Identification of heavy metal sources by multivariable analysis in a typical Mediterranean city (SE Spain)

Problems associated with heavy metal characterization in the majority of sites are often due to multiple sources of pollution. This work presents the results through the use of advanced statistical techniques to identify sources of soil heavy metals in a typical Mediterranean city. The multivariable analysis performed on seven metals identified four sources controlling their variability. Cr, Mn, and Ni contents were associated to soil parent materials; Cd and Pb contents were related to anthropogenic activities, specifically industrial activities and traffic; Cu content is controlled by long-term application of inorganic fertilizers in agricultural areas. Finally, zinc concentration is associated to commercial and outdoor activities in the area. These results were supported by the fact that metals associated to parent material (Cr, Mn, and Ni) were better correlated with soil lithogenic properties, while anthropogenic metals were correlated with more variable soil constituents.     

Effectiveness of three configurations of membrane bioreactors on the removal of priority and emergent organic compounds from wastewater: comparison with conventional wastewater treatments

In this work the effectiveness of membrane bioreactors as advanced treatment on the removal of emergent and priority organic compounds in wastewater treatment plants has been evaluated during a one-year monitoring study. The studied wastewater treatment plant operates with flat sheet and hollow fibre membranes in two parallel lines. Moreover, a reverse osmosis module connected in series after the hollow fibre membrane was evaluated for one month. Comparison of membrane bioreactor and conventional activated sludge treatment was also investigated, as well as the influence of the physicochemical properties of the compounds on the removal rates achieved. Sixteen pharmaceutical compounds belonging to seven therapeutic groups and eight priority organic pollutants, including linear alkylbenzene sulfonates, nonylphenol and its ethoxylates and phthalate, were monitored. The highest mean concentrations corresponded to priority organic pollutants (309 μg L(-1) of linear alkylbenzene sulfonate C(12)) followed by pharmaceutical compounds (24.5 μg L(-1) of ibuprofen). No significant difference of effectiveness was found among flat sheet and hollow fibre membranes. However, an improvement was obtained with the addition of a reverse osmosis module for most of the compounds. Biodegradation has been shown as the main route involved in the removal of organic compounds during both technologies.     

Real-world emissions of in-use off-road vehicles in Mexico

Off-road vehicles used in construction and agricultural activities can contribute substantially to emissions of gaseous pollutants and can be a major source of submicrometer carbonaceous particles in many parts of the world. However, there have been relatively few efforts in quantifying the emission factors (EFs) and for estimating the potential emission reduction benefits using emission control technologies for these vehicles. This study characterized the black carbon (BC) component of particulate matter and NOx, CO, and CO₂ EFs of selected diesel-powered off-road mobile sources in Mexico under real-world operating conditions using on-board portable emissions measurements systems (PEMS). The vehicles sampled included two backhoes, one tractor, a crane, an excavator, two front loaders, two bulldozers, an air compressor, and a power generator used in the construction and agricultural activities. For a selected number of these vehicles the emissions were further characterized with wall-flow diesel particle filters (DPFs) and partial-flow DPFs (p-DPFs) installed. Fuel-based EFs presented less variability than time-based emission rates, particularly for the BC. Average baseline EFs in working conditions for BC, NOx, and CO ranged from 0.04 to 5.7, from 12.6 to 81.8, and from 7.9 to 285.7 g/kg-fuel, respectively, and a high dependency by operation mode and by vehicle type was observed. Measurement-base frequency distributions of EFs by operation mode are proposed as an alternative method for characterizing the variability of off-road vehicles emissions under real-world conditions. Mass-based reductions for black carbon EFs were substantially large (above 99%) when DPFs were installed and the vehicles were idling, and the reductions were moderate (in the 20–60% range) for p-DPFs in working operating conditions. The observed high variability in measured EFs also indicates the need for detailed vehicle operation data for accurately estimating emissions from off-road vehicles in emissions inventories.

Implications: Measurements of off-road vehicles used in construction and agricultural activities in Mexico using on-board portable emissions measurements systems (PEMS) showed that these vehicles can be major sources of black carbon and NO_X. Emission factors varied significantly under real-world operating conditions, suggesting the need for detailed vehicle operation data for accurately estimating emissions inventories. Tests conducted in a selected number of sampled vehicles indicated that diesel particle filters (DPFs) are an effective technology for control of diesel particulate emissions and can provide potentially large emissions reduction in Mexico if widely implemented.     

Optimization of Microwave-Assisted and Conventional Heating Comparative Synthesis of Poly(lactic acid) by Direct Melt Polycondensation from Agroindustrial Banana (Musa AAA Cavendish) and Pineapple (Ananas comosus) Fermented Wastes

In Costa Rica, a lot of pineapple (Ananas comosus) and banana (Musa AAA) agroindustrial residues are generated each year. These residues can be used to obtain l-lactic acid by fermentation, ultrafiltration and electrodialysis. Poly(l-lactic acid) (PLLA) is a biodegradable and renewable polyester with many industrial and biomedical applications. There is a growing interest to improve the energetic efficiency of the synthesis of PLLA, because the main issue to produce this polymer is the high productive cost compared with petrochemical traditional commodities. In this research, the synthesis of PLLA through two different techniques was compared: microwave-assisted and conventional heating. On microwave synthesis the best results were obtained using lower temperatures and lower reaction times than the conventional heated synthesis. The reaction time was reduced from 15 h by conventional heating to 4.5 h using microwave-assisted synthesis.     

Biological activity in metal-contaminated calcareous agricultural soils: the role of the organic matter composition and the particle size distribution

Organic matter (OM) plays a key role in microbial response to soil metal contamination, yet little is known about how the composition of the OM affects this response in Mediterranean calcareous agricultural soils. A set of Mediterranean soils, with different contents and compositions of OM and carbonate and fine mineral fractions, was spiked with a mixture of Cd, Cu, Pb, and Zn and incubated for 12 months for aging. Microbial (Biolog Ecoplates) and enzyme activities (dehydrogenase, DHA; β-galactosidase, BGAL; phosphatase, PHOS; and urease, URE) were assessed and related to metal availability and soil physicochemical parameters. All enzyme activities decreased significantly with metal contamination: 36–68 % (DHA), 24–85 % (BGAL), 22–72 % (PHOS), and 14–84 % (URE) inhibitions. Similarly, catabolic activity was negatively affected, especially phenol catabolism (～86 % compared to 25–55 % inhibition for the rest of the substrates). Catabolic and DHA activities were negatively correlated with ethylenediaminetetraacetic acid (EDTA)-extractable Cd and Pb, but positively with CaCl₂, NaNO₃, and DTPA-extractable Cu and Zn. Soluble OM (water- and hot-water-soluble organic C) was positively related to enzyme and catabolic activities. Recalcitrant OM and fine mineral fractions were positively related to BGAL and PHOS. Conversely, catabolic activity was negatively related to clay and positively to silt and labile OM. Results indicate that the microbial response to metal contamination is highly affected by texture and OM composition.     

Carbon mineralization,microbial activity and metal dynamics in tailing ponds amended with pig slurry and marble waste

A field experiment was set up in Cartagena-La Unión Mining District, SE Spain, aimed at evaluating the short-term effects of pig slurry (PS) amendment alone and together with marble waste (MW) on organic matter mineralization, microbial activity and stabilization of heavy metals in two tailing ponds. These structures pose environmental risk owing to high metals contents, low organic matter and nutrients, and null vegetation. Carbon mineralization, exchangeable metals and microbiological properties were monitored during 67 d. The application of amendments led to a rapid decrease of exchangeable metals concentrations, except for Cu, with decreases up to 98%, 75% and 97% for Cd, Pb and Zn, respectively. The combined addition of MW + PS was the treatment with greater reduction in metals concentrations. The addition of PS caused a significant increase in respiration rates, although in MW + PS plots respiration was lower than in PS plots. The mineralized C from the pig slurry was low, approximately 25–30% and 4–12% for PS and MW + PS treatments, respectively. Soluble carbon (Csol), microbial biomass carbon (MBC) and β-galactosidase and β-glucosidase activities increased after the application of the organic amendment. However, after 3 d these parameters started a decreasing trend reaching similar values than control from approximately day 25 for Csol and MBC. The PS treatment promoted highest values in enzyme activities, which remained high upon time. Arylesterase activity increased in the MW + PS treatment. Thus, the remediation techniques used improved soil microbiological status and reduced metal availability. The combined application of PS + MW reduced the degradability of the organic compounds.     

Kinetic studies of endosulfan photochemical degradations by ultraviolet light irradiation in aqueous medium

Kinetic studies of endosulfan photochemical degradation in controlled aqueous systems were carried out by ultraviolet light irradiation at λ = 254 nm. The photolysis of (α + β: 2 + 1) endosulfan, α-endosulfan and β-endosulfan were first-order kinetics. The observed rate constants obtained from linear least-squares analysis of the data were 1 × 10^?4 s^?1; 1 × 10^?4 s^?1; and 2 × 10^?5 s^?1, respectively, and the calculated quantum yields (φ) were 1, 1 and 1.6, respectively. Preliminary differential pulse polarographic (DPP) analysis allowed to observe the possible endosulfan photochemical degradation pathway. This degradation route involves the formation of the endosulfan diol, its transformation to endosulfan ether and finally the ether's complete degradation by observing the potential shifts.     

Evaluation of a multiresidue method for pesticides in cereals using supercritical fluid extraction and gas chromatographic detection

Supercritical fluid extraction (SFE) was evaluated to be applied for residue analysis of 22 gas chromatography/electron capture detector-nitrogen phosphorus detector (GC/ECD-NPD) amenable pesticides in rice, wild rice and wheat. Samples were extracted with supercritical carbon dioxide at 200 atm pressure and 50°C temperature, using methanol as a static modifier. Mean recoveries obtained with the proposed SFE method at two spiking levels with four replicates per level are compared with those obtained with an ethyl acetate-based solvent extraction/gel permeation chromatography (GPC) clean up method. Both methods gave consistent high recoveries for almost all the pesticides from all the commodities with overall mean recoveries higher than 70% with relative standard deviations lower than 20%. Remarkable exceptions were captafol and dimethoate, for which low and/or non-reproducible recoveries were obtained with the SFE method. Residue levels determined with both methods in nine different incurred samples of wheat, containing some of the studied pesticides, were very similar, but, in all cases, slightly higher levels were determined with the SFE method.     

Effect of sunn hemp (Crotalaria juncea L.) cutting date and planting density on weed suppression in Georgia,USA

A field study was conducted in 2008 and 2009 at the USDA, ARS, Plant Genetic Resources Conservation Unit in Griffin, GA, to investigate weed suppression by sunn hemp (Crotalaria juncea L). The objectives were to (1) evaluate the effects of apical meristem removal (AMR) at three dates [5, 6, and 7 wks after planting (WAP) on May 14, 2008 and May 21, 2009] and (2) assess the impact of seeding rates (11, 28, and 45 kg ha^?1) on weed biomass reduction. Weed species were identified at 4, 8, and 12 wks after sunn hemp planting. Sunn hemp cutting date had no significant effect on weed suppression in 2008 but significant differences for grass weeds at 4, 8, and 12 WAP and for yellow nutsedge at 8 and 12 WAP did occur when compared to the control in 2009. In comparison to the sunn hemp-free control plot in 2009, all three seeding rates had reduced grass weed dry weights at 4, 8, and 12 WAP. The total mass of yellow nutsedge when grown with sunn hemp was reduced compared to the total mass of yellow nutsedge grown in the weedy check for all seeding rates at 8 and 12 WAP. Lower grass weed biomass was observed by 12 WAP for cutting dates and seeding rates during 2008 and 2009. Sunn hemp cutting date and seeding rate reduced branch numbers in both years. The reduction in sunn hemp seeding rates revealed a decrease in weed populations.     

Residues levels of organochlorine pesticide in cow's milk from industrial farms in Hidalgo,Mexico

A survey was carried out from 2008 to 2010 to determine the concentrations of 16 organochlorine pesticide residues (OPRs) from Tizayuca, Hidalgo, Mexico. Organochlorine residue determinations were made from milk fat, using chromatographic cleanup and analysis by gas chromatography with an electron capture detector. The OPR concentrations found were from below the detection limit (DL) to 0.91 ng g^?1 in 2008, DL to 0.38 ng g^?1 in 2009 and DL to 0.59 ng g^?1 in 2010. In general concentrations of organochlorine pesticides were higher in the wet season (3.37 ng g^?1 and 4.79 ng g^?1) than the dry season (1.92 ng g^?1 and 2.71 ng g^?1) for 2009 and 2010, due to control of pests in the pasture and sheds. According to Codex Alimentarius regulations, individual pesticides did not exceed the permissible limits, which for example were 10 μg kg^?1 for alpha hexachlorocyclohexane (HCH) and endosulfan I, 20 μg kg^?1 for p,p’-DDT, and 6 μg kg^?1 for dieldrin, endrin and heptachlor. A reduction of organochlorine pesticide concentrations in cow's milk was noted, indicating that the Mexican government has achieved reduction or elimination of some organochlorine pesticides in response to global agreements on persistent organic pollutants.