Metropolitan Area Of Costa Rica Research Articles

Prevalence and Severity of Plaque-Induced Gingivitis in Three Latin American Cities: Mexico City-Mexico, Great Metropolitan Area-Costa Rica and Bogota-Colombia

Plaque-induced gingivitis is the most common form of periodontal disease and can affect 100% of the population. Gingivitis prevalence in Latin American population is not well documented, therefore the aim of this study was to determine the prevalence and severity of plaque-induced gingivitis in adult populations of three Latin American cities. Methods: This cross sectional multicenter study included 1650 participants, 550 from the Great Metropolitan Area of Costa Rica (GAM), 550 from Mexico City, Mexico (CDMX) and 550 from Bogota City, Colombia (BC). Subjects completed a questionnaire about their medical history and oral hygiene. Clinical assessment included recording of missing teeth, visible plaque index, calculus recording and gingival index (GI, Loe-Silness index). Results: Average GI was 1.36. No statistical difference was found between GAM (1.45) and BC (1.48); however, GI in CDMX was significantly lower (1.16). Average gingival bleeding on probing was 43%. Total plaque index was 0.76 showing the highest accumulation at interproximal sites (p=0.0001). A positive correlation was found between plaque and gingivitis (r=0.59). Dental calculus was present in at least one of the 18 evaluated sites per subject with no statistical difference between cities. There was no statistical difference in GI between smokers, former smokers and non- smokers. Conclusion: Gingivitis prevalence was 99.6%. Moderate Gingivitis was the predominant form, with no statistically significant difference between cities or gender. Dental plaque accumulation was the most important risk factor associated with the establishment of the disease.

Prevalence and Severity of Plaque-Induced Gingivitis in Three Latin American Cities: Mexico City-Mexico, Great Metropolitan Area-Costa Rica and Bogota-Colombia

Plaque-induced gingivitis is the most common form of periodontal disease and can affect 100% of the population. Gingivitis prevalence in Latin American population is not well documented, therefore the aim of this study was to determine the prevalence and severity of plaque-induced gingivitis in adult populations of three Latin American cities. Methods: This cross sectional multicenter study included 1650 participants, 550 from the Great Metropolitan Area of Costa Rica (GAM), 550 from Mexico City, Mexico (CDMX) and 550 from Bogota City, Colombia (BC). Subjects completed a questionnaire about their medical history and oral hygiene. Clinical assessment included recording of missing teeth, visible plaque index, calculus recording and gingival index (GI, Loe-Silness index). Results: Average GI was 1.36. No statistical difference was found between GAM (1.45) and BC (1.48); however, GI in CDMX was significantly lower (1.16). Average gingival bleeding on probing was 43%. Total plaque index was 0.76 showing the highest accumulation at interproximal sites (p=0.0001). A positive correlation was found between plaque and gingivitis (r=0.59). Dental calculus was present in at least one of the 18 evaluated sites per subject with no statistical difference between cities. There was no statistical difference in GI between smokers, former smokers and non- smokers. Conclusion: Gingivitis prevalence was 99.6%. Moderate Gingivitis was the predominant form, with no statistically significant difference between cities or gender. Dental plaque accumulation was the most important risk factor associated with the establishment of the disease.

“Mall”-deando la ciudad: 24 años de territorialización de los malls en Costa Rica

La territorialización de los malls en Costa Rica inicia en el año 1993 con la inauguración de Multiplaza Escazú, en la Gran Área Metropolitana de Costa Rica. De este año al año 2017 se contabiliza un total de 14 malls. En este artículo se hará un recorrido sobre las principales características que tienen los malls; se caracterizará la llegada del primer mall al país y se desarrollará un análisis de la evolución espacio-temporal que han tenido estas infraestructuras en la GAM. Por último, se hace un repaso de algunos de los reclamos y respuestas ciudadanas que se han dado ante la construcción de un mall.

Polycyclic aromatic hydrocarbons in filterable PM2.5 emissions generated from regulated stationary sources in the metropolitan area of Costa Rica

This study analyzed the profiles of polycyclic aromatic hydrocarbons (PAHs) in filterable PM2.5 particles collected from a total of 71 boilers and 22 indirect type furnaces that burn liquid and biomass fuels in the Metropolitan Area of Costa Rica, from February 2014 to November 2015. Modified method NIOSH 5506 was used to analyze PAHs content present in the filter samples. The average concentration of PM2.5 showed values between 18 and 735 mg m−3, based on the source and fuel type used, while the total PAHs in the PM2.5 fraction ranged 1.02–592 μgm−3. For biomass boilers, the most abundant species were Benzo[g,h,i]perylene (BghiP) (35.7–46.5%), Indeno[1,2,3-cd]pyrene (IND) (20.6–27.1%), Benzo[a]pyrene (BaP) (5.2–14.7%) and Dibenzo[a,h]anthracene (DBA) (3.2–13.9%), while for liquid fuels IND (12.8–20.5%), BghiP (7.9–21.2%), Fluoranthene (Flu) (14.5–21.3%) and Pyrene (Pyr) (9.8–14.5%) prevailed. The particles from biomass furnace emissions present higher concentrations of PAHs classified by the U.S. EPA as probable human carcinogens causing a greater health risk than other fuels. Among the diagnostic concentration ratios examined, only BaP/(BaP+Chr), BaA/Chr, BaA/BaP and Pyr/BaP coefficients demonstrated codependency on the type of fuel used.

Chemical characterization of filterable PM2.5 emissions generated from regulated stationary sources in the Metropolitan Area of Costa Rica

Filterable PM2.5 concentrations and their chemical characterizations were analyzed for 67 boilers and 25 indirect furnaces located in the Metropolitan Area of Costa Rica from February 2014 to November 2015. The PM2.5 samples were characterized by their composition, focusing on trace elements, inorganic ions and organic and elemental carbon. The results of PM2.5 concentrations ranged from 72 to 735 mgm-3, with the highest concentrations found for sources using biomass fuel, particularly Type B boilers, and the lowest values for diesel boilers. Further speciation of fine particulate matter (PM) showed significant levels of vanadium and nickel for boilers that use heavy fuel oil (bunker); 4886 and 1942 μgm-3, respectively. Copper and manganese were the most relevant metals for biomass burning sources, due to plant absorption from the soil. As for ion concentration, sulfate presented the highest concentrations for biomass boilers and furnaces, whereas chloride only presented the highest concentrations for furnaces. To complete the balance, organic and elemental carbon (OC and EC) analyses were made, in which biomass burning sources presented values five times higher than oil fuels. A Spearman's correlation analysis was made for the data set, revealing significant relationships between heavy metals, sulfate, and fine PM with respect to heavy fuel oil. For the biomass sources, the correlations pointed to K, Na, Mn and, in some cases, oxygen.

Greenhouses Gases, Carbonyls, and Volatile Organic Compounds Surface Flux Emissions at Three Final Waste Disposal Sites Located in the Metropolitan Area of Costa Rica

The surface flux emissions for volatile organic compounds (VOC’s) (alcohols and aromatic species), priority carbonyls and greenhouse gases, were measured in three different final disposal sites for urban solid waste located in the metropolitan area of Costa Rica, between July and October 2014. The emissions fluxes were determined using the static sampling chamber technique coupled to two different adsorption tubes: active charcoal (Supelco, ORBO 32) to capture BTEX and alcohols; and 2,4-DNPH coated silica gel (SKC, 226-119) for carbonyls. As for the VOCs, the BTEX, Alcohols, and Carbonyls total fluxes were in the range of 3 to 258, 1 to 318 and 0.4 to 8.5 mg/(m2d&#237a), respectively. The magnitudes per site were in the following order La Carpio > El Huaso > Rio Azul. Ethanol and BTEX presented a high correlation in all the cases because possibly they are sharing the same sources or formation mechanisms. The emission fluxes spatial distributions among the sites were very variable and dependent on the location of the active cells and their age. Only La Carpio showed a more homogeneous distribution due to its middle age.

Prevalencia de <i>Fasciola Hepatica</i> y pérdidas económicas asociadas al decomiso de hígados en tres mataderos de clase a de Costa Rica

Para estimar la prevalencia anual y mensual de Fasciola hepatica y las pérdidas económicas anuales asociadas al decomiso de hígados por presencia del parásito, se analizaron los registros del Ministerio de Agricultura y Ganadería de Costa Rica, Dirección de Inocuidad de Productos de Origen Animal (DIPOA), para el 2014, provenientes de 3 mataderos clase A localizados en el área metropolitana de Costa Rica; en estos mataderos se sacrificaron 249 108 reses, de las cuales 4547 hígados fueron decomisados por presencia de F. hepatica en el órgano. Las mayores prevalencias, entre 2,33 y 2,55%, se presentaron en enero, febrero y marzo, y las menores, entre 1,32 y 1,56%, durante agosto, setiembre y octubre. La prevalencia anual según estos registros fue 1,83% (IC 95%: 1,77-1,88). Las pérdidas económicas asociadas al decomiso de hígados fueron de 36.379.000 CRC, equivalentes a 67.438 USD. Se resalta el perjuicio económico de este parásito a nivel nacional y la utilidad del decomiso y registro de vísceras afectadas en los establecimientos de sacrificio de bovinos, como herramienta diagnóstica para la vigilancia epidemiológica, disponible para conocer sobre el estado de esta parasitosis. Como alternativas de control y prevención de la enfermedad, se plantea considerar las condiciones específicas de las regiones afectadas y así controlar esta parasitosis con un manejo integral, que involucre la fuente de alimento, desparasitación regular del ganado, con registro y monitoreo farmacológico de las drogas utilizadas, y saneamiento ambiental en fincas afectadas.

TASAS DE GENERACIÓN Y CARACTERIZACIÓN DE RESIDUOS SÓLIDOS ORDINARIOS EN CUATRO MUNICIPIOS DEL ÁREA METROPOLITANA COSTA RICA

Se determinó la tasa de generación y caracterización de residuos sólidos ordinarios, en el sector residencial y comercial de 04 municipios ubicados geográficamente dentro del Gran Área Metropolitana de Costa Rica. Para ello, en el período 2014-2015, se realizaron muestreos en un número representativo de viviendas y comercios durante 07 días consecutivos. La tasa de generación promedio ponderada de residuos para el área de estudio resultó ser de 0,59 kg/hab-día. Los residuos sólidos generados presentan como componentes mayoritarios: orgánicos 55,9%, seguidos de materiales con alto potencial para ser reciclados o utilizados como combustibles (plásticos 10,2%, papel y cartón 10,4%). El contenido de humedad promedio en los residuos fue de 58,7% en masa (mínimo 54% en Alajuela y máximo 63% en Barva), de la cual hasta un 67% puede ser atribuible a residuos orgánicos biodegradables. El peso volumétrico promedio de los residuos resultó de 155 kg/m3 (mínimo de 141 en Belén y máximo de 163 en San José). Se evidenció que existen diferencias significativas en la composición de residuos sólidos para los sectores comerciales y residenciales, principalmente en la fracción orgánica, papel, cartón y plástico.

Polycyclic aromatic hydrocarbons in PM2.5 and PM10 atmospheric particles in the Metropolitan Area of Costa Rica: Sources, temporal and spatial variations

Polycyclic aromatic hydrocarbons (PAHs) concentrations in PM10 and PM2.5 particles were measured at 14 monitoring sites (12 for PM10 and 2 for PM2.5), located in the Metropolitan Area of Costa Rica, from January to November 2013. High-volume air samplers with pretreated quartz filters were used to collect the particles. The analytical determination was carried out using high-performance liquid chromatography (HPLC). The most abundant PAHs were benzo[a]anthracene, indeno(1,2,3-cd)pyrene, dibenz[a,h]anthracene and acenaphthylene. Ratios obtained by correlating the concentration of some PAHs, both PM10 and PM2.5, suggest that gasoline and diesel vehicles are the main sources in the area being studied. This is consistent with the results obtained when applying the positive matrix factorization (PMF) analysis, since vehicles accounted for 62–74% of total emissions in the area; burning wood fuel was the second source of emissions, contributing between 7 and 15%; and road dust was third, with almost 8%.

Una mirada al involucramiento paterno: participación de los hombres jefes de hogar de la Gran Área Metropolitana de Costa Rica en actividades de cuidado directo

Producto de la división sexual del trabajo, a hombres y mujeres se les han definido los roles, tareas y espacios que deben asumir en la sociedad: a los hombres el trabajo productivo y a las mujeres el reproductivo. Si bien ellas se han incorporado al trabajo remunerado, los hombres no participan de la misma manera en las actividades no remuneradas. Esta desigualdad en la distribución de las tareas domésticas y de cuidado es lo que motiva en este artículo a analizar la participación de los hombres en el trabajo no remunerado, particularmente en el cuidado directo de hijos e hijas menores de 12 años. Se busca dar respuesta a preguntas como ¿participan los hombres padres y jefes de hogar de la Gran Área Metropolitana de Costa Rica, con hijos e hijas menores de 12 años, en las actividades de cuidado directo?, ¿en cuáles actividades y cuánto tiempo le dedican a las mismas?

Exposure of dogs to spotted fever group rickettsiae in urban sites associated with human rickettsioses in Costa Rica

The zoonotic transmission cycles of Rickettsia rickettsii and other spotted fever group (SFG) rickettsiae in Latin America have usually been associated with rural or sylvatic environments, although domestic dogs can be implicated in more populated settings. In this study, exposure of dogs to SFG rickettsiae in the Greater Metropolitan Area of Costa Rica was investigated. Dogs from sites associated with human cases and from dog shelters were evaluated by indirect immunofluorescence assay (IFA) using antigen of SFG rickettsiae. Rickettsia spp. were detected in ectoparasites by polymerase chain reaction (PCR). A total 18.5% (31/168) of dogs associated with human cases and 6.8% (11/161) of dogs in shelters had IgG end titers≥64 to Rickettsia spp. The odds of being seropositive were greater in dogs from areas associated with human cases when compared to shelters (OR: 3.2; 95% C.I: 1.5–5.6). Rhipicephalus sanguineus sensu lato (s. l.) was present in all sites associated with human cases. Rickettsia felis URRWXCal2 and R. felis-like RF2125 were detected in Ctenocephalides felis, and Rickettsia sp. IbR/CRC in Ixodes boliviensis. Results demonstrate that dogs from the main urban center of Costa Rica have been exposed to SFG rickettsiae, especially in areas with known human infection. Both human and animal health sectors must be aware of possible rickettsial diseases in urban areas, where dogs may also serve as sentinels for human infection.

Tree trunk lichen cover and its relation with cardinal orientation in parks of the Greater Metropolitan Area of Costa Rica.

The geographical position of Costa Rica at 11 ° north latitude produces varying temperatures and two seasons, wet and dry, that are clearly established. Tree trunk lichens are greatly affected by humidity and air pollution, factors that can differ according to cardinal orientation of the substrate. We studied eight trees in each of the ten municipal parks in three central provinces: Alajuela, Cartago and San José. With a template we measured lichen cover, regardless of species during the dry and rainy seasons. The highest cover was on the north side of trunks and in the rainy season.

ANÁLISIS DE LA VALIDEZ DISCRIMINANTE DEL EATING ATTITUDES TEST MEDIANTE EL MODELO DE RASCH ANALYSIS OF THE DISCRIMINANT VALIDITY OF THE EATING ATTITUDES TEST THROUGH THE RASCH MODEL

Se analiza la validez discriminante del Eating Attitudes Test (EAT-40) mediante la Teoría de Respuestaal Ítem y su modelo de un parámetro, conocido como modelo de Rasch. El EAT-40 (Garner & Garfinkel,1979) consiste en un instrumento de detección temprana del riesgo de desarrollar trastornos de la conductaalimentaria (TCA), cuyas evidencias de validez en Costa Rica se repasan en este trabajo. Para esteestudio se aplicó la versión española del instrumento (Castro, Toro, Salamero & Guimerá, 1991) a unamuestra de 556 mujeres del área metropolitana de Costa Rica, con un edad promedio de 17.66 años (DE= 6.65). Para aumentar la varianza de las puntuaciones, la muestra estuvo compuesta por estudiantesde colegio (n = 391, 70.3%), de universidad (n = 120, 21.6%), de academias de ballet (n = 26, 4.7%) ypacientes hospitalizadas por bulimia nerviosa o anorexia nerviosa (n = 19, 3.4%). Mediante el modelode Rasch, el análisis del mapeo de dificultad, y el análisis de las curvas características de los ítems yde la prueba completa, se obtuvo evidencia consistente de la capacidad de los ítems del EAT-40 paradiscriminar entre personas con y sin riesgo de TCA. En el apartado final se discuten los hallazgos y seabordan las limitaciones del tamaño de la muestra clínica.

Analysis of Benzene Exposure Levels on Commuters Traveling within the Metropolitan Area of Costa Rica

This study reports the benzene exposure levels of commuters traveling within the metropolitan area of Costa Rica using personal cars, buses, and urban trains. 47 in-vehicle samples were col- lected in the 2014 wet season under three different driving conditions: rush hour traffic, normal traffic and weekends. Samples were collected in Tedlar bags and analyzed using 75 µm carboxen- polydimethylsiloxane (CAR/PDMS) and gas chromatography with flame ionization detection (GC- FID). Additionally, duplicate samples were collected on adsorption tubes filled with Tenax TA and analyzed by thermal desorption (TD) and GC-FID. Results indicate that travelling in cars and buses under rush hour conditions exposes commuters to statistically equal average benzene concentra- tion of 48.7 and 51.6 µg/m3, respectively. Average benzene levels in urban trains (33.0 µg/m3) were measured only during morning rush hours. Greater benzene levels in buses than personal cars concentrations may be attributable to the immersion of traffic-related emission within the bus ca- bins. Factors, such as the driving pattern, the number of vehicles on the route, the road infrastruc- ture, and the prevalence of gasoline-fueled vehicles in Costa Rica, may increase ambient benzene concentrations. Benzene levels inside car cabins reported in this study are in the range of those reported in other urban areas; however, the corresponding concentrations inside buses and urban trains (rush hour only) are higher than previously published exposure levels.

Composición de macronutrientes de la alimentación servida a niños y niñas menores de 6 años en centros de cuido, Hogares Comunitarios de la GAM en Costa Rica, 2010

Community Child Care Centers in Costa Rica represent a low cost, partially subsidized child care option for helping families living in poverty. Children from 0 to 7 years receive care and meals during the day. These centers should follow the nutritional guidelines established by the national authority to offer at least 70% of their energy needs. However, information regarding to the nutritional composition of meals offered is not well known. Objective: To evaluate the energy and macronutrient composition of lunch, morning and afternoon snacks offered in 33 community child care centers located in the metropolitan area of Costa Rica. Methods: A lunch and morning and afternoon snacks were evaluated for each child by direct weight of each meal. Results: 77% of the evaluated meals did not fulfil the recommended amount of energy. Protein did meet the recommendation for children younger than 2 years old but not for the older ones. Carbohydrate was over the recommended amount for all children, while fat was insufficient. Conclusion: Meals offered to children attending in the evaluated 33 Community Child Centers do not fulfil their energy needs. It is highly recommended to perform more in depth evaluations in order to modify current practices in these centers and to contribute to the improvement of all centers nationwide. Updated support materials for community mothers are needed to achieve and develop menu cycles and to offer portion size meals according to the needs of the population they serve.

Microcistina en plantas de tratamiento de agua para consumo humano en un ambiente tropical: el Área Metropolitana de Costa Rica

We measured microcystin levels in water of the Metropolitan Area of Costa Rica by competitive inhibition ELISA and we quantified total coliforms, fecal coliforms, Escherichia coli (by a Most Probable Number method) and aerobic count. We wanted to identify any cyanotoxin correlation with these parameters, as a public health risk. We sampled in the rainy season of 2003 (April-October) and in the dry season of 2004 (February-March) (30 samples/season). We sampled pre-treated, semi-treated and treated water. Microcystin levels < 0.5 ppb were found in the rainy season (and > 0.5 ppb in the dry season). Dry season levels exceeded World Health Organization limits (1.0 ppb). Cyanotoxins occurred in the Tres Rios plant. We did not find a correlation between these microbiologic parameters of water quality and microcystin levels in water.

Chemical characterization and source apportionment of PM10 and PM2.5 in the metropolitan area of Costa Rica, Central America

PM10 and PM2.5 levels, concentrations of major ionic components, trace elements, and organic and elemental carbon were evaluated from samples collected in 4 sites (industrial, commercial and residential zones) located in the metropolitan area of Costa Rica. The annual mean PM levels were higher in high traffic–commercial (HE–01) and industrial (BE–02) sites, 55 μg m–3 and 52 μg m–3 for PM10 and 37 μg m–3 and 36 μg m–3 for PM2 5, respectively. The major components of PM25 were organic matter (OM) and elemental carbon (EC) (44.5–69.9%), and secondary ions (16.1–27.2%), whereas the major components of PM10 were OM+EC (32.7–59.4%), crustal material (23.5–35.6%) and secondary ions (11.4–26.9%). For the most of the sampling sites, PM10 and PM2.5 concentrations were lower during the dry season and increased gradually in the rainy season due to wind patterns. PMF model identified 8 principle sources for PM10 and PM2.5 in the industrial site (crustal, secondary sulfate, secondary nitrate, secondary organic, traffic, sea–salt aerosols, industrial and oil combustion), 6 and 5 sources in commercial and residential sites, respectively. The source contributions showed a clear seasonal pattern for all the sites.

Source Apportionment of PM2.5 in the Metropolitan Area of Costa Rica Using Receptor Models

In this work, receptor models were used to identify the PM2.5 sources and its contribution to the air quality in residential, comercial and industrial sampling sites in the Metropolitan Area of Costa Rica. Principal component analysis with absolute principal component scores (PCA-APCS), UNIMX and positive matrix factorization (PMF) was applied to analyze the data collected during 1 year of sampling campaign (2010-2011). The PM2.5 samples were characterized through its composition looking for trace elements, inorganic ions and organic and elemental carbon. These three models identified some common sources of PM2.5: marine aerosol, crustal material, traffic, secondary aerosols (secondary sulfate and secondary nitrate resolved by PMF), a mixed source of heavy fuels combustion and biomass burning, and industrial emissions. The three models predicted that the major sources of PM2.5 in the Metropolitan Area of Costa Rica were related to anthropogenic sources (73%, 65% and 69%, respectively, for PCA-APCS, Unmix and PMF) although natural sources also contributed to PM2.5 (21%, 24% and 26%). On average, PCA and PMF methods resolved 94% and 95% of the PM2.5 mass concentrations, respectively. The results were comparable to the estimate using UNMIX.

Temporal and spatial variations in organic and elemental carbon concentrations in PM10/PM2.5 in the metropolitan area of Costa Rica, Central America

PM2.5 and PM10 samples were collected at 4 and 14 sampling sites, respectively, located in the Metropolitan area of Costa Rica (MACR), during 2010–2011. These sites were representative of commercial, industrial and residential zones of this region. Concentrations of elemental carbon (EC) and organic carbon (OC) were analyzed using the IMPROVE thermal-optical reflectance (TOR) method. OC and EC concentrations were higher in commercial and industrial sites and showed clear seasonal variations with higher concentrations observed in the rainy season (May–November) than in the dry season (December–April), due to wind patterns in the study area. Total carbonaceous aerosol accounted for 35% of PM10 and 56% of PM2.5 mass. Good correlation between OC and EC in PM10 (R=0.89–0.75) and PM2.5 (R=0.79– 0.64) indicated that they had common dominant sources of combustion such as industrial activities and traffic emissions. The annual average concentrations of estimated SOC (Secondary Organic Carbon) in the MACR PM10 samples showed values between 0.65–8.49 μg/m3, accounting for 48% and 56% of the OC in PM10 and PM2.5 respectively. Positive Matrix Factorization (PMF) identified five principal sources for OC and EC in particles: gasoline vehicles, diesel vehicles, on road traffic, wood smoke and industrial combustion. The contribution of each of the source varied between the PM10 and PM2.5 size fractions.

Relations Between Bulk Precipitation, PM10 Composition and Meteorological Conditions in the Metropolitan Area of Costa Rica

Concentrations of inorganic ions (Cl-, H+, SO42-, NO3-, NH4+, Na+, K+, Ca2+, Mg2+) and metals (V, Ni, Cu, Pb, Cr Mn, Al, Fe) in bulk precipitation and PM10 samples collected in the metropolitan area of Costa Rica were analyzed. Good correlations between acidity in bulk precipitation with the concentrations of aerosols in the air were observed. The scavenging of the pollutants from the air directly affects the pH and composition of the bulk precipitation. The major ions in bulk precipitation in the metropolitan area of Costa Rica were SO42-, NH4+, Ca2+, Na+ ion percentages with 41.4, 12.0, 10.9 and 9.1 respectively. Al, Fe and Mn were the most abundant trace metals. The alkaline cations, NH4+ and Ca2+, actedas acid neutralizers and buffered the acidity of bulk precipitation. Meteorological conditions presented during the events determine the composition of bulk precipitation samples.