The potential persistence and migration of 14 antibiotics comprising sulfonamides, fluoroquinolones, macrolides and tetracyclines were conducted using a 50-d recirculating flume study supported by batch attenuation experiments with spiked concentrations. The study demonstrated that photodegradation was the dominant attenuation process for these antibiotics in the water environment. The half-lives of 2–26 d were in order of sulfadiazine > sulfadimethoxine > sulfamerazine > sulfamethoxazole > sulfamethazine > sulfathiazole > ofloxacin > enrofloxacin > norfloxacin > ciprofloxacin > erythromycin > tetracycline > roxithromycin > oxytetracycline. These modest half-lives meant that the antibiotics were predicted to travel 30–400 km down a typical river before half the concentration would be lost. All antibiotics were detected on the surface sediment in the flume study. Under hyporheic exchange, some of them continually migrated into the deeper sediment and also the sediment pore water. All fluoroquinolones were detected in the sediments. The sulfonamides were detected in the pore water with relatively high concentrations and frequencies. Sulfadiazine, sulfamethazine and sulfathiazole in the upper layer pore water were found to be approaching equilibrium with the surface water. The high presence of sulfonamides in the pore water indicated that their high mobility and persistence potentially pose a risk to hyporheic zone.

With the recovery of whale populations, carcass strandings on beaches are growing. Beach burial is a common management option for stranded carcasses. However, communities fear shark attraction following leachate transport to the ocean via submarine groundwater discharge. Here, a sediment column mesocosm experiment indicated that carcasses can be a localised source of dissolved organic carbon (DOC), phosphate and ammonium to groundwater. The spatial reach of the leachate plume was <2.5 m, while the temporal stabilisation occurred over 100–300 days. No significant chemical signals were observed under a beach-buried carcass, implying effective attenuation of decomposition plumes. For beaches with conditions similar to our one-directional, fast-flowing sediment experiment generating extreme groundwater contamination, it is unlikely that any leachate from a whale carcass would reach the ocean if buried >25 m onshore. Therefore, carcass leachate plumes would only potentially attract sharks to the surf under specific conditions not experienced during our experiments.

This study proposes a new methodology to study contamination, bioavailability and mobility of metals (Cd, Cu, Ni, Pb, and Zn) using chemical and geostatistics approaches in marine sediments of Sepetiba Bay (SE Brazil). The chemical model of SEM (simultaneously extracted metals)/AVS (acid volatile sulfides) ratio uses a technique of cold acid extraction of metals to evaluate their bioavailability, and the geostatistical model of attenuation of concentrations estimates the mobility of metals. By coupling the two it was observed that Sepetiba Port, the urban area of Sepetiba and the riverine discharges may constitute potential sources of metals to Sepetiba Bay. The metals are concentrated in the NE area of the bay, where they tend to have their lowest mobility, as shown by the attenuation model, and are not bioavailable, as they tend to associate with sulfide and organic matter originated in the mangrove forests of nearby Guaratiba area.

Oil spills in the Niger Delta could exert environmental pressures on the soil component. We investigated the impacts of oil spills and the effect of the Enhanced Natural Attenuation (ENA) remediation method on contaminated soil and resident microbial populations in the Odhiaje community in Rivers State, Nigeria. Soil samples for microbiological studies were collected weekly during a 17-week remediation period, while those for edaphic parameters were taken before and after remediation, all at 4 sampling points (SPs). Serial dilution of the oil-impacted soils for microbial density enumeration was carried out according to standard methods. Results revealed that mean concentrations of Total Petroleum Hydrocarbon Contents (THC) (Sig.value = 0.009), SO42- ions (Sig.value = 0.001), and sand compositions (Sig.value = 0.045) all differed markedly across the sampling points at p<0.05. Mean levels of EC (Sig.tvalue = 0.039) and ΣN (Sig.tvalue = 0.058) & K+ ions (Sig.tvalue = 0.004) differed significantly before and after the remediation exercise at the 95% confidence interval. Application of nutrients was rapidly accompanied by microbial population increases, leading to the consumption of oil contaminants in soils to levels comparable to control over the remediation period. Total Heterotrophic Bacteria counts correlated with pH (r = 0.501) and SO42- ions (r = 0.500) (p<0.05), and K+ ions (r = -0.800) (p<0.01); Total Heterotrophic Fungi correlated with pH (r = 0.520) (p<0.05), and Mg2+ ions (r = 0.820) (p<0.01); Hydrocarbon Utilizing Bacteria correlated with available P (r = 0.530) and silt composition (r = -0.504) (p<0.05), and K+ (r = 0.626) and Mg2+ ions (r = 0.733) (p<0.01); and Hydrocarbon Utilizing Fungi correlated with K+ (r = 0.500) & Mg2+ ions (r = 0.506) (p<0.05). Results indicate improvement in C/N ratios and effectiveness of the current cost-effective bioaugmentation technique in the restoration of arable soil productivity in the Odhiaje community.