Evens Emmanuel

Assessing the Mobility of Lead, Copper and Cadmium in a Calcareous Soil of Port-au-Prince, Haiti

The presence of heavy metals in the environment constitutes a potential source of both soil and groundwater pollution. This study has focused on the reactivity of lead (Pb), copper (Cu) and Cadmium (Cd) during their transfer in a calcareous soil of Port-au-Prince (Haiti). Kinetic, monometal and competitive batch tests were carried out at pH 6.0. Two simplified models including pseudo-first-order and pseudo-second-order were used to fit the experimental data from kinetics adsorption batch tests. A good fit of these data was found with pseudo-second-order kinetic model which indicates the applicability of this model to describe the adsorption rates of these metals on the soil. Monometal batch tests indicated that both Langmuir and Freundlich models allowed a good fit for experimental data. On the basis of the maximum adsorption capacity (qmax), the order affinity of Pb, Cu and Cd for the studied soil was Pb2+ > Cu2+ > Cd2+. Competitive sorption has proved that the competition between two or several cations on soils for the same active sites can decrease their qmax. These results show that, at high metal concentrations, Cd may pose more threat in soils and groundwater of Port-au-Prince than Pb and Cu.

Influence of ionic strength and soil characteristics on the behavior of Cryptosporidium oocysts in saturated porous media

The physico-chemical behavior of Cryptosporidium oocysts was investigated during their transfer through an alluvial formation from Les Cayes (Haiti) via batch tests. Five approximately 3 kg soil samples were collected and combined prior to batch tests from the alluvial formations. The experiments were carried out at soil pH by equilibrating different ranges of pure oocysts concentrations and soil samples with 3mM CaCl2 and 1mM NaBr as electrolyte. We used the Debye-Hückel equation describing ion activity in a solution for a given ionic strength. The equilibrium adsorption mechanism is used to enumerate the oocysts in the soil. The results suggest that the oocysts behavior in porous media depends on soil characteristics such as soil pH, the nature of the mineral and organic constituents of the soil and the ionic strength and activities in solution. These results show that a total transfer in batch containing NaBr solutions against a partial one in batch containing CaCl2 solutions depends on the oocysts media concentration. To confirm the oocysts number retained in soil, confocal microscopy was successfully used and the images demonstrate that the majority of oocysts were retained at the range of concentrations tested. The findings from this study demonstrated that the retention of C. Parvum in soils may be influenced by chemical conditions and soils characteristics, which are important for groundwater risk assessment.

Cryptosporidium Contamination of Surface and Water Supplies in Haiti

ABSTRACT Cryptosporidiosis is one of the most frequent causes of diarrhea in Haiti. Transmission in children less than five years-old, HIV-infected individuals, and people living in low socio-economic conditions is frequently due to consumption of water or food contaminated by Cryptosporidium oocysts. This study examined the circulation of Cryptosporidium oocysts in surface waters and in public water supplies in the district of Port-au-Prince. Data were gathered from December 2000 to June 2002 in 37 sites. In the district of Port-au-Prince, 24/37 samples of water collected (65%) were contaminated by Cryptosporidium oocysts and 10/11 (91%) of those collected in reservoirs used by people living in peripheral areas. The rate of contamination was 7/13 (54%) in water from public standpipes provided by the public company of water distribution. All surface water (4/4) collected was highly contaminated.

Cryptosporidiosis in Haiti: surprisingly low level of species diversity revealed by molecular characterization of Cryptosporidium oocysts from surface water and groundwater

The protozoan parasite Cryptosporidium sp. has emerged as one of the most important water contaminants, causing waterborne outbreaks of diarrhoeal diseases worldwide. In Haiti, cryptosporidiosis is a frequent cause of diarrhoea in children under the age of five years, HIV-infected individuals, and people living in low socioeconomic conditions, mainly due to the consumption of water or food polluted by Cryptosporidium oocysts. The aim of this study was to detect and identify Cryptosporidium oocysts present in 12 water samples collected in Port-au-Prince and 4 water samples collected in Cap Haïtien. Initial detection consisted of immunomagnetic separation – immunofluorescence assay (IMS-IFA), which was confirmed by nested PCR, targeting the most polymorphic region of the 18S rRNA gene in 15/16 samples. Genotyping was performed by PCR-restriction fragment length polymorphism (RFLP) analysis and DNA sequencing. Under our working conditions, neither nested PCR-RFLP nor direct DNA sequencing revealed the expected species diversity, as only Cryptosporidium parvum was identified in the water samples studied. This study highlights the difficulty of detecting mixed populations of Cryptosporidium species in environmental samples.

Sewer system flow components identification using signal processing.

The development of a continuous model to simulate the behaviour of sewer systems requires detailed information on each component of the flows contributing to the global discharge. In this paper authors investigate a novel method based on signal processing and long time series data implemented with a 2 min time step (flow rate, conductivity, pH and turbidity) in order to identify the dry weather components in a separated stormwater sewer system draining an industrial catchment. The wavelet analysis is applied to the recorded data to identify main components in dry weather flow after the removing of the signal noise. This paper highlights also a method to detect inflow into sewer system and shows how hydrological modelling can be used to characterise the relevant components. These techniques could be used as a basis for several applications.

Poor Neighbourhood and Natural Disaster

In Port-au-Prince, the urban insecurity resulting from the multiplication of disadvantaged neighbourhoods is juxtaposed with a lack of urban planning, which gave rise to uncontrolled urban sprawling and social and economic segregation of urban population. The process of unplanned urbanization of Port-au-Prince has been argued through historical account on its shantytowns and typology of their habitats. Furthermore, the precarity and disaster risk circumstances of these settlements are presented through the analysis of the environmental issues in the “Cite de l’Eternel”, one of the biggest slums in Port-au-Prince. Its unbridled urbanisation process jeopardised the capital with two major challenges: insufficient infrastructure and its areas prone to floods or susceptible to landslides. The earthquake of 2010 and the risk of another major one further engrave the situation while the urgency of relocating vast number of homeless to temporary homes and shelters show tendency to remain permanent and produce new slums.