Mobility and breakdown of asulam in the soil and the possible impact on the environment

Asulam reaching the soil either directly as spray drift or as rain washings from bracken fronds would, due to its rapid mobility in soil, be expected to leach down the soil profile into the drainage water and thereby contaminate streams and water catchments. The mobility of asulam in soil is influenced by pH, where undissociated asulam will leach less rapidly than the associated form (asulam pK_a 4·82). This is particularly relevant in the case of bracken as it can grow satisfactorily over a wide range of pH values (3·6 – 7·6). Adsorption coefficients expressed as Kd values [(μg asulam/g soil)/(μg asulam/ml solution)] were 2·54, 1·94 and 0·96 at pH readings of 4·0, 4·3 and 4·9 respectively. Another factor involved, the breakdown of asulam, was shown to be temperature dependent, 30·95, 7·65 and 2·50% remaining after 28 days at 5, 18 and 25°C respectively, thus underlining the influence of geographical regions and climatic conditions on asulam behaviour.     

Effects of a tropical cyclone on littoral and sub-littoral biotic communities and on a population of Dugongs (Dugong dugon (Müller))

The extensive damage to littoral and sub-littoral biotic communities caused by cyclone ‘Althea’, which crossed the tropical coast of Queensland on 24 December, 1971, are described. The effects of high wind speeds (mean 129·7 km/h), turbulent seas, storm surges, and heavy rainfall on mangrove, sea grass, algal, and coral reef communities are discussed. Mangroves withstood the immediate effects of the cyclone and protected coastal areas. However, long-term effects on mangroves are apparent. Severe wave action, shifting sand, and low salinities caused extensive damage to sea grass, algal, and coral reef communities. The effects of the cyclone on a Dugong population are described. The catches of Dugongs in shark nets set off Townsville increased from an average of 12·7 per year before the cyclone to 41 in 1972 (the year following the cyclone). This increase is attributed to increased movements in search of food, following extensive damage to sea grass beds. Associated with increased movements, there occurred a change in diet whereby large amounts of brown algae were eaten in addition to sea grasses. Sex and size (age) distributions of captured Dugongs are given and their possible significance discussed.     

14C-labelled material leached from the rhizosphere of plants supplied continuously with 14CO2

¹⁴C, supplied continuously to plant tops as ¹⁴CO₂, was recovered in water-soluble organic material when pots with wheat, clover or ryegrass growing in a podzolic sand were leached with distilled water at weekly intervals. Leachates and root-free soil contained, respectively, 0·15–0·3 and 2·7–5·4% of the total ¹⁴C activity recovered after 8 weeks growth. Plant derived C represented 0·8–1·3% of the total organic C in root-free soils.Water-soluble organic C decreased in successive leachings to reach a steady value, approximately 20 μgC/ml for all treatments. Labelled C represented 14·4–19·5% of this value. Total organic C recovered in the leachates accounted for ca. 0·5% of the soil C, for all treatments. Approximately 15% of the labelled material in the final leachates behaved as neutral sugar, the remainder occurring in a charged complex. A membrane filter (M.Wt. cut-off ~ 10³) retained >60% of the radioactivity.     

Use of water boatmen (Corixidae) in the classification of lakes

Data populations of Corixidae in 55 water bodies are considered. There is a significant correlation (p0·07 ? <0·001) between the distribution of each of six species of Corixidae and the conductivity of water bodies. Similarly, two species show significant correlations (p 0·07 ? <0·001) with a function of lake area and shape. There is also a significant correlation (p <0·001) between conductivity and bicarbonate ion-chloride ion ratios. It is argued that corixid populations may give an indication of the nature of water bodies and provide a valuable means of comparison for both investigation and conservation. A quantitative method of data treatment is described which facilitates comparison.     

Aerodynamic roughness of cultivated soil and its influences on soil erosion by wind in a wind tunnel

Serious soil erosion on cultivated soil by wind occurs extensively in semiarid regions. Surface roughness of cultivated soil that can be characterized by aerodynamic roughness length (z₀) has important implications to wind erosion. Here we report the wind tunnel results of aerodynamic roughness lengths of five treated soils and soil wind erosion rates at different z₀ and wind velocities. The results suggest that the diameter of the largest soil clods exposed and uniformly distributed on the soil surface is an important factor that controls aerodynamic roughness length. Negatively related to aerodynamic roughness length under provided wind velocity, wind erosion rate is a function of z₀ and wind velocity for cultivated soil. Erosion rates decreased with aerodynamic roughness length especially when z₀ is smaller than 0.1 cm and increase non-linearly with wind velocity, and that the smaller the aerodynamic roughness is, the more rapid that increase will be. Regression model comprising z₀ and wind velocity is developed for predicting wind erosion rates for cultivated soil, which quantitatively reflects the influences of aerodynamic roughness length on soil erosion at various wind velocities.     

Conservation of amenity trees in the Lothian Region of Scotland

Amenity trees, defined as all trees excluding those in Forestry Commission and grant-aided woodlands, worked coppice, commercial orchards and hardy-stock nurseries, were surveyed in the Lothian Region between 1972 and 1975. The Region (c. 188,000 ha or 1,877 km²) was stratified into three land categories-(i) burghs (Scottish equivalent of English boroughs), (ii) lowland rural and (iii) upland rural, parts of at least 10% of the 1 km squares (vide Ordnance Survey maps) of each land category being surveyed; the surveyed squares were selected randomly.Numbers of trees per ha ranged from 59 in burghs to 43 and 24 in lowland and upland (above 150m) rural areas respectively. In total there were 6·7 ± 1·9 million amenity trees in the Region divided as follows: 1·4 ± 0·4, 3·2 ± 0·9 and 2·1 ± 0·6 millions between the burghs and lowland and upland rural areas respectively; c. 1·0 m of the 1·4 million trees in burghs were located in Edinburgh. Approximately 70% of trees were deciduous with a larger proportion of conifers in upland areas than elsewhere; sycamore (Acer pseudoplatanus L.), hawthorn (Crataegus spp.) and Scots pine (Pinus sylvestris L.) were the commonest of 76 species or generic groupings recorded, accounting for 11·6, 11·1 and 10·5% respectively of the regional total. Birch (Betula spp.) was the commonest deciduous tree in upland areas where ash (Fraxinus excelsior L.) and beech (Fagus sylvatica L.) were more abundant than sycamore. In the burghs wych elm (Ulmus glabra Huds.) was more numerous than hawthorn and less than sycamore. Trees in Edinburgh differed greatly from those in the smaller towns (burghs) with more rural atmospheres, where sycamore, wych elm, hawthorn, elder and birch contrasted with apple, lilac, flowering cherry, sycamore and rowan occurring abundantly in Edinburgh.Excluding Edinburgh, over 50% of the Region's trees were identified in broadleaved (26·7%), coniferous (21·4%) and mixed (13·6%) woodlands, with 12·0% and 8·1% occurring in shelterbelts and hedgerows respectively; gardens and parks, of all sorts, only accounted for 4·5% and 1·1% respectively.Size class distribution ssuggest that there are sufficient developing saplings to maintain the existing number of mature trees but that wych elm (Ulmus glabra Huds.), unless devastated by Dutch elm disease, sycamore and ash are likely to increase at the expense of oak (Quercus spp.), lime (Tilia spp.), Scots pine and beech. In some situations, however, the resourse seems to be seriously deficient in saplings, e.g. oaks in parks.     

风和风沙流对玉米幼苗叶片膜透性和膜保护系统的影响

为了解玉米幼苗对风和风沙流危害的生理响应机制,2013年春季在内蒙古自治区东部科尔沁沙地研究了0 m·s-1(CK)、6 m·s-1、9 m·s-1、12 m·s-1、15 m·s-1和18 m·s-1等6个风速下净风和风沙流(风沙流强度相应为0g·cm-1·min-1、1.00 g·cm-1·min-1、28.30 g·cm-1·min-1、63.28 g·cm-1·min-1、111.82 g·cm-1·min-1和172.93 g·cm-1·min-1)10 min吹袭对玉米幼苗叶片膜透性影响及其膜保护系统响应。结果表明,净风吹袭下,随风速增强,玉米幼苗丙二醛(MDA)含量和过氧化物酶(POD)活性趋于增加,膜透性和过氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性及可溶性糖、脯氨酸含量呈波动式变化;其中12~18 m·s-1处理的SOD活性,6 m·s-1和12~18 m·s-1处理的POD活性,6 m·s-1和12 m·s-1处理的CAT活性,以及6 m·s-1处理的可溶性糖含量和18 m·s-1处理的脯氨酸含量显著高于CK。风沙流吹袭下,随着风沙流强度增大,玉米幼苗MDA含量、SOD活性和可溶性糖含量趋于下降,但膜透性和POD活性显著增强,除18 m·s-1处理的脯氨酸外,其他处理的CAT活性和脯氨酸含量变化不显著。结果说明,短暂的净风吹袭对于玉米幼苗叶片的细胞膜危害不明显,而风沙流胁迫致其细胞膜结构受损严重;风和风沙流胁迫下对细胞膜起到保护作用的主要是POD,在18 m·s-1大风和风沙流胁迫下脯氨酸起到了渗透调节作用。     

Leaching of ethylene glycol and ethanol in subsoils

The use of the heat pumps connected to ground coils wins widespread interest in the heating of buildings, but in cases of leakage it may involve a risk of ground water pollution caused by anti-freeze mixture components. The adsorption of individual components, such as ethylene glycol, ethanol, methanol, and benzoic acid onto different soil types was studied at 6 °C by use of a batch procedure. No adsorption (or only slight) was observed for any of the test compounds onto samples of subhorizons of sandy till, clayey till, and melt water sand. Leaching experiments with undisturbed soil cores of sandy till showed that ¹⁴C-labelled ethylene glycol or ethanol closely followed the movement of water when cloride was used as a tracer. The percolation experiments were conducted during 79 to 154 day periods at 10 °C and under anaerobic conditions. Darcy velocities varied between 1 and 3 mm day^?1. About 100% of the added amounts of ¹⁴C were recovered in the effluents, although only 74 to 77% of ethylene glycol and 84 to 89% of ethanol were determined as the parent compounds by gas chromatography. Experiments on leaching of ethanol under controlled oxygen supply showed that degradation took place dependent on oxygen availability.     

利用PAM防治松散扰动沙土风蚀效果的风洞试验研究

翻耕农地和建设工地的扰动松散土是沙尘的重要来源。防止扰动土风蚀是保护生态环境的重要内容。该研究通过室内风洞模拟试验，研究了PAM对于提高松散扰动土起动风速、防止风蚀的效果。试验分别采用0°、10°、20°、30°不同的吹角，地表处理为：喷施PAM（用量分别为0.5，1，2，4 g/m²）、喷施清水和未加处理的自然松散扰动（沙）土。试验结果表明：通过表面喷洒PAM溶液可以显著地提高松散扰动土的起动风速，达到控制风蚀的目的；仅喷洒清水处理也可以在一定程度上提高沙尘的起动风速，但其效果甚微；如果松散(沙)土喷施PAM的表面不被扰动（无裂纹），用于松散土风蚀防治时PAM用量控制在1 g/m²以上就可以有效防止风蚀发生，试样经受风速为14 m/s左右的大风、历时30 min而未产生风蚀。     

Estimation of Dust Emission Amount for a Dust Storm Event Occurred in April 1998 in China

The threshold friction velocities for dust rises in inland China are examined using WMO synoptic station data and the soil types in the source region to estimate dust emission amounts for a dust event occurred from 13 to 24 April 1998 in China. The dust-rise reports in the WMO synoptic data are used for the delineation of dust source regions that are found to be composed of the Gobi, Sand and Loess regions according to soil types in inland China. The estimated threshold friction velocities with the use of wind speeds observed in the Gobi, Sand and Loess regions are found to be about 60, 50, and 40 cm s^-1, respectively. The estimated dust-rise occurrencegrids by both the grid interpolated observed wind and the MM5 model wind well coincide with the areas of strong wind speeds. However, the dust-rise areas estimated by the model are larger than those estimated by the observed wind, whereas the friction velocities estimated by the model in the dust-rise areas are much smaller than those estimated by the observed wind, which result in less amount of dust emission by the model in all source regions. The 10-day accumulated total dust emission estimated by the observed wind during the dust storm event is found to be 4.64 × 10⁸ ton in the whole source region of 3.29 × 10⁶ km². Of which 85, 9 and 6% are, respectively, contributed by the Gobi, Sand and Loess regions,suggesting the dominant emission from the Gobi region for this event.The model estimated total dust emission is found to be about 56% of that estimated by the observed wind, indicating some improvement of the model being required.     

Modelization of the mercury fluxes at the air-sea interface

Aqueous and atmospheric Hg° concentrations for remote marine areas such as the equatorial Pacific Ocean and for coastal seas such as the North Sea and the Scheldt Estuary are discussed. Biological processes seem to be at the origin of the supersaturated Hg° concentrations in the water. On the other hand, transfer velocities across the air-sea interface were calculated with a classical shear turbulence model and with a wave breaking model. With these data, Hg° fluxes from the sea to the atmosphere were calculated: in the Pacific Ocean they range from 0.43 to 6.5 μg g Hg.m^?2. yr^?1 at a wind speed of 2.8 m.s^?1 and from 10.3 to 156 μg Hg.m^?2 yr^?1 at a wind speed of 54 m.s^?1, but they are still higher when wave breaking is considered (from 11 to 168 μg Hg.m^?2.yr^?1). These transfer fluxes are an order of magnitude higher in the Scheldt Estuary.     

Threshold wind velocity as an index of soil susceptibility to wind erosion under variable climatic conditions

Wind erosion starts when the threshold wind velocity (µ_t) is exceeded. We evaluated the sensitivity of µ_t to determine the wind erosion susceptibility of soils under variable climatic conditions. Three years field data were used to calculate µ_t by means of the equation µ_t = ū ‐ σ Φ⁻¹ (γ), where ū is the mean wind speed (m s⁻¹), σ the ū standard deviation (m s⁻¹), γ the saltation activity and Φ the standard normal distribution function of γ. Saltation activity was measured with a piezoelectric sensor (Sensit). Results showed that ū of the whole studied period (3·41 m s⁻¹) was lower than µ_t (7·53 m s⁻¹), therefore, wind erosion was produced mainly by wind gusts. The µ_t values ordered in the sequence: Winter (6·10 m s⁻¹) < Spring (8·22 m s⁻¹) = Summer (8·28 m s⁻¹) < Autumn (26·48 m s⁻¹). Higher µ_t values were related to higher air humidity and lower wind speeds and temperatures. The µ_t values did not agree with the erosion amounts of each season, which ordered as follows: Summer (12·88 t ha⁻¹) > Spring (3·11 t ha⁻¹) = Winter (0·17 t ha⁻¹) = Autumn (no erosion). Low µ_t and erosion amounts of Winter were produced by a scarce number of gusts during eroding storms. We concluded that µ_t is useful as an index of soil susceptibility to wind erosion of different climatic periods. The use of a unique µ_t value in wind erosion prediction models can lead to erroneous wind erosion calculations. Copyright © 2008 John Wiley & Sons, Ltd.     

Crassula helmsii (T. Kirk) cockayne: Is it an aggressive alien aquatic plant in Britain?

The occurrence of this alien aquatic macrophyte has rapidly increased during the last decade reaching c. 100 sites mainly in England; these range from shallow acidic seasonal pools to small, more alkaline, nutrient-rich lakes. It is frequently dominant and can grow in an emergent form from 0·7m above the water to a submerged form 1·3m in length, to depths of c. 3m. Plant bimass is generally high with little seasonal cessation of growth. The habit is frequently a dense sward growth which smothers out other flora; it is present in c. ten reserves and is causing concern. It is widely available from aquatic suppliers, it has an enormous potential to propagate from small fragments and has a high growth rate. It is associated with soft sediments and possibly iron-rich areas; this is confirmed by growth trials in static water tanks. In flowing water trials, growth was even faster in water velocities up to 0·32 m s⁻¹, indicating its potential—although no river sites in Britain are yet known. Control by physical removal, often recommended, results in numerous propagules and should be combined with a secondary technique. This initial study suggests that this plant will remain a problem and caution is required to prevent its further spread. Studies of techniques for its control are needed.     

Relationships of physical and chemical conditions to species diversity and density of gastropods in English lakes

The qualitative and quantitative species composition of the communities of Gastropoda in ten representative meres in the North West Midlands, England, are described and shown to differ significantly. Environmental data on water chemistry, percentage organic matter in the substrata, mere area and altitude were estimated. The data matrix was examined by regression analysis. Conductivity shows significant positive correlations with calcium (p < 0·001), magnesium (p < 0·001), sodium (p < 0·01) and sulphate (p < 0·05) ions whilst there is a significant negative correlation with altitude (p < 0·02). The total individuals mere ⁻¹ of Gastropoda show the most significant positive correlation with calcium ions (p < 0·05) whilst species mere⁻¹ (species diversity) are similarly correlated with calcium + area + percentage organic matter (p < 0·02). These results are compared with data from 58 North West Midlands meres and 43 Lake District tarns and lakes. The relationships demonstrated are used to develop a procedural and predictive model which facilitates the choice of water bodies for conservation.     

Mobility and Availability of Copper in Agricultural Soils Irrigated from Water Treated with Copper Sulfate Algaecide

A mesocosm system was designed to study evaporation kinetics and transport of TCE in flowing surface water. The airtight unit, with a total internal volume of 52.01?×?10^?2 m³, was fabricated with glass and Teflon material, and was provided with 8.53 m long channel to simulate water flow in an open channel. The peristaltic pumps, connected to the inlet and the outlet of the mesocosm, provided a constant water flow through the channels. The experimental studies were conducted at two different velocities, 9.42?×?10^?3 and 4.71?×?10^–3 m/s, respectively. For both the velocities, a tracer (NaBr) test confirmed uniform water flow in the channels. The total length and the length between the sampling ports were found sufficient to record gradual decrease in TCE concentrations along the direction of the flow in the channels. The volatilization coefficient for TCE was found to be 0.49 and 1.07 h^?1 for the experiments conducted at lower and higher water velocities, respectively. The TCE evaporation half life (t 1/2) and the corresponding evaporation half distance (d 1/2) were 1.41 h and 23.98 m for lower velocity, and 0.65 h and 21.96 m for higher velocity, respectively.     

Desorption Behaviour of Polycyclic Aromatic Hydrocarbons in Harbour Sludge from the Port of Rotterdam,The Netherlands

Desorption of eight polycyclic aromatic hydrocarbons (PAH) fromtwo harbour sludges from the Port of Rotterdam, the Netherlands,was studied by column elution experiments. When water moves in a sludge layer desorbing contaminants like PAH can be dispersedin the environment. Separation of liquid and solid phase inbatches of sludge, stored for more than three years, by ultra-centrifugation at 4 °C yielded equilibrium partition coefficients. Temperature effects could not account for the observed differences with reported literature values. The differences are attributed to the contact time of PAH in thesediment. Laboratory data reported in the literature were oftenobtained after short contact times and therefore may not represent equilibrium partitioning. Our values represent contacttimes in excess of three years and are therefore more representative for the field conditions. Partition coefficientsobtained from column elution experiments were slightly above those obtained from the batch experiments. During column elutionof the sludge from the Beneden Merwede sorption equilibriumwas absent for the lighter compounds. This is attributed to the presence of a large portion of immobile water in the columns. Elution in the Beerkanaal columns occurred at near sorption equilibrium although pore water velocities were higher. Assumingthat desorption is diffusion controlled, observed desorption inboth materials could be explained. The non-equilibrium desorptionin the Beneden Merwede sludge for phenanthrene, and to alesser extent for anthracene and fluoranthene, could be describedby a diffusion limited model assuming spherical particles.     

Non-polar macroreticular resin to recover phenolic acids from a subtropical latosol

A technique has been developed to extract soil phenolics by their adsorption onto resin, the separation of resin from soil, and desorption from the resin followed by high performance liquid chromatography (HPLC) analysis. Four representative phenolic acids, p-hydroxybenzoic, p-hydroxycinnamic, p-methoxybenzoic and 2,4-dimethoxybenzoic acids, were added to a subtropical soil (66 nmol g^?1 soil) and recovered by extraction with Amberlite XAD-4 resin. The recovery efficiency of the added phenolics was greater using a flotation method to separate resin from soil than by a filtration method. The recoveries of p-hydroxybenzoic acid and p-hydroxycinnamic acid decreased with increasing extractant pH. Recoveries of p-methoxybenzoic acid and 2,4-dimethoxybenzoic acid increased slightly with increasing pH. The addition of NaCl to the XAD-4 resin extractant generally increased the recovery of phenolics by filtration but not by flotation. The recoveries of phenolics from the soil by extraction with XAD-4 resin were much greater than by alkaline extraction at pH 11.     

The influence of the physical attributes of a spruce shoot on momentum transfer

The drag force on fourteen three-prong spruce shoots (Picea rubens) was measured over a range of wind tunnel velocities. The boundary layer resistance to momentum transfer was found to be influenced by the shoot orientation, inclination, and flexibility. Momentum transfer was also influenced by shoot needle density; however, this influence was a function of the shoot orientation. For wind velocities below about 2.0 m s^?1, these factors did not greatly influence the momentum transfer to the shoots. For wind velocities above about 2.0 m s^?1 the momentum transfer decreased with; (1) decreasing inclination of the shoot to the airflow, (2) decreasing shoot flexibility, and (3) orientating the shoot so that the densely-needled side of the shoot faced the wind. A pair of empirical equations were derived relating momentum transfer to wind velocity.     

Residual Organic Compound Removal from Aqueous Solution Using Commercial Coconut Shell Activated Carbon Modified by a Mixture of Seven Metal Salts

The modified activated carbon (MAC) derived from commercial coconut shell activated carbon (AC) with mixture of seven metal salts was used as an adsorbent to remove target residual organic compound (sucrose) from aqueous solutions in batch modes. The results indicated that the highest adsorption capacity of sucrose onto MAC reached when the AC was modified at the ratio of impregnation of AC with mixture of seven metal salts, including nitrate silver (AgNO₃), manganese nitrate (Mn (NO₃)₂), potassium bichromate (K₂Cr₂O₇), nitrate cobalt (Co (NO₃)₂·6H₂O), nitrate copper (Cu (NO₃)₂·3H₂O), nitrate nickel (Ni (NO₃)₂·6H₂O) and nitrate iron (Fe (NO₃)₂·9H₂O) of 3% (w/w). The most appropriate conditions for sucrose adsorption onto MAC in batch experiments obtained at pH 7, contact time of 120 min, 800 mg MAC/50 mL of sucrose solution with initial concentration of 1500 mg/L. At this condition, the highest adsorption capacity of sucrose onto MAC reached 28.28 mg/g. The Langmuir, Freundlich, and Sips adsorption isothermal equilibrium models can adequately describe the adsorption properties of sucrose on MAC. The adsorption kinetic of sucrose onto MAC obeyed pseudo-first-order and pseudo-second-order models with the chemical sorption process. The saturated MAC was recovered by heat from an oven. The highest recovery efficiency of saturated MAC obtained at 180 °C in 120 min. The highest adsorption capacity of sucrose onto recovered MAC was 24.31 mg/g, appropriately adsorption capacity of initial MAC.     

Reduction in soybean yield after exposure to ozone and sulfur dioxide using a linear gradient exposure technique

A linear gradient field exposure system was modified from one originally described by Shinn et al. (1977) and used to expose field grown soybeans (Glycine max cv Hark) to a concentration gradient of a mixture of two gaseous pollutants: SO₂ and 0₃. Since this technique does not use enclosures, study plants experienced near ambient fluctuations in environmental conditions, including wind, and hence were exposed to widely fluctuating pollutant concentrations. Plants in the gradient system were exposed to both pollutants for 57 h on 12 days during the pod-filling period (31 August–17 September). Mean concentrations during the 57 h of exposure at the ‘high’ end of the gradient were 0.16 and 0.06 µl l^?1 (PPM) SO₂ and O₃, respectively, with 10 h at greater than 0.25 and 0.10 µl^?1 SO₂ and O₃, respectively. Total doses for these plants were estimated to be 9.0 and 3.5 µl^?1 · h SO₂ and O₃, respectively. Comparison with plants exposed to ambient air indicated that exposure to SO₂ and O₃ reduced total yield per plant and dry mass per bean by as much as 36 and 15 %, respectively. Since concurrent exposure to a much higher dosage of SO₂ alone (20.2 µl l^?1 · h) was observed in a separate experiment to have no significant effect on yield, 03, although present at moderately low levels, was probably responsible (alone or synergistically with SO₂) for the greatest reduction in seed size and yield.