Effect of chemical amendments on remediation of potentially toxic trace elements (PTEs) and soil quality improvement in paddy fields

Remediation of potentially toxic trace elements (PTEs) in paddy fields is fundamental for crop safety. In situ application of chemical amendments has been widely adapted because of its cost-effectiveness and environmental safety. The main purpose of this research was to (1) evaluate the reduction in dissolved concentrations of cadmium (Cd) and arsenic (As) with the application of chemical amendments and (2) monitor microbial activity in the soil to determine the remediation efficiency. Three different chemical amendments, lime stone, steel slag, and acid mine drainage sludge, were applied to paddy fields, and rice (Oryza sativa L. Milyang 23) was cultivated. The application of chemical amendments immobilized both Cd and As in soil. Between the two PTEs, As reduction was significant (p < 0.05) with the addition of chemical amendments, whereas no significant reduction was observed for Cd than that for the control. Among six soil-related variables, PTE concentration showed a negative correlation with soil pH (r = ?0.70 for As and r = ?0.54 for Cd) and soil respiration (SR) (r = ?0.88 for As and r = ?0.45 for Cd). This result indicated that immobilization of PTEs in soil is dependent on soil pH and reduces PTE toxicity. Overall, the application of chemical amendments could be utilized for decreasing PTE (As and Cd) bioavailability and increasing microbial activity in the soil.     

Bias from two analytical laboratories involved in a long-term air monitoring program measuring organic pollutants in the Arctic: a quality assurance/quality control assessment

Initiated in 1992, air monitoring of organic pollutants in the Canadian Arctic provided spatial and temporal trends in support of Canada's participation in the Stockholm Convention of Persistent Organic Pollutants. The specific analytical laboratory charged with this task was changed in 2002 while field sampling protocols remained unchanged. Three rounds of intensive comparison studies were conducted in 2004, 2005, and 2008 to assess data comparability between the two laboratories. Analysis was compared for organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in standards, blind samples of mixed standards and extracts of real air samples. Good measurement accuracy was achieved for both laboratories when standards were analyzed. Variation of measurement accuracy over time was found for some OCPs and PCBs in standards on a random and non-systematic manner. Relatively low accuracy in analyzing blind samples was likely related to the process of sample purification. Inter-laboratory measurement differences for standards (<30%) and samples (<70%) were generally less than or comparable to those reported in a previous inter-laboratory study with 21 participating laboratories. Regression analysis showed inconsistent data comparability between the two laboratories during the initial stages of the study. These inter-laboratory differences can complicate abilities to discern long-term trends of pollutants in a given sampling site. It is advisable to maintain long-term measurements with minimal changes in sample analysis.     

Ecotoxicological assessment of acid mine drainage: electrophysiological changes in earthworm (Aporrectodea caliginosa) and aquatic oligochaete (Lumbriculus variegatus)

Ecological health of 15 sites in two mining areas on the West Coast of the South Island, New Zealand, was assessed using a non-invasive electrophysiological technique. The conduction velocity (CV) changes in the medial giant fibres (MGF) of the terrestrial earthworm Aporrectodea caliginosa were measured on days 0, 1, 2, 4, 7, 14, and 21 following exposure to soil and/or sediment from six acid mine drainage (AMD) sites, and aquatic oligochaete Lumbriculus variegatus at 0, 3, 6, and 24 h following exposure to water from 14 AMD sites. The colour of the soil/sediments varied from red-brown to black with pH ranging from 4.46 to 7.37. The colour of AMD water samples varied from clear, black, brown to orange, and the pH ranged from 2.99 to 7.66. The CV decreased progressively in A. caliginosa exposed to most soil and sediment samples from the AMD sites (compared with controls exposed to soil from an organic farm) and this was most evident in measurements taken at 7 days. Based on the CV measurements taken on day 7, sites 3 > 2 > 1 were significantly (P < 0.05) the most toxic to earthworms. The CV of L. variegatus exposed to AMD water sampled from many sites also decreased progressively and this was significantly lower than the controls in the measurements taken at 24 h from sites 3 > 9 > 7 > 11. It is proposed that MGF CV in A. caliginosa and L. variegatus worms can be used as a non-invasive, sensitive, biomarker to monitor the toxicity of AMD sites.     

Dechlorination comparison of mono-substituted PCBs with Mg/Pd in different solvent systems

It is widely recognized that polychlorinated biphenyls (PCBs) are a dangerous environmental pollutant. Even though the use and production of PCBs have been restricted, heavy industrial use has made them a wide-spread environmental issue today. Dehalogenation using zero-valent metals has been a promising avenue of research for the remediation of chlorinated compounds and other contaminants that are present in the environment. However, zero-valent metals by themselves have shown little capability of dechlorinating polychlorinated biphenyls (PCBs). Mechanically alloying the metal with a catalyst, such as palladium, creates a bimetallic system capable of dechlorinating PCBs very rapidly to biphenyl. This study primarily aims to evaluate the effects of solvent specificity on the kinetics of mono-substituted PCBs, in an attempt to determine the mechanism of degradation. Rate constants and final byproducts were determined for the contaminant systems in both water and methanol, and significant differences in the relative rates of reaction were observed between the two solvents.     

Dryland salinity and vector-borne disease emergence in southwestern Australia

Broad-scale clearing of native vegetation for agriculture in southwestern Australia has resulted in severe ecosystem degradation, which has been compounded by the subsequent development of large areas of dryland salinity; decreased transevaporation allows the water table to rise, dissolving ancient aeolian salt deposits and creating saline surface pools. The mosquito-borne disease Ross River virus has been noted as a potential adverse human health outcome in salinity-affected regions because the principal vector, Aedes camptorhynchus, is salt tolerant and thrives preferentially in such systems. To understand the geology and ecology underlying the relationship between land clearing and disease emergence, we examine the relationship between dryland salinity processes that determine the dissolved solids profile of saline pools in affected areas, the mosquito vectors and interactions with the human population within the disease cycle. Aedes camptorhynchus is able to survive in a wide range of salinities in pools created by dryland salinity processes. The link with disease emergence is achieved where population distribution and activity overlaps with the convergence of environmental and ecological conditions that enhance disease transmission.     

The risks of risk-based regulation: insights from the environmental policy domain

Risk-based regulation has become increasingly popular in recent years. Proponents argue that it facilitates robust governance, contributing to efficient and effective use of regulatory resources and delivering interventions in proportion to risk. Critics contend that the challenges of operationalising risk-based governance mitigate its potential benefits. In this paper we start by considering what we mean by risk-based governance and discuss some of the factors shaping the adoption of such strategies. We then consider the development and operation of risk-based approaches in the environmental policy domain, focusing specifically on the regulation of contaminated land and radioactive waste. We argue that whilst risk-based approaches can offer important benefits, they face a range of epistemic, institutional and normative challenges that can play an important role in shaping the way that organisations manage both risks to society and their own institutional risks. This has profound implications for achieving regulatory objectives and, for this paper, the environmental outcomes that the regulations are designed to deliver.     

Investigating the capacity of an activated sludge process to reduce volatile organic compounds and odor emissions.

The effects of hydrogen sulfide (H2S) diffusion into activated sludge (AS) on odor and volatile organic compound (VOC) concentrations in offgas were studied over an 8-week period. Most VOCs detected in the offgas of both aeration tanks were aromatic hydrocarbons. The VOC concentrations generally decreased when H2S was introduced to the AS compared with the control, indicating a negative effect of H2S on VOC removal. Two volatile organic sulfur compounds present in the test AS offgas showed an increase followed by a decrease during H2S peak loads. Six VOCs and odor concentration increased during the introduction of an H2S peak; however no correlation was observed between H2S and odor concentration. The increase in odor concentration resulted from the increase in the concentration of six aromatic VOCs, which had their removal slowed down during a 100-ppmv H2S peak. Activated sludge diffusion provides effective H2S removal with minimal affect on odor emissions.     

An Evaluation of Multiple Objective Decision Support Weighting Techniques in Natural Resource Management

Multiple objective decision support (MODS) is a structured framework for evaluating decision alternatives against multiple, and often conflicting, criteria. Its ability to handle complex trade-offs in a variety of quantitative and qualitative units gives it much potential in the field of natural resource management (NRM). A key component of MODS is the process used to obtain information from decision makers on the relative importance of evaluative criteria. Ranking algorithms then use this information to determine the relative value of each decision alternative. This paper explores how practising community based NRM decision makers respond to five generic methods for weighting the criteria. It presents a study in which 55 decision makers throughout five regions in Queensland, Australia, applied MODS to evaluate environmental projects seeking funding under the Australian Natural Heritage Trust. Weighting methods applied include fixed point scoring, rating, ordinal ranking, a graphical method and paired comparisons. Decision makers evaluated each weighting method in terms of ease of use and of how much it helped clarify the decision problem. Results show that decision makers felt uncomfortable applying fixed point scoring and generally preferred to express their preferences through ordinal ranking. This has implications for the types of ranking algorithms that can be applied to evaluate the decision alternatives.     

The biogenic content of process streams from mechanical–biological treatment plants producing solid recovered fuel. Do the manual sorting and selective dissolution determination methods correlate?

The carbon emissions trading market has created a need for standard methods for the determination of biogenic content (χ_B) in solid recovered fuels (SRF). We compare the manual sorting (MSM) and selective dissolution methods (SDM), as amended by recent research, for a range of process streams from a mechanical–biological treatment (MBT) plant. The two methods provide statistically different biogenic content values, as expressed on a dry mass basis, uncorrected for ash content. However, they correlate well (r² > 0.9) and the relative difference between them was <5% for χ_B between 21% ^w/w_d and 72% ^w/w_d (uncorrected for ash content). This range includes the average SRF biogenic content of ca. 68% ^w/w_d. Methodological improvements are discussed in light of recent studies. The repeatability of the SDM is characterised by relative standard deviations on triplicates of <2.5% for the studied population.     

Analysis of PM10, PM2.5, and PM2 5-10 concentrations in Santiago, Chile, from 1989 to 2001

Daily particle samples were collected in Santiago, Chile, at four urban locations from January 1, 1989, through December 31, 2001. Both fine PM with da < 2.5 microm (PM2.5) and coarse PM with 2.5 < da < 10 microm (PM2.5-10) were collected using dichotomous samplers. The inhalable particle fraction, PM10, was determined as the sum of fine and coarse concentrations. Wind speed, temperature and relative humidity (RH) were also measured continuously. Average concentrations of PM2.5 for the 1989-2001 period ranged from 38.5 microg/m3 to 53 microg/m3. For PM2.5-10 levels ranged from 35.8-48.2 microg/m3 and for PM10 results were 74.4-101.2 microg/m3 across the four sites. Both annual and daily PM2.5 and PM10 concentration levels exceeded the U.S. National Ambient Air Quality Standards and the European Union concentration limits. Mean PM2.5 levels during the cold season (April through September) were more than twice as high as those observed in the warm season (October through March); whereas coarse particle levels were similar in both seasons. PM concentration trends were investigated using regression models, controlling for site, weekday, month, wind speed, temperature, and RH. Results showed that PM2.5 concentrations decreased substantially, 52% over the 12-year period (1989-2000), whereas PM2.5-10 concentrations increased by approximately 50% in the first 5 years and then decreased by a similar percentage over the following 7 years. These decreases were evident even after controlling for significant climatic effects. These results suggest that the pollution reduction programs developed and implemented by the Comisión Nacional del Medio Ambiente (CONAMA) have been effective in reducing particle levels in the Santiago Metropolitan region. However, particle levels remain high and it is thus imperative that efforts to improve air quality continue.