Occurrence, distribution, and ecological risk assessment of DDTs and heavy metals in surface sediments from Lake Awassa—Ethiopian Rift Valley Lake

Dichlorodiphenyltrichloroethanes (DDTs) and heavy metals are ubiquitous contaminants with high bioaccumulation and persistence in the environment, which can have adverse effects on humans and animals. Although applications of DDTs have been banned in many countries, developing countries like Ethiopia are still using these for agricultural and medicinal purposes. In addition, heavy metals are naturally present in the aquatic environment and distributed globally. In this study, the occurrence, distribution, and ecological risk of DDTs and heavy metals in surface sediments from one of the Ethiopian rift valley lakes were studied. Twenty-five surface sediment samples from Lake Awassa, Ethiopia were collected and analyzed for DDTs and heavy metals. Results showed that concentrations of total DDTs ranged from 3.64 to 40.2 ng/g dry weight. High levels of DDTs were observed in the vicinity of inflow river side and coastal areas with agricultural activities. The heavy metals content were followed the order Zn?>?Ni?>?Pb?>?Cu?>?Cr?>?Co?>?As?>?Cd?>?Hg. Correlation analysis and principal components analysis demonstrated that heavy metals were originated from both natural and anthropogenic inputs. The levels of DDE and DDD in surface sediments exceeded the sediment quality guideline values, indicating that adverse effects may occur to the lake. A method based on toxic-response factor for heavy metals revealed that the calculated potential ecological risk indices showed low ecological risk for the water body.     

A quantitative risk assessment of waterborne infectious disease in the inundation area of a tropical monsoon region

Flooding and inundation are annual events that occur during the rainy season in Cambodia, and inundation has a strong relationship with human health. This study simulated the coliform bacteria distribution using a hydraulic model and estimated the impact of inundation on public health using a dose–response model. The model parameters were calibrated using field survey data from Cambodia and obtained good agreement with the coliform group count distribution. The results suggest that the impact of inundation on human health is most noticeable in residential areas. The annual average risk of infection during medium-sized flood events is 0.21. The risk due to groundwater use ranges from 0.12 to 0.17 in inundation areas and reaches as high as 0.23 outside the inundation areas. The risk attributed to groundwater use is therefore higher than that for surface water use (0.02–0.06), except in densely populated areas at the city center. There is a high risk for infection with waterborne disease in residential areas, and the annual average risk during small flood events is 0.94. An assessment of possible countermeasures to reduce the risk shows that the control of inundation may bring more risk to public health in Cambodia. Shallower inundation water (<0.3 m) leads to a higher risk of infection, but if the depth is greater than 2 m, the risk is low in residential areas. The simulated results explain the spatial distributions of infection risk,, which are vitally important for determining the highest priority places with relatively high risk and will be helpful for decision makers when considering the implementation of countermeasures.     

Accumulation of Hg and other heavy metals in the Javan mongoose (Herpestes javanicus) captured on Amamioshima Island, Japan

Concentrations of 22 elements (Mg, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Mo, Ag, Cd, Sb, Cs, Ba, Tl, total Hg (T-Hg), Pb) and organic Hg (O-Hg) were examined in the liver, kidney and brain of the Javan mongoose (Herpestes javanicus) and in liver of the Amami rabbit (Pentalagus furnessi) from Amamioshima Island in Japan. Relatively high levels of T-Hg levels (from 1.75 to 55.5 microg g-1 wet wt.) were found in the Javan mongoose. As for a comparison of hepatic T-Hg concentrations between the two areas, there was no significant difference between the Javan mongoose in Amamioshima and those in the Okinawa islands. In addition, T-Hg levels in the livers of the Amami rabbit were the same as in the livers of other herbivorous mammals. Taken together, it suggested that T-Hg accumulation in the livers of the Javan mongoose was not affected by the environment but by a specific physiological mechanism. The comparison of Hg and other heavy metal accumulations between terrestrial mammals (13 species, 61 individuals) including the Javan mongoose and marine mammals (18 species, 508 individuals) were also discussed.     

An intercalibration study on organobromine compounds: Results on polybrominated diphenylethers and related dioxin-like compounds

An intercalibration study on organobromine compounds has been conducted to evaluate the accuracy and reliability in the analysis of brominated flame retardants (BFRs) such as polybrominated diphenyl ethers (PBDEs) and their related compounds like polybrominated and monobromo-polychlorinated dibenzodioxins and -furans (PBDDs/DFs, MoBPCDDs/DFs). This paper reports the results for these compounds in 'Mixed Standard Solutions' and 'Air-Dried Sediment'. The relative standard deviations (RSDs) for PBDEs, PBDDs/DFs and MoBPCDDs/DFs in mixed standard solutions ranged from 9% to 24%, 4% to 20% and 8% to 27%, respectively. The results of this study are better than those reported in earlier international interlaboratory studies due to general improvement in analytical methods and an increasing number of available authentic standards, particularly for PBDEs. In the analysis for higher brominated compounds such as octabromodibenzodioxin, the participants were advised to optimize the calibration curves befitting the range of concentrations found in samples because variation of relative response factors was noted. The results for 'Air-Dried Sediment' were also reasonable with RSDs from 10% to 38% for PBDEs, 8% to 38% for PBDDs/DFs and 17% to 36% for MoBPCDDs/DFs. In the sediment sample, possible errors in the sample pretreatment and/or interference by other compounds/impurities were indicated. The concentrations of pentabromodiphenylether, BDE100, varied more than the other PBDE isomers due to its poor separation in some chromatographic conditions. In addition, interference by PBDEs was observed in the analysis for PBDFs. Potential degradation/secondary formulation of PBDEs and PBDFs during the Soxhlet extraction were suggested when copper powder was added into the sediment samples. Inspite of these observations, the results in this study are better than those reported in other interlaboratory studies due to the advice given to participants for improving the results. Compared with the results for PCDDs/DFs (5-23% RSDs) and Co-PCBs (6-24% RSDs), the RSDs for most of the organobromine compounds were high, indicating an immature QA/QC approach for the analysis of PBDEs and related compounds in comparison to common chlorinated dioxins.     

Depth profiles of radiocarbon and carbon isotopic compositions of organic matter and CO2 in a forest soil

Depth profiles of the specific activities of (14)C and carbon isotopic compositions (Delta(14)C, delta(13)C) in soil organic matter and soil CO(2) in a Japanese larch forest were determined. For investigating the transport of CO(2) in soil, specific activities of (14)C, Delta(14)C and delta(13)C in the organic layer, and atmospheric CO(2) in the same forest area were also determined. The specific activity of (14)C and Delta(14)C in the soil organic matter decreased with the increase in depth of 0-60cm, while that of soil CO(2) did not vary greatly at a soil depth of 13-73cm and was more prevalent than that of atmospheric CO(2). Peaks of specific activities of (14)C appeared at the depth of 0-4cm and Delta(14)C values were positive in the depth range from 0 to 15cm. These results suggest that the present soil at a depth of 0-4cm had been produced from the mid-1950s up until 1963, and the bomb C had reached the depth of 15cm in the objective soil area. The delta(13)C in the soil organic matter increased at the depth of 0-55cm, while that of soil CO(2) collected on 8 November 2004 decreased rapidly at the depth of 0-13cm and only slightly at the depth of 53-73cm. By combining the Delta(14)C and delta(13)C of the respective components and using the Keeling plot approach it was made clear that the entering of atmospheric CO(2) showed a large contribution to soil CO(2) at the depth of 0-13cm and a negligible contribution at the depth of 53-73cm for soil air collected on 8 November 2004. Respiration of live roots was presumed to be the main source of soil CO(2) at the depth of 53-73cm on 8 November 2004.     

Asymptotic growth trajectories of larval sardine (Sardinops melanostictus ) in the coastal waters off western Japan

Growth trajectories of individual larvae of Japanese sardine, Sardinops melanostictus, caught in the coastal waters off western Japan were back-calculated from the first feeding stage up to date of capture (approximate size of 20 to 35 mm total length; TL) based on individually determined allometric relationships between otolith daily ring radii and fish total lengths. The larvae in January-, February-, and March-hatched cohorts in the coastal waters grew faster and more uniformly than those in the oceanic waters offshore of the Kuroshio current. Growth trajectories of the three hatch-month cohorts were similar and could be expressed by the Gompertz model. The inflection points of the growth curves were reached at 9 to 11 d after hatching, when larvae were 10.8 to 11.8 mm TL. Maximum growth rates at these points were 0.80 to 0.85 mm d⁻¹. Growth rates gradually declined after the inflection points, and larval TLs converged into the infinite length of 29 to 32 mm, the sizes at which metamorphosis from larvae to juveniles is initiated. This asymptotic growth pattern in the larval stage resulted in the narrow ranges in TLs in spite of the wide range of ages of the larvae caught by boat seiners in the coastal waters. Slow growth and therefore long duration of the metamorphosing stage could be influential in determining the cumulative total mortality in the early life stages of the Japanese sardine. Received: 14 July 1996 / Accepted: 20 August 1996     

Determination of gaseous semi- and low-volatile organic halogen compounds by barrier-discharge atomic emission spectrometry

A group parameter approach using "total organic halogen" is effective for monitoring gaseous organic halogen compounds, including fluorine, chlorine, and bromine compounds, generated from combustion. We described the use of barrier-discharge radiofrequency- helium-plasma/atomic emission spectrometry, for the detection of semi- and low-volatile organic halogen compounds (SLVOXs), which can be collected by Carbotrap TM adsorbents and analyzed using thermal desorption. The optimal carrier gas flow rates at the injection and desorption lines were established to be 100 mL/min. The detection range for SLVOXs in the gaseous samples was from 10 ng to tens of micrograms. Measuring F was more difficult than measuring Cl or Br, because the wavelength of F is close to that of air. The barrier- discharge radiofrequency-helium-plasma/atomic emission spectrometry measured from 85% to 103% of the SLVOXs in the gas sample. It has been found that Carbotrap B is appropriate for high-boiling-point compounds, and Carbotrap C is suitable for the determination of organic halogen compounds with lower boiling points, in the range 200-230°C. Under optimal analysis conditions, a chlorine- containing plastic was destroyed using different oxygen concentrations. Lower oxygen concentrations resulted in the production of lower amounts of organic halogen compounds.     

Quantitative analysis of microbial biomass yield in aerobic bioreactor

We have studied the integrated model of reaction rate equations with thermal energy balance in aerobic bioreactor for food waste decomposition and showed that the integrated model has the capability both of monitoring microbial activity in real time and of analyzing biodegradation kinetics and thermal-hydrodynamic properties. On the other hand, concerning microbial metabolism, it was known that balancing catabolic reactions with anabolic reactions in terms of energy and electron flow provides stoichiometric metabolic reactions and enables the estimation of microbial biomass yield (stoichiometric reaction model). We have studied a method for estimating real-time microbial biomass yield in the bioreactor during food waste decomposition by combining the integrated model with the stoichiometric reaction model. As a result, it was found that the time course of microbial biomass yield in the bioreactor during decomposition can be evaluated using the operational data of the bioreactor (weight of input food waste and bed temperature) by the combined model. The combined model can be applied to manage a food waste decomposition not only for controlling system operation to keep microbial activity stable, but also for producing value-added products such as compost on optimum condition.     

Abstracts to forthcoming papers

Soil and sediments collected at a former chlor‐alkali plant in coastal Georgia (United States), revealed the presence of PCDF concentrations as great as 82.3 ng/g, dry wt. PCDF congener profile in soil was typical of “chlorine pattern”; with elevated proportions of OCDF and HpCDF. Concentrations of PCDFs declined gradually by 44‐fold at a distance of about 500 m along the contamination gradient. Of PCDDs/DFs, 2,3,7,8‐substituted PCDFs accounted for 94–98% of the TCDD‐like activity, which declined by 25‐fold, corresponding with the reduction of total PCDF concentrations. Concentrations of PCDDs in sediments were as great as 17 ng/g, with an elevated contribution from OCDD. The magnitude of decline in PCDD concentrations with distance from the source was less pronounced than that for PCDFs. PBDDs and PBDFs were not detected. Polybrominated biphenyl ether (PBBE) and monobromo‐heptachloro dibenzo‐p‐dioxins and dibenzofurans (PXDDs/DFs) were found, though, at low concentrations. Their spatial distribution was similar to those of PCDDs.     

Predicting leadership using nutrient requirements and dominance rank of group members

Group members must decide collectively when and where to go despite their different nutrient requirements. One mechanism underlying consensus decisions is the proposition by one individual to move. The individual frequently initiating movements is often named a “leader”, and this individual may be the most dominant, the oldest or may have the greatest physiological needs. However, high-ranking individuals are often those with the highest body mass, and thus the highest nutrient requirements. In this study, we use a state-dependent model to assess the importance of dominance and nutrient requirements to the initiation of group movements, testing different combinations of effects of these interacting factors. We first show using a theoretical approach that whatever the correlation between the dominance hierarchy and body mass, all decision-making systems are viable (or stable). However, in most cases, one individual does become the leader, and nutrient requirements appear to be more important for determining which individual will emerge as the leader than pre-existing individual characteristics such as their dominance rank. We obtained the same result when we compared the simulated distributions of initiations to the observed distributions in three macaque species. Results of our comparison of three macaque groups suggest that we can predict which group member will be the leader simply by knowing its body mass and its reproductive state. Understanding the link between dominance, needs and leadership may be a key to understanding consensus decisions and collective motion in animal groups, and might provide insight into the management of animal groups and their conservation.