Fluoride distibution and the effect of some ions along Alexandria coastal Mediterranean seawater of Egypt

The coastal seawater of Mediterranean of Alexandria receives large amount of discharged waters containing industrial wastes, sewage, and agricultural and domestic drainage. Fluoride and some parameters were(chemical and physical) determined. The data gave indication that the content and the amount of the discharged water largely affect the chemical composition of the coastal water. Stepwise regression analysis was highly significant and the model was very fruitful, where the observed and calculated values were mostly concordant. This may indicated that there was a relation between fluoride content in coastal seawater and its content in the discharged water.     

不同离子对黑土胶体在土壤中运移的影响

黑土样品采自于黑龙江海伦市,提取胶体并对其主要理化性质进行定性定量表征,通过淋滤实验研究胶体在土柱中的运移特征以及不同离子及其强度对胶体运移的影响。结果显示:所提取胶体粒径与理论计算基本吻合,粒径主要分布在2~5μm;当pH由4上升到9时,胶体的zeta电位则由-26.43mV降低到-34.52mV;红外光谱显示胶体颗粒的有机机团主要为-OH、CH-、C=O、多糖;X射线衍射表明其主要矿物组成是石英(56.9%)。不同离子及其强度对胶体的在土壤中的运移有较为明显的影响,当pH由4增加到9时,k值由6.020×10-4降低至3.858×10-4,Ca2+、K+、Na+当离子强度由0.5mmol/L变化到0.001mmol/L时,k值分别由6.087×10-4降低至4.024×10-4、5.518×10-4降低至3.818×10-4、5.401×10-4降低至4.109×10-4。     

IMPACTS OF SILVICULTURE ON FLATWOODS RUNOFF,WATER QUALITY,AND NUTRIENT BUDGETS1

ABSTRACT: Three forest watersheds were isolated by roads in poorly drained flatwoods of Florida. After 12 months of baseline calibration the forest in one watershed was harvested and regenerated with minimum disturbance, in the second watershed with maximum disturbance from common practices, and in the third watershed left intact as a control. Water yields from the maximum treatments increased a significant 250 percent while that from the minimum treatments increased 117 percent as compared to the control. Weed vegetation remaining after the minimum treatment continued significant water use. The water yield increases lasted only for one year. Water quality was reduced by both treatments with the most effect immediately after the maximum disturbance. Absolute levels of suspended sediments, potassium, and calcium remained relatively low. The maximum treatment caused significant changes in net cation balances only for one year. The information shows relative little effect of silvicultural practices in flatwoods on water quality as compared to data from upland forests. Water yield increases may be manipulated by the degree of harvest and weed control practices.     

An assessment of the risks associated with PCDDs and PCDFs following the application of sewage sludge to agricultural land in the UK

A model has been developed to describe the transfer of PCDDs and PCDFs from sludge-amended soils to the human foodchain. The model is conservative and assumes that all foods consumed by an individual are derived from sludge-amended soils. Predicted concentrations of PCDDs and PCDFs in potatoes, cereals, root vegetables and leafy vegetables were in close agreement with mean concentrations reported in the food survey conducted by MAFF in the UK. Predicted concentrations in milk were well below the Maximum Tolerable Concentration adopted by MAFF. Assuming a half-life of ten years in sludge-amended soils, the maximum estimated incremental daily intake (IDI) predicted by the model following ten applications of sludge to agricultural land was 0.80 pg I-TEQ kg⁻¹ day⁻¹, representing an increase of approximately 45% on current levels of background exposure. For an individual whose diet is solely derived from sludge-amended soils, the total exposure is predicted to be approximately 181 pg I-TEQ day⁻¹ or 2.6 pg I-TEQ kg⁻¹ day⁻¹. This compares with an average background exposure of approximately 2 pg I-TEQ kg⁻¹ day⁻¹, well within the TDI of 10 pg I-TEQ kg⁻¹ day⁻¹ and indicates that the application of sewage sludge to agricultural land under the conditions assumed would not appear to present a significant health risk under the conservative scenarios considered in this assessment.     

MODELING THE HYDROLOGIC IMPACTS OF FOREST HARVESTING ON FLORIDA FLATWOODS1

ABSTRACT: The great temporal and spatial variability of pine flat-woods hydrology suggests traditional short-term field methods may not be effective in evaluating the hydrologic effects of forest management. The FLATWOODS model was developed, calibrated and validated specifically for the cypress wetland-pine upland landscape. The model was applied to two typical flatwoods sites in north central Florida. Three harvesting treatments (Wetland Harvesting, Wetland + Upland Harvesting, and Control) under three typical climatic conditions (dry, wet, and normal precipitation years) were simulated to study the potential first-year effects of common forest harvesting activities on flatwoods. Long-term (15 years) simulation was conducted to evaluate the hydrologic impacts at different stages of stand rotation. This simulation study concludes that forest harvesting has substantial effects on hydrology during dry periods and clear cutting of both wetlands and uplands has greater influence on the water regimes than partial harvesting. Compared to hilly regions, forest harvesting in the Florida coastal plains has less impact on water yield.     

The importance of considering spatial attributes in evaluating estuarine habitat condition: the South Carolina experience

The South Carolina Estuarine and Coastal Assessment Program (SCECAP) was initiated in 1999 to assess the condition of the state's coastal habitats using multiple measures of water quality, sediment quality, and biological condition. Sampling was subsequently expanded to include components required for the National Coastal Assessment (Coastal 2000) Program. Habitats are classified as either tidal creeks (<#60; 100 meters in width) or larger open water bodies. Approximately 30 sites are sampled within each habitat during the summer months using a probability-based random sampling design. Results obtained from the first two years of sampling documented significant differences in several water quality parameters (DO, salinity, pH, turbidity, fecal coliform bacteria, total nitrogen, TKN, total phosphorus) and biological measures (chlorophyll-a, finfish and crustacean abundance and biomass and a number of benthic species) between the tidal creek and open water habitats. These differences highlight the value of partitioning shallow water habitats separately from the larger open water bodies traditionally sampled in estuarine monitoring programs, especially since tidal creeks serve as critical nursery areas for many species. Based on the differences observed, there is a clear need to identify different physical and biological thresholds for evaluating the condition of each habitat type.     

MODELING THE FOREST HYDROLOGY OF WETLAND-UPLAND ECOSYSTEMS IN FLORIDA1

ABSTRACT: Few hydrological models are applicable to pine flat-woods which are a mosaic of pine plantations and cypress swamps. Unique features of this system include ephemeral sheet flow, shallow dynamic ground water table, high rainfall and evapotranspiration, and high infiltration rates. A FLATWOODS model has been developed specifically for the cypress wetland-pine upland landscape by integrating a 2-D ground water model, a Variable-Source-Area (VAS)-based surface flow model, an evapotranspiration (ET) model, and an unsaturated water flow model. The FLATWOODS model utilizes a distributed approach by dividing the entire simulation domain into regular cells. It has the capability to continuously simulate the daily values of ground water table depth, ET, and soil moisture content distributions in a watershed. The model has been calibrated and validated with a 15-year runoff and a four-year ground water table data set from two different pine flat woods research watersheds in northern Florida. This model may be used for predicting hydrologic impacts of different forest management practices in the coastal regions.     

Fluoride distribution and the effect of some ions along Alexandria coastal Mediterranean seawater of Egypt

The coastal seawater of Mediterranean of Alexandria receives large amount of discharged waters containing industrial wastes, sewage, and agricultural and domestic drainage. Fluoride and some parameters were( chemical and physical) determined. The data gave indication that the content and the amount of the discharged water largely affect the chemical composition of the coastal water. Stepwise regression analysis was highly significant and the model was very fruitful, where the observed and calculated values were mostly concordant. This may indicated that there was a relation between fluoride content in cosslal seawater and its content in the discharged water.