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According lo Ihe investigation data of PHC content in Jiaozhou Bay, China from 1979 to 1983, the content, sources, horizontal, vertical and seasonal distribution, and transfer laws of PHC in the water of the bay were analyzed on spatial scale, and the processes of pollution sources. land transfer, sedimentation, and water transfer of PHC in Jiaozhou Bay were discussed on temporal scale. These laws and changing processes could provide theoretical foundation for studies on water transfer of PHC and other heavy metals. [ABSTRACT FROM AUTHOR]

Based on the investigation data of PHC content in Jiaozhou Bay, China during 1980 -1981, the distribution of PHC content in the bottom water of Jiaozhou Bay was analyzed. The results showed that PHC content in the bottom water of Jiaozhou Bay varied from 0.028 to 0.147 mg/L from April to November (except for May) during 1980 -1981,indicating that the bottom water was polluted slightly by PHC. PHC content was affected by the vertical water body effect, so that the minimum of PHC content in the bottom water changed stably. In addition, there were no obvious seasonal variations in PHC content in the bottom water. It reveals that PHC brought by human activity was more than that transported by rivers, so PHC pollution caused by human activity was serious. From the inside water to the outside water, PHC content decreased gradually in April and August but increased in November, showing the sedimentation process of PHC. The sedimentation process of PHC showed the migration paths of PHC in Jiaozhou Bay in time and space. [ABSTRACT FROM AUTHOR]

Based on investigation data on PHC content in Jiaozhou Bay, China during 1979 -1983, the horizontal distribution and pollution sources of PHC in Jiaozhou Bay were analyzed. The results showed that from 1979 to 1983, PHC in the water body of Jiaozhou Bay was mainly from rivers such as Haibo River, Licun River and Loushan River, and PHC content ranged from 0.10 to 1. 10 mg/L. The pollution sources of PHC were serious during 1979 -1981 and then became slight during 1982 -1983. From 1979 -1981 to 1982 -1983, PHC content, horizontal distribution and degree of pollution sources changed, but the input mode of PHC was constant, that is, PHC was brought into Jiaozhou Bay by rivers. [ABSTRACT FROM AUTHOR]

Based on investigation data on PHC in Jiaozhou Bay, China from 1979 to 1983, the monthly, seasonal and annual variations of PHC content in Jiaozhou Bay were studied. The results showed that from 1979 to 1983, Jiaozhou Bay was polluted by PHC seriously and then slightly in spring and summer, while Jiaozhou Bay was polluted by PHC slightly in autumn. During 1979-1983, PHC content in the water body of Jiaozhou Bay decreased year by year, and it was close to the background value gradually. Moreover, the reduction was obvious in spring and summer but very slight in autumn. Therefore, the water quality of Jiaozhou Bay became better. [ABSTRACT FROM AUTHOR]

• Moss biocrusts buffer net soil exchange of CO 2 in a humid karst ecosystem. • Moss biocrusts increase soil respiration but decrease its temperature sensitivity. • Disturbance reverses the effect of moss biocrusts on soil CO 2 effluxes. • Moss biocrusts increase soil respiration via soil nutrient and enzyme pathways. Biocrusts, specialized communities comprised of mosses, lichens, cyanobacteria, fungi, and bacteria occurring on the ground surface, are famous as ecological engineers on Earth, but less is understood in humid karst areas, where they are often widespread and provide important ecosystem services. To better understand how biocrusts affect soil carbon cycles, we performed an in situ study monitoring net soil exchange (NSE) of CO 2 , soil respiration (R s), soil temperature and moisture, and determined soil nutrient contents and carbon-related enzyme activities over three different microcosms (soils covered by moss biocrusts, soils deprived of biocrust-forming mosses, and bare soils) in a subtropical karst ecosystem in southwest China. The results showed that, in comparison with bare soils, moss biocrusts increased R s by 40% but decreased NSE by 49% and the temperature sensitivity of R s by 35%. However, disturbance to moss biocrusts decreased R s by 26% but increased NSE by 104% and the temperature sensitivity of R s by 93%. Although moss biocrusts increased the content of soil organic carbon and total nitrogen and the activity of β-glucosidase, this effect was reversed by disturbance to moss biocrusts. While R s was significantly correlated with soil temperature and moisture, the effect of moss biocrusts on R s was partly explained by soil organic carbon, total nitrogen, and β-glucosidase. Overall, this study adds to the scarce number of experiments characterizing biocrust ecology in humid karst ecosystems and calls for management efforts to protect and restore biocrusts to buffer soil CO 2 emissions under global change scenarios. [ABSTRACT FROM AUTHOR]