Jihua Liu

Assessing metal toxicity in sediments using the equilibrium partitioning model and empirical sediment quality guidelines: A case study in the nearshore zone of the Bohai Sea, China

Surface sediments were collected from five nearshore (wastewater discharges, aquaculture facilities and a seaport) sites in Bohai Bay and Laizhou Bay, China. The equilibrium partitioning (EqP) model and empirical sediment quality guidelines (SQGs) were applied to assess the potential metal toxicity in the collected sediments. The results show that, based on the EqP model, 35% of stations exhibited potential metal toxicity. Several metals (Cu, Ni and Cr) exceeded the empirical SQGs (9-93% of the time), however these guidelines may not be suitable for use in the Bohai Sea owing to the background concentrations. The EqP model is a more useful method for assessing potential metal toxicity in Bohai Sea sediment than the empirical SQGs. Additionally, we have provided new understanding about methods for assessing sediment metal toxicity in the Bohai Sea that may be useful in other coastal areas in China.

Extensive study of potential harmful elements (Ag, As, Hg, Sb, and Se) in surface sediments of the Bohai Sea, China: Sources and environmental risks ☆

This study analyzed 405 surface sediment samples, obtained from across the Bohai Sea, for concentrations of five potentially harmful elements (Ag, As, Hg, Sb, and Se) and several ancillary parameters (Al, Fe, Mn, total organic carbon (TOC), and grain size). Statistically, the spatial distributions of these elements were correlated positively with Al, Fe, TOC, and grain size, indicating natural sources for these elements or common accumulation mechanisms. The assessment of potential environmental risk with empirical sediment quality guidelines showed that a significant proportion of the samples had As and Sb concentrations that exceeded the effects range low (ERL) or T20 values in the Bohai Sea, indicating the potential for adverse biological effects. However, the assessment results differed when using evaluation methods that considered background values. Based on the geoaccumulation index (Igeo), Hg and Ag were found to have the highest percentages (35% and 60%, respectively) in samples that were moderately contaminated. The estimated contamination degree (Cd) suggested higher contamination levels for the entire area, with 69% of the samples being moderately contaminated. Generally, except for some local hotspots, such as Jinzhou Bay, the contamination levels of these elements in the Bohai Sea were established as slight to moderate. Samples from the Jinzhou Bay area had concentrations that were 10-100 times higher than in the rest of the Bohai Sea, indicating severe contamination.

Sources, geochemical speciation, and risk assessment of metals in coastal sediments: a case study in the Bohai Sea, China

To investigate the sources and toxicity of metals in Bohai Sea sediments, concentration and geochemical speciation of metals of surface sediments were measured. Metal distributions and principal component analysis suggested that Zn, Pb, Cd, and Ag were largely derived from anthropogenic sources, whereas the majority of the other metals studied here were found to have been derived from natural rock weathering and calcareous marine biota. The major sources of anthropogenic metal inputs to the study region are from the mining industry, port transport services, vehicle exhausts, and agricultural runoff. Empirical sediment quality guidelines and the risk assessment code were used to evaluate the metal toxicities in this area. Our results show that Cd presents a high risk to the ecological system because it was found in the non-residual phase, which tends to be weakly bound and highly bioavailable; Cu, Pb, Ni, and Co pose a low risk; Zn and Cr present no risk. The use of the threshold effects level and effects range-low values of Cd and Cr as guidelines for the Bohai Sea are of limited use as they do not account for the bioavailability and toxicity of the elements in marine environments. Assessment of the annual metal fluxes from riverine and atmospheric sources indicates that the largest contributions of metals to the Bohai Sea were derived from the suspended particulate load of rivers. Furthermore, it was found that the main depositional zones for metals in the Bohai Sea were in estuaries and the center mud zones.

Persistent effects of the Yellow River on the Chinese marginal seas began at least ~880 ka ago

The Yellow River (or Huanghe and also known as China’s Sorrow in ancient times), with the highest sediment load in the world, provides a key link between continental erosion and sediment accumulation in the western Pacific Ocean. However, the exact age of its influence on the marginal sea is highly controversial and uncertain. Here we present high-resolution records of clay minerals and lanthanum to samarium (La/Sm) ratio spanning the past ~1 million years (Myr) from the Bohai and Yellow Seas, the potential sedimentary sinks of the Yellow River. Our results show a climate-driven provenance shift from small, proximal mountain rivers-dominance to the Yellow River-dominance at ~880 ka, a time period consistent with the Mid-Pleistocene orbital shift from 41-kyr to 100-kyr cyclicity. We compare the age of this provenance shift with the available age data for Yellow River headwater integration into the marginal seas and suggest that the persistent influence of the Yellow River on the Chinese marginal seas must have occurred at least ~880 ka ago. To our knowledge, this study provides the first offshore evidence on the drainage history of the Yellow River within an accurate chronology framework.

DISTRIBUTION PATTERN OF POC OF THE SPRING SUSPENDED MATTER IN THE YELLOW SEA AND EAST CHINA SEA: DISTRIBUTION PATTERN OF POC OF THE SPRING SUSPENDED MATTER IN THE YELLOW SEA AND EAST CHINA SEA

A survey of the suspended matter in the South Yellow Sea and the north part of the East China Sea was conducted in April to May 2006.Based on the data from the samples collected at 45 stations,the horizontal and vertical distribution patterns of the particulate organic carbon(POC) of the Yellow Sea and the East China Sea were presented in this paper.And the sources of the POC and the influencing factors were further discussed according to the particulate nitrogen(PN) and C/N.The results show that the highest concentration of surface suspended POC appear at the area around 123° E,31° N in the East China Sea,while the value was lower in the south Yellow Sea and the area to the east of 124° E in the East China Sea.The concentration of surface POC in the vicinity of the Changjiang Estuary is obviously higher than that in other areas,indicating the primary influence by the Changjiang diluted water.However,the highest concentration of bottom suspended POC occurs at the area adjacent of 121.5° E,33.5° N in the south Yellow Sea.And also there was a second highest concentration around 124.5° E,31.5° N in the East China Sea.The value was relative lower in areas to the south of 31° N in the East China Sea.It could be inferred that the high concentration of bottom POC was mainly controlled by the resuspension of sediments.The C/N suggests that the POC of the study area was mainly from the ocean.It is concluded that currents play a critical role in the distribution of POC of suspended matters.Therefore,different areas under the contral of the Yellow Sea Warm Current,the Subei Coastal Current and the Yangtze Diluted Water could be distinguished.The distribution pattern of the POC in the study area was controlled by both the sources of the organic matter and the ocean currents.

The determination of 52 elements in marine geological samples by an inductively coupled plasma optical emission spectrometry and an inductively coupled plasma mass spectrometry with a high-pressure closed digestion method

An improved analytical method to determine the content of 52 major, minor and trace elements in marine geological samples, using a HF-HCl-HNO3 acid system with a high-pressure closed digestion method (HPCD), is studied by an inductively coupled plasma optical emission spectrometry (ICP-OES) and an inductively coupled plasma mass spectrometry (ICP-MS). The operating parameters of the instruments are optimized, and the optimal analytical parameters are determined. The influences of optical spectrum and mass spectrum interferences, digestion methods and acid systems on the analytical results are investigated. The optimal spectral lines and isotopes are chosen, and internal standard element of rhodium is selected to compensate for matrix effects and analytical signals drifting. Compared with the methods of an electric heating plate digestion and a microwave digestion, a high-pressure closed digestion method is optimized with less acid, complete digestion, less damage for digestion process. The marine geological samples are dissolved completely by a HF-HCl-HNO3 system, the relative error (RE) for the analytical results are all less than 6.0%. The method detection limits are 2–40 μg/g by the ICP-OES, and 6–80 ng/g by ICP-MS. The methods are used to determine the marine sediment reference materials (GBW07309, GBW07311, GBW07313), rock reference materials (GBW07103, GBW07104, GBW07105), and cobalt-rich crust reference materials (GBW07337, GBW07338, GBW07339), the obtained analytical results are in agreement with the certified values, and both of the relative standard deviation (RSD) and the relative error (RE) are less than 6.0%. The analytical method meets the requirements for determining 52 elements contents of bulk marine geological samples.

Diversity and distribution of catechol 2, 3-dioxygenase genes in surface sediments of the Bohai Sea

Catechol 2, 3-dioxygenase (C23O) is the key enzyme for aerobic aromatic degradation. Based on clone libraries and quantitative real-time polymerase chain reaction, we characterized diversity and distribution patterns of C23O genes in surface sediments of the Bohai Sea. The results showed that sediments of the Bohai Sea were dominated by genes related to C23O subfamily I.2.A. The samples from wastewater discharge area (DG) and aquaculture farm (KL) showed distinct composition of C23O genes when compared to the samples from Bohai Bay (BH), and total organic carbon was a crucial determinant accounted for the composition variation. C6BH12-38 and C2BH2-35 displayed the highest gene copies and highest ratios to the 16S rRNA genes in KL, and they might prefer biologically labile aromatic hydrocarbons via aquaculture inputs. Meanwhile, C7BH3-48 showed the highest gene copies and highest ratios to the 16S rRNA genes in DG, and this could be selective effect of organic loadings from wastewater discharge. An evident increase in C6BH12-38 and C7BH3-48 gene copies and reduction in diversity of C23O genes in DG and KL indicated composition perturbations of C23O genes and potential loss in functional redundancy. We suggest that ecological habitat and trophic specificity could shape the distribution of C23O genes in the Bohai Sea sediments.

Kr and Xe isotopic compositions of Fe-Mn crusts from the western and central Pacific Ocean and implications for their genesis

Kr and Xe nuclide abundance and isotopic ratios of the uppermost layer of Fe-Mn Crusts from the western and central Pacific Ocean have been determined. The results indicate that the Kr and Xe isotopic compositions, like that of He, Ne and Ar, can be classified into two types: low 3He/4He type and high 3He/4He type. The low 3He/4He type crusts have low 84Kr and 132Xe abundance, while the high 3He/4He type crusts have high 84Kr and 132Xe abundance. The 82Kr/84Kr ratios of the low 3He/4He type crusts are lower than that of the air, while the 83Kr/84Kr and 86Kr/84Kr ratios are higher than those of the air. The Kr isotopic ratios of the higher 3He/4He type crusts are quite similar to those of the air. The 128Xe/132Xe, 130Xe/132Xe and 131Xe/132Xe ratios of the low 3He/4He type sample are distinctly lower than those of the air, whereas the 129Xe/132Xe, 134Xe/132Xe and 136Xe/132Xe ratios are higher than those of the air. The low 3He/4He type samples have the diagnostic characteristics of the MORB, with excess 129, 131, 132, 134, 136Xe relative to 130Xe compared with the solar wind. The 128Xe/132Xe, 130Xe/132Xe and 131Xe/132Xe ratios of the high 3He/4He type samples are slightly higher than those of the air, and the 129Xe/132Xe, 134Xe/132Xe and 136Xe/132Xe ratios are qiute similar to those of the air. The noble gases in the Fe-Mn crusts are derived from the lower mantle, and they are a mixture of lower mantle primitive component, radiogenic component and subduction recycled component. The helium isotopic ratios of the low mantle reservoir are predominantly controlled by primitive He (3He) and U and Th radiogenic decayed He (4He), but the isotopic ratios of the heavier noble gases, such as Ar, Kr and Xe, are controlled to different extent by recycling of subduction components. The difference of the noble isotopic compositions of the two type crusts is the result of the difference of the noble isotopic composition of the mantle source reservoir underneath the seamounts the crusts occurred, the noble gases of the high 3He/4He type crusts are derived mainly from EM-type lower mantle reservoir, and the noble gases in the low 3He/4He type crusts are derived mainly from HIMU-type lower mantle reservoir.