several limitations. Options for dealing with dredged materials include leaving them alone, capping them with clean sediments, placing them in confined facilities, disposing of them at upland sites, treating them chemically, or using them for wetlands creation or other beneficial uses. The ability to reuse lake-dredge materials (LDM) for agricultural purposes is important because it reduces the need for offshore disposal and provides an alternative to disposal of the materials in landfills. Often these materials can be obtained at little or no cost to the farmers or landowners. Thus, forage production offers an alternative to waste management since nutrients in the LDM are recycled into crops that are not directly consumed by humans. The objective of this study (Part 2) were to: (1) assess dredge materials from Lake Panasoffkee, Florida as a soil amendment to establish bahiagrass (BG) in a subtropical beef cattle pasture in Sumter County, Florida; and (2) determine the effect of LDM application on the crude protein (CP) and nutrient uptake of BG. This series of two papers aims at providing assessment of the efficacy of lake-dredged materials especially its implication to environment (soil quality, Part 1) and agriculture (forage quality and pasture establishment. Part 2). Methods: The experimental treatments that were evaluated consisted of different ratios of natural soil (NS) to LDM: LDMO (100% NS:0% LDM); LDM25 (75% NS:25% LDM); LDM50 (50% NS:50% LDM); LDM75 (25% NS:75% LDM); and LDM100 (0% NS:100% LDM). Bahiagrass plots at its early establishment were cut to a 5-cm stubble height on Julian days 112 and harvested to the same stubble height on Julian days 238 and on Julian days 546 following the double-ring method. Field layout was based on the principle of a completely randomized block design with four replications. Plant samples harvested at 546 Julian days were ground to pass through a 1-mm mesh screen in a Wiley mill. Ground forage was analyzed for crude protein. Ground forage samples were also analyzed for tissue P, K, Ca, Mg, Mn, Cu, Fe, Al, and Mo concentrations using an ICP spectroscopy. The effects of dredged materials addition on forage yield and on crude protein and nutrient uptake that were taken at 546 Julian days were analyzed statistically following the PROC ANOVA procedures. Results and Discussion: Part 1 of this study demonstrated that the heavy and trace metal contents of LDM were below the probable effect levels and threshold effect levels. As such, the agricultural or livestock industry could utilize these LDM to produce forages. Results showed consistently and significantly (p < or = 0.001) higher BG biomass production and CP from plots amended with LDM than those of BG planted on plots with 0% LDM. Forage yield of BG during its establishment increased linearly (Forage Yield = 1724.3 + 25.64*LDM; R2 = 0.83; p < or = 0.0001) with increasing rates of LDM application. The CP of BG also varied significantly with varying levels of LDM applications. The tissues of BG with 100% LDM had the greatest CP content while the lowest CP content was from the control plots (LDMO). The CP of BG increased linearly with increasing rates of LDM application. The crude protein response to BG application can be described by a linear equation: Crude Protein = 10.38 + 0.052*LDM; R2 = 0.85 p < or = 0.0001. Addition of LDM had increased the levels of Ca by about 1811 % when compared with the level of soil Ca among plots with no LDM application. Liming the field could have some direct and indirect effects on the chemical status of the soils. The physiological functions performed by Ca in plants are not clearly defined, but it has been suggested that Ca favors the formation of and increases the protein content of mitochondria. Conclusions: Beneficial uses of dredged materials from LP, Florida are both economical and environmental. Often these materials can be obtained at little or no cost to the farmers or landowners. Results showed that dredged materials can be used as soil amendments (lime and fertilizer) for early establishment of BG in beef cattle pastures. Environmentally, dredging of sediments that are rich in CaCO3 should restore the 19.4-sq km LP by removing natural sediments from the lake bottom to improve the fishery, water quality, and navigation of the lake. The nutritional uptake of BG grown in unfertile sandy soils of Sumter County was enhanced significantly (p < or = 0.001) by LDM addition. Uptake of TKN, TP, K, Ca, and Mg were remarkably increased as a result of LDM. Recommendation and Outlook: Land application of LDM from LP may not only provide substantial benefits that will enhance the environment, community, and society in south Florida, but also in other parts of the world especially those areas with forage-based beef cattle pastures and similar climatic conditions. The heavy and trace metal contents of these materials were below the PEL and TEL (see Part 1). As such, the agricultural or livestock industry could utilize these LDM to produce forages. LDM should be regarded as a beneficial resource, as a part of the ecological system. Although our results have demonstrated the favorable and beneficial effects of added LDM on the early establishment of BG in pasture fields., further studies are still needed not only in pastures of south Florida, but also in other areas with subtropical or tropical climatic conditions to determine whether the environmental and ecological implications of LDM application are satisfied over the longer term.