[Waterborne iron migration by groundwater irrigation pumping in a typical irrigation district of Sanjiang Plain].

The iron concentration in groundwater, iron's seasonal migration from groundwater to sun-basked pools, paddy fields and drainage canals, and its distribution in the sediments/soils were observed in the Jiansanjiang Branch Bureau, Heilongjiang Agricultural Cultivation Bureau. The results suggested that the total iron mass concentration of the studied area was (1.73 +/- 0.41) mg x L(-1), ranging from 0.01 to 11.4 mg x L(-1), with the variation coefficient of 1.29%. The annual iron input mass from groundwater to paddy fields and other surface water bodies was 4 976.40 t in 2010, according to the rice planting area and rating irrigation volume. Dissolved Fe2+, Fe3+ and iron, as well as the total iron (dissolved and particle) had seasonal variation, with greater values presented in June and July. These waterborne irons in paddy field waters were greater than those in sun-basked pools and drainage canals. Obvious enrichment effect was observed in sun-basked pools and paddy fields, with their total iron mass concentrations were 6.17 and 21.65 times greater than that in groundwater. Either the total iron or iron oxides in sun-baked pool sediments were greater than that in paddy field soils, field canal and main canal sediments. The differences of the total iron and iron oxides in paddy field soils, field canal and main canal sediments were not significantly different. Considerable irons were precipitated within sun-basked pools and paddy fields during the transfer from groundwater to surface water, with a part of irons exporting into canals through drainage and then precipitated there. Not only the change of total iron mass, but the transformation of iron chemical speciation was observed during the transfer, which was affected by paddy irrigation management directly. The long-term irrigation pumping could cause the substantial enrichment of iron in paddy soils and canal sediments, resulting in the increase of potential pollution risk.

[Dynamic change of dissolved iron in wetland soil solutions responding to freeze-thaw cycles].

The effects of five freeze-thaw cycles on the dynamic change of dissolved iron in three typical wetland soils (humus marsh soil in Carex lasiocarpa community, meadow marsh soil in Cares meyeriarna community, and meadow albic soil in Calamagrostis angustifolia community)of Sanjiang Plain, Northeast China, was analyzed through in-situ soil column simulation. One freeze-thaw cycle was conducted as freezing at -10 degrees C for 1 d and then thawing at 5 degrees C for 7 d. The thermostatically incubated soils at 5 degrees C were controls. The results showed that most pH and Eh values increased after the first freeze-thaw cycle, and then decreased after the subsequent cycles. 84.4% of the pH values of freeze-thaw treated soils were smaller than that of control, while 82.2% of the Eh values of freeze-thaw treated soils were greater than that of control. Most of the dissolved iron in all soil solutions were Fe3+ ions and colloids, and the reduction of these Fe3+ species were inhibited. The concentrations of Fe2, Fe3+, and total dissolved iron (TFe) of the freeze-thaw treated soils were all smaller than that of controls, with the means of (0.62 +/- 0.08) mg x L(-1) and (1.25 +/- 0.16) mg x L(-1), respectively. The variation trends of pH, Eh, and dissolved iron in the humus marsh soil were significantly different from that in the meadow albic soil. The trends in the meadow marsh soil, as the transitional soil type, were more similar to the meadow albic soil for pH, while more similar to the humus marsh soil for Eh and dissolved iron. Among the three soils, the difference between freeze-thaw treated columns and controls of the second layer were all smaller than that of the third and fourth layer, which indicated that the effect of freeze-thaw cycles were more significant for the upper annular wetland soil layers than the lower layers.

[Spatiotemporal distribution characteristics of soil iron in the annular wetland under different water regime].

The effect of water regime on the spatial distribution of total iron and the seasonal variation of dissolved iron in a typical annular wetland of Sanjiang Plain, Northeast China, was analyzed through in situ sampling of soils and soil solutions. The results showed that the average level of total iron of the wetland soil (0-60 cm) was (2.54 +/- 0.73) x 10(4) mg x kg(-1), which decreased gradually from the Calamagrostis angustifolia community in the edge of the annular wetland [(2.91 +/- 0.51) x 10(4) mg x kg(-1)], to the C. meyeriana community [(2.60 +/- 0.35) x 10(4) mg x kg(-1)], the C. lasiocarpa community [(2.48 +/- 0.31) x 10(4) mg x kg(-1)], and the of C. pseudocuraica community [(2.17 +/- 0.31) x 10(4) mg x kg(-1)] in the centre of the annular wetland. The iron solubility of perennial flooding soil was higher than seasonal flooding soil. The gross dissolved iron increased from soil thawing in the late spring [(0.35 +/- 0.086) mg x L(-1)] to freezing in the late autumn [(12.67 +/- 2.92) mg x L(-1)], because the soil iron was activated by continuous submergence. The reduced degree as shown by Fe3+/Fe2+ increased with the increment of water depth or flooding duration. Significant and extremely significant correlations were observed between dissolved Fe3+ or Fe2+ and pH, TOC, TN and PO4(3-), which suggested that the distribution of iron was influenced by the soil physical and chemical properties, and coupled with the transfer and transformation of C, N, and P elements.

[Heavy metal contents in insects collected from the Huludao City suffering pollution by zinc smelting and cholor-alkai production].

14 insect species, which were classified to three groups: the herbivorous, the polyphagous and the carnivorous, and earthworms were collected from the grasslands in Huludao City, Liaoning Province, China. Mercury, cadmium and lead contents in biota were determined to discuss the heavy metal pollution in organisms. Mercury, cadmium and lead contents were 0.168, 9.19 and 12.58 mg x kg(-1) in the herbivorous insects, respectively; 0.375, 24.43 and 17.71 mg x kg(-1) in the polyphagous insects, respectively; 0.928, 29.78 and 18.39 mg x kg(-1) in the carnivorous insects, respectively. It showed that heavy metal pollution in biota in Huludao City was heavy. Bioaccumulation abilities to heavy metals significantly differed with insect species. Snails and dragonflies could accumulate more mercury than the other insects and spiders could accumulate the most cadmium and lead in all insect species. These three metals investigated in insects were all sorted as the herbivorous < the polyphagous < the carnivorous. Cadmium and lead contents between the polyphagous and the carnivorous varied slightly. Correlation analysis showed that cadmium and lead contents were significantly related, but mercury and cadmium or mercury and lead were not. It indicated that cadmium and lead in insects were from the same pollution sources while mercury was more complex.

[Distribution of sediment iron of the ditch system in Sanjiang Plain, northeast China].

The iron distribution of the multi-level ditch system (hair canal-field canal-lateral canal-branch canal-main canal) was studied through total iron determination of the sediments (0-60 cm). The results showed that the mean concentration was (3.02 +/- 0.10) x 10(4) mg x kg(-1). Extremely significant difference was obseved between different ditch level (F = 6.261, p << 0.001), and the highest and the lowest concentration were present in the farmland lateral canal (3.71 x 10(4) mg x kg(-1)) and wetland canal (2.43 x 10(4) mg x kg(-1)), respectively. The difference of different sediment layers was not significant (F = 0.093, p = 0.693), while the iron concentrations of 0-10 cm and 10-20 cm sediments were 51.96% and 62.22% higher than that of the natural wetland soil nearby, respectively. Iron can transfer with the runoff in a certain extent, but it was not cumulated along the ditch system with the largest cumulation location at the third level. The runoff containing iron decreased gradully because of the wetland protection and climate change nowadays. The horizontal transfer of iron along the ditch system indicated the timing and intensity of iron loss in the past since the canals were dredged.

Mercury, cadmium and lead biogeochemistry in the soil-plant-insect system in Huludao City.

Mercury, cadmium, and lead concentrations of ashed plants and insects samples were investigated and compared with those of soil to reveal their biogeochemical processes along food chains in Huludao City, Liaoning Province, China. Concentration factors of each fragments of the soil-plant-the herbivorous insect-the carnivorous insect food chain were 0.18, 6.57, and 7.88 for mercury; 6.82, 2.01, and 0.48 for cadmium; 1.47, 2.24, and 0.57 for lead, respectively. On the whole, mercury was the most largely biomagnified, but cadmium and lead were not greatly accumulated in the carnivorous insects as expected when the food chain extended to the secondary consumers. Results indicated that concentration factors depended on metals and insects species of food chains.

[Characteristics of the wetland soil iron under different ages of reclamation].

The temporal-spatial trends of soil total iron concentration (Fet), free degree (Fed/Fet), activation degree (Feo/Fed) and complex degree (Fep/Fed) of soil iron oxides after reclamation were studied in Sanjiang Plain Wetlands. The result suggests that Fet in the upper tillage layers (0 - 20 cm) are influenced by reclamation more significantly than that in the lower ones (20 - 100 cm), and so does the early ages (0 - 1 years) than the late ages (1 - 25 years). Fet is negatively correlated with organic matter extremely significantly (R = - 0.62), while that with total phosphorus and pH are not significant. Fet of soil layer I (0 - 10 cm) increases obviously during the first 7 years after reclamation, and tends to become stable after 13 years, while those ages of soil layer II (10 - 20 cm) are 8 years and 15 years respectively. Soil layer I shows shorter responding time and better regularity than layer II. Fed/Fet increases rapidly after reclamation, decreases later and then increases again. Feo/Fed indicates exponential decrease with the reclamation ages as well as Fep/Fed. Feo/Fed of layer I decreases radically during the first 4 years after reclamation and tends to become stable after 13 years, while that of layer II decreases dramatically within the first year and keeps stable henceforth. The counterparts of Fep/Fed are 6 years, 14 years, and 2 years respectively. With the fitted experimental equations of Fet, Feo/Fed, and Fep/Fed, the ages of reclamation can be deduced reversely, which indicates the implication of iron on the shifts of soil environment.