The food sources and trophic levels of four species of fish (Hexagrammos otakii, Pholos fangi, Sebastes schlegelii, Zoarces elongates) and six species of invertebrates (Octopus variabilis, Rapana venosa, Oratosquilla oratoria, Alpheus japonicus, Alpheus distinguendus, Charybdis japonica) prior to and following the formation of spatial heterogeneity of artificial reefs (ARs) were studied using stable isotopes. The trophic levels of fishes were significantly higher than those of invertebrates (P < 0.01). The trend of all 10 species occupies a higher trophic levels in March, and showed lower trophic levels in November. Following the formation of spatial heterogeneity, the trophic levels of fishes decreased significantly and did not increase until next year. One year following the formation, the food sources of Z. elongatus were significantly different from the other three kinds of fish. And its trophic level was significantly higher than the other three kinds of fish and also significantly higher than itself prior to the formation. This means Z. elongatus has already adapted to the ARs, where they can maintain high trophic levels. Within two years following the formation, the trophic levels of 10 species marine animals gradually reached a new steady state. This study revealed the effects of the spatial heterogeneity of artificial reefs on marine animals from the perspective of ecosystem structure.
Geogas surveys have been carried out in China for more than 15 years. Although much valuable experience has been obtained from these studies, little progress (until recently) has been made in understanding the mechanisms involved and in testing procedures. One of the major challenges is to design a collector for the metals in Geogas effectively, using the right medium for complete sorption, without knowing their actual forms. Several absorbers have been tested in China. Almost all solid collectors used in Geogas testing contain variable quantities of metals which are difficult to remove chemically or physically. Thus some of the published data related to Geogas surveys should be re-evaluated. Newly developed liquid collectors, used since 1999, improve the accuracy of the Geogas data because they are low in blank levels, and their use negates the need for time-consuming digestion, the aqueous medium being easily analysed by inductively coupled plasma -mass spectrometry. With this refinement in collectors, the recent Geogas anomalies obtained in soils over buried mineralization attest to the presence of metals within soil gas and confirm the validity of this technique.
Studying and understanding the complexity and interactions of different factors influencing stream sediment quality is necessary for the development of successful water quality management strategies. This study aims to evaluate the level of contamination by potentially toxic elements (PTEs) (As, Co, Cr, Cu, Mn, Ni, Pb, V, Zn) of the stream sediments of the Nile River. During the spring of 2019, river sediments were sampled at 23 sites along the Nile River. For each sample, one aliquot was digested in aqua regia and analyzed by ICP-MS for pseudo-total concentration, while for another aliquot, sequential extraction procedures were applied to determine chemical speciation. Compositional data analysis (CoDa) and k-means were applied to recognize the contribution of natural and anthropogenic sources, while pollution indices (EF, RAC) and sediment quality guidelines (SQGs) were applied to assess the ecological risk to biotic species. The results reveal that elements such as Cr, Mn, V and Fe, found in high concentrations in almost all samples (Cr up to 739 mg/kg, Mn up to 1942 mg/kg, V up to 507 mg/kg, Fe up to 98,519 mg/kg), have a natural origin, while the concentrations of Cu (up to 69 mg/kg), Ni (up to 88 mg/kg), Co (up to 42 mg/kg) and As (up to 9.8 mg/kg) are linked to both natural and anthropogenic processes. Sequential extraction shows that Mn, Co, Ni and, in some sites, Cu and Zn, are the most bioavailable elements. These elements present a high risk of toxicity, while the remaining elements imply a low-to-moderate risk.
The ‘Metals in Soil Gas’ (MSG) survey has proven to be a useful tool for mineral exploration under exotic overburden. Tracing the source of these metals with Pb isotopes is helpful to understand the formation of MSG. Lead isotope ratios in MSG samples were determined by ICP-MS (Model HP4500); the Pb isotope ratios in loess, red soil, wall rocks and ores were measured following decomposition and separation using a VG-354 thermal ionization mass spectrometer (TIMS) for comparison. The results of the study of samples collected over the Jiaolongzhang base metal deposit show that the Pb isotope ratios of MSG background samples are markedly distinct from those ratios of any medium (loess, red soil layer, wall-rocks and ores) in the vicinity of the deposit. The Pb isotope ratios in the MSG anomalous samples ( 206 Pb/ 204 Pb = 18.34–18.56, 207 Pb/ 204 Pb = 15.622–15.809 and 208 Pb/ 204 Pb = 38.184–38.691) are totally different from those in the samples of background areas ( 206 Pb/ 204 Pb = 16.46–17.68, 207 Pb/ 204 Pb = 13.985–14.945 and 208 Pb/ 204 Pb = 34.199–36.884). The Pb isotope ratios of MSG anomalous samples scatter near the ratios of the mineralized wall-rocks ( 206 Pb/ 204 Pb = 18.554–18.874, 207 Pb/ 204 Pb = 15.618–15.755 and 208 Pb/ 204 Pb = 38.629–39.126) and sulphides ( 206 Pb/ 204 Pb = 18.130–18.251, 207 Pb/ 204 Pb = 15.671–15.767 and 208 Pb/ 204 Pb = 38.350–38.582). It can be concluded that some of the Pb in MSG anomalous samples originates from deep sulphide mineralization and Pb isotope ratios of MSG anomalous samples indicate that an MSG survey can detect the deeply concealed mineral deposits under exotic cover.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)