外加镍在土壤中的形态与再分配

镍处理土壤经室内培养12周后,采用连续提取技术对试验土壤中镍的形态与再分配方式进行了研究。研究结果表明,外加的水溶性镍进入土壤后的主要存在形态与添加的剂量有关:低剂量时,以铁锰氧化态为主,这一形态在100mg·kg-1处理土壤中占比例最大,达到31.6%;高剂量时,以交换态为主,这一形态在1600mg·kg-1处理土壤中占比例最大,达到48.4%。随着镍添加剂量由0(对照)增加到1600mg·kg-1,再分配系数逐渐由1.00增大到30.65;金属结合强度系数则由0.90减小至0.25,也反映出进入土壤中镍的剂量较大时,镍是以不稳定的形态占优。试验结果也证实了土壤具有减小镍的环境危害的作用,但这种缓冲能力是有限的。随着时间的推移,镍的形态会继续发生变化,但这一转化过程是缓慢的。因此,一旦土壤发生重金属污染,其对土壤环境的影响将是长期的。     

芜湖市郊土壤污染对土壤动物群落结构的影响

研究表明，芜湖市郊农田土壤动物群落的组成与数量随污染程度的加重而减少，土壤动物密度也呈同样的变化趋势，特别是中小型土壤动物，优势类群数量发生较大消长，常见类群和稀有类群的组成逐渐减少．多样性指数H与重金属污染程度之间关系因受到季节的影响而变得复杂：冬季和初夏污染较重样地优势类群数量减少，群落均匀性指数E增加而优势度指数C减小，多样性指数H较高；而春季处于过渡阶段，某些类群(如螨类)数量爆发，C增高，H较小．土壤动物群落密度一类群指数DG随污染加重而减小．受到重金属污染的农田土壤动物的表聚性减弱，甚至出现逆分布现象．图1表4参15     

Changes of Soil Microbiological Properties Caused by Land Use Changing From Rice–Wheat Rotation to Vegetable Cultivation

A survey was done recently in Jiaxing city of Zhejiang Province in the Yangtze River Delta to compare the differences of soil microbiological properties among paddy soils with different land use including continuous open-field vegetable cultivation (OFVC), plastic-greenhouse vegetable cultivation (PGVC) and traditional rice–wheat rotation (RWR). The soil types included are percolating, permeable and waterlogged paddy soils. The results indicate that the microbial flora was markedly changed as the land use changed for all the three soil types. In continuous vegetable cultivation soils, especially in PGVC soils, the bacteria amounts decreased dramatically, but the fungal and actinomyce amounts increased as compared with RWR soils. The dehydrogenase activities decreased significantly in vegetable soils, especially in PGVC soils as compared with RWR soils. The microbial biomass C and the total phospholipid contents (TPL) in vegetable cultivation soil greatly decreased as compared with RWR soils. Biolog analysis indicated that the kinds of carbon sources that could be metabolized by native microbes in PGVC soils greatly decreased as compared with OFVC soils and RWR soils, revealing that microbial diversity had decreased since land use change. The activities of some soil enzymes including urease, invertase and phosphase were all lower in OFVC soils than those in RWR soils, and those in PGVC soils were the lowest. The degradation of microbiological activities in continuous vegetable cultivation soils, especially in PGVC soils, as compared with RWR soils might have been caused by soil acidification and accumulation of salts due to overuse of both organic and inorganic fertilizers in vegetable cultivation.     

磷肥施用量对缺锌土壤上水稻生长的影响

磷肥施用量对缺锌土壤上水稻生长的影响李延，潘伟彬（福建农业大学土化系，福州３５０００２）（闽西职业大学，龙岩３６４０２１）ＥｆｆｅｃｔｏｆＰｈｏｓｐｈａｔｉｃＦｅｒｔｉｌｉｚｅｒｏｎＧｒｏｗｔｈｏｆＲｉｃｅｏｎＺｉｎｃＤｅｆｉｃｉｅｎｔＳｏｉｌ￥Ｌｉ...     

Soil Lead at Elementary Public Schools: Comparison Between School Properties and Residential Neighbourhoods of New Orleans

Soil studies, conducted in Maryland, Minnesota and Louisiana, have described the urban pattern of lead contamination. They have shown that the highest amounts of lead cluster within the interior of the largest cities. The results of the New Orleans urban patterns of distribution of soil lead provided the basis for further study. The hypothesis was tested that elementary school properties have the same pattern of soil lead contamination as their neighbouring residential communities. Thirty New Orleans Public Elementary Schools were selected for this study. Surface samples (2.5cm or 1 inch depth) were collected from playgrounds and next to entrances of each school. Results showed that soil lead on school properties follows the same relative contamination patterns (pvalue10^–5) as soil lead on residential properties of neighbouring communities. Schools however, have significantly lower lead contamination than the neighbouring residential properties. Innercity school properties present a higher risk of soil lead exposure than mid and outercity schools. Soils next to innercity school entrances showed the highest lead, with 18.5% having concentrations over 400gg^–1. Systematic landscaping around the school entrances would significantly reduce the hazard from lead dust contaminated soils.     

新构造运动对安徽土壤分布的影响

安徽地跨亚热带与温带,过渡性特征明显,境内有山地,丘陵和平原,自然地理景观复杂多样,各区域由于所处大地构造单元不同,其新构造运动的表现形式也不同,它制约着区域地貌的发育,成土母质类型和地面气候状况,从而影响了该区域土壤的分布特征。     

Contribution of Pendant Ester Group Hydrolysis to the Erosion of Acrylic Polymers in Binders Aimed at Organotin-Free Antifouling Paints

Specific polymeric material applications as bioactive molecules delivery systems involve a strictly controlled degradation of polymer matrixes. One possibility to obtain a zero-order kinetic for small molecules release consists in a simple hydrolysis of ester groups contained in the macromolecular structure. The chemical degradation can lead to the continuous surface erosion of the formulated resins without loss of their mechanical properties and to a permanent activity of the delivery systems. Hydrolysis is a very well-known reaction in the case of organic molecules containing ester groups. The mechanism seems to be more complicated when ester groups are located in macromolecular structures. With the aim of antifouling applications, acrylic acid polymers bearing lateral ester groups of different chemical structures (hydrophilic, hydrophobic, hydrolyzable) have been prepared, characterized, and immersed in water, at pH 8, and their hydrolysis has been studied. Experimental data display two parameters, at least, which must be taken into account: the reactivity of the ester groups toward hydrolysis and the hydrophilic/hydrophobic balance of the polymer. The susceptibility of the acrylic polymers to hydrolysis has been compared to the erosion characteristics of the corresponding films. The results confirm that hydrolysis is necessary to obtain a regular degradation of the films without loss of mechanical properties. A relationship has been observed between the characteristics of hydrolysis and erosion for each studied polymer.     

Biodegradation of Injection Molded Starch-Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) Blends in a Natural Compost Environment

Injection molded specimens were prepared by blending poly (hydroxybutyrate-co-valerate) (PHBV) with cornstarch. Blended formulations incorporated 30% or 50% starch in the presence or absence of poly-(ethylene oxide) (PEO), which enhances the adherence of starch granules to PHBV. These formulations were evaluated for their biodegradability in natural compost by measuring changes in physical and chemical properties over a period of 125 days. The degradation of plastic material, as evidenced by weight loss and deterioration in tensile properties, correlated with the amount of starch present in the blends (neat PHBV < 30% starch < 50% starch). Incorporation of PEO into starch-PHBV blends had little or no effect on the rate of weight loss. Starch in blends degraded faster than PHBV and it accelerated PHBV degradation. Also, PHBV did not retard starch degradation. After 125 days of exposure to compost, neat PHBV lost 7% of its weight (0.056% weight loss/day), while the PHBV component of a 50% starch blend lost 41% of its weight (0.328% weight loss/day). PHB and PHV moieties within the copolymer degraded at similar rates, regardless of the presence of starch, as determined by ¹H-NMR spectroscopy. GPC analyses revealed that, while the number average molecular weight (Mn) of PHBV in all exposed samples decreased, there was no significant difference in this decrease between neat PHBV as opposed to PHBV blended with starch. SEM showed homogeneously distributed starch granules embedded in a PHBV matrix, typical of a filler material. Starch granules were rapidly depleted during exposure to compost, increasing the surface area of the PHBV matrix.     

Review of studies on environmental impacts of recreation and tourism in Australia

The paper provides a review of available information on the impact of recreation and tourism on environments, particularly on vegetation and soil, in Australia, with an emphasis on forests. Efforts have been made to compare the current research and development situation in Australia with some overseas countries such as the United States and the United Kingdom. While many documents reveal that Australia has been experiencing an increasingly high level of recreation and tourism use in its environments, only limited studies of environmental impacts of recreation and tourism have been published. Compared with other developed countries, particularly the United Kingdom and the United States, Australia lags behind in undertaking research in this area. The results of these limited studies and some observations indicate that the most common recreational and tourist activities (such as bush walking, camping, horse-riding) can, if not well managed, adversely affect the values of Australian natural and semi-natural resources. Overall, they can affect the vegetation and other recreational sites physically and biologically. Physical effects include track formation, soil loss and/or compaction and an increase in fire frequency. Littering and water pollution are also seen as impacts associated with bush walking and camping. Biological effects include causing damage to vegetation, increasing risk of myrtle wilt disease and the spread of the soil pathogen,Phytophthora cinnamomi, as well as assisting weed dispersal. Based on the information reviewed, the authors suggest the following areas as priorities for future research into the environmental impact of recreation and tourism in Australia: determine the type of natural features that attract recreation use; determine the quantitative relationship between the impact and the level of recreation and tourism use for different activities within major vegetation habitats; ascertain site carrying capacity or environment thresholds for major vegetation habitats and recreation activities; and determine the impacts of recreation and tourism for major regions and major vegetation habitats where there have been considerable nature-based recreation and tourism activities.1998 Academic Press     

几种螯合剂对污染土壤的重金属提取效率的研究

在Cd,Pb污染的土壤上,采用批提取实验(batchexperiment),研究了几种螯合剂和不同的水土比对重金属提取效率的影响。结果表明:螯合剂对Cd的提取效率随着各淋洗剂浓度的提高而逐渐提高,相同浓度下各淋洗剂的提取效率大小顺序依次为EDTA>DTPA>NTA>PA>CA>CD>HCl。随水土比提高,相应的提取效率也提高。几种淋洗剂中只有EDTA对Pb和Cd都能达到理想的淋洗效果。