基于便携式X射线荧光光谱速测的设施菜地土壤重金属污染诊断与评价

土壤重金属污染快速诊断与评价是污染防控与风险管理的前提。以广东省典型设施蔬菜产地土壤为研究对象，采用便携式X射线荧光光谱法(portable X-ray fluorescence spectroscopy, PXRF)原位快速获取土壤重金属（镉（Cd）、铜（Cu）、铬（Cr）、铅（Pb）、锌（Zn）、砷（As）、镍（Ni）及汞（Hg））含量，在传统实验室方法验证PXRF的准确性和稳定性的基础上，对广东省设施菜地表层土壤重金属的污染状况进行快速诊断，并对土壤重金属污染风险进行评价。结果表明：(1) 异位PXRF法对土壤Cd、Cu、Cr、Pb、Zn、As及Ni的测定值与传统实验室方法测定值极显著相关(P<0.01)，土壤Pb和As含量的PXRF原位测定值与传统实验室方法测定值极显著相关(P<0.01)；(2) 土壤含水量为150 g?kg-1~200 g?kg-1时，Cr、Pb、Zn和As的PXRF原位测定值与实验室测定值的相关性达到了极显著水平(P<0.01)；(3) 土壤Cd和Cu的超标现象较为突出，其点位超标率分别为20.9%和10.0%。设施菜地土壤Cd的平均含量为0.21 mg?kg-1，约为露天农田土壤的1.2倍。珠江三角洲地区设施土壤中各重金属的含量整体较其他地区高；(4) 土壤Cd、Cu、Cr、Pb、Zn、As、Ni及Hg的单项污染指数均小于1，由高到低依次为Cd>Cu>Pb>Zn>Cr>As>Ni>Hg，内梅罗综合污染指数的均值为0.69。就整体平均值而言，土壤重金属污染程度处于清洁水平。PXRF实现了广东省设施菜地土壤重金属污染的快速诊断，并快速识别出Cd和Cu为设施菜地污染风险较高的潜在污染元素，研究结果可为设施农业土壤重金属污染快速诊断与评价提供方法和数据支撑。     

便携式X射线荧光光谱法(PXRF)在矿区农田土壤 重金属快速检测中的应用研究

针对我国普遍存在的土壤重金属污染问题,迫切需要开展土壤重金属的快速检测与评价方法研究。本文采用便携式X射线荧光光谱法(PXRF)和传统实验室方法对云南会泽铅锌矿区农田土壤As、Pb、Cu和Zn进行测定,分析了PXRF法的应用效果。结果表明:1PXRF法测定的精密度与准确度满足我国农田土壤环境质量检测技术规范中规定的仪器检测要求;2土壤As、Pb、Cu和Zn的PXRF法测定值与传统实验室测定值具有良好的一致性,Pb、Cu和Zn的决定性系数均大于0.70;3基于PXRF法原位测定、PXRF法异位测定和传统实验室测定结果的研究区土壤As、Pb、Cu和Zn具有相似的空间分布规律。可见,PXRF法可用于矿区周边农田土壤As、Pb、Cu和Zn的快速检测、污染筛查与评价。     

北京顺义区土壤重金属分布与环境质量评价

在北京顺义区采集了412份土壤表层样品,分析了其中7种重金属元素（Cu、Zn、Cr、Pb、Cd、As和Hg）的全量,采用单因子指数和内梅罗指数对土壤环境质量进行评价。结果表明,土样中As、Cd、Cr、Hg、Cu、Pb和Zn含量平均值分别为7.85、0.136、61.47、0.073、22.43、20.38mg.kg-1和69.75mg.kg-1,As、Cd、Cr、Cu和Zn含量平均值超过了北京地区环境背景值,但所有元素含量的平均值均未超出土壤环境质量一级标准。土壤中各重金属元素含量Shapiro-Wilk检验和相关性检验结果表明,研究区土壤中重金属Cr呈正态分布,Cd、Cr、Cu、Pb元素与As元素相关性显著。土壤各元素单因子污染指数排序为Zn〉Cr〉Cd〉Cu〉Pb〉As〉Hg,内梅罗综合污染指数平均值为0.745,达到了土壤环境质量评价分级标准Ⅱ级,污染等级为＂警戒线＂级;菜地、果园、荒地、林地、苗圃、设施农业用地和水浇地的土壤内梅罗指数分别为0.809、0.765、0.720、0.669、0.781、0.786和0.729,表现为菜地〉设施农业〉苗圃〉果园〉水浇地〉荒地〉林地。土壤环境质量总体安全,部分地区土壤重金属污染处于警戒水平。     

便携式X射线荧光光谱法(PXRF)在肥料重金属快速检测中的应用

为了探讨一种简单快捷的肥料重金属含量测定方法,本文采用便携式X射线荧光光谱仪(PXRF)测定了我国典型设施农业生产区肥料中As、Pb、Cu、Zn和Cr的含量,并与常规实验室方法的测定值进行比较,以验证PXRF法测定结果的准确性。结果表明:①PXRF对土壤标准物质中As、Pb、Cu、Zn的测定值与标准值之间的相对标准偏差和相对误差均小于10%,表明该仪器测定As、Pb、Cu、Zn的精密度和准确度较好;②肥料中重金属PXRF法测定的检出限均低于相应的国家或行业标准。当含量超过检出限时,有机肥和无机肥中As、Pb、Cu、Zn和Cr常规实验室方法测定值与PXRF法测定值间均达到了极显著相关,R2在0.70～0.99;③PXRF法的检测成本仅为常规仪器的10%?20%,节省了前处理的时间和费用。因此,PXRF法可用于肥料中重金属含量的快速检测与评价。     

太原市污灌区土壤重金属污染现状评价

对太原市污灌区土壤重金属分布特征进行了分析评价,结果表明重金属Pb、Zn、Cu、Ni、Mn、Cr、As、Hg、Cd含量均值均未超过土壤环境质量标准（GB15618—1995）,但其平均值均显著高于太原市土壤背景值。各重金属间的相关分析表明,Pb、Zn、Cu、Ni、Mn、Cr、As、Cd之间呈极显著相关,说明这8种元素污染源可能相同。Hg是本区表层土壤重金属污染的主要因子,重金属元素的污染程度依次为Hg〉Cd〉Pb〉As〉Cu〉Zn〉Cr〉Mn〉Ni。土壤重金属单项污染指数均值均大于1,综合污染指数为2.81,总体上,污染水平为中度及其以上。各种重金属单因子污染指数和综合指数在研究区有相似的空间分布格局,总体分布趋势为东南部小店地区和中南部晋源区相对较高,南部清徐县相对较小;通过因子分析并结合污灌区污染源调查,表明Hg除受污水灌溉的影响外,燃煤释放的Hg可能是重要来源之一,Cd、Zn、Pb和Cu可能来自污水灌溉和大气沉降,以污水灌溉的贡献为主,Ni、Mn、As、Cr来自污水灌溉。Hg、Cd是太原市污灌区土壤中需要优先控制的重金属。     

海南省农产品重金属污染评价与特征分析

采用单项与综合污染指数法,以海南省农产品为研究对象,开展了农产品中重金属Cu、Zn、Pb、Cd、Ni、As、Cr和Hg含量的抽样调查分析与评价。结果表明,全省农产品中重金属的平均含量均低于食品中规定的限值,各重金属的单项与综合污染指数均≤1,综合污染指数为0.57;全省农产品未受重金属污染,属于安全水平,适宜发展无公害农产品。同时发现,个别监测点的农产品中重金属含量有超标现象,新鲜水果中个别样品Pb、Cd、Hg超标,超标率在2.17%～10.87%之间;豆类蔬菜中个别样品Ni超标,超标率为9.09%;瓜果类蔬菜中个别样品Pb、Cd超标,超标率为12.24%～24.49%;叶菜蔬菜中个别样品Pb超标,超标率为6.67%;谷物中个别样品Pb、Cd、As超标,超标率在2.11%～7.37%之间。农产品中重金属含量间多呈正相关,其中Zn与Ni、As与Hg之间差异达到极显著水平,Cu与Zn、Cu与As、Cu与Hg、Zn与As、Zn与Hg、Cd与As、Cd与Cr、Cd与Hg、Ni与As、Ni与Hg、As与Cr之间差异达到显著水平。结合主成分分析结果,推测Cu、Zn、Ni、As、Hg含量主要受农业生产和人类活动的影响,而Cr、Pb和Cd含量受土壤母质的影响比较大。     

新乡市大棚菜田土壤重金属积累特征及污染评价

采用微波消解-ICP-AES技术,测定不同种植年限大棚菜田土壤样品中As、Pb、Zn、Cd、Cr、Mn、Ni、Cu等重金属的含量,研究不同种植年限与大棚菜田土壤重金属累积的相关性以及大棚菜田土壤重金属累积特征,并利用地积累指数法进行污染评价。结果表明:大棚菜田土壤重金属Zn、Pb、Ni、Mn和Cu的含量与种植年限具有极显著相关性;大棚菜田土壤中重金属Cd和Cr的含量与种植年限不相关。重金属元素间相关性分析表明,Zn与Pb、Cd、Ni、Mn、Cr、Cu,Pb与Cd、Ni、Mn、Cr、Cu,Cd与Ni、Mn、Cr,Ni与Mn、Cr、Cu,Mn与Cr、Cu具有污染同源性,Cu与Cd、Cr不具有污染同源性。地积累指数法污染评价结果显示Cd的污染等级达到了6级,已构成了极严重污染;Zn和Cu的污染等级达到2级,已构成了中度污染;Pb、Mn的污染等级达到1级,已经构成了轻~中度污染;As、Ni、Cr均未构成污染。     

渝黔高速公路綦江段两侧农地土壤重金属空间分布特征研究

选择渝黔高速公路綦江段沿线,设置6个农地区域进行土壤重金属(As、Cd、Cr、Cu、Hg、Ni、Pb、Zn)监测,并进行空间特征分析。结果表明:渝黔高速公路綦江段邻域土壤表层As、Cd、Cr、Cu、Hg、Ni、Pb、Zn含量平均值分别为3.40,0.24,59.37,21.81,0.064,25.41,24.75,68.81mg·kg-1;水平方向上,土壤随着高速公路的外延,As、Cr、Ni、Zn含量整体呈下降趋势,Hg则反之,Cd、Cu、Pb相对稳定;垂直方向上,重金属含量随深度增加而降低,即表土层心土层底土层;以表层土为基础,可以确定项目区实际安全种植距离为远离高速公路150 m左右。土壤样品Cd部分超标,超标率为17.65%。     

工业区周边农田重金属污染评价及来源分析

以新疆北疆某工业区周边农田土壤为研究对象,采集0~20 cm土壤样品254个,测定了Cr、Ni、Cu、Zn、As、Hg、Pb、Cd共8种重金属含量。运用相关性分析和主成分分析探讨工业区周边农田土壤重金属的来源,运用GS+进行数据拟合,选取最佳模型,再进行克里格插值分析重金属的空间分布格局。结果表明,Cr、Ni、Cu、Zn、As、Hg、Pb和Cd的含量分别为45.00、28.53、55.66、73.57、13.39、2.17、15.38和0.50 mg kg~(-1)。测量的金属除Cr之外均超过土壤的背景值,只有Hg处于中度污染,其余元素都处于非污染,而研究区综合潜在生态风险程度为严重型。重金属空间分布表明,Ni、Zn、As、Hg和Pb在东部和南部含量较高。来源分析表明,Hg来源受研究区内工业活动的影响;Cr、Ni、Zn和Cd主要来自于化肥、农药和地膜等农业活动和土壤母质的共同作用;As、Hg和Pb主要来源是受研究区内工业活动的影响。     

龙游硫铁矿区农田土壤重金属污染的空间 变异及在水稻中的积累

为了解浙江龙游硫铁矿区农田重金属污染状况,采集矿区265件农田土壤样品,分析8种重金属Cu、As、Hg、Zn、Cd、Ni、Pb、Cr元素全量,利用地统计学软件GS+9.0对研究区土壤各元素指标进行半变异函数拟合,并利用普通克里格法进行插值并绘制空间分布图。采集30件水稻籽粒样品,分析重金属在研究区中水稻籽粒的累积特征,并进行了健康风险评价。结果表明:矿区土壤中8种重金属元素的变异系数从0.72到1.76,离散程度较高。8种重金属的土壤空间半变异函数Cu、As、Hg元素符合指数模型,Zn、Cd、Ni、Pb符合球状模型,Cr符合高斯模型。元素Cu、Pb、Zn、Cr、Ni的块金值与基台值的比值C0/C0+C都小于0.25,说明空间变化主要受地质背景等因素影响;元素Cd、Hg和As的块金值与基台值的比值C0/C0+C在0.25~0.75之间,说明除了地质背景因素,人为活动等随机因素也有影响。矿区水稻籽粒中重金属Ni和Cd的变异系数最高,分别为0.95和0.87,说明Ni和Cd元素可能存在异常积累。矿区水稻籽粒对重金属的富集能力由大到小依次为Cd、Zn、Cu、Ni、As、Hg、Cr、Pb。健康风险评价结果表明矿区农田水稻籽粒中元素As、Cd的风险商大于1,存在潜在健康风险;而其他6种重金属Cu、Hg、Zn、Ni、Pb和Cr基本属于安全范围。     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.     

Karyotypic and genome size variation in Cajanus cajan (L.) Millsp. (pigeonpea) and some wild relatives

Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.     

Effect of some fungicide seed treatments on the survival of Bradyrhizobium japonicum and on the nodulation and yield of soybean [Glycine max. (L) Merr.]

Several commercial fungicide seed treatments were evaluated for their possible effect on the survival of Bradyrhizobium japonicum on seeds and on the nodulation and yield of soybeans in a greenhouse and a field experiment. quinolate Pro (carbendazim and oxine copper), Vitavax 200FF (carboxin and thiram), and Monceren (pencycuron) had a small effect or no effect on the survival of B. japonicum and on the nodulation and yield of soybeans. They can thus be considered compatible with soybean seed inoculation. Germipro UFB (carbendazim and iprodione), Apron 35J (metalaxyl), and Tachigaren (hymexazol) decreased B. japonicum survival and the nodulation and yield of soybeans and thus cannot be considered compatible with soybean seed inoculation.     

Einfluss der düngungsmethoden auf die entwicklung von zuckerrübenkrankheiten

Während neunjähriger (1994-2002) Untersuchungen in der Versuchsanstalt Ba?cyny (Fahlerde, Fall-Gleyboden, ausgebildet aus leichtem Lehmboden) wurde der Befall mit Krankheiten an der Zuckerrübe in Abhängigkeit von der Düngungsmethode bewertet. Folgende Methoden wurden angewendet: A - Mineraldünger, B - Stalldung und Mineraldünger, C - Stroh-, Gründung und Mineraldünger, D - Kompostdünger und Biopräparate (ökologische Düngung). Auf den Objekten A, B, C wurden bei konstanter Phosphor-Kalium-Düngung die Stickstoffgaben von 0 bis 180 kg.ha^?1 differenziert. Auf dem ökologischen Objekt D ohne Mineraldünger wurden statt Stickstoff die Biopräparate P₅₀₀ und P₅₀₁ verabreicht. Der geringste Befall von Krankheiten wurde an der Zuckerrübe auf jenem Objekt festgestellt, das mit Kompost und den Biopräparaten gedüngt worden war. Im Rahmen der konventionellen Düngungsmethoden wurde allgemein die höchste Intensität der Krankheiten an der mit Stroh, Gründung und Mineraldünger gedüngten Zuckerrübe beobachtet. Ausnahmen von dieser Regel bildete das Vorkommen von echtem Mehltau und Keimlingsfäule. Auf den Objekten A, B, C nahm die Intensität der Krankheiten mit der Steigerung der Stickstoffgabe zu. Auch die auf Objekt D verabreichten Biopräparate stimulierten die Entwicklung der Krankheiten. The effect of various fertilization methods on the diseases of sugar beet was estimated on the basis of nine-year studies (1994-2002) conducted in the Experimental Production Farm in Ba?cyny on loess-based, sedimentary-gley, light-clay soil. The following fertilization methods were applied: A - mineral fertilization, B - mineral and manure fertilization, C - straw, green manure and mineral fertilization, D - ecological compost and biodynamic preparations fertilization. In the objects A, B and C fertilized with phosphorus and potassium, various doses of nitrogen ranging from 0 to 180 kg/ha^?1 were used. In the ecological object D, where mineral fertilization was not used, biodynamic preparations P₅₀₀ and P₅₀₁ were applied instead of nitrogen. The lowest ratio of the diseases of sugar beet was observed in the object fertilized with the compost and biodynamic preparations. In view of the conventional fertilization methods, generally the highest incidence of diseases was noted in the sugar beet fertilized with straw, green manure and mineral fertilizers. The exception was the occurrence of powdery mildew and the black leg. In objects A, B and C the incidence of the diseases increased with the increase in nitrogen doses. The applied biodynamical preparations in the object D stimulated the development of diseases too.     

Prospects for control of Pythium damping-off of lettuce with Trichoderma,Gliocladium and Enterobacter spp.

Summary Damping-off of lettuce (Lactuca sativa) caused by Pythium ultimum was studied in pots containing a non-sterile potting mix in the glasshouse. Fifty P. ultimum sporangia g^-1 compost reduced the plant stand to 15% and shoot dry weight to 18%, but this reduction was totally prevented by applying Trichoderma harzianum at 2×10⁵ viable propagules g^-1 potting mix. Gliocladium virens and Enterobacter cloacae also alleviated the damping-off. E. cloacae did not adversely affect the action of the fungal antagonists. The co-existence of the bacterial and fungal antagonists was revealed on the root surface and inner surface of the testa by scanning electron microscopy, indicating the compatibility of the biocontrol agents.     

细菌、真菌及植物氮营养信号研究进展

氮素吸收代谢是所有生物生命活动的核心部分,因此,各种生物对氮的吸收与同化过程都有精细的调节。这种调节依赖于生物对体内氮素状况信号及体外（生长介质中）氮素信号的感受。过去几十年中,在细菌、真菌中已经对氮素营养信号有了较好的研究,而植物中则相对缓慢,但也有了一定的认识。本文重点比较细菌、真菌及植物中氮信号系统的组成,以期为进一步认识植物中的氮信号接受与转导系统提供启示。     

Aircraft operations near concentrations of birds in Antarctica: The development of practical guidelines

Aircraft operations have the potential to disturb and to impact negatively on bird life. A gradient of increasing behavioural response is evident in birds when exposed to increasing aircraft stimulus. The most major disturbance is likely to lead to impacts on the health, breeding performance and survival of individual birds, and perhaps bird colonies. A process of revision to policies on aircraft operations contained in management plans for a number of specially protected areas in Antarctica by the United Kingdom, accompanied by consultations made within the scientific community through the Scientific Committee on Antarctic Research (SCAR) and with operational interests through the Council of Managers of National Antarctic Programmes (COMNAP) resulted in new guidelines being adopted by the Antarctic Treaty Consultative Parties in June 2004. The principal recommendations of the guidelines are that bird colonies should not be overflown below 2000 ft (∼610 m) above ground level and landings within 1/2 nautical mile (∼930 m) of bird colonies should be avoided wherever possible. These guidelines are less stringent and less specific than those that were recommended by the SCAR specialist group on birds, and represent a compromise to accommodate operational needs. While the adoption of clear and consistent guidelines for the operation of aircraft in Antarctica is welcome in that this provides practical advice that is likely to reduce incidences of close aircraft/bird encounters, there remains insufficient knowledge of the interactions between aircraft and birds in Antarctica, and the consequent impacts on individual birds and on bird populations. It is important, therefore, that the guidelines adopted are considered interim, and should be kept under scrutiny with revisions made as new and improved research results appear.     

The abundance of heterocystous blue-green algae in rice soils and inocula used for application in rice fields

Summary Algal populations were quantified (as colony-forming units [CFU] per square centimetre) in 102 samples of rice soils from the Philippines, India, Malaysia and Portugal, and in 22 samples of soil-based inocula from four countries. Heterocystous blue-green algae (BGA) were present in all samples. Nostoc was the dominant genus in most samples, followed by Anabaena and Calothrix. In soils, heterocystous BGA occurred at densities ranging from 1.0 × 10² to 8.0 × 10⁶ CFU/cm² (median 6.4 × 10⁴) and comprised, on average, 9% of the total CFU of algae. Their abundance was positively correlated with the pH and the available P content of the soils. In soil-based inocula, heterocystous BGA occurred at densities ranging from 4.6 × 10⁴ to 2.8 × 10⁷ CFU/g dw (dry weight), comprising only a moderate fraction (average 13%) of the total algae. In most soils, the density of indigenous N₂-fixing BGA was usually higher than that attained by applying recommended rates of soil-based inoculum. Whereas research on the practical utilization of BGA has been mostly directed towards inoculation with foreign strains, our results suggest that attention should also be given to agricultural practices that enhance the growth of indigenous strains already adapted to local environmental conditions.Maître de Recherches ORSTOM (France), Visiting Scientist at IRRI