Key Environmental Parameters Research Articles

Disparities of Environmental Risk Factors Influence Heterogeneity of Malaria Prevalence in Uganda

Malaria is environmentally linked disease of public health concern, yet the aspect of environment in elucidating dynamics of its transmission has not received adequate research focus in Africa and Uganda in particular. A descriptive survey using field observation data sheets and household questionnaire-based survey with 141 respondents were used to collect data from February 2006 to May 2006. The study assessed local knowledge, attitudes and practice for malaria control, as well as key environmental parameters that facilitate human-mosquito interactions. The results demonstrated that perception and degraded environment had positive and significant association with malaria prevalence in Mbale Municipality (p < 0.01). These results suggest that public health education on environmental management for health could result in increased local knowledge be- coming a basis for creating a joint malaria control platform, with communities playing proactive role at the forefront of any interventions for malaria control.

Performance Study of Mobile TV over Mobile WiMAX Considering Different Modulation and Coding Techniques

With the advent of the wide-spread use of smart phones, video streaming over mobile wireless networks has suddenly taken a huge surge in recent years. Considering its enormous potential, mobile WiMAX is emerging as a viable technology for mobile TV which is expected to become of key importance in the future of mobile industry. In this paper, a simulation performance study of Mobile TV over mobile WiMAX is conducted with different types of adaptive modulation and coding taking into account key system and environment parameters which include the variation in the speed of the mobile, path-loss, scheduling service classes with the fixed type of modulations. Our simulation has been conducted using OPNET simulation. Simulation results show that dynamic adaptation of modulation and coding schemes based on channel conditions can offer considerably more enhanced QoS and at the same time reduce the overall bandwidth of the system.

Design of railway bridges considering life-cycle assessment

The world is currently confronted with the challenge of preventing environmental degradation and resource depletion. To compare the environmental performance of two railway bridge designs, an Excel-based model was developed with implementing a simplified quantitative life-cycle assessment. The model covers the entire life cycle of the bridge, from raw material extraction to construction materials recycling and disposal. Various assumptions are made for selecting the relevant emissions and environmental impacts. A streamlined approach is applied to compare the environmental burden throughout the life cycle of the Banafjäl Railway Bridge. The bridge is a simply supported composite structure carrying one railway track. Two track alternatives are investigated: ballasted track and fixed track. The results show that the environmental impacts of the fixed track alternative are lower than those of the ballasted track alternative. From a sustainable development perspective, it appears that fixed track has a significant advantage as the overall environmental impact is reduced by up to 77%. The raw material phase is found to be decisive in the life cycle of both alternatives. The frequency of track replacement is identified as a key environmental parameter, because the extra environmental burden of traffic delay during bridge closure nearly overwhelmed the other life-cycle stages.

Improvement of production rate on recombinant CHO cells in two-stage culture

Background Cultivation temperature is a key environmental parameter that influences cell growth and recombinant protein production. Recombinant CHO (rCHO) cells are usually cultivated at 37 °C. Although lowering culture temperature below 37 °C decrease specific growth rate, in many cases, the specific production rate, q, of CHO cells was not enhanced by lowering the culture temperature. Unlike the specific growth rate, effects of low temperature cultivation on specific productivity rate are not so clear [1]. In the present study, we investigated the effect of low temperature cultivation on rCHO cell growth and production rate. We proposed a two-stage culture that the cultivation was carried out at 37 °C and then a culture temperature become lower. We report that the final production concentration by the two-stage culture is higher than that in case of a flat temperature at 37 °C.

Physico-chemical and biological characterization of anopheline mosquito larval habitats (Diptera: Culicidae): implications for malaria control

BackgroundA fundamental understanding of the spatial distribution and ecology of mosquito larvae is essential for effective vector control intervention strategies. In this study, data-driven decision tree models, generalized linear models and ordination analysis were used to identify the most important biotic and abiotic factors that affect the occurrence and abundance of mosquito larvae in Southwest Ethiopia.MethodsIn total, 220 samples were taken at 180 sampling locations during the years 2010 and 2012. Sampling sites were characterized based on physical, chemical and biological attributes. The predictive performance of decision tree models was evaluated based on correctly classified instances (CCI), Cohen’s kappa statistic (κ) and the determination coefficient (R2). A conditional analysis was performed on the regression tree models to test the relation between key environmental and biological parameters and the abundance of mosquito larvae.ResultsThe decision tree model developed for anopheline larvae showed a good model performance (CCI = 84 ± 2%, and κ = 0.66 ± 0.04), indicating that the genus has clear habitat requirements. Anopheline mosquito larvae showed a widespread distribution and especially occurred in small human-made aquatic habitats. Water temperature, canopy cover, emergent vegetation cover, and presence of predators and competitors were found to be the main variables determining the abundance and distribution of anopheline larvae. In contrast, anopheline mosquito larvae were found to be less prominently present in permanent larval habitats. This could be attributed to the high abundance and diversity of natural predators and competitors suppressing the mosquito population densities.ConclusionsThe findings of this study suggest that targeting smaller human-made aquatic habitats could result in effective larval control of anopheline mosquitoes in the study area. Controlling the occurrence of mosquito larvae via drainage of permanent wetlands may not be a good management strategy as it negatively affects the occurrence and abundance of mosquito predators and competitors and promotes an increase in anopheline population densities.

A Metagenomics Transect into the Deepest Point of the Baltic Sea Reveals Clear Stratification of Microbial Functional Capacities

The Baltic Sea is characterized by hyposaline surface waters, hypoxic and anoxic deep waters and sediments. These conditions, which in turn lead to a steep oxygen gradient, are particularly evident at Landsort Deep in the Baltic Proper. Given these substantial differences in environmental parameters at Landsort Deep, we performed a metagenomic census spanning surface to sediment to establish whether the microbial communities at this site are as stratified as the physical environment. We report strong stratification across a depth transect for both functional capacity and taxonomic affiliation, with functional capacity corresponding most closely to key environmental parameters of oxygen, salinity and temperature. We report similarities in functional capacity between the hypoxic community and hadal zone communities, underscoring the substantial degree of eutrophication in the Baltic Proper. Reconstruction of the nitrogen cycle at Landsort deep shows potential for syntrophy between archaeal ammonium oxidizers and bacterial denitrification at anoxic depths, while anaerobic ammonium oxidation genes are absent, despite substantial ammonium levels below the chemocline. Our census also reveals enrichment in genetic prerequisites for a copiotrophic lifestyle and resistance mechanisms reflecting adaptation to prevalent eutrophic conditions and the accumulation of environmental pollutants resulting from ongoing anthropogenic pressures in the Baltic Sea.

Transcriptomic characterization of cold acclimation in larval zebrafish

BackgroundTemperature is one of key environmental parameters that affect the whole life of fishes and an increasing number of studies have been directed towards understanding the mechanisms of cold acclimation in fish. However, the adaptation of larvae to cold stress and the cold-specific transcriptional alterations in fish larvae remain largely unknown. In this study, we characterized the development of cold-tolerance in zebrafish larvae and investigated the transcriptional profiles under cold stress using RNA-seq.ResultsPre-exposure of 96 hpf zebrafish larvae to cold stress (16°C) for 24 h significantly increased their survival rates under severe cold stress (12°C). RNA-seq generated 272 million raw reads from six sequencing libraries and about 92% of the processed reads were mapped to the reference genome of zebrafish. Differential expression analysis identified 1,431 up- and 399 down-regulated genes. Gene ontology enrichment analysis of cold-induced genes revealed that RNA splicing, ribosome biogenesis and protein catabolic process were the most highly overrepresented biological processes. Spliceosome, proteasome, eukaryotic ribosome biogenesis and RNA transport were the most highly enriched pathways for genes up-regulated by cold stress. Moreover, alternative splicing of 197 genes and promoter switching of 64 genes were found to be regulated by cold stress. A shorter isoform of stk16 that lacks 67 amino acids at the N-terminus was specifically generated by skipping the second exon in cold-treated larvae. Alternative promoter usage was detected for per3 gene under cold stress, which leading to a highly up-regulated transcript encoding a truncated protein lacking the C-terminal domains.ConclusionsThese findings indicate that zebrafish larvae possess the ability to build cold-tolerance under mild low temperature and transcriptional and post-transcriptional regulations are extensively involved in this acclimation process.

The eStation, an Earth Observation processing service in support to ecological monitoring

The eStation is a collecting and processing system designed to automatically deal with the reception, processing, analysis and dissemination of key environmental parameters derived from remotely sensed data. Developed mainly at the Joint Research Centre of the European Commission, the eStation has been distributed to 47 sub-Saharan countries in the frame of the AMESD (Africa n Monitoring of Environment for Sustainable Development) project to provide local institutions with the capacity to easily access a large range of remote sensing products on vegetation, precipitation, fires and oceans. These products, derived from the processing of images coming from various instruments including SPOT-Vegetation, MSG-SEVIRI and MODIS are developed to allow end-users to make local and regional assessments of the state of marine and terrestrial ecosystems. The products, dispatched to the users through the EUMETSAT data broadcasting system (EUMETCast) or provided by other Earth Observation (EO) data agencies (e.g. NASA), are further processed by the eStation to allow end-users to generate their own environmental, whether terrestrial or marine, assessments and reports. Initially designed as a stand-alone system using an open source development framework, the eStation has recently been further developed as a web processing service to allow a broader range of end-users to access the data and services over the Internet. It is the purpose of this paper to introduce the readers to the eStation and its products, to share the lessons learnt in deploying these services as well as to discuss its more recent use in chained environmental web based modeling services.

Optimization of ventilation system operation in office environment using POD model reduction and genetic algorithm

The purpose of this paper is to develop a numerical optimization methodology of ventilation system operation that help improve indoor environment quality and energy costs for space heating and cooling simultaneously. By introducing proper orthogonal decomposition (POD) based model reduction technique into computational fluid dynamics (CFD) simulation, the spatial distributions of key environmental parameters are firstly considered in optimization procedure, which enable to help improve the environment comfort of occupied zones in a office room. Four types of low-dimension parameter spaces are acquired by POD method including indoor temperature, airflow, CO2 concentration and predicted mean vote (PMV) distributions. The precisions of the reconstructed spaces are compared with those of CFD-based original ones. Because of the extremely lower dimension, resulted parameter subspaces are suitable for optimization process in this study. In the proposed genetic algorithm (GA), the objective function is constructed in a way attempting to aggregate and weight indices into one indicator, such as index of PMV, space temperature gradients (STG), indoor air quality (IAQ), energy cost of heating and cooling, etc. A simulation based case study is conducted, which indicates that the presented optimization approach is able to improve indoor comfort and energy costs of ventilation system in a balanced way.

Nitrifying and denitrifying microbial communities and their relationship to nutrient fluxes and sediment geochemistry in the Derwent Estuary, Tasmania

Mineralisation, nitrification and denitrification in sediments are key processes that contribute to the removal of nitrogen from coastal waters. Together these processes are important in preventing the buildup of nitrogen, which can lead to eutrophication in estuarine systems. Spatial and temporal patterns in the composition of nitrifier (bacterial [AOB] and archaeal ammonia oxidizers [AOA]; amoA ), denitrifier ( nirS ) and total bacterial and archaeal (16S rRNA gene) communities in sediment from the Derwent Estuary in southeast Tasmania, Australia, were contrasted with key environmental parameters and benthic nutrient fluxes. Spatial and temporal factors were significant in terms of shaping microbial community composition. Organic matter composition (C:N isotope ratios, %N and %C) was significantly related to the abundance of the different microbial guilds. There was a significant correlation between both the sediment nitrogen content and carbon stable isotope ratio with community composition for total bacteria, AOA and denitrifiers. Sediment chlorophyll a was significantly associated with AOB composition and carbon isotope ratio was related to total archaeal community composition.

Environmental perverse incentives in coastal monitoring

It can be argued that the intensity of monitoring of coastal marine environments lags behind the equivalent terrestrial environments. This results in a paucity of long-term time series of key environmental parameters such as turbidity. This lack of management information of the sources and sinks, and causes and impacts of stressors to the coastal marine environment, along with a lack of co-ordination of information collection is compromising the ability of environmental impact assessments of major coastal developments to discriminate between local and remote anthropogenic impacts, and natural or background processes. In particular, the quasi outsourcing of the collection of coastal information can lead to a perverse incentive whereby in many cases nobody is actively or consistently monitoring the coastal marine environment effectively. This is particularly the case with regards to the collection of long-term and whole-of-system scale data. This lack of effective monitoring can act to incentivise poor environmental performance.

Plant Invasions in China – Challenges and Chances

Invasive species cause serious environmental and economic harm and threaten global biodiversity. We set out to investigate how quickly invasive plant species are currently spreading in China and how their resulting distribution patterns are linked to socio-economic and environmental conditions. A comparison of the invasive plant species density (log species/log area) reported in 2008 with current data shows that invasive species were originally highly concentrated in the wealthy, southeastern coastal provinces of China, but they are currently rapidly spreading inland. Linear regression models based on the species density and turnover of invasive plants as dependent parameters and principal components representing key socio-economic and environmental parameters as predictors indicate strong positive links between invasive plant density and the overall phytodiversity and associated climatic parameters. Principal components representing socio-economic factors and endemic plant density also show significant positive links with invasive plant density. Urgent control and eradication measures are needed in China's coastal provinces to counteract the rapid inland spread of invasive plants. Strict controls of imports through seaports need to be accompanied by similarly strict controls of the developing horticultural trade and underpinned by awareness campaigns for China's increasingly affluent population to limit the arrival of new invaders. Furthermore, China needs to fully utilize its substantial native phytodiversity, rather than relying on exotics, in current large-scale afforestation projects and in the creation of urban green spaces.

The effect of cyclic moisture and temperature on mould growth on wood compared to steady state conditions

Moisture and temperature are the two key environmental parameters that determine the possibility of mould growth on building materials. The time that the material is exposed to these elements is also crucial. The natural environmental conditions of relative humidity and temperature are seldom constant over prolonged time periods in a building. Instead, they vary over time, with fungi encountering both favourable and unfavourable conditions; such variable conditions affect mould growth. This paper reports findings from a laboratory study in which mould growth at alternating RH (between 90% and 60%) or temperature conditions (between 22 °C and 5 °C) was studied and compared to steady state conditions. Fluctuating RH led to slower mould growth, and when the period of unfavourable/favourable conditions was longer (1 week), growth was affected more than if the duration of these conditions was short (12 h). When alternating the temperature weekly between 22 °C and 5 °C, with a mean of 13 °C, the mould growth rate was lower compared to when the temperature was held constant at 22 °C. The mould growth under fluctuating temperature conditions was comparable to when the temperature was kept constant at 10 °C.

MODIS-derived spatiotemporal water clarity patterns in optically shallow Florida Keys waters: A new approach to remove bottom contamination

Retrievals of water quality parameters from satellite measurements over optically shallow waters have been problematic due to bottom contamination of the signals. As a result, large errors are associated with derived water column properties. These deficiencies greatly reduce the ability to use satellites to assess the shallow water environments around coral reefs and seagrass beds. Here, a modified version of an existing algorithm is used to derive multispectral diffuse attenuation coefficient (Kd) from MODIS/Aqua measurements over optically shallow waters in the Florida Keys. Results were validated against concurrent in situ data (Kd(488) from 0.02 to 0.20m−1, N=22, R2=0.68, Mean Ratio=0.93, unbiased RMS=31%), and showed significant improvement over current products when compared to the same in situ data (N=13, R2=0.37, Mean Ratio=1.61, unbiased RMS=50%). The modified algorithm was then applied to time series of MODIS/Aqua data over the Florida Keys (in particular, the Florida Keys Reef Tract), whereby spatial and temporal patterns of water clarity between 2002 and 2011 were elucidated. Climatologies, time series, anomaly images, and empirical orthogonal function analysis showed primarily nearshore–offshore gradients in water clarity and its variability, with peaks in both at the major channels draining Florida Bay. ANOVA revealed significant differences in Kd(488) according to distance from shore and geographic region. Excluding the Dry Tortugas, which had the lowest climatological Kd(488), water was clearest at the northern extent of the Reef Tract, and Kd(488) significantly decreased sequentially for every region along the tract. Tests over other shallow-water tropical waters such as the Belize Barrier Reef also suggested general applicability of the algorithm. As water clarity and light availability on the ocean bottom are key environmental parameters in determining the health of shallow-water plants and animals, the validated new products provide unprecedented information for assessing and monitoring of coral reef and seagrass health, and could further assist ongoing regional zoning efforts.

Effects of short-term changes in sediment temperature on the photosynthesis of two intertidal microphytobenthos communities

Intertidal microphytobenthos (MPB) has been found to maintain high productivity rates despite the variability in various key environmental parameters, namely rapid temperature changes during emersion. The effects of short-term (30 min and 2 h) changes in temperature (15, 25, 35 and 42 °C) on the photosynthetic activity of two intertidal MPB communities (Trancão and Alcochete) of the Tagus estuary were studied using imaging pulse amplitude modulated (Imaging-PAM) fluorometry. MPB communities differed in species composition and size-class distribution: Trancão was dominated by diatoms of the size-class 100–250 μm3, particularly Navicula cf. phyllepta, whereas Alcochete had higher relative abundances for size-class 250–1000 μm3, dominated by a mixture of diatom species of the genera Navicula, Thalassiosira and Gyrosigma. The Trancão MPB community had higher photosynthetic capacity (higher ETRmax), was photoacclimated to higher irradiances (higher Ek) and had lower efficiency at limiting irradiances (lower α). The different taxonomic composition and size-class distribution could explain the observed results, as small cells are usually more active due to larger surface to volume ratios. Photosynthetic capacities of the two studied MPB communities increased with temperature until 35 °C. Photosynthetic efficiencies were not affected by temperature in the 15–35 °C range and both ETRmax and α decreased at the extreme temperature of 42 °C. MPB communities were able to increase photosynthetic capacity and productivity under transient exposure to high sediment temperatures, similar to that observed during summer midday low tides.

Senilia senilis (Linnaeus, 1758), a biogenic archive of environmental conditions on the Banc d'Arguin (Mauritania)

Environmental archives are useful tools for describing past and current climate variations and they provide an opportunity to assess the anthropogenic contribution in coastal ecological changes. Along the West African coast, few studies have focused on such archives in coastal ecosystems. The bloody cockle Senilia senilis, an intertidal bivalve mollusk species, is widely distributed from Western Sahara to Angola, and has been harvested by humans over thousands of years. Therefore, this species appears to be a good candidate for assessing past variations of key environmental parameters such as temperature, primary production, and Saharan dust advection within West African coastal ecosystems. In the present paper, we focused (i) on the identification of growth rhythms of S. senilis shells in Mauritania (Banc d'Arguin), and (ii) on the potential of these shells as (paleo-)environmental archives. The method we used combined environmental survey, sclerochronology, and geochemical analyses of aragonite samples. We showed that microgrowth line formation was controlled by a tidal forcing, leading to the formation of two lines per lunar day. Brightness and thickness of these microgrowth lines progressively decreased from spring to neap tides (fortnightly cycle). Lunar daily growth rates displayed strong seasonal variations, with highest values (>300μm per lunar day) recorded in summer. The oxygen isotope composition of S. senilis shells (δ18Oaragonite) accurately tracked seawater temperature seasonal variations, with a precision of 0.8°C. Finally, we discussed the opportunity to use Ba:Ca ratio in shells as a proxy for primary production or for Saharan dust transport. We also hypothesized that either Canary Currentvariations or, more probably, massive aerosol transfers from Sahara to the Atlantic Ocean could control uranium availability in coastal waters and explain the occurrence of U:Ca peaks within S. senilis shells.

Quantifying spatial variability and biogeochemical controls of ecosystem metabolism in a eutrophic flow-through wetland

Wetlands are highly dynamic ecosystems that exhibit large temporal and spatial gradients in biogeochemical and metabolic processes. While previous studies have documented temporal variability of wetland metabolism, very little is known regarding how wetland metabolism varies spatially. This is particularly relevant for constructed flow-through wetlands used to treat agricultural runoff due to growing concern over the potential for these systems to act as incubators of biological oxygen demanding (BOD) substances (i.e., algal biomass) and contributors to downstream hypoxia. This study employed a spatially explicit characterization of wetland water column properties using multiparameter water quality sondes, thus allowing the calculation of wetland metabolism across a range of spatial scales (meters to 100s of meters). This study documented a high degree of spatial variability in metabolic rates within the wetland, with average gross primary productivity (GPP) ranging from 6.41 to 13.69gO2m−2d−1, community respiration (CR) ranging from 4.85 to 9.79gO2m−2d−1, and net ecosystem production (NEP) ranging from 0.35 to 2.42gO2m−2d−1. Linkages between metabolic rates and environmental controls were quantified using a spatial/temporal statistical approach. Five key environmental parameters (turbidity, dissolved reactive phosphorus, ammonium, electrical conductivity, and temperature) were found to correlate with ecosystem metabolism. Results from this study show that despite high rates of primary productivity, high respiration rates limited NEP in this wetland due to high heterotrophic activity.

The effects of temperature and salinity on 17-α-ethynylestradiol uptake and its relationship to oxygen consumption in the model euryhaline teleost (Fundulus heteroclitus)

The synthetic estrogen 17-α-ethynylestradiol (EE2), a component of birth control and hormone replacement therapy, is discharged into the environment via wastewater treatment plant (WWTP) effluents. The present study employed radiolabeled EE2 to examine impacts of temperature and salinity on EE2 uptake in male killifish (Fundulus heteroclitus). Fish were exposed to a nominal concentration of 100ng/L EE2 for 2h. The rate of EE2 uptake was constant over the 2h period. Oxygen consumption rates (MO2), whole body uptake rates, and tissue-specific EE2 distribution were determined. In killifish acclimated to 18°C at 16ppt (50% sea water), MO2 and EE2 uptake were both lower after 24h exposure to 10°C and 4°C, and increased after 24h exposure to 26°C. Transfer to fresh water (FW) for 24h lowered EE2 uptake rate, and long-term acclimation to fresh water reduced it by 70%. Both long-term acclimation to 100% sea water (32ppt) and a 24h transfer to 100% sea water also reduced EE2 uptake rate by 50% relative to 16ppt. Tissue-specific accumulation of EE2 was highest (40–60% of the total) in the liver plus gall bladder across all exposures, and the vast majority of this was in the bile at 2h, regardless of temperature or salinity. The carcass was the next highest accumulator (30–40%), followed by the gut (10–20%) with only small amounts in gill and spleen. Killifish chronically exposed (15 days) to 100ng/L EE2 displayed no difference in EE2 uptake rate or tissue-specific distribution. Drinking rate, measured with radiolabeled polyethylene glycol-4000, was about 25 times greater in 16ppt-acclimated killifish relative to FW-acclimated animals. However, drinking accounted for less than 30% of gut accumulation, and therefore a negligible percentage of whole body EE2 uptake rates. In general, there were strong positive relationships between EE2 uptake rates and MO2, suggesting similar uptake pathways of these lipophilic molecules across the gills. These data will be useful in developing a predictive model of how key environmental parameter variations (salinity, temperature, dissolved oxygen) affect EE2 uptake in estuarine fish, to determine optimal timing and location of WWTP discharges

Compact and autonomous multiwavelength microanalyzer for in-line and in situ colorimetric determinations

Nowadays, the attainment of microsystems that integrate most of the stages involved in an analytical process has raised an enormous interest in several research fields. This approach provides experimental set-ups of increased robustness and reliability, which simplify their application to in-line and continuous biomedical and environmental monitoring. In this work, a novel, compact and autonomous microanalyzer aimed at multiwavelength colorimetric determinations is presented. It integrates the microfluidics (a three-dimensional mixer and a 25 mm length "Z-shape" optical flow-cell), a highly versatile multiwavelength optical detection system and the associated electronics for signal processing and drive, all in the same device. The flexibility provided by its design allows the microanalyzer to be operated either in single fixed mode to provide a dedicated photometer or in multiple wavelength mode to obtain discrete pseudospectra. To increase its reliability, automate its operation and allow it to work under unattended conditions, a multicommutation sub-system was developed and integrated with the experimental set-up. The device was initially evaluated in the absence of chemical reactions using four acidochromic dyes and later applied to determine some key environmental parameters such as phenol index, chromium(VI) and nitrite ions. Results were comparable with those obtained with commercial instrumentation and allowed to demonstrate the versatility of the proposed microanalyzer as an autonomous and portable device able to be applied to other analytical methodologies based on colorimetric determinations.

Degradation of Chlorinated Phenols by Zero Valent Iron and Bimetals of Iron: A Review

Chlorophenols (CPs) are widely used industrial chemicals that have been identified as being toxic to both humans and the environment. Zero valent iron (ZVI) and iron based bimetallic systems have the potential to efficiently dechlorinate CPs. This paper reviews the research conducted in this area over the past decade, with emphasis on the processes and mechanisms for the removal of CPs, as well as the characterization and role of the iron oxides formed on the ZVI surface. The removal of dissolved CPs in iron-water systems occurs via dechlorination, sorption and co-precipitation. Although ZVI has been commonly used for the dechlorination of CPs, its long term reactivity is limited due to surface passivation over time. However, iron based bimetallic systems are an effective alternative for overcoming this limitation. Bimetallic systems prepared by physically mixing ZVI and the catalyst or through reductive deposition of a catalyst onto ZVI have been shown to display superior performance over unmodified ZVI. Nonetheless, the efficiency and rate of hydrodechlorination of CPs by bimetals depend on the type of metal combinations used, properties of the metals and characteristics of the target CP. The presence and formation of various iron oxides can affect the reactivities of ZVI and bimetals. Oxides, such as green rust and magnetite, facilitate the dechlorination of CPs by ZVI and bimetals, while oxide films, such as hematite, maghemite, lepidocrocite and goethite, passivate the iron surface and hinder the dechlorination reaction. Key environmental parameters, such as solution pH, presence of dissolved oxygen and dissolved co-contaminants, exert significant impacts on the rate and extent of CP dechlorination by ZVI and bimetals.