Predicting bioremediation of hydrocarbons: Laboratory to field scale

There are strong drivers to increasingly adopt bioremediation as an effective technique for risk reduction of hydrocarbon impacted soils. Researchers often rely solely on chemical data to assess bioremediation efficiently, without making use of the numerous biological techniques for assessing microbial performance. Where used, laboratory experiments must be effectively extrapolated to the field scale. The aim of this research was to test laboratory derived data and move to the field scale. In this research, the remediation of over thirty hydrocarbon sites was studied in the laboratory using a range of analytical techniques. At elevated concentrations, the rate of degradation was best described by respiration and the total hydrocarbon concentration in soil. The number of bacterial degraders and heterotrophs as well as quantification of the bioavailable fraction allowed an estimation of how bioremediation would progress. The response of microbial biosensors proved a useful predictor of bioremediation in the absence of other microbial data. Field-scale trials on average took three times as long to reach the same endpoint as the laboratory trial. It is essential that practitioners justify the nature and frequency of sampling when managing remediation projects and estimations can be made using laboratory derived data. The value of bioremediation will be realised when those that practice the technology can offer transparent lines of evidence to explain their decisions.     

Effects of sewage sludge amendment on heavy metal accumulation and consequent responses of Beta vulgaris plants

Use of sewage sludge, a biological residue produced from sewage treatment processes in agriculture is an alternative disposal technique of waste. To study the usefulness of sewage sludge amendment for palak (Beta vulgaris var. Allgreen H-1), a leafy vegetable and consequent heavy metal contamination, a pot experiment was conducted by mixing sewage sludge at 20% and 40% (w/w) amendment ratios to the agricultural soil. Soil pH decreased whereas electrical conductance, organic carbon, total N, available P and exchangeable Na, K and Ca increased in soil amended with sewage sludge in comparison to unamended soil. Sewage sludge amendment led to significant increase in Pb, Cr, Cd, Cu, Zn and Ni concentrations of soil. Cd concentration in soil was found above the Indian permissible limit in soil at both the amendment ratios.

The increased concentration of heavy metals in soil due to sewage sludge amendment led to increases in heavy metal uptake and shoot and root concentrations of Ni, Cd, Cu, Cr, Pb and Zn in plants as compared to those grown on unamended soil. Accumulation was more in roots than shoots for most of the heavy metals. Concentrations of Cd, Ni and Zn were more than the permissible limits of Indian standard in the edible portion of palak grown on different sewage sludge amendments ratios. Sewage sludge amendment in soil decreased root length, leaf area and root biomass of palak at both the amendment ratios, whereas shoot biomass and yield decreased significantly at 40% sludge amendment. Rate of photosynthesis, stomatal conductance and chlorophyll content decreased whereas lipid peroxidation, peroxidase activity and protein and proline contents, increased in plants grown in sewage sludge-amended soil as compared to those grown in unamended soil.

The study clearly shows that increase in heavy metal concentration in foliage of plants grown in sewage sludge-amended soil caused unfavorable changes in physiological and biochemical characteristics of plants leading to reductions in morphological characteristics, biomass accumulation and yield. The study concludes that sewage sludge amendment in soil for growing palak may not be a good option due to risk of contamination of Cd, Ni and Zn and also due to lowering of yield at higher mixing ratio.     

In situ assays with tropical cladocerans to evaluate edge-of-field pesticide runoff toxicity

Tropical regions’ economy is usually based on agriculture, which involves an intensive use, and even frequent overuse, of pesticides. Nevertheless, not much research has been done on the impact of pesticides on tropical aquatic ecosystems, which are often contaminated by runoff-related pesticide inputs due to unpredictable and torrential rainfalls. This study aimed to: (i) adapt and evaluate a short-term sublethal in situ assay using post-exposure feeding as an endpoint, to the tropical cladoceran species Diaphanosoma brachyurum (collected at the Pedra do Cavalo dam in the Paraguaçu River basin, Bahia, Brazil), and, (ii) assess the role of the standard species Daphnia magna as an adequate laboratory surrogate. Lethal and sublethal (post-exposure feeding) responses were assessed for the two species. To evaluate these responses under environmentally realistic exposure conditions, a runoff event was simulated in an agricultural area previously contaminated with different deltamethrin concentrations. The resultant runoff water was used to set up microcosms with different dilutions, simulating the entrance of runoff water in an adjacent lentic system. An in situ assay with D. brachyurum was performed inside the microcosms, allowing to discriminate the effects due to deltamethrin from those due to other potential stressors associated with the experimental design (e.g. organism handling, load of suspended particles, microcosm design). Water samples were collected from microcosms to conduct a laboratory assay with D. magna. The in situ methodologies revealed to be suitable to conduct assays with D. brachyurum under tropical conditions, since all exposed organisms were successfully retrieved from the chambers. Furthermore, none of the potential stressors associated with the experimental design influenced the daphnids’ performance. The tropical cladoceran species, exposed under more realistic conditions, revealed to be more sensitive than the laboratory standard species: lethal effects were only observed for D. brachyurum and sublethal effects were noticed at a lower deltamethrin concentration for this species than for D. magna.     

Perfluorinated compounds in the Pearl River and Yangtze River of China

A total of 14 perfluorinated compounds (PFCs) were quantified in river water samples collected from tributaries of the Pearl River (Guangzhou Province, south China) and the Yangtze River (central China). Among the PFCs analyzed, perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) were the two compounds with the highest concentrations. PFOS concentrations ranged from 0.90 to 99 ng/l and <0.01–14 ng/l in samples from the Pearl River and Yangtze River, respectively; whereas those for PFOA ranged from 0.85 to 13 ng/l and 2.0–260 ng/l. Lower concentrations were measured for perfluorobutane sulfonate (PFBS), perfluorohexane sulfonate (PFHxS), perfluorooctanesulfoamide (PFOSA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorononaoic acid (PFNA), perfluorodecanoic acid (PFDA), and perfluoroundecanoic acid (PFUnDA). Concentrations of several perfluorocarboxylic acids, including perfluorododecanoic acid (PFDoDA), perfluorotetradecanoic acid (PFTeDA), perfluorohexadecanoic acid (PFHxDA) and perfluorooctadecanoic acid (PFOcDA) were lower than the limits of quantification in all the samples analyzed. The highest concentrations of most PFCs were observed in water samples from the Yangtze River near Shanghai, the major industrial and financial centre in China. In addition, sampling locations in the lower reaches of the Yangtze River with a reduced flow rate might serve as a final sink for contaminants from the upstream river runoffs. Generally, PFOS was the dominant PFC found in samples from the Pearl River, while PFOA was the predominant PFC in water from the Yangtze River. Specifically, a considerable amount of PFBS (22.9–26.1% of total PFC analyzed) was measured in water collected near Nanjing, which indicates the presence of potential sources of PFBS in this part of China. Completely different PFC composition profiles were observed for samples from the Pearl River and the Yangtze River. This indicates the presence of dissimilar sources in these two regions.     

Dioxin formation in pulp and paper mills of India

Samples of effluents, sludge, pulp, final products (paper) and soil were collected from the identified pulp and paper mills in India. The samples were analysed for 2,3,7,8-tetrachloro-dibenzo-p-dioxin (2,3,7,8-TCDD) and other dioxin congeners and precursors. Pulp and paper mills using chlorine for the bleaching process showed the presence of 2,3,7,8-TCDD in effluent samples. In the effluent and pulp samples from mills where chlorine dioxide was used as a bleaching agent, the 2,3,7,8-TCDD congener ranged from below the detection limit 0.05 to 0.12 ngL⁻¹/ngg⁻¹. The relative standard deviation of reproducibility and the percent recovery of 2,3,7,8-TCDD were 2.07 and 82.4% in pulp and 2.8 and 92% in effluent, respectively. The 1,3,6,8-TCDD was the only other major dioxin congener found in the treated and untreated effluent and sludge samples. However, dichlorobenzene, trichlorophenyl, and hexachlorobiphenyl were detected in all samples. The formation of dioxins can be minimised by replacing chlorine with chlorine dioxide in bleaching processes in pulp and paper mills.     

Lichen and moss bags as monitoring devices in urban areas. Part II: trace element content in living and dead biomonitors and comparison with synthetic materials

Lobes of the lichen Pseudevernia furfuracea (L.) Zopf and shoots of the moss Hypnum cupressiforme Hedw. were subjected to different treatments (water washing, oven drying, HNO3 washing, NH4-oxalate extraction) to assess the influence of vitality on accumulation efficiency, during a 6-week exposure in bags in two Italian cities, Trieste and Naples. No trend emerged between treatments, in terms of accumulation ability, for major and trace elements. Only water-washed lichens showed an increased C and N content after exposure in both cities. Element concentrations generally reached higher values in mosses than in lichens, especially for Al, Fe, and Zn (both cities), and for Cu, Mg and Na (Naples). Surface development strongly influenced accumulation capacity of the biomonitors. Quartzose and cation exchange filters revealed, on a weight basis, a poor performance. In urban environments, surface interception of atmospheric particulate seems to play a major role in accumulation, irrespective of organism vitality.     

Municipal waste compost as an alternative to cattle manure for supplying potassium to lowland rice

The importance of the use of potassium in agriculture is increasing in South Asia for making most productive use of the nutrient in terms of economic returns. Nutrient supply traditionally by cattle manure is constrained by its insufficient availability. Municipal waste compost may be an alternative source of nutrient supplements. Field experiments were conducted at the Experimental Farm of Calcutta University, West Bengal, India during the wet seasons of 1997, 1998 and 1999 on flooded lowland rice. Potassium fractions in municipal waste compost and cattle manure were determined by sequential extraction and also the potassium uptake by rice to compare the effectiveness of municipal waste compost with traditional manure. Potassium was significantly bound to the organic matter in municipal waste compost. Potassium uptake by rice grain and straw increased significantly with the combined application of organics and fertilizers and it was higher in grain than in straw. Water-soluble and non-exchangeable potassium contents of municipal waste compost and cattle manure were highly correlated with the uptake of potassium by straw and grain. Exchangeable and residual potassium were also significantly correlated with the uptake of potassium by straw and grain of rice. Much higher uptake of K in rice straw and rain resulted from applying the manures in conjunction with fertilizers than when applied singly.     

Pentachlorophenol association with fulvic acids from recycled wastes

The apparent water solubility of pentachlorophenol was measured at pH=6 and at 25 degrees C in pure water, aqueous solutions of three salts (NaCl, KNO(3) and CaCl(2) at 0.010, 0.10 and 1.0M) and in aqueous solutions of three fulvic acids samples extracted from a natural soil (sFA), composted sewage sludge (csFA) and composted livestock's material (lsFA). A solubility enhancement method was developed for the measurement of partition coefficients (K(oc), L/kg organic carbon). Pentachlorophenol associates strongly with the fulvic acid samples and the calculated K(oc) were the following (averages and standard deviations): (sFA) (211+/-22) x 10(2), (csFA) (253+/-26) x 10(2), (lsFA) (235+/-10) x 10(2). For comparison purposes the K(oc) for pyrene were also calculated for the three FA samples and were the following: (sFA) (119+/-10) x 10(2), (csFA) (239+/-21) x 10(2), (lsFA) (92+/-10) x 10(2). The analysis of variance (one-way ANOVA) of the effect of the type of FA sample on the solubilization of pentachlorophenol and pyrene shows that this factor causes significant differences on the aqueous solubilization of these two organic substances.     

Differential responses of the freshwater wetland species Juncus effusus L. and Caltha palustris L. to iron supply in sulfidic environments

Sulfur pollution can lead to serious problems in freshwater wetlands, including phosphorus eutrophication and sulfide toxicity. We tested the effects of anaerobic iron-rich groundwater discharge in fens, simulated by iron injection, on two characteristic species (Juncus effusus and Caltha palustris) in a sulfidic environment. Biomass production of C. palustris roots showed an optimum response to the combined addition of iron and sulfide, with highest values at intermediate concentrations of both substances. Iron deficiency apparently occurred at low iron concentrations, while at high iron concentrations, growth was decreased. For J. effusus, in contrast, no toxic effects were found of both iron and sulfide. This could be explained by larger radial oxygen loss (ROL) of J. effusus and could not be explained by differences in phosphorous concentrations. The results of our experiments confirm that iron-rich groundwater discharge has the potential to affect vegetation composition through toxicity modification in sulfidic environments.