Assessment of heavy metals and crude protein content of molluscs and crustaceans from two selected cities in Nigeria

Crabs, shrimps, periwinkles and land snails form a source of aquatic food which is widely consumed in Nigeria. Therefore, there is need for comparison of nutritional information and heavy metals accumulation potentials of these organisms. The aim of this study was to quantify heavy metals (Cu, Zn, Pb and Cd) and crude protein content of these species that are sold in markets in Ibadan and Lagos, Nigeria. In addition, the influence of location, organism species, organism age, and processing on the levels of the analytes were also investigated. The results showed that mean Cu concentrations ranged from 4.88±0.54μg/g in edible land snail (Gabiella africana) to 34.1±3.0μg/g in raw guinea shrimp (Parapenaeopsis atlantica) and Zn concentrations from 21.4±1.6 in African giant snail (Archarcantina marginata) to 190±21μg/g in raw pink shrimp (Penaeus notialis). The concentration of Zn in all species was below the WHO maximum permissible limit of 100μg/g except in crabs and raw shrimps. Cu concentrations in all the samples except dry shrimps and snails were higher than the WHO permissible level of 10μg/g. Furthermore, highest Pb levels were found in crabs (Callinectes pallidus) (2.74±0.45μg/g) and the minimum mean level of 0.66±0.07μg/g was observed in G. africana. All the samples except dried shrimps contained Pb above the EC limit of 0.5μg/g. The highest mean level (0.20±0.17μg/g) of Cd was detected in crab while the least (0.03±0.01μg/g) was found in periwinkle. However, these levels were lower than the EC limit of 0.5μg/g. The concentrations of Cu, Zn, Pb and Cd in the organisms differed a little between the two sampling locations. The concentration of heavy metals (HMs) varied with studied organisms. For instance, gladiator swim crab (Callinectes pallidus) and raw pink shrimp (P. notalis) bioconcentrated remarkably higher levels of Cu, Zn, Pb and Cd than the other organisms. The process of drying significantly decreased bioavailable HMs in shrimps. Matured snails contained highest concentrations of Cu and Pb while baby snails contained highest levels of Zn. About 63% Cu, 70% Pb, 87% Zn and 10% protein content appeared to be lost during the drying process in shrimps. Crude protein contents ranged from 35.7±2.5% in crabs (C. pallidus) to 79.5±2.0% in snails (G. africana), implying that shrimps, crabs, periwinkles and snails are good sources of animal protein if they are found in contamination free environment.Key words: Heavy metals, protein, crustaceans, mollusc

Heavy metal concentrations in soils and accumulation in plants growing in a deserted slag dumpsite in Nigeria

Early detection and remediation of heavy metals in soil and vegetation will ameliorate serious threats posed to human existence. An auto battery manufacturing company dumped slag containing proportionof heavy metals in an hectare of land at Lalupon, Ibadan, Nigeria. The extent of contamination of soil by heavy metals and their accumulation in plants around the abandoned slag was studied. Plants and thesurrounding soils were sampled from different directions at increasing distance from the vicinity of the waste pile and their concentrations of heavy metals were determined. The levels of Pb, Zn and Ni inmg/kg ranged from 34.8 – 41500, 16.3 – 849 and ND – 48.2; 9.2 – 9700, 16.0 – 271 and 2.83 – 36.9; 4.5- 5670, 8.00 – 174 and ND – 322 in soil, plant root and plant shoot, respectively. The plant samples from the immediate environment of the waste were highly contaminated with Pb. Six plant species, particularly Sporobolus pyramidalis, met some of the conditions to be classified as hyperaccumulatorsfor Pb, Ni and Zn, and three other plants fulfilled the criteria for heavy metal excluders. We conclude that the potential hyperaccumulators and excluders, under controlled conditions, can be used for phytoremediation of the site

Geopolymerisation of fly ashes with waste aluminium anodising etching solutions

Combined management of coal combustion fly ash and waste aluminium anodising etching solutions using geopolymerisation presents economic and environmental benefits. The possibility of using waste aluminium anodising etching solution (AES) as activator to produce fly ash geopolymers in place of the commonly used silicate solutions was explored in this study. Geopolymerisation capacities of five European fly ashes with AES and the leaching of elements from their corresponding geopolymers were studied. Conventional commercial potassium silicate activator-based geopolymers were used as a reference. The geopolymers produced were subjected to physical, mechanical and leaching tests. The leaching of elements was tested on 28 days cured and crushed geopolymers using NEN 12457-4, NEN 7375, SPLP and TCLP leaching tests. After 28 days ambient curing, the geopolymers based on the etching solution activator showed compressive strength values between 51 and 84 MPa, whereas the commercial potassium silicate based geopolymers gave compressive strength values between 89 and 115 MPa. Based on the regulatory limits currently associated with the used leaching tests, all except one of the produced geopolymers (with above threshold leaching of As and Se) passed the recommended limits. The AES-geopolymer geopolymers demonstrated excellent compressive strength, although less than geopolymers made from commercial activator. Additionally, they demonstrated low element leaching potentials and therefore can be suitable for use in construction works.Accepted Author ManuscriptChemE/Product and Process EngineeringBT/Environmental Biotechnolog