Residue Analysis of Organochlorine Pesticides in Water and Sediments from Agboyi Creek, Lagos.

Microlayer water, mixed layer water, epipellic and benthic sediments were collected from Agboyi Creek, Lagos to analyse organochlorine pesticide residues. Sampling was conducted between December 2008 and September 2009 during the dry and wet seasons to study effects of seasonal variation on the samples. Water samples were subjected to liquid-liquid extraction using dichloromethane, while sediments were subjected to cold extraction with petroleum ether/acetone (1:1 v/v) mixture and clean-up on silica gel adsorbents. The samples were analyzed for aldrin, dieldrin, endrin, DDT, heptachlor, HCH, endosulfan, chlordane and methoxychlor. The detection and determination of the pesticide residues were performed by injecting 1 μL of purified extract into the injection port of a gas chromatograph with a 63Ni electron capture detector (GC-μECD Agilent 7890A) equipped with ChemStation software. Pesticide residues in the epipellic and benthic sediments were higher than the residues in the water. The mixed layer water showed enhanced levels of residues when compared with the microlayer water. The residue levels were higher during the dry season than the wet season. The levels of residues in the water and sediments were below the maximum permissive residue limits

On the Physical Design of Molecular Communication Receiver Based on Nanoscale Biosensors

Molecular communications (MC), where molecules are used to encode, transmit, and receive information, is a promising means of enabling the coordination of nanoscale devices. The paradigm has been extensively studied from various aspects, including channel modeling and noise analysis. Comparatively little attention has been given to the physical design of molecular receiver and transmitter, envisioning biological synthetic cells with intrinsic molecular reception and transmission capabilities as the future nanomachines. However, this assumption leads to a discrepancy between the envisaged applications requiring complex communication interfaces and protocols, and the very limited computational capacities of the envisioned biological nanomachines. In this paper, we examine the feasibility of designing a molecular receiver, in a physical domain other than synthetic biology, meeting the basic requirements of nanonetwork applications. We first review the state-of-the-art biosensing approaches to determine whether they can inspire a receiver design. We reveal that nanoscale field effect transistor based electrical biosensor technology (bioFET) is a particularly useful starting point for designing a molecular receiver. Focusing on bioFET-based molecular receivers with a conceptual approach, we provide a guideline elaborating on their operation principles, performance metrics and design parameters. We then provide a simple model for signal flow in silicon nanowire (SiNW) FET-based molecular receiver. Lastly, we discuss the practical challenges of implementing the receiver and present the future research avenues from a communication theoretical perspective

Levels and distribution of chlorinated pesticide residues in water and sediments of Tarkwa Bay, Lagos Lagoon

Microlayer water, mixed layer water, epipellic and benthic sediments were collected from Tarkwa Bay end of Lagos Lagoon to analyse for chlorinated pesticide residues. Sampling was conducted between December 2008 and September 2009 during the dry and wet seasons to study effects of seasonal variation on the samples. Water samples were subjected to liquid-liquid extraction using dichloromethane while sediment samples were subjected to cold extraction with petroleum ether/acetone (1:1 v/v) mixture and clean-up on silica gel adsorbents. The water and sediment samples were analysed for aldrin, dieldrin; endrin, DDT, heptachlor and their metabolites; HCH and endosulfan isomers; α, γ-chlordane and methoxychlor. The detection and determination of the pesticide residues were performed by gas chromatography. Pesticide residues in the epipellic and benthic sediments were higher than residues in the water. The microlayer water showed reduced levels of residues when compared with the mixed layer water. The residue levels were higher during the dry season than the wet season and levels of residues in the water and sediments were within the permissible limits

Fossil Fuels

Fossil fuels are nonrenewable energy resources formed from dead remains of plants and lower animals including phytoplankton and zooplankton that have settled to the sea or lake bottom in large quantities under anoxic conditions. They are nonrenewable resources because they take millions of years to form, and reserves are being depleted much faster than new ones are being formed. They formed from ancient organisms that died and were buried under layers of accumulating sediment. As additional sediment layers built up over these organic deposits, the materials were subjected to increasing temperatures and pressures, leading to the formation of a waxy material known as kerogen, and subsequently hydrocarbons. The processes involved are diagenesis and catagenesis

Sunlight

Sunlight is the electromagnetic radiation given off by the sun. It is passed through the atmosphere to the Earth, where the solar radiation is reflected as daylight. Sunshine results when the solar radiation is not blocked. Sunlight is the primary source of energy to the Earth. It provides infrared, visible, and ultraviolet (UV) electromagnetic radiation with different wavelengths. Small sections of the wavelengths that are visible to the human eye are reflected as rainbow colors. Sunlight may be recorded using a sunshine recorder. Electromagnetic waves are waves that are capable of transporting energy through the vacuum of outer space and that exist with an enormous continuous range of frequencies known as the electromagnetic spectrum. The spectrum is divided into smaller spectra on the basis of interactions of electromagnetic waves with matter

Pesticide

A pesticide is a material used for the mitigation, control, or elimination of plants or animals detrimental to human health or economy. Specifically, a pesticide is a chemical—liquid, granule, or gas—used to kill or control pests such as insects, weeds, bacteria, fungi, rodents, and worms. Pesticides play significant roles in increasing food production and eliminating diseases. However, only a few environmental issues have aroused the concern of the public as much as pesticides because exposure to them can be harmful to huma

Seawater, Composition of

Seawater is a solution of salts of nearly constant composition, dissolved in variable amounts of water. It is denser than fresh water. It is risky to drink seawater because of its high salt content. More water is required to eliminate the salt through excretion than the amount of water that is gained from drinking the seawater. Seawater can be turned into potable water by desalination processes or by diluting it with freshwater. The origin of sea salt is traced to Sir Edmond Halley, who in 1715 proposed that salt and other minerals were carried into the sea by rivers, having been leached out of the ground by rainfall runoff. On reaching the ocean, these salts would be retained and concentrated as the process of evaporation removed the water. There are more than 70 elements dissolved in seawater as ions, but only six make up more than 99 percent of all the dissolved salts; namely, chloride (55.04 weight percent [wt%]), sodium (30.61 wt%), sulphate (7.68 wt%), magnesium (3.69 wt%), calcium (1.16 wt%), and potassium (1.10 wt%). Trace elements in seawater include manganese, lead, gold, and iodine. Biologically important elements such as oxygen, nitrogen, and iron occur in variable concentrations depending on utilization by organisms. Most of the elements occur in parts per million or parts per billion concentrations and are important to some positive and negative biochemical reactions. Properties such as salinity, density, and pH could be used to highlight the composition of seawater

Hydrofluorocarbons

Hydrofluorocarbons (HFCs) are a group of organic compounds that contain carbon, fluorine, and hydrogen. They are by-products of industrial manufacturing and were introduced as a replacement for chlorofluorocarbons and other ozone depleting substances. However, though HFCs have zero ozone depletion potential (ODP), they have intrinsic and significant global warming potential (GWP), typically in the range of 1,000 to 3,000 times that of CO2. Thus, they are among the six key greenhouse gases listed in the Kyoto Protocol for emission reduction. Other greenhouse gases listed by the protocol are CO2, CH4, N2O, PFCs, SF6, and HFCs. Industry and government are collaborating on research and development, communication, and other activities to find new technologies, designs, and processes to manage these emissions. The emissions management is occurring through non-regulatory means, voluntary measures, and industry-government collaborations. The air-conditioning and commercial refrigeration industry has particularly contributed to the success of the management process. HFCs are generally colourless and odourless gases at environmental temperatures and are mostly chemically unreactive. They are non-flammable, having very low toxicity; they are recyclable, and highly energy efficient. There has been a significant growth in the market for HFCs because they have been identified as important alternative fluids for many end users. They find applications in refrigeration and air-conditioning, foam-blowing, general aerosols, solvent cleaning, firefighting, and metered-dose inhaling. They are preferred due to certain physical and chemical characteristics, especially their low toxicity and low flammability. The main sources of atmospheric HFCs are traceable to their sources of application. Two other major emitters are chemical plants making HCFC 22 (where HFC-23 is emitted as a by-product) and HFCs. There are several points in the lifecycle of HFC-using products at which emissions can occur. A computer model uses four emission factors to characterize the HFC emissions, namely fluid manufacturing, product manufacturing, product life, and disposal loss factors. Examples of HFCs include trifluoromethane (HFC-23), difluoromethane (HFC-32), fluoromethane (HFCHydrofluorocarbons 41), 2-chloro-1,1,1,2-tetrafluoroethane (HFC-124), 1,1,2,2,2-pentafluoroethane (HFC-125), 1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,2-tetrafluoroethane (HFC-134a,), 1,1-difluoroethane (HFC-152a), 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea)