Estimates of AOT ozone indices from time-integrated ozone data and hourly air temperature measurements in southwest Sweden

Surface ozone concentration and surface air temperature was measured hourly at three coastal sites, four low elevation inland sites and two high elevation inland sites in southwestern Sweden. Diurnal ozone concentration range (DOR) and diurnal temperature range (DTR) were strongly correlated, both spatially and temporally, most likely because both depended on atmospheric stability. Accumulated ozone exposure above a threshold concentration of x nmol mol⁻¹ (AOTx) was estimated from time-integrated ozone concentration (as from diffusive sampling) and measures of ozone concentration variability. Two methods both estimated 24-h AOTx with high accuracy (modelling efficiencies >90% for x ≤ 40 nmol mol⁻¹). Daytime (08:00–20:00) AOTx could not be equally well estimated. Estimates were better for lower AOT thresholds. Diffusive ozone concentration sampling, combined with hourly temperature monitoring, could be a valuable complement to ozone concentration monitoring with continuous instruments.     

Plant cell death and cellular alterations induced by ozone: key studies in Mediterranean conditions

An account of histo-cytological and ultrastructural studies on ozone effect on crop and forest species in Italy is given, with emphasis on induced cell death and the underlying mechanisms. Cell death phenomena possibly due to ambient O₃ were recorded in crop and forest species. In contrast, visible O₃ effects on Mediterranean vegetation are often unclear. Microscopy is thus suggested as an effective tool to validate and evaluate O₃ injury to Mediterranean vegetation. A DAB-Evans blue staining was proposed to validate O₃ symptoms at the microscopic level and for a pre-visual diagnosis of O₃ injury. The method has been positively tested in some of the most important crop species, such as wheat, tomato, bean and onion and, with some restriction, in forest species, and it also allows one to gain some very useful insights into the mechanisms at the base of O₃ sensitivity or tolerance.     

Ozone exposure of field-grown winter wheat affects soil mesofauna in the rhizosphere

A 2-year open-top chamber experiment with field-grown winter wheat (Triticum aestivum L. cv. Astron) was conducted to examine the effects of ozone on plant growth and selected groups of soil mesofauna in the rhizosphere. From May through June in each year, plants were exposed to two levels of O₃: non-filtered (NF) ambient air or NF+ 40 ppb O₃ (NF+). During O₃ exposure, soil sampling was performed at two dates according to different plant growth stages. O₃ exposure reduced above- and below-ground plant biomass in the first year, but had little effect in the second year. The individual density of enchytraeids, collembolans and soil mites decreased significantly in the rhizosphere of plants exposed to NF+ in both years. Differences were highest around anthesis, i.e. when plants are physiologically most active. The results suggest that elevated O₃ concentrations may influence the dynamic of decomposition processes and the turnover of nutrients.     

盐胁迫下耐盐与盐敏感水稻的RAPD和POD同工酶检测

对耐盐、一般耐盐和盐敏感３种水稻材料进行了ＲＡＰＤ和同工酶检测,结果发现：３３个引物（Ｎ－１－Ｎ－１２,Ｓ４５０－Ｓ４７０）中,２７个引物具有拉增产物,拉增片段大小分布在０．２－３．４ｋｂ之间,说明在一定程度上反映了３种对盐具有不同耐盐性水稻在基因组ＤＮＡ分子水平上的差异,以Ｓ４５０为引物,在强耐盐的７７９中扩增出１个１．１ｋｂ的特异ＤＮＡ片段（Ｓ４５０１１００）,而在对盐敏感的早花２号中,以Ｎ－     

Improved enzymatic hydrolysis of waste paper by ozone pretreatment

Waste paper samples made from newsprint, copier paper, and magazine paper, as well as samples of kraft pulp and thermomechanical pulp, were pretreated with ozone to improve enzymatic hydrolysis. The ozone treatment of pulps of newsprint and of magazine paper increased the specific surface areas and total pore volumes while decreasing the lignin content so that these values became similar to those of thermomechanical pulps. These morphological and chemical changes in the pulps resulted in the increased access of cellulase to the pulp fiber surface and increased enzymatic hydrolysis. For copier paper, in which the lignin content was very low, additives on the pulp fiber surface were oxidized and removed by ozone treatment and extraction, and this allowed improved enzymatic hydrolysis. In contrast, surface areas and total pore volumes of kraft pulp and bleached kraft pulp were decreased by the ozone treatment, resulting in morphological changes in the pulps that decreased enzymatic hydrolysis.     

Ozone and/or Water Stresses Could have Influenced the Betula ermanii Cham. Forest Decline Observed at Oku-Nikko, Japan

A serious forest decline of Betula ermanii Cham. has been observed at Mt. Mae-Shirane, Oku-Nikko, Japan, where high ozone (O₃) concentration and severe water deficiency have been measured. In order to consider the possibility whether O₃ and/or water stresses could have been the causes of the forest decline of B. ermanii, plant growth experiments were conducted in environment-controlled growth cabinets. Two-year-old seedlings of B. ermanii were exposed to either charcoal-filtered air (O₃ concentration <5 ppb) or 50 ppb O₃ (daily average, ranging between 20–100 ppb) for 123 days at 20.0/12.5 ± 1.0°C (day/night) and 70/80 ± 7% relative humidity (day/night). Simultaneously, seedlings were treated with three watering regime: 1.0 < pF < 1.8 (no water stress), 1.8 < pF < 2.5 (mild water stress) or 2.5 < pF < 3.0 (severe water stress). O₃ exposure significantly reduced the dry weights of leaf, root and the whole plant, while water stress significantly reduced the dry weights of each organ and the whole plant. Significant reductions of net photosynthesis, transpiration and stomatal conductance were also observed under O₃ and/or water deficiency treatments, while contents of RuBP carboxylase/oxygenase (Rubisco), chlorophyll _a+b and some essential nutrient elements (N, P, K, Mg and Ca) were not markedly changed. It was suggested that the decrease in net photosynthetic rate induced mainly by stomatal closure was the major cause of the growth reduction under O₃ and/or water stresses. No significant interactions between O₃ and water stresses were observed in terms of the depression of dry matter production, which suggested that simultaneous stress treatments of O₃ exposure and water deficiency could affect the tree growth of B. ermanii additively.     

Comparative Salinity Tolerance of Three Indigenous Tropical Freshwater Cladoceran Species; Moinodaphnia Macleayi, Ceriodaphnia Rigaudii and Diaphanosoma Brachyurum

The acute salinity tolerance of three tropical freshwater cladoceran species, M. macleayi, C. rigaudii and D. brachyurum was determined. The existence of these species represented new records for Trinidad and Tobago, a tropical Caribbean island. It has a large oil based industry, in which, the primary effluent (saline produced water) is discharged directly into many freshwater systems. Cladoceran species are used routinely in temperate regions, to assess the impacts of chemicals and effluents in freshwater systems. However, relatively few studies have assessed the salinity tolerance of these organisms. Test organisms were assayed using seven salinity treatments (0, 1, 3, 5, 10, 15, 20, 25‰) prepared by volumetrically mixing natural filtered seawater with dilution water. C. rigaudii had a 48 h LC50 of 1.6‰, M. macleayi 1.5‰ and D. brachyurum <1‰. The CSmax (critical salinity maximum) for C. rigaudii and M. macleayi was 3‰ after 48 h, compared to 1‰ for D. brachyurum. There was no salinity value at which there was 100% survival. The resulting salinity response curve was a straight line which indicated that each species was intolerant of salt. Consequently, any of these can be considered as a representative freshwater organism for toxicity testing in Trinidad and Tobago.     

The use of respirometric measurements to determine the toxicity of textile dyes in aqueous solution and after oxidative decolourisation processes

Selected results from the degradation of reactive-dye hydrolysates after UV irradiation, ozonation and sodium peroxodisulphate (NaPS) treatment are presented. Reactive dyes with representative chromophores and anchor groups were chosen for the research project. Different stages of oxidative decolourisation were examined and determined by water parameters for biological degradation (BOD). The paper focuses on toxicity tests with Pseudomonas putida to consider whether the oxidative treatments result in products with a risk for the environment. Tests were performed with the AQUALYTIC^® Sensomat System, which measures biological oxygen demand (BOD). It was determined that the chosen oxidative treatments had as a rule no bearing on respiration of P. putida. Experiments with hydrolysates after short-term UV irradiation resulted in a slightly increased but not long-lasting toxicity in comparison with treatments with ozone or NaPS. Toxic effects were found in tests with hydrolysates of metalliferous dyes. During oxidative treatment, metals were liberated from the chromophores. This did cause complete inhibition of respiration of P. putida. Dye Blue E, a member of a dye class with chlorotriazine anchor groups, was itself found to be toxic, caused by the reactivity of the anchor group. The hydrolysate is only of minor toxicity.     

臭氧/高锰酸盐预氧化对生物过滤净水效能的影响

比较了臭氧(O3)和高锰酸盐复合药剂(PPC)对水源水预氧化的助凝效果及其对后续陶粒生物过滤净水效能的影响.结果表明,两种预氧化剂投加量均为2 mg/L时,PPC的助凝效果较为明显,浊度和溶解性有机碳(DOC)的去除率分别由未投加氧化剂时的85.7%和24.2%提高到88.3Z和35.2%;O3能够增加沉淀后水的可生化性,使特征紫外吸光度(SUVA)由0.97L/(m·mg)降至0.89 L/(m·mg).PPC预氧化有助于生物过滤对浊度的稳定去除,而O3预氧化则有助于生物过滤对DOC的去除.与O3预氧化相比,PPC预氧化有利于后续生物过滤运行初期对NH4 -N的去除,二者后续生物过滤在前3个月对NH4 -N的平均去除率分别为26.6%和73.1%,运行后期二者NH4 -N去除率接近.当进水NH4 -N大于2.0 mg/L时,DO是其去除的主要限制因素.