Phytotoxicity and antioxidative enzymes of green microalga (Desmodesmus subspicatus) and duckweed (Lemna minor) exposed to herbicides MCPA, chloridazon and their mixtures

In this study, we evaluate the toxicity of MCPA (auxin-like growth inhibitor), chloridazon (CHD) (PSII-inhibitor) and their mixtures to floating plants and planktonic algae. Toxicity of MCPA (4-chloro-2-methylphenoxyacetic acid) and CHD (5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone) was first assessed in two growth inhibition tests with Lemna minor (ISO/DIS 20079) and Desmodesmus subspicatus (ISO 8692). Next, herbicide mixtures at concentrations corresponding to the EC values were used to assess their interactive effects, and the biomarkers were: for duckweed fresh weight, frond area, chlorophyll content and number of fronds, and for algae cell count and cell volume. The 3d EC?? and EC?? values using cell counts of D. subspicatus were 142.7 and 529.1 mg/L for MCPA and 1.7 and 5.1 mg/L for CHD. The 7d EC?? and EC?? values using frond number of L. minor amounted to 0.8 and 5.4 mg/L for MCPA and 0.7 and 10.4 mg/L for CHD. Higher sensitivity of reproductive (number of cells/fronds) than growth processes (cell volume/frond area) to herbicides applied individually and in mixtures was especially pronounced in the responses of Desmodesmus. Herbicide interactions were assessed by the two-way ANOVA and Abbott's formula. Generally, an antagonistic interaction with Lemna was revealed by MCPA and chloridazon, whereas additive effect of both herbicides was observed for Desmodesmus. A significant stimulation of SOD and APX activity by binary mixtures was noted in algal cells mainly after 24 and 48 hours of exposure. The extremely high stimulation of the activity of both enzymes was induced by the combination EC??CHD + EC??MCPA (48 h). Presumably due to oxidative stress, the treatment with CHD at concentration EC?? after 72 h was lethal for algae grown in aerated cultures, in contrast to standardized test conditions. Taking into account the consequences of risk assessment for herbicide mixtures we can state that a relatively low toxicity, as well as the lack of significant synergy between MCPA and CHD to non-target plants appears to be the most important result.     

Effects of arsenic on concentration and distribution of nutrients in the fronds of the arsenic hyperaccumulator Pteris vittata L

Pteris vittata was the first terrestrial plant known to hyperaccumulate arsenic (As). However, it is unclear how As hyperaccumulation influences nutrient uptake by this plant. P. vittata fern was grown in soil spiked with 0-500 mg As kg(-1) in the greenhouse for 24 weeks. The concentrations of essential macro- (P, K, Ca, and Mg) and micro- (Fe, Mn, Cu, Zn, B and Mo) elements in the fronds of different age were examined. Both macro- and micronutrients in the fronds were found to be within the normal concentration ranges for non-hyperaccumulators. However, As hyperaccumulation did influence the elemental distribution among fronds of different age of P. vittata. Arsenic-induced P and K enhancements in the fronds contributed to the As-induced growth stimulation at low As levels. The frond P/As molar ratios of 1.0 can be used as the threshold value for normal growth of P. vittata. Potassium may function as a counter-cation for As in the fronds as shown by the As-induced K increases in the fronds. The present findings not only demonstrate that P. vittata has the ability to maintain adequate concentrations of essential nutrients while hyperaccumulating As from the soil, but also have implications for soil management (fertilization in particular) of P. vittata in As phytoextraction practice.     

Phytotoxicity and antioxidative enzymes of green microalga (Desmodesmus subspicatus) and duckweed (Lemna minor) exposed to herbicides MCPA,chloridazon and their mixtures

In this study, we evaluate the toxicity of MCPA (auxin-like growth inhibitor), chloridazon (CHD) (PSII-inhibitor) and their mixtures to floating plants and planktonic algae. Toxicity of MCPA (4-chloro-2-methylphenoxyacetic acid) and CHD (5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone) was first assessed in two growth inhibition tests with Lemna minor (ISO/DIS 20079) and Desmodesmus subspicatus (ISO 8692). Next, herbicide mixtures at concentrations corresponding to the EC values were used to assess their interactive effects, and the biomarkers were: for duckweed fresh weight, frond area, chlorophyll content and number of fronds, and for algae cell count and cell volume. The 3d EC₁₀ and EC₅₀ values using cell counts of D. subspicatus were 142.7 and 529.1 mg/L for MCPA and 1.7 and 5.1 mg/L for CHD. The 7d EC₁₀ and EC₅₀ values using frond number of L. minor amounted to 0.8 and 5.4 mg/L for MCPA and 0.7 and 10.4 mg/L for CHD. Higher sensitivity of reproductive (number of cells/fronds) than growth processes (cell volume/frond area) to herbicides applied individually and in mixtures was especially pronounced in the responses of Desmodesmus. Herbicide interactions were assessed by the two-way ANOVA and Abbott's formula. Generally, an antagonistic interaction with Lemna was revealed by MCPA and chloridazon, whereas additive effect of both herbicides was observed for Desmodesmus. A significant stimulation of SOD and APX activity by binary mixtures was noted in algal cells mainly after 24 and 48 hours of exposure. The extremely high stimulation of the activity of both enzymes was induced by the combination EC₁₀CHD + EC₅₀MCPA (48 h). Presumably due to oxidative stress, the treatment with CHD at concentration EC₅₀ after 72h was lethal for algae grown in aerated cultures, in contrast to standardized test conditions. Taking into account the consequences of risk assessment for herbicide mixtures we can state that a relatively low toxicity, as well as the lack of significant synergy between MCPA and CHD to non-target plants appears to be the most important result.     

Phytotoxicity of coloured substances: is Lemna duckweed an alternative to the algal growth inhibition test?

Coloured substances cause problems when interpreting algal tests, because effects due to light absorption can interact with potential toxicity. The Lemna Duckweed growth inhibition test can complement the algal test, on condition that the test is performed on a black, not reflecting surface. On white surfaces, test solution colour can strongly impact Lemna growth. For example, average control sample growth rate of is much higher on white surfaces (0.362 d(-1)) than on black surfaces (0.284 d(-1)). We found that 10 mg l(-1) of the dyestuff "Brilliant Blue R spezial" inhibited average Lemna growth rate about 22% on white surfaces but did not inhibit growth on black surfaces. The reason for this difference stems from the difference in amount of light reflected from below the test beakers. With Brilliant Blue on white surfaces, the test solution colour reduces utilizable light and causes a deterioration of light conditions, whereas on a black surfaces, reflected light is absent a priori, and thus no inhibiting effect was measured. Of particular importance is the choice of test parameter. With Brilliant Blue, a LOEC for average growth rate, based on frond numbers, of 320 mg l(-1) was determined. However, when average growth rate was calculated using dry weights of the plants, the LOEC decreased clearly to 1.0 mg l(-1). In this study, the Lemna test was much more sensitive than the algal test. We recommend Lemna tests be used in addition to algal tests, because doing so may significantly improve the assessment of phytotoxicity of chemicals and sewage.     

The effect of thallium on the growth of Lemna minor and plant tissue concentrations in relation to both exposure and toxicity

The effect of thallium on frond production and the rates of increase in surface area and fresh weight in Lemna minor were examined in terms of concentrations of the element in the growth medium and in the plant. The toxicity indices, EC(50) and threshold concentration, indicate that curtailment of frond expansion occurs at a lower thallium exposure than inhibition of frond multiplication. Production of smaller fronds, rather than chlorosis, was the most notable initial response to thallium stress and, below the threshold of toxicity, enhanced multiplication rates were recorded. Subsequent recovery in thallium-free medium was significant in the region of EC(50) exposures and below, but very little recovery occurred at higher exposures. Lemna minor has a remarkable capacity to accumulate thallium, and accumulation factors of 88 x 10(3) at low exposures, and 6 x 10(3) at high exposures, were recorded, which would suggest some form of active uptake.     

Kinetics of basic dye (methylene blue) biosorption by giant duckweed (Spirodela polyrrhiza)

Wastewater containing pigments and/or dyes can cause serious water pollution problems in the form of reduced light penetration and photosynthesis, and the toxicity from heavy metals associated with pigments and/or dyes. Laboratory investigations, of the potential use of dried Spirodela polyrrhiza biomass as an adsorbent for the removal of the basic dye methylene blue from aqueous solution were conducted. A series of experiments were undertaken in an agitated batch adsorber to assess the effect of the system variables, i.e. sorbent dosage, pH, and contact time. The results showed that as the amount of the dried S. polyrrhiza increased, the percentage of dye sorption increased accordingly. At pH 2.0 the sorption of dye was not favorable, while the sorption at other pHs (3.0-11.0) was remarkable. There was no significant difference in the dye concentration remaining when the pH was increased from 3.0 to 11.0. The dye removal time was influenced by the initial dye concentration, and the process followed the first-order rate kinetics. The rate constants for intraparticle diffusion were 1.00 and 3.27 mg/g/min1/2 for 300 and 500 mg/l of dye, respectively.     

Phytoextraction by arsenic hyperaccumulator Pteris vittata L. from six arsenic-contaminated soils: Repeated harvests and arsenic redistribution

This greenhouse experiment evaluated arsenic removal by Pteris vittata and its effects on arsenic redistribution in soils. P. vittata grew in six arsenic-contaminated soils and its fronds were harvested and analyzed for arsenic in October, 2003, April, 2004, and October, 2004. The soil arsenic was separated into five fractions via sequential extraction. The ferns grew well and took up arsenic from all soils. Fern biomass ranged from 24.8 to 33.5 g plant(-1) after 4 months of growth but was reduced in the subsequent harvests. The frond arsenic concentrations ranged from 66 to 6,151 mg kg(-1), 110 to 3,056 mg kg(-1), and 162 to 2,139 mg kg(-1) from the first, second and third harvest, respectively. P. vittata reduced soil arsenic by 6.4-13% after three harvests. Arsenic in the soils was primarily associated with amorphous hydrous oxides (40-59%), which contributed the most to arsenic taken up by P. vittata (45-72%). It is possible to use P. vittata to remediate arsenic-contaminated soils by repeatedly harvesting its fronds.     

Boron pollution due to geothermal wastewater discharge into the Buyuk Menderes river, Turkey

Kizildere, which is the only commercial geothermal power plant in Turkey and located in Buyuk Menderes Graben in south-west Turkey, discharges annually 6 million tonnes of wastewater into the Buyuk Menderes river, creating environmental pollution. Currently, the wastewater, which includes up to 24 mg/l boron, is discharged into the river at a rate of 750–1500 tonnes per hour. The temperature of the wastewater is approximately 1401°C. The water quality of Buyuk Menderes river is very important for the environment and aquatic life. Reinjection seems to be the only possible solution to this environmental problem.     

Removal of cyanide by woody plants

Hydrogen cyanide is a high volume production chemical that causes severe environmental problems. The toxicity of potassium cyanide (KCN) to basket willow trees (Salix viminalis) was tested. In aqueous solution, 2 mg CN l(-1) as KCN depressed the transpiration after 72 h about 50%. Trees exposed to 0.4 mg CN l(-1) in aqueous solution showed initially a depression of transpiration, but recovered. Doses of 8 and 20 mg CN l(-1) in aqueous solution were quickly mortal to the trees. At the end of the test, almost all cyanide had disappeared from the solutions. Levels of cyanide in plants were related to the toxicity, with no elevated levels of cyanide in plants exposed to 0.4 mg CN l(-1). Willows grown in sand survived 423.5 h irrigation with 20 mg CN l(-1). Willows grown in sand irrigated with 50 mg CN l(-1) died within a few days. The roots of the surviving willows were able to consume about 10 mg CN kg fresh weight(-1)h(-1). Vascular plants possess the enzymes beta-cyanoalanine synthase and beta-cyanoalanine hydrolase, which convert free cyanide to the amino acid asparagine. The in vivo capacity of woody plants (willow, poplar, elder, rose, birch) to remove cyanide was evaluated. Tests were performed with detached leaves and roots in KCN solutions of different concentrations. The highest removal capacity was obtained for basket willow hybrids (Salix viminalis x schwerinii). The Michaelis-Menten kinetics was determined. Realistic values of the half-saturation constant, K(M), were between 0.6 and 1.7 mg CN l(-1); the maximum metabolic capacity, v(max), was around 9.3 mg CN kg fresh weight(-1)h(-1). The removal of cyanide by plants might be useful in phytoremediation and treatment of wastewater from gold mining.     

Boron toxicity in the rare serpentine plant, Streptanthus morrisonii

The release of boron-laden mist from the cooling towers of some geothermal power stations in northern California potentially threatens nearby populations of the rare serpentine plant, Streptanthus morrisonii F. W. Hoffm. To assess the tolerance of S. morrisonii to high levels of boron, the effect of boron on leaf condition, life history, germination rate, growth rate, allocation and photosynthesis was measured on plants grown in a greenhouse. Relative to other species, S. morrisonii was tolerant of excess boron. On serpentine soil, mild to moderate toxicity symptoms (older leaves exhibiting chlorosis and necrosis, but few leaves killed) were apparent when the boron concentration in applied nutrient solutions was 240-650 microm. Severe toxicity symptoms (significant leaf loss, young leaves with toxicity symptoms) were apparent when the applied solution was over 1000 microm boron. Above 1000 microm boron, S. morrisonii appeared unable to complete its life cycle. On a tissue basis, boron toxicity was first observed when leaf boron content was 40-90 micromol g(-1) dry weight. In leaves with severe boron toxicity (> 35% injury), the boron content was generally above 130 micromol g(-1) dry weight. These levels were an order of magnitude above the tissue boron content of plants in the field. Prior to the onset of pronounced boron toxicity symptoms, growth rate, allocation patterns, and photosynthesis were unaffected by high boron. These results indicate that inhibition of growth and photosynthesis occurred because of a loss of viable tissue due to boron injury, rather than a progressive decline as leaf boron levels increased.     

浮萍植物在污水处理中的应用研究进展

浮萍科植物是漂浮生长在水流相对平缓的湖泊河湾水面上植物类群，整个植株完全退化为一个呈圆形或椭圆形的叶状体，主要是通过根或叶状体从水中吸收所需的氮磷等各种营养物质。浮萍科植物的氮磷含量和生长速率高并可以耐受多种污水条件，因此这个类群是污水处理生态工程中重要的水生植物类群。以浮萍为主的污水处理系统已得到较多的研究和应用，这类系统最大特点是浮萍的生长可以大量吸收污水中的氮磷，从而具有较高的氮磷去除率，同时生成的生物量可多种方式利用。因此利用这类系统对污水进行氮磷的处理与转化，并将生成的浮萍生物量适当地资源化利用是未来的发展方向。     

浮萍植物在污水处理中的应用研究进展

浮萍科植物是漂浮生长在水流相对平缓的湖泊河湾水面上植物类群,整个植株完全退化为一个呈圆形或椭圆形的叶状体,主要是通过根或叶状体从水中吸收所需的氮磷等各种营养物质.浮萍科植物的氮磷含量和生长速率高并可以耐受多种污水条件,因此这个类群是污水处理生态工程中重要的水生植物类群.以浮萍为主的污水处理系统已得到较多的研究和应用,这类系统最大特点是浮萍的生长可以大量吸收污水中的氮磷,从而具有较高的氮磷去除率,同时生成的生物量可多种方式利用.因此利用这类系统对污水进行氮磷的处理与转化,并将生成的浮萍生物量适当地资源化利用是未来的发展方向.     

Duckweed (Lemna gibba) growth inhibition bioassay for evaluating the toxicity of olive mill wastes before and during composting

Two-phase olive mill waste (TPOMW) is considered the main problem confronting the modern oil extraction and processing industry. Composting has been recently proposed as a suitable method to treat TPOMW so that it is suitable for use in agriculture. In the work reported here, the Lemna gibba bioassay was tested to assess the toxicity of TPOMW before and during the composting process. The method was compared with the Lepidium sativum bioassay and with other chemical maturity indices traditionally reported in the literature. The L. gibba test proved to be a simple, sensitive, and accurate method to evaluate toxicity before and during the composting of TPOMW. Plant growth response was measured by two methods: counting the number of fronds (leaves) and measuring total frond area (TFA) with image analysis software. Compared to the counting of fronds (L. gibba) or seeds (L. sativum), the use of area-measuring software permitted a very rapid, unbiased and easy way of analysing the toxicity of TPOMW before and during composting. Although the accuracy of the frond count method was similar to the traditional cress seed test, data analysis showed that the TFA measurement method was statistically more accurate (significantly lower variance) than the frond count approach. Highly significant correlations were found between TFA and some important maturation indices commonly reported in literature indicating that the L. gibba bioassay can be a useful tool to determine the degree of maturity of TPOMW composts.     

Phytoremediation potential of Spirulina (Arthrospira) platensis: biosorption and toxicity studies of cadmium

This study examines the possibility of using Spirulina (Arthrospira) platensis TISTR 8217 to remove low concentrations of cadmium (less than 100 mg/l) from wastewater. The cyanobacteria were exposed to six different cadmium concentrations for 96 h, and the growth rate was determined using an optical density at 560 nm. The inhibiting concentration (IC50) was estimated using probit analysis. The IC50 at 24, 48, 72, and 96 h were 13.15, 16.68, 17.28, and 18.35 mg/l Cd, respectively. Cellular damage was studied under a light microscope and a transmission electron microscope. Swollen cells and fragmented filaments were observed. Cell injury increased with increasing concentrations of cadmium. Ultrastructural changes were observed in the algae exposed to cadmium concentrations both close to IC50 (14.68 mg/l) and at IC50 (18.35 mg/l). The alterations induced by cadmium were disintegration and disorganization of thylakoid membranes, presence of large intrathylakoidal space, increase of polyphosphate bodies, and cell lysis. In addition, the cadmium adsorption by algal cells was studied. Environmental factors were found to have an effect on biosorption. The uptake of cadmium was not affected by the temperature of the solution, but the sorption was pH dependent. The optimum pH for biosorption of algal cells was 7. The cadmium uptake process was rapid, with 78% of metal sorption completed within 5 min. The sorption data fit well to the Langmuir isotherm. The maximum adsorption capacity for S. platensis was 98.04 mg Cd per g biomass.     

原核小球藻USTB-01去除化肥厂废水中总氮的研究

采用1株异养原核小球藻USTB-01对化肥厂废水中总氮的去除进行了研究。结果表明,添加一定量的磷酸盐和碳酸钠特别是葡萄糖分别作为磷、无机碳和有机碳源,不仅可以明显促进原核小球藻USTB-01的生长,而且可以大幅度提高废水的总氮去除效率。在4 d时间内原核小球藻USTB-01的生长从OD680 nm0.5增加到3.6,提高到7倍,而废水中总氮的浓度从125 mg/L降低到10.3 mg/L,去除率达到了93.1%,处理后的废水可以达标排放。不仅在高含氮废水的处理,而且在利用废水中的氮培养原核小球藻USTB-01的废水资源化利用方面均具有重要的意义。     

Antioxidative responses to arsenic in the arsenic-hyperaccumulator Chinese brake fern (Pteris vittata L.)

This study measured antioxidative responses of Chinese brake fern (Pteris vittata L.) upon exposure to arsenic (As) of different concentrations. Chinese brake fern was grown in an artificially-contaminated soil containing 0 to 200 mg As kg(-1) (Na2HAsO4) for 12 weeks in a greenhouse. Soil As concentrations at < or =20 mg kg(-1) enhanced plant growth, with 12-71% biomass increase compared to the control. Such beneficial effects were not observed at >20 mg As kg(-1). Plant As concentrations increased with soil As concentrations, with more As being accumulated in the fronds (aboveground biomass) than in the roots and with maximum frond As concentration being 4675 mg kg(-1). Arsenic uptake by Chinese brake enhanced uptake of nutrient elements K, P, Fe, Mn, and Zn except Ca and Mg, whose concentrations mostly decreased. The contents of non-enzymatic antioxidants (glutathione, acid-soluble thiol) followed similar trends as plant As concentrations, increasing with soil As concentrations, with greater contents in the fronds than in the roots especially when exposed to high As concentrations (>50 mg kg(-1)). The activities of enzymatic antioxidants (superoxide dismutase, catalase, ascorbate peroxidase, guaiacol peroxidase) in Chinese brake followed the same trends as plant biomass, increasing with soil As up to 20 mg kg(-1) and then decreased. The results indicated though both enzymatic and non-enzymatic antioxidants played significant roles in As detoxification and hyperaccumulation in Chinese brake, the former is more important at low As exposure (< or =20 mg kg(-1)), whereas the latter is more critical at high As exposure (50-200 mg kg(-1)).     

Municipal wastewater treatment using novel constructed soil filter system

The study gives a new approach for contaminant removal from municipal wastewater using constructed soil filter (CSF) and presents performance of two CSF units located in Mumbai, India. In this system, natural weathered rock is formulated which combines sedimentation, infiltration and biochemical processes to remove suspended solids and oxidisable organics and inorganics of the wastewater. Results show elevated dissolved oxygen (DO) levels, removal of COD (136-205 to 38-40 mg l(-1)) and BOD (80-125 to less than 12 mg l(-1)) suspended solids from 135-203 to 13-18 mg l(-1) and turbidity from 84-124 to 8-11 NTU, bacterial removal of 2.4-3.1 log order for Total coliform and Fecal coliform from site I which is almost 8 years old facility, and site II which is 3 years old. Estimated hydraulic retention time of 0.5-1.0 h, hydraulic loading of 0.036-0.047 m(3)m(-2)h(-1), no pretreatment, high DO levels in the effluent, no bio-sludge production, no mechanical aeration, low energy requirement (0.04 kW h m(-3)) and green aesthetic ambience are its unique features.     

人工湿地植物对重金属铅的抗性

随着含铅废水污染引起的生态安全问题日益加重,以及处理要求的日益严格,含铅废水的处理已成为目前研究和工程实践的重点。由于植物修复技术操作管理方便,成本低廉,处理效率高和选择性强等优点,植物修复已成为处理含铅废水的较有潜力的和行之有效的优化技术。实验参照水体重金属污染现状,模拟设置不同铅浓度的水体,通过盆栽水培实验及实验室分析测试,分别研究了重金属铅对芦苇、香蒲、鸭跖草这3种植物生长的影响、分析各种植物对铅的抗性的表现及重金属在植物体内的积累和分布,为人工湿地植物的选择提供科学依据。     

Risk assessment of boron in glass wool insulation

Background, aim and scope  Glass wools are man-made vitreous fibres, which consist principally of sodium, calcium and magnesium silicates, but may contain smaller amounts of other elements, including boron. The boron contents originate from the use of borates in the glass melting process as a glass former and a flux agent. During the production and application of glass wool insulation products, workers may legally be exposed to glass fibre up to the occupational limit value, commonly of 1 fibre/cm³. However, in practice, the fibre exposure will be at least ten times lower. Boron is a non-metallic element widely distributed in nature, where it occurs as boric acid, borates and borosilicates. Humans are mainly exposed to boron via vegetarian food and drinking water, mineral supplements and various consumer products. Boron is an essential element for plant growth, but the essentiality for humans is not proven, although intakes of trace amounts of the element seem to be useful for bone health and proper brain function; higher concentrations of boron, however, may be toxic. In relation to the European Union legislation on dangerous substances, an EU Expert Group has recommended classifying boric acid and borates with risk phrases for reproductive toxicity. The aim of this paper is to assess whether the new EU hazard classification of boron compounds should imply that glass wool products used for building insulation in the future should be labelled, “may impair fertility and cause harm to the unborn child”, because of the low boron content. Materials and methods  Boron intakes are estimated in a worst-case occupational situation with human exposure to glass wool fibres at the occupational limit of 1 fibre/cm³ by calculation of the mass of the amount of fibres inhaled during an 8-h work day. Fibres are supposed to be cylinders of glass with a length of 30 μm, an average diameter of 1.5–2 μm and containing either 1.5% or 3.5% boron. As a worst-case scenario, the density of the fibres is set to 2,700 kg/m³. The inhalation rate of the individuals at moderate work load was set to 2 m³/h. A worst-case scenario also corresponds to 100% retention and to 100% solubility of the retained fibres in the lungs. Results  With the normal boron content of 1.5% in glass wool fibres for building insulation, the extra daily occupational boron intake/uptake will be 0.03–0.06 mg B for 5 days a week. For more uncommon glass wool with maximum boron content of 3.5%, the worst-case daily boron intake/uptake will be 0.08–0.16 mg B. The main boron exposure in the general population is from vegetarian food, and the average daily dietary intake with food is estimated to 1.2–1.5 mg B/day. In addition, significant intakes may come with drinking water, especially from mineral water. In some instances, exposure from mineral supplements, cosmetics and other consumer products may be significant. For example, individuals taking mineral supplements, e.g. for bodybuilding, may have an additional intake to that of 1–10 mg/day. During the years, various organisations have recommended safe intake values for boron. Recently, the Scientific Panel on Dietetic Products, Nutrition and Allergies of the European Food Safety Authority (EFSA) has established the ‘Tolerable Upper Intake Level’ (UL) for the intake of boron (boric acid and borates) at 0.16 mg B/kg body weight per day or about 10 mg B/day for an adult. Discussion  The calculated, worst-case exposure scenario during an 8-h work day will result in an extra daily boron intake that only corresponds to about 10% of the average daily adult boron intakes through food and drinks of about 1.5 mg. The inter-individual variations in boron intakes from foods, water and supplements will be much greater than an eventual, very worst-case, additional intake of boron from inhalation of glass wool fibres. In addition, the combined intakes are far lower than the ‘Tolerable Upper Intake Level’ of 10 mg B/day for a person weighing 60 kg, as recommended by the European Food Safety Agency. The potential boron intake from inhalation of glass wool fibres is also much lower than boron intakes by workers in the boron industry, who at the present occupational limit value will be exposed to 50 mg of boron 5 days a week, or 100 times more than the worst case for glass wool fibres. Furthermore, in practice, exposure levels will mostly be ten to 100 times lower than the occupational limit used here as a worst case. Conclusions  The estimated boron intake from inhalation of glass wool fibres in occupational settings will be insignificant and without any health risks, even in the case of non-compliance with the occupational limit value. Any proposal requiring hazard labels on commercial glass wool products for building insulation, because of the boron content, is not supported by the present scientific knowledge. Recommendations and perspectives  The European Commission should ensure that the new EU hazard classification of boron compounds is not applied to commercial glass wool products for building insulation having a low content of boron.     

物化-生化组合工艺处理火炸药废水中试研究

针对火炸药废水毒性大、硝基化合物浓度高、COD浓度高、可生化性差的特点,采用"三维电极(TDE)-铁屑内电解-厌氧-曝气生物滤池"工艺对火炸药废水进行中试研究。结果表明,在进水初始浓度COD为3 330～5 330 mg/L,硝基化合物为200～300 mg/L情况下,此工艺不但能够稳定去除COD,去除率达到96.9%,且能高效去除硝基化合物,去除率高达99.6%。出水水质完全符合《兵器工业水污染物排放标准(火炸药)》(GB14470-2002)要求,系统运行稳定。