风浪扰动对太湖水体重金属形态的影响

EFFECTS OF WINDWAVE DISTURBANCE ON HEAVY METALS SPECIATIONS IN THE WATER OF LAKE TAIHU

对不同风浪条件下水体中的悬浮颗粒物,采用ICP-AES测定其中Co,Cr,Cu,Ni,Pb,Zn,Al,Fe和Mn不同形态的含量.研究表明,水体中Al,Fe,Co,Cr,Pb和Ni可提取态含量随风浪扰动程度的增强其含量均有不同程度的增大.Mn,Zn和Cu在7m·s^(-1)风浪下含量最高,11m·s^(-1)风浪次之,2m·s^(-1)风浪最小.7m·s^(-1)风浪与2m·s^(-1)风浪相比,水体中Mn,Co,Cr,Zn,Cu和Ni的B_1,B_2,B_3态含量增加3-20倍.11m·s^(-1)风浪与7m·s^(-1)风浪相比,Co,Cr和Ni的B1态含量分别增加31.1%-76.8%,Mn,Zn和Cu分别减少22.1%-38.6%;Cr,Zn和Ni的B_2态含量增加12.1%—50.2%,Mn减少65.6%,Co和Cu的含量相当;Co和Ni的B3态含量增加15.4%-10.3%,Cr,Mn,Zn和Cu略微减少.水体中的金属主要以Fe-Mn氧化物结合态存在,且金属的三态比例随风浪的变化不明显.Mn的生物有效性最高,Zn,Cu和Ni次之,毒性较大的Pb和Cr的生物有效性较低.Al,Fe和Pb的Fe-Mn氧化物结合态比例非常高,约有74.56%—100%.Co,Cr和Ni的有机结合态比例较高,且Co和Ni的三态比例比较均一,Cu的B_3态较低.

Surface water was taken from the east shore of the mouth of Meiliang bay, lake Taihu. The lake water was sampled under 2m · s^-1, 7m · s^-1 and 11 m · s^-1, respectively. Suspended solids （SS） were obtained by cen- trifuging 25L surface water. SS were further freeze-dried and BCR three stage sequential extraction procedure, and ICP-AES were applied to determine the concentration of Co, Cr, Cu, Ni, Pb, Zn and Al, Fe and Mn in SS. It was found that the total extractable amounts of the metals increased gradually with wind speed. The total extractable contents of Mn, Zn, Cu in the water were highest at modest wind speed and were lowest at weak wind-wave. Comparing with the weak wind-wave, the B1, B2 and B3 fractions contents of Mn, Co, Cr, Zn, Cu and Ni at the middle wind speed were more 3-20 times. Comparing with the modest wind speed, B1, the contents of Co, Cr and Ni were 31.1%-76. 8% higher, Mn, Zn and Cu were 22. 1%-38.6% less; B2, the contents of Cr, Zn and Ni were 12. 1%-50.2% higher, Mn was 65.6% less, the contents of Co was similar to Cu; B3, the contents of Co and Ni were 15.4%-10.3% higher, the contents of Cr, Mn, Zn and Cu decreased a little. The metals were mainly existed in Fe-Mn oxide form in lake water, and independence to wind speed. The bio-availability of Mn was highest, and Zn, Cu and Ni were also very high. However, the bio-availability of Pb and Cr were low. Al, Fe and Pb were mainly existed in Fe-Mn oxide form, which were occupied 74.56%-100% of the total in water. Co, Cr and Ni mainly existed in organic/sulphide form. The organic/sulphide fractions of Cu was the lowest.