Estimation of green house gas emissions from Koteshwar hydropower reservoir,India

The emissions of greenhouse gas (GHG) from soils are of significant importance for global warming. The biological and physico-chemical characteristics of soil affect the GHG emissions from soils of different land use types. Methane (CH₄), nitrous oxide (N₂O), and carbon dioxide (CO₂) production rates from six forest and agricultural soil types in the Koteshwar hydropower reservoir catchments located in the Uttarakhand, India, were estimated and their relations with physico-chemical characteristics of soils were examined. The samples of different land use types were flooded and incubated under anaerobic condition at 30 °C for 60 days. The cumulative GHG production rates in reservoir catchment are found as 1.52 ± 0.26, 0.13 ± 0.02, and 0.0004 ± 0.0001 μg g soil^?1 day^?1 for CO₂, CH₄, and N₂O, respectively, which is lower than global reservoirs located in the same eco-region. The significant positive correlation between CO₂ productions and labile organic carbon (LOC), CH₄ and C/N ratio, while N₂O and N/P ratio, while pH of soils is negatively correlated, conforms their key role in GHG emissions. Carbon available as LOC in the reservoir catchment is found as 3–14% of the total ?C” available in soils and 0–23% is retained in the soil after the completion of incubation. The key objective of this study to signify the C, N, and P ratios, LOC, and pH with GHG production rate by creating an incubation experiment (as in the case of benthic soil/sediment) in the lab for 60 days. In summary, the results suggest that carbon, as LOC were more sensitive indicators for CO₂ emissions and significant C, N, and P ratios, affects the GHG emissions. This study is useful for the hydropower industry to know the GHG production rates after the construction of reservoir so that its effect could be minimized by taking care of catchment area treatment plan.     

Soil erosion and sediment fluxes analysis: a watershed study of the Ni Reservoir,Spotsylvania County,VA, USA

Anthropogenic forces that alter the physical landscape are known to cause significant soil erosion, which has negative impact on surface water bodies, such as rivers, lakes/reservoirs, and coastal zones, and thus sediment control has become one of the central aspects of catchment management planning. The revised universal soil loss equation empirical model, erosion pins, and isotopic sediment core analyses were used to evaluate watershed erosion, stream bank erosion, and reservoir sediment accumulation rates for Ni Reservoir, in central Virginia. Land-use and land cover seems to be dominant control in watershed soil erosion, with barren land and human-disturbed areas contributing the most sediment, and forest and herbaceous areas contributing the least. Results show a 7 % increase in human development from 2001 (14 %) to 2009 (21.6 %), corresponding to an increase in soil loss of 0.82 Mg ha^-1 year^-1 in the same time period. ²¹⁰Pb-based sediment accumulation rates at three locations in Ni Reservoir were 1.020, 0.364, and 0.543 g cm^-2 year^-1 respectively, indicating that sediment accumulation and distribution in the reservoir is influenced by reservoir configuration and significant contributions from bedload. All three locations indicate an increase in modern sediment accumulation rates. Erosion pin results show variability in stream bank erosion with values ranging from 4.7 to 11.3 cm year^-1. These results indicate that urban growth and the decline in vegetative cover has increased sediment fluxes from the watershed and poses a significant threat to the long-term sustainability of the Ni Reservoir as urbanization continues to increase.     

Assessment of pathogenic bacteria in water and sediment from a water reservoir under tropical conditions (Lake Ma Vallée), Kinshasa Democratic Republic of Congo

This study was conducted to assess potential human health risks presented by pathogenic bacteria in a protected multi-use lake-reservoir (Lake Ma Vallée) located in west of Kinshasa, Democratic Republic of Congo (DRC). Water and surface sediments from several points of the Lake were collected during summer. Microbial analysis was performed for Escherichia coli, Enterococcus (ENT), Pseudomonas species and heterotrophic plate counts. PCR amplification was performed for the confirmation of E. coli, ENT, Pseudomonas spp. and Pseudomonas aeruginosa isolated from samples. The results reveal low concentration of bacteria in water column of the lake, the bacterial quantification results observed in this study for the water column were below the recommended limits, according to WHO and the European Directive 2006/7/CE, for bathing water. However, high concentration of bacteria was observed in the sediment samples; the values of 2.65?×?10³, 6.35?×?10³, 3.27?×?10³ and 3.60?×?10⁸ CFU g^?1 of dry sediment for E. coli, ENT, Pseudomonas spp. and heterotrophic plate counts, respectively. The results of this study indicate that sediments of the Lake Ma Vallée can constitute a reservoir of pathogenic microorganisms which can persist in the lake. Possible resuspension of faecal indicator bacteria and pathogens would affect water quality and may increase health risks to the population during recreational activities. Our results indicate that the microbial sediment analysis provides complementary and important information for assessing sanitary quality of surface water under tropical conditions.     

Assessment of heavy metals in aquatic sediments

The concentration of heavy metals in the bottom sediment and interstitial water collected from two reservoirs in Singapore was found to be enriched. A distribution coefficient,K _d , was used to assess the chemical stability of heavy metals in the sediments. Numerical models were used to assess (1) the redistribution of heavy metals in a changing environment, and (2) long-term self clean-up capabilities of a reservoir.     

The Contamination Levels of Organochlorine Pesticides in Water and Sediment Samples in Uluabat Lake, Turkey

The Uluabat Lake is a reservoir of 125 km² surface area, in the boundaries of Bursa province, Turkey. The results showed that Uluabat Lake was still contaminated by organochlorine pesticides and their residues despite the existence of bans over a long time. Considerable amounts of organochlorine pesticides (HCB, p.p^′-DDT, p.p^′- DDE, α -, β- and γ-BHC, Aldrin, Heptachlor epoxide, Endrin, Endosulfan I and II) were detected in water and sediment samples during one-year study in this lake. Samples of water and sediment were collected in different regions, (6 sampling point) of the lake between February 2002 and November 2002.The mean levels of organochlorine pesticides in water and sediments were determined. According to results, it was found that various environs in Uluabat Lake were contaminated by 11 different organochlorine pesticides. Residue analyses showed that higher organochlorine pesticides and their residues were generally more accumulated in the sediment samples.     

Water quality of Mediterranean coastal plains: conservation implications from the Akyatan Lagoon,Turkey

The water quality of the Akyatan Lagoon was characterized using hydrochemical methodology. The lagoon is located on the Mediterranean coast and is the largest wetland ecosystem in Turkey. In addition, the lagoon is classified as a hyper-salinity wetland. Water samples were collected monthly between December 2007 and November 2008. Eleven stations within the lagoon were determined, and triplicate grab samples were obtained from each station to characterize water quality as follows: T °C, pH, total alkalinity (TAlk), dissolved oxygen (DO), total dissolved solids (TDS), salinity, electrical conductivity (EC), and main anions, including chloride (Cl^?), nitrates (NO₃ ^?), and sulfate (SO₄ ^2?). Results from selected stations indicated varying TDS, EC, salinity, and Cl^? concentrations, from 20,892 to 175,824 mg/L, from 35.7 to 99.6 mS/cm, from 22.3 to 71.0 ppt, and from 14,819 to 44,198 mg Cl^?/L, respectively. Data indicated that the spatial distribution of water quality parameters was significantly affected by freshwater input via the constructed drainage channels which collect water from a catchment area and discharge water into the lagoon as a point source, thus preventing drainage water to reach the lagoon as a nonpoint source.     

Distribution and bioaccumulation of organochlorine pesticides (OCPs) in food web of Nansi Lake,China

The concentration of 12 organochlorine pesticides (OCPs) were measured in water, sediment, aquatic plant, and animal (shrimp and fish) of Nansi Lake by gas chromatography equipped with an electron capture detector. The total OCPs concentrations were 65.31–100.31 ng L^?1 in water, 2.9–6.91 ng g^?1 dry weight (dw) in sediments, 1.29–6.42 ng g^?1 dw in aquatic plants and 7.57–17.22 ng g^?1 dw in animals. The OCPs composition profiles showed that heptachlor compounds was also the predominant OCPs contaminants in addition to hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) in Nansi Lake. According to the source of HCHs and DDTs in sediment samples, there was no new input and the HCHs pollution mainly came from the use of Lindane in Nansi Lake. Bioaccumulation of OCPs in aquatic biota indicated that DDTs and heptachlor compounds had a strong accumulation, followed by HCHs and drins. The accumulation abilities of fish for OCPs were higher than those of plants and shrimps. The OCPs biota-sediment accumulation factor values of Channa argus was the highest in fish samples, followed by Carassius auratus, and Cyprinus caspio. Risk assessment of sediment showed that heptachlor epoxide had a higher occurrence possibility of adverse ecological effects to benthic species. Based on the calculation of acceptable daily intake and hazard ratio, HCHs in fish and shrimps from Nansi Lake had a lifetime cancer risk of greater than one per million. The risk assessment of water, sediment, and fish indicated the water environment of Nansi Lake is at a safe level at present.     

Impacts of climate-induced changes on the distribution of pesticides residues in water and sediment of Lake Naivasha, Kenya

This study reports evidence of increased chlorpyrifos contamination in sediment and water in Lake Naivasha following its intensive application in the horticultural farms in the catchment area. Analytical results show that levels of chlorpyrifos residues were influenced by climate-induced rainfall pattern with higher levels reported during period of heavy precipitation with significant decrease during low rainfall. On average, the levels ranged between 14.8 and 32.8 ng g^?1 in sediment during rainy season compared to a range of 8.5–16.6 ng g^?1 in the dry season. Additionally, the mean concentration of chlorpyrifos in water ranged between 8.61 and 22.4 μg L^?1 during rainy season and below detection limit (bdl) ?13.6 μg L^?1 in dry season as quantified by enzyme-linked immunosorbent assay. Meanwhile, independent t test analysis indicated that there was significant difference in concentration at p?≤?0.05 between the seasons with respect to sediment and water samples. This demonstrated that climate-induced variations had considerable influence on contamination. While diazinon and carbofuran were equally applied intensively, their levels were below the detection limit in the all the samples analyzed. ELISA results were validated by the capillary-HPLC photodiode-array detector instrument analysis, and statistical comparison showed no significant difference between them. It was evident that chlorpyrifos residues determination in water and sediment by ELISA can be a useful strategy in environmental management and monitoring program, and a complimentary analytical tool to high performance liquid chromatography. Levels of chlorpyrifos detected in sediment and water were found to exceed recommended criteria for protection of aquatic life and preservation of water quality and may be hazardous if not regularly monitored.     

Evaluation of the impacts of road runoff in a Mediterranean reservoir in Portugal

Road runoff is a linear diffuse source of pollution, with very specific characteristics. This study intends to improve the understanding of road runoff impacts in water bodies in Portugal. The chosen case study is S. Domingos reservoir catchment. The study analyzed land uses, the presence of pollution sources, and gathered temporal water quality data and performed site measurements and sample collection. The water quality data for the reservoir was provided by the national water quality monitoring system from the Portuguese Water Institute. The parameters selected were TSS, COD, NO₃ ^?, Cl^?, and Cu. The results obtained revealed that the presence of IP6 highway at S. Domingos catchment affects the water quality; however, the impacts are not significant due to the high dilution effect of the reservoir volume. Agriculture, the main land use of the catchment, is responsible for introducing pollutants such as TSS, Cl^?, COD, N, and P in the local water streams and at the reservoir. TSS, COD, and Cu are pollutants generated by the road. The success of the study was very much dependent on the availability of 12 years of historic water quality data for S. Domingos reservoir, and the use of the moving average method. Taking into consideration the high variability of hydrological variables in Mediterranean climates, the concentration of pollutants in the water bodies must always be assessed in a significant time period.     

Groundwater environmental capacity and its evaluation index

At present, anthropogenic contribution of heavy metals far exceeds natural input in some aquatic sediment, but the proportions are difficult to differentiate due to the changes in sediment characters. In this paper, the metal (Al, Fe, K, Mg, Ca, Cr, Cu, Ni, and Zn) concentrations, grain size, and total organic carbon (TOC) content in the surface and core sediments of Nansihu Lake Catchment (the open lake and six inflow rivers) were determined. The chemical speciations of the metals (Al, Fe, Cr, Cu, Ni, and Zn) in the surface sediments were also analyzed. Approaches of factor analysis, normalized enrichment factor (EF) and the new non-residual fractions enrichment factor (K_NRF) were used to differentiate the sources of the metals in the sediments, from detrital clastic debris or anthropogenic input, and to quantify the anthropogenic contamination. The results indicate that natural processes were more dominant in concentrating the metals in the surface and core sediments of the open lake. High concentration of Ca and deficiency of other metals in the upper layers of the sediment core were attributed to the input of carbonate minerals in the catchment with increasing human activities since 1980s. High TOC content magnified the deficiency of the metals. Nevertheless, the EF and K_NRF both reveal moderate to significant anthropogenic contamination of Cr, Cu, Ni, and Zn in the surface sediments of Laoyun River and the estuary and Cr in the surface sediments of Baima River. The proportion of non-residual fractions (acid soluble, reducible, and oxidizable fractions) of Cr, Cu, Ni, and Zn in the contaminated sediments increased to 37–99% from the background levels less than 30%.     

Application of geoaccumulation index and enrichment factor for assessing metal contamination in the sediments of Kafrain Dam, Jordan

An investigation is reported of the degree of metal pollution in the sediments of Kafrain Dam and the origin of these metals. Fourteen sampling sites located at Kafrain Dam were chosen for collecting the surface, cutbank, and dam bank sediment samples. The sediment samples have been subjected to a total digestion technique and analyzed by atomic absorption spectrometer for metals including Pb, Zn, Cd, Ni, Co, Cr, Cu, Mn, and Fe. XRD analyses indicate that the sediments of Kafrain Dam are mainly composed of calcite, dolomite, quartz, orthoclase, microcline, kaolinite, and illite reflecting the geology of the study area. The enrichment factor (EF) and geoaccumulation index (I _geo) have been calculated and the relative contamination levels assessed in the study area. The calculations of I _geo are found to be more reliable than of those of EF. The enrichment of metals in the study area has been observed to be relatively high. I _geo results reveal that the study area is not contaminated with respect to Ni, Co, Cr, Cu, and Mn; moderately to strongly contaminated with Pb; and strongly to extremely contaminated with Cd and Zn. The high contents of Pb, Cd, and Zn in the study area result from anthropogenic activities in the catchment area of the dam site. These sources mainly include the agricultural activities, sewage discharging from various sources within the study area (effluent of wastewater treatment plants, treated and untreated wastewaters, and irrigation return water), and the several industries located in the area. Degrees of correlations among the various metals in the study area are suggested by the results and the intermetallic relationship.     

Risk assessment for salmon from water quality changes following timber harvesting

Land use activities may affect surface water quantity and quality. Water quality changes (concentration increases) from land use activities that are above background but below the water quality standard or criteria have always been considered benign. Increased public interest and recent legislation and management regarding threatened, or endangered, salmon populations suggest that environmental influences on these populations need to be reevaluated.As one approach, we developed a risk assessment (toxicity and exposure) for salmon from water quality changes following timber harvesting. Toxicity relationships for nitrate-nitrogen (as an LC₅₀) using chloride, suspended sediment, and exposure were developed from the literature and data from the Alsea Watershed Study in the Oregon Coast Range. These relationships were used to predict the probable risk to coho salmon (Oncorhynchus kisutch) to nitrate-nitrogen exposure.The control or reference catchment, Flynn Creek, had higher nitrate-nitrogen concentrations, but showed little likelihood of risk to salmon because of lower suspended sediment concentrations. The treated catchment, Needle Branch (harvested 27 years ago), had lower nitrate-nitrogen concentrations and was expected to have less risk to salmon. However, the risk assessment relationship exhibited sensitivity to suspended sediment concentrations. This smaller catchment had higher suspended sediment transport and thus a higher risk of nitrate-nitrogen exposure to salmon. The suspended sediment transport functions were based on post-treatment monitoring (1966–1973) and are not considered to represent the current situation. These findings are not meant to be categorical, but merely illustrative of this risk assessment application.     

Modeling of Hydrodynamics and Cohesive Sediment Processes in an Estuarine System: Study Case in Danshui River

The Danshui River estuarine system is the largest estuarine system in northern Taiwan and is formed by the confluence of Tahan Stream, Hsintien Stream, and Keelung River. A comprehensive one-dimensional (1-D) model was used to model the hydrodynamics and cohesive sediment transport in this branched river estuarine system. The applied unsteady model uses advection/dispersion equation to model the cohesive sediment transport. The erosion and deposition processes are modeled as source/sink terms. The equations are solved numerically using an implicit finite difference scheme. Water surface elevation and longitudinal velocity time series were used to calibrate and verify the hydrodynamics of the system. To calibrate and verify the mixing process, the salinity time series was used and the dispersion coefficient of the advection/dispersion equation was determined. The cohesive sediment module was calibrated by comparing the simulated and field measured sediment concentration data and the erosion coefficient of the system was determined. A minimum mean absolute error of 4.22 mg/L was obtained and the snapshots of model results and field measurements showed a reasonable agreement. Our modeling showed that a 1-D model is capable of simulating the hydrodynamics and sediment processes in this estuary and the sediment concentration has a local maximum at the limit of salinity intrusion. Furthermore, it was indicated that for Q ₅₀ (the flow which is equaled or exceeded 50% times), the turbidity maximum location during neap tide is about 1 km closer to the mouth compared to that during spring tide. It was found that deposition is the dominant sediment transport process in the river during spring–neap periods. It was shown that, while sediment concentration at the upstream depends on the river discharge, the concentration in the downstream is not a function of river discharge.     

Water and sediment quality in Qinghai Lake,China: a revisit after half a century

Qinghai Lake, situated on the Qinghai–Tibet plateau, is the largest lake in China. In this study, the water and sediment quality were investigated in Qinghai Lake, three sublakes, and five major tributaries. Both Na⁺ and Cl^? were found to be the major ions present in Qinghai Lake and the three sublakes, while Ca²⁺ and HCO^3? dominated the tributaries. Compared with historical data from the 1960s, the concentrations of NH₄ ⁺, NO₃ ^?, and soluble reactive silica have increased considerably, likely caused by increased human activities in the area. Compared to the historical data, chemical oxygen demand has increased and lake water transparency has decreased, likely related to an increase in nutrient levels. Relatively high concentrations of total nitrogen (TN) and total phosphorus (TP) were observed in Qinghai Lake sediments, although P fraction types and low water concentrations of these two indicate low possibility of transfer into the water column. The ratios of C/N suggest that the organic matter in the sediments are primarily from autochthonous sources. TN and total organic carbon in the sediment cores increased slowly up the core while TP and total inorganic carbon have been fairly constant.     

Spatio-temporal variations of carbon dioxide and its gross emission regulated by artificial operation in a typical hydropower reservoir in China

Supersaturation and excess emission of greenhouse gases in freshwater reservoirs have received a great deal of attention in recent years. Although impoundment of reservoirs has been shown to contribute to the net emission of greenhouse gases, reservoir age, geographical distribution, submerged soil type and artificial regulation also have a great impact on their emissions. To examine how large scale reservoir operation impact the water column CO₂ and its air–water interface flux, a field study was conducted in 2010 to evaluate potential ecological processes that regulate the partial pressure of CO₂ (pCO₂) in the water column in the Pengxi River backwater area (PBA), a typical tributary in the Three Gorges Reservoir, China. Measurements of total alkalinity (TA), pH and water temperature were applied to compute the pCO₂. And this approach was also validated by calculation of pCO₂ from the dissolved inorganic carbon data of samples. Partial least squares (PLS) regression was used to determine how the dynamics of the water pCO₂ were related to the available variables. The estimated pCO₂ in our sample ranged from 26 to 4,087 μatm in the surface water. During low water operation from July to early September, there was an obvious pCO₂ stratification, and pCO₂ in the surface was almost unsaturated. This phenomenon was also observed in the spring bloom during discharge period. Conversely, there was no significant pCO₂ stratification and the entire water column was supersaturated during high water operation from November to the following February. Significant correlation was observed between the magnitude of pCO₂, DO and chlorophyll a, suggesting that phytoplankton dynamics regulate pCO₂ in the PBA. The average areal rate of CO₂ emissions from the Pengxi River ranged from 18.06 to 48.09 mmol m^?2 day^?1, with an estimated gross CO₂ emission from the water surface of 14–37 t day^?1 in this area in 2010. Photosynthesis and respiration rates by phytoplankton might be the dominant processes that regulated pCO₂ in the water column. We conclude that pCO₂ values in the surface water of Pengxi River could be regarded as potential sources of CO₂ to the atmosphere were smaller or similar to those that have been reported for many other reservoirs to date.     

Longitudinal distribution of heavy metals in sediments of a canyon reservoir in Southwest China due to dam construction

In this study, the longitudinal distribution of heavy metals (including As, Cd, Cr, Cu, Ni, Pb, and Zn) from sediment of a 70-km long canyon reservoir in Yunnan Province was investigated and their potential ecological risks were assessed. The results indicated that the concentration of all the detected metals in the sediments that was sampled near the dam was much higher than that sampled from upstream far from the dam. The geoaccumulation index (I _geo) and contamination factors (CF) suggested that Cd was the most important contamination factor, followed by As and Zn, while the concentration of Cr, Cu, Ni, and Pb was at uncontaminated levels. Cd posed a high potential ecological risk in the sediment. Furthermore, potential ecological risk is significantly correlated with the distance from the dam.     

Assessment Of A Natural Wetland For Use In Wastewater Remediation

An environmental study was conducted to assess various aspects of the water and sediment quality of a natural wetland to determine its feasibility for advanced wastewater treatment in Louisiana. Nitrate (NO₃), nitrite (NO₂), ammonia (NH₄), total Kjeldahl nitrogen (TKN), total phosphorus, chloride, total organic carbon, pH, trace metals, fecal coliform, dissolved oxygen (DO), and biochemical oxygen demand (BOD) were monitored. Productivity of a dominant shrub, Iva frutescens, in the wetland was also assessed. Research results indicated that gradients of chloride and salinity concentrations showed a broad mixing of the discharged fresh water into the more saline natural brackish waters. This provided an ideal pattern for nutrient assimilation by the receiving marsh. NH₄ was reduced in the range of 50–100% when all combinations of sources and outflows were considered. For total phosphorus and TKN, reduction ranged from 0–95.1% and 11.2–89.7%, respectively. Some nutrient concentrations in the effluent outlet, NO₃ in particular, were lower than background concentrations found in the reference wetland. Sediment and water showed no significant deficiency or toxicity problems for the major nutrients and metals analyzed. The secondary effluent discharges had little demonstrable negative impact on the wetland during the study period from 1995 to 1996.     

Effects of cement flue dusts from a Nigerian cement plant on air, water and planktonic quality

Effects of cement flue dust from Ewekoro cement Kilns were monitored at some aquatic receptor locations. High levels of total suspended particulates (TSPs) and atmospheric deposition rates (ADRs) were recorded within the factory compared to ancillary locations outside the factory. The TSP and ADR levels which were location dependent were significantly higher (P?<?0.05) during the dry periods than in the wet season. Irrespective of seasonal variations, the key elements in the emissions were Ca^2?+? and Fe^2?+?. The concentrations of Zn^2?+?, Mn^2?+? and Pb^?+? which were trace elements were significantly higher (P?<?0.05) in the deposited than in the airborne particulates. The planktonic flora and fauna of the river systems draining the area were poor with 16 phytoplanktonic and nine zooplanktonic species. Numerically, the phytoplanktons were dominated by diatoms (Bacillariophyta) with Synedra sp. being the most abundant species. The zooplanktonic fauna dominated by rotifers had Lecane curvicornis as a regular occurrence in all the three catchment rivers. The physicochemical parameters assayed were significantly higher (P?<?0.05) in the factory effluent discharges than in water samples from each of the catchment rivers. Seasonal variations inclusive, HCO $_{3}^{-}$ , CO $_{3}^{2-}$ , Ca^2?+? and Mg^2?+? constituted the major ionic component of water samples analysed irrespective of location. Alaguntan River which receives effluents directly from the factory had significantly higher levels (P?<?0.05) of the assayed ions than the other two rivers draining the cement factory catchment areas.     

Dry deposition velocity of atmospheric nitrogen in a typical red soil agro-ecosystem in Southeastern China

Atmospheric dry deposition is an important nitrogen (N) input to farmland ecosystems. The main nitrogen compounds in the atmosphere include gaseous N (NH₃, NO₂, HNO₃) and aerosol N (NH₄ ⁺/NO₃ ^?). With the knowledge of increasing agricultural effects by dry deposition of nitrogen, researchers have paid great attention to this topic. Based on the big-leaf resistance dry deposition model, dry N deposition velocities (V _d) in a typical red soil agro-ecosystem, Yingtan, Jiangxi, Southeastern China, were estimated with the data from an Auto-Meteorological Experiment Station during 2004–2007. The results show that hourly deposition velocities (V _dh) were in the range of 0.17–0.34, 0.05–0.24, 0.57–1.27, and 0.05–0.41 cm/s for NH₃, NO₂, HNO₃, and aerosol N, respectively, and the V _dh were much higher in daytime than in nighttime and had a peak value around noon. Monthly dry deposition velocities (V _dm) were in the range of 0.14–0.36, 0.06–0.18, and 0.07–0.25 cm/s for NH₃, NO₂, and aerosol N, respectively. Their minimum values appeared from June to August, while their maximum values occurred from February to March each year. The maximum value for HNO₃ deposition velocities appeared in July each year, and V _dm(HNO₃) ranged from 0.58 to 1.31 cm/s during the 4 years. As for seasonal deposition velocities (V _ds), V _ds(NH₃), V _ds(NO₂), and V _ds(aerosol N) in winter or spring were significantly higher than those in summer or autumn, while V _ds(HNO₃) in summer were higher than that in winter. In addition, there is no significant difference among all the annual means for deposition velocities (V _da). The average values for NH₃, NO₂, HNO₃, and aerosol N deposition velocities in the 4 years were 0.26, 0.12, 0.81, and 0.16 cm/s, respectively. The model is convenient and feasible to estimate dry deposition velocity of atmospheric nitrogen in the typical red soil agro-ecosystem.     

Bioaccumulation factors and multivariate analysis of heavy metals of three edible fish species from the Barekese reservoir in Kumasi,Ghana

The Barekese reservoir has seen persistent degradation for decades through anthropogenic activities within its catchment. In spite of this, heavy metal pollution profile of fish species of the reservoir is not well studied. Total concentrations of Hg, Cd, Ni, and Cr were analyzed in muscle tissues of 45 edible fish species comprising (Tilapia zilli, Oreochromis niloticus, and Heterotis niloticus) from the reservoir. The examined fish species showed varying bioaccumulative factors for detected metals. A PCA biplot revealed that Cd showed association with all examined fish species used in the study indicating that Cd in the reservoir is biologically available for uptake by all examined fish species. A dendrogram of cluster analysis also revealed that Cd and Cr are in one cluster indicating their associations and similarities to a common anthropogenic source. The study suggests that anthropogenic activities are possible sources of heavy metal pollution in the Barekese reservoir and, hence, the examined fish species could be used to monitor the levels of Ni, Cr, Hg, and Cd in the reservoir.