Intensified fish farming. Performance of electrochemical remediation of marine RAS waters.

Aquaculture has been the fastest growing agricultural sector in the past few decades and currently supplies about half of the fish market. A range of environmental and management concerns including limited land and water availability have led to intensifying fish production by recirculating aquaculture systems (RAS). Fish's diet contains 30-60 % protein and about 4-10 % nitrogen (N). As fish assimilate only 20-30 % of the feed to produce body mass, the unassimilated N is released in the form of toxic ammonium that deteriorates water quality and compels its degradation. Widely extended biological nitrification is not efficient in the removal of nitrites nor other chemicals and pharmaceuticals used during fish culture. Electrochemical oxidation, a less developed alternative, reports several advantages such as, i) simultaneous degradation of ammonia­nitrogen (TAN) and water disinfection in the same step with considerable simplification of the whole process, ii) easy adaptability to different production scales and periods of fish growth, and iii) no generation of harmful by-products and no use of chemicals, among others. Besides, in the case of marine aquaculture, the technology benefits from the high conductivity of seawater; thus, electrochemical oxidation is positioned in a very good place to satisfy the water treatment needs of the increasing production rate of marine aquaculture fish. Here, we report the analysis of the performance of a RAS demonstration plant aimed at farming gilthead sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) and provided with electrochemical remediation of culture water. The performance of the plant, with 20 m3 of seawater operating at a recirculation rate of 0.9-1.4 h-1, has been analysed in terms of TAN removal, water disinfection, make-up water intake and energy consumption and compared to data of conventional RAS provided with biofilters. The benefits and advantages of the innovative electrochemical remediation of RAS water are highlighted.

PAHs in the urban air of Sarajevo: levels, sources, day/night variation, and human inhalation risk.

Polycyclic aromatic hydrocarbons (PAHs) are organic pollutants derived from pyrolysis and pyrosynthesis processes. Industrial activity, motor vehicle emission, and domestic combustion are the main sources of PAHs in the urban atmosphere. In this work, samples collected during the day and night in the urban area of Sarajevo are analyzed separately for gaseous and particle-bound PAHs; the possible origin of PAHs at the receptor site was suggested using different methods applied to the solid phase and to the total PAHs (gaseous + particulate phase). Finally, the risk level in Sarajevo associated to the carcinogenic character of the studied PAHs has been assessed. The result of this study suggests that (a) the total PAH concentrations were higher than those reported in other European cities; (b) the PAH daytime concentrations are higher than nocturnal concentrations: the sum of the PAH day/night ratios is 1.52 (gas) and 1.45 (particle phase); (c) stationary combustion and traffic were suggested to be the main sources of PAHs; (d) the average particle-bound benzo(a)pyrene (BaP) concentration (5.4 ng/m(3)) is higher than EU target annual value (1 ng/m(3)); and (e) PAH cancer risk exceeds the carcinogenic benchmark level recommended by the EPA mainly due to BaP during both the day and night periods.

Evaluation of the urban/rural particle-bound PAH and PCB levels in the northern Spain (Cantabria region).

The aim of the present study was to evaluate the polycyclic aromatic hydrocarbon (PAH) and polychlorinated biphenyl (PCB) levels in PM(10) and PM(2.5), at one rural and three urban sites in the Cantabria region (northern Spain). From all of these pollutants, benzo(a)pyrene is regulated by the EU air quality directives; its target value (1 ng/m(3)) was not exceeded. The concentration values of the studied organic pollutants at the studied sites are in the range of those obtained at other European sites. A comparison between the rural-urban stations was developed: (a) PAH concentration values were lower in the rural site (except for fluorene). Therefore, the contribution of local sources to the urban levels of PAHs seems relevant. Results from the coefficient of divergence show that the urban PAH levels are influenced by different local emission sources. (b) PCB rural concentration values were higher than those found at urban sites. Because no local sources of PCBs were identified in the rural site, the contribution of more distant emission sources (about 40 km) to the PCB levels is considered to be the most important; the long-range transport of PCBs does not seem to be significant. Additionally, local PAH tracers were identified by a triangular diagram: higher molecular weight PAHs in Reinosa, naphthalene in Santander and anthracene/pyrene in Castro Urdiales. A preliminary PAH source apportionment study in the urban sites was conducted by means of diagnostic ratios. The ratios are similar to those reported in areas affected by traffic emissions; they also suggest an industrial emission source at Reinosa.

Evaluation of the contribution of local sources to trace metals levels in urban PM2.5 and PM10 in the Cantabria region (Northern Spain).

The aim of this study was to evaluate the contribution of local emission sources to the selected trace metals levels (As, Ni, Cd, Pb, Ti, V, Mn, Cu, Mo and Hg) in urban particulate matter, PM10 and PM2.5, in the Cantabria region (Northern Spain) during the year 2008. PM10 and PM2.5 samples were collected and characterized in an urban sampling site at Santander (Cantabria); additional PM10 samples were collected at a rural site at Los Tojos (50 Km SW) to evaluate both the urban and rural environment. The particulate matter and the metals regulated by the EC air quality directives (Pb, As, Ni and Cd) did not exceed the EC limit or target values in the Cantabria region. The metal concentrations were much lower at the rural site except for Ni. Different techniques were used to analyse the possible sources of the studied metals: enrichment factor, urban impact, wind and pollutant roses and principal component analysis (PCA). A combination of these techniques allowed us to demonstrate that the local emission sources of metals in the particulate matter at Santander city were the most important. Ti, Ni, As and V were identified as the main urban background tracers while Mn and Pb were the main local industrial tracers. The urban background was found to be the major contributor to PM10. The relationship between the emission tracers and the major air pollutants (NO(2), NO, CO, SO(2),O(3) and PM(10)) was also studied by PCA; a significant relationship between tracers and the major air pollutants was not found, showing a decoupled relationship between major pollutants and metal species in particulate matter.