Influence of photoperiod on carbon dioxide and methane emissions from two pilot-scale stabilization ponds.

Greenhouse gas (GHG) emissions (CO(2), CH(4)) from pilot-scale algal and duckweed-based ponds (ABP and DBP) were measured using the static chamber methodology. Daylight and nocturnal variations of GHG and wastewater characteristics (e.g. chemical oxygen demand (COD), pH) were determined via sampling campaigns during midday (12:30-15:30) and midnight (00:30-03:30) periods. The results showed that under daylight conditions in ABP median emissions were -232 mg CO(2) m(-2) d(-1) and 9.9 mg CH(4) m(-2) d(-1), and in DBP median emissions were -1,654.5 mg CO(2) m(-2) d(-1) and 71.4 mg CH(4) m(-2) d(-1), respectively. During nocturnal conditions ABP median emissions were 3,949.9 mg CO(2) m(-2) d(-1), 12.7 mg CH(4) m(-2) d(-1), and DBP median emissions were 5,116 mg CO(2) m(-2) d(-1), 195.2 mg CH(4) m(-2) d(-1), respectively. Once data measured during daylight were averaged together with nocturnal data the median emissions for ABP were 1,566.8 mg CO(2) m(-2) d(-1) and 72.1 mg CH(4) m(-2) d(-1), whilst for DBP they were 3,016.9 mg CO(2) m(-2) d(-) and 178.9 mg CH(4) m(-2) d(-1), respectively. These figures suggest that there were significant differences between CO(2) emissions measured during daylight and nocturnal periods (p < 0.05). This shows a sink-like behaviour for both ABP and DBP in the presence of solar light, which indicates the influence of photosynthesis in CO(2) emissions. On the other hand, the fluxes of CH(4) indicated that DBP and ABP behave as net sources of CH(4) during day and night, although higher emissions were observed from DBP. Overall, according to the compound average (daylight and nocturnal emissions) both ABP and DBP systems might be considered as net sources of GHG.

Percepción del riesgo por emisiones atmosféricas provenientes de la disposición final de residuos sólidos / Perception of risk arising from atmospheric emissions from an open solid-waste disposal site

Objetivo Identificar los factores sociales que determinan la percepción del riesgo en la población que se encuentra expuesta a las emisiones atmosféricas de un sitio de disposición final de residuos sólidos de la ciudad de Santiago de Cali en Colombia denominado Basuro de Navarro (BN). Materiales y Métodos Estudio cuantitativo con aplicación de una encuesta a una muestra estratificada de 199 personas con asignación proporcional según nivel socio-económico. Resultados Para el 73 % de los encuestados el principal problema es la inseguridad, y para el 50 % es la contaminación del aire. Para los encuestados la contaminación se manifiesta con dolor en la garganta y ardor en los ojos. El 64 % con mayor tiempo de residencia en el sector considera que la contaminación está concentrada en otros sitios de la ciudad y se encuentra por fuera de su sector. El 83,4 % considera que el BN produce contaminación y la asocia al aire en un 42 %. El 48 % calificó como grave y el 29 % como muy grave la contaminación producida por el BN. Discusión Se asocia la percepción del riesgo al tiempo de residencia en el sector y la edad de las personas. Se evidencia la necesidad de implementar programas de divulgación. Sería importante que la comunidad estuviera más informada acerca de los riesgos y medidas de mitigación de la contaminación ambiental asociada al BN.

Objective Identifying social factors determining the perception of risk in a population exposed to atmospheric emissions from a solid waste final disposal site in the city of Cali, Colombia (Basurero de Navarro - BN). Methods This was a quantitative study; a stratified sample of 199 people were surveyed, distributed according to socio-economic level. Results The main problem for 73% of the respondents was insecurity and 50% considered this to be air pollution. Respondents described pollution manifesting itself as pain in the throat and burning eyes; 64% who had lived longer in the sector believed that pollution was more concentrated in other parts of the city and did not affect their sector. 83.4% believed that the BN produced pollution and associated it with the air (42%). 48% rated the pollution caused by the BN as being severe and 29% as being very serious. Discussion Risk perception was associated with the length of residence in the sector and individuals' age. Many gaps in information and the need to implement outreach programmes were highlighted. It is important that the community become better informed about the risks of pollution caused by the BN and what mitigation measures can be taken.

[Perception of risk arising from atmospheric emissions from an open solid-waste disposal site]. / Percepción del riesgo por emisiones atmosféricas provenientes de la disposición final de residuos sólidos.

OBJECTIVE: Identifying social factors determining the perception of risk in a population exposed to atmospheric emissions from a solid waste final disposal site in the city of Cali, Colombia (Basurero de Navarro--BN). METHODS: This was a quantitative study; a stratified sample of 199 people were surveyed, distributed according to socio-economic level. RESULTS: The main problem for 73% of the respondents was insecurity and 50% considered this to be air pollution. Respondents described pollution manifesting itself as pain in the throat and burning eyes; 64% who had lived longer in the sector believed that pollution was more concentrated in other parts of the city and did not affect their sector. 83.4% believed that the BN produced pollution and associated it with the air (42%). 48% rated the pollution caused by the BN as being severe and 29% as being very serious. DISCUSSION: Risk perception was associated with the length of residence in the sector and individuals' age. Many gaps in information and the need to implement outreach programmes were highlighted. It is important that the community become better informed about the risks of pollution caused by the BN and what mitigation measures can be taken.