Environmental changes reflected by sedimentary geochemistry in recent hundred years of Jiaozhou Bay, North China

Sediment geochemical technique was employed to assess how the sediment records reflect the environmental changes of Jiaozhou Bay, a semi-enclosed bay adjacent to Qingdao, China. In the past hundred years, Jiaozhou Bay has been greatly impacted by human interventions. A dated core sediment by Pb-210 chronology was analyzed for trace metals including Li, Cd, Cr, Pb, Cu, Ni, Co, Zn together with C, N, P and BSi. Based on the research, the development of Jiaozhou Bay environment in the past hundred years can be divided into three stages: (1) before the 1980s characterized by relatively low sedimentation rate, weak heavy metal pollution and scarce eutrophication; (2) from the 1980s to 2000, accelerating in the 1990s, during which high sedimentation rates, polluted by heavy metals and the frequent occurrence of red tide; (3) after 2000, the period of the improvement of environment, the whole system has been meliorated including the heavy metal pollution and hypernutrification. (c) 2006 Elsevier Ltd. All rights reserved.

Organic carbon source and burial during the past one hundred years in Jiaozhou Bay, North China

Organic carbon (OC), total nitrogen (TN), and Pb-210 in core sediment were measured to quantify the burial of organic carbon and the relative importance of allochthonous and autochthonous contributions during the past one hundred years in Jiaozhou Bay, North China. The core sediment was dated using Pb-210 chronology, which is the most promising method for estimation of sedimentation rate on a time scale of 100-150 years. The variation of the burial flux of organic carbon in the past one hundred years can be divided into the following three stages: (1) relatively steady before 1980s; (2) increasing rapidly from the 1980s to a peak in the 1990s, and (3) decreasing from the 1990s to the present. The change is consistent with the amount of solid waste and sewage emptied into the bay. The OC:TN ratio was used to evaluate the source of organic carbon in the Jiaozhou Bay sediment. In the inner bay and bay mouth, the organic carbon was the main contributor from terrestrial sources, whereas only about half of organic carbon was contributed from terrestrial source in the outer bay. In the inner bay, the terrestrial source of organic carbon showed a steady change with an increase in the range of 69%-77% before 1990 to 93% in 2000, and then decreased from 2000 because of the decrease in the terrestrial input. In the bay mouth, the percentage of organic carbon from land reached the highest value with 94% in 1994. In the outer bay, the sediment source maintained steady for the past one hundred years.

Geochemieal records of phosphorus in Jiaozhou Bay sediments - Implications for environmental changes in recent hundred years

Phosphorus is a key element and plays an important role in global biogeochemical cycles. The evolution of sedimentary environment is also influenced by phosphorus concentrations and fractions as well as phosphate sorption characteristics of the marine sediments. The geochemical characteristics of phosphorus and their environmental records were presented in Jiaozhou Bay sediments. Profiles of different forms of phosphorus were measured as well as the roles and vertical distributions of phosphorus forms in response to sedimentary environment changes were investigated. The results showed that inorganic phosphorus ( IP) was the major fraction of total phosphorus ( TP); phosphorus which is bound to calcium, iron and occluded phosphorus, as well as the exchangeable phosphorus were the main forms of IP, especially calcium-phosphorus, including detrital carbonate-bound phosphorus ( Det - P) and authigenic apatite-bound phosphorus ( ACa - P), are the uppermost constituent of IP in Jiaozhou Bay sediments. Moreover, the lead-210 chronology technology was employed to estimate how much phosphorus was buried ultimately in sediments. And the research showed that the impacts of human activities have increased remarkably in recent years especially between the 1980s and 2000. According to research, the development of Jiaozhou Bay environment in the past hundred years can be divided into three stages; (I) before the 1980s characterized by the relatively low sedimentation rate, weak land-derived phosphorus inputs and low anthropogenic impacts; (2) from the 1980s to around 2000, accelerating in the 1990s, during which high sedimentation rates, high phosphorus abundance and burial fluxes due to the severe: human activities impacted on the whole environmental system; (3) after 2000, the period of the improvement of environment, the whole system has been improved including the decreasing sedimentation rates, concentration and the burial fluxes of phosphonas.