No abstract

A five-step sequential extraction procedure was applied to organic-rich soil samples from five soil profiles situated 1 -8 km from a zinc smelter. The partitioning of Zn, Cd, Pb, and Cu into five operationally defined fractions (exchangeable, ''carbonate''-bound, reducible, oxidizable, and residual) was studied at different soil depths down to 35 cm. In the surface soil (0 -1 cm) a major part of Pb and Cu was extracted in the oxidizable fraction, whereas for Zn and Cd slightly more was extracted in the ''carbonate''-fraction than in the other four fractions. Extracted metal proportions in the oxidizable fraction were respectively of the order of 30%, 20%, 50%, and 80% for Zn, Cd, Pb, and Cu in the surface soil for all sites, but these proportions decreased with soil depth. In the surface soil less than 20% of all the elements were extracted in the residual fraction, but the proportions associated with this fraction generally increased with soil depth. In the C-horizon, differences in extracted proportions of Pb and Cu in the residual fraction were probably due to geochemical factors, whereas for Zn the low extracted proportion at a highly contaminated site (20%) may be due to Zn migration to the C-horizon at this site. For Cd the extracted proportions in the C-horizon were lower than for the other elements, generally below 20%, presumably because Cd is weaker in terms of its adsorption to the soil than the other elements studied. Total concentrations of the metals decreased strongly with increasing distance from the smelter, but less systematic differences were observed for their distributions among fractions. Potentially bioavailable metal proportions (exchangeable þ ''carbonate''-bound fraction) in the surface soil were about 50%, 60%, 20%, and 10% for Zn, Cd, Pb, and Cu, respectively. In C-horizon soil the mobility sequence Cd4Zn!Pb ¼ Cu was generally observed. The present results indicate that the concentrations and chemical fractionation of Zn, Pb, and Cd in these soils represent a considerable risk to natural terrestrial food chains.

No abstract

Many variables are regularly measured in frequently taken water samples from sewage treatment plants. This results in large data sets with associated high costs. The total phosphorus in the sewage is of great importance since it is an indicator of the total pollution concentration, but no direct on-line analyser is available.This paper concentrates on finding an indirect model for total phosphorus content (tot-P) based on other variables routineiy analysed in inlet water to a Nonvegian sewage treatment plant. Data from 1993 were used for calibration and the developed models were validated with data from 1994. A PLS model for tot-P based on eight X-variables gave the lowest test set RMSEP (0.35). Models based on fewer X-variables gave higher RMSEP, indicating that more X-variables stabilize the models. For practica1 use a model for tot-P based on orthophosphate, total organic carbon and suspended solids seems to be a good compromise between simplicity and predictability. With this model the total phosphorus content was predicted with an average deviation (RMSEP) of 0.45 mgP 1 -' from the measured values, giving a relative precision of 20%. Since the X-variables in the model can be measured on-line, this model can be used as an input for coagulant dosing in the sewage treatment plant and for process control. For this purpose the 20% relative precision is quite acceptable. Preliminary results of PLS models for alkalinity, chemical oxygen demand and biologicai oxygen demand indicate that useful modeis can also be developed for these Y-variables.The use of these PLS models has a substantial cost saving potential. They may replace traditional chemicai analysis, speed up the time from sampling to results and represent a possible input to on-line process control. O 1996 by John Wiley & Sons, Ltd.

Many variables are regularly measured in frequently taken water samples from sewage treatment plants. This results in large data sets with associated high costs. The total phosphorus in the sewage is of great importance since it is an indicator of the total pollution concentration, but no direct on-line analyser is available.This paper concentrates on finding an indirect model for total phosphorus content (tot-P) based on other variables routineiy analysed in inlet water to a Nonvegian sewage treatment plant. Data from 1993 were used for calibration and the developed models were validated with data from 1994. A PLS model for tot-P based on eight X-variables gave the lowest test set RMSEP (0.35). Models based on fewer X-variables gave higher RMSEP, indicating that more X-variables stabilize the models. For practica1 use a model for tot-P based on orthophosphate, total organic carbon and suspended solids seems to be a good compromise between simplicity and predictability. With this model the total phosphorus content was predicted with an average deviation (RMSEP) of 0.45 mgP 1 -' from the measured values, giving a relative precision of 20%. Since the X-variables in the model can be measured on-line, this model can be used as an input for coagulant dosing in the sewage treatment plant and for process control. For this purpose the 20% relative precision is quite acceptable. Preliminary results of PLS models for alkalinity, chemical oxygen demand and biologicai oxygen demand indicate that useful modeis can also be developed for these Y-variables.The use of these PLS models has a substantial cost saving potential. They may replace traditional chemicai analysis, speed up the time from sampling to results and represent a possible input to on-line process control. O 1996 by John Wiley & Sons, Ltd.