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41.
Phosphates for Pb immobilization in soils: a review 总被引:9,自引:0,他引:9
In its soluble ionic forms, lead (Pb) is a toxic element occurring in waters and soils mainly as the result of human activities.
The bioavailability of lead ions can be decreased by complexation with various materials in order to decrease their toxicity.
Pb chemical immobilization using phosphate addition is a widely accepted technique to immobilize Pb from aqueous solution
and contaminated soils. The application of different P amendments cause Pb in soils to shift from forms with high availability
to the most strongly bound Pb fractions. The increase of Pb in the residual or insoluble fraction results from formation of
pyromorphite Pb5(PO4)3X where X = F, Cl, Br, OH, the most stable environmental Pb compounds under a wide range of pH and Eh natural conditions.
Accidental pyromorphite ingestion does not yield bioavailable lead, because pyromorphite is insoluble in the intestinal tract.
Numerous natural and synthetic phosphates materials have been used to immobilize Pb: apatite and hydroxyapatite, biological
apatite, rock phosphate, soluble phosphate fertilizers such as monoammonium phosphate, diammonium phosphate, phosphoric acid,
biosolids rich in P, phosphatic clay and mixtures. The identification of pyromorphite in phosphate amended soils has been
carried out by different non destructive techniques such as X-ray diffraction, scanning electron microscopy coupled with energy
dispersive X-ray spectroscopy, X-ray absorption fine structure, transmission electron microscopy and electron microprobe analysis.
The effectiveness of in situ Pb immobilization has also been evaluated by selective sequential extraction, by the toxicity
leaching procedure and by a physiologically based extraction procedure simulating metal ingestion and gastrointestinal bioavailability
to humans. Efficient Pb immobilization using P amendments requires increasing the solubility of the phosphate phase and of
the Pb species phase by inducing acid conditions. Although phosphorus addition seems to be highly effective, excess P in soil
and its potential effect on eutrophication of surface water, and the possibility of As enhanced leaching remains a concern.
The use of mixed treatments may be a useful strategy to improve their effectiveness in reducing lead phyto- and bioavailability. 相似文献
42.
Variations between rice cultivars in root secretion of organic acids and the relationship with plant cadmium uptake 总被引:13,自引:0,他引:13
To attempt to understand certain mechanisms causing the variations between rice cultivars with regard to Cd uptake and accumulation,
pot soil experiments were conducted with two rice cultivars at different levels of Cd, i.e., 0 (the control), 10, 50 mg Cd
kg−1 soil. The two rice cultivars differ significantly with regard to Cd uptake and accumulation. Root secretions of low-molecular-weight
organic acids (LMWOA) for each treatment were measured with ion chromatography. The results showed that LMWOA concentrations
in the soil planted with Shan you 63 (a high soil Cd accumulator) were all higher than those in the soil planted with Wu yun jing 7 (low soil Cd accumulator) at different soil Cd levels, although the magnitudes of the differences varied for individual LMWOA
and depend on soil Cd concentrations. For all six LMWOA, there were significant differences at P < 0.05 or < 0.01 levels for soils treated with 10 and 50 mg kg−1 Cd. The magnitude of the differences was greater under soil Cd treatments, especially at relatively low levels (for example,
10 mg Cd kg−1 soil), than in the control. Acetic acid and formic acid constituted more than 96% of the total concentration of the six LMWOA,
while citric acid constituted only about 0.1%. The rice cultivar with higher concentrations of LMWOA in soil accumulated more
Cd in the plants. The results indicate that LMWOA secretion by rice root, especially in Cd-contaminated soils, is likely to
be one of the mechanisms determining the plant Cd uptake properties of rice cultivars. 相似文献
43.
A review of the distribution of particulate trace elements in urban terrestrial environments and its application to considerations of risk 总被引:6,自引:0,他引:6
We review the evolution, state of the art and future lines of research on the sources, transport pathways, and sinks of particulate
trace elements in urban terrestrial environments to include the atmosphere, soils, and street and indoor dusts. Such studies
reveal reductions in the emissions of some elements of historical concern such as Pb, with interest consequently focusing
on other toxic trace elements such as As, Cd, Hg, Zn, and Cu. While establishment of levels of these elements is important
in assessing the potential impacts of human society on the urban environment, it is also necessary to apply this knowledge
in conjunction with information on the toxicity of those trace elements and the degree of exposure of human receptors to an
assessment of whether such contamination represents a real risk to the city’s inhabitants and therefore how this risk can
be addressed. 相似文献
44.
We present a new system for microscopic multicolour variable chlorophyll fluorescence imaging of aquatic phototrophs. The
system is compact and portable and enables microscopic imaging of photosynthetic performance of individual cells and chloroplasts
using different combinations of blue, green, red or white light. Automated sequential exposure of microscopic samples to the
three excitation colours enables subsequent deconvolution of the resulting fluorescence signals and colour marking of cells
with different photopigmentation, i.e., cyanobacteria, green algae, red algae and diatoms. The photosynthetic activity in
complex mixtures of phototrophs and natural samples can thus be assigned to different types of phototrophs, which can be quantified
simultaneously. Here, we describe the composition and performance of the new imaging system and present applications with
both natural phytoplankton and microalgal culture samples. 相似文献
45.
Photo-polymerization of triclosan in aqueous solution induced by ultraviolet radiation 总被引:1,自引:0,他引:1
The formation of 2,8-dichlorodibenzo-p-dioxin and other harmful degradation products in the photo-degradation process of triclosan is of increasing concern. Here we worked on the identification of polymerized products at high triclosan concentration and on the mechanism of photoreaction. Five dimmers and two trimers of triclosan were detected by liquid chromatography-mass spectrum analysis. 2,8-dichlorodibenzo-p-dioxin was also identified by comparing with an authentic standard. Relatively low pH and high concentration favored the polymerization of triclosan. Three main routes of photoreaction were postulated, namely dechlorination, ring closure and polymerization. 相似文献
46.
Aijun Yao Yani Wang Xiaodan Ling Zhe Chen Yetao Tang Hao Qiu Rongrong Ying Rongliang Qiu 《Environmental geochemistry and health》2017,39(2):353-367
Economic and highly effective methods of in situ remediation of Cd and As polluted farmland in mining areas are urgently needed. Pot experiments with Brassica chinensis L. were carried out to determine the effects of three soil amendments [a novel iron-silicon material (ISM), a synthetic zeolite (SZ) and an alkaline clay (AC)] on vegetable uptake of As and Cd. SEM–EDS and XRD analyses were used to investigate the remediation mechanisms involved. Amendment with ISM significantly reduced the concentrations of As and Cd in edible parts of B. chinensis (by 84–94 % and 38–87 %, respectively), to levels that met food safety regulations and was much lower than those achieved by SZ and AC. ISM also significantly increased fresh biomass by 169–1412 % and 436–731 % in two consecutive growing seasons, while SZ and AC did not significantly affect vegetable growth. Correlation analysis suggested that it was the mitigating effects of ISM on soil acidity and on As and Cd toxicity, rather than nutrient amelioration, that contributed to the improvement in plant growth. SEM–EDS analysis showed that ISM contained far more Ca, Fe and Mn than did SZ or AC, and XRD analysis showed that in the ISM these elements were primarily in the form of silicates, oxides and phosphates that had high capacities for chemisorption of metal(loid)s. After incubation with solutions containing 800 mg L?1 AsO4 2? or Cd2+, ISM bound distinctly higher levels of As (6.18 % in relative mass percent by EDS analysis) and Cd (7.21 % in relative mass percent by EDS analysis) compared to SZ and AC. XRD analysis also showed that ISM facilitated the precipitation of Cd2+ as silicates, phosphates and hydroxides, and that arsenate combined with Fe, Al, Ca and Mg to form insoluble arsenate compounds. These precipitation mechanisms were much more active in ISM than in SZ or AC. Due to the greater pH elevation caused by the abundant calcium silicate, chemisorption and precipitation mechanisms in ISM treatments could be further enhanced. That heavy metal(loid)s fixation mechanisms of ISM ensure the remediation more irreversible and more resilient to environmental changes. With appropriate application rate and proper nutrients supplement, the readily available and economic ISM is a very promising amendment for safe crop production on multi-metal(loids) polluted soils. 相似文献
47.
Environmental exposure to arsenic (As) in terms of public health is receiving increasing attention worldwide following cases of mass contamination in different parts of the world. However, there is a scarcity of data available on As geochemistry in Brazilian territory, despite the known occurrence of As in some of the more severely polluted areas of Brazil. The purpose of this paper is to discuss existing data on As distribution in Brazil based on recent investigations in three contaminated areas as well as results from the literature. To date, integrated studies on environmental and anthropogenic sources of As contamination have been carried out only in three areas in Brazil: (1) the Southeastern region, known as the Iron Quadrangle, where As was released into the drainage systems, soils and atmosphere as a result of gold mining; (2) the Ribeira Valley, where As occurs in Pb-Zn mine wastes and naturally in As-rich rocks and soils; (3) the Amazon region, including the Santana area, where As is associated with manganese ores mined over the last 50 years. Toxicological studies revealed that the populations were not exposed to elevated levels of As, with the As concentrations in surface water in these areas rarely exceeding 10 microg/L. Deep weathering of bedrocks along with formation of Fe/Al-enriched soils and sediments function as a chemical barrier that prevents the release of As into the water. In addition, the tropical climate results in high rates of precipitation in the northern and southeastern regions and, hence, the As contents of drinking water is diluted. Severe cases of human As exposure related to non-point pollution sources have not been reported in Brazil. However, increasing awareness of the adverse health effects of As will eventually lead to a more complete picture of the distribution of As in Brazil. 相似文献
48.
49.
Haber W 《Environmental science and pollution research international》2007,14(6):359-365
Humans’ superiority over all other organisms on earth rests on five main foundations: command of fire requiring fuel; controlled
production of food and other biotic substances; utilization of metals and other non-living materials for construction and
appliances; technically determined, urban-oriented living standard; economically and culturally regulated societal organization.
The young discipline of ecology has revealed that the progress of civilization and technology attained, and being further
pursued by humankind, and generally taken for granted and permanent, is leading into ecological traps. This metaphor circumscribes
ecological situations where finite resources are being exhausted or rendered non-utilizable without a realistic prospect of
restitution. Energy, food and land are the principal, closely interrelated traps; but the absolutely decisive resource in
question is land whose increasing scarcity is totally underrated. Land is needed for fulfilling growing food demands, for
producing renewable energy in the post-fossil and post-nuclear era, for maintaining other ecosystem services, for urban-industrial
uses, transport, material extraction, refuse deposition, but also for leisure, recreation, and nature conservation. All these
needs compete for land, food and non-food biomass production moreover for good soils that are scarcer than ever. We are preoccupied
with fighting climate change and loss of biodiversity; but these are minor problems we could adapt to, albeit painfully, and
their solution will fail if we are caught in the interrelated traps of energy, food, and land scarcity. Land and soils, finite
and irreproducible resources, are the key issues we have to devote our work to, based on careful ecological information, planning
and design for proper uses and purposes. The article concludes with a short reflection on economy and competition as general
driving forces, and on the role and reputation of today’s ecology.
Updated version of the keynote lecture presented at the EcoSummit 2007 in Beijing, China, May 24. The article is gratefully
dedicated to the memory of my late colleague and friend Frank B. Golley. 相似文献
50.
Carolina Oliveira de Santana Taíse Bomfim de Jesus William Moura de Aguiar Washington de Jesus Sant’anna Franca-Rocha Carlos Alberto Caroso Soares 《Environmental monitoring and assessment》2017,189(3):123
In this study, an analysis was performed on the concentrations of the trace elements Al, As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V, and Zn in muscle of two carnivorous and one planktivorous fish species collected at Todos os Santos Bay (BTS). The accumulation order of the trace elements in Lutjanus analis was Al >Zn >Fe >Cr >Ba >Ni. In Cetengraulis edentulus, the order was Al >Fe >Zn >Cr >Ni >Mn >As. In the species Diapterus rhombeus, the order was Al >Fe >Zn >Cr >Ni >Mn >Cd. To determine the risk related to the consumption of fish, toxicity guidelines were used as standard references. It was observed that the species C. edentulus contained concentrations of As exceeding WHO limits, but these concentrations were acceptable according to the Agência Nacional de Vigilância Sanitária (ANVISA) guidelines. Cd levels were found only in D. rhombeus and in low concentrations according to the determinations of WHO and ANVISA. Pb levels were not detected in any of the three fish species. The analyzed elements did not differ statistically according to the species and feeding habits. The results point to possible risks of human contamination by As related to the consumption of the fish species C. edentulus from the BTS. 相似文献