Research Papers by Harold Wilson Tumwitike Mapoma, PhD, MIEnvSc
SN Applied Sciences, 2020
Understanding the levels and associated ecological risk caused by heavy metals is important for t... more Understanding the levels and associated ecological risk caused by heavy metals is important for the sustainable management and utilization of Lake Chilwa catchment, an important ecosystem in Malawi providing fertile lands for agriculture and a designated wetland ratified by the Ramsar convention in 1997. Concentrations of chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), zinc (Zn), arsenic (As), mercury (Hg) and cadmium (Cd) were analyzed from 22 soil sampling locations. Extraction and quantification were achieved by microwave digestion and Inductively Coupled Plasma Optical Emission Spectrometer, respectively. Mean values were detected in the following order; Zn > Cr > Ni > Cu > Pb > As. Strong correlations were observed between As and Pb (r = 0.85), Cr and Ni (r = 0.82), Cu and Ni (r = 0.81), Cr and Cu (r = 0.8), and Pb and Zn (r = 0.73) suggesting similar sources of input. Principal component analysis revealed that Cu, Pb, Zn and As originate from anthropogenic activities, while Cr and Ni were geogenic. The ecological risk caused by these metals, calculated by the Ecological Risk Index (RI) method, showed a low to moderate ecological risk. The wetland areas had higher overall concentrations and RI values compared to the rest of the catchment. It is therefore important to enforce measures to manage and control these levels to avoid their damaging effects
Sustainable Water Resources Management, Apr 20, 2021
Water quality assessment for water resource protection and management is key towards sustainable ... more Water quality assessment for water resource protection and management is key towards sustainable provision of potable water supply and in meeting sustainable development goals (SDGs) linked to clean water and sanitation. The spatial and temporal aspects of groundwater quality in the Nseleni catchment, South Africa (SA) was investigated, its suitability for domestic use was considered, and required protection measures were established. Using a hybrid approach methodology based on multiple water quality resource assessment techniques such as groundwater quality index (GQI) and concentration duration curves (CDCs), 72 groundwater samples collected from 1994 to 2017 were analysed for physico-chemical (Na+, Ca 2+, Mg 2+, Cl−, SO 4 2−, NO 3−, F−, EC, pH) parameters. Approximately, 33.3% of groundwater samples in the Nseleni catchment were found suitable for drinking when compared to South African water quality guidelines. The use of a hybrid approach method showed that overall groundwater quality in the study catchment was classified as excellent for domestic water use when the groundwater quality index was calculated to be 39.11. Groundwater quality reserve limits for groundwater resources protection were determined for the nine water quality parameters using CDCs. The study concluded that using groundwater quality index and concentration duration curves, it was feasible to classify groundwater resources for improved groundwater quality of reserve determination in the South African context. The study recommends the application of the hybrid method in various catchments of similar characteristics to the studied catchment for setting groundwater quality limits that would contribute towards achieving the goal of groundwater resources protection in other catchments.
Water, Jan 5, 2022
Heavy metals may cause acute and chronic toxic effects to humans and other organisms, hence the n... more Heavy metals may cause acute and chronic toxic effects to humans and other organisms, hence the need to treat wastewater properly, as it contains these toxicants. This work aimed at assessing zinc, copper, cadmium, and chromium in water, soil, and plants that are irrigated with effluent from Manase and Soche Wastewater Treatment Plants (WWTPs) in Blantyre, Malawi. Atomic Absorption Spectrophotometry (AAS) was used to assess the heavy metals. Heavy Metal Health Risk Assessment (HMHRA) on plants (vegetables) around both WWTPs was also conducted. Average daily dose (ADD) and target hazard quotients (THQ) were used to assess HMHRA. Physicochemical parameters were determined using standard methods from American Public Health Association (APHA). The heavy metal ranges were below detection limit (BDL) to 6.94 mg/L in water, 0.0003 to 4.48 mg/kg in soil, and 3 to 32 mg/L in plants. The results revealed that plants irrigated with effluent from WWTP had high values of aforementioned metals exceeding the Malawi Standards and WHO permissible limits. Furthermore, the health risk assessment values showed that vegetables consumed for a long period of time from Manase WWTP were likely to cause adverse health effects as compared to those from Soche WWTP.
Journal of Fundamental and Applied Sciences, 2020
This study was carried out to assess the short-term exposure to respirable particulate matter (PM... more This study was carried out to assess the short-term exposure to respirable particulate matter (PM2.5) from biomass combustion. A total of 24 households were sampled from two rural villages in Lilongwe, viz Nsabwe and Bauleni villages. Levels of particulate matter were measured using a portable gas detector. Indoor mean concentrations of PM2.5 ranged from 457 to 698 µg/m 3 , with no significant difference between the two villages, suggesting exposure to similar levels. The observed levels are far above the recommended WHO limit for indoor air, posing a great health risk, more especially to women and children who frequently visit the cooking areas. There is therefore need to widen appropriate intervention measures to reduce the current levels of indoor air pollution in the rural areas.
Environmental Science and Pollution Research, Oct 19, 2019
The current studies had already revealed the hydrocarbons could migrate from relatively high hydr... more The current studies had already revealed the hydrocarbons could migrate from relatively high hydrocarbon potential stratum to shallow groundwater by corrosion emission and extraction emission in karst area and further impact on human health. Then, the comprehensive experiments were used to understand the mechanism and process of hydrocarbon emission as a continuation of a long-term study on original high hydrocarbon groundwater in shallow Triassic aquifer, taking northwest Guizhou, China, as a reference. The results determined water-rock interaction that lead to the hydrocarbon emission into groundwater with salinity acting as the main driving force. Relatively high salinity promotes the rock corrosion and hydrocarbon emission in the study area. The hydrocarbon emission process varied with different strata, as the results show that the hydrocarbon uniformly distributed in T2g3 than that in T1yn4. Furthermore, the stratum with uniformly distributed hydrocarbon would likely contain high hydrocarbon groundwater, as determined by the process of sedimentation. In addition, “corrosion rate estimation method” and “mineral constituent estimation method” were firstly employed to estimate the hydrocarbon concentration in groundwater to date. Compared with the hydrocarbon concentration of local groundwater samples (0 to 0.14 mg L−1), the result of “mineral constituent estimation method” was analogous to measured value of groundwater samples in the area (0.05 to 0.50 mg L−1), indicating the concentration of hydrocarbon could be estimated by mineral constitutions of groundwater, which was related to the concentration of Ca2+ and Mg2+. Based on the methods and theories in this study, the concentration of original hydrocarbon in shallow groundwater could be estimated and help to understand the mechanism of water-rock interaction in shallow aquifer and original high hydrocarbon groundwater strategic assessment
International Journal of Environmental Science and Technology, 2019
The study assessed heavy metals (Cd, Cu, Fe, Mn, Pb and Zn) and physico-chemical parameters in wa... more The study assessed heavy metals (Cd, Cu, Fe, Mn, Pb and Zn) and physico-chemical parameters in water, sediments and fish from an endorheic lake (Lake Chilwa) in Malawi. It was observed that pH (max. 9.7), EC (max. 2936 μS/cm), TDS (max. 2119 mg/L), NO3− (max. 6.6 mg/L) and PO43− (max. 1.3 mg/L) were higher in the dry season than in the rainy season. Pb was not detected in all samples. However, the rest of heavy metals were detected with significant values of Mn and Cu in fish (Mn: 0.015–1.18 mg/kg dry weight, dw; Cu: 0.41–0.92 mg/kg dw) and sediment (Mn: 2.25–10.66 mg/kg dw; Cu: n.d–1.63 mg/kg dw). The concentrations of heavy metals in fish samples were below the maximum limits for edible fish recommended by Food and Agriculture Organization/World Health Organization: Cd (0.1 mg/kg), Cu (3 mg/kg), Fe (43 mg/kg), Pb (0.2 mg/kg), Mn (2–9 mg/kg) and Zn (60 mg/kg). The calculated target hazard quotients (ranged from 0.001 to 1.07) indicated no human risks from fish consumption. Furthermore, dry season values for Mn, Cu and Zn in sediments were significantly higher (p < 0.05) than those of the rainy season. Conversely, Fe in sediments was significantly higher (p < 0.05) in the rainy season than in the dry season. The use of fertilizer and indiscriminate disposal of metal products contributes to the observed levels. This calls for reinforcement of suitable agricultural and waste management practices in the study area.
This study used a total of 474 groundwater samples analyzed from 2014 data to evaluate the distri... more This study used a total of 474 groundwater samples analyzed from 2014 data to evaluate the distribution of groundwater quality in the Water and Sanitation Agency (WASA) jurisdiction of Lahore city, Pakistan. The study further assessed the variations in suitability of groundwater for drinking (emphasis on arsenic and fluoride) and irrigation using spatial correlation technique in GIS. The hydrochemical analysis revealed a predominance of Mg-Ca-HCO3-SO4 and Ca-Mg-HCO3-SO4 type. Distribution analysis indicated relatively higher salinity (TDSmax = 1667 mg/L), total hardness (THmax = 558 mg/L), and alkalinity (HCO3−max = 584 mg/L) in the south-eastern region of the city, while the central part displayed the highest levels of SO4 and NO3. Also, the eastern region (north-south) of Lahore had significantly elevated As concentrations (up to 86 μg/L). The order of exceedance in terms of arsenic was Gunj Bakhsh town (17.4%), Nishter town (16.4%), Iqbal town (9.8%), Aziz Batti and Shalimar town (8.1%), and Ravi town (3%). The groundwater was classified as average saline to highly saline, except few samples in Aziz Batti/Shalimar town that were in non-saline group. Otherwise, the various indices classified the groundwater for irrigation as generally acceptable. With the various irrigation quality indices displaying discernible variations for the entire study area, it was observed from the distribution maps that the groundwater suitability for irrigation is relatively excellent in the areas away from industries and landfill locations. Also, the chloride analysis shows 98.7% of the groundwater samples belong to the very fresh and fresh water class. Thus, continued monitoring and studying the changes in groundwater quality in Lahore is imperative.
A review of Japan’s fungicide usage from the 1960s to recent times was conducted using data from ... more A review of Japan’s fungicide usage from the 1960s to recent times was conducted using data from the National Institute of Environmental Studies, Japan. A total of 16 commonly used fungicides were assessed and these are: captan, chlorothalonil, fenarimol, ferbam, fosetyl-Al, iprodione, isoprothiolane, mancozeb, mepronil, metalaxyl, myclobutanil, pencycuron, thiophanate-methyl, tolclofos-methyl, triadimefon and trifloxystrobin. The assessment revealed that the most used fungicide within the period (1962–2014) was chlorothalonil with a maximum usage amount of 1795 tons/year. The least used was found to be myclobutanil with a maximum usage amount of 8 tons/year within the same reporting period. Generally, the usage of most of the fungicides peaked between the 1980s to early 2000s. For most of these fungicides, their usage amounts have decreased in recent times. However, the continuous usage of these fungicides has a potential to cause problems in the environment ranging from mere irritations to being very toxic to human beings and organisms.
In this study, twenty one (21) trace elements in the basement complex groundwater of Blantyre dis... more In this study, twenty one (21) trace elements in the basement complex groundwater of Blantyre district, Malawi were analyzed. The majority of the analyzed trace elements in the water were within the standards set by World Health Organization (WHO) and Malawi Standards Board (MSB). But, iron (Fe) (BH16 and 21), manganese (Mn) (BH01) and selenium (Se) (BH02, 13, 18, 19 and 20) were higher than the WHO and MSB standards. Factor analysis (FA) revealed up to five significant factors which accounted for 87.4% of the variance. Factor 1, 2 and 3 suggest evaporite dissolution and silicate weathering processes while the fourth factor may explain carbonate dissolution and pH influence on trace element geochemistry of the studied groundwater samples. According to PHREEQC computed saturation indices, dissolution, precipitation and rock-water-interaction control the levels of trace elements in this aquifer. Elevated concentrations of Fe, Mn and Se in certain boreholes are due to the geology of the aquifer and probable redox status of groundwater. From PHREEQC speciation results, variations in trace element species were observed. Based on this study, boreholes need constant monitoring and assessment for human consumption to avoid health related issues.
This study used multivariate analysis and geochemical modeling to appreciate the trace element ev... more This study used multivariate analysis and geochemical modeling to appreciate the trace element evolution in North Rukuru–Songwe alluvial aquifer of northern Malawi. From the isotopic studies, the δ2H/δ18O ratios revealed that groundwater is of meteoric origin through vertical recharge and mixing processes. The isotopic depletion along the west–east transect is due to mixing and fractionation processes. Generally, the d-excess value approximated the y-intercept of global meteoric water line of 10, which ruled out the influence of secondary evaporative processes on isotopic variation. Hierarchical cluster analysis identified four distinct clusters (C1, C2, C3 and C4) in the study area. Among these four clusters, it was observed that C1 had relatively high median concentrations of Fe (716.7 µg/L), Cr (0.85 µg/L), Pb (7.90 µg/L) and Sb (3.80 µg/L), while C2 was characterized by high levels of Cu (3.20 µg/L). Cluster 3 was comparably defined by high median levels of F (1.00 mg/L) and Mn (338 µg/L), while C4 revealed high median concentrations of As (8.70 µg/L), Ba (635 µg/L), Li (22.2 µg/L), Ni (2.80 µg/L), Se (6.20 µg/L) and Sr (677 µg/L). Clusters C1 and C4 described a flow path along the North Rukuru River, which is characterized by higher levels of evaporites as shown by higher concentrations of Na, K, Cl and SO4. It was also observed that this path was defined by high levels of HCO3 and total hardness. The principal component analysis suggests that carbonate dissolution and silicate weathering are the main mineralization control mechanisms. Furthermore, it is revealed that samples in the west had higher factor scores for As, Ba, Li, Ni, Se and Sr (with higher TDS), while the eastern is characteristic of higher heavy metals (Fe and Pb). Geochemical modeling using PHREEQC showed that surface complexation reactions significantly impact trace elements of higher redox state. In addition, inverse modeling confirms the significance of carbonate dissolution, silicate weathering and cation exchange processes along the North Rukuru River flow path.
The purpose of this research was to characterize the quality of groundwater for drinking and irri... more The purpose of this research was to characterize the quality of groundwater for drinking and irrigation in Blantyre, Malawi as well as identify some geochemical processes governing mineralization of major and some minor elements. The aquifer studied is part of the extensive crystalline basement complex. The suitability and classification involved confirmatory analysis of the results with World Health Organization and Malawi Standards Board groundwater guideline values. The water samples were analyzed for major descriptors (pH, Temperature, turbidity, major ions, total dissolved solids and electrical conductivity (EC), using standard methods. Besides, arsenic, iron and fluoride were analyzed as well. Multivariate statistics (especially Hierarchical Cluster Analysis and Factor Analysis), hydrographical methods (i.e. Piper diagram) and geochemical modeling programs (AquaChem and PHREEQC) were used to characterize the quality and explain the sources and evolution of groundwater. Suitability of groundwater for irrigation was assessed using Wilcox method which identified BH01, BH16 and BH21 as high salinity areas. Incidentally, the three boreholes had relatively higher sulfate and nitrate concentrations than the rest. Nevertheless, the groundwater was found to be within acceptable limits for drinking quality except elevated concentrations of nitrate, fluoride and iron in some boreholes compared with WHO standards, despite meeting the national standards. Borehole BH01, BH02, BH07, BH13 and BH18 exhibited nitrate concentrations greater than national standards (45 mg/L) an indication of groundwater contamination. Furthermore, the groundwater is slightly acidic to slightly above neutral with total dissolved solids less than 500 mg/l. Generally, groundwater was undersaturated with respect to both calcite and dolomite while oversaturated with respect to halite, goethite and hematite. Silicate and carbonate weathering were identified as main mineral sources for major ions in groundwater. There is a dire need for more studies and monitoring of the groundwater in this area to safeguard the resource and human health.
This paper investigated the hydrogeochemical characteristics influencing water quality, and asses... more This paper investigated the hydrogeochemical characteristics influencing water quality, and assessed the groundwater quality for domestic and irrigation purposes in two districts of Salima and Nkhotakota in Malawi. Data was compiled from water quality surveillance reports of water sources constructed by sponsorship from WaterAid Malawi programme. A water quality index (WQI) was used to measure suitability of groundwater for domestic purposes. Electrical conductivity, total dissolved solids and various indices were used to measure quality of water for irrigation. Anion chemistry showed a general dominance of HCO3, while Ca2+ was the dominant cation. The pH of groundwater in Salima was neutral and of Ca-HCO3/Na type; while in Nkhotakota it was slightly acidic and of Ca-Na/Mg type. It was determined that Ca, Mg,SO4 and HCO3 originated from release of carbonates (calcite or dolomite) in both districts and from gypsum in Salima district only. Although turbidity, pH and EC exceeded drinking water standards, the WQI showed the water to be suitable for consumption. It was therefore recommended to educate communities on household water treatment methods. Continual monitoring of these water sources with unacceptable standards was also proposed to be a priority.
Each year, increasing numbers of international students enroll in Chinese universities, yet no li... more Each year, increasing numbers of international students enroll in Chinese universities, yet no literature is available on their intercultural communication competences (ICC) and acculturation status. The study aimed at investigating these two key concepts at Central China Normal University. Two dimensions of intercultural communication competence (affect and behavior) and two dimensions of acculturation (attitude towards maintenance of one’s culture and attitude towards contact with other cultures) were employed to measure and analyze the two research constructs. A representative sample
of 302 international students shows that Asian international students are less motivated to adapt than other students from other continents. In addition, time and education level do not seem to be sufficient factors in facilitating adaptation. Furthermore, the most preferred acculturation strategy is found to be integration. Finally, attitude towards contact positively correlates with affect and behavior. However, there is no relationship between attitude towards cultural maintenance and the two dimensions of ICC. These findings suggest that a better understanding of intercultural communication competence and acculturation, as well as of factors that help facilitate adjustment to the new culture, are essential in assisting Chinese universities to come up with effective programs that enhance contact between cultures.
The hydrogeochemical influence of the Xikuangshan antimony mine on groundwater quality was investi... more The hydrogeochemical influence of the Xikuangshan antimony mine on groundwater quality was investigated by analyzing groundwater from 24 springs in the area for major and trace elements. The samples had a pH of 7.6–8.5; total dissolved solids ranged from 125 to 607 mg/L. The groundwater was dominated by alkaline earths (Ca & Mg) over the alkalis (Na & K), and weak acids (HCO3) over strong acids (SO4 & Cl). Calcite was generally supersaturated and gypsum was always undersaturated, while dolomite was undersaturated in 34 % of the samples. Iron was negatively correlated with Ca, Mg and SO4 , which is consistent with Fe removal during acid buffering. Scatter diagrams and correlation coefficients between the major ions indicate dissolution of carbonates and gypsum as major processes, which could promote calcite precipitation.
More than 7 million people of Lahore city, Pakistan, use groundwater for drinking and other house... more More than 7 million people of Lahore city, Pakistan, use groundwater for drinking and other household purposes. The quality of drinking water from source and distribution system was investigated, and the hydrochemical characteristics and formation mechanisms of groundwater were analyzed. Statistical summary showed higher mean values of major descriptors in distributed groundwater samples compared with source groundwater samples. A total of 50 drinking water samples (16 from source, and 34 from distribution system) were examined for physical, chemical and bacteriological parameters, including pH, turbidity, electrical conductivity, total dissolved solids, total hardness, total alkalinity, Ca2+, Mg2+, Na+, K+, SO4 2−, Cl−, NO3 −, F−, arsenic (As) chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), cadmium (Cd) and lead (Pb). Varying concentrations of trace amounts of Cr (in 8 samples), Fe (18 samples), Cu (18 samples), Zn (13 samples) and Pb (14 samples) were detected. However, the detected trace elements were within the WHO permissible limits for drinking water except Pb where 5 out of 14 samples showed higher than WHO limit value (Pb > 0.01 mg/L). 19 out of 50 samples (6 from source and 13 from distributed samples) showed high values of alkalinity (>250 mg/L). All of 16 groundwater samples from source exceeded 0.01 mg/L WHO limit value for arsenic (As). On the basis of bacteriological analysis, 42 % samples (12 % from source, 55 % from distribution) did not meet WHO guidelines and were unsafe for drinking, especially distributed groundwater samples. Mg–HCO3 contents predominated the groundwater type followed by Ca–HCO3. Carbonate weathering was revealed to be the dominant process controlling dissolution/precipitation processes. PHREEQC modeling showed that the aqueous phase was undersaturated with respect to significant gypsum, halite and mirabilite while equilibrium to saturated with respect to aragonite, calcite and dolomite was observed. Principal component analysis (PCA) revealed that the concentration of As was strongly associated with that of SO4 2−. Reductive dissolution and pH-dependent desorption are the plausible processes responsible for the observed high As concentrations in Lahore.
Research paper, Mar 2015
Prospecting studies indicate that Rwanda has a potential capacity to generate geothermal energy i... more Prospecting studies indicate that Rwanda has a potential capacity to generate geothermal energy in the volcano-tectonically active zones of the East African Rift System (EARS). Two typical regions, Gisenyi and Mashyuza, were reevaluated
for the geothermal potential in Rwanda, where the hot springs were of Na-HCO3 type waters. Geothermometers were applied to estimate subsurface temperatures of Gisenyi and Mashyuza springs and their suitability were discussed using Na-K-Mg diagram. In contradiction to previous studies, the results showed that only K-Mg geothermometer provided reliable estimations for Gisenyi and Mashyuza prospects for which reservoir temperatures are too low for energy production.
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Research Papers by Harold Wilson Tumwitike Mapoma, PhD, MIEnvSc
of 302 international students shows that Asian international students are less motivated to adapt than other students from other continents. In addition, time and education level do not seem to be sufficient factors in facilitating adaptation. Furthermore, the most preferred acculturation strategy is found to be integration. Finally, attitude towards contact positively correlates with affect and behavior. However, there is no relationship between attitude towards cultural maintenance and the two dimensions of ICC. These findings suggest that a better understanding of intercultural communication competence and acculturation, as well as of factors that help facilitate adjustment to the new culture, are essential in assisting Chinese universities to come up with effective programs that enhance contact between cultures.
for the geothermal potential in Rwanda, where the hot springs were of Na-HCO3 type waters. Geothermometers were applied to estimate subsurface temperatures of Gisenyi and Mashyuza springs and their suitability were discussed using Na-K-Mg diagram. In contradiction to previous studies, the results showed that only K-Mg geothermometer provided reliable estimations for Gisenyi and Mashyuza prospects for which reservoir temperatures are too low for energy production.
of 302 international students shows that Asian international students are less motivated to adapt than other students from other continents. In addition, time and education level do not seem to be sufficient factors in facilitating adaptation. Furthermore, the most preferred acculturation strategy is found to be integration. Finally, attitude towards contact positively correlates with affect and behavior. However, there is no relationship between attitude towards cultural maintenance and the two dimensions of ICC. These findings suggest that a better understanding of intercultural communication competence and acculturation, as well as of factors that help facilitate adjustment to the new culture, are essential in assisting Chinese universities to come up with effective programs that enhance contact between cultures.
for the geothermal potential in Rwanda, where the hot springs were of Na-HCO3 type waters. Geothermometers were applied to estimate subsurface temperatures of Gisenyi and Mashyuza springs and their suitability were discussed using Na-K-Mg diagram. In contradiction to previous studies, the results showed that only K-Mg geothermometer provided reliable estimations for Gisenyi and Mashyuza prospects for which reservoir temperatures are too low for energy production.