Batch experiments were conducted to study the short-term biological effects of rare earth ions (La3+, Ce3+) and their mixture on the nitrogen removal in a sequencing batch reactor (SBR). The data showed that higher NH+4―N removal rate, total inorganic nitrogen removal efficiency, and denitrification efficiency were achieved at lower concentrations of rare earth elements (REEs) (<1mg/L). In the first hour of the aeration stage of SBR, the presence of REEs increased the total inorganic nitrogen removal efficiency and NH+4―N removal efficiency by 15.7% and 10%―15%, respectively. When the concentrations of REEs were higher than 1mg/L, the total inorganic nitrogen removal efficiency decreased, and nitrate was found to accumulate in the effluent. When the concentrations of REEs was up to 50.0mg/L, the total inorganic nitrogen removal efficiency was less than 30% of the control efficiency with a high level of nitrate. Lower concentrations of REEs were found to accelerate the nitrogen conversion and removal in SBR. 相似文献
Batch experiments were conducted to study the short-term biological effects of rare earth ions (La3+, Ce3+) and their mixture on the nitrogen removal in a sequencing batch reactor (SBR). The data showed that higher NH4+-N removal rate, total inorganic nitrogen removal efficiency, and denitrification efficiency were achieved at lower concentrations of rare earth elements (REEs) (<1 mg/L). In the first hour of the aeration stage of SBR, the presence of REEs increased the total inorganic nitrogen removal efficiency and NH4+-N removal efficiency by 15.7% and 10%–15%, respectively. When the concentrations of REEs were higher than 1 mg/L, the total inorganic nitrogen removal efficiency decreased, and nitrate was found to accumulate in the effluent. When the concentrations of REEs was up to 50.0 mg/L, the total inorganic nitrogen removal efficiency was less than 30% of the control efficiency with a high level of nitrate. Lower concentrations of REEs were found to accelerate the nitrogen conversion and removal in SBR. 相似文献
With the continual increase in the utilization of rare earth elements (REEs) for industrial and agricultural purposes in China,
the research into the environmental biogeochemical behavior of REEs has become a pressing issue. The REEs’ content in soil
and various parts of wheat under different conditions in soil–plant systems were measured by INAA and ICP-MS. The results
showed four aspects. (1) The mean value of total REEs in soil of China was 176.8 mg kg−1. The mean ratio of ΣLREE/ΣHREE in soils was 8.0 and cerium accounts for 42% of the total REEs. The content of REEs in wheat
seed ranged between 10−11 and 10−8 g g−1, 3–4 orders of magnitude lower than that in soil. (2) The REEs contents in ryegrass, especially in roots, were significantly
related to that of soil. The bioavailability of REEs in soil mainly depended on the exchangeable fraction of REEs, which was
strongly affected by the physico–chemical properties of the soil. (3) Long-term foliage-dressing with Changle microfertilizer
of REEs did not affect the contents and distribution patterns of REEs in soil. At the maturing stage of spring wheat, the
REEs content was in the order of root > leaf >stem and crust. Compared with the control, foliage-dressing has a higher accumulation
of REEs in root and leaf. However, no significant difference was found in stem and crust between the two treatments. (4) There
was no significant accumulation with the soil-dressing method. When comparing controls in both foliage- and soil-dressing
methods, no distinct residue of REEs in grains was found. 相似文献
Leaching behavior and gastrointestinal bioaccessibility of rare earth elements (REEs) from hospital waste incineration (HWI) fly and bottom ash samples collected from Beijing and Nanjing Cities were assessed. In the same ash sample, the leaching concentrations of individual REEs determined by the Toxicity Characteristic Leaching Procedure (TCLP) were higher than those detected by the European standard protocol (EN-type test), thereby suggesting that the low pH value of leaching solution was an important factor influencing the leachability of REE. The REE bioaccessibility results, which were evaluated using the physiologically based extraction test (PBET), indicated that REEs were highly absorbed during gastric phase by dissolution; and subsequently precipitated and/or re-adsorbed in small intestinal phase. The relative amounts of the total REEs extracted by the TCLP method, EN-type test and PBET test were compared. In addition to the pH value of extraction solutions, the chelating role of REEs with organic ligands used in the PBET method was also an important parameter affecting REE adsorption in human body. Additionally, this study showed that REEs were extracted by these methods as concomitants of heavy metals and anions (NO3–, F–, SO42–, and Cl–) from HWI ash, which probably caused the remarkably complex toxicity on human body by the exposure pathway.
The objective of this study was to assess the bulk chemical composition as well as the extent and severity of heavy metal
contamination in the paddy soil of Kočani Field (eastern Macedonia). The results revealed that the paddy soil of the western
part of Kočani Field is severely contaminated with Pb, Zn, As and Cd in the vicinity of the Zletovska River due to irrigation
with riverine water that is severely affected by acid mine and tailing effluents from the Pb–Zn mine in Zletovo. The detected
total concentrations of these metals are far above the threshold values considered to be phytotoxically excessive for surface
soil. The paddy soil in the vicinity of the Zletovska River was also found to exhibit elevated levels of Ba, Th, U, V, W,
Mo, Cu, Sb, Bi, Ag, Au, Hg and Tl, with concentrations above their generally accepted median concentration values obtained
during this study. A correlation matrix revealed that the Mn and Fe oxides/hydroxides are the most important carrier phase
for several trace elements, with the exception of rare earth elements (REEs). These also represent a major sink for the observed
heavy metal pollution of the soil. REEs are mostly associated with two phases: light (L)REEs are bound to K-Al, while heavy
(H)REEs are bound to Mg-bearing minerals. Although there is no direct evidence of a health risk, the paddy soil in the vicinity
of Zletovska River needs further investigation and an assessment should be made of its suitability for agricultural use, particularly
in view of the highly elevated concentrations of Pb, Zn, As and Cd. 相似文献
This paper analyses the contents and species distributions of rare earth elements (REEs) in the water-suspended particulate-sediment
system of the Baotou section of the Yellow River, China, with known anthropogenic REE input from industrial discharges. The
major forms of REEs were suspended and dissolved in the mainstream and the tributaries of the Baotou section, respectively.
The concentrations of the dissolved and suspended REEs had the same trends in the overlying water along the mainstream, which
increased from the Seqi section (site A) to the mouth of the Sidaosha River (site D), reaching a maximum value at site D,
and tending to decrease thereafter. The contents of REEs in sediment cores showed enrichment with light rare earth elements
(LREEs). The bound to carbonates and to Fe–Mn oxides are the major forms of REE in the secondary phase and the REE exhibited
LREE enrichment pattern and moderate Eu depletion in suspended particulates and surface sediments. The contents and species
distributions of REEs in the water-suspended particulate-sediment system of the Baotou section suggest that the anthropogenic
source of REEs from Baotou city have enhanced REE accumulation to the Baotou section. This information is important for predicting
possible pollution resulting from anthropogenic REE input into rivers. 相似文献