Temporal trends and sources of PCDD/Fs, pentachlorophenol and chlornitrofen in paddy field soils along the Yoneshiro River basin, Japan

In order to understand the long-term behaviors of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), pentachlorophenol (PCP), and 2,4,6-trichlorophenyl-4′-nitrophenyl ether (chlornitrofen, CNP) in paddy soil, we measured their concentrations in paddy soil samples collected in 1982 and 1984 (1980s) and in 2000 and 2002 (2000s) from the Yoneshiro River basin, Japan. The concentrations of PCP and CNP decreased from the 1980s to the 2000s, whereas the concentrations of PCDD/Fs and their toxic equivalency (WHO2006-TEQ) remained. The major sources of PCDD/Fs in the paddy soil samples were attributed to impurities in PCP and CNP as a result of comparisons of homologue and congener profiles and principal component analysis. Based on the results of comparison of total input and remaining amount, it is estimated that more than 99% of PCP and CNP applied to the paddy fields had disappeared, whereas most of the applied PCDD/Fs and TEQ remained.     

Effect of microbial activity, soil water content and added copper on the temporal distribution patterns of HCB and DDT among different soil organic matter fractions

Temporal changes in the distribution of exogenous HCB and DDT among different soil organic matter fractions were studied under sterile and non-sterile conditions, different soil water contents, and different concentrations of added Cu(2+). The residence time was 311days. Soil organic matter was fractionated into fulvic acid (FA), humic acid (HA), bound-humic acid (BHA), lipid, and insoluble residue (IR) fractions by a methyl isobutyl ketone (MIBK) method. Results revealed that there is a mass transfer tendency of DDT and HCB from FA, HA and BHA to IR and lipid fractions with increasing residence time. Microbial activity accelerated the mass transfer, while the addition of Cu(2+) slowed it down. The HCB and DDT transfer rate decreased as the soil moisture increased from 1.9% to 60%, but increased when soil moisture increased further to 90%. A two-compartment first order kinetic model was used to describe the mass transfer from FA, HA and BHA.     

Mobility of metals and metalloids in a multi-element contaminated soil 20 years after cessation of the pollution source activity

Knowledge of trace element concentrations and mobility is important in the ecotoxicological assessment of contaminated soils. We analysed soil pore water under field conditions to provide new insights into the mobility of residual contaminants in the surface 50cm of a highly contaminated woodland soil. Cadmium and Zn were highly mobile in the acidic soil, concentrations increasing with depth in soil pore water, showing considerable downward mobility. High levels of surface organic matter restricted the solubility of Cu, Pb and Sb, with highest concentrations being found close to the surface. Dissolved organic carbon in pore water had a strong influence on mobility of Cu, Zn, Pb and Sb. Elevated As had moved from the organic surface horizons but was largely immobilised in deeper layers and associated with Fe and Al oxides. The measured differential mobility of pollutants in the present study is highly relevant to protection of groundwater and other receptors.     

Levels and temporal trends (1983-2003) of persistent organic pollutants (POPs) and mercury (Hg) in seabird eggs from Northern Norway

The main objective of this study was to investigate possible temporal trends of persistent organic pollutants (POPs) and mercury in eggs of herring gulls (Larus argentatus), black-legged kittiwakes (Rissa tridactyla), common guillemots (Uria aalge) and Atlantic puffins (Fratercula arctica) in Northern Norway. Eggs were collected in 1983, 1993 and 2003. Egg concentrations of POPs (PCB congeners IUPAC numbers: CB-28, 74, 66, 101, 99, 110, 149, 118, 153, 105, 141, 138, 187, 128, 156, 157, 180, 170, 194, 206, HCB, alpha-HCH, beta-HCH, gamma-HCH, oxychlordane, trans-chlordane, cis-chlordane, trans-nonachlor, cis-nonachlor, p,p'-DDE, o,p'-DDD, p,p'-DDD, o,p'-DDT and p,p'-DDT) and mercury were quantified. Generally, POP levels decreased between 1983 and 2003 in all species. No significant temporal trend in mercury levels was found between 1983 and 2003.     

福建省土地利用多尺度空间自相关分析

常规统计方法是分析制约土地利用空间分布的影响因素常用方法,其理论假设前提是数据本身在统计上是独立的,呈正态分布。而土地利用空间数据往往具有一定的空间自相关性,同时空间自相关性中蕴含一些有用的信息,必须采用合适的方法予以解决。论文以福建省作为研究区域,采用Moran's I系数的自相关图来表示土地利用及其影响因子的空间自相关性特征,并且在此基础上建立了土地利用与影响因子的空间自回归方程。研究结果表明,研究区域内土地利用与影响因子普遍存在空间自相关性,并且空间自相关性与研究尺度密切相关,空间自相关性随尺度增大而增强。空间自回归模型的解释能力比经典统计回归模型略强,并且空间自回归模型中的残差较小、空间模式不明显,而经典回归模型的残差比较大,并且具有显著的空间分布模式。     

基于空间自相关的安徽省市域发展空间格局研究

选取具有一定跨度的典型年份人均GDP统计数据,采用空间自相关方法分析了安徽省市级单元的经济发展分布空间特征和规律。结果表明,全省Moran’s I指数为0.11,经济上存在较弱的正空间自相关,经济发展呈多种类型,市域间有差异,呈现局部经济区化的雏形。根据人均GDP指标,结合空间自相关系数,将安徽省市域经济发展模式分为5类:集聚发展型、极核发展型、集中贫困型、贫困核型、一般发展型,并对其成因进行了分析。     

长株潭城市群PM2.5和O3浓度时空分布特征及影响因素分析

基于2015~2019年长株潭城市群PM_2.5和O₃遥感浓度数据,利用空间自相关指数和地理加权回归（GWR）等方法探究PM_2.5和O₃浓度的时空分布特征及相关因素对其影响强度.结果表明：① PM_2.5浓度整体呈现出冬季和春季高,夏季和秋季低的"U"型特征,而O₃浓度则表现为夏季和秋季高,冬季和春季低的"M"型特征,PM_2.5与O₃年均浓度高低排序为：长沙市>湘潭市>株洲市.② PM_2.5与O₃浓度在夏季呈现正相关,秋冬季为负相关,且具有显著的空间集聚特征,O₃浓度高-高集聚区的面积呈现逐年增加的趋势.③GWR结果显示：夜间灯光强度和人口密度都对PM_2.5与O₃具有正相关效应,其中,植被指数（NDVI）、风速和温度对PM_2.5浓度的影响最为显著,而风速和温度对O₃影响强度更为突出,不同因素对PM_2.5和O₃浓度影响具有显著的空间异质性.     

Spatial and temporal distribution of Mo in the overlying water of a reservoir downstream from mining area

This study aimed to evaluate the spatial and temporal variations of molybdenum (Mo) in the downstream water body of a Mo mine during three hydrologic periods (wet, dry and medium seasons). The physical properties in Luhun Reservoir reflected seasonal variations in different hydrological periods. The redox potential (ORP) and dissolved oxygen (DO) increased in the dry season. The concomitant decrease in temperature (T), conductivity (COND) and total dissolved solids (TDS) were lowest in the wet season. The pH value did not change significantly during the three hydrologic periods. The distribution of Mo in the dry season was high in upstream and low in downstream areas, which was significantly different from that of the wet and medium seasons. The total Mo concentration in wet (150.1 µg/L) and medium season (148.2 µg/L) was higher than that in the dry season, but the TDS (288.3 mg/L) and the percentage dissolved Mo (81.3%) in overlying water was lowest in the wet season. There was no significant relationship between the dissolved Mo and the total Mo with TDS. In the dry season, the mean total Mo concentration was 116.3 µg/L, which was higher than the standard limit value (70 µg/L) for drinking water (US EPA-United States Environmental Protection Agency recommended value 40 µg/L). Non-point source pollution is the main characteristic of mining area pollution, which was closely related to rainfall. Thus, the Luhun Reservoir contains substantial Mo pollution, which was a significant concern given that it is used as a source of drinking and irrigation water.     

Effects of colony food shortage on behavioral development in honey bees

Three experiments were conducted to explore the effects of severe food shortage on the control of two important and interrelated aspects of temporal division of labor in colonies of the honey bee (Apis mellifera): the size and age distribution of a colony's foraging force. The experiments were conducted with single-cohort colonies, composed entirely of young bees, allowing us to quickly distinguish the development of new (precocious) foragers from increases in activity of bees already competent to forage. In experiment 1, colony food shortage caused an acceleration of behavioral development; a significantly greater proportion of bees from starved colonies than from fed colonies became precocious foragers, and at significantly younger ages. Temporal aspects of this starvation effect were further explored in experiment 2 by feeding colonies that we initially starved, and starving colonies that we initially fed. There was a significant decrease in the number of new foragers in starved colonies that were fed, detected 1 day after feeding. There also was a significant increase in the number of new foragers in fed colonies that were starved, but only after a 2-day lag. These results suggest that colony nutritional status does affect long-term behavioral development, rather than only modulate the activity of bees already competent to forage. In experiment 3, we uncoupled the nutritional status of a colony from that of the individual colony members. The behavior of fed individuals in starved colonies was indistinguishable from that of bees in fed colonies, but significantly different from that of bees in starved colonies, in terms of both the number and age distribution of foragers. These results demonstrate that effects of starvation on temporal polyethism are not mediated by the most obvious possible worker-nest interaction: a direct interaction with colony food stores. This is consistent with previous findings suggesting the importance of worker-worker interactions in the regulation of temporal polyethism in honey bees as well as other social insects. Received: 17 April 1997 / Accepted after revision: 26 December 1997     

Timekeeping in the honey bee colony: integration of circadian rhythms and division of labor

The daily patterns of task performance in honey bee colonies during behavioral development were studied to determine the role of circadian rhythmicity in age-related division of labor. Although it is well known that foragers exhibit robust circadian patterns of activity in both field and laboratory settings, we report that many in-hive tasks are not allocated according to a daily rhythm but rather are performed 24 h per day. Around-the-clock activity at the colony level is accomplished through the performance of some tasks by individual workers randomly with respect to time of day. Bees are initially arrhythmic with respect to task performance but develop diel rhythmicity, by increasing the occurrence of inactivity at night, prior to becoming foragers. There are genotypic differences for age at onset of rhythmicity and our results suggest that these differences are correlated with genotypic variation in rate of behavioral development: genotypes of bees that progressed through the age polyethism schedule faster also acquired behavioral rhythmicity at an earlier age. The ontogeny of circadian rhythmicity in honey bee workers ensures that essential in-hive behaviors are performed around the clock but also allows the circadian clock to be engaged before the onset of foraging. Received: 6 October 1997 / Accepted after revision: 28 March 1998