Hydrogeologic controls of surface-water chemistry in the Adirondack region of New York State

Relationships between surface-water discharge, water chemistry, and watershed geology were investigated to evaluate factors affecting the sensitivity of drainage waters in the Adirondack region of New York to acidification by atmospheric deposition. Instantaneous discharge per unit area was derived from relationships between flow and staff-gage readings at 10 drainage basins throughout the region. The average chemical composition of the waters was assessed from monthly samples collected from July 1982 through July 1984. The ratio of flow at the 50-percent exceedence level to the flow at the 95-percent exceedence level of flow duration was negatively correlated with mean values of alkalinity or acid-neutralizing capacity (ANC), sum of basic cations (SBC), and dissolved silica, for basins containing predominantly aluminosilicate minerals and little or no carbonate-bearing minerals. Low ratios are indicative of systems in which flow is predominately derived from surface- and ground-water storage, whereas high ratios are characteristic of watersheds with variable flow that is largely derived from surface runoff.In an evaluation of two representative surface-water sites, concentrations of ANC, SBC, and dissolved silica, derived primarily from soil mineral weathering reactions. decreased with increasing flow. Furthermore, the ANC was highest at low flow when the percentage of streamflow derived from ground water was maximum. As flow increased, the ANC decreased because the contribution of dilute surface runoff and lateral flow through the shallow acidic soil horizons to total flow increased. Basins having relatively high ground-water contributions to total flow, in general, have large deposits of thick till or stratified drift. A major factor controlling the sensitivity of these streams and lakes to acidification is the relative contribution of ground water to total discharge.     

Subsidy‐stress and multiple‐stressor effects along gradients of deposited fine sediment and dissolved nutrients in a regional set of streams and rivers

1. Stream managers need to understand relationships between multiple stressors and ecological responses. We examined responses of benthic invertebrates and algae along two land‐use‐related stressor gradients of concern in running waters. Our correlative study of the consequences of augmented deposited fine sediment and nutrient concentrations was conducted in a regional set of streams and rivers monitored by a water management authority in New Zealand and incorporated a wide range of catchment geologies and stream orders. 2. We used multiple linear regression analysis and an information‐theoretic approach to select the best predictive models for our biological response variables by testing multiple competing hypotheses that include nonlinear subsidy‐stress relationships and interactive effects between the two stressors. 3. Patterns consistent with a subsidy‐stress response to increasing dissolved inorganic nitrogen concentration were found for the relative abundances of the common invertebrate genera Pycnocentrodes and Deleatidium and for the relative abundance of total individuals in the EPT orders (Ephemeroptera, Plecoptera, Trichoptera). 4. Fine sediment seemed the more pervasive stressor, apparently counteracting and overwhelming any initial subsidy effect of increased nutrients, and accounting for more of the variance in biological response variables. Relationships with high nutrient concentrations were weaker and modelled with less certainty, probably reflecting the indirect modes of action of nutrients compared to those underlying sediment effects. Nevertheless, in several cases, the models indicated that nutrients interacted synergistically with fine sediment, lending further weight to the conclusion that managers need to address both stressors to achieve the best outcomes.     

小兴安岭西南部森林对洪水径流的影响

小兴安岭西南部森林对洪水径流的影响张庆费周晓峰，王传宽（华东师范大学环境科学系上海２０００６２）（东北林业大学林学系哈尔滨１５００４０）ＩｎｆｌｕｅｎｃｅｏｆＦｏｒｅｓｔｏｎＦｌｏｏｄＲｕｎｏｆｆａｔｔｈｅＳｏｕｔｈｗｅｘｔｅｒｎＰａｒｔｏｆＸｉａｏ...     

Simulated Phosphorus and Sediment Loadings in Two Representative Subbasins of the Illinois River

Quantification of the factors affecting phosphorus (P) loading to surface waters is important in assessing the contribution from agricultural activities to water quality. This study investigated the long-term impact of applications of P in poultry litter on the loadings of P and sediment to streams in two subbasins of the Illinois River Watershed. The influences of application rate and environmental characteristics were examined utilizing a transport model, a geographical information system (GIS), and 30 years of daily weather data. Simulated runoff and sediment concentrations of P increased linearly with poultry litter application rate. Most P loadings to streams were in the dissolved form, as overall sediment transport was low, particularly in areas with excellent stands of forage. Because only pasturelands received poultry litter and the initial concentrations of P in the soils in the forested areas were low, the forested areas contributed little runoff and sediment P to streams. Areas of high P loadings coincided with soils having high Curve Numbers (CN) and poor internal drainage. Therefore, subbasins of the watershed containing a greater proportion of pasture and soils with poor drainage characteristics have higher loading rates to streams. Predicted runoff, sediment, and P loadings in both subbasins were highly variable.     

The importance of runoff to DDT and PCB inputs to the Sado estuary and Ria Formosa

PCB congeners, DDT and metabolites were determined in suspended sediments and in the oysterCrassostrea angulata from the upper Sado estuary over two years (1987/88 and 1990) and from Ria Formosa during 1990. Levels of DDT concentrations in suspended sediments collected in both estuarine areas, either in 1988 or 1990, increased in winter. Otherwise, PCB concentrations varied in an erratic way. A DDT enrichment was also recorded inC. angulata in winter and an increase of only PCB concentration levels in oysters of the upper Sado estuary was registered at the same period. These results suggest that, in the absence of important direct sources of PCB and DDT, runoff appears to be the major source of those compounds in both the study areas. Levels of concentrations of these pollutants in oysters reflect either their increase in the environment or changes in particle dynamics in the two estuarine areas.