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671.
Sawalha MF Peralta-Videa JR Sanchez-Salcido B Gardea-Torresdey JL 《Journal of environmental management》2009,90(2):1213-1218
Batch studies were performed to determine the interference of calcium (Ca) and magnesium (Mg) on the sorption of Cu(II), Cd(II), Cr(III), Cr(VI), Pb(II), and Zn(II) [from CuSO(4), K(2)Cr(2)O(7), Pb(NO(3))(2), Cr(NO(3))(3), ZnCl(2), and Cd(NO(3))(2)] by saltbush (Atriplex canescens) biomass. The results demonstrated that Ca and Mg at concentrations of at least 20 times higher than the concentration of most of the target metals did not interfere with the metal binding. The data show that the batch binding capacity from a multimetal solution at pH 5.0 was (micromol/g) about 260 for Cr(III) and Pb, and about 117, 54, and 49 for Cu, Zn, and Cd, respectively. The use of 0.1M HCl allowed the recovery of 85-100% of the bound Cu, Cr(III), and Pb, and more than 37% of the bound Cd and Zn. The column binding capacity for Pb was about 49 micromol/g from both the single and multimetal solutions, while it was, respectively about 35 and 23 micromol/g for Cr(III). The binding capacity for Cu and Zn from the single and multimetal column experiments was 35 micromol/g and less than 10 micromol/g, respectively. The stripping data from the single column experiment showed that 0.1M HCl allowed the recovery of all the bound Cu and Zn, 90% and 74% of the bound Pb and Cr(VI), respectively, and less than 25% of the bound Cd and Cr(III), while the stripping from the multimetal experiment showed that 0.1M HCl allowed the recovery of all the bound Cu and about 74%, 54%, 43%, and 40% of the bound Pb, Zn, Cd, and Cr(III), respectively. 相似文献
672.
Su J Wang H Kimberley MO Beecroft K Magesan GN Hu C 《Environmental science and pollution research international》2007,14(7):529-535
Goal, Scope and Background Biosolids, i.e., treated sewage sludge, are commonly used as a fertilizer and amendment to improve soil productivity. Application
of biosolids to meet the nitrogen (N) requirements of crops can lead to accumulation of phosphorus (P) in soils, which may
result in P loss to water bodies. Since 1996, biosolids have been applied to a Pinus radiata D. Don plantation near Nelson City, New Zealand, in an N-deficient sandy soil. To investigate sustainability of the biosolids
application programme, a long-term research trial was established in 1997, and biosolids were applied every three years, at
three application rates, including control (no biosolids), standard and high treatments, based on total N loading. The objective
of this study was to evaluate the effect of repeated application of biosolids on P mobility in the sandy soil.
Materials and Methods Soil samples were collected in August 2004 from the trial site at depths of 0–10, 10–25, 25–50, 50–75, and 75–100 cm. The
soil samples were analysed for total P (TP), plant-available P (Olsen P and Mehlich 3 P), and various P fractions (water-soluble,
bioavailable, Fe and Al-bound, Ca-bound, and residual) using a sequential P fractionation procedure.
Results and Discussion Soil TP and Olsen P in the high biosolids treatment (equivalent to 600 kg N ha−1 applied every three years) had increased significantly (P<0.05) in both 0–10 cm and 10–25 cm layers. Mehlich 3 P in soil of the high treatment had increased significantly only at
0–10 cm. Olsen P appeared to be more sensitive than Mehlich 3 P as an indicator of P movement in a soil profile. Phosphorus
fractionation revealed that inorganic P (Al/Fe-bound P and Ca-bound P) and residual P were the main P pools in soil, whereas
water-soluble P accounted for approximately 70% of TP in biosolids. Little organic P was found in either the soil or biosolids.
Concentrations of water-soluble P, bioavailable inorganic P (NaHCO3 Pi) and potentially bioavailable inorganic P (NaOH Pi) in both 0–10 and 10–25 cm depths were significantly higher in the
high biosolids treatment than in the control. Mass balance calculation indicated that most P applied with biosolids was retained
by the top soil (0–25 cm). The standard biosolids treatment (equivalent to 300 kg N ha−1 applied every three years) had no significant effect on concentrations of TP, Mehlich 3 P and Olsen P, and P fractions in
soil.
Conclusions The results indicate that the soil had the capacity to retain most biosolids-derived P, and there was a minimal risk of P
losses via leaching in the medium term in the sandy forest soil because of the repeated biosolids application, particularly
at the standard rate.
Recommendations and Perspectives Application to low-fertility forest land can be used as an environmentally friendly option for biosolids management. When
biosolids are applied at a rate to meet the N requirement of the tree crop, it can take a very long time before the forest
soil is saturated with P. However, when a biosolids product contains high concentrations of P and is applied at a high rate,
the forest ecosystem may not have the capacity to retain all P applied with biosolids in the long term.
ESS-Submission Editor: Dr. Jean-Paul Schwitzguébel jean-paul.schwitzguebel@epfl.ch 相似文献
673.
Sakan S Grzetić I Dordević D 《Environmental science and pollution research international》2007,14(4):229-236
Introduction In this work, sediments of the River Tisa (Tisza) are studied to assess their environmental pollution levels for some major
heavy metals, as well as to predict the investigated elements’ mobility on the basis of their association type with the substrate.
The Tisa River catchments area is a subbasin of the River Danube. Part of this river, 166 km long, belongs to the Serbian
province of Vojvodina, before it flows into the Danube. It has been chosen for our investigation, because it has been exposed
to intense pollution in the last decades.
Materials and Methods The river sediment samples were collected at 32 locations. The proportions of sand, silt and clay fractions were determined.
The sequential extraction procedure following a modified Tessier method was applied for speciation of the metal forms in the
collected samples. The metal concentrations of Zn, Cd, Pb, Ni, Cu, Cr, Fe and Mn in extracts were determined by atomic absorption
spectroscopy.
Results and Discussion Granulometric analysis showed that some 50% of the Tisa River sediments were silt and clay, while the rest was sand with quartz,
as the main constituent. The average metal content of the surface river sediment samples for every fraction of sequential
extraction was presented and discussed in relation to pH, Eh and metal fractionation. The average metal content from the Tisa
River sediments, obtained as an average of the metal’s concentration released in all five sequential extraction fractions
was compared with: average metal contents of the Tisa River sediments in Hungary, metal content in soils formed on the Tisa
River alluvium of Vojvodina, average metal content in soils of Vojvodina, and average metal content in soils of Hungary. An
assessment of metal pollution levels in Tisa River sediments was made by comparing mean values for obtained results for the
Tisa River sediments with the freshwater sediment’s Quality Guidelines as published by US EPA, Environment Canada and soil
standards for Serbia.
Conclusion According to US EPA and Canadian Quality Guidelines for freshwater sediments, the concentration of heavy metals in Tisa sediments
were: (a) much higher than defined concentrations below which harmful effects on river biota are unlikely to be observed,
(b) below defined concentrations above which harmful effects on river biota are likely to be observed. The concentration levels
of Pb, Ni, Cu and Cr in Tisa River sediments are safe when compared with Serbian MAQ (Maximum Allowed Quantity) standards
for soils, but they are unsafe in the case of Zn and Cd.
Recommendations and Outlook The quality of sediments in the Tisa River was on the border line between potentially polluted and polluted. This line could
very easily be exceeded since the quality of sediments in the Tisa River in Hungary was already worse than in Serbia. These
results indicated the need for further monitoring of heavy metals in that locality. 相似文献
674.
The Yellow River in winter as source water is characterized as high alkalinity, low temperature and low particle concentrations,
which have brought many difficulties to water treatment plants. This study fully examines the optimized coagulation process
of the Yellow River by conventional and pre-polymerized metal coagulants, pH adjustment and polyelectrolytes as the primary
coagulants or coagulant aids. For all the metal coagulants, polyaluminum chlorides are superior to traditional metal coagulants
due to their stable polymeric species and low consumption of alkalinity. The removal of natural organic matter by monomeric
metal coagulants can be improved through pH adjustment, which is in accordance with the higher concentration of polymeric
species formed at corresponding pH value. With the addition of polyelectrolytes as coagulant aids, the coagulation performance
is significantly improved. The effective removal of dissolved organic matter is consistent with high charge density, while
molecular weight is relatively important for removing particles, which is consistent with polyelectrolytes as primary coagulants.
These results suggest that the coagulation mechanisms in the removal of dissolved organic matter and particles are different,
which may be exploited for optimized coagulation for the typical source water in practice. 相似文献
675.
Carboxymethyl-beta-cyclodextrin (CMCD) has been proposed for remediation of metal-contaminated sediments. This research presents stability constants for CMCD-lead complexes, and demonstrates a rigorous methodology for estimating stability constants for metal-complexing agents. The conditional stability constant for the lead-CMCD aqueous complex was determined to be 10(5.18) with the 95% confidence interval ranging from 10(5.14) to 10(5.22). The best fit for experimental data was made by assuming a reaction between divalent CMCD(2-) and Pb(2+) and using the WATEQ activity coefficient formulation. The optimized value was derived from experimental data with the geochemical model PHREEQC coupled to UCODE_2005, a parameter optimization program. Like FITEQL, UCODE has a built-in option to optimize parameter values by minimizing the weighted sum of squared residuals (WSSR). However, our approach not only allows rapid, automatic optimization of the stability constant, but also allows determination of uncertainties in estimated parameter values and statistical analysis to assess the appropriateness of the conceptual model. The automation of the process allows testing of multiple conceptual models and the final values produced are internally consistent with the PHREEQC database. In this case five different conceptual models to describe the metal complexation and protonation reactions of CMCD were considered. 相似文献
676.
Mining activities in Rakha copper mine (Jharkhand, India) were ceased in the year 2001, leaving a huge amount of untreated
tailings in the nearby tailings pond. The copper tailings contained high concentrations of heavy metals (total Cu, Ni concentrations
1779, 564 mgkg−1, respectively), and low contents of major nutrient elements and organic matter. Tailings are often very unstable, and a potential
vegetation cover may reduce the erosion or immobilize the toxicants to surrounding environment by phytostabilization. However,
high shoot concentrations of elements might disperse them and could be harmful to grazing animals. The objective of this study
was to find out which of the three properties; low-accumulation, root accumulation or shoot accumulation of elements (Cu,
Ni, Mn, Zn, Pb, Cd and Co), occur in the semi aquatic species Ammania baccifera growing on copper tailings. Roots of this species accumulated high levels of Cu, even more than 1000 mg kg−1, DW. Metals accumulated by A. baccifera were mostly distributed in root tissues, suggesting that an exclusion strategy for metal tolerance widely exists in them.
Thus, establishment of such plant on copper tailings can be a safe method to stabilize the metals. 相似文献
677.
Knowledge of the total concentration of heavy metals is not enough to fully assess the environmental impact of urban soils.
For this reason, the determination of metal speciation is important to evaluate their environment and the mobilization capacity.
Sequential extraction technique proposed by the former European Community Bureau of Reference (BCR) was used to speciate Cd,
Cu, Fe, Mn, Ni, Pb, and Zn in urban soils from Guangzhou into four operationally defined fractions: HOAc extractable, reducible,
oxidizable, and residual. The Cu, Fe, Ni, and Zn were predominately located in the residual fraction, Pb in the reducible
fraction, and Cd and Mn within the HOAc extractable fraction. The order of Cd in each fraction was generally HOAc extractable
> reducible > residual > oxidizable; Cu and Fe were residual > reducible > oxidizable > HOAc extractable; Mn was HOAc extractable
> residual > reducible > oxidizable; Ni and Zn were residual > reducible > HOAc extractable > oxidizable; and Pb was reducible
> residual > oxidizable > HOAc extractable. Cadmium was identified as being the most mobile of the elements, followed by Mn,
Zn, Ni, Cu, Pb and Fe. Iron–Mn oxides can play an important role in binding Cd, Cu, Ni, Pb, and Zn and in decreasing their
proportion associated with the residual fraction in the soils. With total concentrations of Cd, Cu, Ni, Pb, Zn, and Mn increase,
these metals more easily release and may produce more negative effects on the urban environment. 相似文献
678.
Unravelling the effects of complexation of transition metal ions on the hydroxylation of catechol over the whole pH region
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Zexiu An Jianfei Sun Qiong Mei Bo Wei Mingxue Li Ju Xie Maoxia He Qiao Wang 《环境科学学报(英文版)》2022,34(5):392-402
Catechol pollutants (CATPs) serving as chelating agents could coordinate with many metal ions to form various CATPs-metal complexes. Little information is available on the effects of complexation of metal ions on CATPs degradation. This work presents a systematical study of •OH-mediated degradation of catechol and catechol-metal complexes over the whole pH range in advanced oxidation processes (AOPs). Results show that the pH-dependent complexation of metal ions (Zn2+, Cu2+, Ti4+ and Fe3+) promotes the deprotonation of catechol under neutral and even acidic conditions. The radical adduct formation (RAF) reactions are both thermodynamically and kinetically favorable for all dissociation and complexation species, and OH/O− group-containing C positions are more vulnerable to •OH attack. The kinetic results show that the complexation of the four metal ions offers a wide pH range of effectiveness for catechol degradation. At pH 7, the apparent rate constant (kapp) values for different systems follow the order of catechol+Ti4+ ≈ catechol+Zn2+ > catechol+Cu2+ > catechol+Fe3+ > catechol. The mechanistic and kinetic results would greatly improve our understanding of the degradation of CATPs-metal and other organics-metal complexes in AOPs. The toxicity assessment indicates that the •OH-based AOPs have the ability for decreasing the toxicity and increasing the biodegradability during the processes of catechol degradation. 相似文献