Data on heavy metals content and biochar toxicity in a pristine tropical agricultural soil.

Accumulation of heavy metals results in soil degradation and impairs the normal functioning of ecosystems. Thus, monitoring of heavy metals is essential in both pristine and polluted soils. Concentrations of heavy metals were determined in a pristine tropical agricultural soil using acid digestion procedures. The soil samples were also analyzed for physico-chemical parameters and biochar toxicity to earthworms. Data shows that the soil is acidic, with low organic matter content. The level of heavy metals ranged from <0.06±0.0 to 595.8±2.8 µg g-1. However, the concentrations were found to be below the soil regulatory standards of heavy metals in agricultural soils. Furthermore, increased addition of biochar to the soil caused toxic effect on earthworms over a 90 d biochar-soil contact time. The data provides baseline information of heavy metals in pristine agricultural soils from the region, and the effect of biochar amendments on tropical soils.

Influence of biochar aged in acidic soil on ecosystem engineers and two tropical agricultural plants.

Biochar amendment to soil is predicted globally as a means to enhance soil health. Alongside the beneficial result on soil nutrient availability and retention, biochar is presumed to increase soil macro / microbiota composition and improve plant growth. However, evidence for such an effect remains elusive in many tropical agricultural soils. The influence of biochar aged in soil was assessed on soil microbiota, macrobiota (Eudrilus eugeniae), seedling emergence and early plant growth of Oryza sativa and Solanum lycopersicum in tropical agricultural soil, over a 90 d biochar-soil contact time. Results showed negative impacts of increased loading of biochar on the survival and growth of E. eugeniae. LC50 and EC50 values ranged from 34.8% to 86.8% and 0.9-23.7% dry biochar kg-1 soil, over time. The growth of the exposed earthworms was strongly reduced (R2 = -0.866, p < 0.05). Biochar significantly increased microbiota abundance relative to the control soil (p < 0.001). However, fungal population was reduced by biochar addition. Biochar application threshold of 10% and 5% was observed for (O. sativa) and (S. lycopersicum), respectively. Furthermore, the addition of biochar to soil resulted in increased aboveground (shoot) biomass (p < 0.01). However, the data revealed that biochar did not increase the belowground (root) biomass of the plant species during the 90 d biochar-soil contact time. The shoot-to-root-biomass increase indicates a direct toxic influence of biochar on plant roots. This reveals that nutrient availability is not the only mechanism involved in biota-biochar interactions. Detailed studies on specific biota-plant-responses to biochars between tropical, temperate and boreal environments are needed to resolve the large variations and mechanisms behind these effects.

Western blot-indeterminate results in Nigerian patients HIV serodiagnosis: the clinical and public health implication.

The clinical and public health implication of HIV Western blot (WB) indeterminate results is yet to be appraised in sub-Saharan Africa, including Nigeria. Using HIV Tri Line Test enzyme-linked immunosorbent assay (ELISA), 1286 patients (600 males and 686 females; age range, 5-60 years) with symptoms suggestive of HIV infection were screened. A total of 1020 (79.3%, 95% confidence interval [CI] 76.8-81.5) of the patients comprising of 514 (85.7%) males and 506 (73.8%) females were HIV seropositive and the difference was statistical significantly (chi(2) = 5.72, df = 1, p < 0.05). Western blot analysis of sera from the 1020 HIV-seropositive individuals using the BIO-RAD NEW LAV-BLOT I specifying World Health Organization (WHO) interpretive criteria, confirmed the HIV serostatus of 815 (79.9%, 95% CI, 77.4-82.4) of them with 205 (20.1%, 95% CI, 17.6-22.6) individuals having indeterminate results consisting of either; 1 env +/- gag +/- pol, gag + pol, gag only or pol only. Of these, 102 (19.8%) were males and 103 (20.4%) were females. Patients aged 11-20 years old recorded the highest percentage of indeterminate results (31.7%, 95% CI, 20.2-43.2) while those aged 21-30 years recorded the least (14.2%, 95% CI, 10.6-17.8) and the difference was statistically significant (chi(2) = 15.73, df = 5, p < 0.05). Result confirmed the limitation of Western blot assays in HIV confirmatory serodiagnosis. After obtaining HIV indeterminate Western blot result, clinicians should consider the total profile for the patient, reassess risk factors for HIV infection, perform a HIV retesting at 3-month intervals for 6 months or use an alternate HIV antibody confirmatory assay and running antibody tests for other human retroviruses.