Elements In River Waters Research Articles

Occurrence, transport and sources of metals and metalloids in the Bangpakong River in the eastern economic corridor area of Thailand

The occurrence of elements in river water is affected by various factors, including mobility, weathering and transport processes and anthropogenic contributions. A total of six water sampling campaigns were conducted from 2021 to 2022 to study the factors affecting the occurrence of twelve elements (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn and Se) in the Bangpakong River. The total concentrations of all the elements were within the levels set by the national surface water quality standard. Comparisons of dissolved elemental concentrations in the study area with the global average for dissolved elemental concentrations in pristine rivers indicated contamination with Al, As, Co, Mn, Zn and Se in the river water. Based on the percentage of each element in particulates to the total concentration, Al (80.6 %), Cr (71.9 %), Cu (69.9 %), Fe (95.6 %), Mn (76.6 %), Pb (74.7 %), and Zn (70.6 %) were mainly transported in the particulate phase in both the dry and wet seasons. However, As (65.5 %), Co (60.3 %), and Se (77.6 %) were mainly transported in the dissolved phase in both seasons. The ratios of the dissolved Se concentration in river water to the Se concentration in the Earth's crust indicated significant and high mobility, especially in downstream sites, likely due to Se leaching from alluvial sediments. Seawater intrusion is likely the cause of As and Zn contamination in the dry season. Weathering of rocks and soils likely causes Al, Co, and Mn contamination in the wet season. The anthropogenic sources of contamination include the discharge of Mn and Zn from fertilizers in agriculture and the use of formulated feed in aquaculture. Approximately 52.98, 25.23, 5.68 and 0.63 tons of Fe, Al, Mn and Zn, respectively, are estimated to be transported from the river into the Gulf of Thailand each year.

Assessment of As, Cr, Cd, and Pb in urban surface water from a subtropical river: contamination, sources, and human health risk

ABSTRACT This work aimed to determine the level of some toxic elements (As, Cr, Cd, and Pb) in the water of the Rupsha River, Bangladesh, concerning their potential dangers to human exposure. The elemental concentrations (mg/L) were determined using Atomic Absorption Spectrometer and found to decrease in the order of Cr (0.041) > Pb (0.029) > As (0.004) > Cd (0.002). The level of elements in this river water surpasses various international limits, making it unfit for human consumption. Furthermore, the metal pollution index and contamination index indicated that the water was also unsuitable for this purpose. The elements chosen were persuasive to discern the hazard quotient of non-carcinogenic risk. Moreover, total targeted hazard quotient (TTHQ) values were found for adults and children within acceptable limits (TTHQ <1). The value of carcinogenic risk did not surpass the range (10−6 to 10−4) of the threshold limit. Due to their high-water consumption per unit of body-weight and physiological development, children were found to be more sensitive than adults. Multivariate analyses demonstrated that human activities were the primary origin of toxic elements in river water. According to the findings, urban and industrial effluents should be treated before being released into rivers. Development along the river bank must be carefully controlled to safeguard the river environment. In the end, this will improve the quality of the water and lower the chance that people will be exposed to metals.

Quantification of potentially toxic dissolved elements in river water using multivariate statistical approaches: a case study of Golmud River, China

Quantification of potentially toxic dissolved elements in river water using multivariate statistical approaches: a case study of Golmud River, China

Quantification of potentially toxic dissolved elements in River water using multivariate statistical approaches: a case study of Golmud River, China

Quantification of potentially toxic dissolved elements in River water using multivariate statistical approaches: a case study of Golmud River, China

Determination of elements in river water

Main textThe need for quality assessment of anthropogenic impact on environmental pollution is increasing due to discharge from various industries, the use of chemicals in agriculture and the consumption of fossil fuels. Diminishing resources such as natural waters used for the cultivation of agricultural products, plant and animal habitats are under severe pollution pressure and are at constant risk. Several parameters, such as Pb, Cd, Ni, Hg were listed by Water Framework Directive in Directive (2008/105/EC) in the priority substances. Cadmium and Hg were identified as priority hazardous substances whereas As is an important contaminant for its potential toxicological and carcinogenic effects.An inter-comparison study is organised in EURAMET TC-MC in order to demonstrate the capability participants for measuring five elements in river water. The participants carried out measurements for analytes: Pb, Cd, Ni and As as mandatory elements, and Se as an optional one. Participants were asked to perform the measurements with respect to the protocol provided.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

ВЗАИМОСВЯЗЬ ХИМИЧЕСКОГО СОСТАВА И УРОВНЯ ЗАГРЯЗНЕННОСТИ РЕЧНЫХ ВОД И ДОННЫХ ОТЛОЖЕНИЙ РЕК БАССЕЙНА СЕВЕРСКОГО ДОНЦА (В ПРЕДЕЛАХ РОСТОВСКОЙ ОБЛАСТИ)

The article considers the chemical composition features and pollution levels of river waters and sediments in the Seversky Donets River basin. The river waters pollution degree has been assessed using the specific combinatorial index of water pollution, and the river sediments pollution level has been evaluated using the conventional total pollution index and the integral contamination index of river sediments proposed by the authors. In order to compare the chemical compositions of the studied media we have used the concentration coefficients of elements in river waters and sediments based on the corresponding clarks. The physical and chemical features of the elements which contents differ significantly in the studied media have been analyzed in detail: namely manganese, copper, nickel, and lead. Physical and geographical and other factors that influence the distribution of elements within the river water – river sediments system in the study area have also been considered. It has been revealed that the level river sediments pollution in the Seversky Donets River basin is determined by elevated contents of nickel and lead. These elements are transferred mainly in a suspended form. It is demonstrated that the river waters pollution level depends on a number of macro- and microcomponents, and manganese and copper compounds make a significant contribution. It is concluded that the discrepancy between the levels of river sediments contamination and the river water pollution in the Seversky Donets River basin is mainly caused by the self-purification processes in river sediments.

An Integrated Approach in the Assessment of the Vlasina River System Pollution by Toxic Elements

Increasing pollutant levels in surface water are a very important problem in developing countries. In Serbia, the largest rivers are transboundary rivers that cross the border already polluted. Taking this into account, evaluation of the distribution characteristics, ecological risk, and sources of toxic elements in river water and surface sediments in the watercourses of the Vlasina watershed is of great significance for the protection of water resources in Serbia. A total of 17 sediment and 18 water samples were collected and analyzed by Inductively Coupled Plasma—Optical Emission spectrometry (ICP-OES) and Inductively Coupled Plasma—Mass spectrometry (ICP-MS) to determine micro- and macroelements contents. The geo-accumulation index (Igeo) was applied to determine and classify the magnitude of toxic element pollution in this river sediment. The contents of the studied toxic elements were below water and sediment quality guidelines. For studied river water, results of principal component analysis (PCA) indicated the difference in behavior of Cr, Mn, Ni, Cu, and As and V, respectively. Cluster analysis (CA) classified water samples according to As and Cu content. The PCA results revealed that lead in river sediments had different behavior than other elements and can be associated mainly with anthropogenic sources. According to the degree of Igeo, the majority of sediments in the Vlasina region were uncontaminated regarding studied toxic elements. The origin of elements is mostly from natural processes such as soil and rock weathering.

River water treatment by continuous electrocoagulation: insights into removal of acetaminophen, and natural organic matter

Abstract River water was treated by continuous electrocoagulation (EC) for acetaminophen (AP), natural organic matter (NOM measured as UV254), and removal of elements. HRT at 40 min with 0.5 mg/L AP exhibited the best removal efficiency for NOM (55.9%) and AP (53.4%) removal. Except for aluminium, other elements in river water were removed completely. The EC sludge (floating and settled) XRD spectrum showed peaks from AP were reduced, and the few peaks left were from aluminium hydroxide formed by EC. Several bonds in functional groups of AP and NOM were significantly deformed. FESEM images revealed that the sludge was highly porous material as needed for adsorption. EDAX showed that floating sludge had slightly higher carbon compared with settled sludge whereas nitrogen was higher in settled sludge. Other element concentrations in both sludges were similar, proving that water treatment was due to electro-floatation, adsorption, and sweep flocs. Single-factor ANOVA showed significant variance at HRT for NOM (F4.066 = 92.67, p = &amp;lt;0.05) and AP (F4.066 = 20.59, p = &amp;lt;0.05) removal. Variance was significant between treatments at different drug concentrations for NOM (F3.478 = 88.53, p = &amp;lt;0.05) and AP (F3.478 = 529.85, p = &amp;lt;0.05) removal. NOM removal correlated well with AP removal during continuous electrocoagulation.

Pollution of Water with Lead and Cadmium by the Effect of Adding Cities Waste in Al-Diwaniyah River, Iraq

This study was conducted to know the effect of adding sewage and industrial water on the concentration of Lead and Cadmium elements in river water during different seasons of the year in Al-Diwaniyah province / Iraq, Water samples were collected in 1 L water bottles with three replicates for all location and during four seasons: summer (July) 2019, autumn (October) 2019, winter (January) 2020, and spring (April) 2020 with three seasons. location : The first location was located at the entrance to the city of Al-Diwaniyah (Al-suniyah), Which represents the control treatment where it takes place before the various pollution ports that flow into the river (such as sewage, hospital waste, factory waste, sewage … etc.), the second location in the city center (Rifaat neighborhood) and the third location in the Sudair area, which represents the last location of the city of Al-Diwaniyah after the end of all estuaries and sources of pollution. The results of the study found that the concentration of Lead and Cadmium in the river’s water increased with an increase in its slope from the first location to the third location for both elements (Lead and cadmium), That their concentration increased with the increase in the addition of residues, and the highest pollution concentration was in the summer, The Lead concentration was 0.1303 μg.L−1, In the third location and the lowest concentration in the winter season, it reached 0.0033 μg.L−1 in the first location, while the highest concentration of Cadmium in the summer season was 0.05533 μg.L−1 in the third location and the lowest concentration in the winter and spring seasons was 0.00 in the first location, This indicates an increase in the concentration of the two elements in the river water and (As it affects humans and different neighborhoods), which causes health and toxic damage according to the type of element and the type of this organism on the one hand, and the elemental pollution is affected according to the seasons of the year in terms of uses and waste added, as well as the quantities of water contained in the river on the other hand.

Distribution characteristics, enrichment patterns and health risk assessment of dissolved trace elements in river water in the source region of the Yangtze River

Abstract The security of water environment in the source region of the Yangtze River (SRYR) is vital to the water environment security of the whole basin. The results showed that the rivers in the SRYR were weakly alkaline and the values of total solid solubility (TDS), electrical conductivity (EC), turbidity concentration and salinity were higher than the values in the middle and lower reaches of the Yangtze River. The results showed that the dissolved trace elements detected displayed obvious regional distribution characteristics, showing a high concentration trend in the Chumar River, low in the Dangqu, and middle in the Tong River. All water quality indexes in the SRYR met the surface water environmental quality standard of class II based on GB 3838-2002 except Hg, while the average concentration of As exceeded 10 μg/L. The main enrichment elements in the SRYR were Li, Se, As and Pb, and their concentrations were far higher than the average concentration of the world rivers. Moreover, the HI and HQingrstion of children caused by As in the SRYR were greater than 1. This study could provide basic data for water environment protection and water resource management in the SRYR.

Potentially toxic elements in river water and associated health risks in Ropar Wetland, India and its vicinity

In the present study, quality of surface water from five different locations on the banks of river Sutlej in Ropar wetland was determined by estimation of physico-chemical parameters; water quality indices; contents of arsenic, cadmium, cobalt, chromium, copper, iron, manganese, lead and zinc; determination of genotoxic potential of water samples using Allium cepa root chromosomal aberration assay and plasmid pBR322 DNA nicking assay; and assessment of associated possible human health risks for adults and children. River water was slightly alkaline, moderate to very hard, non-saline, genotoxic and unsuitable for both drinking and irrigation. Among 20 surface water samples analysed, contents of Cd, Cr, Cu, Fe, Mn and Pb in 11, 7, 3, 15, 14 and 13 samples exceeded the safe limits (mg/L) of 0.003, 0.05, 0.05, 0.30, 0.10 and 0.01, respectively. Ingestion of surface posed higher health risk than dermal contact, where Co was major contributor to mean hazard index (3.26–10.72 for adults and 4.22–13.87 for children). Hazard index for dermal contact in both age groups was < 1.00. Cr was found to be primarily responsible for high total cancer risk posed by both routes of exposure, i.e. ingestion (6.83E−04 to 2.03E−03 for adults and 7.58E−05 to 2.25E−04 for children) and dermal contact (5.15E−05 to 2.02E−04 for adults and 6.23E−06 to 2.44E−05 for children). Prolonged exposure to contaminated surface water may elevate the human health risk in the study area; therefore, pre-treatment of river water is necessary before its utilization by human population of the study area.

Determination of the Concentration of Li, Mn, Ni, Co, Fe used for Lithium Ion Battery and Nickel Metal Hydride Battery in River Waters

The concentration of Li, Mn, Ni, Co, Fe in Japanese rivers those are used to the lithium ion battery(LIB), nickel metal hydride battery(NiMHB）etc. were determined using ICP-MS and ICP-AES. Fifty five samples were collected around the LIB and NiMHB factory etc. from Miyagi prefecture to Tottori prefecture. Because the concentration of Mn and Fe was high, we measured them by ICP-AES and determined other elements by ICP-MS. Because 58Ni was interfered by 58Fe, 60Ni was used for the measurement. In the three samples among 55 samples, three or more elements of Li, Mn, Ni and Co showed more than 5 times the concentration of river in Japan. In 14 samples, 2 elements of Li, Mn, Ni and Co showed more than 5 times the average value of the river in Japan. Since the use of LIB and NiMHB will increase here after, it will be important to pay attention to the concentrations of these elements in river waters.

Study of Toxic Elements in River Water and Wetland Using Water Hyacinth (Eichhornia crassipes) as Pollution Monitor.

The concentration of toxic elements present in surface water of Sutlej River and Harike wetland besides Eichhornia crassipes, commonly known as water hyacinth, is estimated employing inductively coupled plasma mass spectrometry (ICP‐MS). Toxic elements such as cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb), uranium (U), and zinc (Zn) are identified in the river as well as in Harike wetland catchment. Accumulation of elements in different parts of the water hyacinth plant is observed with the roots exhibiting maximum affinity followed by stem and then leaves. The removal efficacy of pollutants by water hyacinth is estimated using bioconcentration factor (BCF) index. It is found to be different for different elements, with Mn showing the highest and U the lowest magnitude. The study carried out in the present work indicates that rhizofiltration could play an important role in controlling pollutant load.

Characteristics, sources, water quality and health risk assessment of trace elements in river water and well water in the Chinese Loess Plateau

Water resources and water quality are restrictive factors in the Chinese Loess Plateau (CLP), a unique area with most severe soil erosion, fragile ecology and water shortage. River and well water samples were firstly analyzed, and multiple methods and indexes, including principal component analysis (PCA), correlation analysis (CA), sodium adsorption ratio (SAR), water quality index (WQI), hazard quotient (HQ), and hazard index (HI), were used to investigate characteristics, water quality and health risk assessment of trace elements in CLP. The average trace elements concentrations were higher than the world average with a slightly alkaline characteristic. PCA and CA showed that Al, Fe, Li, B, As, and F had natural origins from loess weathering and leaching; Cr, Pb, Cd, Cu, Ag, and Tl were mainly from anthropogenic input; Co, Ni, and Mn were dominated by both anthropogenic and natural sources. The poor river water quality was mainly related with high sodium (alkalinity) and salinity hazard. The poor well water quality samples with high WQI values, especially for As, Cr, and B, were distributed in the northwest and the Fenhe River sub-basin. The pollution level of trace elements in rivers in CLP was in medium level compared with other rivers worldwide. Arsenic pollution was the worst in well water and was the potential pollutant in river water especially for children. Arid climate together with anthropogenic input and special water characteristics (high Na, pH, and low Ca) aggravated As pollution. More work should be done to monitor the secular variation and remove As in the high As areas. The results of this study can provide the basic data for efficient water management and human health protection in CLP.

Forms of trace arsenic, cesium, cadmium, and lead transported into river water for the irrigation of Japanese paddy rice fields

In this study, we focus on the behavior of geogenic, toxic trace elements, particularly As, Cs, Cd, and Pb, during their transportation in two rivers for irrigation commonly used in monsoon Asia; one river originates from an active volcano, Mt. Asama, and the other originates from a currently inactive volcano, Yatsugatake Mountains in Nagano, Japan. These rivers were investigated to understand the role of river water as a pollutant of rice and other aquatic plants (via irrigation) and aquatic animals. The results indicated that the behavior of toxic trace elements in river water are likely controlled by their interactions with particulate Fe, Al, and Ti compounds. The majority of Pb and Cd is transported as particulate matter with Fe, Al, and Ti, while the majority of As is transported in the dissolved form, predominantly as arsenate, with low abundance of particulate matter. Cs is transported either as the dissolved form or as particulate matter in both rivers. The investigated elements are transported in the rivers as particulate and dissolved forms, and the ratio of these forms is controlled by the pH and presence of particulate Fe, Al, and Ti phases in the river water. With respect to Cs in both rivers, the parameter governing the concentration and transportation of Cs, in the bimodal form (i.e., particulate and dissolved forms), through the river possibly shifts from sorption to pH by particulate Fe–Al–Ti, according to the abrupt increase in the concentration of Cs in the river. The chemical attraction of particulate Fe–Al–Ti for Cs is weaker than that for Pb and Cd, indicating that the lower electronegativity of Cs weakens the chemical attraction on a colloid for the competitive sorption with the other trace elements. The different relationships between As and Fe in the river and in the irrigation water and soil water, as well as those in paddy rice, suggested that As in paddy rice is not directly derived from As in the irrigation water from the river under flooding.

Mobility of nutrients and trace metals during weathering in the late Archean

The evolution of the geosphere and biosphere depends on the availability of bio-essential nutrients and trace metals. Consequently, the chemical and isotopic variability of trace elements in the sedimentary record have been widely used to infer the existence of early life and fluctuations in the near-surface environment on the early Earth, particularly fluctuations in the redox state of the atmosphere. In this study, we applied late Archean weathering models (Hao et al., 2017), developed to estimate the behavior of major elements and the composition of late Archean world average river water, to explore the behavior of nutrient and trace metals and their potential for riverine transport. We focused on P, Mn, Cr, and Cu during the weathering of olivine basalt.In our standard late Archean weathering model (pCO2,g = 10−1.5 bars, pH2,g = 10−5.0 bars), crustal apatite was totally dissolved by the acidic rainwater during weathering. Our model quantitatively links the pCO2,g of the atmosphere to phosphate levels transported by rivers. The development of late Archean river water (pH = 6.4) resulted in riverine phosphate of at least 1.7 μmolar, much higher than at the present-day. At the end of the early Proterozoic snowball Earth event when pCO2,g could be 0.01–0.10 bars, river water may have transported up to 70 μmolar phosphate, depending on the availability of apatite, thereby stimulating high levels of oxygenic photosynthesis in the marine environment.Crustal levels of Mn in olivine dissolved completely during weathering, except at large extents of weathering where Mn was stored as a component of a secondary carbonate mineral. The corresponding Mn content of river water, about 1.2 μmolar, is higher than in modern river water. Whiffs of 10−5 mole O2 gas or HNO3 kg−1 H2O resulted in the formation of pyrolusite (MnO2) and abundant hematite and simultaneous dramatic decreases in the concentration of Mn(II) in the river water.Chromite dissolution resulted in negligible dissolved Cr in Archean river water. However, amorphous Cr(OH)3 representing easily-weatherable Cr-bearing minerals dissolved totally during the weathering simulations, resulting in concentrations of Cr(III) in the river water of up to 0.14 μmolar, higher than at the present-day.Late Archean weathering of accessory chalcopyrite produced chalcocite and bornite, and extremely low concentrations of Cu (<10−15 molar) because of the low solubilities of the copper sulfides. However, pulses of either O2,g or HNO3 produced native copper, chalcocite, and bornite, much more hematite, and river water containing levels of dissolved Cu comparable to the present-day. Copper mineralogy predicted by weathering models might provide a new correlation with evidence from studies of copper mineral evolution.Overall, our results implied that the redox state of the atmosphere, the pH of surface waters, and the availability of easily-weatherable minerals are all important factors controlling the dissolution of trace elements in river water. Interpretation of the sedimentary signatures of trace elements should consider not only the redox state but also the pH and availability of accessory minerals.

Weathering of evaporites: natural versus anthropogenic signature on the composition of river waters

Weathering of evaporites strongly influences the chemistry of continental runoff, making surface waters poorly exploitable for civil uses. In south-central Sicily, this phenomenon is worsened by the occurrence of abandoned landfills of old sulphur and salt mines. The industrial evolution of the Bosco-S. Cataldo mining site leaved two landfills from the early exploitation of a sulphur mine followed by that of a kainite deposit. In particular, the weathering of these landfills leads the dissolved salt (TDS) values up to about 200 g l−1 in the Stincone–Salito Stream waters. This process induces the V, Cr and Fe desorption from sediments and particulates in the aqueous phase under reducing conditions. At the same time, the weathering of salt minerals releases Rb and Cs, originally contained in halite. The overall processes lead to the V, Cr, Fe, Rb and Cs enrichment of waters from the Stincone–Salito Stream system accompanied by a sharp growth of As content, up to about 13 µg l−1, caused by As release from Fe-bearing solids due to the high salinity. Therefore, the scenario of the weathering of Bosco-S. Cataldo mine landfills depicts an environment strongly influenced by effects of the growing salinity and euxinic water conditions where the attained TDS, Eh and pH conditions reduce the natural scavenging capability of the interested river system, favouring a growth of residence time of toxic elements in river waters.

Application of membrane processes in fractionation of elements in river water.

The influence of wastewater treatment plant (WWTP) effluents from one microelectronic industrial zone on element concentrations and partitioning in river water was investigated. The stepwise membrane filtration is used to distinguish different size fractions including large particulate (>18 μm), particulate (0.2-18 μm), colloidal/nanoparticle (10 kDa-0.2 μm) and truly dissolved fractions (<10 kDa) in river water samples and WWTP effluents. Results demonstrated that anthropogenic inputs (WWTP effluents and industrial area) had an important influence on concentrations and partitioning of some elements in river water. Mass balance results showed that membrane filtration processes could realize a good fractionation for many elements (good recoveries) in water samples. Flux decline during 0.2 μm and 10 kDa filtrations were analyzed, and corresponding fouling mechanisms are discussed.

Geochemical interaction between the freshwater and marine hydrospheres

The results of more than 40years long authors’ investigations in the field of the freshwater (river input) and marine (ocean waters) hydrospheres are summarized. The latest estimations of the global average concentrations of many chemical elements in river water and suspended matter and in ocean water and suspended matter are presented. It is shown that particulate suspended forms of many elements are predominant in river waters (“rivers are the kingdom of suspended forms of elements”), while their dissolved forms prevail in ocean waters (“ocean is the kingdom of dissolved forms of elements”). Sedimentary and biogeochemical processes of the river material transformation in the river-sea mixing zone (the so-called “marginal filter of the ocean”) were studied thoroughly. It was shown that radical quantitative and qualitative changes of dissolved and particulate suspended substances take place in this zone, resulting in the governed transformation of dissolved forms into suspended particulate forms and their following deposition on the bottom. The first data on the losses of 35 chemical elements in the river-sea mixing zone are presented. These data prove that the concentrations of dissolved elements in river and ocean waters are in regular and close relationship with their losses in the river-sea mixing zone and with the types of element distribution in ocean water column (conservative, biogenic, and lithogenic). This indicates the existence of a geochemical system in the entire (freshwater and marine) hydrosphere, which calls for deep and detailed investigations.

Lithological controls of dissolved trace elements: carbonate versus silicate

Trace elements in river waters can give information about chemical weathering and aqueous environments, but the systematics of trace elements in river waters have been poorly understood. Here, concentrations of dissolved trace elements were determined to investigate factors controlling their seasonal and spatial variations in the Han River Basin (HR), South Korea. Two major branches, the North Han River (NHR) and South Han River (SHR), differed largely in concentrations of their trace elements (e.g., As, B, Co, Li, Ni, and U), with the NHR having low concentrations and the SHR having high concentrations. This difference can be mainly attributed to the underlying lithology of the watersheds, namely, silicates in the NHR and carbonates plus clastic sediments containing black slate rich in trace elements in the SHR. Seasonally, concentrations of trace elements such as Al, Co, Fe, and Rb in the NHR were higher in summer, indicating that these trace elements exist as a colloid-borne form because of intensive physical weathering in the NHR. In contrast, the SHR showed little or no seasonal variation in concentrations of those trace elements.