The concentrations of rare earth elements （REEs） in the soil extracts and soil solutions from two different alluvial soil profiles irrigated with sewage were measured using inductively coupled plasma-mass spectrometry. The results showed that the REE concentrations in the soil extracts from soil samples affected by sewage irrigation were much higher than those in virgin soil samples. The REE concentrations in the soil extracts of the rhizophere soil were higher than those of the non-rhizophere soil. The shale-normalized REE patterns in the soil extracts from the upper soil layer affected by sewage irrigation shown middle REE （MREE） enrichment relative to light REE （LREE） and heavy REE （HREE）. This result was attributed to the MREE-rich organic colloidal material, REE-HM （humic and fulvic acids） and phosphate-REE complexations. The REE patterns in the soil extracts from deep soil little-affected by sewage irrigation showed HREE enrichment relative to LREE, which might have been caused by the preferential complexation of HREE with carbonate. The normalized La/Yb ratios in the soil extracts increased with the decrease in depth. The sewage irrigation did not affect the total REE contents and REE pattern in the soil profiles.
[Objective]The study aimed at assessing the whole value of Qilihai Wetland in Tianjin City.[Method]In this study,the whole value of Qilihai Wetland was divided into two parts,namely use value and non-use value.The use value of Qilihai Wetland was estimated by market value,travel cost,shadow project method and so forth,and the non-use value of Qilihai Wetland was assessed by contingent valuation method.[Result]The total value of Qilihai Wetland reached 1.892 billion yuan,wherein the direct use value,including animal and plant products,tourism,scientific and cultural value,was 0.539 billion yuan,accounting for 28% of total value;the indirect use value,composed of functional values in hydrology,water quality,erosion control,CO2 fixation and habitats,was up to 0.965 billion yuan,making up 51%;the non-use value totaled 0.388 billion yuan,taking up 21%.In addition,the ecological benefit of Qilihai Wetland was the maximum,accounting for 72% of total benefit,followed by economic benefit（21%）,while the social benefit was the minimum（9%）.[Conclusion]The results can provide scientific references for the effective conservation and sustainable utilization of Qilihai Wetland.
