Temperature effect on water extractability of cadmium, copper, lead and zinc from composted organic solid wastes of south-west Nigeria

Spatial and Temporal Heterogeneity of Metal Contaminants in Soils Along Two Major Roads

The concentrations of zinc, copper, lead and cadmium owing to vehicles were analyzed in roadside soils during all the four seasons from Faisalabad-Gojra road (M-4) and Gojra-Jhang road (GJR) in the Punjab, Pakistan. Results indicated that all the polluted sites along the roadside had comparatively higher metal concentrations as compared to control, nevertheless, spatio-temporal variations in metal concentrations were apparent in different soil samples. The spatial differences in metal concentrations were strongly associated with vehicle density at the Gojra Interchange site and Forest Park site along M-4 and GJR roads, respectively. Among seasons, metal ions exhibited the following order: summer > autumn > spring > winter, indicating that high temperature might have released more metal ions. The metals were recorded in contaminated soil in the order of Zn > Cu > Pb > Cd along both roads. This investigation emphasizes the need for proper environmental management particularly the improvement of roads and proper checking of vehicles running on these regards.

Lead Concentrations in Soils and Some Wild Plant Species Along Two Busy Roads in Pakistan

This study assessed the level of Pb in soil and five wild plant species (Calotropis procera, Datura alba, Parthenium hysterophorus, Cenchrus ciliaris and Ricinus communis) during all the four seasons. Two busy roads varying in age and traffic volume were selected i.e., Faisalabad-Sargodha road (FSR) and Pindi Bhattian to Lillah (M-2) in the Punjab, Pakistan. Results showed raised levels of Pb in both plants and soil samples along both roads. The range of Pb concentration in plants was 0.08-3.98 and 1.95-4.74 mg kg^- 1 for soil. Higher Pb contamination was recorded along FSR road as compared to M-2. Among seasons, the higher Pb concentration was found during summer, probably due to very high temperature. Among all the plants studied, Calotropis procera accumulated the highest level (3.98 mg kg^- 1 dry wt.) of Pb; Thus, it can be used as good biomonitor/phytoremediator at Pb contaminated areas.

Biomass ash reutilisation as an additive in the composting process of organic fraction of municipal solid waste

In this work the effects of selected types of biomass ash on the composting process and final product quality were studied by conducting a 96-day long experiment where the source separated organic fraction of municipal waste, mixed with wood prunings that served as bulking agent, was added with 0%, 2%, 4% and 8% wt/wt of biomass ash. The evolution over time of the main process parameters was observed, and the final composts were characterised. On the basis of the results, both the composting process and the quality of the final product were improved by ash addition. Enhanced volatile solids reduction and biological stability (up to 32% and 52%, respectively, as compared to the unamended product) were attained when ash was added, since ash favored the aerobic degradation by acting asa physical conditioner. In the final products, higher humification of organic matter (expressed in terms of the humification index, that was 2.25 times higher in the most-enriched compost than in the unamended one) and total Ca, K, Mg and P content were observed when ash was used. The latter aspect may influence the composts marketability positively, particularly with regards to potassium and phosphorus. The heavy metals content, that is regarded as the main environmental disadvantage when using ash asa composting additive, did not negatively affect the final composts quality. However, some other controversial effects of ash, related to the moisture and temperature values attained during the process, pH (8.8-9.2 as compared to 8.2 of the unamended compost) and electrical conductivity levels (up to 53% higher as compared to the unamended compost) in the final composts, were also observed.

Recycling of organic wastes through composting for land applications: a Nigerian experience

In-vessel composting, a contribution to sustainable solid waste management, was conducted on source-separated waste materials generated in Abeokuta city, south-west Nigeria. Feedstock (household, agricultural and municipal waste) and the resultant composts were chemically characterized using standard procedures. Identification and changes in the microbial population during composting, the effects of composting on waste volume reduction (WVR) and elemental composition of composts were evaluated. Product performance on plant growth and metal uptake were then assessed using African spinach (Amaranthus hybridus) in a screen house for 8 weeks. Metals were determined in acid digest using atomic absorption spectrometry. Compost yields and WVR ranged from 35.28 to 48.68% and 51.66 to 64.72%, respectively. Compost heavy metal (Cu, Cr, Zn, Ni, Cd and Pb) concentrations (mg kg( -1)), ranging from 0.67-0.82; 0.13-7.5; 0.001-0.22; 1.67-18.33; 6.50-17.67; and 0.83-6.00 for Cu, Pb, Cd, Ni, Cr and Zn, respectively, were within limits for class A+ composts. The effect of composting varied with element type and significantly (p < 0.05) reduced microbial population by 44.44 to 88.46%. Plant height, leaf number and biomass yield gave positive correlations (r = 0.950 to 0.977; 0.978 to 0.989 and 0.99, respectively; p < 0.05) with applied compost rate. Low-metal composts were produced but the presence of Cd and Pb in plant tissues calls for further research on the long-term effect of products on plant metal uptake in amended soils. The study is a contribution to the data bank of composting as a low technology waste management option in the developing countries.

Influence of humic acid derived from composted wastes of Nigeria origin on oxidative and antioxidant status of African mud catfish (Clarias gariepinus)

The utilization of organic fertilizer, a product of composted organic wastes, is being advocated in Nigeria as a solid waste management alternative. The application of such products near surface water could increase organic matter load of the aquatic environment, thus increasing the humic substance concentration that influence metal speciation and bioavailability in water. In this study, Humic Acid (HA), a major humic substance fraction, derived from composted organic wastes of Nigeria origin was evaluated for effects on the oxidative and antioxidant status of African Mud Catfish (Clarias gariepinus) exposed to different HA (100, 250, 500 and 1000 mg L(-1)) concentrations in static water culture. Lipid peroxidation was estimated via malondialdehyde (MDA) using thiobarbituric acid assay while oxidative stress was assessed spectrophotometrically, via superoxide dismutase (SOD), glutathione (GSH) and catalase (CAT) using standard enzymatic assay techniques. Results showed that treatments increased MDA by 20 to 70% but decreased SOD, CAT and GSH by 10 to 42.56%, 43.62 to 64.09% and 9.84 to 67.68%, respectively. Negative coefficient (r) was obtained for CAT (r = - 0.491; p > 0.10), GSH (r = - 0.551; p > 0.10) versus HA concentration but correlation was positive for MDA (r = 0.998; p = 0.012) and the latter. Study revealed humic acid-mediated oxidative stress and lipid oxidation in the fish. The adverse impact was a function of humic acid concentration and an assessment of heavy metal-humic acid mixture effect on the oxidative and antioxidant status of fresh water fish is recommended.

Potential nephrotoxicity in African mud catfish (Clarias gariepinus) following exposure to compost derived humic acid

Influence of compost-derived Humic Acid (HA) on nephrotoxicity in juvenile African mud catfish (Clarias gariepinus) was evaluated in static water culture. Fish samples were exposed to different HA concentrations (0, 100, 250, 500 and 1000 mg L(-1)) for 45 days at 5 samples per aquarium. Renal function was assessed spectrophotometrically via levels of serum albumin, measured using bromocresol green, creatinine by Jaffe method and urea by Nesslerization method. Results revealed that the mean value of albumin or urea in the exposed group (1), at each HA concentration, was lower than the value found in the control group (II). Creatinine was relatively higher in I relative to II. Significant (p < 0.05) variations for I and II were obtained at 250 to 1000 mgHA L(-1) for the three biomarkers. Relative to increasing HA concentration, decreasing albumin (0.84 to 0.43 g dL(-1): r = -0.114; p > 0.10), urea (5.21 to 1.95 mg dL(-1); r = -0.586; p > 0.10) and increasing creatinine (0.20 to 1.53 mg dL(-1): r = +0.704; p > 0.10) were recorded; r is correlation coefficient. Changes in urea were not predictive of nephrotic syndrome but alterations in albumin and creatinine revealed induced nephrotoxicity, especially at elevated HA concentrations (above 100 mg L(-1)). Overall, the effect of humic acid was dose-dependent. Further studies at various humic acid concentrations, especially below 100 mg L(-1), are required to establish the actual nephrotoxic dose.