Seasonal Variations In Concentrations Research Articles

Temporal, spatial, and seasonal variations in airborne PCDD/F and dl-PCB concentrations around Bien Hoa hot spot, Vietnam, and health risk assessments

Passive air samplers were used to monitor polychlorodibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorobiphenyls (dl-PCBs) between 2020 and 2022 in four residential areas around Bien Hoa hot spot (BHS) including Trung Dung (TD), Tan Phong (TP), Quang Vinh (QV), and Buu Long (BL). The total toxic equivalents of PCDD/Fs and dl-PCBs (∑TEQs) were highest in the TD area, from 284 to 642 fg TEQ/PUF day. Next was the QV area, where ∑TEQs ranged from 229 to 569 fg TEQ/PUF day. Then, ∑TEQs varied from 205 to 503 fg TEQ/PUF day in the TP area. The lowest ∑TEQs were between 179 and 385 fg TEQ/PUF day in the BL area. The temporal, spatial, and seasonal variations in concentrations of PCDD/Fs and dl-PCBs were related to the prevailing wind direction and the distance from each area to the dioxin hot spot. The average ∑TEQs for all four areas surrounding BHS in the dry season (423 fg TEQ/PUF day) were 1.4 times higher than in the rainy season (303 fg TEQ/PUF day). Health risk assessments from airborne dioxin exposure were estimated using the average daily doses through inhalation (ADDI). The ADDI for residents surrounding BHS ranged from 14.6 to 208 fg TEQ/kg BW/day. The ADDI values by areas were as follows: 23.2–208 fg TEQ/kg BW/day in the TD, 18.7–184 fg TEQ/kg BW/day in the QV, 16.7–163 fg TEQ/kg BW/day in the TP, and 14.6–125 fg TEQ/kg BW/day in the BL. These ADDI values remained within and below the 10% threshold of the WHO-recommended tolerable daily intake (100–400 fg TEQ/kg BW/day). It is necessary to control the excavation activities inside the BHS and cover the temporary storage sites of dioxin-contaminated materials to minimize the emissions of PCDD/Fs and dl-PCB into the ambient air.

Seasonal variability of trace elements bioaccumulation in Pacific Oysters (Crassostrea gigas) from an experimental pilot farm in the Calich Lagoon (Sardinia, Italy)

BackgroundMetals pollution is a worldwide environmental issue due to their persistence in the ecosystems, non-degradability, and bioaccumulation in marine biota. Pacific Oysters (Crassostrea gigas) are highly nutritious bivalve representing an important dietary constituent but may accumulate metals through feeding on suspended sediments from surrounding water, then represent a suitable tool for biomonitoring. Materials and methodsThe occurrence of trace elements (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Rb, Se, Sn, V, Zn) was investigated in Pacific Oysters (Cassostrea gigas) collected from Calich Lagoon in each season of 2019. Samples were homogenized and subjected to microwave acid digestion before being analyzed by inductively coupled plasma-mass spectrometer (ICP-MS). ResultsThe results showed a significant seasonal variation for temperature, dissolved oxygen, chlorophyll, and pH. Moreover, high significant seasonal variation in concentrations of Cd, Mn, Ni, and V was recorded. The highest values were found for Fe (128 mg kg⁻1 w.w.), and Al (112 mg kg⁻1 w.w.) in October, for Zn (113 mg kg⁻1 w.w.) in March and May. ConclusionsPacific Oysters were confirmed as suitable bioindicators of the health status of coastal lagoons; trace elements concentrations were highly affected by season of collection, and according to literature the highest values were recorded in autumn and summer. The EU legal limits for Cd and Pb were not exceeded, then the farmed oysters were safe to consumers.

Statistical analysis of seasonal variations in pollutant concentrations in urban atmosphere

In the context of global climate change and urbanization, the issue of air quality is becoming increasingly relevant. Air pollution poses a threat to human health and ecosystems, highlighting the need for monitoring the concentrations of pollutants. This study examines the seasonal variations in the concentrations of harmful substances in the urban atmosphere using statistical methods. The aim of the research is to analyze time series data on concentrations of carbon monoxide (CO), nitrogen oxide (NO), nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), ammonia (NH3), and particulate matter (PM2.5 and PM10). Correlation and factor analysis are employed to assess the relationships between pollutants and identify underlying factors. The analysis of data collected over several years emphasizes seasonal changes, showing that pollutant concentrations are subject to significant fluctuations driven by both natural and anthropogenic factors. The results can be used to develop strategies for improving air quality and predicting the health impacts of pollution on the population. This research deepens the understanding of the dynamics of atmospheric pollution and its seasonal dependence, which is important for shaping environmental policy and management decisions.

Physicochemical mechanisms of dissolved <sup>137</sup>CS seasonal variations in freshwaters: Fukushima and Chernobyl

Analysis of available monitoring data sets on concentrations of accidentally derived dissolved radiocesium in water bodies is indicative of two major physicochemical mechanisms responsible for their seasonal variations in water bodies in the course of the year: temperature dependence of radiocesium desorption from suspended material and ion-exchange remobilization of radiocesium by ammonium cations formed during decomposition of organic matter in anoxic conditions. An equation describing seasonal variations in concentration of dissolved radiocesium in water bodies has been derived accounting for two factors: water temperature and combined concentration of key competing cations.

Seasonal variations in concentrations of PM2.5 and tire wear particle of < 2.5 μm (TWP2.5) and polymeric components of PM2.5 at a bus stop

Air pollution is a global public health concern. Bus stops have heavy traffic and local emissions. PM2.5 was collected for 2 day at a bus stop each month for one year. Polymeric components in the PM2.5 samples were analyzed using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Seasonal variations of the polymeric components, PM2.5 concentration, and concentration of tire wear particles <2.5 μm (TWP2.5) were investigated. Various polymeric components were found, including natural rubber (NR) and curing agents from TWPs, bitumen originating from asphalt pavement wear particles (APWPs), plant-related components (PRCs), and poly (ethylene-terephthalate) (PET) from PET fabric lint. The PM2.5 concentrations at the bus stop were 4–124% higher than those in the regional background, and the annual average PM2.5 concentration at the bus stop was more than 1.5 times higher than that in the regional background. Non-exhanst sources such as abrasion of tires, brakes, and asphalt pavements, vehicle exhaust emissions, and road dust resuspension accounted for the high PM2.5 concentrations. The PM2.5 concentrations during winter were higher than those in the other seasons. On average, the additional generation of PM2.5 at the bus stop was approximately 10 μg/m3, while that in the winter was approximately 18 μg/m3. The annual average TWP2.5 concentration at the bus stop was 1.28 μg/m3 (0.7–1.8 μg/m3), and the seasonal order was winter > fall > spring > summer. TWP2.5 is directly generated by the abrasion of tire tread through the friction with the road surface and also is produced from primary TRWPs by pressing and breaking them upon the contact with tires while driving vehicles. The annual average contribution of TWP2.5 to the PM2.5 concentration at the bus stop was 5.5% (1.6–14.0%).

Seasonal heavy metal effects on detoxification and antioxidant gene expression in the urban honeybee

AbstractEnvironmental pollutants are associated with honeybee colony losses and may show seasonal concentration variations with respect to the environment and plants. In this study, we examined arsenic (As), lead (Pb), and mercury (Hg) seasonal variations in honey and honeybees in urban areas. Seasonal trends in detoxification (CYP9Q1, CYP9Q2, and CYP9Q3) and antioxidant genes encoding catalase (CAT) and superoxide dismutase (SOD1) were also determined in honeybees. Accordingly, As, Pb, and Hg concentrations were significantly increased in summer in both honey and honeybee samples when compared with other seasons. Similarly, the expression level of CYP9Q1, CYP9Q2, CYP9Q3, SOD1, and CAT showed a significant increase in summer honeybees. This increased expression level particularly in summer honeybees indicating an increased summer honeybee exposure and adaptive oxidative stress responses to environmental pollutants, including heavy metals due to increased flight activity when compared with other seasons. Thus, active season honeybees were subjected to environmental oxidative and detoxification stressors when exposed to environmental pollutants, including heavy metals.

The reactivity of dissolved and suspended particulate phosphorus pools decreases with distance downstream in the Yellow River

The Yellow River is a potentially important source of terrestrially derived phosphorus to the phosphorus limited Bohai Sea. However, seasonal variation in concentrations, partitioning and bioavailability of dissolved and particulate phosphorus along the length of the Yellow River are poorly constrained. Here, we measure dissolved and suspended particulate phosphorus at 72 stations from the source to the estuary of the Yellow River during the rainy season in 2020 and dry season in 2021. Mean concentrations of total phosphorus, total dissolved phosphorus and dissolved reactive phosphorus were higher in the rainy season than the dry season. Analysis with sequential fractionation indicated that generally phosphorus associated with calcium carbonate dominated the suspended particulate pool. However, phosphorus content and the relative contribution of iron-bound phosphorus in suspended particles increased during the dry season, suggesting seasonal variations in bioavailability. Reactivity of the phosphorus pools decreased from source to estuary, suggesting low export potential of bioavailable phosphorus to the Bohai Sea.

Airborne particulate matter in Southeast Asia: a review on variation, chemical compositions and source apportionment

Environmental context Airborne particulate matter (PM) is a major public health risk in Southeast Asia. The annual average concentration of fine PM (PM2.5) in the region is significantly higher than the WHO air quality guidelines, and higher PM2.5 levels were recorded during dry seasons, primarily due to biomass burning. In this paper, we provide an overview of the seasonal variations in concentrations, chemical compositions, and sources of PM in Southeast Asian countries. Abstract Airborne particulate matter (PM) in Southeast Asia is the most important air pollutant, causing millions of premature deaths. This review provides an overview of the levels, chemical compositions and sources of PM and compared these with studies from megacities in other regions. Daily average PM2.5 concentrations were lower than polluted megacities such as Delhi but substantially higher than 24-h mean air quality guideline of the WHO. Levels of PM2.5 in maritime continental Southeast Asia (Indonesia, Brunei, Malaysia, Philippines and Singapore) were lower than in mainland continental countries (Cambodia, Myanmar, Thailand, Vietnam, and Laos). PM levels are usually two times higher during dry than wet seasons. Organic carbon is a key chemical component, contributing 9–52% of PM mass. SO42−EN22044_IE1.gif, NO3−EN22044_IE2.gif, and NH4+EN22044_IE3.gif are major ions and NO3−EN22044_IE4.gif/SO42−EN22044_IE5.gif ratios were notably lower than in megacities in other regions, implying lower emissions from mobile relative to stationary sources. Source apportionment indicates biomass burning is one of the most important sources, particularly during the haze (dry) seasons, followed by road traffic emission in dense-traffic cities such as Bangkok, Kuala Lumpur and Hanoi. The secondary aerosols contribution to PM mass is usually lower than that in cities from other regions. We suggest future PM source apportionment studies in Southeast Asia to include both inorganic and organic tracers and apply both chemical mass balance and multivariate receptor models.

Seasonal and Spatial Variability of Dissolved Nutrients in the Yenisei River

The accelerated rates of warming in high latitudes lead to permafrost degradation, enhance nutrient cycling and intensify the transport of terrestrial materials to the Arctic rivers. The quantitative estimation of riverine nutrient flux on seasonal and spatial scales is important to clarify the ongoing changes in land–ocean connectivity in the Arctic domain. This study is focused on a multiyear (2015–2021) analysis of concentrations of dissolved nutrients in the Yenisei River. Applying stationary water sampling, we studied seasonal variations in concentrations of phosphate, nitrate, nitrite and ammonia ions in the Yenisei River in the upper (56.0° N), middle (60.9° N) and lower (67.4° N) sections of the river. The waters of the upper river section demonstrated significant and steady nutrient enrichment throughout the hydrological year, reflecting the influence of the Krasnoyarsk reservoir. The downstream reaches of the Yenisei River had more apparent seasonal patterns of nutrient concentrations. Particularly, winter-season nutrient levels in the middle and lower river sections were the highest during the hydrological year and close to the upper section. At snowmelt, and especially the summer–fall seasons, all inorganic nutrient concentrations dropped dramatically after the inflow of the Angara River. On the other hand, the peak nitrite content observed during the early spring flood was most pronounced in the lower section of the river basin, reflecting the specific characteristics of the nitrogen cycle in permafrost soils. The spring flood plays the major role in the annual nutrient fluxes, except for nitrates, for which the maximum occurred in the winter season. The summer–fall season, despite its duration and considerable water runoff, demonstrated the lowest fluxes of dissolved inorganic phosphorus and nitrogen in comparison to other periods of the hydrological year, suggesting strong biological uptake and chemostasis.

Spatial Distribution, Source Analysis and Health Risk Study of Heavy Metals in the Liujiang River Basin in Different Seasons

Three high-frequency sampling and monitoring experiments were performed at the Lutang and Luowei transects of the Liujiang River entrance and at the southeast exit of the Liuzhou during 2019 for the purpose of assessing physico-chemical variables and human health hazards of water heavy metals in different rainfall processes. There were significant seasonal variations in concentrations of 11 heavy metals and most variables showed higher levels during the dry season. The distribution of heavy metals in the Liuzhou area varied significantly by region. Pollution source analysis indicated distinct seasons of wetness and dryness. The dry season is dominated by anthropogenic activities, while the wet season is dominated by natural processes. The results of hazard quotient (HQ) and carcinogenic risk (CR) analysis showed that the health risk of non-carcinogenic heavy metals in the wet season is slightly higher than that in the dry season. Seasonal changes in carcinogenic risk are the opposite; this is due to the combined influence of natural and human activities on the concentration of heavy metals in the river. Among them, Al was the most important pollutant causing non-carcinogenic, with As being a significant contributor to carcinogenic health risk. Spatially, the downstream Luowei transect has a high health risk in both the dry and rainy seasons, probably due to the fact that the Luowei transect is located within a major industrial area in the study area. There are some input points for industrial effluent discharge in the area. Therefore, high-frequency monitoring is essential to analyze and reduce the heavy metal concentrations in the Liujiang River during dry and wet seasons in order to protect the health of the residents in the area.

Seasonal Variations in Concentrations and Chemical Compositions of TSP near a Bulk Material Storage Site for a Steel Plant

The concentrations of total suspended particles (TSPs) on four buildings near a steel plant’s bulk material storage site for iron ore, coal, limestone, and sinter were evaluated for summer and winter, where the concentrations were 58 (17–55) μg m−3 and 125 (108–155) μg m−3, respectively. A multivariate regression analysis of meteorological parameters with TSP concentrations indicates that temperature, wind speed, and frequency of rainfall are potential predictors of TSP concentrations, where the respective p values for the model are p = 0.005, p = 0.049, and p = 0.046. The strong correlation between usual co-pollutants, CO, NO2, and NOX with TSP concentrations, as indicated by the Pearson correlation values of 0.87, 0.86, and 0.77, respectively, implies substantial pollution from mobile sources. The weak correlation of SO2 with TSP concentrations rules out a significant pollution contribution from power plants. The speciation of TSPs in winter showed the percentage proportions of water-soluble ions, metal elements, and carbon content in winter as 60%, 15%, and 25%, while in summer, they were 68%, 14%, and 18%, respectively. Water-soluble ions were the most significant composition for both seasons, where the predominant species in summer and winter are SO42− and NO3−, respectively. In the TSP metal elements profile, the proportion of natural origin ones exceeded those from anthropogenic sources. The health risk assessment indicates a significant cancer risk posed by chromium, while that posed by other metal elements including Co, Ni, As, and Pb are insignificant. Additionally, all metal elements’ chronic daily occupational exposure levels were below the reference doses except for Cu and Zn. Insights from this investigation can inform decisions on the design of the TSP-capturing mechanism. Specifically, water sprays to capture the water-soluble portion would substantially reduce the amplified concentrations of TSPs, especially in winter.

Insights into factors affecting size-segregated nitrate formation in a coastal city through measurements of dual isotopes

Due to the effective control of SO2 emissions in China, nitrate becomes a key component in atmospheric aerosols, especially in haze episodes. Therefore, it is important to elucidate the formation pathways and sources of ambient NO3−. In this study, size-segregated particles were collected in Xiamen urban area from August 2019 to February 2021. Water-soluble inorganic ions and the dual isotope compositions (δ15N and δ18O) of NO3− were measured. A Bayesian isotope mixing model was used to investigate the formation pathways and contributions of different NOx sources to NO3−. The results showed that NO3− exhibited pronounced seasonal variations in concentrations and size distributions. The δ15N–NO3- and δ18O–NO3- values in different modes were lower in the warm season (May to November) than in the cold season (December to Feburary), attributing largely to the source and formation pathway changes. Bayesian model indicated that the contribution of the NO2 + ⋅OH pathway in the warm season was higher than in the cold season, and the contribution decreased with the increase of particle size. However, opposite seasonal trends were observed for N2O5 + H2O, N2O5 + Cl− and NO3 + HC pathways. The size distribution of δ15N–NO3- values was more influenced by the formation pathway than the isotopic fractionation. Results also indicated that the average contribution of soil emission (13.5%) to ambient NO3− was significantly lower than that of coal combustion (30.4%), ship emission (26.6%) and vehicle exhaust (29.6%). The contribution of soil emisison was almost double in warm season (17.7%) compared to cold season (9.3%) whereas coal combustion and vehicle exhaust decreased and ship emission remained relatively stable. Our results highlight the influence of formation pathways on the size distribution of δ15N–NO3- and the importance of after emission treatment of ship exhaust in reducing particle pollution in port cities.

DETERMINANTS OF SEASONAL VARIATIONS IN SURFACEOZONE – A STUDY IN VISAKHAPATNAM CITY OFANDHRA PRADESH, INDIA

Ozone is an important constituent of the atmosphere. It is a variable gas and even a minute changes in its composition in the vertical profile of the atmospheric gases can cause far reaching implications vis-à -vis warming of the earth and other effects. About 90% of Ozone is found in the stratosphere up to 50km the majority of which is in the height range of 10-16 km. The stratosphericozone protects the earth from the harmful effects of the Ultraviolet (UV) radiation and hence it is known as ‘good ozone’. The remaining 10% of ozone in the atmosphere hovers in the troposphere and resides on the ground which is a pollutant that is harmful to plants, animals, and humans. This is bad ozone. Hence, Ozone is metaphorically referred to as, “Good up high but bad down below”. The paper attempts to analyze the seasonal variation in concentration of ozone at the surface. The role of precursors that help in formation and destruction are studied. The study shows correlation of concentration of surface ozone with precursors. The statistical inferences show an irrefutable influence of meteorological parameters on the concentration of ozone.

Seasonal patterns of microplastics in surface sediments of a Mediterranean lagoon heavily impacted by human activities (Bizerte lagoon, Northern Tunisia)

In this paper, we investigated seasonal variations in concentrations of microplastics (MPs) in surface sediments of a lagoon heavily impacted by human activities, located in northern Tunisia (the Bizerte lagoon, southern Mediterranean Sea). Analyses of 112 sediment samples collected from 28 stations between May 2019 and February 2020 revealed significant seasonal variation in concentrations of total MPs, with the highest levels recorded in August 2019 (109.6 ± 59.8 items kg-1 DS (dry sediment)) and the lowest in February 2020 (33.2 ± 22.0 items kg-1 DS). In terms of polymer types, polyethylene particles were the most abundant throughout the year, followed by polypropylene, polyvinyl chloride, and polyethylene terephthalate. Spatial variations in total MP concentrations were found to depend on several environmental factors, including proximity to the coastline, level of anthropogenic pressure, location inside the lagoon, and presence/absence of vegetation. The upper 5-cm surface sediment layer of the lagoon was found to contain ~ 9.96 × 1010 MP particles, equal to ~ 248.97 t of plastic. Similar patterns of microplastic composition and structure were found throughout the year, revealing the same plastic pollution hotspots during all seasons. This indicates that sources of plastic pollution are land-based and originate from coastal urban, industrial, and agricultural areas, as well as from major freshwater streams. The findings of the present work can help to develop an efficient environmental management plan aiming to reduce and/or stop the spread of plastic pollution and its impacts on the socially and economically important ecosystem of the Bizerte lagoon.

Spatiotemporal variations of nitrogen and phosphorus deposition across China

Atmospheric deposition is an important pathway for the input of anthropogenic and natural nutrients to terrestrial and aquatic ecosystems. However, previous measurements focused mainly on hotspot locations, ignoring the fact that the deposition magnitudes of various nutrient species (e.g., nitrogen (N), phosphorus (P)) at a national scale should be investigated jointly. To better characterize national scale bulk deposition, precipitation samples were collected at 41 sites across China from September 2015 to August 2016 and September 2017 to August 2018. The bulk deposition fluxes of total nitrogen (TN) and total phosphorus (TP) over the network were 27.5 kg N ha−1 yr−1 and 0.92 kg P ha−1 yr−1, respectively. Contributions of NH4+, NO3−, and dissolved organic nitrogen (DON) to TN averaged 32%, 32%, and 36%, respectively. Significant spatial and seasonal variations in concentrations and deposition fluxes of all nutrient species were observed reflecting effects of local reactive nitrogen (Nr) and P emissions and rainfall amount. Major sources were energy resource consumption for NO3−, agricultural activities for NH4+, and a mixed contribution of both anthropogenic and natural sources for DON and TP. Atmospheric N and P deposition represent important external nutrient inputs to ecosystems and a high ratio of TN to TP (29.9) may induce relative P-limitation and further increase the risk of eutrophication. This work reveals a new map of atmospheric N and P deposition and identifies regions where emissions should be controlled to mitigate long-term impacts of atmospheric deposition over China.

Dominant species as biological indicators to predict the changes of trace element in different types of rangeland

Alpine meadow, typical steppe and desert are globally important rangeland ecosystems. However, the seasonal variations in concentrations of trace elements, which are important nutrients for grazing livestock, are unclear in these types of rangeland and it is difficult to prevent disorders in grazing livestock caused by trace element excesses and deficiencies. In order to identify which forage species might serve as indicators of the trace element status of livestock forage, we investigated the seasonal trends in Fe, Mn, Cu, and Zn concentrations in the plant communities and dominant species from diverse rangeland types in northwest China in relation to livestock sufficiency levels. The trace element concentrations in the plant communities changed significantly with the season, with the highest Cu, Mn and Zn concentrations and the lowest Fe and Mn concentrations detected in spring and summer, respectively. The seasonal mean temperature, seasonal precipitation, and above-ground biomass significantly negatively correlated with the seasonal variation of Fe and Mn concentrations in the plant community. However, there was almost no significant correlation between these factors and the seasonal Cu and Zn concentrations. The plant concentrations of Fe and Mn were much higher than the recommended levels for livestock in all rangeland types, but the concentrations of Cu in the alpine meadow and the Zn concentrations in all the rangelands barely met the nutritional requirements for animal growth. Based on these deficiencies, we suggest that some forage species could be used as biological indicators to predict changes in the concentrations of trace elements. A decrease in the relative biomass of Kobresia capillifolia and Kobresia humilis in alpine meadows implies a decrease in the levels of Cu in the plant community. A decrease in the relative biomass of K. humilis in alpine meadows, an increase in Stipa bungeana in typical steppes and an increase in Nitraria tangutorum and Salsola passertine in desert rangelands lead to decreased concentrations of Zn in the plant community.

Atmospheric concentrations of polychlorinated biphenyls, brominated flame retardants, and novel flame retardants in Lagos, Nigeria indicate substantial local sources.

Polychlorinated biphenyls (PCBs), brominated flame retardants (BFRs) like polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD), and novel flame retardants (NFRs) like decabromodiphenyl ethane (DBDPE) are ubiquitous environmental pollutants. Despite this, little is known about their concentrations in outdoor air in the African continent. To address this knowledge gap, concentrations of BFRs, NFRs, and PCBs were measured in outdoor air at 8 sites located within the metropolitan area of Lagos, Nigeria. Concentrations of ∑8BDEs, ∑HBCDD, ∑7NFRs and ∑8PCBs were: 21-750 (median=100) pg/m3, <12-180 (median =<12) pg/m3, 34-900 (median=300) pg/m3 and 85-460 (median=300) pg/m3, respectively. Decabromodiphenyl ether (BDE-209, range: <16-620pg/m3, median=71pg/m3) and DBDPE (range: <37-890pg/m3, median=280pg/m3) were the dominant BFRs detected, while the non-Arochlor PCB 11 (range: 49-220pg/m3, median=100pg/m3) was the dominant PCB. To the authors' knowledge, these are the first data on the non-Arochlor PCB 11 in outdoor air in Africa. In general, concentrations of all target contaminants in this study were within the range reported elsewhere in Africa and worldwide. Likely due to the tropical climate of Lagos, no seasonal variation in concentrations was discernible for any of the target contaminants. While concentrations of PBDEs and some NFRs were correlated with population density, concentrations of PCBs appear more impacted by leaks from electrical transformers and for PCB 11 to proximity to activities like textile factories that produce and use dyes.

Organic Matter Composition of Biomineral Flocs and Its Influence on Suspended Particulate Matter Dynamics Along a Nearshore to Offshore Transect

AbstractThe seasonal variation in concentration of transparent exopolymer particles (TEPs), particulate organic carbon (POC) and particulate organic nitrogen (PON) were investigated together with floc size and the concentration of suspended particulate matter (SPM) along the cross‐shore gradient, from the high turbid nearshore toward the low‐turbid offshore waters in the Southern Bight of the North Sea. Our data demonstrate that biophysical flocculation cannot be explained by these heterogeneous parameters, but requires a distinction between a more reactive labile (“fresh”) and a less reactive refractory (“mineral‐associated”) fraction. Based on all data, we separated the labile and mineral‐associated POC, PON, and TEP using a semi‐empirical model approach. The model's estimates of fresh and mineral‐associated organic matter (OM) show that great parts of the POC, PON, and TEP are associated with suspended minerals, which are present in the water column throughout the year, whereas the occurrence of fresh TEP, POC, and PON is restricted to spring and summer months. In spite of a constantly high abundance of total TEP throughout the entire year, it is its fresh fraction that promotes the formation of larger and faster sinking biomineral flocs, thereby contributing to reducing the SPM concentration in the water column over spring and summer. Our results show that the different components of the SPM, such as minerals, extracellular OM and living organisms, form an integrated dynamic system with direct interactions and feedback controls.

Seasonal variation of concentration and net CO2 exchange in the spruce forest ecosystem of the middle taiga

Seasonal variation of concentration and net CO2 exchange in the spruce forest ecosystem of the middle taiga

SEASONAL VARIATION IN TRACE METAL CONCENTRATIONS IN SOIL AND VEGETABLE SAMPLES FROM SELECTED MINING AREAS IN JOS SOUTH AND BARKIN LADI LGA, PLATEAU STATE

In this study, the seasonal variation in concentrations of the trace metals Cu, Zn, Pb, Cd, As Ni and Co in soil and vegetable samples from farms in some mining areas in Jos South and Barkin Ladi LGA, Plateau State were investigated in two major seasons (dry and wet). This was done to assess the pollution status of the farms and hence, the safety levels of the vegetable samples. The samples were treated and digested using 10 cm3 HNO3 and 30 cm3 HCl in the ratio of 1:3. Trace metal concentrations were determined using the PG-990 model atomic absorption spectrophotometer. Analytical results of soil samples from mining areas indicated higher concentration of Cu and As for both seasons than the values reported by the FAO/WHO (2007). Similarly, the metals Cu (15.12±1.50 mg/kg), Zn (76.45±2.40 mg/kg), Pb (23.75±1.35 mg/kg), Cd (3.69±0.15 mg/kg), Ni (17.80 ±0.15 mg/kg) and Co (28.14+1.35 mg/kg) showed high concentrations in dry season than wet season. Comparing the vegetable samples, spinach was found to accumulate high concentration of trace metals than tomato and Irish potato. In general, the levels of trace metals in soil and vegetable samples were higher in dry season than in wet season. The levels of Pb, Cd, As, Ni and Co were significantly above the critical toxic level in vegetables as reported by WHO/FAO (2007), while Zn and Cu occurred within the acceptable limit for both seasons.