Nitrogen assimilation by phytoplankton and other microorganisms in the surface waters of the central North Pacific Ocean

Assimilation rates of ¹⁵N-labelled ammonium, urea, and nitrate by plankton in the upper euphotic zone were measured in 2 summer, 2 winter, and 1 spring cruise in the central North Pacific Ocean. Average rates of ammonium plus urea assimilation could not be determined precisely, but were estimated to be 7 to 25 g-at. N m^-3 day^-1. Indirect evidence suggested that non-photosynthetic microorganisms contributed to these rates. Nitrate assimilation was negligible in the upper waters considered in this report (above the chlorophyll maximum and the nutricline). Potential, nitrate-saturated rates were in the range 1 to 8 g-at. N m^-3 day^-1. Seasonal comparison showed lowest rates of both carbon and nitrogen assimilation rates per chlorophyll a in winter.     

Case study: Voluntary agreements in environmental management at formosa plastics

Three agreements addressing environmental and safety performance, zero discharge of wastewater and sustainable development have been signed between Formosa Plastics Corporation, Texas (Formosa Plastics), and its former adversaries. The key element of the agreements is the improvement of the affected community. These agreements go beyond public information and beyond procedures for public participation. They have led to meaningful public participation and partnership and are unique in this respect. The following article explores the setup and results of each agreement. The initial agreement, the Blackburn-Formosa Agreement, signed in 1992, set the stage for subsequent partnerships. The Wilson-Formosa Zero Discharge Agreement followed in 1994. Finally, the Sustainable Development Agreement was signed by Jim Blackburn, Diane Wilson, and Formosa Plastics in late 1997. These agreements have proven very successful in avoiding disputes and helping improve company performance in environmental and safety issues. In many respects, these agreements offer a model for others in working with an affected community.     

Simulated and experimental evaluation of factors affecting the rate and extent of reductive dehalogenation of chloroethenes with glucose

Carbohydrates such as molasses are being added to aquifers to serve as electron donors for reductive dehalogenation of chloroethenes. Glucose, as a model carbohydrate, was studied to better understand the processes involved and to evaluate the effectiveness for dehalogenation of different approaches for carbohydrate addition. A simulation model was developed and calibrated with experimental data for the reductive dehalogenation of tetrachloroethene to ethene via cis-1,2-dichloroethene. The model included fermentors that convert the primary donor (glucose) into butyrate, acetate and hydrogen, methanogens, and two separate dehalogenator groups. The dehalogenation groups use the hydrogen intermediate as an electron donor and the different haloethenes as electron acceptors through competitive inhibition. Model simulations suggest first that the initial relative population size of dehalogenators and H(2)-utilizing methanogens greatly affects the degree of dehalogenation achieved. Second, the growth and decay of biomass from soluble carbohydrate plays a significant role in reductive dehalogenation. Finally, the carbohydrate delivery strategies used (periodic versus batch addition and the time interval between periodic addition) greatly affect the degree of dehalogenation that can be obtained with a given amount of added carbohydrate.     

Results and evaluation of the first study of organochlorine contaminants (PCDDs, PCDFs, PCBs and DDTs), heavy metals and metalloids in birds from Baja California, México

Organochlorine compounds (OCs) including polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p-p'-DDE), heavy metals (Pb, Cd, Zn, Cu), and arsenic were measured in house sparrows (Passer domesticus) and common ground doves (Columbina passerina) from Baja California Sur, México. Concentrations of PCDD/Fs were low, with 21 pg/g for house sparrows, and 7.7 pg/g for common ground doves. Non-ortho-PCB concentrations in house sparrow and common ground doves were 58 and 254 pg/g, respectively, and are within the highest concentrations reported in species that are in the low levels of food webs. The major differences in organochlorine levels between species were found for ortho-PCBs and DDTs. ortho-PCB levels were higher in the seedeater species, whereas DDT levels were higher in the omnivorous species. Heavy metal levels were far below those associated with negative effects.     

Effects of a mixture of tetracyclines to Lemna gibba and Myriophyllum sibiricum evaluated in aquatic microcosms

The impact of a mixture of oxytetracycline, chlortetracycline, tetracycline and doxycycline on Myriophyllum sibiricum and Lemna gibba was investigated using fifteen 12,000-L microcosms (k=5, n=3). Significant concentration-response relationships were only found for M. sibiricum, where dry mass was 69, 47, 30, and 7% of controls at respective treatment concentrations of 0.080, 0.218, 0.668, and 2.289 micromol/L. Somatic endpoints were strongly and negatively correlated with percent light transmission, except plant length, which was positively correlated. Treated microcosms experienced a reduction in the percent of surface irradiance penetrating the water column as high as 99.8% at a depth of 70 cm, relative to controls. Position relative to the water column was likely responsible for the differential effects observed between floating (L. gibba) and submerged (M. sibiricum) species of macrophytes. A hazard quotient assessment of the lowest EC10 value indicated significant risk, exceeding the critical HQ value, but not the lowest EC25 value.     

The economic benefits of fulfilling the World Health Organization’s limits for particulates: A case study in Algeciras Bay (Spain)

Algeciras Bay is an important industrial and port zone in the south of Spain whose pollution by particulate matter surpasses the threshold levels recommended by the World Health Organization (WHO) in its 2005 Guide on Air Quality. This study analyses the mortality avoided and the economic benefit which would be derived from a reduction of the pollution of PM2.5 and PM10 to the levels recommended by the WHO in Algeciras Bay in the period 2005-2015. The analysis carried out shows that the industrial zones, such as Los Barrios and San Roque, are those which have greater levels of pollution and in which the relative risk is greater. The calculations for Algeciras Bay between 2000 and 2015 show 182 deaths which would be avoided if the particulate matter pollution were reduced to the levels recommended by the WHO. Likewise, the economic valuation which this impact has on health is carried out through two concepts: the cost of illness and the Value of Statistical Life (VSL). The result shows that the economic benefit that would come out with the cost of illness valuation is 5,329,110€ and from the VSL is 414,787,113€.

Implications: PM_2.5 has a greater concentration in industrial localities and is linked to the industrial activity. When the particulate matter pollution is reduced to the levels recommended by the WHO in an industrialised area such as Algeciras (Spain), 182 deaths which would be avoided. The result shows that the economic benefit that would come out with the cost of illness valuation is 5,329,110€ and from the value of statistical life is 414,787,113€.     

Heavy metal extractable forms in sludge from wastewater treatment plants

The analysis of heavy metals is a very important task to assess the potential environmental and health risk associated with the sludge coming from wastewater treatment plants (WWTPs). However, it is widely accepted that the determination of total elements does not give an accurate estimation of the potential environmental impact. So, it is necessary to apply sequential extraction techniques to obtain a suitable information about their bioavailability or toxicity. In this paper, a sequential extraction scheme according to the BCR's guidelines was applied to sludge samples collected from each sludge treatment step of five municipal activated sludge plants. Al. Cd, Co, Cu, Cr, Fe, Mn, Hg, Mo, Ni, Pb, Ti and Zn were determined in the sludge extracts by inductively coupled plasma atomic emission spectrometry. In relation to current international legislation for the use of sludge for agricultural purposes none of metal concentrations exceeded maximum permitted levels. In most of the metal elements under considerations, results showed a clear rise along the sludge treatment in the proportion of two less-available fractions (oxidizable metal and residual metal).     

Laboratory evaluation of thermophilic-anaerobic digestion to produce Class A biosolids. 1. Stabilization performance of a continuous-flow reactor at low residence time.

There is increasing interest in the United States in producing biosolids from municipal wastewater treatment that meet the criteria for Class A designation established by the U.S. Environmental Protection Agency. Class A biosolids are intended to be free of pathogens and also must meet requirements for reduction of the vector-attraction potential associated with untreated sludge. High-temperature processes are considered to produce Class A biosolids if the combination of operating temperature and treatment time exceeds minimum criteria, but this option is not applicable to mixed, continuous-flow reactors. Such reactors, or any combination of reactors that does not meet the holding time requirement at a specific temperature, must be demonstrated to inactivate pathogens to levels consistent with the Class A criteria. This study was designed to evaluate pathogen inactivation by thermophilic anaerobic digestion in a mixed, continuous-flow reactor followed by batch or plug-flow treatment. In this first of a two-part series, we describe the performance of a continuous-flow laboratory reactor with respect to physical and chemical operating parameters; microbial inactivation in the combined continuous-flow and batch treatment system is described in the second part. Sludges from three different sources were treated at 53 degrees C, while sludge from one of the sources was also treated at 55 and 51 degrees C. Relatively short hydraulic retention times (four to six days) were used to represent a conservative operating condition with respect to pathogen inactivation. Treatment of a fermented primary sludge led to an average volatile-solids (VS) destruction efficiency of 45%, while VS destruction for the other two sources was near or below 38%, the Class A criterion for vector attraction reduction. Consistent with other studies on thermophilic anaerobic digestion of sludges at short residence times, effluent concentrations of volatile fatty acids (VFAs) were relatively high. Also consistent with other studies, the most abundant VFA in the effluent was propionate. Gas production ranged from 0.3 to 0.5 m3/kg VS fed and from 0.8 to 1.3 m3/kg VS destroyed.     

Cobalt-based alumina pillared zirconium phosphate catalysts for the selective catalytic reduction of NO by propane

A series of cobalt containing alumina pillared zirconium phosphate materials have been prepared by ion exchange or by impregnation, and fully characterised. The catalytic behaviour of these materials in the selective catalytic reduction of NO by propane, in excess of oxygen, at temperatures ranging between 350 and 550 degrees C, has been also evaluated. A maximum NO conversion close to 14% is obtained on Co-impregnated catalysts heated at 600 degrees C. The NO reduction seems to be related to the presence of Co3+, thus the calcination temperature of samples influences the resulting activity much more than the cobalt content.     

Concentrations and trends of benzene in ambient air over New York State during 1990–2003

Since 1990s, a systematic program to measure air toxics has been active in New York State with monitors located both in urban and rural areas. In this study we examined the spatial and temporal characteristics of benzene, a known human carcinogen that is emitted by many source categories. The analysis indicates that ambient concentration levels of benzene have decreased by as much as 60% over this period not only in the ozone non-attainment area of New York City that had the reformulated gas (RFG) requirements, but also over the rest of the state as well. Although the rate of decrease appears to have flattened out in recent years, the annual average concentration levels are found to be above the health risk threshold even at the remote location, Whiteface Mountain, suggesting the need for further reductions in benzene emissions.