– Pollutant migration pathways
Given great evaporation and small precipitation, only a small amount of leachate is
produced owning to the high content of inorganic components in waste. Basically,
leachate is not necessarily discharged beyond the landfill, considering poor permeability under simple hydrogeological conditions. Therefore, groundwater in the
area is not easily contaminated by leachate. Where the groundwater is contaminated, pollutants can migrate, transform, and spread through groundwater flows.
– Receptors
During the operation of the landfill, workers inside the landfill may be exposed to
groundwater pollutants, so they are considered as sensitive receptors based on the
landfill use and the surrounding population.
• Exposure pathway analysis
Since the site contamination plume involves drinking water sources, the exposure
pathways include indoor and outdoor inhalation of vapor from groundwater, which
are not applicable to the focus pollutants: ammonia nitrogen and fluoride.
Therefore, there is no pathway of exposure for focus pollutants in the landfill of
Qinghai Province. It is not necessary to evaluate the health risk.
Case 4 Groundwater pollution investigation, source intensity evaluation and risk
assessment of an OCS site in Gansu Province
(1) Overview of the study area
(a) Geographical location
The OCS site is located in Lanzhou City, Gansu Province and about 500 m away
from the Yellow River.
(b) Meteorological conditions
Lanzhou is situated in temperate semi-arid climate zone characterized by dry and
cold climate with long winters and large temperature differences. The average mean
temperature is 9.1 °C and the extreme maximum and minimum temperatures are
39.1 °C and −23.1 °C respectively. The precipitation is different among years and
within the year, with an annual average of 317.6 mm. It is concentrated in July,
August and September, representing 56 to 70% of the annual total. The average
annual evaporation in the urban area is 1433 mm; the average annual sunshine
reaches 2446.4 h; the average annual relative humidity registers 59%; and the
maximum frozen soil depth is 103 cm. The mean annual wind speed is 1.0 m/s, and
the dominant wind direction is SE and SEE (along the river). The maximum wind
speed is 27.6 m/s, predominately in the west direction. The maximum snow
thickness is 10 cm.
186
5 Application Cases
Given great evaporation and small precipitation, only a small amount of leachate is
produced owning to the high content of inorganic components in waste. Basically,
leachate is not necessarily discharged beyond the landfill, considering poor permeability under simple hydrogeological conditions. Therefore, groundwater in the
area is not easily contaminated by leachate. Where the groundwater is contaminated, pollutants can migrate, transform, and spread through groundwater flows.
– Receptors
During the operation of the landfill, workers inside the landfill may be exposed to
groundwater pollutants, so they are considered as sensitive receptors based on the
landfill use and the surrounding population.
• Exposure pathway analysis
Since the site contamination plume involves drinking water sources, the exposure
pathways include indoor and outdoor inhalation of vapor from groundwater, which
are not applicable to the focus pollutants: ammonia nitrogen and fluoride.
Therefore, there is no pathway of exposure for focus pollutants in the landfill of
Qinghai Province. It is not necessary to evaluate the health risk.
Case 4 Groundwater pollution investigation, source intensity evaluation and risk
assessment of an OCS site in Gansu Province
(1) Overview of the study area
(a) Geographical location
The OCS site is located in Lanzhou City, Gansu Province and about 500 m away
from the Yellow River.
(b) Meteorological conditions
Lanzhou is situated in temperate semi-arid climate zone characterized by dry and
cold climate with long winters and large temperature differences. The average mean
temperature is 9.1 °C and the extreme maximum and minimum temperatures are
39.1 °C and −23.1 °C respectively. The precipitation is different among years and
within the year, with an annual average of 317.6 mm. It is concentrated in July,
August and September, representing 56 to 70% of the annual total. The average
annual evaporation in the urban area is 1433 mm; the average annual sunshine
reaches 2446.4 h; the average annual relative humidity registers 59%; and the
maximum frozen soil depth is 103 cm. The mean annual wind speed is 1.0 m/s, and
the dominant wind direction is SE and SEE (along the river). The maximum wind
speed is 27.6 m/s, predominately in the west direction. The maximum snow
thickness is 10 cm.
186
5 Application Cases