Characteristics of trace metals and phosphorus in seawaters offshore the Yangtze River

Field determination of trace concentrations of hazardous metals in waters by portable EDXRF

A new effective method has been developed for field determination of trace concentrations of cadmium, arsenic, zinc, copper, nickel, chromium, and lead in waters (e.g., surface and wastewater) using an energy dispersive X-ray fluorescence (EDXRF) analyzer. Trace concentrations cannot be determined by EDXRF without preconcentration. Agar was used for the preconcentration of these potentially toxic elements (PTE). Metals are trapped in the three-dimensional network of agar gel. Subsequent swelling of the gel leads to more effective preconcentration. The swollen gels with PTE were analyzed by a portable energy dispersive X-ray fluorescence analyzer Delta Professional X (pXRF). The preconcentration factors for each PTE were determined. With pXRF, the detection limits were 7, 5, 6, 7, 9, 47, and 22 µg/L for Cr, Ni, Cu, Zn, As, Cd, and Pb, respectively. A reference material was used to assess the methodology performance, and it has a very good agreement. The optimized and verified methodology was tested in practice at the special chemical unit of the Fire Rescue Service of the Czech Republic. PTE were determined by pXRF in a mobile chemical laboratory in field analysis. The measured values were compared with those determined via inductively coupled plasma mass spectrometry (ICP-MS) and were in good agreement. Our method was applied to real wastewater samples collected during after a fire of accumulation batteries of domestic photovoltaic power plants, allowing accurate real-time estimation of PTE concentrations. Obtaining reliable data during an ecological accident has a very important role in minimizing the subsequent environmental impact of the accident.

Measurements and analysis of nitrogen and phosphorus in oceans: Practice, frontiers, and insights

Nitrogen and phosphorus concentrations in oceans have been extensively studied, and advancements in associated disciplines have rapidly progressed, enabling the exploration of novel and previously challenging questions. A keyword analysis was conducted using the Scopus database to examine chronological trends and hotspots, offering comprehensive insights into the evolution of marine nitrogen and phosphorus research. For this purpose, author keyword networks were developed for the periods before 1990, 1990 to 2000, 2001 to 2011, and 2012 to 2022. Furthermore, analytical techniques employed in the recent decade to determine nitrogen and phosphorus concentrations in seawater were assessed for their applicability and limitations through a critical review of more than 50 journal articles. Taxonomy and nitrogen biogeochemistry were the prominent research interests for the first two periods, respectively, while stable isotopic tracking of nitrogen and phosphorus processes emerged as the dominant research focus for the last two decades. The integration of macroeconomic factors in research development and the chronological rise of interdisciplinary research were identified. Conventional analytical techniques such as spectrophotometry, colorimetry, fluorometry, and elemental analysis were noted, along with emerging techniques like remote sensing and microfluidic sensors.

Watershed seasonality regulating vanadium concentrations and ecological risks in the coastal aquatic habitats of the northwest Pacific

Vanadium is a component of different natural and industrial products and a widely used metal, which, nonetheless, has only garnered attention in recent years owing to its potential risks. Six sampling trips were conducted over different seasons and years, collecting 108 samples from rivers and 232 from the bays and analyzed using high-precision inductively coupled plasma mass spectrometry. This study investigated the sources, spatiotemporal characteristics, and risks of vanadium in the aquatic ecosystems of two typical bays of the Northwest Pacific that have strong links with vanadium-related industries. Likewise, the health and ecological risks were assessed using probabilistic and deterministic approaches. Overall, vanadium concentrations were higher in Jiaozhou Bay (JZB: 0.41-52.7 μg L^-1) than in Laizhou Bay (LZB: 0.39-17.27 μg L^-1), with concentrations higher than the majority of the worldwide studies. Vanadium-realted industries significantly impacted (p < 0.05) the metal concentrations in the rivers with 54.22% (40.73-150%) and 54.45% (27.66%-68.87%) greater concentrations in JZB and LZB rivers. In addition, vanadium exhibited significant seasonal variation, and higher values were quantified during the monsoon period at LZB owing to the greater catchment area. Impacted by smaller freshwater inputs, the post-monsoon period had substantial impacts on JZB, and vanadium in the rivers and bays was significantly higher during the winter. Despite some concentrations being higher than that indicated in the drinking water guidelines established by China, vanadium presents low to null risks to the population as per both approaches. Last, species with limited resilience are likely to face medium to high risks, with an incidence of 65-93% using the probabilistic method and 52-97% using the deterministic assessment.

Ecological risk assessment of trace metals and comprehensive contamination indicators in the coastal waters of Macao, South China Sea

Few systematic and scientific assessments have been conducted on marine environmental quality in the coastal waters of Macao, a major city in the Pearl River Delta, China. In this study, we investigated the spatial distribution of trace metals (TMs) and comprehensive contamination indicators of marine water in Macao and evaluated their ecological risks. The total amount of typical TMs (∑TMs) in surface water ranged from 2.71 μg/L to 201 μg/L. ∑TMs (Hg, As, and Cd) in sediments ranged from 0.34 mg/kg to 54.8 mg/kg. TM contamination in surface water was influenced by spatial position and tidal current direction. The spatial distribution and correlation analysis of TMs and comprehensive contamination indicators were assessed, and ecological risk assessment indicated that the surface water and sediments in coastal waters of Macao are of relatively good quality, although high sulfide levels could be detected in surface water.

Distribution and composition of suspended matters in the wintertime in the East China Sea

Total suspended matters (TSMs), as the sediment precursor, directly affect the mass exchange and sedimentation in the East China Sea (ECS). Ultrafine suspended matters (USMs) are an important component of the TSMs, and may play a significant role in regulating pollutant transfer and shaping biological communities. However, the conventional filtration may cause the loss of USMs because the filter membranes with the pore size of 0.45 μm were adopted to collect TSMs; and consequently, no data on USMs are currently available in continental shelves. In this study, the TSMs and USMs in the wintertime in the ECS were collected by using the filter membranes with the pore size of 0.22 μm for investigating their compositions, distributions and exchanges for the first time. The results show that the TSMs consisted of mineral particles (35-80%), biological fragments (10-50%), and flocs (10-40%); and mainly accumulated along the coastal belt and in southwest of the Cheju Island. Comparatively, the USMs were composed of fine biological fragments (10-70%), mineral particles (15-70%), and unrecognizable particles with various shapes (15-35%). They exhibited a clear heterogeneous distribution, namely, accumulated along the coastal belt and outer shelf, but dispersed in the mid-shelf, implying that USMs might be jointly controlled by biological activities, terrestrial inputs and hydrodynamic system in the ECS and the Yellow Sea. The distinct distribution difference between TSMs and USMs denotes their different exchange styles, i.e., for TSMs active in north of the ECS, and weak along the coastal front zone and 100 m isobath; while for USMs almost inactive along the coastal front zone, and active in the outer shelf. Our results may provide a novel clue for evaluating the contribution of TSMs to sedimentation, pollutant transfer and maintenance of marine biological communities with emphasis on the new method for collecting TSMs and USMs in the ECS.

Influence of humic substances on iron distribution in the East China Sea

The influence of humic substances (specifically humic and fulvic acids, referred to as HS-HA and HS-FA) as well as other factors, such as major nutrient concentrations of total dissolved nitrogen (TDN), total dissolved phosphate (TDP) and hydrologic factors, on the distribution of total dissolved iron (DFe) and the chemical speciation of DFe was studied in the East China Sea (ECS) during a summer cruise in 2013. As the wide rage fraction of nature organic matter, the HS-HA, HS-FA in ESC contains most part of the organic ligand (Lt) of DFe. The concentrations of HS-HA, DFe and Lt in coastal water masses were higher than those in the water masses affected by the Kuroshio Current. The highest concentrations of HS-HA and DFe were observed in surface water at stations MT1 and MC4, with the value of 336.5 μg SRHA/L and 20.3 nmol/L, respectively, whereas, the lowest concentrations of HS-HA and DFe were observed in surface waters with the value of 149.6 μg SRHA/L and 0.4 nmol/L, respectively. HS-HA concentrations were more conservative than that of DFe. The DFe which were combined by unit weight HS-HA (mg^-1, IB) in the surface and bottom waters quickly decreased with increasing salinities from the Yangtze River estuary to the southeast of the ECS. Average IB values in bottom waters were higher than those in surface waters. This study indicated that Yangtze River dilution water and cold water from the Yellow Sea were the main source of HS-HA and DFe in ECS.

Dissolved trace elements in Hooghly (Ganges) River Estuary, India: Risk assessment and implications for management

The study presents a spatio-seasonal distribution of 13 trace elements in the surface water (0-5 cm) along the north-south gradient of Hooghly River Estuary, India, and subsequently evaluates the human health risk by adopting USEPA standards. An overall homogeneous spatial distribution of elements was pronounced, whereas an irregular and inconsistent seasonal pattern were recorded for the majority of the elements. The concentration range (μg/l) of the elements and their relative variability were obtained as follows in the decreasing order: Al (55,458-104,955) > Fe (35,676-78,427) > Mn (651.76-975.78) > V (85.15-147.70) > Si (16.0-153.88) > Zn (26.94-105.32) > Cr (21.61-106.02) > Ni (19.64-66.72) > Cu (34.70-65.80) > Pb (26.40-37.48) > Co (11.16-23.01) > As (0.10-8.20) > Cd (1.19-5.53). Although Pb, Ni, Cr, Al, Fe, and Mn exceeded the WHO prescribed threshold limit for drinking water, Metal Pollution Index values (8.02-11.86) superseded the upper threshold limit endorsing adverse impact on biota. The studied elements were justified to have a non-carcinogenic risk as derived from hazard quotient and hazard index values. However, the trace elements As, Cd, Pb, and Cr exceeded the upper limit of cancer risk (10^-4), thereby leading to carcinogenic risk concern for both children and adult population groups, where children are more susceptible than the adults. Hence, evaluation of bioavailable fractions of the elements is required for proper management of this stressed fluvial system.

Capacity of humic substances to complex with iron at different salinities in the Yangtze River estuary and East China Sea

The iron binding capacities (IBC) of fulvic acid (FA) and humic acid (HA) were determined in the salinity range from 5 to 40. The results indicated that IBC decreased while salinity increased. In addition, dissolved iron (dFe), FA and HA were also determined along the Yangtze River estuary’s increasing salinity gradient from 0.14 to 33. The loss rates of dFe, FA and HA in the Yangtze River estuary were up to 96%, 74%, and 67%, respectively. The decreases in dFe, FA and HA, as well as the change in IBC of humic substances (HS) along the salinity gradient in the Yangtze River estuary were all well described by a first-order exponential attenuation model: y(dFe/FA/HA, S) = a₀ × exp(kS) + y₀. These results indicate that flocculation of FA and HA along the salinity gradient resulted in removal of dFe. Furthermore, the exponential attenuation model described in this paper can be applied in the major estuaries of the world where most of the removal of dFe and HS occurs where freshwater and seawater mix.