Hydrophobicity of complex organic mixtures

Hydrophobicity is an important property in risk assessment of chemicals. A group parameter that reflects the hydrophobicity of technical mixtures is not yet available. However, many substances are complex organic mixtures, for which it is practically impossible to determine each component separately. An experimental procedure to measure the hydrophobicity of organic mixtures without knowledge of the individual components was developed and tested for a mixture of benzene and twelve chlorobenzenes. This procedure is based on separation of the mixture into fractions of increasing hydrophobicity by reversed-phase HPLC, after which the total molar concentration in each fraction is determined by vapour pressure osmometry. The obtained information on hydrophobicity can be used for assessing bioaccumulation and sediment sorption after emission of the mixture to water has occurred.     

Distribution and dynamics of larval populations of Anopheles messeae and A. atroparvus in the delta of the rivers Rhine and Meuse,The Netherlands

The distribution and ecology of mosquitoes of the Anopheles maculipennis complex were studied in the delta of the rivers Rhine and Meuse in the southwest of The Netherlands. The study area was previously malarious, with A. atroparvus being the only vector. 125 potential aquatic habitats of A. maculipennis were sampled, of which 47 (37.6%) contained larvae of this species complex. Larval densities varied from 7.4-325.93 larvae m-2. There was no correlation between chlorinity (@1000) of the water and presence and/or density of larvae. The presence of A. maculipennis was not associated with one particular aquatic floristic habitat, although larvae were often found together with floating algae (Enteromorpha spp.). Larvae were not found in areas experiencing tidal flooding. A newly developed PCR method was used for identification of the mosquito sibling species. Of 150 larvae examined, only 4 were identified as A. atroparvus. All other larvae examined were A. messeae. Adult mosquitoes were identified as A. messeae and 30 wild-caught mosquitoes had fed on domestic animals. Because most anophelines found in 1999 were A. messeae, it is concluded that the study area has undergone a dramatic ecological change since the previous anopheline investigations in 1935, causing the near extinction of A. atroparvus. This species was the only malaria vector in The Netherlands and therefore it is not expected that malaria can return to its former endemic status in the coastal areas of The Netherlands.     

影响瑞典最大湖泊中冰河时代残余体片脚类动物Monoporeia affinis (Lindstrom)数量波动的因素

在瑞典最大的三个湖泊中人们研究了影响冰河时代残余体片脚类动物Monoporeis affinis的长期(1982-000年)种群密度的因素.在所有的三个湖泊中,Monoporeia数量都有较大的波动,在维纳恩和拉伦湖中还出现了明显的密度峰值.在维纳恩湖中,片脚类动物的显示出在一年期间内它和春季最大硅藻的生物体积有非常重要的关系.韦特恩湖中硅藻生物体积和Monoporeia密度间没有这种关系可能是由于此湖泊较深及其营养浓度比较低.在富营养的梅拉伦湖中.夏季氧不足(＜4mgO2/L)可能是一个重要的调节因素.均温层的温度显示在1989～1994年间深湖水存在一个明显的温暖周期.维纳和韦特恩湖均温层温度和总的太阳照射有关.然而和北大西洋波动冬天指数有关的既不是均温层水温也不是硅藻的生物体积.我们推测温度和接近湖底的氧气浓度的变化通过作用于种群的补充幼体成功率(繁殖)和幼体(年轻的)存活率来对种群密度起负面影响.     

Anammox: an option for ammonium removal in bioreactor landfills

Experiments carried out in bioreactor landfill simulators demonstrated that more than 40% of the total N was transferred into the liquid and gas phases during the incubation period of 380 days. Ammonium, an end product of protein degradation and important parameter to consider during landfill closure, tends to accumulate up to inhibitory levels in the leachate of landfills especially in landfills with leachate recirculation. Most efforts to remove ammonium from leachate have been focused on ex situ and partial in situ methods such as nitrification, denitrification and chemical precipitation. Besides minimal contributions from other N-removal processes, Anammox (Anaerobic Ammonium Oxidation) bacteria were found to be active within the simulators. Anammox is considered to be an important contributor to remove N from the solid matrix. However, it was unclear how the necessary nitrite for Anammox metabolism was produced. Moreover, little is known about the nature of residual nitrogen in the waste mass and possible mechanisms to remove it. Intrusion of small quantities of O₂ is not only beneficial for the degradation process of municipal solid waste (MSW) in bioreactor landfills but also significant for the development of the Anammox bacteria that contributed to the removal of ammonium. Volatilisation and Anammox activity were the main N removal mechanisms in these pilot-scale simulators. The results of these experiments bring new insights on the behaviour, evolution and fate of nitrogen from solid waste and present the first evidence of the existence of Anammox activity in bioreactor landfill simulators.     

Evaluating Post-wildfire Vegetation Regeneration as a Response to Multiple Environmental Determinants

Vegetation regeneration in post-fire environments varies across the landscape of a burned area. Variations are caused by interacting factors, including soil properties, vegetation characteristics, hydrology, land management history, and burn severity. While many of these factors have been explored previously, few studies have investigated the combination of multiple factors. A time-series of the remotely sensed enhanced vegetation index data has been analyzed to estimate rates of regeneration across a burn in central Arizona. We used regression trees to evaluate post-fire vegetation response as a function of multiple factors. Regeneration was a function of elevation (likely a proxy for moisture availability), burn severity, pre-burn vegetation, and post-burn management activities. Both time-series vegetation data and regression trees were valuable tools for determining dominant interacting factors responsible for variations in post-fire regeneration. Evaluation of the time-series data and modeled post-fire vegetation permitted the interpretation of management actions across the burned area.     

A novel method to determine buffer strip effectiveness on deep soils

Unfertilized buffer strips (BS) generally improve surface water quality. High buffer strip effectiveness (BSE) has been reported for sloping shallow aquifers, but experimental data for plain landscapes with deeply permeable soils is lacking. We tested a novel method to determine BSE on a 20-m-deep, permeable sandy soil. Discharge from soil to ditch was temporarily collected in an in-stream reservoir to measure its quantity and quality, both for a BS and a reference (REF) treatment. Treatments were replicated once for the first, and three times for the next three leaching seasons. No significant BSE was obtained for nitrogen and phosphorus species in the reservoirs. Additionally, water samples were taken from the upper groundwater below the treatments. The effect of BS for nitrate was much bigger in upper groundwater than in the reservoirs that also collected groundwater from greater depths that were not influenced by the treatments. We conclude that measuring changes in upper groundwater to assess BSE is only valid under specific hydrogeological conditions. We propose an alternative experimental set-up for future research, including extra measurements before installing the BS and REF treatments to deal with spatial and temporal variability. The use of such data as covariates will increase the power of statistical tests by decreasing between-reservoir variability.     

An update on maternal medication-related embryopathies

There is a general perception that any exposure to medication during pregnancy poses a potential risk to the fetus. Most available data about teratogenic drugs is derived from animal studies, case reports, or cohort studies. As a result, counseling women and their partners about the safety of drugs during pregnancy can be difficult due to limited information about efficacy, pharmacokinetics, and teratogenicity of some drugs. However, this should always be done in the context of weighing up potential teratogenic risks with the perinatal risks of an untreated medical or psychiatric condition. Ideally, this counseling should occur prior to a planned pregnancy so that medications and treatment of chronic medical conditions can be optimized. It is important that clinicians providing antenatal care are able to confidently manage women including utilizing appropriate resources. This paper aims at reviewing a selected (non-exhaustive) list of the most commonly prescribed medications considered significant human teratogens and provides recommendations for pre-conception and antenatal counseling.     

Establishing the link between ammonia emission control and measurements of reduced nitrogen concentrations and deposition

In the context of international efforts to reduce the impactsof atmospheric NH₃ and NH₄ ⁺ (collectively, NH_x), it is important to establish the link between NH₃emissions and monitoring of NH_x concentrations and deposition. This is equally relevant to situations where NH₃emissions changes are certain (e.g. due to changed source sectoractivity), as to cases where NH₃ abatement technologies havebeen implemented. Correct interpretation of adequate atmosphericmeasurements is essential, since monitoring data provide the onlymeans to evaluate trends in regional NH₃ emissions.These issues have been reviewed using available measurements and modelling from nine countries. In addition to historic datasets,the analysis here considers countries where NH₃ source sector activity changed (both increases and decreases) and countries where NH₃ abatement policies have been implemented.In The Netherlands an `ammonia gap' was identified between the expected reduction and results of monitoring, and was attributedinitially to ineffectiveness of the abatement measures. The analysis here for a range of countries shows that atmospheric interactions complicate the expected changes, particularly sinceSO₂ emissions have decreased at the same time, while at manysites the few years of available data show substantial inter-annual variation. It is concluded that networks need to beestablished that speciate between NH₃ and aerosol NH₄ ⁺, in addition to providing wet deposition, and sample at sufficient sites for robust regional estimates to be established. Such measurements will be essential to monitor compliance of the international agreements on NH₃ emission abatement.     

Mining on communal land as a new frontier –a case study of the Kunene Region,Namibia

ABSTRACT

This paper is about mining under communal ownership which makes this kind of mining a new mining frontier. The newness of the frontier is that it has introduced a series of institutional complexities that is uncommon to artisanal and large-scale mining. Mining companies have to negotiate deals with communities and their leaders to be able to prospect for mineral resources. We also argue that the state’s environmental legislation is poorly harmonised with the prevalent conditions in communal areas where mining is gaining greater importance. Legislation remains silent on the rights of those living on communal land. These rights remain in a state of confusion with often negative effects on the local communities who are exposed to a number of duplicating development programmes and legislative structures. The aim of this paper is to explore the dynamics communal mining in the Kunene Region in north-western Namibia.     

Environmental and economic impacts of water scarcity and market reform on the Mooki catchment

Over-allocation of irrigation water has led to widespread environmental degradation in the Murray-Darling Basin (MDB) in Australia, prompting discussions of the water efficiency performance of irrigated industries. There is increasing pressure for irrigators to adopt water efficient practices in line with ecologically sustainable principles, especially with current drought conditions. However, there is great uncertainty surrounding the available practices to improve irrigation efficiency from both ecological and economic standpoints. This paper examines the economic and environmental impact of several possible water efficient practices and government policies, using an interdisciplinary approach combining biophysical modelling and economic modelling. This is done for the case-study of the Mooki catchment in the MDB, located in northern New South Wales, Australia.