| There are different forms of arsenic and phosphorus in the environment,and their toxicity and bioavailability show obvious differences.For example,the toxicity of trivalent arsenic is much greater than that of pentavalent arsenic,while dissolved reactive phosphorus is the main factor causing surface water eutrophication.Therefore,the accurate determination of different forms of arsenic and phosphorus is of great significance to environmental and ecological risk assessments.Active sampling,due to the processes of sample preservation,transportation and pretreatment,is prone to change the morphology of pollutants,which makes the results deviate from the true level in the environment.Therefore,it is necessary to develop an in-situ monitoring technique for the determination of arsenic and phosphorus in different forms.Diffusive gradient in thin films technique?DGT?is a new in-situ,non-destructive passive sampling technique.It has the advantages of low detection limit,simple operation and time-weighted concentration.In this paper,a DGT method based on a new binding phases was developed for the determination of inorganic arsenic and dissolved reactive phosphorus,and applied to the study of phosphorus desorption behavior in soil.The main research contents and results are as follows.A new diffusive gradients in thin films sampling method?DGT?with a CeO2/ZrO2 mixed binding gel was developed for the measurement of As???and As???in water and sediment.New CeO2/ZrO2 binding gel showed efficient adsorption toward As???and As???and was better than CeO2 gel and ZrO2 gels.The effective capacities of CeO2/ZrO2-DGT for As?III?and As?V?were 77.8?g and 58.1?g per device,respectively.Solution pH?4.019.01?and ionic strength?0.050.75 M?had no effects on the uptake of As???and As???by CeO2/ZrO2-DGT.The masses of As???and As???accumulated by the DGT increased linearly with time?R2>0.99?up to 72 h for tap water and synthetic seawater samples.Limits of detection?LODs?of As???and As???by CeO2/ZrO2-DGT coupled with an on-line hydride generation atomic fluorescence spectrometry?HG-AFS?were 0.06?g/L and 0.08?g/L,respectively.The method was used for measuring As???and As???in surface and sediment of several reservoirs in Dalian.The measured concentrations of As???and As???were 0.130.14?g/L and 0.200.25?g/L in the surface water and 0.381.82?g/L and 0.693.46?g/L in sediment.A new method for determination of dissolved reactive phosphorus in pore water of soil-biogas slags was established based on CeO2-DGT.The concentration of dissolved active phosphorus in soil determined by CeO2-DGT are 119457?g/L.After adding Biogas residue in the soils,the concentration of dissolved active phosphorus in pore water of soil-biogas residues were 19482678?g/L.There was a good correlation?r=0.9944?between the concentration of dissolved active phosphorus in pore water determined by CeO2-DGT and the concentration determined by centrifugation method.DIFS model was used to fit the phosphorus supply capacity?R value,the ratio of dissolved active phosphorus concentration in pore water determined by DGT and centrifugation.?of soil and soil-biogas residue,and the kinetic parameters of phosphorus in soil and soil-biogas residue were obtained.The results showed that the desorption constants(k-1)of soil and soil-biogas residue were 1.62×10-68.65×10-5 s-1 and 1.02×10-64.45×10-6 s-1;the distribution coefficients?Kd?were 40.67205.11 cm3/g and 94.36366.96 cm3/g;the response time?Tc?were 43.81701s and 1171.51852.8 s.The increase of Kd after the application of biogas residue indicated that the solid-phase replenishment pool of soil-biogas residue increases and its replenishment capacity could be maintained for a longer sampling time.The decrease of k-1 and the increase of Tc indicated that the resupply of solid phase contributed little to the dissolved reactive phosphorus in the pore water of soil-biogas residue.The supply of dissolved reactive phosphorus in the pore water of soil-biogas residue was mainly controlled by the process of plant uptake of phosphorus.The CeO2/ZrO2-DGT developed in this paper has been successfully applied to the determination of As?III?and As?V?in surface water and sediments of reservoirs.It has the advantages of reducing detection limit,simple operation and low cost.CeO2-DGT was developed to determine the concentration of dissolved reactive phosphorus in soil and soil-biogas slags,and it was used to determine the kinetic parameters of phosphorus desorption in soil and soil-biogas slags.These parameters will help us to have a deeper understanding of phosphorus release mechanism. |
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