Ecological water demand:the case of the slope systems in the East Liaohe River Basin

The ecological water demand (EWD) is the least water amount required to maintain the structure and the function of the special eco-system and the temporal scale of a study on the EWD must be a season's time. Based on GIS and RS with the source information of hydrological data of 46 hydrological gauges covering 52 years and the digital images of Landsat TM in 1986, 1996 and 2000, the landscape patterns, precipitation and runoff in the East Liaohe River Basin were analyzed. With the result of the above analysis, the spatial and temporal changes of the ecological water demand in the slope systems (EWDSS) of the East Liaohe River Basin (ELRB) were derived. Landscapes in the ELRB are dispersed and strongly disturbed by human actions. The hydrological regime in ELRB has distinct spatial variations. The average annual EWDSS in the ELRB is 504.72 mm (324.08-618.89 mm), and the average EWDSS in the growth season (from May to September) is 88.29% of the year's total EWDSS .The ultimate guaranteeing ratio of the EWDSS in ELRB is 90%. The scarce EWDSS area in the whole year and in the growth season are 60.47% and 74.01% of the entire basin respectively. The trend of scarce EWDSS area is most serious according to the quantity and area of scarce EWDSS regions.

Occurrence and bioaccumulation of polybrominated diphenyl ethers in sediments and paddy ecosystems of Liaohe River Basin, northeast China

Concentrations of 16 polybrominated diphenyl ether（PBDE） congeners were measured in river sediments, paddy soils and three species of paddy-field organisms（crab, loach and carp） collected from the Liaohe River Basin, northeastern China. The total contents of PBDEs（∑_（16）PBDEs） in sediments and paddy soils were in the ranges of 273.4–3246.3 pg/g dry weight（dw）, and 192.1–1783.8 pg/g dw, respectively. BDE 209 was the dominant congener both in sediments and paddy soils. The concentrations of ∑_（16）PBDEs in sediments were significantly higher than those in the adjacent paddy soils, indicating a potential transport of PBDEs from river to paddy ecosystems via river water irrigation. The biota–soil accumulation factor（BSAF） was calculated as the ratio between the lipid-normalized concentration in paddyfield organisms and the total organic carbon-normalized concentration in paddy soil. The average BSAF values of ∑15PBDEs followed the sequence of crab（3.6） 〉 loach（3.3） 〉 carp（2.1）. BDE 154 had the highest BSAF value, and a parabolic trend between BSAF values of individual PBDE congeners and their log KOWvalues was observed. In view of the fact that crab had the larger BSAF value and higher lipid content, the ecological risk and health risk for crab cultivation in paddy fields should be of particular concern.