Systematic literature review of the performance characteristics of Chebyshev polynomials in machine learning applications for economic forecasting in low-income communities in sub-Saharan Africa.

Chebyshev polynomials have unique properties that place them in a class of functions that are highly efficient in the approximation of non-linear functions. Machine learning techniques are being applied to solve complex non-linear problems in the financial markets where there is a proliferation of financial products. The techniques for valuing diverse portfolios of these products can be time consuming and expensive. Formal research has been conducted to determine how machine learning can considerably reduce the computational effort without losing accuracy. The objective of this systematic literature review is to discover evidence of research on the optimal use of Chebyshev polynomials in machine learning and neural networks that may be used for the estimation of generalized financial outcomes of large clusters of small economic units in low-income communities in sub-Saharan Africa. Scopus, ProQuest, and Web of Science databases were queried with search criteria designed to recover peer-reviewed research articles that addressed this objective. Many articles discussing broader applications in engineering, computer science, and applied mathematics were found. Several articles provided insights into the challenges of forecasting stock price outcomes from unpredictable market activities, and in investment portfolio valuations. One article addressed specific environmental issues relating to energy, biology, and ecological situations, and presented encouraging results. While the literature search did not find any similar articles that address economic forecasting for low-income communities, the applications and techniques used in stock market forecasting and portfolio valuations can contribute to formative theory on sustainable development. There is currently no theoretical underpinning of sustainable development initiatives in developing countries. A framework for small business structures, data collection, and near real-time processing is proposed as a potential data-driven approach to guide policy decisions and private sector involvement. Supplementary Information: The online version contains supplementary material available at 10.1007/s43546-022-00328-w.

Estimation of Measurement Uncertainties for the DGT Passive Sampler Used for Determination of Copper in Water.

Diffusion-based passive samplers are increasingly used for water quality monitoring. While the overall method robustness and reproducibility for passive samplers in water are widely reported, there has been a lack of a detailed description of uncertainty sources. In this paper an uncertainty budget for the determination of fully labile Cu in water using a DGT passive sampler is presented. Uncertainty from the estimation of effective cross-sectional diffusion area and the instrumental determination of accumulated mass of analyte are the most significant sources of uncertainty, while uncertainties from contamination and the estimation of diffusion coefficient are negligible. The results presented highlight issues with passive samplers which are important to address if overall method uncertainty is to be reduced and effective strategies to reduce overall method uncertainty are presented.

Evaluation of a passive sampler for the speciation of metals in urban runoff water.

Metals in urban runoff water need to be monitored in order to estimate fluxes and assess their impact on the aquatic environment. Passive sampling is a useful and reliable emerging tool for measuring time averaged concentrations of metals in water bodies. This paper describes the deployment of a passive sampler to measure Cu, Ni and Zn in an urban runoff water treatment facility. The concentrations derived from the passive samplers are compared to concentrations obtained from an automated water sampler which provides pooled spot water samples and to model predictions from the visualMINTEQ computer speciation code. Results show that visualMINTEQ predictions partly describe the metal speciation in non-equilibrium systems. In addition we conclude that passive samplers are useful for monitoring and characterization of metal speciation under chemodynamic conditions.

Performance of a passive sampler for the determination of time averaged concentrations of nitrate and phosphate in water.

A passive sampler device for the kinetic accumulation of nitrate (NO3(-)) and phosphate (HPO4(2-)) in water was developed and calibrated. The sampler incorporates an ion-exchange disk as the receiving phase and selectively collects nitrate and phosphate at sampling rates of 197 ± 43 and 75 ± 12 mL per day, respectively. Minimum exposure times under nutrient rich and nutrient poor conditions were estimated to be 3 and 27 days respectively for phosphate and 1 and 7 days respectively for nitrate. The influence of the environmental variables pH (5-9), temperature (7-21 °C) and turbulence (50-400 rpm) on sampling rates was investigated. Temperature was found to have a significant influence on uptake rates for both anions, while pH influenced phosphate only. Water turbulence did not influence the uptake rates under the studied conditions. A series of field studies was conducted at a municipal wastewater treatment plant. Results for the passive sampler were lower than concentrations obtained using conventional measurement methods, due to methodological differences, and biofouling was found to affect the results for sampling periods over 3 days. This study shows that passive sampling can be used to monitor nitrate and phosphate concentrations in aqueous media. The approach provides an interesting alternative to grab sampling as it yields time-averaged concentrations of the analytes.

Replacement predictions for drinking water networks through historical data.

Lifetime distribution functions and current network age data can be combined to provide an assessment of the future replacement needs for drinking water distribution networks. Reliable lifetime predictions are limited by a lack of understanding of deterioration processes for different pipe materials under varied conditions. An alternative approach is the use of real historical data for replacement over an extended time series. In this paper, future replacement needs are predicted through historical data representing more than one hundred years of drinking water pipe replacement in Gothenburg, Sweden. The verified data fits well with commonly used lifetime distribution curves. Predictions for the future are discussed in the context of path dependence theory.

Importance of automobile exhaust catalyst emissions for the deposition of platinum, palladium, and rhodium in the northern hemisphere.

An estimated 500 million vehicles worldwide are equipped with an exhaust catalyst that uses platinum group elements (PGE) as the main active components and thus contribute to global PGE emissions. Although PGE emitted from automobile exhaust catalysts were first believed to remain in the roadside environment, we propose here that fine PGE-containing particles in automobile exhaust have resulted in a widespread distribution of emitted PGE. Regional and long-range transport of PGE from automobile exhaust catalysts is supported by elevated PGE deposition in both a peat bog located 250 m from traffic and in central Greenland, respectively. Russian smelters were also found to contribute to PGE contamination in central Greenland. Deposition rates estimated for the roadside environment, the peat bog, and central Greenland were used to provide a first estimate of PGE deposition in the northern hemisphere. The results show that deposition of regionally or long-range transported PGE accounts for a large fraction of total PGE deposition, and PGE deposition in the roadside environment represents less than 5% of the total deposition. Transport at the regional and global scales represents an important component in the environmental cycle of emitted PGE and needs to be further studied to fully assess the environmental fate of PGE from automobile exhaust catalysts.

Platinum group element concentrations and osmium isotopic composition in urban airborne particles from Boston, Massachusetts.

Platinum, Pd, Rh, and Os were found to occur at elevated concentrations in airborne particles (PM10) collected at urban sites in Boston, MA. Average Pt, Pd, Rh, and Os concentrations were 6.9 +/- 1.9, 8.1 +/- 1.8, 1.50 +/- 0.50, and 0.068 (-0.068 + 0.070) pg m(-3), respectively. Elevated Pt, Pd, and Rh concentrations are attributed to automobile catalysts, which use Pt, Pd, and Rh for the removal of pollutants from engine exhaust gas. An automobile catalyst source is supported by significant correlations between these elements and by a Pt/Rh similar to that in catalysts. Elevated Os concentrations are also believed to be the result of emission from automobile catalysts in which Os occurs as an impurity. The isotopic composition of Os (187Os/ 188Os) ranged from 0.30 to 2.90, indicating large variations in Os sources. Osmium has a predominantly anthropogenic origin at concentrations > 0.1 pg m(-3), whereas natural sources are more important at lower Os concentrations. Osmium isotopic composition also indicates that Pt, Pd, and Rh in Boston air are of almost exclusive anthropogenic origin, with a relatively small natural contribution. Our results indicate that scavenging by rain plays a major role in the atmospheric residence time and environmental fate of PGE.

Environmental routes for platinum group elements to biological materials--a review.

The increased use of platinum group elements (PGE) in automobile catalysts has led to concern over potential environmental and biological accumulation. Platinum (Pt), palladium (Pd) and rhodium (Rh) concentrations have increased in the environment since the introduction of automobile catalysts. This review summarises current knowledge concerning the environmental mobility, speciation and bioavailability of Pt, Pd and Rh. The greater proportion of PGE emissions is from automobile catalysts, in the form of nanometer-sized catalyst particles, which deposit on roadside surfaces, as evidenced in samples of road dust, grass and soil. In soil, PGE can be transformed into more mobile species through complexation with organic matter and can be solubilised in low pH rainwater. There are indications that environmentally formed Pd species are more soluble and hence more mobile in the environment than Rh and Pt. PGE can reach waterbodies through stormwater transport and deposition in sediments. Besides external contamination of grass close to roads, internal PGE uptake has been observed for plants growing on soil contaminated with automobile catalyst PGE. Fine particles of PGE were also detected on the surface of feathers sampled from passerines and raptors in their natural habitat, and internal organs of these birds also contained PGE. Uptake has been observed in sediment-dwelling invertebrates, and laboratory studies have shown an uptake of PGE in eel and fish exposed to water containing road dust. The available evidence indicates that the PGE, especially Pd, are transported to biological materials through deposition in roots by binding to sulphur-rich low molecular weight species in plants. PGE uptake to exposed animals have uptake rates in the following order: Pd>Pt>Rh. The liver and kidney accumulate the highest levels of PGE, especially Pd. Urinary Pd and Rh, but not Pt, levels are correlated with traffic intensity. Dental alloys may lead to elevated urinary Pt levels. Platinum is a well-known allergen and Pd also shows a strong sensitisation potential.

Platinum group elements in raptor eggs, faeces, blood, liver and kidney.

The increased use of platinum group elements (PGEs) in automobile catalysts and their emission into the environment has led to a concern over environmental and particularly biological accumulation. Specimens of samples from raptors are useful for the investigation of the impact of PGEs because these birds are found in both urban and rural environments and are invariably at the top of the food chain. Platinum (Pt), palladium (Pd) and rhodium (Rh) concentrations were determined by quadrupole Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) in eggs of the sparrowhawk (Accipiter nisus) and the peregrine falcon (Falco peregrinus), and in blood, liver and kidney of the peregrine falcon, while only Pt was determined in faeces of the peregrine falcon and the gyrfalcon (Falco rusticolus). PGE concentrations were higher in blood compared to both faeces and eggs, while liver and kidney concentrations were not elevated indicating no bioaccumulation through metallothionein pathways. A significant spatial trend could only be established for Pt in faeces. The general lack of a spatial trend is probably due to the widespread distribution of automobiles and the long-range transport of nanoparticles containing PGEs, and because birds migrate and forage over large areas. No significant temporal trend could be established. Higher relative concentrations of Pd, followed by Rh and Pt, indicate a mobility gradient of Pd>>Rh>Pt.

Comparative tissue distribution of metals in birds in Sweden using ICP-MS and laser ablation ICP-MS.

Cadmium, copper, lead, palladium, platinum, rhodium, and zinc profiles were investigated along feather shafts of raptor and other bird species by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The distribution of external versus internal metal contamination of feathers was investigated. The species examined were peregrine falcon (Falco peregrinus), sparrowhawk ( Accipiter nisus), willow grouse (Lagopus lagopus), and house sparrow (Passer domesticus) in Sweden. For habitat comparisons, total Cu, Pb, Zn, and Cd concentrations were analyzed by ICP-MS in feathers of the examined species as well as captive peregrine falcon. For investigation of metal distribution and correlation in different biological materials of raptors, total concentrations of Cu, Pb, Cd, and Zn were also investigated by ICP-MS in feathers, eggs, blood, feces, liver, and kidney of wild peregrine falcon from southwestern Sweden. Laser ablation of feathers revealed that Pb contamination is both external and internal, Zn contamination is internal, and Cd and Cu contamination is predominantly internal, with a few externally attached particles of high concentration. Pb, Cu, and Cd signal intensities were highest in urban habitats and contamination was mainly external in feathers. The background signal intensity of Zn was also higher in birds from urban habitats. The laser ablation profile of PGE (Pt, Pd, Rh) demonstrated that PGE contamination of feathers consists almost exclusively of externally attached PGE-containing particles, with little evidence of internally deposited PGE.Generally, total metal concentrations in feathers were highest in sparrowhawk and house sparrow due to their urban habitat. Total Cu, Zn, and Cd concentrations were highest in liver and kidney due to binding to metallothionein, while the total Pb concentration was highest in feces due to the high excretion rate of Pb. A decreasing temporal trend for Pb in feathers, showing that Pb levels in feathers have decreased since the introduction of nonleaded petrol, is also discussed.

Metal diffusion properties of a Nafion-coated porous membrane in an aquatic passive sampler system.

A cellulose acetate membrane, positioned in a passive sampler system, was coated with the perfluorinated polymer Nafion. Aqueous metal transport through the membrane and the Nafion film was investigated. The Nafion-coated membrane prevents the transport of metals bound to natural organic material to the receiving phase in the passive sampler, while copper associated with small synthetic ligands pass through the Nafion film. Increasing thickness of the Nafion film decreases the metal uptake rate to the receiving phase in the passive sampler and increases the response time. A decreased response time for the passive sampler would provide a better estimation of rapid changes in concentration, particularly for dynamic aquatic systems such as urban runoff. Limited biofouling protection with the Nafion coating was demonstrated by growth inhibition of natural periphyton communities on glass surfaces.

Impact of automobile emissions on the levels of platinum and lead in Accra, Ghana.

Examination of car fleet records in Accra demonstrates an increasing proportion of catalytic converter-equipped cars in the relatively old car fleet (average age 13 years) due to their import from developed countries. However, only leaded petrol is sold in Ghana. Lead anti-knocking additives, which are known to affect catalyst activity and promote thermal sintering and mechanical abrasion, may increase Pt emissions. This possible synergism prompted the concomitant determination of Pb and Pt levels in road dust and roadside soils in Ghana. Both metals followed traffic density with higher concentrations in urban areas compared to remote sites. In urban areas, the range for Pb (365 +/- 93 microg g(-1) for dust and 291 +/- 76 microg g(-1) for soil) reflects precatalyst levels in Europe and the US, while the range for Pt (39 +/- 24 ng g(-1) for dust and 15 +/- 5.3 ng g(-1) for soil) is typical for the same countries. The elevated Pt concentrations were unexpected due to recent introduction of catalysts to Ghana compared to the prolonged use of catalysts in Europe and the US.

Performance of an in situ passive sampling system for metals in stormwater.

A passive sampler has been developed and is demonstrated in situ for urban runoff. The passive sampler is compared to conventional composite (time-dependent and flow-weighted) bottle sampling during and between storm events. The sampling was carried out at established stormwater stations; before and after a stormwater detention pond. In situ deployment of the passive sampler provides the metal concentrations, corresponding to the electrochemically available fraction of total metal, for time-dependent samples collected in parallel. The sampler provides improved accuracy compared to bottle sampling because contamination during sample transport and handling is minimised. Laboratory handling is reduced by direct analysis of the accumulated metals on the receiving membrane by laser ablation inductively coupled plasma mass spectrometry. Passive sampling also solves the problem of metal speciation change during transport to the laboratory, which is a potential problem for bottle samples. The low cost and convenience of the passive sampler and subsequent analysis should allow significantly more extensive spatial and temporal monitoring of metals in the aquatic environment than has previously been possible.

Scanning laser ablation-ICP-MS tracking of platinum group elements in urban particles.

While it has now been demonstrated that platinum group elements (PGE) are released from automobile catalysts into the environment, less is known about the form in which they are emitted and transported. Here we show that scanning laser ablation-inductively coupled plasma-mass spectrometry (scanning laser ablation-ICP-MS) can identify and track individual particles released from automobile catalysts present in environmental particulates and sediments. Particles with high PGE concentrations were found in the exhaust of gasoline and diesel vehicles equipped with catalytic converters. The PGE-Ce association in individual particles provides a definitive fingerprinting for tracking catalyst particles in environmental compartments, while relative PGE signal intensity is an indication of the catalyst type. Scanning laser ablation-ICP-MS of road and aquatic sediments revealed a few PGE containing catalyst particles and it was possible to identify catalyst types for the origin of these particles.

Effect of stormwater runoff on metal distribution in the sediment and interstitial waters of an urban river.

Metals were analysed in the interstitial waters and sediments of an urban river, receiving stormwater and combined sewer overflow, over a two month period and interpreted in terms of rain events. Depth profiles for metal concentrations showed the highest interstitial water concentrations in samples with low sedimentary organic material. Storm events can both resuspend sediments and associated metal-rich interstitial waters and alter the metal distribution between interstitial water and sediment. Metal profiles downstream of a combined sewer overflow showed elevated interstitial water concentrations compared to an upstream site. Downstream sites also reveal evidence of metal burial and resuspension processes during and between wet periods.