Research studies have modified traditional substances to seek fast-acting removal of phosphorus in constructed wetlands (CWs) and ecological dams, rather than develop a brand-new nano-adsorbent. This work synthesized FeCa-based layered double hydroxide (FeCa-LDH) with a chemical co-precipitation method, and the performance, mechanism and factors of phosphorus removal were investigated. FeCa-LDH showed a marked ability to adsorb phosphorus from waste water, with a removal efficiency of 94.4 % and 98.2 % in CWs and ecological dams, respectively. Both FTIR and XPS spectrum evidenced that FeCa-LDH removed phosphorus via electrostatic and hydrogen-bonding adsorption, as well as a coordination reaction and interlayer anion exchange. FeCa-LDH showed a higher capacity to remove phosphorus in alkaline and neutral waste water than in acid conditions. Co-occurrence anions, which influenced the efficiency of the phosphorus removal capacity are considered in the sequence below: CO32- ≈ HCO3- > SO42- > NO3-. Innovatively, FeCa-LDH was not affected by the low-temperature limitation for CWs, and phosphorus removal efficiency at 5 ℃ was almost equal to that at 25 ℃. These results cast a new idea on the construction, application and phosphorus removal performance of CWs and ecological dams.
The black soil region of the northeast is an important marketable grain base and a main grain producing area,playing extremely important function on ensuring the grain security of China.The present severe soil and water loss has seriously affected the land productivity and the output of grain.The paper discusses the influence to physical,chemical and biological properties for soil and water loss in black soil region of the northeast systematically and analyzes the main effect of soil and water conservation measures.
Mojiagou Watershed was chosen to study small watershed comprehensive control.It is one subbasin in Shitoukoumen Reservoir Watershed which is the important drinking water source for Changchun City,the capital city of Jilin Province.Five structural management practices,i.e.contour farming,terrace cultivation,grain to green,chemical fertilizer reduction,and constructed wetland,are selected to reduce pollution loads.The optimal management complete model consists of two interacting components: an objective function and many constraints.The objective function is to minimize the measure construction cost.The constraints are: the reservoir water quality standards,the area to be transformed and nonnegative.The decisive factors are: the area constructed with terraces and the fertilizer applied.The optimal management model is used to simulate pollutant concentration in Mojiagou Watershed under three stages of twenty-one possible schemes.The resulting practical scenarios for three stages are achieved.In 2011 to 2020,the concentration for TP can meet grade Ⅲ standard(≤0.05 mg·L-1) in reservoir when the corn fields of less than five degree in gradient are farmed along the contour line,terrace area no change and other fields turn grain to green.To attain TP grade Ⅱ(≤0.025 mg·L-1) in 2021 to 2030,there is a need of 0.03 km2 constructed wetland based on the first strategy.With all corn fields be turned to grow trees and no fertilizer application,the water quality will meet TP grade Ⅰ standard in 2031 to 2050.The modeling framework developed(≤0.01 mg·L-1) in the present study is an efficient tool for planning a watershed-wide implementation of pollution control practices for mitigating runoff pollution impact on the receiving water bodies.
Diffuse pollution from surface runoff in slope cropland is the key source impacting drinking water quality.Rainfall,soil and runoff are interacted during the process of diffuse pollution yield.Runoff and soil solute transport in rain events were collected and monitored by movable plots.The diffuse pollution loads were obtained.The contributions of rainfall and soil solute showed that dissolved total nitrogen and phosphorus loads from rainfall accounted for 58% and 67% of dissolved total nitrogen and phosphorus in runoff,respectively.Nitrogen and phosphorus from rainfall was delivered by surface runoff to other systems.However,nitrate in runoff resulted from soil dissolved nitrogen transport.The interacting depth of rainfall-runoff-soil solute simplified the process of quantifyiog diffuse pollution loads in small watershed.It helps to make pollution control plan for improving water quality.
Marsh has important ecological and environmental functions and is sensitive to the global climate change, while the variation of soil temperature could better indicate the climate fluctuation. Our study showed that the annual and seasonal dynamic changes of soil temperature in marsh showed distinctly "sinusoid" character curve, whereas the mean annual temperature of different soil depths showed "U" feature. From May to September, the mean temperature at the topsoil (10 cm) of uncultivated marsh was 11.69 +/- 3.04 degrees C, while that of cultivated marsh was 15.80 +/- 3.41 degrees C. The soil respiration rate of uncultivated marsh in August and September was 156.41 +/- 76.91 mg x m(-2) x h(-1) and 116.75 +/- 57.43 mg x m(-2) x h(-1), accounted for 14.6% and 13.1% of that of cultivated marsh, respectively. The soil temperature was significantly positively correlated with soil respiration.
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