Upstream Sampling Site Research Articles

Isotopic insights and integrated analysis for heavy metal levels, ecological risks, and source apportionment in river sediments of the Qinghai-Tibet Plateau

The research was carried out to examine the pollution characteristics, ecological risk, and origins of seven heavy metals (Hg, As, Pb, Cu, Cd, Zn, and Ni) in 51 sediment samples gathered from 8 rivers located on the Qinghai-Tibet Plateau (QTP) in China. The contents of Hg and Cd were 5.0 and 1.1 times higher than their background values, respectively. The mean levels of other measured heavy metals were below those found naturally in the local soil. The enrichment factor showed that the study area exhibited significantly enriched Hg with 70.6% sampling sites. The Cd contents at 19.6% of sampling sites were moderately enriched. The other sampling sites were at a less enriched level. The sediments of all the rivers had a medium level of potential ecological risk. Hg was the major ecological risk factor in all sampling sites, followed by Cd. The findings from the positive matrix factorization (PMF) analysis shown agricultural activities, industrial activities, traffic emissions, and parent material were the major sources. The upper, middle, and low reaches of the Quanji river had different Hg isotope compositions, while sediments near the middle reaches were similar to the δ202Hg of the industrial source. At the upstream sampling sites, the Hg isotope content was very close to the background level. The results of this research can establish a strong scientific sound to improve the safety of the natural circumstances of rivers on the QTP.

Elucidating potential bioindicators from insights in the diversity and assembly processes of prokaryotic and eukaryotic communities in the Mekong River

Drivers for spatio-temporal distribution patterns of overall planktonic prokaryotes and eukaryotes in riverine ecosystems are generally not fully understood. This study employed amplicon metabarcoding to investigate the distributions and assembly mechanisms of bacterial and eukaryotic communities in the Mekong River. The prevailing bacteria taxa were found to be Betaproteobacteria, Actinobacteria, and Bacteroidetes, while the dominant eukaryotic organisms were cryptophytes, chlorophytes, and diatoms. The community assemblages were influenced by a combination of stochastic and deterministic processes. Drift (DR) and dispersal limitation (DL), signifying the stochastic mechanism, were the main processes shaping the overall prokaryotic and eukaryotic communities. However, homogeneous selection (HoS), indicating deterministic mechanism, played a major role in the assembly process of core prokaryotic communities, especially in the wet season. In contrast, the core eukaryotic communities including Opisthokonta, Sar, and Chlorophyta were dominated by stochastic processes. The significance of HoS within prokaryotic communities was also found to exhibit a decreasing trend from the upstream sampling sites (Chiang Saen and Chiang Khan, Nong Khai) towards the downstream sites (Mukdahan, and Khong Chiam) of the Mekong River. The environmental gradients resulting from the site-specific variations and the gradual decrease in elevation along the river may have a potential influence on the role of HoS in community assembly. Crucial environmental factors that shape the phylogenetic structure within distinct bins of the core prokaryotic communities including water depth, temperature, chloride, sodium, and sulphate were identified, as inferred by their correlation with the beta Net Relatedness Index (betaNRI) during the wet season. Overall, these findings enhance understanding of the complex mechanisms governing the spatio-temporal dynamics of prokaryotic and eukaryotic communities in the Mekong River. Finally, insights gained from this study could provide information on further use of specific core bacteria as microbial-based bioindicators that are effective for the assessment and conservation of the Mekong River ecosystem.

Geochemical characterization, its controlling factors, and comparison between the upstream and downstream segments of the Himalayan Satluj River basin, India

Satluj River Basin (SRB) has special economic significance, representing the country's most incredible hydro-structure with fresh water, a primary source of irrigation and hydroelectric power in Northern India. Therefore, SRB's geochemical characterization is vital for hydropower and agricultural sustainability. This study provides a preliminary characterization of the hydrogeochemical processes controlling the natural water evolution in SRB by observing the spatial variation and qualitative assessment of solute chemistry (major ions and trace/heavy elements) in the Satluj river, associated tributaries, and groundwater. Hydrochemical characteristics displayed the predominance of geogenic weathering processes with carbonates dissolution and silicate weathering as end members that could explain all the geochemical variability within the SRB. The results reveal that the chemical signature of the upstream segment is possibly influenced more by carbonate weathering than silicate weathering, and the trends reverse in the downstream section with the increasing influence of silicate weathering. Dissolved heavy metals (HMs) such as Mn, Cr, Fe, Co, Ni, Cu, Zn, As, Cd, and Pb showed large fluctuations among upstream and downstream sampling sites, indicating diverse environmental conditions. Human health risk assessment (HHRA) studies revealed less or no potential noncarcinogenic via HMs, except for the downstream stretch of tributaries inferring increased non-cancerous risk. Moreover, the HHRA with HMs (Cr, As, Cd, and Pb) manifested high carcinogenic risks for adults and children across the SRB. The finding of this study could be the baseline dataset for assessing the future status, effective management, and better utilization of water resources of the SRB.

Nitrogen and phosphorusas major factors shaping microbial community structures in surface sediments in Xiangxi River, Three Gorges Reservoir

香溪河是三峡库区最大的入库支流,目前关于香溪河沉积物微生物群落结构特征及其主要影响因素尚不明确。本研究监测香溪河上、中、下游上覆水及沉积物的主要理化指标,通过16S rDNA高通量测序研究香溪河表层沉积物中微生物群落结构特征,使用统计学软件分析细菌与理化指标间的关系。结果表明,上覆水中氨氮(NH₃-N)、叶绿素a(Chl.a)浓度自下游向上游逐渐升高,其中NH₃-N浓度从下游的2.04 mg/L升高到上游的3.14 mg/L。不同点位上覆水中磷酸盐(PO^3-₄)浓度在0.14~0.18 mg/L之间波动;同一点位间隙水中NH₃-N、PO^3-₄浓度明显高于上覆水,10~15 cm沉积物间隙水中NH₃-N与PO^3-₄浓度分别是0~5 cm沉积物间隙水的3.4倍和1.7倍。沉积物中Fe(Ⅱ)、Fe(Ⅲ)、酸可挥发性硫化物和铬还原性硫化物含量均表现为上游点位高于中游、下游,底层沉积物含量高于中层和表层。香溪河中游沉积物的微生物多样性和丰富度高于下游和上游,其中变形菌门(Proteobacteria)是表层沉积物中的优势菌门,鞘脂单胞菌属(Sphingomonas)为主要菌属。不同代谢功能的微生物在空间分布上存在差异,比如具有降解多环芳烃能力的外新鞘脂菌属(Novosphingobium)和土生单胞菌属(Terrimonas)在下游点位的相对丰度最高,分别达到5.8%和5.4%,硝化螺旋菌属(Nitrospira)和黄杆菌属(Flavobacterium)在中游的相对丰度最高,而铁氧化菌水杆菌属(Aquabacterium)主要分布在上游点位。冗余分析(RDA)表明总有机碳、硫酸根、Fe(Ⅱ)、氨氮和总磷是影响香溪河沉积物中微生物群落结构的主要环境因子。本研究有助于进一步了解周边环境和人为活动对香溪河水质稳定及沉积物中微生物的影响,为三峡库区水环境改善和管理提供参考。;Xiangxi River is the largest inflow tributary in the Three Gorges Reservoir area. Structural characteristics and influence factors of the microbial communities in sediments of Xiangxi River are not clear so far. This study investigated the main physical and chemical parameters of the overlying water (i.e., surface, middle and bottom layers) and sediments of the Xiangxi River. 16S rDNA high-throughput sequencing was used to reveal the characteristics of microbial community structures in the sediments. In addition, the relationship between bacteria and physicochemical parameters were analyzed statistically. Chlorophyll.a (Chl.a), concentrations of ammonia nitrogen (NH₃-N) in the overlying water increased gradually from the downstream (2.04 mg/L) to the upstream (3.14 mg/L). The concentrations of phosphate (PO^3-₄) in overlying water fluctuated between 0.14 and 0.18 mg/L at different sampling sites. In addition, the concentrations of NH₃-N and PO^3-₄ in the pore-water at the same site were significantly higher than those in the overlying water. Pore-water NH₃-N and PO^3-₄ concentrations at 10-15 cm depth were 3.4 and 1.7 times higher than those at 0-5 cm depth in sediments, respectively. Higher contents of Fe (Ⅱ), Fe (Ⅲ), acid volatile sulfide and chromium reducing sulfide were observed in the upstream sampling sites and bottom layers of the sediments. The microbial diversity and richness in the sediments of midstream were higher compared to the sediments of downstream and upstream. Proteobacteria was the dominant phylum in the surface sediments, and Sphingomonas was the main genus. The spatial distributions of microorganisms for different metabolic activities varied. Typical bacteria with the ability to degrade polycyclic aromatic hydrocarbons, such as Novosphingobium and Terrimonas, were mainly observed in the sediments of downstream sites with percentage reaching 5.8% and 5.4%, respectively. The percentages of Nitrospira and Flavobacterium were highest in the midstream. The iron-oxidizing bacteria (i.e., Aquabacterium) were rich in the upstream sites. Redundancy analysis (RDA) showed that total organic carbon (TOC), sulfate (SO^2-₄), Fe (Ⅱ), NH₃-N and total phosphorus (TP) were the main environmental factors shaping the microbial community structures in sediments of Xiangxi River. This study will help to further understand the impacts of surrounding environment and human activities on the stability of water quality and the microorganisms in the sediments of Xiangxi River, and provide a reference for the improvement and management of the water environment in the Three Gorges Reservoir area.

Assessment of Surface Water Quality of Huai Luang River in Udon Thani, Thailand, Using the Water Quality Index

This study aimed to analyze the surface water quality of the Huai Luang River using the water quality index (WQI) method. Five parameters were analyzed to assess the water quality of the Huai Luang River; they were dissolved oxygen (DO), biochemical oxygen demand (BOD), total coliform bacteria (TCB), fecal coliform bacteria (FCB), and ammonia (NH3). The Huai Luang River is the municipality’s primary consumption water source in Udon Thani province, Thailand. WQI classifications were calculated by using the surface water quality standards program of Thailand’s Pollution Control Department (PCD-WQI). The results showed that the water quality in the Huai Luang River was bad status, in the WQI range of 54-60 scores. The major sources of pollutants in the Huai Luang River were wastewater from communities, agriculture, and animal farms are the main contributors to water pollution. Seasonal water quality variations were observed at each monitoring site from March 2022 to February 2023. WQI concentration in the rainy season (March to June) was generally among the highest (57 score) compared with other seasons (56 score in winter and 54 score in summer). While the WQI concentration of the upstream sampling site (domestic wastewater) had the lowest (55 score) compared with the other sites (59 score for midstream and 60 score for downstream). Therefore, this research study presented valuable information on WQI for the Huai Luang River for water quality management by administrators and local community participation.

In a Degraded Stream, Increased Salt Concentration is Correlated with Decreased EPT Diversity

Many streams in the Northern Panhandle of West Virginia are biologically impaired due to historical and concurrent anthropogenic activities, including mining, agriculture, and urbanization. These activities alter water chemistry which affects the benthic macroinvertebrate communities. While taxa like Ephemeroptera, Plecoptera, and Trichoptera (EPT taxa) are sensitive to water pollution, other taxa like tipulids, beetles, and chironomid midges are more pollution tolerant. However, responses to specific chemical pollutants are taxa specific and even some EPT are relatively pollution tolerant. We investigated how increases in chloride (Cl) and specific conductance (SPC) affected the macroinvertebrate community in a stream already heavily impacted by mining, urbanization and agriculture. Five upstream sampling sites were placed in a degraded stream above the outfall of an active coal mine, while five additional sites were placed downstream of the discharge. Water chemistry was measured in each site, and macroinvertebrates were collected with kick nets, leaf packs and a visual collection of unique habitats following the Stream Monitoring Information Exchange (SMIE) protocol. We found that temperature, SPC, and Cl were significantly higher downstream of the mine outfall with SPC and Cl more than doubling. SMIE water quality scores and whole community Shannon-Wiener Diversity Index scores were not significantly different between upstream and downstream sites but EPT diversity was significantly higher upstream of the mine. This data helps determine taxa specific responses to changes in water chemistry, specifically SPC and Cl, and highlights how streams already afflicted with poor water quality can lose additional taxa when the concentrations of salts increases.

Unravelling the spatiotemporal variation of pCO2 in low order streams: Linkages to land use and stream order

Headwater streams make the majority of cumulative stream length in a river basin, carbon dioxide (CO2) emission from headwater (low order) streams is thus an essential component. Anthropogenic activities in headwater areas such as land use change and land use practices can strongly modify terrestrial carbon and nutrient input, which could affect the level of partial pressure of dissolved carbon dioxide (pCO2) and CO2 degassing from streams. However, there are large uncertainties in estimates due to the lack of data in subtropical rivers of rapidly developing rural regions. The spatiotemporal variation and driving factors of the pCO2 and CO2 degassing from low-order streams remain to be explored. In this study, we assess multi-spatial scale effects of land use on pCO2 dynamics in seven headwater tributary rivers in Central China during 2016, 2017 and 2018 in rainy and dry seasons. Our results reveal that the stream pCO2 level consistently increases as the stream order increases from 1 to 3 under apparent seasonal variations. Riverine pCO2 is positively related to the percentage of urban land and cropland surrounding the river segments, but is negatively related to the percentage of forest land. The stream pCO2 is more closely correlated with the 1000 and 2000 m diameters of circular buffers at upstream sampling sites than the circular buffers with 100 and 500 m diameters. There exist significant relationships of pCO2 with the concentrations of TN, TP, DO, and DOC in the low-order streams. The partial redundancy analysis quantifies the relative importance of anthropogenic land uses, natural factors and water chemical variables in mediating stream pCO2, showing that influences of anthropogenic land uses (urban and cropland) on pCO2 decrease, with a percentage role of 34%, 14%, and 4% in the 1st-, 2nd- and 3rd-order streams, respectively. The impact of nutrients on pCO2, however, increases as the stream order increases. Urban influence on stream pCO2 also decreases as stream order increases. Our study highlights the effect of land use/land cover types and stream order on riverine pCO2 and provides new insight into estimating CO2 emission in headwater streams. Future studies are needed on the linkage between riverine CO2 degassing and stream orders under changing land use conditions.

Heavy metal toxicity, ecological risk assessment, and pollution sources in a hydropower reservoir.

Heavy metal (HM) toxicity, ecological risk, and pollution sources were analyzed using the pollution indexing and statistical methods in the Three Gorges Reservoir (TGR). The average concentration of HM increased in the order of Cr < Ni < As < Cd < Cu < Mn < Pb < Zn < Al < Fe during the recharge period and Cd < Cr < Ni < As < Cu < Pb < Mn < Zn < Al < Fe during the discharge period. Significant spatial variations of Pb, Zn, Cd, As, Mn, Ni, Cr, and Cu were observed at the upstream and downstream sampling sites. Pb sharply increased during the recharge period, ranges (6.93-148.62μg/L) and exceeded WHO and USPEA standards limit. HPI, HEI, Cd, WPI indicated low pollution and moderate pollution with the strong influence of Pb and Cd in the discharge and recharging period, respectively. HTML values are below the permissible toxicity load except for Pb. The Pb toxicity removal percentage is 56.47%, suggesting that the lead's toxicity level is high in TGR and requires the removal process. Ecological risk index values indicated that pollution is low in TGR. The potential ecological risk indexes (RI) of 9.07 and 31.60 were obtained for the discharge and recharge period, respectively, indicating low potential ecological risk from heavy metals in TGR. However, RI values revealed that (Pb, Cd, As Cr Ni, Cu Zn, and Mn) were the most ecological risk HMs in TGR. A significant ecological risk of Pb and Cd distribution was observed across the TGR. Multivariate statistical results found that Pb, Cd, Zn, Mn, Ni, As, Cr, Cu mainly originate from industrial wastewater, mining, metals processing, and agricultural runoff. Fe and Al were mainly from bedrock weathering. Pb, Cd, Zn HMs are a threat to the reservoir ecosystem. This study delivered a current status of HM pollution, toxicity, ecological risk, and pollution sources, indicating a vital insight into HM pollution and water security management inthe Three Gorges Reservoir.

Centric diatom diversity in the lower part of the Southern Bug river (Ukraine): the transitional zone at Mykolaiv city.

The diversity of centric diatoms is documented for the transitional zone of the lower part of the Southern Bug River (Ukraine) just before entering the Dnipro-Bug Estuary and compared to earlier results from the upstream sampling sites of the same river system. Benthic samples of the following sites were investigated: north of Mykolaiv City (approximately 5 km), in Mykolaiv City (near Varvarivskyi Bridge), and 5 km south of the city. Twenty-four centric diatom taxa belonging to 11 genera were identified, analysed, and documented by scanning electron microscopy (SEM) and light microscopy (LM). Among them, Aulacoseira nivalis is the first report for Ukraine, A. islandica and is the first confirmed record for the studied area since the 1930s. The maximum number of centric diatom taxa found in one station was 21, the minimum 10. Melosira subglobosa was the most common (documented in 57–80% of sites with centric diatoms) and abundant species 7.3–15.7% in relative abundance to all diatom taxa. The discovered diversity of taxa and its comparison with previous results is discussed with regard to the relevance of estuary zones in the research of diatoms.

Analyzing Particle-Associated Pollutant Transport to Identify In-Stream Sediment Processes during a High Flow Event

Urban areas are a leading source of polycyclic aromatic hydrocarbons (PAHs) that result from combustion processes and are emitted into rivers, especially during rain events and with particle wash-off from urban surfaces. In-stream transport of suspended particles and attached PAHs is linked strongly to sediment turnover processes. This study aimed to identify particle exchange processes that contribute to the transport of suspended particles during flood events. An urban high-flow signal was tracked in high temporal resolution at two sampling sites in the Ammer River (South-western Germany). Samples were analyzed for turbidity, total suspended solids concentrations (TSS), particle-size distribution, organic carbon, and PAH. Maximum discharge and the highest TSS occurred nearly simultaneously at the upstream sampling site, whereas a temporally shifted course was observed for downstream. The total load of particles was similar, yet a decrease of PAH mass (~28%) and an increase of the particulate organic carbon (POC) content (~3.5%-points) occurred. Coarser particles (≥26 µm) dominated at the beginning of the event at both sampling sites. The signal of remobilized riverbed sediment increases downstream and leads to well-established, robust linear correlations between TSS and PAHs. This study highlights that riverbed sediment acts as intermediate storage for contaminated particles from upstream sources that shape, together with the fresh urban input, the “particle signature” of suspensions moving through catchments during high discharge conditions.

&lt;p class="HeadingRunIn"&gt;&lt;strong&gt;Monthly Diversity and Abundance of Caddisflies in Upstream and Downstream Areas of the Mae Ngat Somboonchol Dam, Chiang Mai Province, Thailand&lt;/strong&gt;&lt;/p&gt;

The Mae Ngat Somboonchol Dam, located in Chiang Mai Province of northern Thailand, was constructed to serve the purposes of irrigation and electricity generation for the region. This hydroelectric dam is located on the Mae Ngat River, which is a tributary of the Ping River. The aim of this experiment was to study the diversity and abundance of the population of caddisflies in this river. Seven sampling sites, including 2 upstream and 5 downstream sites, were monitored monthly for adult male caddisflies using a light pan trap device over 1 year (June 2013 – May 2014). A total of 3,844 male specimens belonging to 16 families and 94 species were caught. However, the total abundance of caddisflies was higher at the upstream sampling sites than at the downstream sampling sites. The top three most abundant species found to be present in this river were Oecetis scutulata MARTYNOV, 1936, Setodes argentiguttatus GORDON &amp; SCHMID, 1987 and Cheumatopsyche globosa ULMER, 1910, respectively. The species compositions of the upstream and downstream sites differed. 44 specimens of the species Trichoptera were represented exclusively at the upstream sites. Examples of this include Macrostemum fenestratum ALBARDA, 1887, Setodes endymion MALICKY &amp; CHANTARAMONGKOL, 2000, Hydropsyche camillus MALICKY &amp; CHANTARAMONGKOL, 2000 and Ecnomus jojachin MALICKY &amp; CHANTARAMONGKOL, 1993. The 23 species exclusively represented in the downstream sites included Aethaloptera sexpunctata KOLENATI, 1859, Cheumatopsyche banksi MOSELY, 1942, Oecetis tripunctata FABRICIUS, 1793 and Ecnomus votticius MALICKY &amp; CHANTARAMONGKOL, 1993. There were 50 newly recorded species while 18 species were absent when compared to a previous study from 2009. The diversity and abundance also differed during each month of collection. The highest numbers of trapped male caddisflies were found from April to May, which were 352 and 292, respectively. The upstream sites contained a higher number of caddisflies and a greater level of diversity than the downstream sites.

Spatial and Temporal Variability in the Development and Potential Toxicity of Phormidium Biofilms in the Tarn River, France.

Proliferation of Phormidium biofilms in rivers is becoming a worldwide sanitation problem for humans and animals, due to the ability of these bacteria to produce anatoxins. To better understand the environmental conditions that favor the development of Phormidium biofilms and the production of anatoxins, we monitored the formation of these biofilms and their toxins for two years in the Tarn River, biofilms from which are known to have caused the deaths of multiple dogs. As previously observed in New Zealand, Phormidium biofilm development occurred in riffle areas. The coverage of these biofilms at the bottom of the river exhibited strong spatial and temporal variations, but was positively correlated with water temperature and depth. Anatoxin-a was detected in less than 50% of the biofilms. The concentrations of these toxins in the biofilms exhibited high spatiotemporal variability, with the highest concentrations being recorded at the end of the summer period at the upstream sampling sites. These findings suggest that the maturity of the biofilms, combined with the local environmental conditions, have an impact on the production of anatoxin, making risk assessment for these benthic proliferations challenging.

Sediment Fingerprinting to Delineate Sources of Sediment in the Agricultural and Forested Smith Creek Watershed, Virginia, USA

AbstractThe sediment fingerprinting approach was used to apportion fine‐grained sediment to cropland, pasture, forests, and streambanks in the agricultural and forested Smith Creek, watershed, Virginia. Smith Creek is a showcase study area in the Chesapeake Bay watershed, where management actions to reduce nutrients and sediment are being monitored. Analyses of suspended sediment at the downstream and upstream sampling sites indicated streambanks were the major source of sediment (76% downstream and 70% upstream). Current management strategies proposed to reduce sediment loadings for Smith Creek do not target streambanks as a source of sediment, whereas the results of this study indicate that management strategies to reduce sediment loads in Smith Creek may be effective if directed toward managing streambank erosion. The results of this study also highlight the utility of sediment fingerprinting as a management tool to identify sediment sources.

Ecosystem-Based Management strategies to improve aquaculture in developing countries: Case study of Marismas Nacionales

The Ecosystem Based Management approach is an opportunity to maximize ecosystem services while promoting ecological resilience and appropriate productive activities. However, implementing this management strategy relies on acknowledging spatial interactions between economic activities and ecosystem services as well as an effective communication between scientists and decision-makers. The lack in understanding those interactions and management decisions based on limited information has led to an unsuccessful transition between artisanal and intensive aquaculture in a Wetland of International Importance (NW Mexican Pacific). In this study, we evaluated the effect of aquaculture as a driver of wetland degradation and water quality and analysed the perceptions of decision makers and scientists concerning the spatial scale of aquaculture impacts on ecosystem services.From 1997–2013, we found that herbaceous wetland and croplands have been lost while grasslands, urban areas, aquaculture and mangroves have increased. Shrimp ponds were built on natural water bodies, herbaceous wetlands and croplands. However, perturbed mangrove patches are found near aquaculture ponds, mostly downstream. Water samples were analysed and differences were found between upstream and downstream sampling sites in the concentration of DO, COD, TS, salinity, SO42-, Cl-1, CaCO3, Na, Cr, Ni and Al. Sediment analysis showed that the amount of coarse sediment such as sand and gravel diminished significantly upstream and does not reach the river mouth. Finally, perceived spatial relationship analyses showed that most academics surveyed recognized that aquaculture could have a far-reaching impact outside the immediate production area. On the other hand, more than half of the decision makers who responded did not perceive any impact and the majority of the rest considered that the impact occurred close to the ponds. The likelihood of integrated coastal management strategies being implemented depends on the close collaboration of scientists and decision makers, on their understanding of complex spatial interactions, on developing appropriate management alternatives and on incorporating science in spatial planning and decision making.

Origin of placer gold and other heavy minerals from fluvial Cenozoic sediments in close proximity to Rote Fäule-related Au mineralisation in the North Sudetic Trough, SW Poland

Detailed morphological and geochemical studies of placer gold grains and other heavy minerals from Cenozoic fluvial clastic sediments in the area of the Zimnik Creek drainage basin (North Sudetic Trough, Lower Silesia) allowed the description of their specific features: shape and morphology, flatness index, internal textural features and chemical composition of the gold grains. It enables an estimation of the distance from the source area and determination of the source of the ore mineralisation, along with establishing the feeder areas for placer mineralisation including Rote Faule-related gold hosted by Rotliegend-Zechstein transitional sediments. The comparison of the heavy mineral contents of placer grains from the Zimnik Creek drainage basin makes it possible to identify the area of origin for the gold particles. The crystalline Au-Ag-Pd-Hg (polymetallic) alloy grains of fluvial gold are assumed to come from the transitional sediments between the Rotliegend and the Zechstein in the North Sudetic Basin. The morphological and geochemical features of the polymetallic grains strongly suggest that the grains from the upper course of the Zimnik Creek valley sediments represent what has eroded from the local gold mineralisation and this mineralisation is probably in the vicinity of the upstream sampling site. The bimodal chemical composition of the Au-Ag-Pd-Hg alloy grains with electrum and medium-Ag grains (<15 wt.% Ag) found in the study area is typical of the Rote Faule and Kupferschiefer-related gold mineralisation on the southern side of the North Sudetic Trough and the Sieroszowice-Polkowice copper mining district of the Fore-Sudetic Monocline. The study of the Ag contents of placer grains from the Zimnik Creek drainage basin highlights the contrast between the placer gold grains derived from Paleozoic orogenic gold mineralisation in the Sudetes (typically simple Au-Ag alloys containing between 5 and 20 wt.% of Ag) and the one formed by the oxidizing chloride hydrothermal systems. The grains identified in this manner as originating from the oxidizing hydrothermal system of the transitional zone can be distinguished from the placer gold derived from other styles of mineralisation, which are not Rote Faule-related. It is particularly important considering the ongoing reconnaissance exploration in the North Sudetic Trough (SW Poland), which employs gold grain analyses as a prospecting tool for the detection of potentially economic primary gold mineralisation.

Eutrophication status of the Daning River within the Three Gorges Reservoir and its controlling factors before and after experimental impoundment

We evaluated 4-year-old data set to assess the trophic state and the controlling factors of the TGR during different experimental impounding (January 2005 to December 2005, stage I–stage II; January 2007 to December 2007, stage II–stage III; January 2009 to December 2009, stage III–stage IV) and normal operating (January 2011 to December 2011, stage IV) periods. The trophic state indices (TSITP) increased in the study area after TGR impoundment, and the TSISD and TSICHL did not significantly change after TGR impoundment; the values of TSICHL only increased at S1 (upstream sampling sites) after the TGR impoundment. The TSISD values in the Daning River (S1, S2, and S3) and the main stream of the TGR (S4) showed similar seasonal variations, with the highest values observed in the flood seasons, followed by the normal seasons and the dry seasons in descending order. The TSICHL only values varied substantially among the three seasons in the backwater area of the Daning River (S2), with the highest value occurring in the flood seasons, followed by dry seasons and normal seasons. The differences in the trophic state indices became smaller between the three seasons after TGR impoundment. The values of TSITP and TSISD showed similar spatial variances, with the highest value observed at S4, followed by S3, S2, and S1 in descending order. The TSICHL values were higher at S2 than at S3, S1, and S4. The results showed that the phosphorus and nonalgal turbidity limit trophic status of the mainstream of TGR and Daning River before and after experimental impoundment.

Impact on Water Quality of Nandoni Water Reservoir Downstream of Municipal Sewage Plants in Vhembe District, South Africa

The deterioration of water quality in our freshwater sources is on the increase worldwide and, in South Africa, mostly due to the discharge of municipal sewage effluent. Here we report on the use of principal component analysis, coupled with factor and cluster analysis, to study the similarities and differences between upstream and downstream sampling sites that are downstream of municipal sewage plants. The contribution of climatic variables, air temperature, humidity, and rainfall were also evaluated with respect to variations in water quality at the sampling sites. The physicochemical and microbial values were higher than the Department of Water Affairs and Forestry (DWAF) and World Health Organization (WHO) guidelines. The cluster analysis showed the presence of two clusters for each of the Mvudi, Dzindi, and Luvuvhu Rivers and Nandoni reservoir sampling sites. The principal component analysis (PCA) accounted for 40% of the water quality variation and was associated strongly with pH, electrical conductivity, calcium, magnesium, chloride, bromide, nitrate, and total coliform, and negatively with rainfall, which represented Mvudi downstream and was attributed to the Thohoyandou sewage plant. The PCA accounted for 54% of the variation and was associated strongly with electrical conductivity, sulfate; total dissolved solids, fluoride, turbidity, nitrate, manganese, alkalinity, magnesium, and total coliform represented Dzindi downstream, with inflows from the Vuwani sewage plant and agriculture. The PCA accounted for 30% of the variation and was associated strongly with total dissolved solids, electrical conductivity, magnesium, fluoride, nitrate, sulfate, total coliform average air temperature, and total rainfall, and negatively associated with manganese and bromide represented Luvuvhu upstream and was associated with commercial agriculture. The PCA accounted for 21% of the variation and was associated strongly with turbidity, alkalinity, magnesium, chloride, fluoride, nitrate, and strongly negatively associated with rainfall, which represented Luvuvhu downstream, associated with inflows from Vuwani oxidation ponds, Elim and Waterval sewage plants, and agriculture. The PCA accounted for 14% of the variation and was moderately associated with rainfall and weakly associated with chloride and bromide and negatively associated with nitrate, which represented the natural Nandoni reservoir system. The continued discharge of effluent may render the raw water supply unsuitable for human consumption and lead to eutrophication due to nitrate enrichment and proliferation of harmful algal blooms and schistomiasis infections in the long term.

Biophysical Survey of the Hinatuan Enchanted River Underwater Cave System (HERUCS) and its Connecting River, Surigao del Sur, Southern Philippines

A rapid survey inside the Hinatuan Enchanted River Underwater Cave System (HERUCS) and its connecting river was done to gather baseline data on the biophysical aspects of the cave and river ecosystem. It involved collection of water samples, sediments and macrofauna. Water samples were analyzed for the following parameters, namely: nitrates, phosphates, turbidity, BOD, pH, alkalinity, conductivity and total coliform. Sediment samples were analyzed for total organic matter and grain size. A listing of macrofauna found within the length of the established sampling station was also collected, photo-documented and identified. Water from inside the cave have a pH range of 7.35– 7.39, a BOD of 1.67– 4.00 mg/L, a 16 ppt salinity (at cave entrance), and, nitrate and phosphate values of 0.32 –0.44 mg/L and 0.10–0.52 mg/L, respectively. The mean total coliform count of the water sample from the upstream sampling site was 1,700 MPN/100ml. There were 5 organisms belonging to 4 families recorded from inside the cave while 43 organisms belonging to 9 families were collected from its connecting river. Majority of the macrofauna samples collected were marine to brackish-water species and can be considered accidentals. Although there were no stygobites caught, the possibility of finding new species is high considering the depth of the cave and its many unexplored chambers. Further explorations are highly recommended with the use of mixed gas (i.e., Nitrox) for longer bottom time and more thorough sampling.

Floodplain influence on carbon speciation and fluxes from the lower Pearl River, Mississippi

To investigate the floodplain influence on carbon speciation and export to the northern Gulf of Mexico, water samples were collected monthly from two sites in the East Pearl River (EPR) basin during 2006–2008. Additionally, four spatial surveys in the river basin between those two sites were also conducted. Compared with the upstream sampling site at Bogalusa, MS, dissolved inorganic carbon (DIC) and particulate organic carbon (POC) concentrations were 36% and 55% lower, respectively, and dissolved organic carbon (DOC) concentration was 49% higher at the downstream Stennis Space Center (SSC) site. In addition, the bulk DOC pool at SSC had a higher colloidal fraction than at Bogalusa (75% vs. 68%). Detailed spatial surveys revealed the differences between the upstream and downstream stations resulted both from input from Hobolochitto Creek, a tributary of the EPR, and from influence of the swamp-rich floodplain. The contributions from Hobolochitto Creek to the carbon pool in the EPR basin were lowest during a high flow event and reached a maximum during the dry season. Meanwhile, the floodplain in the EPR basin acted as a significant sink for DOC, POC and particulate nitrogen during summer and for suspended sediment during a high flow event. However, the floodplain was converted into a source of suspended sediment, DOC, and POC to the EPR during winter, revealing a dynamic nature and seasonality in the floodplain influence. Consistent with its dominant forest coverage, abundant wetlands along the river corridor, and mild anthropogenic disturbance, the Pearl River basin above Bogalusa generally had higher yields of DOC and POC (1903 and 1386kg-Ckm−2yr−1, respectively), but a lower yield of DIC (2126kg-Ckm−2yr−1) compared to other North American rivers. An estimation based on a mass balance approach suggests the interactions between floodplain and the main river stem could reduce the annual DIC and POC export fluxes from downstream of the EPR by 24% and 40%, respectively, but enhance the annual riverine DOC export by 25%. Similar scenarios likely occur in other wetland-rich coastal rivers and are capable of significantly altering the current estimation of riverine carbon export.

Barrage fishponds: Reduction of pesticide concentration peaks and associated risk of adverse ecological effects in headwater streams

Constructed wetlands have been suggested as pesticide risk mitigation measures. Yet, in many agricultural areas, ponds or shallow lakes are already present and may contribute to the control of non-point source contamination by pesticides. In order to test this hypothesis, we investigated the influence of extensively managed barrage fishponds (n = 3) on the dissolved concentrations of 100 pesticides in headwater streams over the course of a year. Among the 100 pesticides, 50 different substances were detected upstream and 48 downstream. Highest measured concentration upstream was 26.5 μg/L (2-methyl-4-chlorophenoxyacetic acid, MCPA) and 5.19 μg/L (isoproturon) downstream. Fishponds were found to reduce peak exposure levels as high pesticide concentrations (defined here as ≥ 1 μg/L) generally decreased by more than 90% between upstream and downstream sampling sites. The measured concentrations in the investigated streams were compared to laboratory toxicity data for standard test organisms (algae, invertebrates and fish) using the toxic unit approach. When considering the threshold levels set by the European Union within the first tier risk assessment procedure for pesticide registration (commission regulation (EU) N° 546/2011), regulatory threshold exceedances were observed for 22 pesticides upstream from fishponds and for 9 pesticides downstream. Therefore, the investigated barrage fishponds contributed to the reduction of pesticide peak concentrations and potential risk of adverse effects for downstream ecosystems.