Chlorophenols and other related derivatives of environmental concern: properties, distribution and microbial degradation processes

Chlorophenols are chlorinated aromatic compound structures and are commonly found in pesticide preparations as well as industrial wastes. They are recalcitrant to biodegradation and consequently persistent in the environment. A variety of chlorophenols derivatives compounds are highly toxic, mutagenic and carcinogenic for living organisms. Biological transformation by microorganisms is one of the key remediation options that can be exploited to solve environmental pollution problems caused by these notorious compounds. The key enzymes in the microbial degradation of chlorophenols are the oxygenases and dioxygenases. These enzymes can be engineered for enhanced degradation of highly chlorinated aromatic compounds through directed evolution methods. This review underscores the mechanisms of chlorophenols biodegradation with the view to understanding how bioremediation processes can be optimized for cleaning up chloroaromatic contaminated environments.     

Radon measurements by nuclear track detectors in secondary schools in Oke-Ogun region, Nigeria

Radon measurements were performed in secondary schools in the Oke-Ogun area, South-west, Nigeria, by solid state nuclear track detectors (SSNTDs). About seventy CR-39 detectors were distributed in 35 high schools of the Oke-Ogun area. The CR-39 detectors were exposed in the schools for 3 months and then etched in NaOH 6 N solution at 90 °C for 3 h. The tracks were counted manually at the microscope and the radon concentration was determined at the Radioactivity Laboratory, Department of Physics, University of Trieste, Trieste, Italy. The overall average radon concentration in the surveyed area was 45 ± 27 Bq m⁻³. The results indicate no radiological health hazard. The research also focused on parameters affecting radon concentrations such as the age of the building in relation to building materials and floor number of the classrooms. The results show that radon concentrations in ground floors are higher than in upper floors.     

Radionuclide content of concrete building blocks and radiation dose rates in some dwellings in Ibadan, Nigeria

Thirty-two samples of concrete building blocks were collected from different block making industries in Ibadan. The radioactivity concentrations of the natural radionuclides in the samples were determined by gamma-ray spectrometry with a NaI(Tl) detector. The radioactivity concentrations varied from 6.2 to 57.5 Bq kg(-1), 12.4 to 64.9 Bq kg(-1) and 95.3 to 766.1 Bq kg(-1) for 226Ra, 232Th and 40K, respectively. The radium equivalent activities of the 32 samples varied from 51.3 to 175.7 Bq kg(-1). Radiation exposure levels in 30 dwellings were determined using LiF thermoluminescent dosimeters. The annual equivalent dose rates varied from 0.318 to 0.657 mSv y(-1) with a mean of 0.433 mSv y(-1). The annual effective dose rate to the whole body was calculated as 0.236 mSv y(-1), which is less than that (mean) estimated by UNSCEAR for normal background areas.     

Periodic characterization of alkyl-naphthalenes in stack gas and ambient air around a medical waste incinerator

Environmental Science and Pollution Research - Due to the subtle occurrence of environmental polycyclic aromatic hydrocarbon (PAHs) pollution from incinerators, it is seldom considered a...     

Assessment of physico-chemical qualities and heavy metal concentrations of Umgeni and Umdloti Rivers in Durban,South Africa

We assessed the effects of seasonal dynamics on the physico-chemical qualities and heavy metals concentrations of the Umgeni and Umdloti Rivers in Durban, South Africa. Water samples were taken from nine different sampling points and analysed for the following parameters; temperature, pH, turbidity, electrical conductivity (EC), biological oxygen demand (BOD₅), chemical oxygen demand (COD), phosphate (PO₄ ^2?), nitrate (NO₃ ^2?), ammonium (NH₄ ⁺), sulphate (SO₄ ^2?), lead (Pb²⁺), mercury (Hg²⁺), cadmium (Cd²⁺), aluminium (Al³⁺), and copper (Cu²⁺) using standard methods. The data showed variations it terms of the seasonal fluctuations and sampling regime as follows: temperature 12–26.5 °C; pH 5.96–8.45; turbidity 0.53–18.8 NTU; EC 15.8–5180 mS m^?1; BOD₅ 0.60–7.32 mg L^?1; COD 10.5–72.9 mg L^?1; PO₄ ^2??<?500–2,460 μg L^?1; NO₃ ^2? <0.05–4.21 mg L^?1; NH₄ ⁺?<?0.5–1.22 mg L^?1; SO₄ ^2? 3.90–2,762 mg L^?1; Pb²⁺ 0.023–0.135 mg L^?1; Hg²⁺ 0.0122–0.1231 mg L^?1 Cd²⁺ 0.068–0.416 mg L^?1; Al³⁺ 0.037–1.875 mg L^?1, and Cu²⁺0.006–0.144 mg L^?1. The concentrations of most of the investigated parameters exceeded the recommended limit of the South African Guidelines and World Health Organization tolerance limits for freshwater quality. We conclude that these water bodies are potentially hazardous to public health and this highlights the need for implementation of improved management strategies of these river catchments for continued sustainability.     

Bacterial biosensors for rapid and effective monitoring of biodegradation of organic pollutants in wastewater effluents

Significant amounts of toxic substances which are hazardous to animals, plants, microorganisms, and other living organisms including humans are released annually into aquatic and terrestrial environments, mostly from improper wastewater discharges. Early detection of such pollutants in wastewater effluents and proper monitoring before their final release into the environment is therefore necessary. In this study, two whole-cell bacterial biosensors were constructed by transforming competent cells of Shigella flexneri and Shigella sonnei with pLUX plasmids and evaluated for their potential to monitor wastewater samples undergoing degradation by measuring bioluminescence response using a microplate luminometer. Both bacterial biosensors were found to be extremely sensitive to the wastewater samples, with different patterns, concomitant with those of the COD removals demonstrated at the different days of the degradation. Generally higher bioluminescence values were obtained at the later days of the degradation period compared to the initial values, with up to 571.76% increase in bioluminescence value obtained at day 5 for 0.1% (v/v) effluent concentration. Also, a steady decrease in bioluminescence was observed for the bacterial biosensors with increasing time of exposure to the wastewater effluent for all the sampling days. These biosensor constructs could therefore be applicable to indicate the bioavailability of pollutants in a way that chemical analysis cannot, and for in situ monitoring of biodegradation. This has great potential to offer a risk assessment strategy in predicting the level of bioremediation required during municipal wastewater treatment before their final discharge into the aquatic milieu.     

Stakeholders’ Perceptions of GM Technology in West Africa: Assessing the Responses of Policymakers and Scientists in Ghana and Nigeria

The perception of two key stakeholders such as policymakers and scientists on genetic modification (GM) technology was examined in Ghana and Nigeria using semi-structured interviews. A total sample of 20 policymakers (16 at ministries and 4 at parliament/cabinet) and 58 scientists (43 at research institutes and 15 at universities) participated at the interviews. This study revealed respondents perspectives on potential benefits and risks of GM technology, status and development of biosafety regulatory frameworks, role of science and technology innovation in agricultural development, intellectual property right and related issues. The study also shed some light on a possible influence of the European Union and United States in the development and potential adoption of GM technology. More importantly, the article suggests that most respondents including policymakers believe that GM technology has great potential to solve part of agricultural problems in both countries. But, lack of appropriate regulatory framework, lack of trained personnel, weak institutions and poor equipped laboratory among others represent a significant challenge in introducing GM technology in this part of Africa.     

Air quality impact of carbon monoxide emission from diesel engine electric power generators

An emissions inventory and the AERMOD View dispersion model were used to estimate the concentrations and the potential effects of carbon monoxide (CO) from diesel engine electric power generators operated by and providing electricity to a textile factory in Nigeria on its host air shed. The CO emissions from simultaneous operations of all of the electric power generators in the factory resulted in: 1‐hr average CO emissions of 4.2 to 54.5 micrograms per cubic meters (μg/m³) and 24‐hr average CO emissions of 0.3 to 20.9 μg/m³. The estimated 1‐hr averaging period maximum ground‐level concentrations of CO were deposited within the factory, while the 24‐hr maximum ground‐level concentrations are estimated at a distance 90 meters (m) from the factory in a southeast direction. The ground‐level concentrations of CO emanating from the textile factory are within the stipulated ambient air quality standards.     

Land-Cover Change Trajectories in Northern Ghana

Land-cover change trajectories are an emergent property of complex human–environment systems such as the land-use system. An understanding of the factors responsible for land change trajectories is fundamental for land-use planning and the development of land-related policies. The aims of this study were to characterize and identify the spatial determinants of agricultural land-cover change trajectories in northern Ghana. Land-cover change trajectories were defined using land-cover maps prepared from Landsat Thematic Mapper dataset acquired in 1984, 1992, and 1999. Binary logistic regression was used to model the probability of observing the trajectories as a function of spatially explicit biophysical and socioeconomic independent variables. Population densities generally increased along the continuum of land-use intensity, whereas distance from market and roads generally decreased along this continuum. Apparently, roads and market serve as incentives for settlement and agricultural land use. An increase in population density is an important spatial determinant only for trajectories where the dominant change process is agricultural extensification. A major response to population growth is an increase in cultivation frequency around the main market. Agricultural intensification is highly sensitive to accessibility by roads. The increase in land-use intensity is also associated with low soil quality. These results suggest the need for policies to restore soil fertility for agricultural sustainability. The models also provide a means for identifying functional relationships for in-depth analyses of land-use change in Ghana.     

Biostimulation and bioaugmentation enhances aerobic biodegradation of dichloroethenes

The accumulation of dichloroethenes (DCEs) as dominant products of microbial reductive dechlorination activity in soil and water represent a significant obstacle to the application of bioremediation as a remedial option for chloroethenes in many contaminated systems. In this study, the effects of biostimulation and/or bioaugmentation on the biodegradation of cis- and trans-DCE in soil and water samples collected from contaminated sites in South Africa were evaluated in order to determine the possible bioremediation option for these compounds in the contaminated sites. Results from this study indicate that cis- and trans-DCE were readily degraded to varying degrees by natural microbial populations in all the soil and water samples tested, with up to 44% of cis-DCE and 41% of trans-DCE degraded in the untreated soil and water samples in two weeks. The degradation rate constants ranged significantly (P<0.05) between 0.0938 and 0.560 wk(-1) and 0.182 and 0.401 wk(-1), for cis- and trans-DCE, respectively, for the various treatments employed. A combination of biostimulation and bioaugmentation significantly increased the biodegradation of both compounds within two weeks; 14% for cis-DCE and 18% for trans-DCE degradation, above those observed in untreated soil and water samples. These findings support the use of a combination of biostimulation and bioaugmentation for the efficient biodegradation of these compounds in contaminated soil and water. In addition, the results clearly demonstrate that while naturally occurring microorganisms are capable of aerobic biodegradation of cis- and trans-DCE, biotransformation may be affected by several factors, including isomer structure, soil type, and the amount of nutrients available in the water and soil.